diff --git a/.stylua.toml b/.stylua.toml
new file mode 100644
index 0000000..902182b
--- /dev/null
+++ b/.stylua.toml
@@ -0,0 +1,8 @@
+column_width = 120
+line_endings = "Unix"
+indent_type = "Spaces"
+indent_width = 4
+quote_style = "AutoPreferDouble"
+call_parentheses = "Always"
+# never allow `if x then y end` on one line — always expand after then/do
+collapse_simple_statement = "Never"
diff --git a/README.md b/README.md
index 71c2b89..ec38e93 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # `a`
 
-`a` embeds a Lua interpreter and adds a standard library and IO access, so a script can reach the network, a database, the filesystem, and the terminal without additional setup.
+`a` embeds a Lua interpreter and adds a standard library and IO access, so a script can reach the outside world — today an HTTP client and SQLite, with more of the surface below planned — without additional setup.
 
 ```sh
 a file.lua   # run a script
@@ -38,10 +38,14 @@ The result is a single binary that runs a `.lua` file. There is no package manag
 
 ## The standard library
 
-The standard library is the main purpose of `a`. Planned surface:
+The standard library is the main purpose of `a`. Available today:
 
-- **Networking** — HTTP client, WebSocket, and MQTT (3.1.1 and 5).
+- **Networking** — HTTP client (WebSocket and MQTT are planned).
 - **SQLite** — access to embedded SQLite databases.
+- **Core helpers** — `math`, `table`, and `utils` extensions, structured `log`, `os` time helpers, and `task.join` concurrency.
+
+Planned:
+
 - **Filesystem** — read/write/glob/walk without stock Lua's `io` boilerplate.
 - **Terminal UI** — interactive line editing and full-screen TUI, comparable to `ncurses`.
 
@@ -52,7 +56,7 @@ The intent is for the common case to be a single call rather than a multi-step s
 - Embeds Lua 5.5 via `mlua`, on an async core ([`tokio`](https://tokio.rs/)) so IO-heavy scripts don't block.
 - A single self-contained binary. No LuaRocks, no make, no virtualenv.
 - Scripts run in a **sandboxed** environment modeled on [Luau's safe environment](https://luau.org/sandbox): `io`, `package`, and `debug` are not loaded; `os` is trimmed to its time functions; the bytecode/chunk-loading escape hatches (`load`, `loadfile`, `dofile`, `string.dump`) are removed. The library `a` provides is the supported way to reach the outside world.
-- A leading `#!` shebang line is skipped, so scripts can be made executable directly.
+- A leading `#!` shebang line is skipped (after an optional UTF-8 BOM), so scripts can be made executable directly. Script files need not be valid UTF-8 — Lua source is byte-oriented.
 
 ## Building
 
diff --git a/docs/utils.md b/docs/utils.md
index 3179f1c..ee86c7f 100644
--- a/docs/utils.md
+++ b/docs/utils.md
@@ -10,7 +10,7 @@ local data = utils.fromJSON('{"name":"Alice","age":30}')
 print(data.name, data.age)            --> Alice   30
 
 print(utils.toJSON({1, 2, 3}))        --> [1,2,3]
-print(utils.dump({a = 1, b = {2, 3}})) --> { a = 1, b = { 2, 3 } }
+print(utils.dump({a = 1, b = {2, 3}})) --> {a=1, b={2, 3}}
 ```
 
 ## JSON
diff --git a/lua/coroutines-demo.lua b/lua/coroutines-demo.lua
index c578c23..6203303 100644
--- a/lua/coroutines-demo.lua
+++ b/lua/coroutines-demo.lua
@@ -3,7 +3,9 @@
 --
 -- Run with:  cargo run -- lua/coroutines-demo.lua
 
-local function banner(s) print("\n=== " .. s .. " ===") end
+local function banner(s)
+    print("\n=== " .. s .. " ===")
+end
 
 ----------------------------------------------------------------------
 banner("1. Pure Lua coroutines (no async involved)")
@@ -11,19 +13,19 @@ banner("1. Pure Lua coroutines (no async involved)")
 -- Plain cooperative coroutines work exactly as in stock Lua: this is pure VM
 -- machinery and never touches tokio.
 local function counter(n)
-  for i = 1, n do
-    coroutine.yield(i * i)
-  end
-  return "done"
+    for i = 1, n do
+        coroutine.yield(i * i)
+    end
+    return "done"
 end
 
 local co = coroutine.wrap(counter)
 print("squares:", co(3), co(3), co(3)) -- 1  4  9
 
 local raw = coroutine.create(counter)
-print("status fresh:", coroutine.status(raw))      -- suspended
+print("status fresh:", coroutine.status(raw)) -- suspended
 coroutine.resume(raw, 1)
-coroutine.resume(raw, 1)                            -- runs to `return`
+coroutine.resume(raw, 1) -- runs to `return`
 print("status after return:", coroutine.status(raw)) -- dead
 
 ----------------------------------------------------------------------
@@ -43,14 +45,15 @@ banner("3. GOTCHA: async os.sleep inside a *manually resumed* coroutine")
 -- coroutine.resume / coroutine.wrap does NOT. So driving an async call yourself
 -- does not actually wait -- the sleep is not performed by your resume loop.
 local sleeper = coroutine.wrap(function()
-  os.sleep(0.50)
-  return "awoke"
+    os.sleep(0.50)
+    return "awoke"
 end)
 
 local t1 = os.microtime()
-local first = sleeper()                 -- returns immediately with the sentinel
-print(string.format("first resume returned %s after only %.3fs (did NOT wait 0.5s)",
-  tostring(first), os.microtime() - t1))
+local first = sleeper() -- returns immediately with the sentinel
+print(
+    string.format("first resume returned %s after only %.3fs (did NOT wait 0.5s)", tostring(first), os.microtime() - t1)
+)
 print("--> lesson: don't hand-drive coroutines that call async stdlib functions.")
 
 ----------------------------------------------------------------------
@@ -60,40 +63,43 @@ banner("4. Real concurrency: task.join drives coroutines on tokio")
 -- interleave them. Three tasks that each sleep concurrently finish in ~the
 -- longest single sleep, not the sum -- proof the sleeps overlap on one thread.
 local function worker(name, secs)
-  return function()
-    print(string.format("  [%s] start", name))
-    os.sleep(secs)
-    print(string.format("  [%s] woke after %.2fs", name, secs))
-    return name .. ":" .. secs
-  end
+    return function()
+        print(string.format("  [%s] start", name))
+        os.sleep(secs)
+        print(string.format("  [%s] woke after %.2fs", name, secs))
+        return name .. ":" .. secs
+    end
 end
 
 local t2 = os.microtime()
-local a, b, c = task.join(
-  worker("slow", 0.30),
-  worker("med",  0.20),
-  worker("fast", 0.10)
-)
+local a, b, c = task.join(worker("slow", 0.30), worker("med", 0.20), worker("fast", 0.10))
 local elapsed = os.microtime() - t2
 print(string.format("results: %s, %s, %s", a, b, c))
 print(string.format("wall time: %.3fs", elapsed))
-print(string.format("sequential would have been ~0.60s; concurrent ~0.30s => %s",
-  elapsed < 0.45 and "CONCURRENT (overlapped on tokio)" or "serialized?!"))
+print(
+    string.format(
+        "sequential would have been ~0.60s; concurrent ~0.30s => %s",
+        elapsed < 0.45 and "CONCURRENT (overlapped on tokio)" or "serialized?!"
+    )
+)
 
 ----------------------------------------------------------------------
 banner("5. Nested + return values")
 ----------------------------------------------------------------------
 -- task.join itself yields, so it composes: a joined task can join again.
-local outer = task.join(
-  function()
-    local x, y = task.join(
-      function() os.sleep(0.05); return 21 end,
-      function() os.sleep(0.05); return 21 end
-    )
+local outer = task.join(function()
+    local x, y = task.join(function()
+        os.sleep(0.05)
+        return 21
+    end, function()
+        os.sleep(0.05)
+        return 21
+    end)
     return x + y
-  end,
-  function() os.sleep(0.10); return "sibling" end
-)
+end, function()
+    os.sleep(0.10)
+    return "sibling"
+end)
 print("nested join result:", outer) -- 42
 
 print("\nAll demos finished.")
diff --git a/lua/stdlib/http.lua b/lua/stdlib/http.lua
index 5c4e4f8..e131744 100644
--- a/lua/stdlib/http.lua
+++ b/lua/stdlib/http.lua
@@ -5,7 +5,9 @@
 
 -- Attach resp.json() to a response table: parses resp.body via utils.fromJSON.
 local function wrap_resp(resp)
-    resp.json = function() return utils.fromJSON(resp.body) end
+    resp.json = function()
+        return utils.fromJSON(resp.body)
+    end
     return resp
 end
 
@@ -17,7 +19,9 @@ end
 
 -- Method shorthands for the stateless module.
 for _, m in ipairs({ "get", "post", "put", "patch", "delete", "head" }) do
-    http[m] = function(url, opts) return http.request(m:upper(), url, opts) end
+    http[m] = function(url, opts)
+        return http.request(m:upper(), url, opts)
+    end
 end
 
 function http.getJSON(url, opts)
@@ -41,12 +45,24 @@ function session_mt:request(method, url, opts)
     return wrap_resp(self:_request(method, url, opts))
 end
 
-function session_mt:get(url, opts)    return self:request("GET",    url, opts) end
-function session_mt:post(url, opts)   return self:request("POST",   url, opts) end
-function session_mt:put(url, opts)    return self:request("PUT",    url, opts) end
-function session_mt:patch(url, opts)  return self:request("PATCH",  url, opts) end
-function session_mt:delete(url, opts) return self:request("DELETE", url, opts) end
-function session_mt:head(url, opts)   return self:request("HEAD",   url, opts) end
+function session_mt:get(url, opts)
+    return self:request("GET", url, opts)
+end
+function session_mt:post(url, opts)
+    return self:request("POST", url, opts)
+end
+function session_mt:put(url, opts)
+    return self:request("PUT", url, opts)
+end
+function session_mt:patch(url, opts)
+    return self:request("PATCH", url, opts)
+end
+function session_mt:delete(url, opts)
+    return self:request("DELETE", url, opts)
+end
+function session_mt:head(url, opts)
+    return self:request("HEAD", url, opts)
+end
 
 function session_mt:getJSON(url, opts)
     local resp = self:get(url, opts)
diff --git a/lua/stdlib/math.lua b/lua/stdlib/math.lua
index 996097c..4e96241 100644
--- a/lua/stdlib/math.lua
+++ b/lua/stdlib/math.lua
@@ -11,8 +11,16 @@ local function roundHalfAwayFromZero(x)
     return i
 end
 
---- Round a number to the nearest integer, or to N decimal places.
---- Rounds half away from zero. round(value, 0) returns an integer; round(value, places > 0) returns a float.
+--- @brief Round a number to the nearest integer, or to N decimal places.
+---
+--- round(value) and round(value, 0) return an integer; round(value, places > 0) returns a float.
+--- Rounds half away from zero. Errors on non-numbers, NaN and infinity, on negative or
+--- non-integer places, and (in the integer form) on results outside the Lua integer range.
+--- If value * 10^places overflows, rounding cannot change the value and it is returned unchanged.
+---
+--- @param value number: Value to round
+--- @param places number|nil: Optional number of decimal places, default 0 (must be a non-negative integer)
+--- @return number: The rounded value
 function math.round(value, places)
     if type(value) ~= "number" then
         error("round() called with a non-number value")
@@ -34,7 +42,7 @@ function math.round(value, places)
         if places == 0 then
             return value
         end
-        return value + 0.0
+        return value + 0.0 -- an integer has no decimals to round, but the contract says float
     end
 
     if not math.isFinite(value) then
@@ -52,64 +60,113 @@ function math.round(value, places)
     local mul = 10.0 ^ places
     local scaled = value * mul
     if not math.isFinite(scaled) then
+        -- rounding cannot change a value of this magnitude
         return value
     end
     return roundHalfAwayFromZero(scaled) / mul
 end
 
---- Clamp a number to an interval [min, max]. Either bound may be nil (half-open).
+--- @brief Clamp number to an interval, optionally half-open.
+--- If both bounds are nil, just returns the value.
+--- Errors if any of the params is in wrong type (value must be number, min and max must be number or nil),
+--- or if min is greater than max.
+--- @param value number: Value to clamp
+--- @param min number|nil: Lower bound, or nil for no lower bound
+--- @param max number|nil: Upper bound, or nil for no upper bound
+--- @return number: Value clamped to the interval
 function math.clamp(value, min, max)
     if type(value) ~= "number" then
         error("Non-number passed to clamp() as value")
     end
+
     if min ~= nil and type(min) ~= "number" then
         error("Non-number passed to clamp() as minimum")
     end
+
     if max ~= nil and type(max) ~= "number" then
         error("Non-number passed to clamp() as maximum")
     end
+
     if min ~= nil and max ~= nil and min > max then
         error("clamp() minimum is greater than maximum")
     end
-    if min ~= nil and value < min then return min end
-    if max ~= nil and value > max then return max end
+
+    if min ~= nil and value < min then
+        return min
+    end
+
+    if max ~= nil and value > max then
+        return max
+    end
+
     return value
 end
 
---- Return true if value is a finite number (not NaN or infinity).
+--- @brief Check if a value is a finite number (not NaN or infinity)
+--- @param value any: Value to check
+--- @return boolean: True if the value is a finite number; false for NaN, infinity and non-number values
 function math.isFinite(value)
-    if type(value) ~= "number" then return false end
+    if type(value) ~= "number" then
+        return false
+    end
+    -- NaN is the only value not equal to itself
+    -- math.huge represents infinity
     return value == value and value ~= math.huge and value ~= -math.huge
 end
 
---- Return the sign of a number: -1, 0, or 1. NaN yields 0.
+--- @brief Get the sign of a number: -1 for negative, 0 for zero, 1 for positive.
+--- Note: NaN has no sign and yields 0.
+--- @param value number: Value to take the sign of
+--- @return number: -1, 0 or 1
 function math.sign(value)
     if type(value) ~= "number" then
         error("Non-number passed to sign()")
     end
-    if value > 0 then return 1
-    elseif value < 0 then return -1
-    else return 0
+    if value > 0 then
+        return 1
+    elseif value < 0 then
+        return -1
+    else
+        return 0
     end
 end
 
---- Scale a value linearly from [inMin, inMax] to [outMin, outMax].
---- If clamp is true, the result is clamped to the output range.
+--- @brief Scale a value from one range to another (linear interpolation).
+--- @param value number: The input value to scale
+--- @param inMin number: The minimum of the input range
+--- @param inMax number: The maximum of the input range
+--- @param outMin number: The minimum of the output range
+--- @param outMax number: The maximum of the output range
+--- @param clamp boolean: If true, clamp the result to [outMin, outMax]. Default is false.
+--- @return number: The scaled value
 function math.scale(value, inMin, inMax, outMin, outMax, clamp)
-    if type(value) ~= "number" then error("Non-number passed to scale() as value") end
-    if type(inMin) ~= "number" or type(inMax) ~= "number" then error("Non-number passed to scale() as input range") end
-    if type(outMin) ~= "number" or type(outMax) ~= "number" then error("Non-number passed to scale() as output range") end
-    if inMin == inMax then error("Input range cannot be zero (inMin == inMax)") end
+    if type(value) ~= "number" then
+        error("Non-number passed to scale() as value")
+    end
+    if type(inMin) ~= "number" or type(inMax) ~= "number" then
+        error("Non-number passed to scale() as input range")
+    end
+    if type(outMin) ~= "number" or type(outMax) ~= "number" then
+        error("Non-number passed to scale() as output range")
+    end
+    if inMin == inMax then
+        error("Input range cannot be zero (inMin == inMax)")
+    end
 
     local ratio = (value - inMin) / (inMax - inMin)
     local result = outMin + ratio * (outMax - outMin)
 
     if clamp then
         local lo, hi = outMin, outMax
-        if lo > hi then lo, hi = hi, lo end
-        if result < lo then return lo
-        elseif result > hi then return hi
+        if lo > hi then
+            lo, hi = hi, lo
+        end
+        if result < lo then
+            return lo
+        elseif result > hi then
+            return hi
         end
     end
+
     return result
 end
diff --git a/lua/stdlib/sqlite.lua b/lua/stdlib/sqlite.lua
index dfc8f82..2949f5c 100644
--- a/lua/stdlib/sqlite.lua
+++ b/lua/stdlib/sqlite.lua
@@ -23,18 +23,21 @@ return function(Connection)
     end
 
     --- Run `fn` inside a transaction: commit on success, roll back and re-raise
-    --- on error. The original error is re-raised unchanged (level 0).
+    --- on error. The original error is re-raised unchanged (level 0), and fn's
+    --- return values are passed through on success.
     function Connection:transaction(fn)
         if type(fn) ~= "function" then
             error("sqlite: transaction requires a function argument (got " .. type(fn) .. ")", 2)
         end
         self:begin()
-        local ok, err = pcall(fn)
-        if ok then
+        local results = table.pack(pcall(fn))
+        if results[1] then
             self:commit()
-        else
-            self:rollback()
-            error(err, 0)
+            return table.unpack(results, 2, results.n)
         end
+        -- On failure, roll back but never let a rollback error mask the original
+        -- one (the connection may already be closed, or no transaction active).
+        pcall(self.rollback, self)
+        error(results[2], 0)
     end
 end
diff --git a/lua/stdlib/table.lua b/lua/stdlib/table.lua
index 94b50e5..64d1a2a 100644
--- a/lua/stdlib/table.lua
+++ b/lua/stdlib/table.lua
@@ -1,5 +1,16 @@
---- Make a read-only proxy of a table. Reads pass through; writes raise an error.
---- Caveat: pairs(), next() and # see no contents (proxy is empty). Intended for API namespaces.
+--- @brief Make a read-only view of a table.
+---
+--- Returns a proxy table: reads pass through to the original table, writes raise an error.
+--- The original table is not modified and stays writable - changes to it show through the proxy.
+--- The proxy's metatable is protected (getmetatable returns false).
+---
+--- Caveat: the proxy itself is empty - pairs(), next() and the # operator see no contents,
+--- and the table.* helpers built on them (keys, values, contains, isEmpty, ...) treat it
+--- as empty. Intended for protecting API namespace tables, not for data tables.
+---
+--- @param tbl table: Table to protect
+--- @param name string: Optional name of the table, used in error messages
+--- @return table: Read-only proxy of the table
 function table.readonly(tbl, name)
     if type(tbl) ~= "table" then
         error("table.readonly: argument is not a table (got " .. type(tbl) .. ")")
@@ -7,73 +18,132 @@ function table.readonly(tbl, name)
     if name ~= nil and type(name) ~= "string" then
         error("table.readonly: name is not a string (got " .. type(name) .. ")")
     end
+
     local message = "Attempt to update a read-only table"
-    if name ~= nil then message = message .. " " .. name end
+    if name ~= nil then
+        message = message .. " " .. name
+    end
+
     return setmetatable({}, {
         __index = tbl,
-        __newindex = function() error(message, 2) end,
+        __newindex = function()
+            -- level 2 blames the assignment in the caller's code
+            error(message, 2)
+        end,
         __metatable = false,
     })
 end
 
---- Filter a table by predicate, preserving keys. May leave gaps in a sequence table.
+--- @brief: Filters a table based on a predicate, all values in the table are run through this predicate; the ones that apply stay.
+--- Keys are preserved - filtering a numbered table may leave gaps, use table.ifilter for those.
+--- @param tbl table: Table to filter
+--- @param predicate function: The predicate/filtering function, e.g. function(v) return v <= 5 end - this keeps only values up to 5
+--- @return table: Product of the operation (new table)
 function table.filter(tbl, predicate)
-    if type(tbl) ~= "table" then error("table.filter: table argument is not a table (got " .. type(tbl) .. ")") end
-    if type(predicate) ~= "function" then error("table.filter: predicate is not a function (got " .. type(predicate) .. ")") end
+    if type(tbl) ~= "table" then
+        error("table.filter: table argument is not a table (got " .. type(tbl) .. ")")
+    end
+    if type(predicate) ~= "function" then
+        error("table.filter: predicate is not a function (got " .. type(predicate) .. ")")
+    end
     local result = {}
     for k, v in pairs(tbl) do
-        if predicate(v) then result[k] = v end
+        if predicate(v) then
+            result[k] = v
+        end
     end
     return result
 end
 
---- Filter a sequence table by predicate, producing a new gapless sequence.
+--- @brief: Filters a numbered table based on a predicate, all values in the table are run through this predicate; the ones that apply stay. Produces a new numbered table without gaps.
+--- @param tbl table: Numbered table to filter
+--- @param predicate function: The predicate/filtering function, e.g. function(v) return v <= 5 end - this keeps only values up to 5
+--- @return table: Product of the operation (new table)
 function table.ifilter(tbl, predicate)
-    if type(tbl) ~= "table" then error("table.ifilter: argument is not a table (got " .. type(tbl) .. ")") end
-    if type(predicate) ~= "function" then error("table.ifilter: predicate is not a function (got " .. type(predicate) .. ")") end
+    if type(tbl) ~= "table" then
+        error("table.ifilter: table argument is not a table (got " .. type(tbl) .. ")")
+    end
+    if type(predicate) ~= "function" then
+        error("table.ifilter: predicate is not a function (got " .. type(predicate) .. ")")
+    end
     local result = {}
     for i = 1, #tbl do
         local v = tbl[i]
-        if predicate(v) then result[#result + 1] = v end
+        if predicate(v) then
+            result[#result + 1] = v
+        end
     end
     return result
 end
 
---- Map values through a function, preserving keys.
+--- @brief: Maps the values in the table through a mapper function, preserving keys
+--- @param tbl table: Table to map
+--- @param mapper function: a mapping function, e.g. function(v) return v + 1 end
+--- @return table: Product of the operation (new table)
 function table.map(tbl, mapper)
-    if type(tbl) ~= "table" then error("table.map: table argument is not a table (got " .. type(tbl) .. ")") end
-    if type(mapper) ~= "function" then error("table.map: mapper is not a function (got " .. type(mapper) .. ")") end
+    if type(tbl) ~= "table" then
+        error("table.map: table argument is not a table (got " .. type(tbl) .. ")")
+    end
+    if type(mapper) ~= "function" then
+        error("table.map: mapper is not a function (got " .. type(mapper) .. ")")
+    end
     local result = {}
-    for k, v in pairs(tbl) do result[k] = mapper(v) end
+    for k, v in pairs(tbl) do
+        result[k] = mapper(v)
+    end
     return result
 end
 
---- Map values through a function, dropping nils. May leave gaps in a sequence table.
+--- @brief: Maps the values in the table through a mapper function, preserving keys. If the function returns nil, the value is dropped. May leave gaps in a numbered table!
+--- @param tbl table: Table to map
+--- @param mapper function: a mapping function, e.g. function(v) return v + 1 end
+--- @return table: Product of the operation (new table)
 function table.filterMap(tbl, mapper)
-    if type(tbl) ~= "table" then error("table.filterMap: table argument is not a table (got " .. type(tbl) .. ")") end
-    if type(mapper) ~= "function" then error("table.filterMap: mapper is not a function (got " .. type(mapper) .. ")") end
+    if type(tbl) ~= "table" then
+        error("table.filterMap: table argument is not a table (got " .. type(tbl) .. ")")
+    end
+    if type(mapper) ~= "function" then
+        error("table.filterMap: mapper is not a function (got " .. type(mapper) .. ")")
+    end
     local result = {}
     for k, v in pairs(tbl) do
         local res = mapper(v)
-        if res ~= nil then result[k] = res end
+        if res ~= nil then
+            result[k] = res
+        end
     end
     return result
 end
 
---- Map a sequence through a function, dropping nils, producing a gapless sequence.
+--- @brief: Maps the values in the numbered table through a mapper function. If the function returns nil, the value is dropped. Result is a numbered table without gaps.
+--- @param tbl table: Numbered table to map
+--- @param mapper function: a mapping function, e.g. function(v) return v + 1 end
+--- @return table: Product of the operation (new table)
 function table.ifilterMap(tbl, mapper)
-    if type(tbl) ~= "table" then error("table.ifilterMap: argument is not a table (got " .. type(tbl) .. ")") end
-    if type(mapper) ~= "function" then error("table.ifilterMap: mapper is not a function (got " .. type(mapper) .. ")") end
+    if type(tbl) ~= "table" then
+        error("table.ifilterMap: table argument is not a table (got " .. type(tbl) .. ")")
+    end
+    if type(mapper) ~= "function" then
+        error("table.ifilterMap: mapper is not a function (got " .. type(mapper) .. ")")
+    end
     local result = {}
     for i = 1, #tbl do
         local res = mapper(tbl[i])
-        if res ~= nil then result[#result + 1] = res end
+        if res ~= nil then
+            result[#result + 1] = res
+        end
     end
     return result
 end
 
---- Merge tables into a new table. Sequence parts are appended in order; other keys are
---- copied with later arguments overwriting earlier ones. Not recursive; not deep.
+--- @brief Merge tables into a new table. The sequence part (consecutive positive integer keys
+--- starting at 1) of each table is appended in argument order; all other keys (including
+--- non-sequence numeric keys) are copied over, values from later arguments overwriting earlier
+--- ones. Not recursive: nested tables are copied by reference. Errors if an argument is not a table.
+---
+--- Metatable is not copied.
+--- @param ... table: Tables to merge
+--- @return table: Product of the operation (new table)
 function table.merge(...)
     local result = {}
     local n = 0
@@ -100,18 +170,27 @@ end
 local MERGE_DEPTH_LIMIT = 100
 
 local function deepCopy(value, level)
-    if type(value) ~= "table" then return value end
-    if level > MERGE_DEPTH_LIMIT then error("table.deepMerge/deepCopy recursion too deep") end
+    if type(value) ~= "table" then
+        return value
+    end
+    if level > MERGE_DEPTH_LIMIT then
+        error("table.deepMerge/deepCopy recursion too deep")
+    end
     local result = {}
-    for k, v in pairs(value) do result[k] = deepCopy(v, level + 1) end
+    for k, v in pairs(value) do
+        result[k] = deepCopy(v, level + 1)
+    end
     return result
 end
 
 local function mergeRecurse(level, ...)
-    if level > MERGE_DEPTH_LIMIT then error("table.deepMerge recursion too deep") end
+    if level > MERGE_DEPTH_LIMIT then
+        error("table.deepMerge recursion too deep")
+    end
+
     local result = {}
     local n = 0
-    for argi = 1, select('#', ...) do
+    for argi = 1, select("#", ...) do
         local tbl = select(argi, ...)
         if type(tbl) ~= "table" then
             error("table.deepMerge: argument #" .. argi .. " is not a table (got " .. type(tbl) .. ")")
@@ -135,126 +214,235 @@ local function mergeRecurse(level, ...)
     return result
 end
 
---- Recursively merge tables. Nested tables on both sides are merged; other values are overwritten.
---- The result shares no tables with the inputs (everything is deep-copied).
+--- @brief Merge tables recursively into a new table. Sequence parts are appended in argument
+--- order (like table.merge); for other keys, when both sides hold tables they are merged
+--- recursively, otherwise the value from the later argument overwrites the earlier one.
+--- The result shares no tables with the inputs (everything adopted is deep-copied).
+--- Errors if an argument is not a table, or when nesting exceeds a depth limit.
+---
+--- Metatables are not copied.
+--- @param ... table: Tables to merge
+--- @return table: Product of the operation (new table)
 function table.deepMerge(...)
     return mergeRecurse(1, ...)
 end
 
---- Deep-copy a table at all levels (excluding metatables).
+--- @brief Make a deep copy of a table
+---
+--- Raises an error if the value is not a table
+---
+--- @param value table: Table to copy
+--- @return table: Clone of the table at all levels, excluding metatables
 function table.deepCopy(value)
     if type(value) ~= "table" then
         error("table.deepCopy: argument is not a table (got " .. type(value) .. ")")
     end
+
     return deepCopy(value, 1)
 end
 
---- Reduce all values in a table to one using a function. Iteration order is unspecified.
+--- @brief: Reduces all values in a table to a single value using a reducer function & initial value. Iteration order is unspecified.
+--- @param tbl table: Table to reduce
+--- @param reducer function: The reducer function, e.g. function(acc, v) return acc + v end - this computes the sum of all values in the table
+--- @param initialValue any: Starting value of the accumulator
+--- @return any: Result of the reduction
 function table.reduce(tbl, reducer, initialValue)
-    if type(tbl) ~= "table" then error("table.reduce: table argument is not a table (got " .. type(tbl) .. ")") end
-    if type(reducer) ~= "function" then error("table.reduce: reducer is not a function (got " .. type(reducer) .. ")") end
+    if type(tbl) ~= "table" then
+        error("table.reduce: table argument is not a table (got " .. type(tbl) .. ")")
+    end
+    if type(reducer) ~= "function" then
+        error("table.reduce: reducer is not a function (got " .. type(reducer) .. ")")
+    end
     local accumulator = initialValue
-    for _, v in pairs(tbl) do accumulator = reducer(accumulator, v) end
+    for _, v in pairs(tbl) do
+        accumulator = reducer(accumulator, v)
+    end
     return accumulator
 end
 
---- Reduce a sequence table to one value, iterating in order.
+--- @brief: Reduces a numbered table to a single value using a reducer function & initial value, iterating the sequence part in order. Other keys are ignored.
+--- @param tbl table: Numbered table to reduce
+--- @param reducer function: The reducer function, e.g. function(acc, v) return acc .. v end - this concatenates all values in order
+--- @param initialValue any: Starting value of the accumulator
+--- @return any: Result of the reduction
 function table.ireduce(tbl, reducer, initialValue)
-    if type(tbl) ~= "table" then error("table.ireduce: table argument is not a table (got " .. type(tbl) .. ")") end
-    if type(reducer) ~= "function" then error("table.ireduce: reducer is not a function (got " .. type(reducer) .. ")") end
+    if type(tbl) ~= "table" then
+        error("table.ireduce: table argument is not a table (got " .. type(tbl) .. ")")
+    end
+    if type(reducer) ~= "function" then
+        error("table.ireduce: reducer is not a function (got " .. type(reducer) .. ")")
+    end
     local accumulator = initialValue
-    for _, v in ipairs(tbl) do accumulator = reducer(accumulator, v) end
+    for _, v in ipairs(tbl) do
+        accumulator = reducer(accumulator, v)
+    end
     return accumulator
 end
 
---- Return the minimum value in a table. Returns nil for an empty table. NaN propagates.
+--- @brief: Get the lowest of all values in a table (any table, all values are visited).
+--- Returns nil if the table is empty. If any value is NaN, the result is NaN.
+--- @param tbl table: Table to search
+--- @return any: The lowest value, or nil if the table is empty
 function table.min(tbl)
-    if type(tbl) ~= "table" then error("table.min: argument is not a table (got " .. type(tbl) .. ")") end
+    if type(tbl) ~= "table" then
+        error("table.min: argument is not a table (got " .. type(tbl) .. ")")
+    end
     local min
     for _, val in pairs(tbl) do
-        if val ~= val then return val end
-        if min == nil or val < min then min = val end
+        if val ~= val then
+            return val -- NaN propagates
+        end
+        if min == nil or val < min then
+            min = val
+        end
     end
     return min
 end
 
---- Return the maximum value in a table. Returns nil for an empty table. NaN propagates.
+--- @brief: Get the highest of all values in a table (any table, all values are visited).
+--- Returns nil if the table is empty. If any value is NaN, the result is NaN.
+--- @param tbl table: Table to search
+--- @return any: The highest value, or nil if the table is empty
 function table.max(tbl)
-    if type(tbl) ~= "table" then error("table.max: argument is not a table (got " .. type(tbl) .. ")") end
+    if type(tbl) ~= "table" then
+        error("table.max: argument is not a table (got " .. type(tbl) .. ")")
+    end
     local max
     for _, val in pairs(tbl) do
-        if val ~= val then return val end
-        if max == nil or val > max then max = val end
+        if val ~= val then
+            return val -- NaN propagates
+        end
+        if max == nil or val > max then
+            max = val
+        end
     end
     return max
 end
 
---- Return the arithmetic mean of all values. Returns nil for an empty table. NaN propagates.
+--- @brief: Get the mean of all values in a table (any table, all values are visited).
+--- Returns nil if the table is empty. If any value is NaN, the result is NaN.
+--- @param tbl table: Table to average
+--- @return number|nil: Mean of the values, or nil if the table is empty
 function table.mean(tbl)
-    if type(tbl) ~= "table" then error("table.mean: argument is not a table (got " .. type(tbl) .. ")") end
+    if type(tbl) ~= "table" then
+        error("table.mean: argument is not a table (got " .. type(tbl) .. ")")
+    end
     local sum
     local count = 0
     for _, val in pairs(tbl) do
         count = count + 1
-        sum = sum and sum + val or val
+        if sum == nil then
+            sum = val
+        else
+            sum = sum + val
+        end
+    end
+    if count == 0 then
+        return nil
     end
-    return count > 0 and sum / count or nil
+    return sum / count
 end
 
---- Return the sum of all values. Returns 0 for an empty table. NaN propagates.
+--- @brief: Get the sum of all values in a table (any table, all values are visited).
+--- Returns 0 if the table is empty. If any value is NaN, the result is NaN.
+--- @param tbl table: Table to sum
+--- @return number: Sum of the values, 0 for an empty table
 function table.sum(tbl)
-    if type(tbl) ~= "table" then error("table.sum: argument is not a table (got " .. type(tbl) .. ")") end
+    if type(tbl) ~= "table" then
+        error("table.sum: argument is not a table (got " .. type(tbl) .. ")")
+    end
     local sum = 0
-    for _, val in pairs(tbl) do sum = sum + val end
+    for _, val in pairs(tbl) do
+        sum = sum + val
+    end
     return sum
 end
 
---- Return an array of all keys. Order is unspecified.
+--- @brief: Get an array of all keys in the table. Order is unspecified.
+--- @param tbl table: Table to take the keys from
+--- @return table: New numbered table with all keys
 function table.keys(tbl)
-    if type(tbl) ~= "table" then error("table.keys: argument is not a table (got " .. type(tbl) .. ")") end
+    if type(tbl) ~= "table" then
+        error("table.keys: argument is not a table (got " .. type(tbl) .. ")")
+    end
     local result = {}
-    for k in pairs(tbl) do result[#result + 1] = k end
+    for k, _ in pairs(tbl) do
+        result[#result + 1] = k
+    end
     return result
 end
 
---- Return an array of all values. Order is unspecified.
+--- @brief: Get an array of all values in the table. Order is unspecified.
+--- @param tbl table: Table to take the values from
+--- @return table: New numbered table with all values
 function table.values(tbl)
-    if type(tbl) ~= "table" then error("table.values: argument is not a table (got " .. type(tbl) .. ")") end
+    if type(tbl) ~= "table" then
+        error("table.values: argument is not a table (got " .. type(tbl) .. ")")
+    end
     local result = {}
-    for _, v in pairs(tbl) do result[#result + 1] = v end
+    for _, v in pairs(tbl) do
+        result[#result + 1] = v
+    end
     return result
 end
 
---- Return true if the table contains the given value (compared with ==).
+--- @brief: Check if a table contains a specific value.
+--- @param tbl table: Table to check
+--- @param value any: Value to search for (compared with ==)
+--- @return boolean: True if the table contains the given element
 function table.contains(tbl, value)
-    if type(tbl) ~= "table" then error("table.contains: argument is not a table (got " .. type(tbl) .. ")") end
+    if type(tbl) ~= "table" then
+        error("table.contains: argument is not a table (got " .. type(tbl) .. ")")
+    end
     for _, v in pairs(tbl) do
-        if v == value then return true end
+        if v == value then
+            return true
+        end
     end
     return false
 end
 
---- Find a value matching a predicate. Returns (value, key) or (nil, nil) if not found.
---- Check the returned key for nil to distinguish a stored false from "not found".
+--- @brief: Find a table element that matches a predicate. Search order is unspecified
+--- (sequence part is in practice visited first, in order).
+--- @param tbl table: Table to check
+--- @param predicate function: Checker function
+--- @return any, any: Matching value, and its index (value, key); If not found, returns nil, nil.
+--- Check the key for nil to distinguish a stored false value from "not found".
 function table.find(tbl, predicate)
-    if type(tbl) ~= "table" then error("table.find: table argument is not a table (got " .. type(tbl) .. ")") end
-    if type(predicate) ~= "function" then error("table.find: predicate is not a function (got " .. type(predicate) .. ")") end
+    if type(tbl) ~= "table" then
+        error("table.find: table argument is not a table (got " .. type(tbl) .. ")")
+    end
+    if type(predicate) ~= "function" then
+        error("table.find: predicate is not a function (got " .. type(predicate) .. ")")
+    end
     for k, v in pairs(tbl) do
-        if predicate(v) then return v, k end
+        if predicate(v) then
+            return v, k
+        end
     end
     return nil, nil
 end
 
---- Return true if the table has no elements.
+--- @brief: Check if a table is empty (has no elements).
+--- @param tbl table: Table to check
+--- @return boolean: True if empty table
 function table.isEmpty(tbl)
-    if type(tbl) ~= "table" then error("table.isEmpty: argument is not a table (got " .. type(tbl) .. ")") end
+    if type(tbl) ~= "table" then
+        error("table.isEmpty: argument is not a table (got " .. type(tbl) .. ")")
+    end
     return next(tbl) == nil
 end
 
---- Return a new array with elements in reverse order.
+--- @brief: Reverse an array. Returns a new array with elements in reverse order.
+--- @param tbl table: Table to reverse
+--- @return table: New table with reversed order
 function table.reverse(tbl)
-    if type(tbl) ~= "table" then error("table.reverse: argument is not a table (got " .. type(tbl) .. ")") end
+    if type(tbl) ~= "table" then
+        error("table.reverse: argument is not a table (got " .. type(tbl) .. ")")
+    end
     local result = {}
-    for i = #tbl, 1, -1 do result[#result + 1] = tbl[i] end
+    for i = #tbl, 1, -1 do
+        result[#result + 1] = tbl[i]
+    end
     return result
 end
diff --git a/lua/stdlib/utils.lua b/lua/stdlib/utils.lua
index 6e8f540..3db9910 100644
--- a/lua/stdlib/utils.lua
+++ b/lua/stdlib/utils.lua
@@ -1,81 +1,103 @@
--- Lua-side of the utils module.
--- utils.NULL, utils.isNull, utils.toJSON, utils.fromJSON are provided by Rust before this runs.
+-- Lua-implemented part of the utils module, extending the global utils table.
+-- The native parts of the module (dump, toJSON, fromJSON, NULL, isNull)
+-- are declared in Rust before this file is loaded.
 
+-- Substituted when a callback throws a nil error value (e.g. plain `error()`),
+-- so that the returned err is always non-nil on failure.
 local NIL_ERROR_PLACEHOLDER = "unspecified error"
 
--- Pretty-print any Lua value as a string.
-local function dumpValue(val, depth, seen)
-    if depth > 20 then return "..." end
-    local t = type(val)
-    if t == "nil" then
-        return "nil"
-    elseif t == "boolean" or t == "number" then
-        return tostring(val)
-    elseif t == "string" then
-        return string.format("%q", val)
-    elseif t == "table" then
-        if utils.isNull(val) then return "null" end
-        if seen[val] then return "<circular>" end
-        seen[val] = true
-        local parts = {}
-        local len = #val
-        if len > 0 then
-            for i = 1, len do
-                parts[i] = dumpValue(val[i], depth + 1, seen)
-            end
-        else
-            for k, v in pairs(val) do
-                local key = type(k) == "string" and k or ("[" .. tostring(k) .. "]")
-                parts[#parts + 1] = key .. " = " .. dumpValue(v, depth + 1, seen)
-            end
-        end
-        seen[val] = nil
-        if #parts == 0 then return "{}" end
-        return "{ " .. table.concat(parts, ", ") .. " }"
-    else
-        return "<" .. t .. ">"
-    end
-end
-
---- Pretty-print any Lua value to a string.
-function utils.dump(val)
-    return dumpValue(val, 0, {})
-end
-
---- Call a function, capturing any error. Returns (result, nil) on success or (nil, err) on failure.
---- Extra arguments are forwarded to the callback, like pcall.
+--- @brief Call a function, capturing any error - like pcall, but with Go-style returns.
+---
+---   local value, err = utils.try(callback)
+---   local value, err = utils.try(callback, arg1, arg2) -- pcall-style shorthand
+---   if err then
+---       print(err)
+---   else
+---       -- handle value
+---   end
+---
+--- - err is nil if the callback succeeded, otherwise the error value
+--- - value is the callback's first return value (nil on error)
+--- - extra arguments are passed to the callback, like with pcall
+---
+--- This is less confusing than pcall when the return value is actually needed.
+--- The thrown error value is passed through as-is, so a table thrown with
+--- error({code = 42}) stays a table. The downside is that the result can't be
+--- used directly as a condition in "if" or "while" - simply use pcall there.
+---
+--- @param callback function: Function to call
+--- @param ... any: Arguments passed to the callback
+--- @return any, any: The callback's first return value and nil, or nil and the error
 function utils.try(callback, ...)
     if type(callback) ~= "function" then
         error("utils.try: callback is not a function (got " .. type(callback) .. ")")
     end
+
     local ok, result = pcall(callback, ...)
-    if ok then return result, nil end
-    if result == nil then result = NIL_ERROR_PLACEHOLDER end
+    if ok then
+        return result, nil
+    end
+    if result == nil then
+        result = NIL_ERROR_PLACEHOLDER
+    end
     return nil, result
 end
 
 local TRYN_MAX_COUNT = 64
 
---- Like utils.try but for functions that return N values.
---- Returns (v1, ..., vN, nil) on success or (nil, ..., nil, err) on failure.
+--- @brief Call a function, capturing any error - like utils.try, but for N return values.
+---
+---   local value1, value2, err = utils.tryn(2, callback)
+---   local value1, value2, err = utils.tryn(2, callback, arg1, arg2) -- pcall-style shorthand
+---   if err then
+---       print(err)
+---   else
+---       -- handle (value1, value2)
+---   end
+---
+--- - err is nil if the callback succeeded, otherwise the error value
+--- - values are the callback's return values, padded with nils or truncated to exactly N
+--- - extra arguments are passed to the callback, like with pcall
+---
+--- This is less confusing than pcall for multiple return values, where the error
+--- and the first value share a slot:
+---
+---   local status, errorOrValue1, value2 = pcall(callback)
+---
+--- @param expectedCount number: How many return values to pass through (integer, 0 to 64)
+--- @param callback function: Function to call
+--- @param ... any: Arguments passed to the callback
+--- @return any ...: expectedCount values followed by the error or nil
 function utils.tryn(expectedCount, callback, ...)
     local count = math.tointeger(expectedCount)
-    if count == nil then error("utils.tryn: expectedCount must be an integer number") end
+    if count == nil then
+        error("utils.tryn: expectedCount must be an integer number")
+    end
     expectedCount = count
-    if expectedCount < 0 then error("utils.tryn: expectedCount must not be negative") end
+    if expectedCount < 0 then
+        error("utils.tryn: expectedCount must not be negative")
+    end
     if expectedCount > TRYN_MAX_COUNT then
         error("utils.tryn: at most " .. TRYN_MAX_COUNT .. " return values are supported")
     end
     if type(callback) ~= "function" then
         error("utils.tryn: callback is not a function (got " .. type(callback) .. ")")
     end
+
     local results = table.pack(pcall(callback, ...))
+
     if results[1] then
+        -- Success: pass through values 2..expectedCount+1 (truncating or nil-padding),
+        -- with nil in the error slot. The explicit assignment overwrites a possible
+        -- extra return value so it cannot leak into the error slot.
         results[expectedCount + 2] = nil
         return table.unpack(results, 2, expectedCount + 2)
     end
+
     local err = results[2]
-    if err == nil then err = NIL_ERROR_PLACEHOLDER end
+    if err == nil then
+        err = NIL_ERROR_PLACEHOLDER
+    end
     local out = {}
     out[expectedCount + 1] = err
     return table.unpack(out, 1, expectedCount + 1)
diff --git a/lua/test.lua b/lua/test.lua
index d9b6711..1c23292 100644
--- a/lua/test.lua
+++ b/lua/test.lua
@@ -1,42 +1,50 @@
 -- Smoke-test for the stdlib extensions.
 
 print("=== math ===")
-print("round(2.5)     =", math.round(2.5))      -- 3
+print("round(2.5)     =", math.round(2.5)) -- 3
 print("round(2.567,2) =", math.round(2.567, 2)) -- 2.57
 print("clamp(10,0,5)  =", math.clamp(10, 0, 5)) -- 5
-print("isFinite(1/0)  =", math.isFinite(1/0))   -- false
-print("isFinite(3.14) =", math.isFinite(3.14))  -- true
-print("sign(-7)       =", math.sign(-7))         -- -1
+print("isFinite(1/0)  =", math.isFinite(1 / 0)) -- false
+print("isFinite(3.14) =", math.isFinite(3.14)) -- true
+print("sign(-7)       =", math.sign(-7)) -- -1
 print("scale(5,0,10,0,100) =", math.scale(5, 0, 10, 0, 100)) -- 50.0
 
 print("\n=== table ===")
-local t = {3, 1, 4, 1, 5}
-print("sum    =", table.sum(t))    -- 14
-print("min    =", table.min(t))    -- 1
-print("max    =", table.max(t))    -- 5
-print("mean   =", table.mean(t))   -- 2.8
-local evens = table.ifilter(t, function(v) return v % 2 == 0 end)
+local t = { 3, 1, 4, 1, 5 }
+print("sum    =", table.sum(t)) -- 14
+print("min    =", table.min(t)) -- 1
+print("max    =", table.max(t)) -- 5
+print("mean   =", table.mean(t)) -- 2.8
+local evens = table.ifilter(t, function(v)
+    return v % 2 == 0
+end)
 print("evens  =", table.concat(evens, ",")) -- 4
-local doubled = table.map({1,2,3}, function(v) return v * 2 end)
+local doubled = table.map({ 1, 2, 3 }, function(v)
+    return v * 2
+end)
 print("doubled=", table.concat(doubled, ",")) -- 2,4,6
-print("deepCopy ok:", table.deepCopy({x={y=1}}).x.y == 1)
-print("merged =", table.concat(table.merge({1,2},{3,4}), ",")) -- 1,2,3,4
+print("deepCopy ok:", table.deepCopy({ x = { y = 1 } }).x.y == 1)
+print("merged =", table.concat(table.merge({ 1, 2 }, { 3, 4 }), ",")) -- 1,2,3,4
 
 print("\n=== utils ===")
 print("dump(nil)     =", utils.dump(nil))
-print("dump({1,2})   =", utils.dump({1, 2}))
-print("dump({x=1})   =", utils.dump({x = 1}))
+print("dump({1,2})   =", utils.dump({ 1, 2 }))
+print("dump({x=1})   =", utils.dump({ x = 1 }))
 print("isNull(NULL)  =", utils.isNull(utils.NULL))
 print("isNull(nil)   =", utils.isNull(nil))
 
-local json = utils.toJSON({name="Alice", age=30, tags={"a","b"}})
+local json = utils.toJSON({ name = "Alice", age = 30, tags = { "a", "b" } })
 print("toJSON =", json)
 local parsed = utils.fromJSON(json)
 print("fromJSON name=", parsed.name, "age=", parsed.age)
 
-local v, err = utils.try(function() return 42 end)
+local v, err = utils.try(function()
+    return 42
+end)
 print("try ok: v=", v, "err=", err)
-local v2, err2 = utils.try(function() error("oops") end)
+local v2, err2 = utils.try(function()
+    error("oops")
+end)
 print("try err: v=", v2, "err ~= nil:", err2 ~= nil)
 
 print("\n=== os ===")
diff --git a/lua/test_sqlite.lua b/lua/test_sqlite.lua
index 2de1581..b058c68 100644
--- a/lua/test_sqlite.lua
+++ b/lua/test_sqlite.lua
@@ -2,8 +2,10 @@
 
 local function assert_eq(actual, expected, msg)
     if actual ~= expected then
-        error(string.format("%s: expected %s, got %s",
-            msg or "assertion failed", tostring(expected), tostring(actual)), 2)
+        error(
+            string.format("%s: expected %s, got %s", msg or "assertion failed", tostring(expected), tostring(actual)),
+            2
+        )
     end
 end
 
@@ -25,7 +27,7 @@ con:execute([[
 -- Positional params, every supported type.
 local changed = con:execute(
     "INSERT INTO people (name, age, score, vip, notes) VALUES (?, ?, ?, ?, ?)",
-    {"Alice", 30, 9.5, true, "first"}
+    { "Alice", 30, 9.5, true, "first" }
 )
 assert_eq(changed, 1, "execute returns rows changed")
 assert_eq(con:changes(), 1, "changes() after insert")
@@ -35,7 +37,7 @@ assert_eq(first_id, 1, "lastInsertRowid")
 -- Named params (mix of :name in SQL).
 con:execute(
     "INSERT INTO people (name, age, score, vip, notes) VALUES (:name, :age, :score, :vip, :notes)",
-    {name = "Bob", age = 42, score = 7.25, vip = false, notes = utils.NULL}
+    { name = "Bob", age = 42, score = 7.25, vip = false, notes = utils.NULL }
 )
 assert_eq(con:lastInsertRowid(), 2, "lastInsertRowid after second insert")
 
@@ -51,33 +53,33 @@ assert_eq(rows[1].notes, "first", "row 1 notes (text round-trip)")
 assert_eq(rows[2].notes, nil, "row 2 notes is nil (NULL round-trip)")
 
 print("=== queryOne ===")
-local bob = con:queryOne("SELECT * FROM people WHERE name = ?", {"Bob"})
+local bob = con:queryOne("SELECT * FROM people WHERE name = ?", { "Bob" })
 assert(bob ~= nil, "queryOne found Bob")
 assert_eq(bob.age, 42, "queryOne Bob age")
 
-local missing = con:queryOne("SELECT * FROM people WHERE name = ?", {"Nobody"})
+local missing = con:queryOne("SELECT * FROM people WHERE name = ?", { "Nobody" })
 assert_eq(missing, nil, "queryOne returns nil for no match")
 
 print("=== UPDATE / DELETE ===")
-local n = con:execute("UPDATE people SET age = age + 1 WHERE name = :who", {who = "Alice"})
+local n = con:execute("UPDATE people SET age = age + 1 WHERE name = :who", { who = "Alice" })
 assert_eq(n, 1, "update affected 1 row")
-assert_eq(con:queryOne("SELECT age FROM people WHERE name = ?", {"Alice"}).age, 31, "age incremented")
+assert_eq(con:queryOne("SELECT age FROM people WHERE name = ?", { "Alice" }).age, 31, "age incremented")
 
-n = con:execute("DELETE FROM people WHERE name = ?", {"Bob"})
+n = con:execute("DELETE FROM people WHERE name = ?", { "Bob" })
 assert_eq(n, 1, "delete affected 1 row")
 assert_eq(#con:query("SELECT * FROM people"), 1, "one row left after delete")
 
 print("=== transaction(fn) — commit ===")
 con:transaction(function()
-    con:execute("INSERT INTO people (name, age) VALUES (?, ?)", {"Carol", 25})
-    con:execute("INSERT INTO people (name, age) VALUES (?, ?)", {"Dave", 28})
+    con:execute("INSERT INTO people (name, age) VALUES (?, ?)", { "Carol", 25 })
+    con:execute("INSERT INTO people (name, age) VALUES (?, ?)", { "Dave", 28 })
 end)
 assert_eq(#con:query("SELECT * FROM people"), 3, "two rows committed")
 
 print("=== transaction(fn) — rollback on error ===")
 local ok, err = pcall(function()
     con:transaction(function()
-        con:execute("INSERT INTO people (name, age) VALUES (?, ?)", {"Eve", 99})
+        con:execute("INSERT INTO people (name, age) VALUES (?, ?)", { "Eve", 99 })
         error("boom")
     end)
 end)
@@ -87,25 +89,27 @@ assert_eq(#con:query("SELECT * FROM people"), 3, "failed transaction rolled back
 
 print("=== manual begin / commit ===")
 con:begin()
-con:execute("INSERT INTO people (name, age) VALUES (?, ?)", {"Frank", 50})
+con:execute("INSERT INTO people (name, age) VALUES (?, ?)", { "Frank", 50 })
 con:commit()
 assert_eq(#con:query("SELECT * FROM people"), 4, "manual commit persisted")
 
 print("=== manual begin / rollback ===")
 con:begin()
-con:execute("INSERT INTO people (name, age) VALUES (?, ?)", {"Grace", 60})
+con:execute("INSERT INTO people (name, age) VALUES (?, ?)", { "Grace", 60 })
 con:rollback()
 assert_eq(#con:query("SELECT * FROM people"), 4, "manual rollback discarded")
 
 print("=== mixed param table is rejected ===")
 local mixed_ok = pcall(function()
-    con:query("SELECT 1 WHERE 1 = ?", {1, key = "x"})
+    con:query("SELECT 1 WHERE 1 = ?", { 1, key = "x" })
 end)
 assert_eq(mixed_ok, false, "mixed positional/named params error")
 
 print("=== close ===")
 con:close()
-local closed_ok = pcall(function() con:query("SELECT 1") end)
+local closed_ok = pcall(function()
+    con:query("SELECT 1")
+end)
 assert_eq(closed_ok, false, "use after close errors")
 
 print("\nAll sqlite checks passed.")
diff --git a/src/lua_tests/async_tests.rs b/src/lua_tests/async_tests.rs
new file mode 100644
index 0000000..fe30c40
--- /dev/null
+++ b/src/lua_tests/async_tests.rs
@@ -0,0 +1,313 @@
+//! Tests for the async parts of the stdlib: os.sleep, task.join and sqlite.
+//! These have no flowbox-rt counterpart and need a tokio runtime, so they live
+//! apart from the ported sync tests.
+
+use std::time::{Duration, Instant};
+
+use super::lua;
+
+#[tokio::test]
+async fn test_os_sleep_actually_sleeps() {
+    let lua = lua();
+
+    let start = Instant::now();
+    lua.load(r#"os.sleep(0.1)"#).exec_async().await.unwrap();
+    let elapsed = start.elapsed();
+
+    assert!(elapsed >= Duration::from_millis(95), "slept only {elapsed:?}");
+    assert!(elapsed < Duration::from_millis(500), "slept too long: {elapsed:?}");
+}
+
+#[tokio::test]
+async fn test_os_sleep_invalid_duration() {
+    let lua = lua();
+
+    // Negative, NaN and infinite durations must raise a Lua error, not panic the host
+    for src in ["os.sleep(-1)", "os.sleep(0/0)", "os.sleep(math.huge)"] {
+        let err = lua.load(src).exec_async().await.unwrap_err();
+        assert!(err.to_string().contains("os.sleep"), "{src}: {err}");
+    }
+}
+
+#[tokio::test]
+async fn test_os_sleep_rejects_huge_finite_duration() {
+    let lua = lua();
+
+    // A huge-but-finite duration must be rejected promptly, not parked forever
+    // (which would read as the runtime hanging). The test itself would hang if
+    // this regressed, so tokio's test timeout / the assertion guards it.
+    let err = lua.load(r#"os.sleep(1e18)"#).exec_async().await.unwrap_err();
+    assert!(err.to_string().contains("os.sleep"), "{err}");
+
+    // A duration within the cap is accepted (0 sleeps instantly).
+    lua.load(r#"os.sleep(0)"#).exec_async().await.unwrap();
+}
+
+#[tokio::test]
+async fn test_task_join_returns_results_positionally() {
+    let lua = lua();
+
+    let (a, b, c): (i64, String, bool) = lua
+        .load(
+            r#"
+            return task.join(
+                function() return 1 end,
+                function() os.sleep(0.01) return "two" end,
+                function() return true end
+            )
+            "#,
+        )
+        .eval_async()
+        .await
+        .unwrap();
+
+    assert_eq!(a, 1);
+    assert_eq!(b, "two");
+    assert!(c);
+}
+
+#[tokio::test]
+async fn test_task_join_runs_concurrently() {
+    let lua = lua();
+
+    let start = Instant::now();
+    lua.load(
+        r#"
+        task.join(
+            function() os.sleep(0.15) end,
+            function() os.sleep(0.1) end,
+            function() os.sleep(0.05) end
+        )
+        "#,
+    )
+    .exec_async()
+    .await
+    .unwrap();
+    let elapsed = start.elapsed();
+
+    // Sequential execution would take ~0.3s; overlapped, the slowest task dominates.
+    assert!(elapsed >= Duration::from_millis(140), "finished too fast: {elapsed:?}");
+    assert!(elapsed < Duration::from_millis(280), "tasks did not overlap: {elapsed:?}");
+}
+
+#[tokio::test]
+async fn test_task_join_rejects_non_function_argument() {
+    let lua = lua();
+
+    // A non-function argument gives a prefixed, positioned error, not mlua's
+    // bare "error converting Lua integer to function".
+    let err = lua
+        .load(r#"task.join(function() end, 42)"#)
+        .exec_async()
+        .await
+        .unwrap_err();
+    let msg = err.to_string();
+    assert!(msg.contains("task.join: argument #2 must be a function"), "{msg}");
+    assert!(msg.contains("integer"), "{msg}");
+}
+
+#[tokio::test]
+async fn test_os_sleep_rejects_non_number() {
+    let lua = lua();
+
+    let err = lua.load(r#"os.sleep("soon")"#).exec_async().await.unwrap_err();
+    let msg = err.to_string();
+    assert!(msg.contains("os.sleep: duration must be a number"), "{msg}");
+}
+
+#[tokio::test]
+async fn test_task_join_propagates_errors() {
+    let lua = lua();
+
+    let err = lua
+        .load(r#"task.join(function() error("boom") end, function() return 1 end)"#)
+        .exec_async()
+        .await
+        .unwrap_err();
+    assert!(err.to_string().contains("boom"));
+}
+
+#[tokio::test]
+async fn test_sqlite_in_memory_roundtrip() {
+    let lua = lua();
+
+    let (name, id, count): (String, i64, i64) = lua
+        .load(
+            r#"
+            local db = sqlite.connect(":memory:")
+            db:execute("CREATE TABLE t (id INTEGER PRIMARY KEY, name TEXT)")
+            db:execute("INSERT INTO t (name) VALUES (?)", {"alice"})
+            db:execute("INSERT INTO t (name) VALUES (?)", {"bob"})
+            local id = db:lastInsertRowid()
+            local row = db:queryOne("SELECT name FROM t WHERE id = ?", {1})
+            local rows = db:query("SELECT * FROM t")
+            db:close()
+            return row.name, id, #rows
+            "#,
+        )
+        .eval_async()
+        .await
+        .unwrap();
+
+    assert_eq!(name, "alice");
+    assert_eq!(id, 2);
+    assert_eq!(count, 2);
+}
+
+#[tokio::test]
+async fn test_sqlite_binds_non_utf8_as_blob() {
+    let lua = lua();
+
+    // A non-UTF-8 / NUL-containing Lua string must bind and round-trip intact
+    // (as a BLOB) rather than failing the UTF-8 conversion.
+    let ok: bool = lua
+        .load(
+            r#"
+            local db = sqlite.connect(":memory:")
+            db:execute("CREATE TABLE t (id INTEGER PRIMARY KEY, data)")
+            local blob = "\255\0\254bin"
+            db:execute("INSERT INTO t (data) VALUES (?)", {blob})
+            local got = db:queryOne("SELECT data FROM t WHERE id = 1").data
+            return got == blob
+            "#,
+        )
+        .eval_async()
+        .await
+        .unwrap();
+    assert!(ok);
+}
+
+#[tokio::test]
+async fn test_sqlite_rejects_empty_and_multi_statements() {
+    let lua = lua();
+
+    let err = lua
+        .load(r#"local db = sqlite.connect(":memory:"); return db:execute("  ")"#)
+        .eval_async::<mlua::Value>()
+        .await
+        .unwrap_err();
+    assert!(err.to_string().contains("no SQL statement"), "{err}");
+
+    // A comment-only statement has no runnable SQL either.
+    let err = lua
+        .load(r#"local db = sqlite.connect(":memory:"); return db:query("-- only a comment")"#)
+        .eval_async::<mlua::Value>()
+        .await
+        .unwrap_err();
+    assert!(err.to_string().contains("no SQL statement"), "{err}");
+
+    let err = lua
+        .load(
+            r#"
+            local db = sqlite.connect(":memory:")
+            db:execute("CREATE TABLE t (x)")
+            return db:execute("INSERT INTO t VALUES (1); INSERT INTO t VALUES (2)")
+            "#,
+        )
+        .eval_async::<mlua::Value>()
+        .await
+        .unwrap_err();
+    assert!(err.to_string().contains("single SQL statement"), "{err}");
+}
+
+#[tokio::test]
+async fn test_sqlite_execute_batch_runs_all_statements() {
+    let lua = lua();
+
+    let count: i64 = lua
+        .load(
+            r#"
+            local db = sqlite.connect(":memory:")
+            db:executeBatch([[
+                CREATE TABLE t (x);
+                INSERT INTO t VALUES (1);
+                INSERT INTO t VALUES (2);
+                INSERT INTO t VALUES (3);
+            ]])
+            return db:queryOne("SELECT COUNT(*) AS n FROM t").n
+            "#,
+        )
+        .eval_async()
+        .await
+        .unwrap();
+    assert_eq!(count, 3);
+}
+
+#[tokio::test]
+async fn test_sqlite_transaction_passes_through_return_values() {
+    let lua = lua();
+
+    let (a, b): (i64, String) = lua
+        .load(
+            r#"
+            local db = sqlite.connect(":memory:")
+            db:execute("CREATE TABLE t (x)")
+            return db:transaction(function() return 7, "eight" end)
+            "#,
+        )
+        .eval_async()
+        .await
+        .unwrap();
+    assert_eq!(a, 7);
+    assert_eq!(b, "eight");
+}
+
+#[tokio::test]
+async fn test_sqlite_transaction_does_not_mask_original_error() {
+    let lua = lua();
+
+    // If the body fails AND rollback then also fails (here: the connection is
+    // closed inside the body), the caller must still see the body's error.
+    let err = lua
+        .load(
+            r#"
+            local db = sqlite.connect(":memory:")
+            db:execute("CREATE TABLE t (x)")
+            db:transaction(function()
+                db:close()
+                error("ORIGINAL ERROR")
+            end)
+            "#,
+        )
+        .exec_async()
+        .await
+        .unwrap_err();
+    assert!(err.to_string().contains("ORIGINAL ERROR"), "{err}");
+}
+
+#[tokio::test]
+async fn test_sqlite_transaction_commit_and_rollback() {
+    let lua = lua();
+
+    let (after_commit, after_rollback): (i64, i64) = lua
+        .load(
+            r#"
+            local db = sqlite.connect(":memory:")
+            db:execute("CREATE TABLE t (x)")
+
+            db:transaction(function()
+                db:execute("INSERT INTO t VALUES (1)")
+            end)
+            local committed = db:queryOne("SELECT COUNT(*) AS n FROM t").n
+
+            local ok, err = pcall(function()
+                db:transaction(function()
+                    db:execute("INSERT INTO t VALUES (2)")
+                    error("nope")
+                end)
+            end)
+            assert(not ok)
+            assert(tostring(err):find("nope"))
+            local rolled_back = db:queryOne("SELECT COUNT(*) AS n FROM t").n
+
+            return committed, rolled_back
+            "#,
+        )
+        .eval_async()
+        .await
+        .unwrap();
+
+    assert_eq!(after_commit, 1);
+    // The failed transaction's insert must have been rolled back.
+    assert_eq!(after_rollback, 1);
+}
diff --git a/src/lua_tests/core_tests.rs b/src/lua_tests/core_tests.rs
new file mode 100644
index 0000000..619b54f
--- /dev/null
+++ b/src/lua_tests/core_tests.rs
@@ -0,0 +1,226 @@
+//! Core environment tests: basic Lua evaluation, sandbox verification, and
+//! checks that the stdlib extends rather than replaces the standard modules.
+//!
+//! Ported from flowbox-rt's fb_lua core_tests, with sandbox-verification
+//! tests added for this project's sandbox (see src/sandbox.rs).
+
+use super::assert_eq_f64;
+
+/// Smoke test for the environment setup
+#[test]
+fn test_call_lua_function() {
+    let lua = super::lua();
+
+    let chunk: mlua::Function = lua
+        .load(
+            r#"
+            function(a, b)
+                return a + b
+            end
+            "#,
+        )
+        .eval()
+        .unwrap();
+
+    let res: i32 = chunk.call((10, 20)).unwrap();
+    assert_eq!(res, 30);
+}
+
+/// dofile, loadfile and load (raw bytecode loading) are removed from the sandbox.
+#[test]
+fn test_sandbox_chunk_loaders_removed() {
+    let lua = super::lua();
+
+    for name in ["dofile", "loadfile", "load"] {
+        let is_nil: bool = lua.load(format!("return {name} == nil")).eval().unwrap();
+        assert!(is_nil, "global `{name}` should be nil in the sandbox");
+    }
+}
+
+/// string.dump (bytecode producer, the counterpart of load) is removed.
+#[test]
+fn test_sandbox_string_dump_removed() {
+    let lua = super::lua();
+
+    let is_nil: bool = lua.load(r#"return string.dump == nil"#).eval().unwrap();
+    assert!(is_nil, "string.dump should be nil in the sandbox");
+}
+
+/// io, package and debug libraries are not loaded at all.
+#[test]
+fn test_sandbox_io_package_debug_not_loaded() {
+    let lua = super::lua();
+
+    for name in ["io", "package", "debug"] {
+        let is_nil: bool = lua.load(format!("return {name} == nil")).eval().unwrap();
+        assert!(is_nil, "global `{name}` should be nil in the sandbox");
+    }
+}
+
+/// collectgarbage only allows the "count" option; everything else raises
+/// an error mentioning the sandbox.
+#[test]
+fn test_sandbox_collectgarbage_count_only() {
+    let lua = super::lua();
+
+    let count: f64 = lua.load(r#"return collectgarbage("count")"#).eval().unwrap();
+    assert!(count > 0.0, "collectgarbage(\"count\") should report heap KB, got {count}");
+
+    let err = lua.load(r#"return collectgarbage()"#).exec().unwrap_err();
+    assert!(err.to_string().contains("sandboxed"), "unexpected error: {err}");
+
+    let err = lua.load(r#"return collectgarbage("collect")"#).exec().unwrap_err();
+    assert!(err.to_string().contains("sandboxed"), "unexpected error: {err}");
+}
+
+/// The os table only keeps the safe time functions plus our extensions.
+#[test]
+fn test_sandbox_os_dangerous_functions_removed() {
+    let lua = super::lua();
+
+    let os_table = lua.globals().get::<mlua::Table>("os").unwrap();
+    for name in ["execute", "exit", "getenv", "remove", "rename", "setlocale", "tmpname"] {
+        assert!(
+            !os_table.contains_key(name).unwrap(),
+            "os.{name} should be removed from the sandbox"
+        );
+    }
+    for name in ["date", "difftime", "time", "clock", "microtime", "sleep"] {
+        assert!(
+            os_table.contains_key(name).unwrap(),
+            "os.{name} should be present in the sandbox"
+        );
+    }
+}
+
+/// Verify that the math table was extended with custom functions,
+/// not replaced - standard Lua math functions must still exist.
+#[test]
+fn test_math_table_extended_not_replaced() {
+    let lua = super::lua();
+
+    // Test standard math functions still work
+    let result: f64 = lua.load(r#"return math.floor(3.7)"#).eval().unwrap();
+    assert_eq_f64!(result, 3.0);
+
+    let result: f64 = lua.load(r#"return math.ceil(3.2)"#).eval().unwrap();
+    assert_eq_f64!(result, 4.0);
+
+    let result: f64 = lua.load(r#"return math.abs(-5)"#).eval().unwrap();
+    assert_eq_f64!(result, 5.0);
+
+    let result: f64 = lua.load(r#"return math.sqrt(16)"#).eval().unwrap();
+    assert_eq_f64!(result, 4.0);
+
+    let result: f64 = lua.load(r#"return math.sin(0)"#).eval().unwrap();
+    assert_eq_f64!(result, 0.0);
+
+    let result: f64 = lua.load(r#"return math.cos(0)"#).eval().unwrap();
+    assert_eq_f64!(result, 1.0);
+
+    let result: f64 = lua.load(r#"return math.max(1, 5, 3)"#).eval().unwrap();
+    assert_eq_f64!(result, 5.0);
+
+    let result: f64 = lua.load(r#"return math.min(1, 5, 3)"#).eval().unwrap();
+    assert_eq_f64!(result, 1.0);
+
+    // Verify math.pi constant exists
+    let result: f64 = lua.load(r#"return math.pi"#).eval().unwrap();
+    assert!(result > 3.14 && result < 3.15);
+
+    // Verify our custom functions are also present
+    let result: i64 = lua.load(r#"return math.round(3.7)"#).eval().unwrap();
+    assert_eq!(result, 4);
+
+    let result: f64 = lua.load(r#"return math.round(3.1415, 2)"#).eval().unwrap();
+    assert_eq_f64!(result, 3.14);
+
+    let result: i64 = lua.load(r#"return math.clamp(50, 0, 100)"#).eval().unwrap();
+    assert_eq!(result, 50);
+}
+
+/// Verify that the table module was extended with custom functions,
+/// not replaced - standard Lua table functions must still exist.
+#[test]
+fn test_table_module_extended_not_replaced() {
+    let lua = super::lua();
+
+    // Test standard table functions still work
+    // table.insert
+    let result: String = lua
+        .load(
+            r#"
+            local t = {1, 2, 3}
+            table.insert(t, 4)
+            return utils.toJSON(t)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, "[1,2,3,4]");
+
+    // table.remove
+    let result: String = lua
+        .load(
+            r#"
+            local t = {1, 2, 3, 4}
+            table.remove(t, 2)
+            return utils.toJSON(t)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, "[1,3,4]");
+
+    // table.concat
+    let result: String = lua.load(r#"return table.concat({"a", "b", "c"}, "-")"#).eval().unwrap();
+    assert_eq!(result, "a-b-c");
+
+    // table.sort
+    let result: String = lua
+        .load(
+            r#"
+            local t = {3, 1, 4, 1, 5, 9}
+            table.sort(t)
+            return utils.toJSON(t)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, "[1,1,3,4,5,9]");
+
+    // table.unpack
+    let result: i64 = lua
+        .load(
+            r#"
+            local t = {10, 20, 30}
+            local a, b, c = table.unpack(t)
+            return a + b + c
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, 60);
+
+    // Verify our custom functions are also present
+    let _: () = lua
+        .load(
+            r#"
+            local ro = table.readonly({x = 1})
+            assert(ro.x == 1)
+            "#,
+        )
+        .exec()
+        .unwrap();
+
+    let result: String = lua
+        .load(
+            r#"
+            local merged = table.merge({a = 1}, {b = 2})
+            return utils.toJSON(merged)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(result.contains("\"a\":1") && result.contains("\"b\":2"));
+}
diff --git a/src/lua_tests/math_tests.rs b/src/lua_tests/math_tests.rs
new file mode 100644
index 0000000..1f9ab62
--- /dev/null
+++ b/src/lua_tests/math_tests.rs
@@ -0,0 +1,398 @@
+//! Tests for the math stdlib extensions (lua/stdlib/math.lua).
+
+use super::assert_eq_f64;
+use mlua::prelude::LuaValue;
+
+#[test]
+fn test_clamp() {
+    let lua = super::lua();
+
+    // Simple, integers
+    let result: i64 = lua.load(r#"return math.clamp(3, 10, 20)"#).eval().unwrap();
+    assert_eq!(result, 10); // low
+    let result: i64 = lua.load(r#"return math.clamp(3, nil, 20)"#).eval().unwrap();
+    assert_eq!(result, 3); // low-unbounded
+
+    let result: i64 = lua.load(r#"return math.clamp(15, 10, 20)"#).eval().unwrap();
+    assert_eq!(result, 15); // inside
+
+    let result: i64 = lua.load(r#"return math.clamp(25, 10, 20)"#).eval().unwrap();
+    assert_eq!(result, 20); // high
+    let result: i64 = lua.load(r#"return math.clamp(25, 10, nil)"#).eval().unwrap();
+    assert_eq!(result, 25); // high-unbounded
+
+    let result: i64 = lua.load(r#"return math.clamp(999, nil, nil)"#).eval().unwrap();
+    assert_eq!(result, 999); // unbounded
+
+    // Floats
+    let result: f64 = lua.load(r#"return math.clamp(3.5, 10.5, 20.5)"#).eval().unwrap();
+    assert_eq_f64!(result, 10.5); // low
+    let result: f64 = lua.load(r#"return math.clamp(3.5, nil, 20.5)"#).eval().unwrap();
+    assert_eq_f64!(result, 3.5); // low-unbounded
+
+    let result: f64 = lua.load(r#"return math.clamp(15.5, 10.5, 20.5)"#).eval().unwrap();
+    assert_eq_f64!(result, 15.5); // inside
+
+    let result: f64 = lua.load(r#"return math.clamp(25.5, 10.5, 20.5)"#).eval().unwrap();
+    assert_eq_f64!(result, 20.5); // high
+    let result: f64 = lua.load(r#"return math.clamp(25.5, 10.5, nil)"#).eval().unwrap();
+    assert_eq_f64!(result, 25.5); // high-unbounded
+
+    let result: f64 = lua.load(r#"return math.clamp(999.9, nil, nil)"#).eval().unwrap();
+    assert_eq_f64!(result, 999.9); // unbounded
+
+    // Check some negative numbers
+    let result: i64 = lua.load(r#"return math.clamp(3, -10, 20)"#).eval().unwrap();
+    assert_eq!(result, 3); // low
+    let result: i64 = lua.load(r#"return math.clamp(-15, -10, 20)"#).eval().unwrap();
+    assert_eq!(result, -10); // inside
+    let result: i64 = lua.load(r#"return math.clamp(-25, -10, 20)"#).eval().unwrap();
+    assert_eq!(result, -10); // high
+    let result: i64 = lua.load(r#"return math.clamp(25, -10, 20)"#).eval().unwrap();
+    assert_eq!(result, 20); // high
+
+    assert!(lua.load(r#"return math.clamp(nil, 1, 2)"#).eval::<LuaValue>().is_err());
+    assert!(lua.load(r#"return math.clamp(1, "1", 2)"#).eval::<LuaValue>().is_err());
+    assert!(lua.load(r#"return math.clamp(1, "foo", 2)"#).eval::<LuaValue>().is_err());
+    assert!(lua.load(r#"return math.clamp(1, 1, "bar")"#).eval::<LuaValue>().is_err());
+    assert!(lua.load(r#"return math.clamp(1, 1, "2")"#).eval::<LuaValue>().is_err());
+
+    // Crossed bounds (min > max) is a programming error, not a valid interval
+    let err = lua.load(r#"return math.clamp(5, 10, 0)"#).exec().unwrap_err();
+    assert!(err.to_string().contains("greater than"));
+}
+
+#[test]
+fn test_round() {
+    let lua = super::lua();
+
+    // Round positive numbers
+    let result: i64 = lua.load(r#"return math.round(3.4)"#).eval().unwrap();
+    assert_eq!(result, 3);
+
+    let result: i64 = lua.load(r#"return math.round(3.5)"#).eval().unwrap();
+    assert_eq!(result, 4);
+
+    let result: i64 = lua.load(r#"return math.round(3.9)"#).eval().unwrap();
+    assert_eq!(result, 4);
+
+    // Round negative numbers
+    let result: i64 = lua.load(r#"return math.round(-3.4)"#).eval().unwrap();
+    assert_eq!(result, -3);
+
+    let result: i64 = lua.load(r#"return math.round(-3.5)"#).eval().unwrap();
+    assert_eq!(result, -4);
+
+    // Round whole numbers (should stay the same)
+    let result: i64 = lua.load(r#"return math.round(5)"#).eval().unwrap();
+    assert_eq!(result, 5);
+
+    let result: i64 = lua.load(r#"return math.round(0)"#).eval().unwrap();
+    assert_eq!(result, 0);
+
+    // Round with a non-number should error
+    let err = lua.load(r#"return math.round("not a number")"#).exec().unwrap_err();
+    assert!(err.to_string().contains("non-number"));
+
+    // NaN must error, not silently become 0
+    let err = lua.load(r#"return math.round(0/0)"#).exec().unwrap_err();
+    assert!(err.to_string().contains("finite"));
+
+    // Infinity must error (out of integer range)
+    assert!(lua.load(r#"return math.round(math.huge)"#).exec().is_err());
+    assert!(lua.load(r#"return math.round(-math.huge)"#).exec().is_err());
+
+    // Out of i64 range must error
+    assert!(lua.load(r#"return math.round(1e19)"#).exec().is_err());
+    assert!(lua.load(r#"return math.round(-1e19)"#).exec().is_err());
+
+    // Half away from zero at exactly +-0.5
+    let result: i64 = lua.load(r#"return math.round(0.5)"#).eval().unwrap();
+    assert_eq!(result, 1);
+    let result: i64 = lua.load(r#"return math.round(-0.5)"#).eval().unwrap();
+    assert_eq!(result, -1);
+
+    // The naive floor(value + 0.5) trap: 0.49999999999999994 + 0.5 == 1.0 in f64,
+    // but the nearest integer is 0
+    let result: i64 = lua.load(r#"return math.round(0.49999999999999994)"#).eval().unwrap();
+    assert_eq!(result, 0);
+    let result: i64 = lua.load(r#"return math.round(-0.49999999999999994)"#).eval().unwrap();
+    assert_eq!(result, 0);
+
+    // Integer-valued floats at the edge of f64 precision (2^53)
+    let result: i64 = lua.load(r#"return math.round(2.0^53 - 1.0)"#).eval().unwrap();
+    assert_eq!(result, 9007199254740991);
+    let result: i64 = lua.load(r#"return math.round(2.0^53)"#).eval().unwrap();
+    assert_eq!(result, 9007199254740992);
+
+    // -2^63 is exactly representable as a float and is a valid Lua integer...
+    let result: bool = lua.load(r#"return math.round(-2.0^63) == math.mininteger"#).eval().unwrap();
+    assert!(result);
+
+    // ...but 2^63 is one above math.maxinteger and must error
+    assert!(lua.load(r#"return math.round(2.0^63)"#).exec().is_err());
+}
+
+//noinspection RsApproxConstant
+#[test]
+fn test_round_to_places() {
+    let lua = super::lua();
+
+    // roundn was merged into round - it must no longer exist
+    let result: bool = lua.load(r#"return math.roundn == nil"#).eval().unwrap();
+    assert!(result);
+
+    // places = 0 behaves like the one-argument form and returns an integer
+    let result: String = lua.load(r#"return math.type(math.round(3.1415, 0))"#).eval().unwrap();
+    assert_eq!(result, "integer");
+    let result: i64 = lua.load(r#"return math.round(3.7, 0)"#).eval().unwrap();
+    assert_eq!(result, 4);
+
+    // places > 0 rounds to N decimal places and returns a float
+    let result: f64 = lua.load(r#"return math.round(3.1415, 1)"#).eval().unwrap();
+    assert_eq_f64!(result, 3.1);
+
+    let result: f64 = lua.load(r#"return math.round(3.1415, 3)"#).eval().unwrap();
+    assert_eq_f64!(result, 3.142);
+
+    let result: f64 = lua.load(r#"return math.round(2.567, 2)"#).eval().unwrap();
+    assert_eq_f64!(result, 2.57);
+
+    let result: String = lua.load(r#"return math.type(math.round(3.1415, 2))"#).eval().unwrap();
+    assert_eq!(result, "float");
+
+    // Integer input with places > 0 returns the same value as a float
+    let result: String = lua.load(r#"return math.type(math.round(5, 2))"#).eval().unwrap();
+    assert_eq!(result, "float");
+    let result: f64 = lua.load(r#"return math.round(5, 2)"#).eval().unwrap();
+    assert_eq_f64!(result, 5.0);
+
+    // Negative numbers round half away from zero
+    let result: f64 = lua.load(r#"return math.round(-2.345, 2)"#).eval().unwrap();
+    assert_eq_f64!(result, -2.35);
+
+    // Huge values must not overflow to infinity via the 10^places multiplier
+    let result: f64 = lua.load(r#"return math.round(1.5e308, 2)"#).eval().unwrap();
+    assert_eq_f64!(result, 1.5e308);
+
+    // Huge places are a no-op (cannot change any f64), not an overflow
+    let result: f64 = lua.load(r#"return math.round(12.5, 400)"#).eval().unwrap();
+    assert_eq_f64!(result, 12.5);
+
+    // Tiny values still round correctly with large places
+    let result: f64 = lua.load(r#"return math.round(1.23e-300, 300)"#).eval().unwrap();
+    assert_eq_f64!(result, 1.0e-300);
+
+    // Places given as an integral float is accepted
+    let result: f64 = lua.load(r#"return math.round(3.14159, 2.0)"#).eval().unwrap();
+    assert_eq_f64!(result, 3.14);
+
+    // Non-integral places must error
+    assert!(lua.load(r#"return math.round(3.14, 2.5)"#).exec().is_err());
+
+    // Negative places must error with a clear message
+    let err = lua.load(r#"return math.round(3.14, -2)"#).exec().unwrap_err();
+    assert!(err.to_string().contains("negative"));
+
+    // NaN must error
+    let err = lua.load(r#"return math.round(0/0, 2)"#).exec().unwrap_err();
+    assert!(err.to_string().contains("finite"));
+
+    // Infinity must error
+    assert!(lua.load(r#"return math.round(math.huge, 2)"#).exec().is_err());
+
+    // Non-number must error
+    let err = lua.load(r#"return math.round("foo", 2)"#).exec().unwrap_err();
+    assert!(err.to_string().contains("non-number"));
+}
+
+#[test]
+fn test_is_finite() {
+    let lua = super::lua();
+
+    // Regular numbers are finite
+    let result: bool = lua.load(r#"return math.isFinite(42)"#).eval().unwrap();
+    assert!(result);
+
+    let result: bool = lua.load(r#"return math.isFinite(-3.14)"#).eval().unwrap();
+    assert!(result);
+
+    let result: bool = lua.load(r#"return math.isFinite(0)"#).eval().unwrap();
+    assert!(result);
+
+    // Infinity is not finite
+    let result: bool = lua.load(r#"return math.isFinite(math.huge)"#).eval().unwrap();
+    assert!(!result);
+
+    let result: bool = lua.load(r#"return math.isFinite(-math.huge)"#).eval().unwrap();
+    assert!(!result);
+
+    // NaN is not finite (0/0 produces NaN)
+    let result: bool = lua.load(r#"return math.isFinite(0/0)"#).eval().unwrap();
+    assert!(!result);
+
+    // Non-numbers return false
+    let result: bool = lua.load(r#"return math.isFinite("hello")"#).eval().unwrap();
+    assert!(!result);
+
+    let result: bool = lua.load(r#"return math.isFinite(nil)"#).eval().unwrap();
+    assert!(!result);
+
+    let result: bool = lua.load(r#"return math.isFinite({})"#).eval().unwrap();
+    assert!(!result);
+
+    // Very large numbers are still finite
+    let result: bool = lua.load(r#"return math.isFinite(1e308)"#).eval().unwrap();
+    assert!(result);
+
+    // But overflow to infinity is not
+    let result: bool = lua.load(r#"return math.isFinite(1e309)"#).eval().unwrap();
+    assert!(!result);
+}
+
+#[test]
+fn test_sign() {
+    let lua = super::lua();
+
+    // Positive numbers return 1
+    let result: i64 = lua.load(r#"return math.sign(42)"#).eval().unwrap();
+    assert_eq!(result, 1);
+
+    let result: i64 = lua.load(r#"return math.sign(0.001)"#).eval().unwrap();
+    assert_eq!(result, 1);
+
+    // Negative numbers return -1
+    let result: i64 = lua.load(r#"return math.sign(-42)"#).eval().unwrap();
+    assert_eq!(result, -1);
+
+    let result: i64 = lua.load(r#"return math.sign(-0.001)"#).eval().unwrap();
+    assert_eq!(result, -1);
+
+    // Zero returns 0
+    let result: i64 = lua.load(r#"return math.sign(0)"#).eval().unwrap();
+    assert_eq!(result, 0);
+
+    // Negative zero is still zero
+    let result: i64 = lua.load(r#"return math.sign(-0)"#).eval().unwrap();
+    assert_eq!(result, 0);
+
+    // Positive infinity returns 1
+    let result: i64 = lua.load(r#"return math.sign(math.huge)"#).eval().unwrap();
+    assert_eq!(result, 1);
+
+    // Negative infinity returns -1
+    let result: i64 = lua.load(r#"return math.sign(-math.huge)"#).eval().unwrap();
+    assert_eq!(result, -1);
+
+    // NaN returns 0 (NaN is not > 0 and not < 0)
+    let result: i64 = lua.load(r#"return math.sign(0/0)"#).eval().unwrap();
+    assert_eq!(result, 0);
+
+    // Error on non-number
+    let err = lua.load(r#"return math.sign("foo")"#).exec().unwrap_err();
+    assert!(err.to_string().contains("Non-number"));
+}
+
+#[test]
+fn test_scale() {
+    let lua = super::lua();
+
+    // Scale 0-100 to 0-1
+    let result: f64 = lua.load(r#"return math.scale(50, 0, 100, 0, 1)"#).eval().unwrap();
+    assert_eq_f64!(result, 0.5);
+
+    // Scale 0-100 to 0-10
+    let result: f64 = lua.load(r#"return math.scale(25, 0, 100, 0, 10)"#).eval().unwrap();
+    assert_eq_f64!(result, 2.5);
+
+    // Scale with offset ranges
+    let result: f64 = lua.load(r#"return math.scale(15, 10, 20, 100, 200)"#).eval().unwrap();
+    assert_eq_f64!(result, 150.0);
+
+    // Scale to inverted range
+    let result: f64 = lua.load(r#"return math.scale(0, 0, 100, 100, 0)"#).eval().unwrap();
+    assert_eq_f64!(result, 100.0);
+
+    let result: f64 = lua.load(r#"return math.scale(100, 0, 100, 100, 0)"#).eval().unwrap();
+    assert_eq_f64!(result, 0.0);
+
+    // Value outside input range (no clamp)
+    let result: f64 = lua.load(r#"return math.scale(150, 0, 100, 0, 10)"#).eval().unwrap();
+    assert_eq_f64!(result, 15.0);
+
+    let result: f64 = lua.load(r#"return math.scale(-50, 0, 100, 0, 10)"#).eval().unwrap();
+    assert_eq_f64!(result, -5.0);
+
+    // Value outside input range with clamp=true
+    let result: f64 = lua.load(r#"return math.scale(150, 0, 100, 0, 10, true)"#).eval().unwrap();
+    assert_eq_f64!(result, 10.0);
+
+    let result: f64 = lua.load(r#"return math.scale(-50, 0, 100, 0, 10, true)"#).eval().unwrap();
+    assert_eq_f64!(result, 0.0);
+
+    // Clamp with inverted output range
+    let result: f64 = lua.load(r#"return math.scale(150, 0, 100, 10, 0, true)"#).eval().unwrap();
+    assert_eq_f64!(result, 0.0);
+
+    let result: f64 = lua.load(r#"return math.scale(-50, 0, 100, 10, 0, true)"#).eval().unwrap();
+    assert_eq_f64!(result, 10.0);
+
+    // Clamp=false (explicit) behaves same as default
+    let result: f64 = lua.load(r#"return math.scale(150, 0, 100, 0, 10, false)"#).eval().unwrap();
+    assert_eq_f64!(result, 15.0);
+
+    // Zero-width output range is allowed (always returns outMin)
+    let result: f64 = lua.load(r#"return math.scale(50, 0, 100, 5, 5)"#).eval().unwrap();
+    assert_eq_f64!(result, 5.0);
+
+    // Boundary values
+    let result: f64 = lua.load(r#"return math.scale(0, 0, 100, 0, 10)"#).eval().unwrap();
+    assert_eq_f64!(result, 0.0);
+
+    let result: f64 = lua.load(r#"return math.scale(100, 0, 100, 0, 10)"#).eval().unwrap();
+    assert_eq_f64!(result, 10.0);
+
+    // Negative input range
+    let result: f64 = lua.load(r#"return math.scale(-50, -100, 0, 0, 10)"#).eval().unwrap();
+    assert_eq_f64!(result, 5.0);
+
+    // Inverted input range (inMin > inMax)
+    let result: f64 = lua.load(r#"return math.scale(75, 100, 0, 0, 10)"#).eval().unwrap();
+    assert_eq_f64!(result, 2.5);
+
+    // Error on zero-width input range (division by zero)
+    let err = lua.load(r#"return math.scale(50, 100, 100, 0, 10)"#).exec().unwrap_err();
+    assert!(err.to_string().contains("Input range cannot be zero"));
+
+    // Error on non-number value
+    let err = lua.load(r#"return math.scale("foo", 0, 100, 0, 10)"#).exec().unwrap_err();
+    assert!(err.to_string().contains("Non-number"));
+
+    // Error on non-number range
+    let err = lua.load(r#"return math.scale(50, "a", 100, 0, 10)"#).exec().unwrap_err();
+    assert!(err.to_string().contains("Non-number"));
+
+    // Infinity input produces infinity output (no clamp)
+    let result: bool = lua
+        .load(r#"return math.scale(math.huge, 0, 100, 0, 10) == math.huge"#)
+        .eval()
+        .unwrap();
+    assert!(result);
+
+    // Infinity input with clamp gets clamped
+    let result: f64 = lua.load(r#"return math.scale(math.huge, 0, 100, 0, 10, true)"#).eval().unwrap();
+    assert_eq_f64!(result, 10.0);
+
+    let result: f64 = lua
+        .load(r#"return math.scale(-math.huge, 0, 100, 0, 10, true)"#)
+        .eval()
+        .unwrap();
+    assert_eq_f64!(result, 0.0);
+
+    // NaN input produces NaN output
+    let result: bool = lua
+        .load(r#"local r = math.scale(0/0, 0, 100, 0, 10); return r ~= r"#)
+        .eval()
+        .unwrap();
+    assert!(result); // NaN ~= NaN is true
+}
diff --git a/src/lua_tests/mod.rs b/src/lua_tests/mod.rs
new file mode 100644
index 0000000..7d501de
--- /dev/null
+++ b/src/lua_tests/mod.rs
@@ -0,0 +1,41 @@
+//! Tests for the Lua stdlib, ported from flowbox-rt's fb_lua `lua_tests` and
+//! adapted to this project's sandbox and stdlib.
+
+mod async_tests;
+mod core_tests;
+mod math_tests;
+mod os_tests;
+mod table_tests;
+mod utils_tests;
+
+use mlua::Lua;
+
+/// A fresh sandboxed Lua with the full stdlib installed - the same state scripts get.
+pub(crate) fn lua() -> Lua {
+    crate::sandbox::create_sandboxed_lua().unwrap()
+}
+
+/// Compare two JSON strings as parsed values (key order independent).
+#[allow(dead_code)]
+pub(crate) fn json_eq(a: &str, b: &str) -> bool {
+    let a: serde_json::Value = serde_json::from_str(a).unwrap();
+    let b: serde_json::Value = serde_json::from_str(b).unwrap();
+    a == b
+}
+
+/// Assert that two f64 values are equal within an epsilon (default `f64::EPSILON`).
+macro_rules! assert_eq_f64 {
+    ($a:expr, $b:expr) => {
+        assert_eq_f64!($a, $b, f64::EPSILON)
+    };
+    ($a:expr, $b:expr, $eps:expr) => {{
+        let (a, b): (f64, f64) = ($a, $b);
+        let eps: f64 = $eps;
+        assert!(
+            (a - b).abs() <= eps,
+            "assertion failed: `(left !== right)` (left: `{a:?}`, right: `{b:?}`, epsilon: `{eps:?}`, diff: `{:?}`)",
+            (a - b).abs()
+        );
+    }};
+}
+pub(crate) use assert_eq_f64;
diff --git a/src/lua_tests/os_tests.rs b/src/lua_tests/os_tests.rs
new file mode 100644
index 0000000..9a45624
--- /dev/null
+++ b/src/lua_tests/os_tests.rs
@@ -0,0 +1,173 @@
+//! Tests for the sandboxed `os` table.
+//!
+//! Ported from flowbox-rt's fb_lua os_tests. Unlike flowbox, this project
+//! keeps the real Lua 5.5 os.date/os.time/os.difftime (flowbox used a
+//! chrono-based shim), so a few edge cases differ - see individual tests.
+//! os.sleep is async here and is covered by async_tests, not this file.
+
+use std::time::{Duration, Instant};
+
+#[test]
+fn test_os_time_now() {
+    let lua = super::lua();
+
+    let result: i64 = lua.load(r#"return os.time()"#).eval().unwrap();
+    let now = chrono::Utc::now().timestamp();
+    assert!((result - now).abs() <= 5, "os.time() = {result}, expected ~{now}");
+}
+
+#[test]
+fn test_os_time_from_table() {
+    let lua = super::lua();
+
+    // Round trip through local time - independent of the host timezone
+    let ok: bool = lua
+        .load(
+            r#"
+            local t = os.time({year = 2020, month = 1, day = 15, hour = 10, min = 30, sec = 20})
+            local d = os.date("*t", t)
+            return d.year == 2020 and d.month == 1 and d.day == 15
+                and d.hour == 10 and d.min == 30 and d.sec == 20
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(ok);
+
+    // Out-of-range fields are normalized like mktime; hour defaults to 12
+    let ok: bool = lua
+        .load(
+            r#"
+            local a = os.time({year = 2020, month = 14, day = 1})
+            local b = os.time({year = 2021, month = 2, day = 1})
+            return a == b
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(ok);
+
+    // The normalized fields are written back into the table
+    let ok: bool = lua
+        .load(
+            r#"
+            local tbl = {year = 2020, month = 14, day = 1}
+            os.time(tbl)
+            return tbl.year == 2021 and tbl.month == 2 and tbl.day == 1
+                and tbl.hour == 12 and tbl.wday == 2 -- 2021-02-01 was a Monday
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(ok);
+
+    // Missing mandatory field is an error
+    let ok: bool = lua.load(r#"return (pcall(os.time, {year = 2020}))"#).eval().unwrap();
+    assert!(!ok);
+}
+
+#[test]
+fn test_os_date_format() {
+    let lua = super::lua();
+
+    let result: String = lua.load(r#"return os.date("!%Y-%m-%dT%H:%M:%S", 1000000000)"#).eval().unwrap();
+    assert_eq!(result, "2001-09-09T01:46:40");
+
+    // Epoch
+    let result: String = lua.load(r#"return os.date("!%Y-%m-%d %H:%M:%S", 0)"#).eval().unwrap();
+    assert_eq!(result, "1970-01-01 00:00:00");
+
+    // Stock Lua difference: flowbox's chrono shim truncated float time values;
+    // real Lua 5.5 requires an integer-representable time and raises an error.
+    let ok: bool = lua.load(r#"return (pcall(os.date, "!%Y-%m-%d", 0.9))"#).eval().unwrap();
+    assert!(!ok, "os.date with a fractional time value should raise in stock Lua");
+
+    // Default format is %c, applied to the current time
+    let result: String = lua.load(r#"return os.date()"#).eval().unwrap();
+    assert!(!result.is_empty());
+
+    // Invalid format specifier is an error, not garbage output
+    let ok: bool = lua.load(r#"return (pcall(os.date, "%Q"))"#).eval().unwrap();
+    assert!(!ok);
+}
+
+#[test]
+fn test_os_date_table() {
+    let lua = super::lua();
+
+    // 2001-09-09T01:46:40Z was a Sunday, day 252 of the year
+    let ok: bool = lua
+        .load(
+            r#"
+            local d = os.date("!*t", 1000000000)
+            return d.year == 2001 and d.month == 9 and d.day == 9
+                and d.hour == 1 and d.min == 46 and d.sec == 40
+                and d.wday == 1 and d.yday == 252
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(ok);
+}
+
+/// os.clock is replaced with monotonic wall time since state creation.
+#[test]
+fn test_os_clock() {
+    let start = Instant::now();
+    let lua = super::lua();
+
+    std::thread::sleep(Duration::from_millis(30));
+
+    let clock: f64 = lua.load(r#"return os.clock()"#).eval().unwrap();
+    assert!(
+        (start.elapsed().as_secs_f64() - clock).abs() < 0.1,
+        "Clock function works"
+    );
+
+    // 200 ms elapses, so it should be reported accurately
+    std::thread::sleep(Duration::from_millis(200));
+    let clock2: f64 = lua.load(r#"return os.clock()"#).eval().unwrap();
+
+    assert!((clock2 - clock - 0.2) < 0.03, "Clock tracks time");
+}
+
+#[test]
+fn test_os_difftime() {
+    let lua = super::lua();
+
+    let result: f64 = lua.load(r#"return os.difftime(10, 4)"#).eval().unwrap();
+    assert_eq!(result, 6.0);
+
+    let ok: bool = lua.load(r#"return (pcall(os.difftime, 10))"#).eval().unwrap();
+    assert!(!ok);
+}
+
+#[test]
+fn test_os_missing_dangerous_functions() {
+    let lua = super::lua();
+
+    let os_table = lua.globals().get::<mlua::Table>("os").unwrap();
+    for name in ["execute", "exit", "getenv", "remove", "rename", "setlocale", "tmpname"] {
+        assert!(
+            !os_table.contains_key(name).unwrap(),
+            "os.{name} should be removed from the sandbox"
+        );
+    }
+}
+
+#[test]
+fn test_os_microtime() {
+    let lua = super::lua();
+
+    let result1: f64 = lua.load(r#"return os.microtime()"#).eval().unwrap();
+    std::thread::sleep(Duration::from_millis(100));
+    let result2: f64 = lua.load(r#"return os.microtime()"#).eval().unwrap();
+    assert!(
+        (result2 - result1 - 0.1).abs() < 0.03,
+        "os.microtime() should return fractional seconds"
+    );
+
+    // It is a Unix timestamp
+    let now = chrono::Utc::now().timestamp() as f64;
+    assert!((result2 - now).abs() <= 5.0, "os.microtime() = {result2}, expected ~{now}");
+}
diff --git a/src/lua_tests/table_tests.rs b/src/lua_tests/table_tests.rs
new file mode 100644
index 0000000..82d61c8
--- /dev/null
+++ b/src/lua_tests/table_tests.rs
@@ -0,0 +1,1497 @@
+//! Tests for the `table` stdlib extensions (lua/stdlib/table.lua).
+//! Ported from flowbox-rt's fb_lua lua_tests/table_tests.rs.
+
+use super::assert_eq_f64;
+use super::json_eq;
+
+#[test]
+fn test_readonly_lua_function() {
+    let lua = super::lua();
+
+    // Test that reads work on readonly table
+    let result: i64 = lua
+        .load(
+            r#"
+            local t = {foo = 42, bar = "hello"}
+            local ro = table.readonly(t)
+            return ro.foo
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, 42);
+
+    // Test that writes fail on readonly table
+    let write_result = lua.load(
+        r#"
+        local t = {foo = 42}
+        local ro = table.readonly(t)
+        ro.foo = 100
+        "#,
+    );
+    let err = write_result.exec().unwrap_err();
+    assert!(err.to_string().contains("read-only table"));
+
+    // Test adding new keys also fails
+    let add_result = lua.load(
+        r#"
+        local t = {foo = 42}
+        local ro = table.readonly(t)
+        ro.new_key = "value"
+        "#,
+    );
+    let err = add_result.exec().unwrap_err();
+    assert!(err.to_string().contains("read-only table"));
+}
+
+#[test]
+fn test_readonly_with_name() {
+    let lua = super::lua();
+
+    // Reads still pass through when a name is given
+    let val: i64 = lua
+        .load(
+            r#"
+            local ro = table.readonly({x = 1}, "MyTable")
+            return ro.x
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(val, 1);
+
+    // The name is included in the write error message
+    let err = lua
+        .load(
+            r#"
+            local ro = table.readonly({x = 1}, "MyTable")
+            ro.x = 2
+            "#,
+        )
+        .exec()
+        .unwrap_err();
+    assert!(err.to_string().contains("read-only table MyTable"));
+}
+
+#[test]
+fn test_readonly_metatable_protected() {
+    let lua = super::lua();
+
+    // The metatable must not be reachable - otherwise scripts could mutate
+    // the protected table through getmetatable(ro).__index
+    let result: bool = lua
+        .load(
+            r#"
+            local ro = table.readonly({x = 1})
+            return getmetatable(ro) == false
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(result);
+
+    // Replacing the metatable must fail too
+    let err = lua
+        .load(
+            r#"
+            local ro = table.readonly({x = 1})
+            setmetatable(ro, {})
+            "#,
+        )
+        .exec()
+        .unwrap_err();
+    assert!(err.to_string().contains("protected metatable"));
+}
+
+#[test]
+fn test_merge_tables() {
+    let lua = super::lua();
+
+    // Merge two tables with string keys (second overwrites first)
+    let result: String = lua
+        .load(
+            r#"
+            local a = {x = 1, y = 2}
+            local b = {y = 10, z = 3}
+            local merged = table.merge(a, b)
+            return utils.toJSON(merged)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(json_eq(&result, r#"{"x":1,"y":10,"z":3}"#));
+
+    // Merge array-style tables (numeric keys append)
+    let result: String = lua
+        .load(
+            r#"
+            local a = {1, 2, 3}
+            local b = {4, 5}
+            local merged = table.merge(a, b)
+            return utils.toJSON(merged)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, "[1,2,3,4,5]");
+
+    // Merge more than two tables
+    let result: String = lua
+        .load(
+            r#"
+            local a = {x = 1}
+            local b = {y = 2}
+            local c = {z = 3}
+            local merged = table.merge(a, b, c)
+            return utils.toJSON(merged)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(json_eq(&result, r#"{"x":1,"y":2,"z":3}"#));
+
+    // Empty table handling
+    let result: String = lua
+        .load(
+            r#"
+            local a = {x = 42}
+            local merged = table.merge({}, a, {})
+            return utils.toJSON(merged)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(json_eq(&result, r#"{"x":42}"#));
+
+    // Original tables are not modified
+    let result: String = lua
+        .load(
+            r#"
+            local a = {x = 1}
+            local b = {x = 2}
+            local _ = table.merge(a, b)
+            return utils.toJSON(a)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(json_eq(&result, r#"{"x":1}"#));
+
+    // Nested tables are NOT recursively merged (shallow merge)
+    let result: String = lua
+        .load(
+            r#"
+            local a = {config = {a = 1, b = 2}}
+            local b = {config = {c = 3}}
+            local merged = table.merge(a, b)
+            return utils.toJSON(merged)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    // config is overwritten entirely, not merged
+    assert!(json_eq(&result, r#"{"config":{"c":3}}"#));
+}
+
+#[test]
+fn test_deep_merge_tables() {
+    let lua = super::lua();
+
+    // Simple merge (same as table.merge for flat tables)
+    let result: String = lua
+        .load(
+            r#"
+            local a = {x = 1, y = 2}
+            local b = {y = 10, z = 3}
+            local merged = table.deepMerge(a, b)
+            return utils.toJSON(merged)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(json_eq(&result, r#"{"x":1,"y":10,"z":3}"#));
+
+    // Deep merge of nested tables
+    let result: String = lua
+        .load(
+            r#"
+            local a = {config = {a = 1, b = 2}}
+            local b = {config = {b = 20, c = 3}}
+            local merged = table.deepMerge(a, b)
+            return utils.toJSON(merged)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    // config is merged recursively
+    assert!(json_eq(&result, r#"{"config":{"a":1,"b":20,"c":3}}"#));
+
+    // Multiple levels of nesting
+    let result: String = lua
+        .load(
+            r#"
+            local a = {a = {b = {c = {val = 1}}}}
+            local b = {a = {b = {c = {other = 2}, d = 3}}}
+            local merged = table.deepMerge(a, b)
+            return utils.toJSON(merged)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(json_eq(&result, r#"{"a":{"b":{"c":{"other":2,"val":1},"d":3}}}"#));
+
+    // Table overwrites non-table
+    let result: String = lua
+        .load(
+            r#"
+            local a = {x = 1}
+            local b = {x = {nested = 42}}
+            local merged = table.deepMerge(a, b)
+            return utils.toJSON(merged)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(json_eq(&result, r#"{"x":{"nested":42}}"#));
+
+    // Non-table overwrites table
+    let result: String = lua
+        .load(
+            r#"
+            local a = {x = {nested = 42}}
+            local b = {x = 100}
+            local merged = table.deepMerge(a, b)
+            return utils.toJSON(merged)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(json_eq(&result, r#"{"x":100}"#));
+
+    // Merge more than two tables with nesting
+    let result: String = lua
+        .load(
+            r#"
+            local a = {config = {a = 1}}
+            local b = {config = {b = 2}}
+            local c = {config = {c = 3}}
+            local merged = table.deepMerge(a, b, c)
+            return utils.toJSON(merged)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(json_eq(&result, r#"{"config":{"a":1,"b":2,"c":3}}"#));
+
+    // Array-style tables append (same as table.merge)
+    let result: String = lua
+        .load(
+            r#"
+            local a = {1, 2}
+            local b = {3, 4}
+            local merged = table.deepMerge(a, b)
+            return utils.toJSON(merged)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, "[1,2,3,4]");
+
+    // Original tables are not modified
+    let result: String = lua
+        .load(
+            r#"
+            local a = {config = {val = 1}}
+            local b = {config = {val = 2}}
+            local _ = table.deepMerge(a, b)
+            return utils.toJSON(a)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(json_eq(&result, r#"{"config":{"val":1}}"#));
+
+    // Recursion limit protection (should error at depth > 100)
+    let err = lua
+        .load(
+            r#"
+            local function buildDeep(depth)
+                if depth == 0 then
+                    return {val = 1}
+                end
+                return {nested = buildDeep(depth - 1)}
+            end
+            local a = buildDeep(101)
+            local b = buildDeep(101)
+            return table.deepMerge(a, b)
+            "#,
+        )
+        .exec();
+    assert!(err.is_err());
+    assert!(err.unwrap_err().to_string().contains("recursion too deep"));
+}
+
+#[test]
+fn test_filter() {
+    let lua = super::lua();
+
+    // Filter array with predicate - preserves sequential numeric keys, serializes as array
+    let result: String = lua
+        .load(
+            r#"
+            local t = {1, 2, 3, 4, 5, 6}
+            local filtered = table.filter(t, function(v) return v <= 3 end)
+            return utils.toJSON(filtered)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, "[1,2,3]");
+
+    // Filter dictionary with predicate
+    let result: String = lua
+        .load(
+            r#"
+            local t = {a = 10, b = 20, c = 30, d = 5}
+            local filtered = table.filter(t, function(v) return v >= 15 end)
+            return utils.toJSON(filtered)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(json_eq(&result, r#"{"b":20,"c":30}"#));
+
+    // Filter with empty result
+    let result: String = lua
+        .load(
+            r#"
+            local t = {1, 2, 3}
+            local filtered = table.filter(t, function(v) return v > 100 end)
+            return utils.toJSON(filtered)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, "{}");
+
+    // Filter empty table
+    let result: String = lua
+        .load(
+            r#"
+            local t = {}
+            local filtered = table.filter(t, function(v) return true end)
+            return utils.toJSON(filtered)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, "{}");
+
+    // Original table unmodified
+    let result: String = lua
+        .load(
+            r#"
+            local t = {a = 1, b = 2, c = 3}
+            local _ = table.filter(t, function(v) return v == 2 end)
+            return utils.toJSON(t)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(json_eq(&result, r#"{"a":1,"b":2,"c":3}"#));
+}
+
+#[test]
+fn test_ifilter() {
+    let lua = super::lua();
+
+    // ifilter produces numbered table without gaps
+    let result: String = lua
+        .load(
+            r#"
+            local t = {1, 2, 3, 4, 5, 6}
+            local filtered = table.ifilter(t, function(v) return v % 2 == 0 end)
+            return utils.toJSON(filtered)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    // Should be a clean array [2, 4, 6] without gaps
+    assert_eq!(result, "[2,4,6]");
+
+    // ifilter with none matching
+    let result: String = lua
+        .load(
+            r#"
+            local t = {1, 2, 3}
+            local filtered = table.ifilter(t, function(v) return v > 100 end)
+            return utils.toJSON(filtered)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, "{}");
+
+    // ifilter with all matching
+    let result: String = lua
+        .load(
+            r#"
+            local t = {10, 20, 30}
+            local filtered = table.ifilter(t, function(v) return v >= 5 end)
+            return utils.toJSON(filtered)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, "[10,20,30]");
+
+    // ifilter preserves order
+    let result: String = lua
+        .load(
+            r#"
+            local t = {"a", "bb", "ccc", "dddd", "eeeee"}
+            local filtered = table.ifilter(t, function(v) return #v >= 3 end)
+            return utils.toJSON(filtered)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, r#"["ccc","dddd","eeeee"]"#);
+
+    // Original table unmodified
+    let result: String = lua
+        .load(
+            r#"
+            local t = {1, 2, 3, 4, 5}
+            local _ = table.ifilter(t, function(v) return v == 3 end)
+            return utils.toJSON(t)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, "[1,2,3,4,5]");
+}
+
+#[test]
+fn test_map() {
+    let lua = super::lua();
+
+    // Map array values
+    let result: String = lua
+        .load(
+            r#"
+            local t = {1, 2, 3}
+            local mapped = table.map(t, function(v) return v * 2 end)
+            return utils.toJSON(mapped)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, "[2,4,6]");
+
+    // Map dictionary values
+    let result: String = lua
+        .load(
+            r#"
+            local t = {a = 1, b = 2, c = 3}
+            local mapped = table.map(t, function(v) return v + 10 end)
+            return utils.toJSON(mapped)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(json_eq(&result, r#"{"a":11,"b":12,"c":13}"#));
+
+    // Map to different types
+    let result: String = lua
+        .load(
+            r#"
+            local t = {1, 2, 3}
+            local mapped = table.map(t, function(v) return "val" .. v end)
+            return utils.toJSON(mapped)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, r#"["val1","val2","val3"]"#);
+
+    // Map empty table
+    let result: String = lua
+        .load(
+            r#"
+            local t = {}
+            local mapped = table.map(t, function(v) return v * 2 end)
+            return utils.toJSON(mapped)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, "{}");
+
+    // Original table unmodified
+    let result: String = lua
+        .load(
+            r#"
+            local t = {x = 100}
+            local _ = table.map(t, function(v) return v * 999 end)
+            return utils.toJSON(t)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(json_eq(&result, r#"{"x":100}"#));
+}
+
+#[test]
+fn test_filter_map() {
+    let lua = super::lua();
+
+    // filterMap drops nil results
+    let result: String = lua
+        .load(
+            r#"
+            local t = {a = 1, b = 2, c = 3, d = 4}
+            local mapped = table.filterMap(t, function(v)
+                if v % 2 == 0 then
+                    return v * 10
+                else
+                    return nil
+                end
+            end)
+            return utils.toJSON(mapped)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(json_eq(&result, r#"{"b":20,"d":40}"#));
+
+    // filterMap all pass (none return nil)
+    let result: String = lua
+        .load(
+            r#"
+            local t = {x = 5, y = 10}
+            local mapped = table.filterMap(t, function(v) return v + 1 end)
+            return utils.toJSON(mapped)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(json_eq(&result, r#"{"x":6,"y":11}"#));
+
+    // filterMap all filtered (all return nil)
+    let result: String = lua
+        .load(
+            r#"
+            local t = {a = 1, b = 2}
+            local mapped = table.filterMap(t, function(v) return nil end)
+            return utils.toJSON(mapped)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, "{}");
+
+    // filterMap on numbered table may leave gaps (preserves keys)
+    let result: String = lua
+        .load(
+            r#"
+            local t = {10, 20, 30, 40, 50}
+            local mapped = table.filterMap(t, function(v)
+                if v > 20 then return v end
+                return nil
+            end)
+            -- Check that the result has correct values even if keys are sparse
+            local count = 0
+            local sum = 0
+            for _, v in pairs(mapped) do
+                count = count + 1
+                sum = sum + v
+            end
+            return count .. ":" .. sum
+            "#,
+        )
+        .eval()
+        .unwrap();
+    // Should have 3 values: 30, 40, 50 summing to 120
+    assert_eq!(result, "3:120");
+}
+
+#[test]
+fn test_ifilter_map() {
+    let lua = super::lua();
+
+    // ifilterMap produces numbered table without gaps
+    let result: String = lua
+        .load(
+            r#"
+            local t = {1, 2, 3, 4, 5}
+            local mapped = table.ifilterMap(t, function(v)
+                if v % 2 == 1 then
+                    return v * 100
+                end
+                return nil
+            end)
+            return utils.toJSON(mapped)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    // Should produce clean array [100, 300, 500]
+    assert_eq!(result, "[100,300,500]");
+
+    // ifilterMap preserves order
+    let result: String = lua
+        .load(
+            r#"
+            local t = {"apple", "banana", "cherry", "date"}
+            local mapped = table.ifilterMap(t, function(v)
+                if #v > 5 then
+                    return string.upper(v)
+                end
+                return nil
+            end)
+            return utils.toJSON(mapped)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, r#"["BANANA","CHERRY"]"#);
+
+    // ifilterMap empty result
+    let result: String = lua
+        .load(
+            r#"
+            local t = {1, 2, 3}
+            local mapped = table.ifilterMap(t, function(v) return nil end)
+            return utils.toJSON(mapped)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, "{}");
+
+    // ifilterMap all values pass
+    let result: String = lua
+        .load(
+            r#"
+            local t = {10, 20, 30}
+            local mapped = table.ifilterMap(t, function(v) return v // 10 end)
+            return utils.toJSON(mapped)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    // Using integer division (//) to get integers
+    assert_eq!(result, "[1,2,3]");
+}
+
+#[test]
+fn test_reduce() {
+    let lua = super::lua();
+
+    // Sum of values
+    let result: i64 = lua
+        .load(
+            r#"
+            local t = {1, 2, 3, 4, 5}
+            return table.reduce(t, function(acc, v) return acc + v end, 0)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, 15);
+
+    // Product of values
+    let result: i64 = lua
+        .load(
+            r#"
+            local t = {2, 3, 4}
+            return table.reduce(t, function(acc, v) return acc * v end, 1)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, 24);
+
+    // String concatenation
+    let result: String = lua
+        .load(
+            r#"
+            local t = {"hello", " ", "world"}
+            return table.reduce(t, function(acc, v) return acc .. v end, "")
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, "hello world");
+
+    // Reduce empty table returns initial value
+    let result: i64 = lua
+        .load(
+            r#"
+            local t = {}
+            return table.reduce(t, function(acc, v) return acc + v end, 42)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, 42);
+
+    // Reduce dictionary values (order unspecified but result should be deterministic)
+    let result: i64 = lua
+        .load(
+            r#"
+            local t = {a = 10, b = 20, c = 30}
+            return table.reduce(t, function(acc, v) return acc + v end, 0)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, 60);
+
+    // Reduce with complex accumulator (count and sum)
+    let result: String = lua
+        .load(
+            r#"
+            local t = {5, 10, 15, 20}
+            local r = table.reduce(t, function(acc, v)
+                acc.count = acc.count + 1
+                acc.sum = acc.sum + v
+                return acc
+            end, {count = 0, sum = 0})
+            return r.count .. ":" .. r.sum
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, "4:50");
+}
+
+#[test]
+fn test_min() {
+    let lua = super::lua();
+
+    // Min of positive numbers
+    let result: i64 = lua.load(r#"return table.min({5, 3, 8, 1, 9})"#).eval().unwrap();
+    assert_eq!(result, 1);
+
+    // Min with negative numbers
+    let result: i64 = lua.load(r#"return table.min({-5, 3, -8, 1, 9})"#).eval().unwrap();
+    assert_eq!(result, -8);
+
+    // Min of floats
+    let result: f64 = lua.load(r#"return table.min({3.14, 2.71, 1.41})"#).eval().unwrap();
+    assert_eq_f64!(result, 1.41);
+
+    // Min with single element
+    let result: i64 = lua.load(r#"return table.min({42})"#).eval().unwrap();
+    assert_eq!(result, 42);
+
+    // Min of empty table returns nil
+    let result: bool = lua.load(r#"return table.min({}) == nil"#).eval().unwrap();
+    assert!(result);
+
+    // Min works on dictionary values too (uses pairs)
+    let result: i64 = lua.load(r#"return table.min({a = 100, b = 50, c = 75})"#).eval().unwrap();
+    assert_eq!(result, 50);
+}
+
+#[test]
+fn test_max() {
+    let lua = super::lua();
+
+    // Max of positive numbers
+    let result: i64 = lua.load(r#"return table.max({5, 3, 8, 1, 9})"#).eval().unwrap();
+    assert_eq!(result, 9);
+
+    // Max with negative numbers
+    let result: i64 = lua.load(r#"return table.max({-5, -3, -8, -1, -9})"#).eval().unwrap();
+    assert_eq!(result, -1);
+
+    // Max of floats
+    let result: f64 = lua.load(r#"return table.max({3.14, 2.71, 1.41})"#).eval().unwrap();
+    assert_eq_f64!(result, 3.14);
+
+    // Max with single element
+    let result: i64 = lua.load(r#"return table.max({42})"#).eval().unwrap();
+    assert_eq!(result, 42);
+
+    // Max of empty table returns nil
+    let result: bool = lua.load(r#"return table.max({}) == nil"#).eval().unwrap();
+    assert!(result);
+
+    // Max works on dictionary values too
+    let result: i64 = lua.load(r#"return table.max({a = 100, b = 50, c = 75})"#).eval().unwrap();
+    assert_eq!(result, 100);
+}
+
+#[test]
+fn test_mean() {
+    let lua = super::lua();
+
+    // Mean of integers
+    let result: f64 = lua.load(r#"return table.mean({10, 20, 30})"#).eval().unwrap();
+    assert_eq_f64!(result, 20.0);
+
+    // Mean of floats: (1.5 + 2.5 + 3.0) / 3 = 7.0 / 3
+    let result: f64 = lua.load(r#"return table.mean({1.5, 2.5, 3.0})"#).eval().unwrap();
+    assert_eq_f64!(result, 7.0 / 3.0);
+
+    // Mean with single element
+    let result: f64 = lua.load(r#"return table.mean({42})"#).eval().unwrap();
+    assert_eq_f64!(result, 42.0);
+
+    // Mean of empty table returns nil (consistent with min/max)
+    let result: bool = lua.load(r#"return table.mean({}) == nil"#).eval().unwrap();
+    assert!(result);
+
+    // Mean with negative numbers
+    let result: f64 = lua.load(r#"return table.mean({-10, 0, 10})"#).eval().unwrap();
+    assert_eq_f64!(result, 0.0);
+
+    // Mean works on dictionary values too
+    let result: f64 = lua.load(r#"return table.mean({a = 100, b = 200, c = 300})"#).eval().unwrap();
+    assert_eq_f64!(result, 200.0);
+}
+
+#[test]
+fn test_sum() {
+    let lua = super::lua();
+
+    // Sum of integers
+    let result: i64 = lua.load(r#"return table.sum({1, 2, 3, 4, 5})"#).eval().unwrap();
+    assert_eq!(result, 15);
+
+    // Sum of floats
+    let result: f64 = lua.load(r#"return table.sum({1.5, 2.5, 3.0})"#).eval().unwrap();
+    assert_eq_f64!(result, 7.0);
+
+    // Sum with negative numbers
+    let result: i64 = lua.load(r#"return table.sum({-10, 5, -5, 10})"#).eval().unwrap();
+    assert_eq!(result, 0);
+
+    // Sum of empty table returns 0 (unlike min/max/mean which return nil)
+    let result: i64 = lua.load(r#"return table.sum({})"#).eval().unwrap();
+    assert_eq!(result, 0);
+
+    // The 0 result of an empty sum is an integer
+    let result: String = lua.load(r#"return math.type(table.sum({}))"#).eval().unwrap();
+    assert_eq!(result, "integer");
+
+    // Sum works on dictionary values
+    let result: i64 = lua.load(r#"return table.sum({a = 10, b = 20, c = 30})"#).eval().unwrap();
+    assert_eq!(result, 60);
+
+    // Sum with single element
+    let result: i64 = lua.load(r#"return table.sum({42})"#).eval().unwrap();
+    assert_eq!(result, 42);
+}
+
+#[test]
+fn test_keys() {
+    let lua = super::lua();
+
+    // Keys of a dictionary - order unspecified, so check via sorting
+    let result: String = lua
+        .load(
+            r#"
+            local k = table.keys({a = 1, b = 2, c = 3})
+            table.sort(k)
+            return utils.toJSON(k)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, r#"["a","b","c"]"#);
+
+    // Keys of an array are numeric indices
+    let result: String = lua
+        .load(
+            r#"
+            local k = table.keys({"x", "y", "z"})
+            table.sort(k)
+            return utils.toJSON(k)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, "[1,2,3]");
+
+    // Keys of empty table
+    let result: String = lua.load(r#"return utils.toJSON(table.keys({}))"#).eval().unwrap();
+    assert_eq!(result, "{}");
+
+    // Keys count matches table size
+    let result: i64 = lua.load(r#"return #table.keys({a = 1, b = 2, c = 3, d = 4})"#).eval().unwrap();
+    assert_eq!(result, 4);
+}
+
+#[test]
+fn test_values() {
+    let lua = super::lua();
+
+    // Values of a dictionary - order unspecified, so check via sorting
+    let result: String = lua
+        .load(
+            r#"
+            local v = table.values({a = 10, b = 20, c = 30})
+            table.sort(v)
+            return utils.toJSON(v)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, "[10,20,30]");
+
+    // Values of an array
+    let result: String = lua
+        .load(
+            r#"
+            local v = table.values({"x", "y", "z"})
+            table.sort(v)
+            return utils.toJSON(v)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, r#"["x","y","z"]"#);
+
+    // Values of empty table
+    let result: String = lua.load(r#"return utils.toJSON(table.values({}))"#).eval().unwrap();
+    assert_eq!(result, "{}");
+
+    // Values count matches table size
+    let result: i64 = lua
+        .load(r#"return #table.values({a = 1, b = 2, c = 3, d = 4})"#)
+        .eval()
+        .unwrap();
+    assert_eq!(result, 4);
+}
+
+#[test]
+fn test_contains() {
+    let lua = super::lua();
+
+    // Contains in array
+    let result: bool = lua.load(r#"return table.contains({1, 2, 3, 4, 5}, 3)"#).eval().unwrap();
+    assert!(result);
+
+    // Does not contain
+    let result: bool = lua.load(r#"return table.contains({1, 2, 3, 4, 5}, 99)"#).eval().unwrap();
+    assert!(!result);
+
+    // Contains in dictionary values
+    let result: bool = lua
+        .load(r#"return table.contains({a = "foo", b = "bar"}, "bar")"#)
+        .eval()
+        .unwrap();
+    assert!(result);
+
+    // Does not check keys, only values
+    let result: bool = lua.load(r#"return table.contains({a = 1, b = 2}, "a")"#).eval().unwrap();
+    assert!(!result);
+
+    // Contains nil check (nil is never contained)
+    let result: bool = lua.load(r#"return table.contains({1, nil, 3}, nil)"#).eval().unwrap();
+    assert!(!result);
+
+    // Empty table contains nothing
+    let result: bool = lua.load(r#"return table.contains({}, 1)"#).eval().unwrap();
+    assert!(!result);
+
+    // Contains with string values
+    let result: bool = lua
+        .load(r#"return table.contains({"apple", "banana", "cherry"}, "banana")"#)
+        .eval()
+        .unwrap();
+    assert!(result);
+}
+
+#[test]
+fn test_is_empty() {
+    let lua = super::lua();
+
+    // Empty table is empty
+    let result: bool = lua.load(r#"return table.isEmpty({})"#).eval().unwrap();
+    assert!(result);
+
+    // Array is not empty
+    let result: bool = lua.load(r#"return table.isEmpty({1, 2, 3})"#).eval().unwrap();
+    assert!(!result);
+
+    // Dictionary is not empty
+    let result: bool = lua.load(r#"return table.isEmpty({a = 1})"#).eval().unwrap();
+    assert!(!result);
+
+    // Table with only nil values is empty (nil doesn't count as a value)
+    let result: bool = lua.load(r#"return table.isEmpty({nil, nil})"#).eval().unwrap();
+    assert!(result);
+
+    // Single element is not empty
+    let result: bool = lua.load(r#"return table.isEmpty({42})"#).eval().unwrap();
+    assert!(!result);
+}
+
+#[test]
+fn test_min_max_nan_propagates() {
+    let lua = super::lua();
+
+    // A NaN anywhere in the input must yield NaN, not an arbitrary survivor value
+    let result: bool = lua.load(r#"local r = table.max({5, 0/0, 3}); return r ~= r"#).eval().unwrap();
+    assert!(result, "max with NaN in the middle must be NaN");
+
+    let result: bool = lua.load(r#"local r = table.min({3, 0/0, 5}); return r ~= r"#).eval().unwrap();
+    assert!(result, "min with NaN in the middle must be NaN");
+
+    let result: bool = lua.load(r#"local r = table.max({0/0, 5}); return r ~= r"#).eval().unwrap();
+    assert!(result, "max with NaN first must be NaN");
+
+    let result: bool = lua.load(r#"local r = table.min({0/0}); return r ~= r"#).eval().unwrap();
+    assert!(result, "min of only NaN must be NaN");
+}
+
+#[test]
+fn test_merge_argument_validation() {
+    let lua = super::lua();
+
+    // A nil argument must error, not silently swallow the remaining arguments
+    let err = lua
+        .load(
+            r#"
+            local function maybeNil() return nil end
+            return table.merge({a = 1}, maybeNil(), {b = 2})
+            "#,
+        )
+        .exec()
+        .unwrap_err();
+    assert!(err.to_string().contains("not a table"));
+
+    // Non-table arguments must error with a clear message
+    let err = lua.load(r#"return table.merge({}, 5)"#).exec().unwrap_err();
+    assert!(err.to_string().contains("not a table"));
+
+    // Same for deepMerge
+    let err = lua.load(r#"return table.deepMerge({a = 1}, nil, {b = 2})"#).exec().unwrap_err();
+    assert!(err.to_string().contains("not a table"));
+
+    // No arguments is a valid (empty) merge
+    let result: bool = lua.load(r#"return table.isEmpty(table.merge())"#).eval().unwrap();
+    assert!(result);
+}
+
+#[test]
+fn test_merge_key_handling() {
+    let lua = super::lua();
+
+    // Non-sequence numeric keys (float, zero, negative, sparse) are preserved, not renumbered
+    let result: bool = lua
+        .load(
+            r#"
+            local m = table.merge({[1.5] = "x", [0] = "y", [-3] = "z"})
+            return m[1.5] == "x" and m[0] == "y" and m[-3] == "z" and m[1] == nil
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(result);
+
+    // Sparse numeric keys beyond the sequence stay where they are
+    let result: bool = lua
+        .load(
+            r#"
+            local m = table.merge({[1] = "a", [5] = "b"})
+            return m[1] == "a" and m[5] == "b" and m[2] == nil
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(result);
+
+    // Non-sequence numeric keys collide map-style: later table overwrites
+    let result: String = lua
+        .load(r#"return table.merge({[10] = "a"}, {[10] = "b"})[10]"#)
+        .eval()
+        .unwrap();
+    assert_eq!(result, "b");
+
+    // The sequence parts still concatenate in order
+    let result: String = lua
+        .load(r#"return utils.toJSON(table.merge({1, 2}, {3, 4}, {5}))"#)
+        .eval()
+        .unwrap();
+    assert_eq!(result, "[1,2,3,4,5]");
+}
+
+#[test]
+fn test_deep_merge_array_concat() {
+    let lua = super::lua();
+
+    // Arrays of tables concatenate just like arrays of scalars -
+    // element-wise merging only applies to non-sequence keys
+    let result: bool = lua
+        .load(
+            r#"
+            local m = table.deepMerge({{a = 1}}, {{b = 2}})
+            return #m == 2 and m[1].a == 1 and m[1].b == nil and m[2].b == 2 and m[2].a == nil
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(result);
+}
+
+#[test]
+fn test_deep_merge_no_aliasing() {
+    let lua = super::lua();
+
+    // Mutating the merge result must never touch the input tables
+    let result: i64 = lua
+        .load(
+            r#"
+            local inner = {val = 1}
+            local m = table.deepMerge({}, {x = inner})
+            m.x.val = 99
+            return inner.val
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, 1);
+
+    // Also for appended sequence elements
+    let result: i64 = lua
+        .load(
+            r#"
+            local inner = {val = 1}
+            local m = table.deepMerge({inner})
+            m[1].val = 99
+            return inner.val
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, 1);
+
+    // And for nested tables adopted deep inside
+    let result: i64 = lua
+        .load(
+            r#"
+            local deep = {leaf = 1}
+            local m = table.deepMerge({cfg = {}}, {cfg = {sub = deep}})
+            m.cfg.sub.leaf = 99
+            return deep.leaf
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, 1);
+}
+
+#[test]
+fn test_deep_merge_error_message() {
+    let lua = super::lua();
+
+    // The recursion limit error must name the actual function, not a stale one
+    let err = lua
+        .load(
+            r#"
+            local function buildDeep(depth)
+                if depth == 0 then
+                    return {val = 1}
+                end
+                return {nested = buildDeep(depth - 1)}
+            end
+            return table.deepMerge(buildDeep(101), buildDeep(101))
+            "#,
+        )
+        .exec()
+        .unwrap_err();
+    assert!(err.to_string().contains("table.deepMerge"));
+}
+
+#[test]
+fn test_ireduce() {
+    let lua = super::lua();
+
+    // Iterates in sequence order - order-sensitive reduction proves it
+    let result: String = lua
+        .load(
+            r#"
+            local t = {"a", "b", "c", "d"}
+            return table.ireduce(t, function(acc, v) return acc .. v end, "")
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, "abcd");
+
+    // Empty table returns the initial value
+    let result: i64 = lua
+        .load(r#"return table.ireduce({}, function(acc, v) return acc + v end, 42)"#)
+        .eval()
+        .unwrap();
+    assert_eq!(result, 42);
+
+    // Only the sequence part is reduced, other keys are ignored
+    let result: i64 = lua
+        .load(
+            r#"
+            local t = {1, 2, 3}
+            t.x = 100
+            return table.ireduce(t, function(acc, v) return acc + v end, 0)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, 6);
+}
+
+#[test]
+fn test_reverse() {
+    let lua = super::lua();
+
+    // Reverse array of numbers
+    let result: String = lua
+        .load(r#"return utils.toJSON(table.reverse({1, 2, 3, 4, 5}))"#)
+        .eval()
+        .unwrap();
+    assert_eq!(result, "[5,4,3,2,1]");
+
+    // Reverse array of strings
+    let result: String = lua
+        .load(r#"return utils.toJSON(table.reverse({"a", "b", "c"}))"#)
+        .eval()
+        .unwrap();
+    assert_eq!(result, r#"["c","b","a"]"#);
+
+    // Reverse empty array
+    let result: String = lua.load(r#"return utils.toJSON(table.reverse({}))"#).eval().unwrap();
+    assert_eq!(result, "{}");
+
+    // Reverse single element
+    let result: String = lua.load(r#"return utils.toJSON(table.reverse({42}))"#).eval().unwrap();
+    assert_eq!(result, "[42]");
+
+    // Original array unmodified
+    let result: String = lua
+        .load(
+            r#"
+            local t = {1, 2, 3}
+            local _ = table.reverse(t)
+            return utils.toJSON(t)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, "[1,2,3]");
+
+    // Reverse of reverse is original
+    let result: String = lua
+        .load(r#"return utils.toJSON(table.reverse(table.reverse({1, 2, 3, 4})))"#)
+        .eval()
+        .unwrap();
+    assert_eq!(result, "[1,2,3,4]");
+}
+
+#[test]
+fn test_find() {
+    let lua = super::lua();
+
+    // Find in a sequence returns the value and its key
+    let result: bool = lua
+        .load(
+            r#"
+            local v, k = table.find({10, 20, 30}, function(x) return x == 20 end)
+            return v == 20 and k == 2
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(result);
+
+    // Find in a dictionary
+    let result: bool = lua
+        .load(
+            r#"
+            local v, k = table.find({a = 1, b = 2}, function(x) return x == 2 end)
+            return v == 2 and k == "b"
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(result);
+
+    // Not found returns nil, nil
+    let result: bool = lua
+        .load(
+            r#"
+            local v, k = table.find({1, 2, 3}, function() return false end)
+            return v == nil and k == nil
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(result);
+
+    // Empty table finds nothing
+    let result: bool = lua
+        .load(
+            r#"
+            local v, k = table.find({}, function() return true end)
+            return v == nil and k == nil
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(result);
+
+    // A stored false value is findable - the key distinguishes it from "not found"
+    let result: bool = lua
+        .load(
+            r#"
+            local v, k = table.find({false}, function(x) return x == false end)
+            return v == false and k == 1
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(result);
+}
+
+#[test]
+fn test_deep_copy() {
+    let lua = super::lua();
+
+    // The copy is structurally equal to the original
+    // (key order in the JSON dumps is unspecified, compare parsed)
+    let (copy, orig): (String, String) = lua
+        .load(
+            r#"
+            local orig = {a = 1, nested = {b = 2, deeper = {c = 3}}, arr = {1, 2, 3}}
+            local copy = table.deepCopy(orig)
+            return utils.toJSON(copy), utils.toJSON(orig)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(json_eq(&copy, &orig));
+
+    // Mutating the copy at any level must not touch the original
+    let result: bool = lua
+        .load(
+            r#"
+            local orig = {a = 1, nested = {b = 2}, arr = {1, 2, 3}}
+            local copy = table.deepCopy(orig)
+            copy.a = 99
+            copy.nested.b = 99
+            copy.arr[1] = 99
+            return orig.a == 1 and orig.nested.b == 2 and orig.arr[1] == 1
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(result);
+
+    // Metatables are not copied
+    let result: bool = lua
+        .load(
+            r#"
+            local orig = setmetatable({x = 1}, {__index = function() return 42 end})
+            local copy = table.deepCopy(orig)
+            return getmetatable(copy) == nil and copy.x == 1 and copy.missing == nil
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(result);
+
+    // Recursion limit protection (also catches self-referencing tables)
+    let err = lua
+        .load(
+            r#"
+            local function buildDeep(depth)
+                if depth == 0 then
+                    return {val = 1}
+                end
+                return {nested = buildDeep(depth - 1)}
+            end
+            return table.deepCopy(buildDeep(101))
+            "#,
+        )
+        .exec()
+        .unwrap_err();
+    assert!(err.to_string().contains("recursion too deep"));
+
+    let err = lua
+        .load(
+            r#"
+            local t = {}
+            t.self = t
+            return table.deepCopy(t)
+            "#,
+        )
+        .exec()
+        .unwrap_err();
+    assert!(err.to_string().contains("recursion too deep"));
+}
+
+#[test]
+fn test_argument_type_validation() {
+    let lua = super::lua();
+
+    // Every table.* function must reject wrong argument types with a clear message
+    let cases: &[(&str, &str)] = &[
+        ("table.filter(5, function() end)", "not a table"),
+        ("table.filter({}, 5)", "not a function"),
+        ("table.ifilter(nil, function() end)", "not a table"),
+        ("table.ifilter({}, nil)", "not a function"),
+        ("table.map(5, function() end)", "not a table"),
+        ("table.map({}, 'x')", "not a function"),
+        ("table.filterMap(5, function() end)", "not a table"),
+        ("table.filterMap({}, 5)", "not a function"),
+        ("table.ifilterMap(5, function() end)", "not a table"),
+        ("table.ifilterMap({}, 5)", "not a function"),
+        ("table.reduce(5, function() end, 0)", "not a table"),
+        ("table.reduce({}, 5, 0)", "not a function"),
+        ("table.ireduce(5, function() end, 0)", "not a table"),
+        ("table.ireduce({}, 5, 0)", "not a function"),
+        ("table.min(5)", "not a table"),
+        ("table.max('foo')", "not a table"),
+        ("table.mean(nil)", "not a table"),
+        ("table.sum(5)", "not a table"),
+        ("table.keys(5)", "not a table"),
+        ("table.values(5)", "not a table"),
+        ("table.contains(5, 1)", "not a table"),
+        ("table.find(5, function() end)", "not a table"),
+        ("table.find({}, 5)", "not a function"),
+        ("table.isEmpty(5)", "not a table"),
+        ("table.reverse(5)", "not a table"),
+        ("table.deepCopy(5)", "not a table"),
+        ("table.deepCopy(nil)", "not a table"),
+    ];
+
+    for (code, expected) in cases {
+        let err = lua.load(format!("return {code}")).exec().unwrap_err();
+        let msg = err.to_string();
+        assert!(
+            msg.contains(expected),
+            "case `{code}` should error with `{expected}`, got: {msg}"
+        );
+    }
+}
+
+#[test]
+fn test_readonly_arg_validation() {
+    let lua = super::lua();
+
+    // Non-table argument must error with the same message style as the other table functions
+    let err = lua.load(r#"return table.readonly(5)"#).exec().unwrap_err();
+    assert!(err.to_string().contains("not a table"), "got: {err}");
+
+    let err = lua.load(r#"return table.readonly(nil)"#).exec().unwrap_err();
+    assert!(err.to_string().contains("not a table"), "got: {err}");
+
+    // A non-string name must error instead of being silently coerced
+    let err = lua.load(r#"return table.readonly({}, 5)"#).exec().unwrap_err();
+    assert!(err.to_string().contains("not a string"), "got: {err}");
+}
diff --git a/src/lua_tests/utils_tests.rs b/src/lua_tests/utils_tests.rs
new file mode 100644
index 0000000..c4f0b09
--- /dev/null
+++ b/src/lua_tests/utils_tests.rs
@@ -0,0 +1,813 @@
+//! Tests for the `utils` global: NULL sentinel, isNull, toJSON/fromJSON, dump
+//! (Rust side) and try, tryn (Lua side, lua/stdlib/utils.lua).
+//!
+//! Ported from flowbox-rt fb_lua utils_tests. `utils.dump` is the flowbox Rust
+//! implementation (src/stdlib/lua_dump.rs), so the dump tests match flowbox's.
+
+use super::json_eq;
+
+#[test]
+fn test_dump() {
+    let lua = super::lua();
+
+    let dump = |code: &str| -> String {
+        lua.load(format!("return utils.dump({})", code))
+            .eval::<String>()
+            .unwrap()
+    };
+
+    // nil
+    assert_eq!(dump("nil"), "nil");
+
+    // booleans
+    assert_eq!(dump("true"), "true");
+    assert_eq!(dump("false"), "false");
+
+    // integers
+    assert_eq!(dump("1"), "1");
+    assert_eq!(dump("0"), "0");
+    assert_eq!(dump("-42"), "-42");
+
+    // floats - whole numbers show .0 (Lua 5.4 tostring)
+    assert_eq!(dump("1.0"), "1.0");
+    assert_eq!(dump("0.0"), "0.0");
+    assert_eq!(dump("-5.0"), "-5.0");
+
+    // floats - with fractional part
+    assert_eq!(dump("1.5"), "1.5");
+    assert_eq!(dump("-3.14159"), "-3.14159");
+    assert_eq!(dump("0.001"), "0.001");
+
+    // strings are quoted and escaped JSON-style
+    assert_eq!(dump("'hello'"), "\"hello\"");
+    assert_eq!(dump("''"), "\"\""); // empty
+    assert_eq!(dump("'with spaces'"), "\"with spaces\"");
+    assert_eq!(dump("'special\\nchars\\ttab'"), "\"special\\nchars\\ttab\"");
+
+    // empty table
+    assert_eq!(dump("{}"), "{}");
+
+    // simple table with string key
+    assert_eq!(dump("{foo=1}"), "{foo=1}");
+    assert_eq!(dump("{_foo=1}"), "{_foo=1}");
+    assert_eq!(dump("{_1=1}"), "{_1=1}");
+    // a string key that does not look like an identifier is bracketed and quoted
+    assert_eq!(dump("{[\"1\"]=1}"), "{[\"1\"]=1}");
+
+    // nested table
+    assert_eq!(dump("{foo={bar=1}}"), "{foo={bar=1}}");
+
+    // array-style table (numeric keys)
+    assert_eq!(dump("{10, 20, 30}"), "{10, 20, 30}");
+
+    // mixed keys - order may vary, so check by substrings
+    let dumped = dump("{foo=1, [999]='a'}");
+    assert!(dumped.contains("foo=1"), "got: {dumped}");
+    assert!(dumped.contains("[999]=\"a\""), "got: {dumped}");
+
+    // a table with both an array part and hash keys dumps both
+    assert_eq!(dump("{10, 20, foo='hash'}"), "{10, 20, foo=\"hash\"}");
+
+    // function
+    assert_eq!(dump("function() end"), "<Function>");
+}
+
+#[test]
+fn test_dump_deep_nesting() {
+    let lua = super::lua();
+
+    // Recursion limit: tables at depth > 20 are rendered as <TRUNCATED>
+    // Build a table nested 25 levels deep - truncation happens at depth 21
+    let deep_result: String = lua
+        .load(
+            r#"
+            local t = {val="leaf"}
+            for i = 1, 25 do
+                t = {nested=t}
+            end
+            return utils.dump(t)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    // 20 levels of {nested=, then the innermost table's value truncated at depth 21
+    let expected = format!("{}{{nested=<TRUNCATED>}}{}", "{nested=".repeat(20), "}".repeat(20));
+    assert_eq!(deep_result, expected);
+
+    // A table just within the limit still dumps fully
+    let shallow_result: String = lua
+        .load(
+            r#"
+            local t = {val="leaf"}
+            for i = 1, 5 do
+                t = {nested=t}
+            end
+            return utils.dump(t)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    let expected = format!("{}{{val=\"leaf\"}}{}", "{nested=".repeat(5), "}".repeat(5));
+    assert_eq!(shallow_result, expected);
+}
+
+#[test]
+fn test_dump_circular() {
+    let lua = super::lua();
+
+    // There is no cycle detection; the depth limit terminates the recursion,
+    // so a self-referencing table dumps 21 levels and then truncates
+    let result: String = lua
+        .load(
+            r#"
+            local t = {}
+            t.self = t
+            return utils.dump(t)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    let expected = format!("{}<TRUNCATED>{}", "{self=".repeat(21), "}".repeat(21));
+    assert_eq!(result, expected);
+
+    // The same table appearing twice as a sibling dumps twice
+    let result: String = lua
+        .load(
+            r#"
+            local shared = {x = 1}
+            return utils.dump({shared, shared})
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, "{{x=1}, {x=1}}");
+}
+
+#[test]
+fn test_to_json() {
+    let lua = super::lua();
+
+    // Primitives
+    let result: String = lua.load(r#"return utils.toJSON(nil)"#).eval().unwrap();
+    assert_eq!(result, "null");
+
+    let result: String = lua.load(r#"return utils.toJSON(true)"#).eval().unwrap();
+    assert_eq!(result, "true");
+
+    let result: String = lua.load(r#"return utils.toJSON(false)"#).eval().unwrap();
+    assert_eq!(result, "false");
+
+    let result: String = lua.load(r#"return utils.toJSON(42)"#).eval().unwrap();
+    assert_eq!(result, "42");
+
+    let result: String = lua.load(r#"return utils.toJSON(3.14)"#).eval().unwrap();
+    assert_eq!(result, "3.14");
+
+    let result: String = lua.load(r#"return utils.toJSON("hello")"#).eval().unwrap();
+    assert_eq!(result, "\"hello\"");
+
+    // Empty table serializes as an empty object
+    let result: String = lua.load(r#"return utils.toJSON({})"#).eval().unwrap();
+    assert_eq!(result, "{}");
+
+    // Array-style table
+    let result: String = lua.load(r#"return utils.toJSON({1, 2, 3})"#).eval().unwrap();
+    assert_eq!(result, "[1,2,3]");
+
+    // Object-style table
+    let result: String = lua.load(r#"return utils.toJSON({a=1})"#).eval().unwrap();
+    assert_eq!(result, "{\"a\":1}");
+
+    // Nested structure
+    let result: String = lua
+        .load(r#"return utils.toJSON({nested={value=42}})"#)
+        .eval()
+        .unwrap();
+    assert_eq!(result, "{\"nested\":{\"value\":42}}");
+}
+
+#[test]
+fn test_to_json_mixed_and_integer_keys() {
+    let lua = super::lua();
+
+    // A table with both a sequence part and hash keys is serialized as an
+    // object; integer keys become string keys
+    let result: String = lua
+        .load(r#"return utils.toJSON({1, 2, x = 3})"#)
+        .eval()
+        .unwrap();
+    assert!(json_eq(&result, r#"{"1":1,"2":2,"x":3}"#), "got: {result}");
+
+    // Non-sequential integer keys become string object keys
+    let result: String = lua
+        .load(r#"return utils.toJSON({a = 1, [10] = "x"})"#)
+        .eval()
+        .unwrap();
+    assert!(json_eq(&result, r#"{"a":1,"10":"x"}"#), "got: {result}");
+}
+
+#[test]
+fn test_to_json_pretty() {
+    let lua = super::lua();
+
+    // Second argument enables pretty-printing
+    let result: String = lua.load(r#"return utils.toJSON({a=1}, true)"#).eval().unwrap();
+    assert_eq!(result, "{\n  \"a\": 1\n}");
+
+    // Explicit false behaves like the default compact output
+    let result: String = lua.load(r#"return utils.toJSON({a=1}, false)"#).eval().unwrap();
+    assert_eq!(result, "{\"a\":1}");
+}
+
+#[test]
+fn test_to_json_unserializable_errors() {
+    let lua = super::lua();
+
+    // Unserializable values must raise an error instead of silently returning "null"
+    let err = lua.load(r#"return utils.toJSON(function() end)"#).exec().unwrap_err();
+    assert!(err.to_string().contains("toJSON"), "got: {err}");
+    assert!(err.to_string().contains("function"), "got: {err}");
+
+    // A single bad value must not silently discard the whole structure
+    let err = lua
+        .load(r#"return utils.toJSON({x = 1, f = function() end})"#)
+        .exec()
+        .unwrap_err();
+    assert!(err.to_string().contains("toJSON"), "got: {err}");
+
+    // Self-referencing tables cannot be serialized (caught by the depth limit)
+    let err = lua
+        .load(
+            r#"
+            local t = {}
+            t.self = t
+            return utils.toJSON(t)
+            "#,
+        )
+        .exec()
+        .unwrap_err();
+    assert!(err.to_string().contains("toJSON"), "got: {err}");
+    assert!(err.to_string().contains("nesting too deep"), "got: {err}");
+
+    // NaN and Infinity have no JSON representation
+    let err = lua.load(r#"return utils.toJSON(0/0)"#).exec().unwrap_err();
+    assert!(err.to_string().contains("NaN"), "got: {err}");
+
+    let err = lua.load(r#"return utils.toJSON(math.huge)"#).exec().unwrap_err();
+    assert!(err.to_string().contains("Infinity"), "got: {err}");
+
+    // Only string and integer keys can become JSON object keys
+    let err = lua.load(r#"return utils.toJSON({[true] = 1})"#).exec().unwrap_err();
+    assert!(err.to_string().contains("object key"), "got: {err}");
+
+    let err = lua.load(r#"return utils.toJSON({[1.5] = 1})"#).exec().unwrap_err();
+    assert!(err.to_string().contains("object key"), "got: {err}");
+
+    // An integer key that stringifies onto an existing string key must error
+    // rather than silently dropping one of the two values.
+    let err = lua
+        .load(r#"return utils.toJSON({[1] = "int", ["1"] = "str"})"#)
+        .exec()
+        .unwrap_err();
+    assert!(err.to_string().contains("duplicate object key"), "got: {err}");
+
+    // A non-UTF-8 string value gets a clear prefixed error, not mlua's bare
+    // "error converting Lua string to &str".
+    let err = lua.load(r#"return utils.toJSON("\255bad")"#).exec().unwrap_err();
+    assert!(err.to_string().contains("utils.toJSON"), "got: {err}");
+    assert!(err.to_string().contains("UTF-8"), "got: {err}");
+}
+
+#[test]
+fn test_null_sentinel() {
+    let lua = super::lua();
+
+    // utils.NULL exists and is distinct from nil
+    let result: bool = lua.load(r#"return utils.NULL ~= nil"#).eval().unwrap();
+    assert!(result);
+
+    // isNull identifies the sentinel and nothing else
+    let result: bool = lua.load(r#"return utils.isNull(utils.NULL)"#).eval().unwrap();
+    assert!(result);
+
+    let result: bool = lua
+        .load(
+            r#"
+            return utils.isNull(nil) or utils.isNull(0) or utils.isNull("")
+                or utils.isNull({}) or utils.isNull(false)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(!result);
+
+    // JSON null deserializes to the sentinel - consistently at any nesting level
+    let result: bool = lua.load(r#"return utils.isNull(utils.fromJSON("null"))"#).eval().unwrap();
+    assert!(result);
+
+    let result: bool = lua
+        .load(
+            r#"
+            local obj = utils.fromJSON('{"a": null, "b": 1}')
+            return utils.isNull(obj.a) and obj.a ~= nil and obj.b == 1
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(result);
+
+    // Nulls in arrays preserve the array length
+    let result: bool = lua
+        .load(
+            r#"
+            local arr = utils.fromJSON('[1, null, 3]')
+            return #arr == 3 and utils.isNull(arr[2]) and arr[1] == 1 and arr[3] == 3
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(result);
+
+    // The sentinel serializes back to JSON null
+    let result: String = lua.load(r#"return utils.toJSON(utils.NULL)"#).eval().unwrap();
+    assert_eq!(result, "null");
+
+    let result: String = lua.load(r#"return utils.toJSON({a = utils.NULL})"#).eval().unwrap();
+    assert_eq!(result, "{\"a\":null}");
+
+    // dump renders the sentinel as NULL, bare and inside tables
+    // (other light userdata dumps as <LightUserData>)
+    let result: String = lua.load(r#"return utils.dump(utils.NULL)"#).eval().unwrap();
+    assert_eq!(result, "NULL");
+
+    let result: String = lua.load(r#"return utils.dump({a = utils.NULL})"#).eval().unwrap();
+    assert_eq!(result, "{a=NULL}");
+
+    let result: String = lua.load(r#"return utils.dump({1, utils.NULL, 3})"#).eval().unwrap();
+    assert_eq!(result, "{1, NULL, 3}");
+}
+
+/// utils.NULL is mlua's own null sentinel (Value::NULL, a null-pointer light
+/// userdata), so nulls interoperate with mlua's serde layer in both directions.
+#[test]
+fn test_null_sentinel_matches_mlua() {
+    use mlua::LuaSerdeExt;
+
+    let lua = super::lua();
+
+    let null_val: mlua::Value = lua.load(r#"return utils.NULL"#).eval().unwrap();
+    assert_eq!(null_val, mlua::Value::NULL);
+
+    // a null produced by mlua (lua.null()) is recognized by utils.isNull
+    let is_null: bool = lua
+        .globals()
+        .get::<mlua::Table>("utils")
+        .unwrap()
+        .get::<mlua::Function>("isNull")
+        .unwrap()
+        .call(lua.null())
+        .unwrap();
+    assert!(is_null);
+}
+
+#[test]
+fn test_utils_table_extensible() {
+    let lua = super::lua();
+
+    // utils is a plain global table just like math and table - scripts can extend it
+    let result: i64 = lua
+        .load(
+            r#"
+            utils.myHelper = function() return 41 + 1 end
+            return utils.myHelper()
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, 42);
+
+    // and the built-in functions are of course still there
+    let result: bool = lua.load(r#"return type(utils.try) == "function""#).eval().unwrap();
+    assert!(result);
+}
+
+#[test]
+fn test_try_tryn_arg_validation() {
+    let lua = super::lua();
+
+    // The callback must be a function, rejected with a clear message
+    let err = lua.load(r#"return utils.try(5)"#).exec().unwrap_err();
+    assert!(err.to_string().contains("not a function"), "got: {err}");
+
+    let err = lua.load(r#"return utils.try(nil)"#).exec().unwrap_err();
+    assert!(err.to_string().contains("not a function"), "got: {err}");
+
+    let err = lua.load(r#"return utils.tryn(2, 5)"#).exec().unwrap_err();
+    assert!(err.to_string().contains("not a function"), "got: {err}");
+
+    // expectedCount must be a non-negative integer
+    let err = lua.load(r#"return utils.tryn(2.5, function() end)"#).exec().unwrap_err();
+    assert!(err.to_string().contains("integer"), "got: {err}");
+
+    assert!(lua.load(r#"return utils.tryn(-1, function() end)"#).exec().is_err());
+}
+
+#[test]
+fn test_try_error_values() {
+    let lua = super::lua();
+
+    // A thrown table is passed through as-is (pcall semantics), so scripts can
+    // attach structured data to errors
+    let result: bool = lua
+        .load(
+            r#"
+            local v, err = utils.try(function() error({code = 42}) end)
+            return v == nil and type(err) == "table" and err.code == 42
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(result);
+
+    // A nil error value still yields a non-nil err, so `if err` always detects failure
+    let result: bool = lua
+        .load(
+            r#"
+            local v, err = utils.try(function() error() end)
+            return err ~= nil
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(result);
+
+    let result: bool = lua
+        .load(
+            r#"
+            local a, err = utils.tryn(1, function() error() end)
+            return err ~= nil
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(result);
+}
+
+#[test]
+fn test_tryn_return_counts() {
+    let lua = super::lua();
+
+    // tryn returns exactly expectedCount + 1 values (the last one is the error slot),
+    // both on success and on failure
+    let result: i64 = lua
+        .load(r#"return select('#', utils.tryn(2, function() return 1 end))"#)
+        .eval()
+        .unwrap();
+    assert_eq!(result, 3);
+
+    let result: i64 = lua
+        .load(r#"return select('#', utils.tryn(2, function() error("x") end))"#)
+        .eval()
+        .unwrap();
+    assert_eq!(result, 3);
+
+    // expectedCount = 0 gives just the error slot
+    let result: bool = lua
+        .load(
+            r#"
+            local err = utils.tryn(0, function() return 1, 2 end)
+            return err == nil and select('#', utils.tryn(0, function() end)) == 1
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(result);
+}
+
+#[test]
+fn test_tryn_count_cap() {
+    let lua = super::lua();
+
+    // Excessive expected_count must error early instead of allocating huge buffers
+    let err = lua
+        .load(r#"return utils.tryn(1000000, function() return 1 end)"#)
+        .exec()
+        .unwrap_err();
+    assert!(err.to_string().contains("at most"), "got: {err}");
+
+    let err = lua
+        .load(r#"return utils.tryn(65, function() return 1 end)"#)
+        .exec()
+        .unwrap_err();
+    assert!(err.to_string().contains("at most"), "got: {err}");
+
+    // The maximum allowed count still works
+    let result: i64 = lua
+        .load(
+            r#"
+            local r = {utils.tryn(64, function() return 42 end)}
+            return r[1]
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, 42);
+}
+
+#[test]
+fn test_from_json() {
+    let lua = super::lua();
+
+    // Primitives - JSON null becomes the utils.NULL sentinel, not nil
+    lua.load(r#"assert(utils.isNull(utils.fromJSON("null")))"#).exec().unwrap();
+
+    let result: bool = lua.load(r#"return utils.fromJSON("true")"#).eval().unwrap();
+    assert!(result);
+
+    let result: bool = lua.load(r#"return utils.fromJSON("false")"#).eval().unwrap();
+    assert!(!result);
+
+    let result: i64 = lua.load(r#"return utils.fromJSON("42")"#).eval().unwrap();
+    assert_eq!(result, 42);
+
+    // Whole JSON numbers arrive as Lua integers, fractional ones as floats
+    let result: bool = lua
+        .load(r#"return math.type(utils.fromJSON("42")) == "integer""#)
+        .eval()
+        .unwrap();
+    assert!(result);
+
+    let result: f64 = lua.load(r#"return utils.fromJSON("3.14")"#).eval().unwrap();
+    assert!((result - 3.14).abs() < 0.001);
+
+    let result: bool = lua
+        .load(r#"return math.type(utils.fromJSON("3.14")) == "float""#)
+        .eval()
+        .unwrap();
+    assert!(result);
+
+    let result: String = lua.load(r#"return utils.fromJSON('"hello"')"#).eval().unwrap();
+    assert_eq!(result, "hello");
+
+    // Array
+    let result: i64 = lua
+        .load(
+            r#"
+            local arr = utils.fromJSON("[1, 2, 3]")
+            return arr[1] + arr[2] + arr[3]
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, 6);
+
+    // Object
+    let result: i64 = lua
+        .load(
+            r#"
+            local obj = utils.fromJSON('{"a": 10, "b": 20}')
+            return obj.a + obj.b
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, 30);
+
+    // Nested structure
+    let result: i64 = lua
+        .load(
+            r#"
+            local data = utils.fromJSON('{"nested": {"value": 42}}')
+            return data.nested.value
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, 42);
+
+    // Invalid JSON should error, and the message names the function
+    let err = lua.load(r#"return utils.fromJSON("not valid json")"#).exec().unwrap_err();
+    assert!(err.to_string().contains("fromJSON"), "got: {err}");
+}
+
+#[test]
+fn test_json_roundtrip() {
+    let lua = super::lua();
+
+    // Round-trip test: Lua -> JSON -> Lua
+    let result: i64 = lua
+        .load(
+            r#"
+            local original = {x = 10, y = 20, items = {1, 2, 3}}
+            local json = utils.toJSON(original)
+            local restored = utils.fromJSON(json)
+            return restored.x + restored.y + restored.items[1]
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, 31); // 10 + 20 + 1
+
+    // NULL survives a Lua -> JSON -> Lua round trip
+    let result: bool = lua
+        .load(
+            r#"
+            local restored = utils.fromJSON(utils.toJSON({a = utils.NULL}))
+            return utils.isNull(restored.a)
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(result);
+}
+
+#[test]
+fn test_try() {
+    let lua = super::lua();
+
+    // Success case: returns value, nil error
+    let (value, has_error): (i64, bool) = lua
+        .load(
+            r#"
+            local val, err = utils.try(function() return 42 end)
+            return val, err ~= nil
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(value, 42);
+    assert!(!has_error);
+
+    // Error case: returns nil value, error
+    let (is_nil, has_error): (bool, bool) = lua
+        .load(
+            r#"
+            local val, err = utils.try(function() error("boom") end)
+            return val == nil, err ~= nil
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(is_nil);
+    assert!(has_error);
+
+    // Error message is preserved
+    let contains_boom: bool = lua
+        .load(
+            r#"
+            local val, err = utils.try(function() error("boom") end)
+            return tostring(err):find("boom") ~= nil
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(contains_boom);
+}
+
+#[test]
+fn test_try_shorthand() {
+    let lua = super::lua();
+
+    // pcall-style shorthand: the function and its arguments, no closure needed
+    let (value, has_error): (String, bool) = lua
+        .load(
+            r#"
+            local val, err = utils.try(string.rep, "ab", 3)
+            return val, err ~= nil
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(value, "ababab");
+    assert!(!has_error);
+
+    // Errors thrown by the called function are captured the same way as with a closure
+    let captured: bool = lua
+        .load(
+            r#"
+            local val, err = utils.try(error, "boom")
+            return val == nil and tostring(err):find("boom") ~= nil
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(captured);
+
+    // nil arguments are forwarded with the argument count preserved (pcall semantics)
+    let result: i64 = lua
+        .load(
+            r#"
+            local function countArgs(...) return select('#', ...) end
+            local n = utils.try(countArgs, nil, nil, nil)
+            return n
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, 3);
+}
+
+#[test]
+fn test_tryn() {
+    let lua = super::lua();
+
+    // Success case with multiple return values
+    let (a, b, c, has_error): (i64, i64, i64, bool) = lua
+        .load(
+            r#"
+            local a, b, c, err = utils.tryn(3, function() return 1, 2, 3 end)
+            return a, b, c, err ~= nil
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!((a, b, c), (1, 2, 3));
+    assert!(!has_error);
+
+    // Error case: all values are nil, error is present
+    let (all_nil, has_error): (bool, bool) = lua
+        .load(
+            r#"
+            local a, b, c, err = utils.tryn(3, function() error("fail") end)
+            return a == nil and b == nil and c == nil, err ~= nil
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(all_nil);
+    assert!(has_error);
+
+    // Fewer return values than expected: pads with nil
+    let (a, b_nil, c_nil, has_error): (i64, bool, bool, bool) = lua
+        .load(
+            r#"
+            local a, b, c, err = utils.tryn(3, function() return 100 end)
+            return a, b == nil, c == nil, err ~= nil
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(a, 100);
+    assert!(b_nil);
+    assert!(c_nil);
+    assert!(!has_error);
+
+    // More return values than expected: truncates
+    let (a, b, has_error): (i64, i64, bool) = lua
+        .load(
+            r#"
+            local a, b, err = utils.tryn(2, function() return 1, 2, 3, 4, 5 end)
+            return a, b, err ~= nil
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!((a, b), (1, 2));
+    assert!(!has_error);
+}
+
+#[test]
+fn test_tryn_shorthand() {
+    let lua = super::lua();
+
+    // pcall-style shorthand: arguments after the callback are passed to it
+    let (q, r, has_error): (i64, i64, bool) = lua
+        .load(
+            r#"
+            local function divmod(a, b) return a // b, a % b end
+            local q, r, err = utils.tryn(2, divmod, 17, 5)
+            return q, r, err ~= nil
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!((q, r), (3, 2));
+    assert!(!has_error);
+
+    // Error case: arguments are passed, the error lands in the last slot
+    let (all_nil, captured): (bool, bool) = lua
+        .load(
+            r#"
+            local function fail(msg) error("failed: " .. msg) end
+            local a, b, err = utils.tryn(2, fail, "badly")
+            return a == nil and b == nil, tostring(err):find("failed: badly") ~= nil
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert!(all_nil);
+    assert!(captured);
+
+    // nil arguments are forwarded with the argument count preserved (pcall semantics)
+    let result: i64 = lua
+        .load(
+            r#"
+            local function countArgs(...) return select('#', ...) end
+            local n, err = utils.tryn(1, countArgs, nil, 5, nil)
+            return n
+            "#,
+        )
+        .eval()
+        .unwrap();
+    assert_eq!(result, 3);
+}
diff --git a/src/main.rs b/src/main.rs
index 3810a2c..bf85457 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -2,6 +2,11 @@ use std::path::PathBuf;
 
 use clap::Parser;
 
+// Lua source embedded in test strings (e.g. `math.round(3.1415, 2)`) trips
+// clippy's approx_constant lint, which mistakes the literals for `PI`.
+#[cfg(test)]
+#[allow(clippy::approx_constant)]
+mod lua_tests;
 mod repl;
 mod sandbox;
 mod stdlib;
@@ -16,9 +21,18 @@ struct Args {
 }
 
 #[tokio::main]
-async fn main() -> Result<(), Box<dyn std::error::Error>> {
+async fn main() {
     env_logger::Builder::from_env(env_logger::Env::default().default_filter_or("warn")).init();
 
+    if let Err(err) = run().await {
+        // Display (not Debug) so a Lua error's traceback and multi-line messages
+        // read as intended instead of as one escaped line.
+        eprintln!("{err}");
+        std::process::exit(1);
+    }
+}
+
+async fn run() -> Result<(), Box<dyn std::error::Error>> {
     let args = Args::parse();
 
     let lua = sandbox::create_sandboxed_lua()?;
@@ -27,15 +41,23 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         return repl::run(&lua).await;
     };
 
-    let source = tokio::fs::read_to_string(&filepath).await?;
+    // Read as bytes, not a UTF-8 String: Lua source (and its string literals) are
+    // byte strings, and stock Lua runs files that aren't valid UTF-8.
+    let source = tokio::fs::read(&filepath)
+        .await
+        .map_err(|e| format!("a: cannot read {}: {e}", filepath.display()))?;
+
+    // Strip a leading UTF-8 BOM, as stock Lua does, so a BOM before a shebang
+    // (common from Windows editors) doesn't reach the lexer.
+    let source = source.strip_prefix(b"\xEF\xBB\xBF").unwrap_or(&source);
 
-    // Skip a leading shebang line like stock Lua's luaL_loadfilex does (it
-    // skips any first line starting with '#'). The newline is kept so error
+    // Skip a leading shebang line, if present. The newline is kept so error
     // messages still report correct line numbers.
-    let chunk = if source.starts_with('#') {
-        &source[source.find('\n').unwrap_or(source.len())..]
+    let chunk: &[u8] = if source.first() == Some(&b'#') {
+        let nl = source.iter().position(|&b| b == b'\n').unwrap_or(source.len());
+        &source[nl..]
     } else {
-        source.as_str()
+        source
     };
 
     lua.load(chunk)
diff --git a/src/repl.rs b/src/repl.rs
index 757e1de..2842b35 100644
--- a/src/repl.rs
+++ b/src/repl.rs
@@ -1,16 +1,14 @@
 //! Interactive read-eval-print loop.
 //!
-//! Started when `a` is run with no script path. Each line is compiled and run in
-//! the same sandboxed Lua state used for scripts, so the full stdlib (including
-//! the async http/sqlite/os.sleep calls) is available. Evaluation uses the async
-//! executor, matching how files are run.
+//! Each line is compiled and run in exactly the same way scripts are run, 
+//! keeping the Lua state between lines.
 
 use mlua::prelude::{LuaFunction, LuaMultiValue, LuaTable};
 use mlua::Lua;
 use rustyline::error::ReadlineError;
 use rustyline::DefaultEditor;
 
-const PROMPT: &str = "a> ";
+const PROMPT: &str = ">>> ";
 const CONTINUATION_PROMPT: &str = "..> ";
 
 /// Outcome of trying to compile a piece of REPL input.
@@ -86,6 +84,9 @@ pub(crate) async fn run(lua: &Lua) -> Result<(), Box<dyn std::error::Error>> {
 
     // Accumulated lines of an as-yet-incomplete statement.
     let mut buffer = String::new();
+    // Guards against an unbroken stream of read errors spinning forever (e.g. a
+    // reader that keeps failing without ever reaching EOF).
+    let mut consecutive_errors = 0u32;
 
     loop {
         let prompt = if buffer.is_empty() {
@@ -96,6 +97,7 @@ pub(crate) async fn run(lua: &Lua) -> Result<(), Box<dyn std::error::Error>> {
 
         match editor.readline(prompt) {
             Ok(line) => {
+                consecutive_errors = 0;
                 if buffer.is_empty() {
                     buffer = line;
                 } else {
@@ -127,12 +129,21 @@ pub(crate) async fn run(lua: &Lua) -> Result<(), Box<dyn std::error::Error>> {
             // Ctrl-C: abandon the current input and start fresh.
             Err(ReadlineError::Interrupted) => {
                 buffer.clear();
+                consecutive_errors = 0;
             }
             // Ctrl-D (on an empty line) or end of piped input: quit.
             Err(ReadlineError::Eof) => break,
+            // Any other read error (e.g. a non-UTF-8 input line) is reported but
+            // does not end the session — a stray pasted byte shouldn't kill the
+            // REPL. Bail only if errors keep coming with no successful read in
+            // between, so a permanently broken stream can't spin forever.
             Err(err) => {
                 eprintln!("{err}");
-                break;
+                buffer.clear();
+                consecutive_errors += 1;
+                if consecutive_errors >= 100 {
+                    break;
+                }
             }
         }
     }
diff --git a/src/stdlib/http.rs b/src/stdlib/http.rs
index 6aba9ba..eb68065 100644
--- a/src/stdlib/http.rs
+++ b/src/stdlib/http.rs
@@ -54,13 +54,18 @@ impl CookieJar {
             return;
         }
 
-        let mut domain = host.to_ascii_lowercase();
+        let request_host = host.to_ascii_lowercase();
+        let mut domain = request_host.clone();
         for seg in segments {
             if let Some((k, v)) = seg.split_once('=')
                 && k.trim().eq_ignore_ascii_case("domain")
             {
                 let d = v.trim().trim_start_matches('.').to_ascii_lowercase();
-                if !d.is_empty() {
+                // Only accept a Domain the request host actually belongs to
+                // (exact match or a subdomain). Otherwise a response could plant
+                // a cookie scoped to an unrelated domain ("cookie tossing"); such
+                // an attribute is ignored and the cookie stays host-scoped.
+                if !d.is_empty() && (request_host == d || request_host.ends_with(&format!(".{d}"))) {
                     domain = d;
                 }
             }
@@ -141,6 +146,17 @@ fn form_urlencode(pairs: &[(String, String)]) -> String {
 
 const MAX_REDIRECTS: u32 = 10;
 
+/// The origin of a URL: (scheme, host, effective port). Two URLs share an origin
+/// when all three match — the boundary across which credentials and secret
+/// headers must not be replayed on a redirect.
+fn origin_of(u: &reqwest::Url) -> (String, Option<String>, Option<u16>) {
+    (
+        u.scheme().to_ascii_lowercase(),
+        u.host_str().map(|h| h.to_ascii_lowercase()),
+        u.port_or_known_default(),
+    )
+}
+
 /// Shared by the stateless `http.request` and a session's `:request`. When `jar`
 /// is `Some`, the matching jar cookies are sent and any `Set-Cookie` responses
 /// are stored back.
@@ -228,39 +244,63 @@ async fn execute_request(
         }
     }
 
+    // Did the caller supply their own Content-Type? If so it wins over the one a
+    // json/form body would otherwise imply (no silent override, no duplicate).
+    let has_user_content_type = custom_headers
+        .iter()
+        .any(|(k, _)| k.eq_ignore_ascii_case("content-type"));
+
     let is_digest = matches!(auth.as_ref(), Some((true, _, _)));
     let mut digest_header: Option<String> = None;
     let mut digest_tried = false;
 
     let mut url = url;
     let mut redirects_left = MAX_REDIRECTS;
+    // Origin (scheme, host, port) of the ORIGINAL request. Once a redirect
+    // leaves this origin we stop attaching credentials, custom headers, and
+    // per-request cookies, mirroring what reqwest's own redirect policy does:
+    // a redirect to an attacker-controlled host must not receive the caller's
+    // Authorization, Cookie, or secret headers.
+    let origin = reqwest::Url::parse(&url).ok().map(|u| origin_of(&u));
 
     let resp = loop {
         // Host used for cookie matching and as the Set-Cookie domain fallback;
         // recomputed each hop since a redirect may cross hosts.
-        let host = reqwest::Url::parse(&url)
-            .ok()
+        let parsed = reqwest::Url::parse(&url).ok();
+        let host = parsed
+            .as_ref()
             .and_then(|u| u.host_str().map(|h| h.to_ascii_lowercase()));
+        // Are we still on the origin the request was addressed to?
+        let same_origin = match (origin.as_ref(), parsed.as_ref()) {
+            (Some(o), Some(u)) => *o == origin_of(u),
+            _ => false,
+        };
 
         let mut req = client.request(method.clone(), &url);
 
         if let Some(t) = timeout {
             req = req.timeout(t);
         }
-        for (k, v) in &custom_headers {
-            req = req.header(k, v);
+        // Custom headers carry only while on the original origin.
+        if same_origin {
+            for (k, v) in &custom_headers {
+                req = req.header(k, v);
+            }
         }
 
-        // Cookie header: jar cookies for this host, then per-request cookies
-        // which override on name collision.
+        // Cookie header: jar cookies for this host (the jar is domain-scoped, so
+        // this is always safe), then per-request cookies which override on name
+        // collision — but the explicit per-request cookies stay on-origin only.
         let mut cookie_map: HashMap<String, String> = HashMap::new();
         if let (Some(jar), Some(host)) = (jar.as_ref(), host.as_ref()) {
-            for (n, v) in jar.lock().unwrap().cookies_for(host) {
+            for (n, v) in jar.lock().unwrap_or_else(|e| e.into_inner()).cookies_for(host) {
                 cookie_map.insert(n, v);
             }
         }
-        for (k, v) in &opts_cookies {
-            cookie_map.insert(k.clone(), v.clone());
+        if same_origin {
+            for (k, v) in &opts_cookies {
+                cookie_map.insert(k.clone(), v.clone());
+            }
         }
         if !cookie_map.is_empty() {
             let header = cookie_map
@@ -272,15 +312,23 @@ async fn execute_request(
         }
 
         if let Some((bytes, ct)) = body.as_ref() {
-            if let Some(ct) = ct {
+            // Apply the body's implied Content-Type only when the caller didn't
+            // set their own (and theirs is still in effect, i.e. same origin).
+            if let Some(ct) = ct
+                && !(same_origin && has_user_content_type)
+            {
                 req = req.header(reqwest::header::CONTENT_TYPE, *ct);
             }
             req = req.body(bytes.clone());
         }
 
-        // Auth. Basic goes out on every hop; digest's Authorization is set only
-        // after the 401 challenge below has been answered (digest_header).
-        if let Some((digest, username, password)) = auth.as_ref() {
+        // Auth. Basic goes out on each hop; digest's Authorization is set only
+        // after the 401 challenge below has been answered (digest_header). Both
+        // are withheld once a redirect leaves the original origin, so credentials
+        // never reach a host the caller did not address.
+        if same_origin
+            && let Some((digest, username, password)) = auth.as_ref()
+        {
             if *digest {
                 if let Some(h) = digest_header.as_ref() {
                     req = req.header(reqwest::header::AUTHORIZATION, h);
@@ -298,7 +346,7 @@ async fn execute_request(
 
         // Store Set-Cookie from this hop into the jar.
         if let (Some(jar), Some(host)) = (jar.as_ref(), host.as_ref()) {
-            let mut j = jar.lock().unwrap();
+            let mut j = jar.lock().unwrap_or_else(|e| e.into_inner());
             for value in resp.headers().get_all(reqwest::header::SET_COOKIE).iter() {
                 if let Ok(s) = value.to_str() {
                     j.set_from_header(host, s);
@@ -339,15 +387,21 @@ async fn execute_request(
             }
         }
 
-        // Follow a redirect if there is one to follow.
+        // Follow a redirect if there is one to follow. A redirect with a usable
+        // Location that we can't follow because the budget is spent is a "too
+        // many redirects" error, not a silent success returning the 3xx.
         if status.is_redirection()
-            && redirects_left > 0
             && let Some(next) = resp
                 .headers()
                 .get(reqwest::header::LOCATION)
                 .and_then(|l| l.to_str().ok())
                 .and_then(|loc| reqwest::Url::parse(&url).and_then(|base| base.join(loc)).ok())
         {
+            if redirects_left == 0 {
+                return Err(mlua::Error::external(format!(
+                    "http: too many redirects (max {MAX_REDIRECTS})"
+                )));
+            }
             redirects_left -= 1;
             // 303, and 301/302 on a POST, degrade to a bodyless GET — the
             // behaviour browsers and reqwest's own redirect policy apply.
@@ -420,7 +474,7 @@ fn make_session(
     tbl.raw_set("save", {
         let jar = jar.clone();
         lua.create_function(move |_, (_this, path): (LuaTable, String)| {
-            let jsonl = jar.lock().unwrap().to_jsonl();
+            let jsonl = jar.lock().unwrap_or_else(|e| e.into_inner()).to_jsonl();
             std::fs::write(&path, jsonl)
                 .map_err(|e| mlua::Error::external(format!("session:save: {e}")))
         })?
@@ -431,7 +485,7 @@ fn make_session(
         lua.create_function(move |_, (_this, path): (LuaTable, String)| {
             let src = std::fs::read_to_string(&path)
                 .map_err(|e| mlua::Error::external(format!("session:load: {e}")))?;
-            jar.lock().unwrap().merge_jsonl(&src);
+            jar.lock().unwrap_or_else(|e| e.into_inner()).merge_jsonl(&src);
             Ok(())
         })?
     })?;
@@ -439,7 +493,7 @@ fn make_session(
     tbl.raw_set("clearCookies", {
         let jar = jar.clone();
         lua.create_function(move |_, _this: LuaTable| {
-            jar.lock().unwrap().cookies.clear();
+            jar.lock().unwrap_or_else(|e| e.into_inner()).cookies.clear();
             Ok(())
         })?
     })?;
@@ -448,7 +502,7 @@ fn make_session(
         let jar = jar.clone();
         lua.create_function(move |lua, _this: LuaTable| {
             let outer = lua.create_table()?;
-            let j = jar.lock().unwrap();
+            let j = jar.lock().unwrap_or_else(|e| e.into_inner());
             for (domain, names) in j.cookies.iter() {
                 let inner = lua.create_table()?;
                 for (name, value) in names.iter() {
@@ -527,3 +581,71 @@ pub(super) fn install(lua: &Lua) -> LuaResult<()> {
     // session metatable wrapping http.session().
     lua.load(HTTP_LUA).set_name("@[stdlib/http]").exec()
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn cookie(jar: &CookieJar, domain: &str, name: &str) -> Option<String> {
+        jar.cookies.get(domain).and_then(|m| m.get(name).cloned())
+    }
+
+    #[test]
+    fn set_cookie_defaults_to_request_host() {
+        let mut jar = CookieJar::default();
+        jar.set_from_header("example.com", "sid=abc");
+        assert_eq!(cookie(&jar, "example.com", "sid").as_deref(), Some("abc"));
+    }
+
+    #[test]
+    fn set_cookie_honors_domain_the_host_belongs_to() {
+        let mut jar = CookieJar::default();
+        // A subdomain may scope a cookie up to its parent domain.
+        jar.set_from_header("app.example.com", "sid=abc; Domain=example.com");
+        assert_eq!(cookie(&jar, "example.com", "sid").as_deref(), Some("abc"));
+    }
+
+    #[test]
+    fn set_cookie_rejects_foreign_domain() {
+        let mut jar = CookieJar::default();
+        // Cookie tossing: a response from one host must not plant a cookie scoped
+        // to an unrelated domain. The bad Domain= is ignored; it stays host-scoped.
+        jar.set_from_header("127.0.0.1", "evil=1; Domain=other.example");
+        assert!(cookie(&jar, "other.example", "evil").is_none());
+        assert_eq!(cookie(&jar, "127.0.0.1", "evil").as_deref(), Some("1"));
+    }
+
+    #[test]
+    fn set_cookie_rejects_partial_suffix_match() {
+        let mut jar = CookieJar::default();
+        // "notexample.com" ends with "example.com" as a raw substring but is not
+        // a subdomain, so the Domain must be rejected.
+        jar.set_from_header("notexample.com", "x=1; Domain=example.com");
+        assert!(cookie(&jar, "example.com", "x").is_none());
+        assert_eq!(cookie(&jar, "notexample.com", "x").as_deref(), Some("1"));
+    }
+
+    #[test]
+    fn origins_compare_by_scheme_host_port() {
+        let u = |s: &str| origin_of(&reqwest::Url::parse(s).unwrap());
+        assert_eq!(u("https://a.com/x"), u("https://a.com/y")); // path-independent
+        assert_eq!(u("https://a.com"), u("https://a.com:443")); // default port
+        assert_ne!(u("https://a.com"), u("http://a.com")); // scheme differs
+        assert_ne!(u("https://a.com"), u("https://b.com")); // host differs
+        assert_ne!(u("https://a.com"), u("https://a.com:8443")); // port differs
+    }
+
+    #[test]
+    fn cookies_for_matches_domain_and_subdomains() {
+        let mut jar = CookieJar::default();
+        jar.set_from_header("example.com", "a=1");
+        assert_eq!(jar.cookies_for("example.com"), vec![("a".into(), "1".into())]);
+        // a cookie stored on example.com is sent to its subdomains
+        jar.set_from_header("sub.example.com", "b=2; Domain=example.com");
+        let mut got = jar.cookies_for("sub.example.com");
+        got.sort();
+        assert_eq!(got, vec![("a".into(), "1".into()), ("b".into(), "2".into())]);
+        // but not to an unrelated host
+        assert!(jar.cookies_for("other.com").is_empty());
+    }
+}
diff --git a/src/stdlib/logging.rs b/src/stdlib/logging.rs
index 7d4f8ee..e451119 100644
--- a/src/stdlib/logging.rs
+++ b/src/stdlib/logging.rs
@@ -5,7 +5,17 @@ fn args_to_string(lua: &Lua, args: Variadic<LuaValue>) -> LuaResult<String> {
     let tostring: mlua::Function = lua.globals().get("tostring")?;
     let parts: Vec<String> = args
         .into_iter()
-        .map(|v| tostring.call::<String>(v).unwrap_or_else(|_| "?".to_string()))
+        .map(|v| {
+            // tostring can yield a non-UTF-8 byte string (Lua strings are byte
+            // strings); render it lossily rather than collapsing the whole
+            // argument to "?" and losing its readable parts. "?" is reserved for
+            // the rare case where tostring itself errors (e.g. a broken
+            // __tostring metamethod).
+            match tostring.call::<mlua::String>(v) {
+                Ok(s) => s.to_string_lossy(),
+                Err(_) => "?".to_string(),
+            }
+        })
         .collect();
     Ok(parts.join("\t"))
 }
@@ -55,3 +65,28 @@ pub(super) fn install(lua: &Lua) -> LuaResult<()> {
     lua.globals().raw_set("log", log)?;
     Ok(())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn non_utf8_arg_is_rendered_lossily_not_dropped() {
+        let lua = Lua::new();
+        // A byte string that is not valid UTF-8 must keep its readable parts
+        // (via lossy conversion) rather than collapsing the whole argument to "?".
+        let args: Variadic<LuaValue> =
+            Variadic::from_iter([LuaValue::String(lua.create_string(b"\xff readable").unwrap())]);
+        let rendered = args_to_string(&lua, args).unwrap();
+        assert!(rendered.contains("readable"), "got: {rendered:?}");
+        assert_ne!(rendered, "?");
+    }
+
+    #[test]
+    fn multiple_args_are_tab_joined() {
+        let lua = Lua::new();
+        let args: Variadic<LuaValue> =
+            Variadic::from_iter([LuaValue::Integer(1), LuaValue::Boolean(true)]);
+        assert_eq!(args_to_string(&lua, args).unwrap(), "1\ttrue");
+    }
+}
diff --git a/src/stdlib/lua_dump.rs b/src/stdlib/lua_dump.rs
new file mode 100644
index 0000000..e1e8456
--- /dev/null
+++ b/src/stdlib/lua_dump.rs
@@ -0,0 +1,116 @@
+use std::borrow::Cow;
+
+use mlua::Value as LuaValue;
+use serde_json::Value as JsonValue;
+
+/// Pretty-print a Lua value for humans (the backend of `utils.dump`).
+/// Ported from flowbox-rt's fb_lua lua_dump.rs, adapted to mlua 0.11.
+pub(super) fn dump(value: LuaValue) -> Cow<'static, str> {
+    dump_inner(value, DumpPosition::Value, 0)
+}
+
+enum DumpPosition {
+    Key,
+    Value,
+}
+
+fn keywrap(value: Cow<'static, str>, position: DumpPosition) -> Cow<'static, str> {
+    match position {
+        DumpPosition::Key => format!("[{value}]").into(),
+        DumpPosition::Value => value,
+    }
+}
+
+fn dump_inner(value: LuaValue, position: DumpPosition, recursion_depth: usize) -> Cow<'static, str> {
+    let res: Cow<'static, str> = match value {
+        LuaValue::Nil => "nil".into(),
+        LuaValue::Boolean(v) => if v { "true" } else { "false" }.into(),
+        LuaValue::Integer(v) => v.to_string().into(),
+        LuaValue::Number(v) => {
+            if v.fract() == 0.0 {
+                // ensure decimal places are shown to indicate it is a float
+                format!("{:.1}", v.trunc()).into()
+            } else {
+                v.to_string().into()
+            }
+        }
+        LuaValue::String(v) => {
+            let stringified = v.to_string_lossy().to_string();
+            match position {
+                DumpPosition::Key => {
+                    // return to bypass the keywrap
+                    return if stringified.char_indices().any(|(index, c)| {
+                        if index == 0 {
+                            !c.is_ascii_alphabetic() && c != '_'
+                        } else {
+                            !c.is_ascii_alphanumeric() && c != '_'
+                        }
+                    }) {
+                        // json-serialize the string to add quotes and escapes
+                        format!("[{}]", serde_json::to_string(&JsonValue::String(stringified)).unwrap()).into()
+                    } else {
+                        // string lua key can be used as is {foo="bar"}
+                        stringified.into()
+                    };
+                }
+                DumpPosition::Value => serde_json::to_string(&JsonValue::String(stringified)).unwrap().into(),
+            }
+        }
+        LuaValue::Table(t) => {
+            if recursion_depth > 20 {
+                // Flow through keywrap so a table used as a key still renders as
+                // `[<TRUNCATED>]`, consistent with every other key.
+                return keywrap("<TRUNCATED>".into(), position);
+            }
+            let recursion_depth = recursion_depth + 1;
+
+            let mut buf = "{".to_string();
+
+            let mut first = true;
+            let mut list_next = Some(1);
+            for pair in t.pairs::<LuaValue, LuaValue>() {
+                let Ok((k, v)) = pair else {
+                    list_next = None;
+                    continue;
+                };
+
+                if !first {
+                    buf.push_str(", ");
+                }
+                first = false;
+
+                // special case for sequential numeric keys, starting at 1
+                if let Some(list_index) = list_next {
+                    if let LuaValue::Integer(index) = k
+                        && index == list_index
+                    {
+                        buf.push_str(&dump_inner(v, DumpPosition::Value, recursion_depth));
+                        list_next = Some(list_index + 1);
+                        continue;
+                    }
+                    list_next = None;
+                }
+
+                buf.push_str(&format!(
+                    "{}={}",
+                    dump_inner(k, DumpPosition::Key, recursion_depth),
+                    dump_inner(v, DumpPosition::Value, recursion_depth)
+                ));
+            }
+
+            buf.push('}');
+            buf.into()
+        }
+        // The null pointer lightuserdata is the JSON null sentinel (utils.NULL)
+        LuaValue::LightUserData(ud) if ud.0.is_null() => "NULL".into(),
+        // Complex objects can't be displayed
+        LuaValue::LightUserData(_) => "<LightUserData>".into(),
+        LuaValue::Function(_) => "<Function>".into(),
+        LuaValue::Thread(_) => "<Thread>".into(),
+        LuaValue::UserData(_) => "<UserData>".into(),
+        LuaValue::Error(e) => format!("<Error:{e}>").into(),
+        other => format!("<{}>", other.type_name()).into(),
+    };
+
+    keywrap(res, position)
+}
diff --git a/src/stdlib/mod.rs b/src/stdlib/mod.rs
index 98f6e64..4c988a0 100644
--- a/src/stdlib/mod.rs
+++ b/src/stdlib/mod.rs
@@ -1,5 +1,6 @@
 mod http;
 mod logging;
+mod lua_dump;
 mod math;
 mod os_ext;
 mod sqlite;
diff --git a/src/stdlib/os_ext.rs b/src/stdlib/os_ext.rs
index f7901f8..9d4f769 100644
--- a/src/stdlib/os_ext.rs
+++ b/src/stdlib/os_ext.rs
@@ -1,7 +1,7 @@
 use std::time::{Duration, SystemTime, UNIX_EPOCH};
 
 use mlua::prelude::LuaResult;
-use mlua::{Lua, Table as LuaTable};
+use mlua::{Lua, Table as LuaTable, Value as LuaValue};
 
 /// Extend the already-sandboxed `os` table with non-standard additions.
 pub(super) fn install(lua: &Lua) -> LuaResult<()> {
@@ -21,7 +21,33 @@ pub(super) fn install(lua: &Lua) -> LuaResult<()> {
     // os.sleep(seconds) — yields the Lua coroutine via tokio; does not block the thread.
     os.raw_set(
         "sleep",
-        lua.create_async_function(|_, seconds: f64| async move {
+        lua.create_async_function(|_, seconds: LuaValue| async move {
+            // Accept only a number, with a prefixed message (mlua's own coercion
+            // would report a bare "error converting ..." for e.g. a string).
+            let seconds = match seconds {
+                LuaValue::Integer(i) => i as f64,
+                LuaValue::Number(n) => n,
+                other => {
+                    return Err(mlua::Error::external(format!(
+                        "os.sleep: duration must be a number (got {})",
+                        other.type_name()
+                    )));
+                }
+            };
+            // Cap the delay: a huge-but-finite value (e.g. 1e18) would otherwise
+            // park the task effectively forever with no way to interrupt it from
+            // Lua, which reads as the runtime hanging rather than the script.
+            const MAX_SLEEP_SECS: f64 = 24.0 * 60.0 * 60.0; // one day
+            if !(seconds.is_finite() && seconds >= 0.0) {
+                return Err(mlua::Error::external(
+                    "os.sleep: duration must be a non-negative finite number of seconds",
+                ));
+            }
+            if seconds > MAX_SLEEP_SECS {
+                return Err(mlua::Error::external(format!(
+                    "os.sleep: refusing to sleep for more than {MAX_SLEEP_SECS} seconds (got {seconds})"
+                )));
+            }
             let duration = Duration::try_from_secs_f64(seconds).map_err(|_| {
                 mlua::Error::external(
                     "os.sleep: duration must be a non-negative finite number of seconds",
diff --git a/src/stdlib/sqlite.rs b/src/stdlib/sqlite.rs
index 064ff22..050a4d1 100644
--- a/src/stdlib/sqlite.rs
+++ b/src/stdlib/sqlite.rs
@@ -130,7 +130,16 @@ fn lua_value_to_sqlite(value: LuaValue) -> LuaResult<Value> {
         LuaValue::Boolean(b) => Ok(Value::Integer(b as i64)),
         LuaValue::Integer(i) => Ok(Value::Integer(i)),
         LuaValue::Number(f) => Ok(Value::Real(f)),
-        LuaValue::String(s) => Ok(Value::Text(s.to_str()?.to_owned())),
+        // Lua strings are byte strings. Valid UTF-8 binds as TEXT; anything else
+        // (raw bytes, embedded NULs) binds as a BLOB so binary data round-trips
+        // instead of failing the UTF-8 conversion.
+        LuaValue::String(s) => {
+            let bytes = s.as_bytes();
+            match std::str::from_utf8(&bytes) {
+                Ok(text) => Ok(Value::Text(text.to_owned())),
+                Err(_) => Ok(Value::Blob(bytes.to_vec())),
+            }
+        }
         other => Err(mlua::Error::external(format!(
             "sqlite: cannot bind value of type '{}'",
             other.type_name()
@@ -224,11 +233,37 @@ fn rows_to_lua(lua: &Lua, rows: Vec<Record>) -> LuaResult<LuaTable> {
 // Blocking workers (run on the tokio blocking pool)
 // ---------------------------------------------------------------------------
 
+/// Reject SQL that is empty/comment-only or contains more than one statement.
+///
+/// `execute`/`query`/`queryOne` compile a single statement via `prepare_cached`,
+/// which silently ignores anything after the first — so `execute("A; B")` would
+/// run only `A` and drop `B` with no error, and `execute("")` surfaces SQLite's
+/// bare "not an error". `Batch` uses SQLite's own tokenizer to count statements
+/// (skipping comments/whitespace), giving a clear message instead. Use
+/// `executeBatch` to run multiple statements on purpose.
+fn ensure_single_statement(conn: &rusqlite::Connection, sql: &str) -> Result<(), DbError> {
+    let mut batch = rusqlite::Batch::new(conn, sql);
+    let mut count = 0usize;
+    while batch.next()?.is_some() {
+        count += 1;
+        if count > 1 {
+            return Err(DbError::Other(
+                "sqlite: expected a single SQL statement (use executeBatch for multiple)".to_string(),
+            ));
+        }
+    }
+    if count == 0 {
+        return Err(DbError::Other("sqlite: no SQL statement to run".to_string()));
+    }
+    Ok(())
+}
+
 /// Run an INSERT/UPDATE/DELETE-style statement, returning rows changed.
 async fn run_execute(handle: ConnHandle, sql: String, params: BoundParams) -> Result<usize, DbError> {
     tokio::task::spawn_blocking(move || -> Result<usize, DbError> {
         let guard = handle.lock().unwrap_or_else(|e| e.into_inner());
         let conn = guard.as_ref().ok_or(DbError::Closed)?;
+        ensure_single_statement(conn, &sql)?;
         let mut stmt = conn.prepare_cached(&sql)?;
         bind_params(&mut stmt, &params)?;
         Ok(stmt.raw_execute()?)
@@ -237,11 +272,24 @@ async fn run_execute(handle: ConnHandle, sql: String, params: BoundParams) -> Re
     .unwrap_or_else(|e| Err(DbError::Other(format!("sqlite: background task failed: {e}"))))
 }
 
+/// Run every statement in `sql` in order, with no parameter binding.
+async fn run_execute_batch(handle: ConnHandle, sql: String) -> Result<(), DbError> {
+    tokio::task::spawn_blocking(move || -> Result<(), DbError> {
+        let guard = handle.lock().unwrap_or_else(|e| e.into_inner());
+        let conn = guard.as_ref().ok_or(DbError::Closed)?;
+        conn.execute_batch(&sql)?;
+        Ok(())
+    })
+    .await
+    .unwrap_or_else(|e| Err(DbError::Other(format!("sqlite: background task failed: {e}"))))
+}
+
 /// Run a SELECT-style statement, materializing every row.
 async fn run_query(handle: ConnHandle, sql: String, params: BoundParams) -> Result<Vec<Record>, DbError> {
     tokio::task::spawn_blocking(move || -> Result<Vec<Record>, DbError> {
         let guard = handle.lock().unwrap_or_else(|e| e.into_inner());
         let conn = guard.as_ref().ok_or(DbError::Closed)?;
+        ensure_single_statement(conn, &sql)?;
         let mut stmt = conn.prepare_cached(&sql)?;
         // Column names must be captured before the mutable borrows below.
         let columns: Vec<String> = stmt.column_names().into_iter().map(String::from).collect();
@@ -279,6 +327,14 @@ impl UserData for SqliteConn {
             }
         });
 
+        methods.add_async_method("executeBatch", |_, this, sql: String| {
+            let handle = this.0.clone();
+            async move {
+                run_execute_batch(handle, sql).await.map_err(mlua::Error::external)?;
+                Ok(())
+            }
+        });
+
         methods.add_async_method("query", |lua, this, (sql, params): (String, Option<LuaTable>)| {
             let handle = this.0.clone();
             let bound = convert_params(params);
@@ -301,23 +357,49 @@ impl UserData for SqliteConn {
             }
         });
 
-        // These only read in-memory connection state, so they stay synchronous.
-        methods.add_method("lastInsertRowid", |_, this, ()| {
-            let guard = this.0.lock().unwrap_or_else(|e| e.into_inner());
-            let conn = guard.as_ref().ok_or_else(|| mlua::Error::external(DbError::Closed))?;
-            Ok(conn.last_insert_rowid())
+        // These only read in-memory connection state, but they still contend on
+        // the same mutex that a running query holds for its whole duration. Doing
+        // the lock on the blocking pool (not inline) keeps the tokio event loop
+        // responsive: a `close()` next to a long query no longer freezes every
+        // other coroutine and timer.
+        methods.add_async_method("lastInsertRowid", |_, this, ()| {
+            let handle = this.0.clone();
+            async move {
+                tokio::task::spawn_blocking(move || -> Result<i64, DbError> {
+                    let guard = handle.lock().unwrap_or_else(|e| e.into_inner());
+                    Ok(guard.as_ref().ok_or(DbError::Closed)?.last_insert_rowid())
+                })
+                .await
+                .unwrap_or_else(|e| Err(DbError::Other(format!("sqlite: background task failed: {e}"))))
+                .map_err(mlua::Error::external)
+            }
         });
 
-        methods.add_method("changes", |_, this, ()| {
-            let guard = this.0.lock().unwrap_or_else(|e| e.into_inner());
-            let conn = guard.as_ref().ok_or_else(|| mlua::Error::external(DbError::Closed))?;
-            Ok(conn.changes() as i64)
+        methods.add_async_method("changes", |_, this, ()| {
+            let handle = this.0.clone();
+            async move {
+                tokio::task::spawn_blocking(move || -> Result<i64, DbError> {
+                    let guard = handle.lock().unwrap_or_else(|e| e.into_inner());
+                    Ok(guard.as_ref().ok_or(DbError::Closed)?.changes() as i64)
+                })
+                .await
+                .unwrap_or_else(|e| Err(DbError::Other(format!("sqlite: background task failed: {e}"))))
+                .map_err(mlua::Error::external)
+            }
         });
 
-        methods.add_method("close", |_, this, ()| {
-            // Dropping the connection releases the SQLite handle; later use errors.
-            *this.0.lock().unwrap_or_else(|e| e.into_inner()) = None;
-            Ok(())
+        methods.add_async_method("close", |_, this, ()| {
+            let handle = this.0.clone();
+            async move {
+                // Dropping the connection releases the SQLite handle; later use errors.
+                // Done on the blocking pool so it waits behind an in-flight query
+                // there rather than stalling the event loop.
+                tokio::task::spawn_blocking(move || {
+                    *handle.lock().unwrap_or_else(|e| e.into_inner()) = None;
+                })
+                .await
+                .map_err(|e| mlua::Error::external(format!("sqlite: background task failed: {e}")))
+            }
         });
     }
 }
@@ -331,8 +413,13 @@ pub(super) fn install(lua: &Lua) -> LuaResult<()> {
 
     sqlite.set(
         "connect",
-        lua.create_function(|_, path: String| {
-            let conn = rusqlite::Connection::open(&path).map_err(mlua::Error::external)?;
+        lua.create_async_function(|_, path: String| async move {
+            // Opening a file-backed database touches disk, so do it on the
+            // blocking pool rather than the tokio event loop.
+            let conn = tokio::task::spawn_blocking(move || rusqlite::Connection::open(&path))
+                .await
+                .map_err(|e| mlua::Error::external(format!("sqlite.connect: background task failed: {e}")))?
+                .map_err(|e| mlua::Error::external(format!("sqlite.connect: {e}")))?;
             Ok(SqliteConn(Arc::new(Mutex::new(Some(conn)))))
         })?,
     )?;
diff --git a/src/stdlib/task.rs b/src/stdlib/task.rs
index 548c0fa..07647e0 100644
--- a/src/stdlib/task.rs
+++ b/src/stdlib/task.rs
@@ -2,6 +2,26 @@ use futures::future::join_all;
 use mlua::prelude::{LuaResult, LuaValue};
 use mlua::{Function, Lua, MultiValue, Variadic};
 
+/// Validate that every variadic argument is a function, returning them as a
+/// `Vec<Function>`. Produces a `task.join:`-prefixed error naming the offending
+/// argument position and type, instead of mlua's bare conversion message.
+fn functions_or_error(args: Variadic<LuaValue>) -> LuaResult<Vec<Function>> {
+    let mut out = Vec::with_capacity(args.len());
+    for (i, v) in args.into_iter().enumerate() {
+        match v {
+            LuaValue::Function(f) => out.push(f),
+            other => {
+                return Err(mlua::Error::external(format!(
+                    "task.join: argument #{} must be a function (got {})",
+                    i + 1,
+                    other.type_name()
+                )))
+            }
+        }
+    }
+    Ok(out)
+}
+
 /// Proof-of-concept concurrency primitive built on Lua coroutines + tokio.
 ///
 /// `task.join(f1, f2, ...)` runs each function as its own Lua coroutine and
@@ -19,7 +39,8 @@ pub(super) fn install(lua: &Lua) -> LuaResult<()> {
 
     task.raw_set(
         "join",
-        lua.create_async_function(|lua, funcs: Variadic<Function>| async move {
+        lua.create_async_function(|lua, args: Variadic<LuaValue>| async move {
+            let funcs = functions_or_error(args)?;
             // Wrap each function in its own coroutine and turn it into a future.
             let mut threads = Vec::with_capacity(funcs.len());
             for f in funcs.iter() {
diff --git a/src/stdlib/utils.rs b/src/stdlib/utils.rs
index 046d460..1734ca0 100644
--- a/src/stdlib/utils.rs
+++ b/src/stdlib/utils.rs
@@ -1,20 +1,12 @@
-use std::ffi::c_void;
-
 use mlua::prelude::LuaResult;
-use mlua::{LightUserData, Lua, Value as LuaValue};
-use serde_json;
+use mlua::{Lua, Value as LuaValue};
 
 const UTILS_LUA: &str = include_str!("../../lua/stdlib/utils.lua");
 
-// A stable address used as the identity of utils.NULL.
-static NULL_MARKER: u8 = 0;
-
-fn null_lud() -> LightUserData {
-    LightUserData(std::ptr::addr_of!(NULL_MARKER) as *mut c_void)
-}
-
+// utils.NULL is a null-pointer light userdata - the same sentinel mlua itself
+// uses for JSON null (mlua::Value::NULL), and the same convention flowbox uses.
 pub(crate) fn is_null(val: &LuaValue) -> bool {
-    matches!(val, LuaValue::LightUserData(p) if *p == null_lud())
+    matches!(val, LuaValue::LightUserData(p) if p.0.is_null())
 }
 
 // ---------------------------------------------------------------------------
@@ -38,7 +30,17 @@ pub(crate) fn lua_to_json(val: LuaValue, depth: u32) -> LuaResult<serde_json::Va
             .ok_or_else(|| {
                 mlua::Error::external("utils.toJSON: NaN and Infinity cannot be serialized as JSON")
             }),
-        LuaValue::String(s) => Ok(serde_json::Value::String(s.to_str()?.to_owned())),
+        LuaValue::String(s) => {
+            // JSON strings must be UTF-8. Lua strings are byte strings, so give a
+            // clear prefixed error instead of mlua's bare conversion message.
+            let bytes = s.as_bytes();
+            match std::str::from_utf8(&bytes) {
+                Ok(text) => Ok(serde_json::Value::String(text.to_owned())),
+                Err(_) => Err(mlua::Error::external(
+                    "utils.toJSON: string is not valid UTF-8 and cannot be encoded as JSON",
+                )),
+            }
+        }
         LuaValue::Table(t) => table_to_json(t, depth),
         other => Err(mlua::Error::external(format!(
             "utils.toJSON: cannot serialize value of type '{}'",
@@ -48,7 +50,7 @@ pub(crate) fn lua_to_json(val: LuaValue, depth: u32) -> LuaResult<serde_json::Va
 }
 
 pub(crate) fn table_to_json(t: mlua::Table, depth: u32) -> LuaResult<serde_json::Value> {
-    let seq_len = t.raw_len() as usize;
+    let seq_len = t.raw_len();
 
     // Try array serialization: every key must be a sequential integer in 1..=seq_len.
     if seq_len > 0 {
@@ -89,6 +91,14 @@ pub(crate) fn table_to_json(t: mlua::Table, depth: u32) -> LuaResult<serde_json:
                 )))
             }
         };
+        // Stringifying integer keys can collide with a real string key (e.g.
+        // both `[1]` and `["1"]`). Silently dropping one would be data loss, so
+        // fail loudly like every other unrepresentable case here.
+        if map.contains_key(&key) {
+            return Err(mlua::Error::external(format!(
+                "utils.toJSON: duplicate object key '{key}' (an integer key collides with a string key)"
+            )));
+        }
         map.insert(key, lua_to_json(v, depth + 1)?);
     }
     Ok(serde_json::Value::Object(map))
@@ -100,7 +110,7 @@ pub(crate) fn table_to_json(t: mlua::Table, depth: u32) -> LuaResult<serde_json:
 
 fn json_to_lua(lua: &Lua, val: serde_json::Value) -> LuaResult<LuaValue> {
     match val {
-        serde_json::Value::Null => Ok(LuaValue::LightUserData(null_lud())),
+        serde_json::Value::Null => Ok(LuaValue::NULL),
         serde_json::Value::Bool(b) => Ok(LuaValue::Boolean(b)),
         serde_json::Value::Number(n) => {
             if let Some(i) = n.as_i64() {
@@ -134,13 +144,18 @@ fn json_to_lua(lua: &Lua, val: serde_json::Value) -> LuaResult<LuaValue> {
 pub(super) fn install(lua: &Lua) -> LuaResult<()> {
     let utils = lua.create_table()?;
 
-    utils.raw_set("NULL", LuaValue::LightUserData(null_lud()))?;
+    utils.raw_set("NULL", LuaValue::NULL)?;
 
     utils.raw_set(
         "isNull",
         lua.create_function(|_, val: LuaValue| Ok(is_null(&val)))?,
     )?;
 
+    utils.raw_set(
+        "dump",
+        lua.create_function(|_, val: LuaValue| Ok(super::lua_dump::dump(val).into_owned()))?,
+    )?;
+
     utils.raw_set(
         "toJSON",
         lua.create_function(|_, (val, pretty): (LuaValue, Option<bool>)| {
@@ -166,6 +181,6 @@ pub(super) fn install(lua: &Lua) -> LuaResult<()> {
 
     lua.globals().raw_set("utils", utils)?;
 
-    // Lua side adds: utils.dump, utils.try, utils.tryn
+    // Lua side adds: utils.try, utils.tryn
     lua.load(UTILS_LUA).set_name("@[stdlib/utils]").exec()
 }