diff --git a/lib/lua/runtime.sx b/lib/lua/runtime.sx
index e3f0d948..68c70de6 100644
--- a/lib/lua/runtime.sx
+++ b/lib/lua/runtime.sx
@@ -1538,12 +1538,50 @@
             (else (lua-to-display v)))))
       (else (lua-to-display v)))))
 
+(define
+  lua-parse-int-base
+  (fn (s base)
+    (let ((trimmed (trim s)) (neg false) (i 0) (n 0) (valid false))
+      (begin
+        (when (and (> (len trimmed) 0) (= (char-at trimmed 0) "-"))
+          (begin (set! neg true) (set! i 1)))
+        (when (and (> (len trimmed) i) (= (char-at trimmed i) "+"))
+          (set! i (+ i 1)))
+        (define
+          pi-loop
+          (fn ()
+            (when (< i (len trimmed))
+              (let ((c (char-at trimmed i)))
+                (let ((d (cond
+                           ((and (>= c "0") (<= c "9")) (- (char-code c) (char-code "0")))
+                           ((and (>= c "a") (<= c "z")) (+ 10 (- (char-code c) (char-code "a"))))
+                           ((and (>= c "A") (<= c "Z")) (+ 10 (- (char-code c) (char-code "A"))))
+                           (else -1))))
+                  (cond
+                    ((or (< d 0) (>= d base)) (set! i (len trimmed)))
+                    (else
+                      (begin
+                        (set! n (+ (* n base) d))
+                        (set! valid true)
+                        (set! i (+ i 1))
+                        (pi-loop)))))))))
+        (pi-loop)
+        (cond
+          ((not valid) nil)
+          ((< i (len trimmed)) nil)
+          (neg (- 0 n))
+          (else n))))))
+
 (define
   lua-tonumber
   (fn (&rest args)
     (let ((v (first args))
           (base (if (> (len args) 1) (nth args 1) nil)))
       (cond
+        ((not (= base nil))
+          (cond
+            ((= (type-of v) "string") (lua-parse-int-base v base))
+            (else nil)))
         ((= (type-of v) "number") v)
         ((= (type-of v) "string") (lua-to-number v))
         (else nil)))))
diff --git a/lib/lua/scoreboard.json b/lib/lua/scoreboard.json
index 0b6bce3d..8a6acc38 100644
--- a/lib/lua/scoreboard.json
+++ b/lib/lua/scoreboard.json
@@ -1,8 +1,8 @@
 {
   "totals": {
     "pass": 1,
-    "fail": 12,
-    "timeout": 3,
+    "fail": 11,
+    "timeout": 4,
     "skip": 8,
     "total": 24,
     "runnable": 16,
@@ -11,11 +11,15 @@
   "top_failure_modes": [
     [
       "other: Unhandled exception: \\\"Unhandled exception: \\\\\\\"assertion failed!\\\\\\\"\\",
-      8
+      6
     ],
     [
       "timeout",
-      3
+      4
+    ],
+    [
+      "other: Unhandled exception: \\\"Unhandled exception: \\\\\\\"lua: attempt to call non-functio",
+      2
     ],
     [
       "other: Unhandled exception: \\\"Unhandled exception: \\\\\\\"lua: module 'C' not found\\\\\\\"\\",
@@ -28,10 +32,6 @@
     [
       "other: Unhandled exception: \\\"Unhandled exception: \\\\\\\"lua: attempt to compare incompat",
       1
-    ],
-    [
-      "other: Unhandled exception: \\\"Unhandled exception: \\\\\\\"lua: attempt to call non-functio",
-      1
     ]
   ],
   "results": [
@@ -51,19 +51,19 @@
       "name": "attrib.lua",
       "status": "fail",
       "reason": "other: Unhandled exception: \\\"Unhandled exception: \\\\\\\"lua: module 'C' not found\\\\\\\"\\",
-      "ms": 6137
+      "ms": 6133
     },
     {
       "name": "big.lua",
       "status": "timeout",
       "reason": "per-test timeout",
-      "ms": 8008
+      "ms": 8007
     },
     {
       "name": "calls.lua",
       "status": "fail",
       "reason": "undefined symbol: fat\\",
-      "ms": 4744
+      "ms": 5786
     },
     {
       "name": "checktable.lua",
@@ -87,7 +87,7 @@
       "name": "constructs.lua",
       "status": "fail",
       "reason": "other: Unhandled exception: \\\"Unhandled exception: \\\\\\\"lua: attempt to compare incompat",
-      "ms": 6638
+      "ms": 7418
     },
     {
       "name": "db.lua",
@@ -99,13 +99,13 @@
       "name": "errors.lua",
       "status": "fail",
       "reason": "other: Unhandled exception: \\\"Unhandled exception: \\\\\\\"assertion failed!\\\\\\\"\\",
-      "ms": 3109
+      "ms": 4168
     },
     {
       "name": "events.lua",
       "status": "fail",
       "reason": "other: Unhandled exception: \\\"Unhandled exception: \\\\\\\"assertion failed!\\\\\\\"\\",
-      "ms": 7069
+      "ms": 7884
     },
     {
       "name": "files.lua",
@@ -123,13 +123,13 @@
       "name": "literals.lua",
       "status": "fail",
       "reason": "other: Unhandled exception: \\\"Unhandled exception: \\\\\\\"assertion failed!\\\\\\\"\\",
-      "ms": 1866
+      "ms": 1796
     },
     {
       "name": "locals.lua",
       "status": "fail",
       "reason": "other: Unhandled exception: \\\"Unhandled exception: \\\\\\\"lua: attempt to call non-functio",
-      "ms": 1612
+      "ms": 1655
     },
     {
       "name": "main.lua",
@@ -140,44 +140,44 @@
     {
       "name": "math.lua",
       "status": "fail",
-      "reason": "other: Unhandled exception: \\\"Unhandled exception: \\\\\\\"assertion failed!\\\\\\\"\\",
-      "ms": 3983
+      "reason": "other: Unhandled exception: \\\"Unhandled exception: \\\\\\\"lua: attempt to call non-functio",
+      "ms": 5457
     },
     {
       "name": "nextvar.lua",
-      "status": "fail",
-      "reason": "other: Unhandled exception: \\\"Unhandled exception: \\\\\\\"assertion failed!\\\\\\\"\\",
-      "ms": 6968
-    },
-    {
-      "name": "pm.lua",
-      "status": "fail",
-      "reason": "other: Unhandled exception: \\\"Unhandled exception: \\\\\\\"assertion failed!\\\\\\\"\\",
-      "ms": 5852
-    },
-    {
-      "name": "sort.lua",
       "status": "timeout",
       "reason": "per-test timeout",
       "ms": 8007
     },
+    {
+      "name": "pm.lua",
+      "status": "fail",
+      "reason": "other: Unhandled exception: \\\"Unhandled exception: \\\\\\\"assertion failed!\\\\\\\"\\",
+      "ms": 6576
+    },
+    {
+      "name": "sort.lua",
+      "status": "timeout",
+      "reason": "per-test timeout",
+      "ms": 8008
+    },
     {
       "name": "strings.lua",
       "status": "fail",
       "reason": "other: Unhandled exception: \\\"Unhandled exception: \\\\\\\"assertion failed!\\\\\\\"\\",
-      "ms": 3925
+      "ms": 4708
     },
     {
       "name": "vararg.lua",
       "status": "fail",
       "reason": "other: Unhandled exception: \\\"Unhandled exception: \\\\\\\"assertion failed!\\\\\\\"\\",
-      "ms": 2195
+      "ms": 2227
     },
     {
       "name": "verybig.lua",
       "status": "pass",
       "reason": "",
-      "ms": 930
+      "ms": 959
     }
   ]
 }
\ No newline at end of file
diff --git a/lib/lua/scoreboard.md b/lib/lua/scoreboard.md
index b719d360..9612c3aa 100644
--- a/lib/lua/scoreboard.md
+++ b/lib/lua/scoreboard.md
@@ -1,16 +1,16 @@
 # Lua-on-SX conformance scoreboard
 
 **Pass rate:** 1/16 runnable (6.2%)
-fail=12 timeout=3 skip=8 total=24
+fail=11 timeout=4 skip=8 total=24
 
 ## Top failure modes
 
-- **8x** other: Unhandled exception: \"Unhandled exception: \\\"assertion failed!\\\"\
-- **3x** timeout
+- **6x** other: Unhandled exception: \"Unhandled exception: \\\"assertion failed!\\\"\
+- **4x** timeout
+- **2x** other: Unhandled exception: \"Unhandled exception: \\\"lua: attempt to call non-functio
 - **1x** other: Unhandled exception: \"Unhandled exception: \\\"lua: module 'C' not found\\\"\
 - **1x** undefined symbol: fat\
 - **1x** other: Unhandled exception: \"Unhandled exception: \\\"lua: attempt to compare incompat
-- **1x** other: Unhandled exception: \"Unhandled exception: \\\"lua: attempt to call non-functio
 
 ## Per-test results
 
@@ -18,25 +18,25 @@ fail=12 timeout=3 skip=8 total=24
 |---|---|---|---:|
 | all.lua | skip | driver uses dofile to chain other tests | 0 |
 | api.lua | skip | requires testC (C debug library) | 0 |
-| attrib.lua | fail | other: Unhandled exception: \"Unhandled exception: \\\"lua: module 'C' not found\\\"\ | 6137 |
-| big.lua | timeout | per-test timeout | 8008 |
-| calls.lua | fail | undefined symbol: fat\ | 4744 |
+| attrib.lua | fail | other: Unhandled exception: \"Unhandled exception: \\\"lua: module 'C' not found\\\"\ | 6133 |
+| big.lua | timeout | per-test timeout | 8007 |
+| calls.lua | fail | undefined symbol: fat\ | 5786 |
 | checktable.lua | skip | internal debug helpers | 0 |
 | closure.lua | timeout | per-test timeout | 8008 |
 | code.lua | skip | bytecode inspection via debug library | 0 |
-| constructs.lua | fail | other: Unhandled exception: \"Unhandled exception: \\\"lua: attempt to compare incompat | 6638 |
+| constructs.lua | fail | other: Unhandled exception: \"Unhandled exception: \\\"lua: attempt to compare incompat | 7418 |
 | db.lua | skip | debug library | 0 |
-| errors.lua | fail | other: Unhandled exception: \"Unhandled exception: \\\"assertion failed!\\\"\ | 3109 |
-| events.lua | fail | other: Unhandled exception: \"Unhandled exception: \\\"assertion failed!\\\"\ | 7069 |
+| errors.lua | fail | other: Unhandled exception: \"Unhandled exception: \\\"assertion failed!\\\"\ | 4168 |
+| events.lua | fail | other: Unhandled exception: \"Unhandled exception: \\\"assertion failed!\\\"\ | 7884 |
 | files.lua | skip | io library | 0 |
 | gc.lua | skip | collectgarbage / finalisers | 0 |
-| literals.lua | fail | other: Unhandled exception: \"Unhandled exception: \\\"assertion failed!\\\"\ | 1866 |
-| locals.lua | fail | other: Unhandled exception: \"Unhandled exception: \\\"lua: attempt to call non-functio | 1612 |
+| literals.lua | fail | other: Unhandled exception: \"Unhandled exception: \\\"assertion failed!\\\"\ | 1796 |
+| locals.lua | fail | other: Unhandled exception: \"Unhandled exception: \\\"lua: attempt to call non-functio | 1655 |
 | main.lua | skip | standalone interpreter driver | 0 |
-| math.lua | fail | other: Unhandled exception: \"Unhandled exception: \\\"assertion failed!\\\"\ | 3983 |
-| nextvar.lua | fail | other: Unhandled exception: \"Unhandled exception: \\\"assertion failed!\\\"\ | 6968 |
-| pm.lua | fail | other: Unhandled exception: \"Unhandled exception: \\\"assertion failed!\\\"\ | 5852 |
-| sort.lua | timeout | per-test timeout | 8007 |
-| strings.lua | fail | other: Unhandled exception: \"Unhandled exception: \\\"assertion failed!\\\"\ | 3925 |
-| vararg.lua | fail | other: Unhandled exception: \"Unhandled exception: \\\"assertion failed!\\\"\ | 2195 |
-| verybig.lua | pass | - | 930 |
+| math.lua | fail | other: Unhandled exception: \"Unhandled exception: \\\"lua: attempt to call non-functio | 5457 |
+| nextvar.lua | timeout | per-test timeout | 8007 |
+| pm.lua | fail | other: Unhandled exception: \"Unhandled exception: \\\"assertion failed!\\\"\ | 6576 |
+| sort.lua | timeout | per-test timeout | 8008 |
+| strings.lua | fail | other: Unhandled exception: \"Unhandled exception: \\\"assertion failed!\\\"\ | 4708 |
+| vararg.lua | fail | other: Unhandled exception: \"Unhandled exception: \\\"assertion failed!\\\"\ | 2227 |
+| verybig.lua | pass | - | 959 |
diff --git a/lib/lua/test.sh b/lib/lua/test.sh
index 22922649..deebeb57 100755
--- a/lib/lua/test.sh
+++ b/lib/lua/test.sh
@@ -978,6 +978,14 @@ cat > "$TMPFILE" << 'EPOCHS'
 (epoch 1895)
 (eval "(lua-eval-ast \"if string.find(\\\"hello\\\", \\\"^wor\\\") then return 0 else return 1 end\")")
 
+;; ── tonumber with base (Lua 5.1) ──────────────────────────────
+(epoch 1900)
+(eval "(lua-eval-ast \"return tonumber('1010', 2)\")")
+(epoch 1901)
+(eval "(lua-eval-ast \"return tonumber('FF', 16)\")")
+(epoch 1902)
+(eval "(lua-eval-ast \"if tonumber('99', 8) == nil then return 1 else return 0 end\")")
+
 EPOCHS
 
 OUTPUT=$(timeout 60 "$SX_SERVER" < "$TMPFILE" 2>/dev/null)
@@ -1482,6 +1490,11 @@ check 1893 "gsub %d → X"                    '"X + X = X:3"'
 check 1894 "find ^ anchor hit"              '1'
 check 1895 "find ^ anchor miss"             '1'
 
+# ── tonumber with base ───────────────────────────────────────
+check 1900 "tonumber('1010', 2)"            '10'
+check 1901 "tonumber('FF', 16)"             '255'
+check 1902 "tonumber('99', 8) → nil"        '1'
+
 TOTAL=$((PASS + FAIL))
 if [ $FAIL -eq 0 ]; then
   echo "ok $PASS/$TOTAL Lua-on-SX tests passed"
diff --git a/plans/lua-on-sx.md b/plans/lua-on-sx.md
index 97abea0c..879b0e15 100644
--- a/plans/lua-on-sx.md
+++ b/plans/lua-on-sx.md
@@ -82,6 +82,7 @@ Each item: implement → tests → tick box → update progress log.
 
 _Newest first. Agent appends on every commit._
 
+- 2026-04-24: lua: scoreboard iteration — `tonumber(s, base)` for bases 2-36. Validates digit ranges per base, supports leading `+`/`-`, trims whitespace. `math.lua` past assert #21. Asserts 8→6, timeouts 3→4. 384/384 green.
 - 2026-04-24: lua: scoreboard iteration — added `lua-unwrap-final-return` (post-processor that rewrites top-level `(raise (list 'lua-ret V))` → `V` so top-level defines leak to SX top and loadstring closures can see them). Tried dropping the function-guard at top level, but too many tests use `if x then return 0 else return err end` at chunk tail, whose returns aren't at the *statement-list* tail — guard still needed. Kept guard + unwrap-as-no-op. Scoreboard unchanged.
 - 2026-04-24: lua: scoreboard iteration — `lua-pat-strip-captures` helper lets patterns with `(...)` capture parens at least match (captures themselves aren't returned yet — match returns whole match). Unblocks common Lua pattern idioms like `(%a+)=(%d+)`. Scoreboard unchanged.
 - 2026-04-24: lua: scoreboard iteration — extended pattern engine to `string.match`/`gmatch`/`gsub`. `gsub` now supports string/function/table replacement modes. 381/381 green (+6 pattern tests).