fix(engine): count fnmatch label-pattern wildcard groups per raw star, not by path-glob rules

labelPatternToRegExp reused change-guardrail's path-glob wildcard-group counter
to guard against catastrophic backtracking, but that counter treats a ** pair as
ONE group (the path compiler collapses ** into a single .*). The fnmatch compiler
here has no ** concept and emits one .* per *, so the count and the compiled regex
disagreed for any ** pattern: *a**b counted 2 but compiled 3 .* groups and was
wrongly accepted, admitting a pattern this compiler builds into a catastrophic-
backtracking RegExp on an adversarial near-miss label.

Count one group per raw * (no ** pairing; ? and [..] are not counted) and compare
against the shared MAX_GLOB_WILDCARD_GROUPS, now exported from change-guardrail
rather than redeclared. An over-complex registry key degrades to the existing
LABEL_PATTERN_NEVER_MATCHES and is still cached. The path-glob counter and every
path consumer keep their **-is-one-group semantics unchanged.

Closes #9994

Author: shin-core

apps/loopover-ui/public/downloads/loopover-extension.zip

@@ -1,4 +1,4 @@
-import { hasUnsafeWildcardCount } from "../signals/change-guardrail.js";
+import { MAX_GLOB_WILDCARD_GROUPS } from "../signals/change-guardrail.js";
 
 export function labelMatchesPattern(label: string, pattern: string): boolean {
   return labelPatternToRegExp(pattern.toLowerCase()).test(label.toLowerCase());
@@ -42,6 +42,19 @@ const LABEL_PATTERN_NEVER_MATCHES = /^(?!)$/;
 // change-guardrail.ts (there `*` stops at `/` and `?` is literal): labels are flat strings, so `*` matches any
 // run, `?` any single character, and `[seq]`/`[!seq]` a character class. Literal keys are unaffected — for a
 // pattern with no glob metacharacter the RegExp is an exact match, so existing configs score identically.
+
+/** Count the backtracking-capable wildcard GROUPS this fnmatch compiler will emit: one per raw `*` (each
+ *  compiles to a `.*` below), with NO `**`-is-one-group rule — unlike change-guardrail's path-glob counter,
+ *  this compiler has no globstar concept, so `**` is two `.*` groups, not one (#9994). `?` is not counted (it
+ *  compiles to a single `.`, which cannot backtrack ambiguously), and neither are `[…]` classes. */
+function fnmatchWildcardGroups(pattern: string): number {
+  let count = 0;
+  for (let i = 0; i < pattern.length; i += 1) {
+    if (pattern.charAt(i) === "*") count += 1;
+  }
+  return count;
+}
+
 function labelPatternToRegExp(pattern: string): RegExp {
   const cached = labelPatternRegExpCache.get(pattern);
   if (cached !== undefined) {
@@ -51,13 +64,15 @@ function labelPatternToRegExp(pattern: string): RegExp {
     labelPatternRegExpCache.set(pattern, cached);
     return cached;
   }
-  // Reuses change-guardrail.ts's wildcard-GROUP counting (a `*` here matches the same "any run of chars"
-  // semantics as that glob compiler's `*`, so the same catastrophic-backtracking risk and the same empirically-
-  // safe threshold apply) — an over-complex registry-sourced label_multipliers key degrades to a safe never-match
-  // instead of hanging RegExp.test() on an adversarial near-miss label (#2456). Reachable via the public
-  // score-preview API, the MCP tool, and the per-PR label-audit signal, so one bad registry entry could otherwise
-  // hang scoring for every PR on that repo.
-  if (hasUnsafeWildcardCount(pattern)) {
+  // Reject an over-complex registry-sourced label_multipliers key so it degrades to a safe never-match instead
+  // of hanging RegExp.test() on an adversarial near-miss label (#2456). Reachable via the public score-preview
+  // API, the MCP tool, and the per-PR label-audit signal, so one bad registry entry could otherwise hang
+  // scoring for every PR on that repo. Counting is fnmatch-specific, NOT change-guardrail's path-glob count:
+  // this compiler emits one `.*` per `*` with no `**` pairing (see below), so `**` is TWO backtracking groups
+  // here, not the single `.*` the path compiler collapses it into (#9994) — counting via that predicate would
+  // undercount `**` and admit a glob this compiler builds into a catastrophic-backtracking RegExp. The threshold
+  // itself is the shared MAX_GLOB_WILDCARD_GROUPS, so the two surfaces stay on one empirically-safe boundary.
+  if (fnmatchWildcardGroups(pattern) > MAX_GLOB_WILDCARD_GROUPS) {
     setLabelPatternRegExpCacheEntry(pattern, LABEL_PATTERN_NEVER_MATCHES);
     return LABEL_PATTERN_NEVER_MATCHES;
   }

packages/loopover-engine/src/scoring/label-match.ts

@@ -34,7 +34,10 @@ export function canonicalize(value: string): string {
 // protected automatically rather than needing to separately remember the risk. The boundary is set at the
 // highest GROUP count proven safe by the benchmark above (2) — a boundary that itself sits inside the
 // empirically dangerous range would defeat the point of a cap.
-const MAX_GLOB_WILDCARD_GROUPS = 2;
+// Exported (#9994) so label-match.ts's fnmatch compiler applies the SAME empirically-safe threshold rather
+// than redeclaring its own literal — a second, independently-chosen cap is exactly the drift the
+// hasUnsafeWildcardCount export below warns about.
+export const MAX_GLOB_WILDCARD_GROUPS = 2;
 
 /** Count `*` GROUPS in `glob` — a `**` pair is ONE group (it compiles to a single `.*`, see globToRegExp), not
  *  two. Mirrors globToRegExp's own tokenization exactly (including consuming a `**`'s trailing `/`) so the count

packages/loopover-engine/src/signals/change-guardrail.ts

@@ -0,0 +1,34 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+
+import {
+  clearLabelPatternRegExpCacheForTest,
+  labelMatchesPattern,
+  labelPatternRegExpCacheKeysForTest,
+} from "../dist/scoring/label-match.js";
+
+// #9994: the fnmatch compiler emits one `.*` per `*` and has no `**` concept, so `*a**b` compiles to THREE
+// `.*` groups. The old guard reused change-guardrail's path-glob counter, which scores a `**` pair as ONE
+// group, undercounting `**` and admitting a pattern this compiler builds into a catastrophic-backtracking
+// RegExp. Counting is now fnmatch-specific (one per raw `*`), so `**`-containing patterns over the cap are
+// rejected — they fail SAFE toward no-multiplier (never match).
+test("#9994: a pattern whose COMPILED groups exceed the cap via `**` is rejected (never matches)", () => {
+  clearLabelPatternRegExpCacheForTest();
+  assert.equal(labelMatchesPattern("anything", "*a**b"), false); // 3 stars → 3 groups → rejected
+  assert.equal(labelMatchesPattern("x/y", "**/**"), false); // 4 stars → 4 groups → rejected
+});
+
+test("#9994: the preserved 2-group and non-`*` cases still match exactly", () => {
+  assert.equal(labelMatchesPattern("type:bug-fix", "type:*"), true);
+  assert.equal(labelMatchesPattern("priority:1", "priority:?"), true); // `?` is not a counted group
+  assert.equal(labelMatchesPattern("a-b-c", "a*b*c"), true); // 2 stars, at the cap
+  assert.equal(labelMatchesPattern("kind:bug", "kind:[bc]ug"), true); // classes are not counted groups
+});
+
+test("#9994: a rejected over-complex pattern is still cached (repeated read served from cache)", () => {
+  clearLabelPatternRegExpCacheForTest();
+  assert.equal(labelMatchesPattern("anything", "*a**b"), false);
+  assert.ok(labelPatternRegExpCacheKeysForTest().includes("*a**b"));
+  assert.equal(labelMatchesPattern("something-else", "*a**b"), false); // cache-hit arm, still false
+  assert.equal(labelPatternRegExpCacheKeysForTest().filter((k) => k === "*a**b").length, 1);
+});

packages/loopover-engine/test/label-match.test.ts

@@ -960,9 +960,12 @@ NOVELTY_BONUS_SCALAR = 3
     // Regex metacharacters in a literal key stay literal: `.` matches only a dot, not any char.
     expect(labelMultiplierFor({ "v1.0": 1.1 }, ["v1.0"])).toBe(1.1);
     expect(labelMultiplierFor({ "v1.0": 1.1 }, ["v1x0"])).toBe(1);
-    // `**/` counts as one wildcard group and matches across path-like label segments.
+    // #9994: this fnmatch compiler counts one wildcard group per raw `*` (it has no `**`-is-one-group rule —
+    // that is the PATH compiler's semantics), so `**/bug` and `**bug` are 2 groups (at the cap → still
+    // compile and match), but `public/**/*.json` is THREE (`**` + `*`) and is now rejected as over-complex,
+    // failing SAFE toward no multiplier — where the old path-glob count wrongly scored it as 2 and matched it.
     expect(labelMultiplierFor({ "**/bug": 1.45 }, ["feature/bug"])).toBe(1.45);
-    expect(labelMultiplierFor({ "public/**/*.json": 1.2 }, ["public/release/config.json"])).toBe(1.2);
+    expect(labelMultiplierFor({ "public/**/*.json": 1.2 }, ["public/release/config.json"])).toBe(1);
     expect(labelMultiplierFor({ "**bug": 1.35 }, ["feature-bug"])).toBe(1.35);
     // When several patterns match, the highest multiplier wins (mirrors upstream `max(...)`).
     expect(labelMultiplierFor({ "kind/*": 1.1, "*/bug": 1.6 }, ["kind/bug"])).toBe(1.6);
@@ -2150,4 +2153,30 @@ describe("label pattern matcher memoization (#2106)", () => {
     expect(labelMatchesPattern("type-bug-fix", "type-*-*")).toBe(true);
     expect(labelMatchesPattern("type-bug", "type-*-*")).toBe(false);
   });
+
+  it("#9994: a `**`-containing pattern is counted by its COMPILED groups (one per raw *), not the path-glob `**`-is-one rule, so it is rejected", () => {
+    // The fnmatch compiler emits one `.*` per `*` and has no `**` concept, so `*a**b` compiles to THREE `.*`
+    // groups. change-guardrail's path counter scored it as 2 (a `**` pair = one group) and wrongly ACCEPTED it,
+    // admitting a pattern this compiler builds into a catastrophic-backtracking RegExp. All three fail SAFE
+    // toward no-multiplier (never matches).
+    clearLabelPatternRegExpCacheForTest();
+    expect(labelMatchesPattern("anything", "*a**b")).toBe(false); // 3 stars → 3 compiled groups → rejected
+    expect(labelMatchesPattern("x/y", "**/**")).toBe(false); // 4 stars → 4 compiled groups → rejected
+    expect(labelMatchesPattern("abc", "a**b**c")).toBe(false); // 4 stars → rejected
+
+    // The preserved 2-group cases and non-`*` metacharacters still compile and match exactly as before.
+    expect(labelMatchesPattern("type:bug-fix", "type:*")).toBe(true);
+    expect(labelMatchesPattern("priority:1", "priority:?")).toBe(true); // `?` is not a counted group
+    expect(labelMatchesPattern("a-b-c", "a*b*c")).toBe(true);
+    expect(labelMatchesPattern("kind:bug", "kind:[bc]ug")).toBe(true); // classes are not counted groups
+  });
+
+  it("#9994: a rejected over-complex pattern is still cached, so a repeated read is served from the cache", () => {
+    clearLabelPatternRegExpCacheForTest();
+    expect(labelMatchesPattern("anything", "*a**b")).toBe(false);
+    expect(labelPatternRegExpCacheKeysForTest()).toContain("*a**b");
+    // Second read of the same over-complex pattern is served from the cache (cache-hit arm), still false.
+    expect(labelMatchesPattern("something-else", "*a**b")).toBe(false);
+    expect(labelPatternRegExpCacheKeysForTest().filter((k) => k === "*a**b")).toHaveLength(1);
+  });
 });