fix(bench): dep-bump fixture should reflect post-ignore-filter content (#845)

.bench/baseline.json

@@ -1,5 +1,5 @@
 {
-  "capturedAt": "2026-05-06T00:29:28.140Z",
+  "capturedAt": "2026-05-06T00:45:56.229Z",
   "node": "v22.13.0",
   "platform": "darwin-arm64",
   "options": {
@@ -13,7 +13,7 @@
       "fixture": "tiny",
       "fileCount": 5,
       "approxTokens": 790,
-      "durationMs": 2,
+      "durationMs": 1,
       "llmCalls": 0,
       "llmTotalMs": 0,
       "llmTotalPromptTokens": 0
@@ -22,18 +22,18 @@
       "fixture": "medium",
       "fileCount": 25,
       "approxTokens": 36150,
-      "durationMs": 31124,
+      "durationMs": 31137,
       "llmCalls": 20,
-      "llmTotalMs": 106333,
+      "llmTotalMs": 106348,
       "llmTotalPromptTokens": 34237
     },
     {
       "fixture": "large",
       "fileCount": 50,
       "approxTokens": 83410,
-      "durationMs": 72151,
+      "durationMs": 72093,
       "llmCalls": 41,
-      "llmTotalMs": 244112,
+      "llmTotalMs": 244101,
       "llmTotalPromptTokens": 74197
     },
     {
@@ -42,23 +42,23 @@
       "approxTokens": 17600,
       "durationMs": 15967,
       "llmCalls": 11,
-      "llmTotalMs": 54726,
+      "llmTotalMs": 54727,
       "llmTotalPromptTokens": 18937
     },
     {
       "fixture": "refactor",
       "fileCount": 30,
       "approxTokens": 32650,
-      "durationMs": 33994,
+      "durationMs": 33999,
       "llmCalls": 28,
-      "llmTotalMs": 153871,
+      "llmTotalMs": 153888,
       "llmTotalPromptTokens": 52430
     },
     {
       "fixture": "initial-commit",
       "fileCount": 50,
       "approxTokens": 83410,
-      "durationMs": 72291,
+      "durationMs": 72285,
       "llmCalls": 41,
       "llmTotalMs": 245148,
       "llmTotalPromptTokens": 74546
@@ -67,19 +67,19 @@
       "fixture": "docs-update",
       "fileCount": 9,
       "approxTokens": 15050,
-      "durationMs": 18563,
+      "durationMs": 18570,
       "llmCalls": 8,
       "llmTotalMs": 56293,
       "llmTotalPromptTokens": 13908
     },
     {
       "fixture": "dep-bump",
-      "fileCount": 3,
-      "approxTokens": 8450,
-      "durationMs": 27158,
-      "llmCalls": 1,
-      "llmTotalMs": 27141,
-      "llmTotalPromptTokens": 19597
+      "fileCount": 2,
+      "approxTokens": 450,
+      "durationMs": 0,
+      "llmCalls": 0,
+      "llmTotalMs": 0,
+      "llmTotalPromptTokens": 0
     }
   ]
 }

src/lib/parsers/default/__fixtures__/index.test.ts

@@ -1,3 +1,5 @@
+import { DEFAULT_IGNORED_EXTENSIONS, DEFAULT_IGNORED_FILES } from '../../../config/constants'
+import { DiffNode } from '../../../types'
 import {
   allFixtures,
   depBumpFixture,
@@ -49,6 +51,31 @@ describe('bench fixtures (#845)', () => {
     expect(firstSnapshot).toBe(secondSnapshot)
   })
 
+  // Guard against the class of mistake that shipped in the prior
+  // dep-bump fixture: any file matching the default ignore list
+  // (lockfiles, node_modules, .map / .lock extensions) would be
+  // stripped before the pipeline ever sees it on a real commit, so
+  // including such a file in a fixture produces bench numbers that
+  // can't translate to user-facing wins. Fail loudly if any fixture
+  // accidentally drifts back into that shape.
+  it('no fixture file matches DEFAULT_IGNORED_FILES or DEFAULT_IGNORED_EXTENSIONS', () => {
+    const offending: string[] = []
+    const collect = (node: DiffNode, fixtureName: string) => {
+      node.diffs.forEach((diff) => {
+        const basename = diff.file.split('/').pop() || diff.file
+        if (DEFAULT_IGNORED_FILES.includes(basename)) {
+          offending.push(`${fixtureName}: ${diff.file} (matches DEFAULT_IGNORED_FILES)`)
+        }
+        if (DEFAULT_IGNORED_EXTENSIONS.some((ext) => diff.file.toLowerCase().endsWith(ext))) {
+          offending.push(`${fixtureName}: ${diff.file} (matches DEFAULT_IGNORED_EXTENSIONS)`)
+        }
+      })
+      node.children.forEach((child) => collect(child, fixtureName))
+    }
+    allFixtures.forEach((fixture) => collect(fixture.rootNode, fixture.name))
+    expect(offending).toEqual([])
+  })
+
   it('refactor scenario includes a rename diff', () => {
     const collectedDiffs: string[] = []
     const walk = (node: typeof refactorFixture.rootNode) => {
@@ -59,10 +86,20 @@ describe('bench fixtures (#845)', () => {
     expect(collectedDiffs.some((diff) => diff.includes('rename from'))).toBe(true)
   })
 
-  it('dep-bump scenario is dominated by a lockfile-shaped modification', () => {
-    const lockfileDiff = depBumpFixture.rootNode.diffs.find((diff) => diff.file.endsWith('.lock'))
-    expect(lockfileDiff).toBeDefined()
-    expect(lockfileDiff?.diff).toContain('diff --git')
-    expect(lockfileDiff?.tokenCount).toBeGreaterThan(1000)
+  it('dep-bump scenario reflects post-filter content (no lockfiles)', () => {
+    // Lockfiles live in DEFAULT_IGNORED_FILES + DEFAULT_IGNORED_EXTENSIONS,
+    // so they're stripped before the pipeline ever sees the diff. The
+    // fixture should mirror what the pipeline would actually receive
+    // for a dependabot-style commit: package.json + CHANGELOG, both
+    // small.
+    const allDiffs: typeof depBumpFixture.rootNode.diffs = []
+    const walk = (node: typeof depBumpFixture.rootNode) => {
+      allDiffs.push(...node.diffs)
+      node.children.forEach(walk)
+    }
+    walk(depBumpFixture.rootNode)
+    expect(allDiffs.find((diff) => diff.file.endsWith('.lock'))).toBeUndefined()
+    expect(allDiffs.find((diff) => diff.file.endsWith('-lock.json'))).toBeUndefined()
+    expect(allDiffs.find((diff) => diff.file === 'package.json')).toBeDefined()
   })
 })

src/lib/parsers/default/__fixtures__/index.ts

@@ -290,13 +290,17 @@ const DOCS_UPDATE_FILES: FileSpec[] = [
 ]
 
 /**
- * Dep bump: the dependabot-style commit. Tiny content change in
- * package.json, large lockfile delta. Pipeline should mostly
- * skip-trivial these.
+ * Dep bump: the dependabot-style commit. Just the human-readable
+ * surface — package.json + an optional CHANGELOG entry. Lockfiles
+ * (yarn.lock, package-lock.json, pnpm-lock.yaml, *.lock) are in
+ * `DEFAULT_IGNORED_FILES` / `DEFAULT_IGNORED_EXTENSIONS`
+ * (`src/lib/config/constants.ts`), so the pipeline never sees them
+ * on a real `coco commit`. An earlier draft of this fixture
+ * included `yarn.lock` and reported 27 s of LLM work for it; that
+ * was a bench-fixture artifact, not a real-world cost.
  */
 const DEP_BUMP_FILES: FileSpec[] = [
   { path: 'package.json', tokens: 250, shape: 'modification' },
-  { path: 'yarn.lock', tokens: 8000, shape: 'modification' },
   { path: 'CHANGELOG.md', tokens: 200, shape: 'modification' },
 ]