fix(bake): strip model-conditional betas from baked base set

CHANGELOG.md

@@ -11,6 +11,8 @@ checklist.
 
 ## [Unreleased]
 
+- **fix(bake): strip model-conditional betas from the baked base set (issue #484 follow-up).** The drift *detection* fix made `computeDrift` ignore the `betaForModel()`-managed betas, but the *bake* path (`capture-and-bake.mjs`) still wrote the raw captured `anthropic_beta` verbatim — so an auto-rebake from a capture that rode `context-1m-2025-08-07` (the drift runner's capture does) re-introduced it to the base, undoing #475. The bake now runs the captured beta header through `stripModelConditionalBetas` (new export, shares `MODEL_CONDITIONAL_BETAS`) before writing, so a rebake produces only the real diff (e.g. dropping `afk-mode-2026-01-31`) and never re-adds the per-request betas. `test/bake-drift-report.mjs` +2 cases (88/88).
+
 - **fix(drift-check): stop the perpetual false-positive auto-rebake loop (issue #484).** `cc-drift-template-watch.yml` re-fired every cycle because `computeDrift` compared the live `--check` capture against the bundle without accounting for two structural, non-drift differences: (1) the **model-conditional betas** `context-1m-2025-08-07` and `fallback-credit-2026-06-01`, which `betaForModel()` appends per-request and the baked base deliberately omits — so a capture carrying them read as "beta added" forever; and (2) the **environment-specific memory directory path** in the system prompt, which differs on every cross-OS bake (e.g. a Windows-baked bundle vs the Linux drift runner's `/root/...` capture). `computeDrift` now filters the `betaForModel()`-managed betas from both sides (new export `MODEL_CONDITIONAL_BETAS`) and normalizes the memory path before the system_prompt diff (new export `normalizeMemoryPath`). Genuine base-beta changes (e.g. `afk-mode` add/removal) and real prompt edits still surface. `test/bake-drift-report.mjs` extended (+6 cases, 81/81). Closes the regression-rebake loop that produced #476 and #483.
 
 ## [4.8.55] - 2026-06-09

scripts/capture-and-bake.mjs

@@ -41,7 +41,7 @@ import { fileURLToPath } from 'node:url';
 import { captureLiveTemplateAsync, findInstalledCC } from '../dist/live-fingerprint.js';
 import { scrubTemplate, findUserPathHits } from '../dist/scrub-template.js';
 import { PLATFORM_ONLY_TOOLS } from '../dist/cc-template.js';
-import { computeDrift, formatDriftReport, interpretDrift, formatDriftSummary } from './drift-report.mjs';
+import { computeDrift, formatDriftReport, interpretDrift, formatDriftSummary, stripModelConditionalBetas } from './drift-report.mjs';
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
 const repoRoot = join(__dirname, '..');
@@ -70,6 +70,17 @@ if (!captured) {
 log(`captured: CC v${captured._version}, ${captured.tools.length} tools, ${captured.system_prompt.length} char system prompt`);
 
 const scrubbed = scrubTemplate(captured);
+// Strip the model-conditional betas betaForModel() appends per-request
+// (context-1m on [1m] requests, fallback-credit on fable) so the baked BASE set
+// matches #475's design — they're re-added per-request at runtime, not part of
+// the canonical base. Without this, a capture that rode one (the drift runner's
+// capture carries context-1m) would re-introduce it to the base on every rebake,
+// undoing #475. Same set the drift detector ignores (drift-report.mjs).
+const beforeBeta = scrubbed.anthropic_beta || '';
+scrubbed.anthropic_beta = stripModelConditionalBetas(beforeBeta);
+if (scrubbed.anthropic_beta !== beforeBeta) {
+  log(`stripped model-conditional beta(s) from baked base: ${beforeBeta} → ${scrubbed.anthropic_beta}`);
+}
 scrubbed._source = 'bundled';
 scrubbed._supportedMaxTested = captured._version;
 

scripts/drift-report.mjs

@@ -20,6 +20,22 @@ export const MODEL_CONDITIONAL_BETAS = new Set([
   'fallback-credit-2026-06-01', // FABLE_FALLBACK_CREDIT_BETA — appended for fable requests only
 ]);
 
+/**
+ * Strip the model-conditional betas (the ones betaForModel() appends per-request)
+ * from a comma-joined beta string. Used by the BAKE path (capture-and-bake.mjs) so
+ * the canonical base set written to cc-template-data.json never carries them — a
+ * live capture that happened to ride them (e.g. a `[1m]` request carrying
+ * context-1m) would otherwise re-introduce them to the base on every rebake,
+ * undoing #475's design. Mirrors the filter computeDrift applies for detection.
+ */
+export function stripModelConditionalBetas(beta) {
+  return (beta || '')
+    .split(',')
+    .filter(Boolean)
+    .filter((b) => !MODEL_CONDITIONAL_BETAS.has(b))
+    .join(',');
+}
+
 /**
  * Collapse the environment-specific CC memory directory path to a placeholder so
  * a cross-OS bake doesn't read as system_prompt drift: the bundle may be baked on

test/bake-drift-report.mjs

@@ -3,7 +3,7 @@
 // test runner spawns each file via node:test which is fine for imports
 // too, but the existing pattern groups script-imports in serial).
 
-import { unifiedDiff, computeDrift, describeTool, formatDriftReport, interpretDrift, formatDriftSummary, MODEL_CONDITIONAL_BETAS, normalizeMemoryPath } from '../scripts/drift-report.mjs';
+import { unifiedDiff, computeDrift, describeTool, formatDriftReport, interpretDrift, formatDriftSummary, MODEL_CONDITIONAL_BETAS, normalizeMemoryPath, stripModelConditionalBetas } from '../scripts/drift-report.mjs';
 
 let pass = 0;
 let fail = 0;
@@ -389,6 +389,30 @@ header('37. computeDrift — real prompt edit still flagged despite path normali
   check('diff shows the real edit, not the path', d[0].detail?.some((l) => /CHANGED/.test(l)) && !d[0].detail?.some((l) => /\.claude/.test(l)));
 }
 
+// ──────────────────────────────────────────────────────────────────────
+// issue #484 — the BAKE must strip model-conditional betas so a rebake can't
+// re-introduce them to the base (undoing #475). Mirrors the detection filter.
+header('38. stripModelConditionalBetas — removes context-1m / fallback-credit, keeps the rest');
+{
+  const captured = 'claude-code-20250219,context-1m-2025-08-07,interleaved-thinking-2025-05-14,effort-2025-11-24';
+  const baked = stripModelConditionalBetas(captured);
+  check('context-1m removed', !baked.includes('context-1m-2025-08-07'));
+  check('base betas preserved in order', baked === 'claude-code-20250219,interleaved-thinking-2025-05-14,effort-2025-11-24');
+  check('fallback-credit removed too', stripModelConditionalBetas('claude-code-20250219,fallback-credit-2026-06-01') === 'claude-code-20250219');
+  check('no-op when no managed betas present', stripModelConditionalBetas('claude-code-20250219,afk-mode-2026-01-31') === 'claude-code-20250219,afk-mode-2026-01-31');
+  check('empty / undefined safe', stripModelConditionalBetas('') === '' && stripModelConditionalBetas(undefined) === '');
+}
+
+header('39. bake-vs-check consistency — a re-baked base no longer drifts from the capture on managed betas');
+{
+  // Simulate: live capture carries context-1m (rode a [1m] request); the bake
+  // strips it; computeDrift(baked-base, same-capture) must NOT re-flag it.
+  const capture = makeTemplate({ anthropic_beta: 'claude-code-20250219,context-1m-2025-08-07,effort-2025-11-24' });
+  const baked = makeTemplate({ anthropic_beta: stripModelConditionalBetas(capture.anthropic_beta) });
+  check('baked base omits context-1m', !baked.anthropic_beta.includes('context-1m'));
+  check('no beta drift between baked base and the capture it came from', computeDrift(baked, capture).length === 0);
+}
+
 // ──────────────────────────────────────────────────────────────────────
 console.log(`\n${pass} pass, ${fail} fail`);
 process.exit(fail === 0 ? 0 : 1);