[Brooooooklyn]

Problem

After a platform rollout, existing projects can return HTTP 500 for cached hashed assets without an application redeploy. Commit 5c0b5ba added a header deletion in finalizeAsset, but Cloudflare Cache API responses have immutable headers. When no header rule matches, applyHeaderRules returns that original response and the deletion throws Can't modify immutable headers.

The actual dispatcher reproduces this in Miniflare/workerd: the first request returns 200, then cache hits return 500. This matches the affected voidzero.dev routing and reported recovery after platform rollback; historical incident logs were unavailable, so incident attribution remains based on the reproduction and configuration.

Change

Remove the internal shared-cache marker from the writable client response already constructed by meter. Preserve the marker in the stored cache entry and avoid modifying the immutable cached response.

Add real Workers Cache API regressions under platform/packages/dispatch/test/runtime/, covering absent, unmatched, and matched header rules. Each verifies repeated cache hits, unchanged origin request counts, response content and caching headers, and removal of the internal marker. The existing mutable response mocks did not expose this failure.

The regressions run in the existing platform-unit project and Platform CI. The dispatch typecheck command checks the Node-based runtime harness separately from the Worker source to keep their global types isolated.

Validation

• Before the fix, the new no-rule and unmatched-rule cases fail with HTTP 500; all three cases pass after the fix.
• Focused dispatcher/runtime tests: 256 passed. vp test run --project 'platform-*' platform/packages/dispatch/test/runtime/asset-cache.test.ts also passes all three runtime cases at their final location.
• Platform and SDK typechecks, platform type-aware lint, focused lint, formatting, and diff checks pass.
• Full tests: 551 files passed, 10,413 tests passed, 47 skipped; one integration suite failed during setup because local migration state references missing 20260913054327_elite_betty_ross.sql.
• vp run check remains blocked by a missing compiler dependency in the ignored local playground-local/deploy-verify app. This blocker is outside the changed code.

No production deployment or app redeployment was performed.

[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-22T14:07:35.022776Z	84d7791	New commits

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[chatgpt-codex-connector]

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Reviewed commit: 7e13837dbe

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