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Turbopack Persistent Cache Causes Slower Builds And OOM After Pipeline Changes

When a compile pipeline change (e.g. turbopack.rules loader, reactCompiler) invalidates most of the module graph, `next build` over an existing `.next/cache` is significantly slower and uses more memory than a cold build, often causing OOM on constrained CI. The persistent cache retains stale entries during rebuild and lacks mass-invalidation fallback.

criticalConfidence 85%Next.js Affected V16.3.6 Affected V16.4.0-Canary.57

Origin Analysis

Turbopack's filesystem cache does not detect mass invalidation; invalid entries remain in memory/on disk while new artifacts are produced, leading to duplicate graph state and memory bloat. `turbopackGc` only cleans after the build, not during, so peak memory is unaffected. There is no mechanism to clear or bypass the cache when a large fraction of modules change.

1. Create app with many routes/components importing from a macro expanded via `turbopack.rules` and `condition.content`; enable `reactCompiler` and `experimental.turbopackRustReactCompiler`. 2. Run `LOADER=off next build` from empty `.next` (cold). 3. Run `LOADER=on next build` keeping `.next/cache` from step 2 (warm over old pipeline). 4. Run `LOADER=on next build` from empty `.next` (cold new pipeline). Compare time and peak memory: warm is slower and higher.

Fixing Code Block

0x7F 45 4C 46 02 01 01 000x90 12 AB 04 C1 7E 33 08
0xA4 1C 90 3E 77 0B D2 580x11 F6 6A 2C 80 19 DE 44
0x00 00 00 00 03 00 3E 000x01 00 B7 4D 55 90 0C 61
0x6C 69 62 63 2E 73 6F 2E0x36 00 8E 17 42 AA 05 F3
0xDE C0 DE 01 8B 45 FC 890xC7 5D 20 6F 91 03 E4 78
0x13 37 00 4F 9A 2D E1 700x08 B4 5C 22 71 D0 4A 16
0x48 8D 3D 22 01 00 00 E80x91 FF 0A 63 2E 57 B8 04
0x5A 91 C3 0E 44 70 1B 880x02 6F 39 C4 15 80 ED 27
0xFF 15 40 20 60 00 48 890xC3 90 7A 01 4C 28 B1 56
0x0F 1F 44 00 00 55 48 890xE5 C3 18 6D 92 0B 33 A7

Edge Case Audit

Clearing the cache on any config change discards all incremental build benefits after pipeline changes, which may increase build times for small changes. In a monorepo or with frequent config tweaks this may negate caching. Do not run concurrently across multiple processes targeting the same `.next` directory—use a lock or ensure CI jobs are serialized. To roll back, remove the script and restore the previous `.next/cache` from backup; the cache will naturally rebuild. Test on Vercel where cache is restored automatically: add this step before `next build` in the build command.