feat(core): batch-safe hashing with output fingerprinting by FrozenPandaz · Pull Request #34446 · nrwl/nx

FrozenPandaz · 2026-02-13T16:45:25Z

Current Behavior

In batch mode, all task hashes are computed upfront before the batch executor runs any tasks. Tasks with dependentTasksOutputFiles get hashed using whatever dependency outputs happen to be on disk from a previous run. This leads to:

False cache hits: If a dependency's sources changed but its old outputs are still on disk, the dependent task's hash matches a stale cache entry and wrong results are served.
False cache misses: On cold runs with no outputs on disk, the hash is computed without dependency output content and never matches any stored cache entry.

Non-batch mode doesn't have this problem because it uses lazy hashing — tasks with depsOutputs are only hashed after their dependencies complete and fresh outputs exist on disk.

Additionally, the shouldCopyOutputsFromCache and recordOutputsHash methods only worked when the daemon was running. Without the daemon, shouldCopyOutputsFromCache always returned true (always re-copy) and recordOutputsHash was a no-op.

Expected Behavior

Batch mode correctly validates whether dependency outputs on disk match the dependency's current hash before trusting any cache entries. When outputs are stale, cache reads are skipped and tasks are re-hashed after the batch completes with fresh outputs. This validation works with or without the daemon.

How it works

Hash all tasks in the batch (existing behavior)
Validate: For each task with depsOutputs whose dependency is also in the batch, check if the dependency's outputs on disk were produced by its current hash. If not, mark the task as stale.
Skip cache reads for stale tasks
Run the batch
Clear hashes on stale tasks, call hashTasks() again — outputs are now fresh
postRunSteps stores cache entries under the correct hash

Output Fingerprinting (daemon-free fallback)

Previously, output freshness validation only worked with the daemon's in-memory tracking. This PR adds a persistent alternative:

OutputFingerprints (Rust/napi): SQLite-backed table that maps task_hash → fingerprint where fingerprint is a deterministic hash of all output files
hashTaskOutput (Rust/napi): Exposed existing Rust output hashing function to TypeScript — uses rayon for parallel file hashing
Unified outputsHashesMatch: Uses the daemon when available, falls back to comparing the current on-disk fingerprint against the stored DB fingerprint

recordOutputsHash now always persists fingerprints to the DB (in addition to notifying the daemon when available), so subsequent runs can validate outputs even without the daemon.

Run-by-run behavior

Run	Dep outputs on disk?	Outputs match dep hash?	Cache result
1 (cold)	No	No → skip cache	Miss → runs → stores correct hash
2 (same sources)	Yes, from run 1	Yes → trust hash	Hit
N (dep sources changed)	Yes, but stale	No → skip cache	Miss → runs → stores correct hash

Files changed

File	Change
`packages/nx/src/native/tasks/output_fingerprints.rs`	New — DB-backed OutputFingerprints struct
`packages/nx/src/native/tasks/hashers/hash_task_output.rs`	Expose hashTaskOutput via napi
`packages/nx/src/native/tasks/task_hasher.rs`	Import rename
`packages/nx/src/native/tasks/mod.rs`	Register new module
`packages/nx/src/native/db/initialize.rs`	Register new table schema
`packages/nx/src/tasks-runner/task-orchestrator.ts`	Batch validation, unified outputsHashesMatch, recordOutputsHash with DB persistence

Related Issue(s)

Related to #30949

nx-cloud · 2026-02-13T16:45:59Z

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☁️ Nx Cloud last updated this comment at 2026-02-21 01:50:05 UTC

netlify · 2026-02-13T16:55:36Z

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netlify · 2026-02-13T16:57:12Z

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When tasks with dependentTasksOutputFiles are co-batched with their dependencies, hashes are computed using outputs from a previous run that may be stale. This adds a validation step that checks whether dependency outputs on disk match the dependency's current hash, skips cache reads for untrustworthy hashes, and re-hashes after the batch completes with fresh outputs.

Add OutputFingerprints Rust struct backed by SQLite for persisting output file checksums. Expose hashTaskOutput via napi so TypeScript can fingerprint outputs without the daemon. Unify outputsHashesMatch to use daemon when available, falling back to DB fingerprints.

With output fingerprinting, outputs that already match the cache are left in place instead of being re-copied. Update e2e assertions to expect "existing outputs match the cache, left as is" instead of "local cache" when daemon is disabled or outputs are untouched.

Add null checks before calling hashTaskOutput to prevent "Failed to convert JavaScript value Undefined into rust type String" when tasks have no outputs defined (e.g. maven tasks). Also update symlink cache test assertion.

With output fingerprinting enabled for all cache operations (not just batch mode), tasks whose outputs are already on disk now correctly report "existing outputs match the cache" instead of "local cache". Updated e2e assertions across cache, run, ng-add, and nx-init-angular tests to expect the new status when outputs haven't been deleted.

Wrap identifyTasksWithStaleDepsOutputs and getInputs in try-catch so that targets without proper input configuration (e.g. inferred maven targets) don't crash the entire batch execution.

hashTasks filters out tasks that already have a hash. The previous code cleared hashes on the result copies (created by runBatch via spread) but called hashTasks on batch.taskGraph which holds the originals — still with their hashes. This caused hashTasks to skip them entirely, leaving the copies with undefined hashes that crashed napi when passed to cache.put. Clear hashes on the originals so hashTasks picks them up, then sync the fresh hashes back to the result copies.

The testCompile target hash was missing src/test/java/**/*.java because CacheConfig used the wrong parameter name for the compiler plugin's test source roots. Also removes an unnecessary fallback in MavenExpressionResolver that masked the issue.

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Important

At least one additional CI pipeline execution has run since the conclusion below was written and it may no longer be applicable.

Nx Cloud has identified a possible root cause for your failed CI:

The e2e-gradle test failure appears to be an environment_state issue rather than a code defect. The failing test is in a project not modified by our PR (e2e-gradle is not in touched_projects), the error occurs in an unchanged test file, and the similar-task-failure-detector confirms this error pattern doesn't exist on master. The process execution failure when running nx show projects has no logical connection to our batch hashing and output fingerprinting changes in task-orchestrator.ts.

No code changes were suggested for this issue.

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FrozenPandaz force-pushed the fix-batch-hash branch 3 times, most recently from cf36e18 to 71d9c98 Compare February 13, 2026 16:52

FrozenPandaz changed the title ~~fix(core): validate batch task hashes against stale dependency outputs~~ feat(core): batch-safe hashing with output fingerprinting Feb 13, 2026

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FrozenPandaz force-pushed the fix-batch-hash branch 2 times, most recently from ef9a35e to 92f349b Compare February 20, 2026 16:11

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FrozenPandaz force-pushed the fix-batch-hash branch 2 times, most recently from 940564b to b74c720 Compare February 20, 2026 19:57

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FrozenPandaz force-pushed the fix-batch-hash branch from ef3c9b5 to 309264d Compare February 20, 2026 21:58

FrozenPandaz added 9 commits February 20, 2026 18:16

chore(maven): remove reset because of this issu9e

9d7f602

fix(core): guard hashTaskOutput against undefined outputs

bc5c56b

Add null checks before calling hashTaskOutput to prevent "Failed to convert JavaScript value Undefined into rust type String" when tasks have no outputs defined (e.g. maven tasks). Also update symlink cache test assertion.

fix(core): make batch stale-dep detection resilient to errors

2b14d06

Wrap identifyTasksWithStaleDepsOutputs and getInputs in try-catch so that targets without proper input configuration (e.g. inferred maven targets) don't crash the entire batch execution.

FrozenPandaz force-pushed the fix-batch-hash branch from ebc28bc to a270277 Compare February 20, 2026 23:17

nx-cloud bot reviewed Feb 21, 2026

View reviewed changes

fix(maven): fix inputs for maven:test

fd6015c

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feat(core): batch-safe hashing with output fingerprinting#34446

feat(core): batch-safe hashing with output fingerprinting#34446
FrozenPandaz wants to merge 10 commits intomasterfrom
fix-batch-hash

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FrozenPandaz commented Feb 13, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Current Behavior

Expected Behavior

How it works

Output Fingerprinting (daemon-free fallback)

Run-by-run behavior

Files changed

Related Issue(s)

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