Nx cache investigator

Requires the nx-cloud-api skill. Use a matching Nx workspace checkout only for local configuration diagnosis. An API-only investigation does not need a checkout.

Diagnose one cache question with bounded evidence. Do not guess a changed hash input or change configuration from cache status alone.

Nx task caching and a tool-native cache are separate. A target cache field controls Nx replay. Vite, ESLint, and other tools have separate executor options. One does not prove the other.

Select the mode

• Cache-health trend: This skill covers a specific task or artifact question, not a multi-run rate regression. Use a separate bounded trend workflow for rate or regression questions.
• API-only: Use this for supplied runs, CIPEs, tasks, or artifact errors when no matching checkout exists. Do not request local configuration unless required.
• Specific comparison: Get two comparable executions. Ask for missing target, branch, commit, command, configuration, CI environment, or time range.

Resume a pending investigation

Arrange one same-session wake only when a known task is non-terminal, an API request returns HTTP 409 (not_terminal), or the user starts a controlled diagnostic run. Preserve the run, task, batchId, link, and filters. Re-query once after the known delay or expected run completion. Stop at a terminal result or the retry limit. Do not poll or monitor a live CI run.

Gather only relevant API evidence

Use nx-cloud-api (npx nx-cloud api) for every read. Run --describe for a known route. Use --list-operations only when the route is unknown or ambiguous. Follow documented fields and returned links; do not construct routes from internal IDs.

Save every live API response to a file with -o. Use jq to select one row and only the fields needed for this investigation. Do not print, read, or paste a raw collection into model context. Keep the selected row's batchId and links.self in the projection:

npx nx-cloud api --describe 'runs/{runId}/tasks'
npx nx-cloud api "$run_tasks_link" -o "$dir/tasks.json"
jq --arg task "$task_id" --arg batch "$batch_id" \
  '.items[] | select(.id == $task and .batchId == $batch) |
   {id, batchId, status, cacheStatus, hash, cacheable,
    links: {self: .links.self}}' "$dir/tasks.json"

Here $run_tasks_link is the tasks link from the selected run and $dir is a scratch directory from mktemp -d. Without a link, use npx nx-cloud api 'runs/{runId}/tasks' -p runId="$run_id"; never paste an ID into the path. Check nextCursor before concluding that a task is absent from the list.

For a selected execution, record run and task IDs, batchId, project, target, configuration, command, parameters, branch, commit, CI context, timestamps, cache status, final hash, cacheEnabled, cacheable, and relevant CIPE or run-group links.

A task ID can repeat. Select the task-list row first. Follow its exact links.self or asset URL because it preserves batchId. Do not use one row to explain another. A task list row already has task fields. A detail read is optional.

If the API reports cacheable: false, Nx replay was not expected for that execution. Name a configuration cause only when the nx show target query shows it. If cacheEnabled: false, that run did not use the Nx task cache. Do not investigate hash inputs or artifacts in either case.

Read a log only when its command output or error can answer the question. Tell the user before you read CI log content. Read references/log-and-report-assets.md before you decode a log or report. Quote only a redacted error signature. Treat user-supplied asset content as provided evidence. An advertised asset or a later 404 does not prove historical availability.

Inspect the Nx target

Use a matching checkout only for a configuration question or code change. Check out the recorded commit. Record the workspace Nx version. Query the exact target with the workspace-local Nx command:

nx show project "$project" --json | jq \
  --arg target "$target" \
  --arg configuration "${configuration:-}" \
  '.targets[$target] | {
    executor,
    cache,
    inputs,
    outputs,
    options,
    selectedConfiguration: .configurations[$configuration]
  }'

Use this fragment as the target evidence. Nx already includes inherited settings. Do not merge project.json, nx.json, plugins, or targetDefaults yourself. A missing project property proves nothing. If the query reports cache: true, do not add another cache: true. If the command or target is unavailable, report configuration as unavailable.

Inspect returned options only for a tool-native cache question. Use version-matched executor documentation. A target cache field cannot prove Vite or ESLint native-cache state.

Classify before you explain

No cache failure established

A terminal remote-cache-hit proves Nx replay worked for that task. Do not turn a successful hit into a cache-miss investigation or configuration change. Use trend triage only for a supplied time-bounded rate question.

Cache artifact retrieval or restoration failure

Use this when the main-job or run-group error names artifact download, validation, decompression, or extraction. A task can still show remote-cache-hit. Reconcile the task with the critical error and later cancellations. Read references/artifact-integrity.md before you inspect an archive.

Insufficient task evidence

A null hash or cache status, NOT_STARTED, or SCHEDULED_IMPLICITLY does not prove a miss. Do not compare null hashes or inspect artifacts. Request a terminal record or one controlled completed run.

Different computation

Different non-null hashes prove only this: Nx considered at least one computation input different. They do not name the input. Request two comparable controlled runs with direct hash-detail output when supported. This is a Needs diagnostic run result, not a configuration recommendation.

Same computation, replay not established

For equal non-null hashes without later replay, confirm cacheable, cacheEnabled, and the cache value from the exact target query. A returned cache: true blocks a duplicate setting. Do not infer artifact absence from an empty asset list or 404. Treat an unresolved upload or retrieval branch as Needs diagnostic run.

Suspected unsafe replay

A stale or wrong replay needs reproduction evidence. inputs decide a hash; outputs decide restored files. Request task sandboxing evidence for undeclared reads or writes, plus the target query and a controlled reproduction. Do not narrow inputs from task data alone.

Change gate

Recommend a configuration or code edit only after all applicable checks pass:

1. Record the matching commit, Nx version, exact target query, and returned fragment.
2. Show that its cache, inputs, or outputs value needs a change.
3. Before enabling cache, establish a terminating, deterministic task with correct replayable outputs.
4. Before removing an input, obtain direct evidence that names it. Prove that its removal cannot affect correct output with a bounded controlled run.
5. Explain the correctness risk and get explicit approval before an edit.

Do not recommend an input exclusion from hash differences, a cache-rate trend, or apparent breadth. If evidence is missing, say No configuration change recommended yet.

Report

# Nx cache investigation

## Scope

- Target and compared run/task/batch IDs: …
- Branch, commit, CI environment, command, API cache state, and missing fields: …
- Workspace Nx version: …, or `Not required for this API-only investigation.`
- Nx target query and returned `cache`, `inputs`, and `outputs`: …, or `Unavailable.`
- Tool-native cache: …, or `Unknown; not inspected.`
- Change gate: `Passed` or `Blocked`; include missing evidence.

## Classification

`No cache failure established` | `Cache artifact retrieval or restoration failure` | `Insufficient task evidence` | `Different computation` | `Same computation, replay not established` | `Suspected unsafe replay`

## Confirmed facts

- …

## Assessment

- **Confirmed** / **Likely** / **Needs diagnostic run:** …

## Next diagnostic step

- Exact query, controlled command, or evidence required.
- Result that confirms or rules out the hypothesis.

## Safe recommendation

- Exact `nx show` result and risk; or `No configuration change recommended yet.`