Debug E2E Test

Start from a test name (not a CI run), find its recent distinct failure modes, investigate one, falsify a root-cause mechanism, and land on fix-the-test vs. file-a-bug with the action to match. This is an orchestrator: deterministic work lives in scripts/, and detailed procedures live in references/ that you read only when a stage needs them.

Editing this skill: this file holds the invariant, the reference holds the mechanism. Restating a mechanism here makes two copies that drift apart silently.

When to use

You picked up one specific e2e test that is failing or flaking, and want its evidence without hunting for it by hand. Two entries, one triage. They differ only in where the evidence comes from; everything from "read the summary" onward is identical.

Pick local when the engineer just produced the failure or says "locally"; pick CI when they name a test CI is failing. When they said neither, don't ask -- look: run collect-local-evidence.js --test '<what they named>' (drop --test if they named nothing), and take the local entry if it returns ok (that call is the local entry's first step), the CI entry otherwise. They compose -- a local dig that needs a rate runs the history query afterwards, and a CI diagnosis reproduces locally in the verification half.

This is the debugging process for this case. Don't layer a general debugging workflow on top of it -- the rules below (one pattern at a time, a falsifiable mechanism, evidence ruled in and out) are that discipline. If you arrived here mid-way through another one, drop it and restart from the evidence; a hypothesis formed before the evidence was read is the thing this skill exists to prevent.

Not this skill: a test still being written or edited (author-e2e-tests); a whole run's failures or a run ID/URL (e2e-failure-analyzer); a Vitest or extension-host failure.

Non-negotiable rules

These hold on both entries unless a line names one.

• Zero runs is never a clean result (CI) -- only nonzero runs with no failure patterns is. No local artifacts is not a dead end (local) -- it means the test hasn't run yet, so it ends in an offer to run it.
• Resolve the test identity with resolve-test-key.js, never by hand; when it returns candidates instead of a resolution, ask which test before querying. The local entry needs this only to build a run command.
• Investigate one selected pattern at a time (CI); ask which when there's more than one. Never fetch evidence for a pattern the engineer didn't select -- ask first, even to check a side theory about how patterns relate.
• Never run a test in the foreground. Use Bash run_in_background: true and tail the log. A foreground call lasting minutes blocks delivery of the engineer's messages until it returns, so "it's hung, stop it" cannot reach you mid-run and you cannot TaskStop the run. This matters most here: debugging means watching a run you may well want to abandon.
• Fetch one representative occurrence first; a second only for a listed reason in references/evidence-escalation.md -- name which.
• Agree the fix approach before the first edit, the same way you agree the pattern before fetching evidence.
• Escalate evidence only to answer a concrete question, and show the evidence block before you act on it. Large output stays on disk and out of the conversation; how the read is delegated is references/evidence-escalation.md.
• Never increase a timeout or add an arbitrary wait as the fix.
• Never claim a flaky test is fixed on one green run.
• A previous merged fix must be checked against subsequent failures, and that check reported as four lines, not a triage report (references/prior-triage.md).
• Root-cause claims cite observed evidence and the alternatives ruled out.
• Checkpoint at every phase transition (CI). The local entry starts one only once it escalates (references/local-evidence.md).

Requirements

• Claude Code, run from a Positron checkout: the scripts resolve the repo root from their own location and keep triage state in the shared git dir.
• On PATH: node and git. The CI entry additionally needs gh (authenticated); the local entry needs neither gh nor a network.
• Both entries run on Windows. The one step that does not is escalating into the e2e-failure-analyzer scripts, which shell out to unzip (references/evidence-escalation.md). Nothing in this skill needs unzip: local evidence reads traces with yauzl instead.
• CI entry only: E2E_INSIGHTS_API_KEY set, or present in the repo-root .env.e2e (the query script falls back to it automatically). Get it from 1Password at op://Positron/E2E_dashboard_api_key/credential; without 1Password access, ask the Positron QA team. triage-history.js pre-flights this and exits with cause: "missing-api-key" plus the setup steps -- relay those steps and stop; this is not a triage finding and there is no degraded mode. A cause: "api-unreachable" is the different case: a key was found, so retry rather than sending the engineer to 1Password.
• Neighbor skills: e2e-failure-analyzer (its e2e-query-history.js and e2e-process-s3.js are invoked directly); at the fix stage positron-pr-helper, author-vitest-tests, author-e2e-tests.

Scripts

Run from the repo root. Flags and output contracts: references/scripts.md. If a script itself breaks, see references/script-fallbacks.md.

Start or resume

/debug-e2e-test "<test>" -- start the CI entry. <test> can be anything that names one test: a leaf title, a spec path, spec.test.ts:41, a full testName|||specPath key, or a dashboard URL. /debug-e2e-test --local -- start the local entry (see below). /debug-e2e-test with no argument -- don't ask which test: run the local collector unfiltered. It ranks failures first and newest first, so it selects the most recent local failure on its own, and names it back to you for confirmation. Only when that finds nothing (no-results) is there a test name to ask for. /debug-e2e-test --resume <triage-id> -- resume. /debug-e2e-test --status -- list saved triages.

On --local (or when the engineer describes a failure they just produced): skip straight to evidence -- no key resolution, no history, no checkpoint.

node .claude/skills/debug-e2e-test/scripts/collect-local-evidence.js

Act on its verdict, then read summaryFile and go to Determine root cause. references/local-evidence.md owns the verdict table, the run-it offer for no-results, what local evidence cannot answer, and when to start checkpointing after all. The rest of this section is the CI entry.

On --resume: run node .claude/skills/debug-e2e-test/scripts/checkpoint.js --triage-id <id> --read, validate it, and continue from phase / nextAction. Do not repeat completed history or evidence work unless the engineer asks to refresh, the saved data is invalid, or the branch/test identity changed.

On --status: node .claude/skills/debug-e2e-test/scripts/checkpoint.js --status.

Otherwise (new triage):

1. Resolve the test identity. Never hand-assemble the key -- pass whatever the engineer gave you (leaf title, spec path, spec.test.ts:41 from a stack trace, full key, or a pasted dashboard URL) straight through:

   node .claude/skills/debug-e2e-test/scripts/resolve-test-key.js '<whatever they gave>'

   It reads the real hierarchy from Playwright (~2s), so the describe nesting is never guessed. Use resolved.testKey when resolved is non-null; when it's null, present candidates and ask which -- do not pick one yourself. On inWorkingTree: false or a non-null note, relay it. If it exits non-zero, read references/history-query.md.

2. Run the history helper:

   node .claude/skills/debug-e2e-test/scripts/triage-history.js \
     --test-key '<testName>|||<specPath>' --lookback-days 14

3. Act on its verdict. stop: true (zero-runs-both, clean) or an error field means stop and report -- read references/history-query.md for what each verdict means. Otherwise continue.

4. Initialize a checkpoint and record the patterns. <id> is the triageId from the history output, used verbatim in every later command -- inventing one silos the checkpoint from the work dir already holding the history and evidence, which is what --resume reads:

   node .claude/skills/debug-e2e-test/scripts/checkpoint.js --triage-id <id> \
     --init --test-key '<key>'

5. Check for prior triage before presenting the table:

   node .claude/skills/debug-e2e-test/scripts/find-prior-triage.js \
     --spec-path '<specPath>' --triage-id <id> \
     --occurrence-shas '["<sha1>","<sha2>"]'

   A non-none verdict changes the plan -- read references/prior-triage.md. A merged fix additionally needs a denominator before "it held" is sayable: re-run the history query with --since-fix <mergedAt> and pass the resulting fixHeld numbers back in. Without them the verdict is too-recent-to-tell by construction, so skipping this step silently downgrades the answer. none is not conclusive -- it matches spec paths, so a POM/helper-only fix never registers. If the failing locator is gone from the working tree, read that file anyway. open-attempt-in-flight means stop and point at the open PR.

6. Present the failure modes as a table (never a run-on sentence). The Rate column comes from each pattern's rates array, never count / totalRuns; Last seen renders lastSeen as 5d ago (Jul 24), or just today at 0d. Include a "Seen on" column whenever two branches were queried:

   #	Failure mode	Count	Rate	Last seen	Environments	Seen on
   A	locator.click timeout: .codicon-maximize	4	100% on feature/x	5d ago (Jul 24)	ubuntu/chromium	feature/x only
   B	toBeVisible() timeout: getByLabel('...')	3	1.9% on main	today	ubuntu/electron	main only

   Count and Rate are cumulative over the lookback, so they cannot separate an acute burst a merged fix already closed from an ongoing drip. A pattern whose daysAgo is stale next to the others is an already-fixed candidate: say so in your recommendation instead of steering the engineer there on count alone.

   When lastSeen.date is null for every pattern, render Last seen as unknown and give the recency read from onset instead ("Started yesterday"). Report a dateless column as a gap in that one read, never as a reason the already-fixed question can't be asked.

7. Ask which pattern to prioritize whenever the table has more than one row. Give your own read ("A is dominant at 99% -- start there, or focus on B?") but let the engineer decide; they may already know which failure they care about. A single pattern needs no choice. Save the selection to the checkpoint (--set selectedPattern=A --set phase=pattern-selected).

Investigate the selected pattern

Local entry: collect-local-evidence.js already wrote your summary.md -- start at step 2. Steps 2 and 3 are shared.

1. Fetch evidence for the pattern's representative occurrence:

   node .claude/skills/debug-e2e-test/scripts/fetch-pattern-evidence.js \
     --report-url '<representativeOccurrence.report_url>' \
     --triage-id <id> --pattern A

   (The helper strips the index.html#?testId= fragment and filters the report to this one test itself.)
2. Read the generated summary.md (failure, timeline tail, sibling tests, error-shaped logs, unresolved questions). Read only the summary first.
3. State the concrete questions that remain. Before each escalation past the summary, show the evidence block (Question / Next artifact / Reason) defined in references/evidence-escalation.md -- can't fill all three fields, don't escalate. Show it, then dispatch the escalation as a subagent with that block as its prompt; don't open the artifact yourself, and don't let the block reach only the subagent. That reference owns the block format, the dispatch contract, the ladder, the reasons a second occurrence is allowed, raw-log spelunking, and 403/null handling.
4. Save phase=evidence-gathered to the checkpoint.

Determine root cause

This is a collaborative dig, not a rubber-stamped verdict. Read references/triage-rubric.md -- the taxonomy, the dismissal bar, what each evidence type proves, and the locator-drift decision.

State: the observed mechanism (citing trace step / log line / snapshot); what the evidence rules in and out; the surviving alternatives; and a fix that could plausibly change the failure rate (a fix that couldn't is not a fix -- keep digging).

Delegate cross-file tracing to an Explore subagent only after the evidence names a concrete symbol / selector / event / subsystem -- under the same cap and forbidden list as an evidence read ("Delegate the read" in references/evidence-escalation.md).

Then agree the fix approach, before the first edit. Table the plausible fixes (approach / what it changes / risk) with your recommendation and let the engineer pick -- editing before the pick burns a context on a rejected approach. Carry the pick as diagnosis.fixApproach.

Save the diagnosis to the checkpoint (--patch a diagnosis object) and set phase=hypothesis-ready. Include the fields record-diagnosis.js renders (confidence, summary, targetedFailure, signal, hypothesis, optional supersedes) plus fixApproach from the gate above -- see references/diagnosis-block.md for what each must contain.

Reproduce and fix

Checkpoint the diagnosis before implementing, then set phase=implementation. That is the required step: history, evidence, and working-tree edits are all durable on disk, so the invariant to hold is that implementation could start from the checkpoint alone -- a fixApproach specific enough to act on without re-reading the evidence.

That invariant is what makes a clear safe, so you never have to propose one: the engineer clears when they want and --resume <id> picks the triage back up.

Read references/reproduction.md now -- it owns keeping this phase's context small, project choice, race verification, and the RED bar you must hold when author-vitest-tests writes a lower-level regression test (that skill drives toward green; it does not enforce RED-first).

Record the result and close out

Every triage ends by declaring an outcome and recording its diagnosis -- this is not optional, and checkpoint.js refuses phase=done until it's satisfied. On the local entry there is no checkpoint to gate you, so the rule is yours to keep: a PR or an issue still gets the block. A local dig that ends with a fix and no artifact ends when the fix is verified -- say so and stop; don't manufacture a checkpoint to close. The outcome spans two axes (what you found x what you did):

outcome is the primary artifact -- a secondary note (e.g. mentioning a product race in the backlog while you fix the test) does not change it. When a triage genuinely produces two artifacts, the block goes on both and outcome still names one: references/diagnosis-block.md.

A returning sub-tool is not the end of the triage -- opening the PR via positron-pr-helper or a passing author-vitest-tests run resolves a step. Once the PR/issue exists:

1. record-diagnosis.js --triage-id <id> --pr <n> --outcome <fix-test|fix-product> (or --issue <n> --outcome file-issue) appends the block and sets outcome + outcomeRef + diagnosisBlockRecorded in one call. For a no-op, skip this and checkpoint.js --set outcome=no-op --set outcomeReason="..." instead.
2. checkpoint.js --set phase=done.