Hunt: Root Cause Before Fix

Hunt: Diagnose Before You Fix

Prefix your first line with 🥷 inline, not as its own paragraph.

A patch applied to a symptom creates a new bug somewhere else.

Outcome Contract

• Outcome: the root cause is identified before any fix is applied.
• Done when: one sentence explains the cause, every observed symptom fits it, and the fix or handoff is verified against a reproducible check.
• Evidence: source trace, repro command or UI path, logs or state, targeted test/build output, and runtime evidence for UI or native defects.
• Output: root cause, fix or handoff, verification result, and any unswept sibling risks.
• Authorization: "diagnose", "investigate", "why", "look into", "排查", "看看", or equivalent is report-only. Apply a fix only when the current request explicitly asks to fix, change, implement, or optimize, or when an authorization to do so is still in force for this same unfinished task with the action, scope, and goal unchanged; root-cause proof is still required first. A fix authorization never carries commit, push, publish, or any destructive action with it.

Do not touch code until you can state the root cause in one sentence:

"I believe the root cause is [X] because [evidence]."

Name a specific file, function, line, or condition. "A state management issue" is not testable. "Stale cache in useUser at src/hooks/user.ts:42 because the dependency array is missing userId" is testable. If you cannot be that specific, you do not have a hypothesis yet.

Diagnosis Signals

Hypothesis quality gate: the hypothesis must explain every observable symptom, not just the one reported first; partial coverage is a symptom-level guess, not a root cause. A symptom the reporter waves off as unrelated is still a symptom the hypothesis has to cover. For timing-dependent issues (flicker, intermittent failure, race), reproduce reliably before diagnosing.

Rationalization smells: "I'll just try this" = no hypothesis, write it first. "I'm confident" = run the instrument that proves it. "Probably the same issue" = re-read the execution path from scratch. "It works on my machine" = enumerate env differences before dismissing. "One more restart" = read the last error verbatim; never restart more than twice without new evidence.

Durable Context Preflight

See references/durable-context.md for when durable context is in scope and the redaction gate that applies before any of it becomes a durable rule.

For /hunt: durable context is hypothesis fuel only, and current code, logs, and repro evidence override memory. It never replaces a fresh root-cause sentence or a reproducible symptom list.

Bisect Mode

Activate when: "以前是好的", "之前是好的", "used to work", "上一次提交还是对的", "broke after update", or the user remembers a specific good commit or version.

• Protect the user's worktree first: git status --short --branch -uall. Any modified, staged, or untracked files mean no bisect in the current checkout: run it in a temporary detached worktree and remove that worktree when done. If a temporary worktree is impossible, stop and ask for explicit cleanup/stash approval.
• If the last-good version is only a few releases back, git diff <last-good>..HEAD -- <suspect path> and read the delta first. The regression is usually visible there at a fraction of a bisect's cost; fall through to bisect only when the diff is too large or the culprit is not obvious.
• Bisect only with a non-interactive pass/fail command defined up front, and keep the bookkeeping in git (git bisect good/bad), including when you test a suspect commit directly. When it names the culprit, read only that diff down to the specific line, then run git bisect reset before removing the temporary worktree.

Repeated Regression / Screenshot Reference Mode

Activate when the user says the same issue is still wrong after a fix, provides a "good" screenshot/version/file, or describes a visual result as previously correct.

Treat the reference as evidence, not decoration: list every reported and visible symptom in the user's concrete words; identify the reference oracle (last-good commit, old build, fixture, screenshot, described expected state); define the pass/fail check before editing; then name the exact current-vs-reference delta. Do not generalize a visual defect into "style polish" when the evidence points to a broken render, race, font pipeline, or state path.

If the issue is purely subjective UI taste, route to /ui. If it is rendering, state, timing, build output, font generation, or a regression from a known-good version, stay in /hunt.

Scope Blast Mode

Activate after fixing a root-cause pattern, before declaring the bug done; also when the user says "举一反三", "举一反三深入看看", or "其他地方有没有同样问题". The same shape often hides in N other places; one local fix that ignores the blast leaves N - 1 bugs in the tree.

Extract the pattern signature (the specific function, regex, API call, CSS selector, lock acquisition, validation skip, or input boundary that produced the bug) and grep -rn it across the repo, excluding generated dirs, build output, and vendored deps; for class-of-bug patterns ("any handler missing the lock"), grep the surrounding shape, not just the literal text. For every match, answer in writing: same bug / safe to leave (why) / unsure (ask the user). Do not silently skip a match, and do not claim "fixed" until the blast report is in the Output block. Unrelated bugs the sweep surfaces get listed, not fixed in this PR, unless the user agrees.

Confirm or Discard

Run the one probe that would fail if the hypothesis were wrong, then read it. If the evidence contradicts the hypothesis, discard it completely and re-orient on what the probe just showed. Do not stack a fix onto a disproven hypothesis, and do not keep one just because the code "looks like" the cause.

Runtime Evidence Ladder

Use this ladder before claiming a bug is fixed:

1. Source trace: name the exact function, state transition, file, line, or condition that can produce the symptom.
2. Deterministic repro: run or write the smallest command, fixture, UI path, or scenario that produces it.
3. Logs/state/cache: inspect the runtime state that proves the path was reached, including queues, DB rows, caches, temp files, generated outputs, or external tool logs.
4. Build/test: run the narrow test or build that exercises the fix.
5. Real runtime check: for UI, native app, browser, rendering, or visual bugs, open the app/page/artifact and verify the visible result with a screenshot or concrete checklist.

Compile-only is not enough for UI, native-app, visual, rendering, or generated-artifact bugs. If the runtime check is impossible in the environment, say why and hand off the exact screen, command, or artifact to verify.

When the reporter's environment is the missing rung and it cannot be reproduced locally, the next artifact is a read-only probe they can paste and run, not another hypothesis. Have it print the environment, the disputed measurement, and the state of whatever the hypothesis turns on, and nothing that could carry a secret or a private path. Assume none of your own layout: their install method, directory conventions, locale, shell, and version all differ, so discover rather than hardcode. Ship it as plain copyable text with one command to run and one block to paste back.

For recurring classes of failures, load references/failure-patterns.md before adding a second fix.

Native App Freeze Mode

For beachballs, not responding, tab-switch freezes, first-open lag, idle wake stalls, overlay lockups, or frozen-app screenshots, load references/logging-techniques.md (Native App Freeze Mode) before changing code.

Targeted Logging

Every log is a yes/no question: "if this prints X before Y, hypothesis A survives; otherwise A is dead." A log that cannot rule a hypothesis in or out is noise. Remove temporary logs before finishing; gate persistent diagnostics behind the project's debug flag. If adding a log changes the behavior, that is itself evidence of a timing, lifecycle, or concurrency problem. Full playbook: references/logging-techniques.md.

Rendering Bug Mode

For PDF output, page breaks, font rendering, or print layout defects, load references/rendering-debug.md; it carries the activation triggers and the diagnosis checklist (WeasyPrint quirks, font loading, page overflow, browser print CSS).

IME / Unicode Issues

For input method, character rendering, or text encoding bugs (IME state, cursor drift, emoji splitting, composition events), check references/ime-unicode.md first before forming a hypothesis.