Dev Bug Review

Bug Review

A disciplined workflow for working a queue of bug reports. One bug at a time. No skipping steps. No batching.

The contract

For every incoming bug report, execute these five phases in order. Do not proceed to the next phase without the previous one's output.

1. Confirm the finding -- reproduce or evidence the bug before believing it
2. Validate the solution or push back -- evaluate the proposed fix; disagree with reasoning if warranted
3. Get agreement -- wait for the user to agree before touching code
4. Implement -- apply the fix, add tests, verify
5. Summarize, commit, changelog -- one commit per bug, changelog entry included

If there are N bugs, you run this loop N times. Do not try to land all bugs in one commit unless the user explicitly says so.

Phase 1: Confirm the finding

Before writing any code, prove the bug is real and that you understand it.

• Read the code path the report implicates. Cite file paths and line numbers.
• Reproduce it where feasible: a failing test, a just exec "<cmd>" that demonstrates the issue, a session DB inspection, a screenshot, a log snippet.
• For integration-test failures, check for a preserved service log first. The test fixtures (ServiceInstance, e2e RealService, MCP conftest helper) archive their tmp_dir to cache/target/tests/evidence/<timestamp>-<worker>-<nodeid>/<tmp-basename>/ on failure. The stderr of the failing test has an ARTIFACT: preserved ... -> cache/target/tests/evidence/... line with the exact path. Inside: service.log, sessions/<vm-id>/process.log, sessions/<vm-id>/serial.log, sessions/<vm-id>/session.db, logs/gateway.log. These are the authoritative evidence for "VM didn't boot", "provision hung", or "exec timed out" style reports -- read them before accepting any root-cause theory. See /dev-debugging Step 2 for the layout. If the artifact doesn't exist, ask the user to rerun (or run it yourself) so one gets captured.
• If the report is vague ("it's slow", "it crashes sometimes"), nail it down before moving on. Ask a targeted question rather than guess.
• If the bug is not reproducible or not present in the code, say so clearly and stop. Do not manufacture a fix for a bug that doesn't exist.

Output for this phase is a short statement: what the bug is, where it lives, and the evidence. Do not proceed silently.

Phase 2: Validate the solution or push back

The report usually arrives with a proposed fix. Treat it as a hypothesis, not an order (see memory: "Push back on proposed fixes").

Evaluate the proposed fix against:

• Does it address the root cause, or just the symptom? Symptom patches leave the bug to resurface elsewhere.
• Is the pattern systemic? If the same mistake exists in 7 other places, fixing only the reported site is deferred breakage. See /dev-debugging "Fix the pattern, not the instance".
• Does it break invariants? Ephemeral VM model, guest binary read-only, codesigning entitlement, gateway auth (never weaken), Tauri embed-at-build -- all listed in CLAUDE.md.
• Does it contradict a memory or skill? Check relevant skills before accepting a fix that seems to fight them.
• Is there a simpler or safer alternative? Sometimes the right fix is deleting the feature, not patching it.

If the proposed fix is wrong or incomplete, push back with reasoning. State what you'd do instead and why. Do not silently "improve" the fix -- name the disagreement so the user can weigh in.

If the proposed fix is correct, say so plainly. Do not pad with fake alternatives.

Phase 3: Get agreement

Stop and wait. Do not start editing code until the user confirms the plan for this specific bug. A single "sounds good" covers this one bug, not the whole queue.

Auto mode does not override this. Agreement gates on the fix plan are a feature, not an interruption -- the user explicitly asked for a review workflow.

Phase 4: Implement (TDD)

Fixes land test-first. No exceptions.

1. Write the test first, watch it fail. Before editing implementation code, write a test that captures the bug and fails for the right reason. "Fails for the right reason" matters -- a test that fails because of a missing import tells you nothing. Run the test and see the red.
   • If the bug lives in a pure function, unit-test that function directly.
   • If the bug is only visible through I/O or timing, extract a pure helper (e.g. argument construction, state transition, decision logic) out of the buggy site and test the helper. Extraction is part of the fix, not scope creep.
   • If you literally cannot write a failing test (e.g. the bug is in a system call behavior you can't mock), state that out loud and describe the manual reproduction you ran instead. Do not skip this silently.
2. Apply the fix. Watch the test go green. Minimum code needed -- no opportunistic refactors beyond what the test extraction required (see CLAUDE.md "Minimize code").
3. If the pattern is systemic, fix all instances in this pass. Do not defer siblings to "a future cleanup". The audit from Phase 2 defines the scope.
4. While fixing, surface any additional issues you uncover. If the code you're touching has an adjacent bug (zombie children, duplicated branches, wrong error handling), flag it in your summary. Fold small ones into the same fix; call out larger ones for a separate bug review pass.
5. Opportunistic cleanup -- do it, but name it. When your diagnosis reveals that the buggy code reinvents a wheel the project already has (hand-rolled retry when capsem_core::poll::poll_until exists, hand-rolled 0o600 when pty_log::open_append exists, a vec![...] a clippy-lint away, a patient: bool where an enum self-documents), fix it in the same commit. Do NOT ship a minimal diff on top of a bug that was caused by the duplication -- that's how the same bug class reappears in a new location. Rules: (a) touch only code the fix itself motivates, (b) check existing primitives first (grep for poll_until, capsem_core::, shared helpers) before hand-rolling anything, (c) call out each cleanup in the summary so it's explicit, not silent. "Also fixed while I was here: X, Y, Z." If the cleanup is large enough that it'd dominate the diff or obscure the bug fix, split it into a sibling commit in the same review.
6. Run the relevant gates:

• Rust change: cargo check -p <crate> + targeted cargo test
• Cross-cutting Rust: just test
• Frontend: pnpm run check (fail-on-warnings) + pnpm test where relevant
• VM behavior: just exec "capsem-doctor -k <category>" or the targeted diagnostic
• Telemetry: python3 build_system/scripts/doctor/check_session.py
• Fix every warning surfaced. Warnings are errors (CLAUDE.md).

Phase 5: Summarize, commit, changelog

Write a summary back to the user before committing:

• What the bug was (one line)
• Root cause (one or two lines)
• What you changed (files + intent, not line-by-line diff)
• How you verified (tests/commands run)

Then commit per project rules (CLAUDE.md "Commits"):

• Update CHANGELOG.md under ## [Unreleased] in the same commit as the fix. Write from the user's perspective under ### Fixed.
• Stage files explicitly. No git add -A.
• Conventional message: fix: <one-line subject>. Body can expand on root cause.
• Author: Elie Bursztein github@elie.net. No Co-Authored-By trailers.
• One bug per commit. If you fixed a systemic pattern across many files, that's still one commit -- but it's still one bug.

Then move to the next bug in the queue and repeat from Phase 1.

Anti-patterns

• Skipping the failing test: going straight to the fix. The test-first gate catches wrong diagnoses and guards against regressions.
• Skipping confirmation: accepting the report at face value and jumping to a fix. You will fix the wrong thing.
• Silent solution swap: user proposed fix A, you silently shipped fix B. Surface the disagreement instead.
• Agreement creep: treating "sounds good" on bug #1 as authorization for bugs #2-#5. Re-agree per bug.
• Batched commits: "I fixed all five, here's the commit." Loses bisectability and blurs the changelog.
• Skipped changelog: "I'll add it at the end." Each commit carries its own entry.
• Pre-existing dismissal: "That failure is unrelated." Investigate every failure surfaced during the fix. Never deflect.
• Symptom patching: stripping a header to avoid a decoder bug instead of fixing the decoder. Address the system, not the surface.
• Narrow fix for systemic bug: fixing 1 of 8 identical sites. Audit first, then fix all in one pass.

Relationship to other skills

• /dev-debugging -- the methodology for a single bug investigation (reproduce, diagnose, fix). Bug review composes debugging across a queue with extra gates (confirm, push back, per-bug commit).
• /dev-sprint -- for multi-change features. Bug review is lighter weight: no sprint dir, no tracker.md, one commit per bug.
• /dev-testing -- the testing gates invoked in Phase 4.