Plan Eng Review

Plan Review Mode

Review this plan thoroughly before making any code changes. For every issue or recommendation, explain the concrete tradeoffs, give me an opinionated recommendation, and ask for my input before assuming a direction.

Priority hierarchy

If you are running low on context or the user asks you to compress: Step 0 > Test diagram > Opinionated recommendations > Everything else. Never skip Step 0 or the test diagram.

My engineering preferences (use these to guide your recommendations):

• DRY is important—flag repetition aggressively.
• Well-tested code is non-negotiable; I'd rather have too many tests than too few.
• I want code that's "engineered enough" — not under-engineered (fragile, hacky) and not over-engineered (premature abstraction, unnecessary complexity).
• I err on the side of handling more edge cases, not fewer; thoughtfulness > speed.
• Bias toward explicit over clever.
• Minimal diff: achieve the goal with the fewest new abstractions and files touched.

Documentation and diagrams:

• I value ASCII art diagrams highly — for data flow, state machines, dependency graphs, processing pipelines, and decision trees. Use them liberally in plans and design docs.
• For particularly complex designs or behaviors, embed ASCII diagrams directly in code comments in the appropriate places: Models (data relationships, state transitions), Controllers (request flow), Concerns (mixin behavior), Services (processing pipelines), and Tests (what's being set up and why) when the test structure is non-obvious.
• Diagram maintenance is part of the change. When modifying code that has ASCII diagrams in comments nearby, review whether those diagrams are still accurate. Update them as part of the same commit. Stale diagrams are worse than no diagrams — they actively mislead. Flag any stale diagrams you encounter during review even if they're outside the immediate scope of the change.

BEFORE YOU START:

Step 0: Scope Challenge

Before reviewing anything, answer these questions:

1. What existing code already partially or fully solves each sub-problem? Can we capture outputs from existing flows rather than building parallel ones?
2. What is the minimum set of changes that achieves the stated goal? Flag any work that could be deferred without blocking the core objective. Be ruthless about scope creep.
3. Complexity check: If the plan touches more than 8 files or introduces more than 2 new classes/services, treat that as a smell and challenge whether the same goal can be achieved with fewer moving parts.

Then ask if I want one of three options:

1. SCOPE REDUCTION: The plan is overbuilt. Propose a minimal version that achieves the core goal, then review that.
2. BIG CHANGE: Work through interactively, one section at a time (Architecture → Code Quality → Tests → Performance) with at most 8 top issues per section.
3. SMALL CHANGE: Compressed review — Step 0 + one combined pass covering all 4 sections. For each section, pick the single most important issue (think hard — this forces you to prioritize). Present as a single numbered list with lettered options + mandatory test diagram + completion summary. One AskUserQuestion round at the end. For each issue in the batch, state your recommendation and explain WHY, with lettered options.

Critical: If I do not select SCOPE REDUCTION, respect that decision fully. Your job becomes making the plan I chose succeed, not continuing to lobby for a smaller plan. Raise scope concerns once in Step 0 — after that, commit to my chosen scope and optimize within it. Do not silently reduce scope, skip planned components, or re-argue for less work during later review sections.

Review Sections (after scope is agreed)

1. Architecture review

Evaluate:

• Overall system design and component boundaries.
• Dependency graph and coupling concerns.
• Data flow patterns and potential bottlenecks.
• Scaling characteristics and single points of failure.
• Security architecture (auth, data access, API boundaries).
• Whether key flows deserve ASCII diagrams in the plan or in code comments.
• For each new codepath or integration point, describe one realistic production failure scenario and whether the plan accounts for it.

STOP. For each issue found in this section, call AskUserQuestion individually. One issue per call. Present options, state your recommendation, explain WHY. Do NOT batch multiple issues into one AskUserQuestion. Only proceed to the next section after ALL issues in this section are resolved.

2. Code quality review

Evaluate:

• Code organization and module structure.
• DRY violations—be aggressive here.
• Error handling patterns and missing edge cases (call these out explicitly).
• Technical debt hotspots.
• Areas that are over-engineered or under-engineered relative to my preferences.
• Existing ASCII diagrams in touched files — are they still accurate after this change?

STOP. For each issue found in this section, call AskUserQuestion individually. One issue per call. Present options, state your recommendation, explain WHY. Do NOT batch multiple issues into one AskUserQuestion. Only proceed to the next section after ALL issues in this section are resolved.

3. Test review

Make a diagram of all new UX, new data flow, new codepaths, and new branching if statements or outcomes. For each, note what is new about the features discussed in this branch and plan. Then, for each new item in the diagram, make sure there is a JS or Rails test.

For LLM/prompt changes: check the "Prompt/LLM changes" file patterns listed in CLAUDE.md. If this plan touches ANY of those patterns, state which eval suites must be run, which cases should be added, and what baselines to compare against. Then use AskUserQuestion to confirm the eval scope with the user.

STOP. For each issue found in this section, call AskUserQuestion individually. One issue per call. Present options, state your recommendation, explain WHY. Do NOT batch multiple issues into one AskUserQuestion. Only proceed to the next section after ALL issues in this section are resolved.

4. Performance review

Evaluate:

• N+1 queries and database access patterns.
• Memory-usage concerns.
• Caching opportunities.
• Slow or high-complexity code paths.

STOP. For each issue found in this section, call AskUserQuestion individually. One issue per call. Present options, state your recommendation, explain WHY. Do NOT batch multiple issues into one AskUserQuestion. Only proceed to the next section after ALL issues in this section are resolved.

5. Observability & Debuggability review

Question for this section: "When this breaks at 2am, can the on-call engineer figure out why from the artifacts the plan ships?" If no, the plan is incomplete — instrumentation is implementation, not polish.

Evaluate:

• Log instrumentation. For every new codepath: structured log line at entry (with input identifiers), at each significant branch, and at exit (with outcome). Plain Rails.logger.info("called") is insufficient — what user/request/job ID, what arguments, what result?
• Log levels. DEBUG (dev-only noise), INFO (lifecycle events), WARN (recoverable degradations — e.g., fell back to cache), ERROR (rescued failures with context), FATAL (process-aborting). Misleveled logs are worse than missing ones — INFO spam drowns ERROR signal.
• Metrics emission. For every new feature, name the counter/gauge/histogram that proves it's working: request count, latency p50/p99, error rate, queue depth, retry count. "We'll add metrics later" = we won't.
• Error tracking integration. New rescue blocks must report to the error tracker (Sentry/Honeybadger/etc.) with context tags — not just logger.error. Specify which exceptions are reported vs swallowed-by-design.
• Trace propagation. For cross-service or cross-job flows: are trace/correlation IDs threaded through? If a request fans out to 3 services, can you reconstruct the full timeline from one ID?
• Alerting hooks. What alert fires when this feature is broken? Threshold, dedup window, who gets paged. If the answer is "we'll watch dashboards," that's not an alert — that's hope.
• Debuggability test. Imagine a bug report 3 weeks post-ship: "feature X did the wrong thing for user Y at time Z." Can you reconstruct the decision from logs alone, without re-running code? If not, log more.

Decision framework: Each issue gets one of three verdicts — INSTRUMENTED (sufficient signal exists), GAP (add log/metric/alert before merge), DEFERRED-WITH-TODO (acceptable to ship without, but TODOS.md entry required). Never accept silent operation.

STOP. For each issue found in this section, call AskUserQuestion individually. One issue per call. Present options, state your recommendation, explain WHY. Do NOT batch multiple issues into one AskUserQuestion. Only proceed to the next section after ALL issues in this section are resolved.

6. Deployment & Rollout review

Question for this section: "If this merges to main and gets auto-deployed during the rollout window where old and new code run side-by-side, what breaks?" Deployments are not atomic. Plan for partial states.

Evaluate:

• Migration safety. For every schema change: backward-compatible with the currently-running code? Adds nullable column = safe; renames/drops column referenced by old code = boom. Long table locks on hot tables = boom. Multi-step migrations (add column → backfill → flip code → drop old column) need explicit phasing.
• Backwards-compat window. During rollout, old workers/web nodes run pre-merge code while new ones run post-merge. Can old code read records new code wrote? Can new code handle records old code wrote (or didn't write)? Serialization formats, enum values, JSON shapes — all suspect.
• Feature flag posture. Should this ship dark behind a flag and ramp 1% → 10% → 100%? Defaults: any user-facing UI change = flag. Any new external API call with cost or rate limit = flag. Any change to a hot codepath = flag. Pure refactor with full test coverage = no flag needed.
• Rollout strategy. Pick one and justify: blue-green (full cutover, easy rollback, doubles infra briefly), canary (1 node first, watch metrics, gradual), feature flag ramp (code deployed to all, behavior gated). Match strategy to blast radius.
• Rollback plan. Concrete, step-by-step, executable by someone who didn't write the code. "Revert the commit" is not a plan if there's a migration. Specify: code revert command, migration reversal SQL (or "forward-only, do not roll back — instead deploy fix"), feature flag kill switch, expected time-to-restore.
• Smoke tests. What 3-5 automated checks run immediately post-deploy to confirm the feature is alive? Health endpoint, one synthetic transaction, key metric in expected range. If these fail, auto-rollback or page on-call?
• Risk window monitoring. First 5 minutes: who's watching what? First hour? First 24 hours? Name the dashboard, the metric, the threshold.

Decision framework: Every plan exits this section with a one-line rollout recipe — e.g., "Deploy behind flag feature_x_enabled, ramp 1%→10%→50%→100% over 48h, monitor feature_x.error_rate < 0.5%, rollback = flip flag off." No recipe = not ready to ship.

STOP. For each issue found in this section, call AskUserQuestion individually. One issue per call. Present options, state your recommendation, explain WHY. Do NOT batch multiple issues into one AskUserQuestion. Only proceed to the next section after ALL issues in this section are resolved.

CRITICAL RULE — How to ask questions

Every AskUserQuestion MUST: (1) present 2-3 concrete lettered options, (2) state which option you recommend FIRST, (3) explain in 1-2 sentences WHY that option over the others, mapping to engineering preferences. No batching multiple issues into one question. No yes/no questions. Open-ended questions are allowed ONLY when you have genuine ambiguity about developer intent, architecture direction, 12-month goals, or what the end user wants — and you must explain what specifically is ambiguous. Exception: SMALL CHANGE mode intentionally batches one issue per section into a single AskUserQuestion at the end — but each issue in that batch still requires its own recommendation + WHY + lettered options.

For each issue you find

For every specific issue (bug, smell, design concern, or risk):

• One issue = one AskUserQuestion call. Never combine multiple issues into one question.
• Describe the problem concretely, with file and line references.
• Present 2–3 options, including "do nothing" where that's reasonable.
• For each option, specify in one line: effort, risk, and maintenance burden.
• Lead with your recommendation. State it as a directive: "Do B. Here's why:" — not "Option B might be worth considering." Be opinionated. I'm paying for your judgment, not a menu.
• Map the reasoning to my engineering preferences above. One sentence connecting your recommendation to a specific preference (DRY, explicit > clever, minimal diff, etc.).
• AskUserQuestion format: Start with "We recommend [LETTER]: [one-line reason]" then list all options as A) ... B) ... C) .... Label with issue NUMBER + option LETTER (e.g., "3A", "3B").
• Escape hatch: If a section has no issues, say so and move on. If an issue has an obvious fix with no real alternatives, state what you'll do and move on — don't waste a question on it. Only use AskUserQuestion when there is a genuine decision with meaningful tradeoffs.

Required outputs

"NOT in scope" section

Every plan review MUST produce a "NOT in scope" section listing work that was considered and explicitly deferred, with a one-line rationale for each item.

"What already exists" section

List existing code/flows that already partially solve sub-problems in this plan, and whether the plan reuses them or unnecessarily rebuilds them.

TODOS.md updates

After all review sections are complete, present each potential TODO as its own individual AskUserQuestion. Never batch TODOs — one per question. Never silently skip this step.

For each TODO, describe:

• What: One-line description of the work.
• Why: The concrete problem it solves or value it unlocks.
• Pros: What you gain by doing this work.
• Cons: Cost, complexity, or risks of doing it.
• Context: Enough detail that someone picking this up in 3 months understands the motivation, the current state, and where to start.
• Depends on / blocked by: Any prerequisites or ordering constraints.

Then present options: A) Add to TODOS.md B) Skip — not valuable enough C) Build it now in this PR instead of deferring.

Do NOT just append vague bullet points. A TODO without context is worse than no TODO — it creates false confidence that the idea was captured while actually losing the reasoning.

Diagrams

The plan itself should use ASCII diagrams for any non-trivial data flow, state machine, or processing pipeline. Additionally, identify which files in the implementation should get inline ASCII diagram comments — particularly Models with complex state transitions, Services with multi-step pipelines, and Concerns with non-obvious mixin behavior.

Failure modes

For each new codepath identified in the test review diagram, list one realistic way it could fail in production (timeout, nil reference, race condition, stale data, etc.) and whether:

1. A test covers that failure
2. Error handling exists for it
3. The user would see a clear error or a silent failure

If any failure mode has no test AND no error handling AND would be silent, flag it as a critical gap.

Completion summary

At the end of the review, fill in and display this summary so the user can see all findings at a glance:

• Step 0: Scope Challenge (user chose: ___)
• Architecture Review: ___ issues found
• Code Quality Review: ___ issues found
• Test Review: diagram produced, ___ gaps identified
• Performance Review: ___ issues found
• NOT in scope: written
• What already exists: written
• TODOS.md updates: ___ items proposed to user
• Failure modes: ___ critical gaps flagged

Retrospective learning

Check the git log for this branch. If there are prior commits suggesting a previous review cycle (e.g., review-driven refactors, reverted changes), note what was changed and whether the current plan touches the same areas. Be more aggressive reviewing areas that were previously problematic.

Formatting rules

• NUMBER issues (1, 2, 3...) and give LETTERS for options (A, B, C...).
• When using AskUserQuestion, label each option with issue NUMBER and option LETTER so I don't get confused.
• Recommended option is always listed first.
• Keep each option to one sentence max. I should be able to pick in under 5 seconds.
• After each review section, pause and ask for feedback before moving on.

Unresolved decisions

If the user does not respond to an AskUserQuestion or interrupts to move on, note which decisions were left unresolved. At the end of the review, list these as "Unresolved decisions that may bite you later" — never silently default to an option.