planmode-engineer

name	planmode-engineer
description	Use when reviewing an execution plan and you need engineering scrutiny across architecture, data flow, diagrams, edge cases, test coverage, and performance.

planmode-engineer

Cogine internal skill for engineering-manager plan review.

Cross-Platform Notes

• When this skill says AskUserQuestion, use the platform's question or confirmation tool if available; otherwise ask the user directly and wait.
• Ignore toolchain-specific self-management integrations unless your environment explicitly provides them.
• Do not start implementation or edit project code while running this skill.

Preamble (run first)

_BRANCH=$(git branch --show-current 2>/dev/null || echo "unknown")
_BASE_BRANCH=$(gh pr view --json baseRefName -q .baseRefName 2>/dev/null || gh repo view --json defaultBranchRef -q .defaultBranchRef.name 2>/dev/null || echo "main")
echo "BRANCH: $_BRANCH"
echo "BASE_BRANCH: $_BASE_BRANCH"

AskUserQuestion Format

ALWAYS follow this structure for every AskUserQuestion call:

1. Re-ground: State the project, the current branch (use the _BRANCH value printed by the preamble — NOT any branch from conversation history or gitStatus), the base branch when relevant, and the current plan/task. (1-2 sentences)
2. Simplify: Explain the problem in plain English a smart 16-year-old could follow. No raw function names, no internal jargon, no implementation details. Use concrete examples and analogies. Say what it DOES, not what it's called.
3. Recommend: RECOMMENDATION: Choose [X] because [one-line reason]
4. Options: Lettered options: A) ... B) ... C) ...

Assume the user hasn't looked at this window in 20 minutes and doesn't have the code open. If you'd need to read the source to understand your own explanation, it's too complex.

Per-skill instructions may add additional formatting rules on top of this baseline.

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:

Target Gate

Before reviewing architecture or tests, identify the exact artifact being reviewed:

• Current branch diff against the detected base branch.
• Pasted implementation plan.
• Backlog-ready spec or GitHub issue.
• Product/founder handoff that still needs engineering translation.
• Specific files or modules named by the user.

If more than one target is plausible, ask the user to choose. Do not silently combine targets.

For issue/spec inputs, first state whether the input is implementation-ready:

• READY: enough scope, target files/modules, acceptance criteria, and validation exist.
• READY WITH RISKS: implementable, but risks or assumptions must be visible.
• NOT READY: missing decisions would materially change implementation.

If the verdict is NOT READY, list the missing information and recommend backlog-ready-spec before continuing.

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.
4. TODOS cross-reference: Read TODOS.md if it exists. Are any deferred items blocking this plan? Can any deferred items be bundled into this PR without expanding scope? Does this plan create new work that should be captured as a TODO?

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.

Test Plan Artifact

After producing the test diagram, write a portable local test plan artifact in the repo so later QA or review workflows can consume it:

BRANCH=$(git rev-parse --abbrev-ref HEAD 2>/dev/null || echo "unknown")
USER=$(whoami)
DATETIME=$(date +%Y%m%d-%H%M%S)
mkdir -p .planmode/test-plans

Write to .planmode/test-plans/{user}-{branch}-test-plan-{datetime}.md:

# Test Plan
Generated by /planmode-engineer on {date}
Branch: {branch}
Repo: {owner/repo}

## Affected Pages/Routes
- {URL path} — {what to test and why}

## Key Interactions to Verify
- {interaction description} on {page}

## Edge Cases
- {edge case} on {page}

## Critical Paths
- {end-to-end flow that must work}

This file is a portable handoff artifact. Include only the information that helps a QA tester know what to test and where — not implementation details.

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.

CRITICAL RULE — How to ask questions

Follow the AskUserQuestion format from the Preamble above. Additional rules for plan reviews:

• 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.
• Map the reasoning to my engineering preferences above. One sentence connecting your recommendation to a specific preference (DRY, explicit > clever, minimal diff, etc.).
• 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.
• 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.

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. Use the TODO schema below.

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:

• Review Target: branch diff / pasted plan / backlog spec / issue / product/founder handoff / files
• Implementation Readiness Verdict: READY / READY WITH RISKS / NOT READY
• 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 LETTERS for options (A, B, C...).
• Label with NUMBER + LETTER (e.g., "3A", "3B").
• One sentence max per option. 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.