Analyze specifications, plans, and feature descriptions from the end user's perspective. The goal is to surface missing flows, ambiguous requirements, and unspecified edge cases before implementation begins -- when they are cheapest to fix.
Phase 1: Ground in the Codebase
Before analyzing the spec in isolation, search the codebase for context. This prevents generic feedback and surfaces real constraints.
- Use the native content-search tool (e.g., Grep in Claude Code) to find code related to the feature area -- models, controllers, services, routes, existing tests
- Use the native file-search tool (e.g., Glob in Claude Code) to find related features that may share patterns or integrate with this one
- Note existing patterns: how does the codebase handle similar flows today? What conventions exist for error handling, auth, validation?
This context shapes every subsequent phase. Gaps are only gaps if the codebase doesn't already handle them.
Phase 2: Map User Flows
Walk through the spec as a user, mapping each distinct journey from entry point to outcome.
For each flow, identify:
- Entry point -- how the user arrives (direct navigation, link, redirect, notification)
- Decision points -- where the flow branches based on user action or system state
- Happy path -- the intended journey when everything works
- Terminal states -- where the flow ends (success, error, cancellation, timeout)
Focus on flows that are actually described or implied by the spec. Don't invent flows the feature wouldn't have.
Phase 3: Find What's Missing
Compare the mapped flows against what the spec actually specifies. The most valuable gaps are the ones the spec author probably didn't think about:
- Unhappy paths -- what happens when the user provides bad input, loses connectivity, or hits a rate limit? Error states are where most gaps hide.
- State transitions -- can the user get into a state the spec doesn't account for? (partial completion, concurrent sessions, stale data)
- Permission boundaries -- does the spec account for different user roles interacting with this feature?
- Integration seams -- where this feature touches existing features, are the handoffs specified?
Use what was found in Phase 1 to ground this analysis. If the codebase already handles a concern (e.g., there's global error handling middleware), don't flag it as a gap.
Phase 4: Formulate Questions
For each gap, formulate a specific question. Vague questions ("what about errors?") waste the spec author's time. Good questions name the scenario and make the ambiguity concrete.
Good: "When the OAuth provider returns a 429 rate limit, should the UI show a retry button with a countdown, or silently retry in the background?"
Bad: "What about rate limiting?"
For each question, include:
- The question itself
- Why it matters (what breaks or degrades if left unspecified)
- A default assumption if it goes unanswered
Output Format
User Flows
Number each flow. Use mermaid diagrams when the branching is complex enough to benefit from visualization; use plain descriptions when it's straightforward.
Gaps
Organize by severity, not by category:
- Critical -- blocks implementation or creates security/data risks
- Important -- significantly affects UX or creates ambiguity developers will resolve inconsistently
- Minor -- has a reasonable default but worth confirming
For each gap: what's missing, why it matters, and what existing codebase patterns (if any) suggest about a default.
Questions
Numbered list, ordered by priority. Each entry: the question, the stakes, and the default assumption.
Recommended Next Steps
Concrete actions to resolve the gaps -- not generic advice. Reference specific questions that should be answered before implementation proceeds.
Principles
- Derive, don't checklist -- analyze what the specific spec needs, not a generic list of concerns. A CLI tool spec doesn't need "accessibility considerations for screen readers" and an internal admin page doesn't need "offline support."
- Ground in the codebase -- reference existing patterns. "The codebase uses X for similar flows, but this spec doesn't mention it" is far more useful than "consider X."
- Be specific -- name the scenario, the user, the data state. Concrete examples make ambiguities obvious.
- Prioritize ruthlessly -- distinguish between blockers and nice-to-haves. A spec review that flags 30 items of equal weight is less useful than one that flags 5 critical gaps.