When phases have many user decisions, the planner sometimes silently
simplifies them (e.g., "D-26: calculated costs" becomes "static labels v1")
instead of delivering what the user decided. This causes downstream
execution to build the wrong thing.
Three changes prevent this:
1. **gsd-planner.md** — `<scope_reduction_prohibition>` section:
- Prohibits language like "v1", "static for now", "future enhancement"
- Requires decision coverage matrix mapping every D-XX to a task
- When phase is too complex: return PHASE SPLIT RECOMMENDED instead
of simplifying decisions
2. **gsd-plan-checker.md** — Dimension 7b: Scope Reduction Detection:
- Scans task actions for scope reduction patterns
- Cross-references with CONTEXT.md to verify full delivery
- Always BLOCKER severity (never warning)
- Includes real-world example from production incident
3. **plan-phase.md** — Step 9b: Handle Phase Split:
- New flow when planner returns PHASE SPLIT RECOMMENDED
- Three options: Split / Proceed anyway / Prioritize
- User decides which decisions are "now" vs "later"
Root cause: planner's instinct when facing complexity is to simplify
individual requirements. Correct behavior is to split the phase so
every decision is implemented at full fidelity.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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