## 2.5. Validate `--reviews` Prerequisite

**Skip if:** No `--reviews` flag.

**If `--reviews` AND `--gaps`:** Error — cannot combine `--reviews` with `--gaps`. These are conflicting modes.

**If `--reviews` AND `has_reviews` is false (no REVIEWS.md in phase dir):**

Error:
```
No REVIEWS.md found for Phase {N}. Run reviews first:

/gsd:review --phase {N}

Then re-run /gsd:plan-phase {N} --reviews
```
Exit workflow.