Let routed CI cache researched reviews too, from one shared policy

[brentvatne]

Caught by the reviewer on the roadmap PR (#72). It flagged the roadmap for claiming researched reviews are cacheable again — and it was right, because the fix only half-landed.

The miss

#71 removed the offline index and dropped the research gate from cacheAllowed in runLegacyCi. runRoutedCi — the path taken by every repo that has adopted routing.jsonc — still had it:

const cacheAllowed =
  !bypassTriggerGate &&
  !stackWalk &&
  !feedbackNeedsRunSeam(rootConfig.feedback) &&
  !rootConfig.research.enabled &&   // ← still here
  metadata !== undefined;

git log -S confirms both gates were added by the same commit (#61) for the same reason: the offline index was an artifact whose contents the cache key could not represent. With the index gone that reason is gone, so this was a missed half rather than an independent constraint. Effect: routed repos have been running a fresh review for every researched PR unnecessarily.

The fix is the deduplication

Correcting the second copy would leave the actual defect in place — one policy written out twice will drift, and this one already did. reviewCacheAllowed in review-cache.ts is now the single definition, and both paths call it.

A unit test pins each flag and records explicitly that research is not among them, so the next person to wonder doesn't have to re-derive it from two call sites.

Note on the roadmap PR

I fixed the code rather than qualifying the prose, so #72's text ("removing the offline index let ci.ts drop !config.research.enabled from cacheAllowed, so researched reviews are cacheable again") is accurate once this merges. No change needed there.

Verification

tsc clean · oxlint clean · oxfmt clean · ref-check 0 errors · 709 tests pass (+1).

🤖 Generated with Claude Code

[github-actions]

🤖 AI code review

Decision: Approve

Overall PR risk: Medium. This change modifies existing behavior by consolidating the cache-allow policy from two separate implementations into one shared function. Both the legacy and routed CI paths now have identical logic, which is correct: the reason for blocking cache reuse (the offline index artifact) was removed in #71 for the legacy path but missed in the routed path. The behavior is now consistent across both code paths. What might break: routed repositories with research enabled will now reuse cached reviews when the input hash matches; the hash covers scoped files, content, scope config, PR metadata, agents, and route, but does not cover live documentation content, so reused reviews could carry stale citations and skip fresh MCP calls. Blast radius is limited to routed CI runs only, and rollback is straightforward (add the research flag back to reviewCacheAllowed or bump REVIEW_INPUT_HASH_VERSION). No critical or warning-level defects found.

🔗 Review setup:

• This PR changes code the reviewer prompts cite (src, src/tests). Check that the guidance quoting it is still correct.

No findings.

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This review is advisory — it never blocks a merge and never auto-approves.