Cross Review

Cross-Review — Opposite-Provider Gate

Same-model review is an echo chamber. This skill asks the other provider to try to break an artifact, with identical severity rules and normalized JSON Lines output for every mode. It never starts by itself: the producing skill invokes it automatically when its outputs are saved, before user approval or handoff. Concept, architecture, plan, requirements, QA, and P7 documentation reviews are mandatory gates; do not ask the user whether to start them.

Modes

Supply source artifacts that establish truth through --ground-truth; the script embeds both artifacts and ground truth with cat -n line numbers. A --diff-base embeds that git diff. Add --diff-paths with normal Git pathspecs for large PROJs; the prompt names every changed path omitted by that scope. Embedded material defaults to a 900,000-byte ceiling and fails before the provider call rather than truncating. The reviewer has no need or permission to run commands, making read-only behaviour independent of sandbox support.

Run it

If scripts/cross-review.sh has not been installed in the project yet, use ~/.claude/skills/cross-review/scripts/cross-review.sh in the commands below. Run from the project root so artifact paths resolve correctly.

Before P0, state.json does not exist. Pass the author explicitly; findings are written to stdout for the human, never to a ledger:

bash scripts/cross-review.sh concept <X> <theme> \
  --artifacts specs/PROJ-<X>-<theme>/1_brainstorm/PROJ-<X>-concept.md \
  --ground-truth specs/PROJ-<X>-<theme>/0_context/existing-state.md \
  --author-provider claude --author-model <writer-model> --round 1

For requirements, review the complete PRD set against the concept and the compact UI contracts that exist. Prefer implementation-handoff.md, sitemap, layout decision, and design language over embedding every mockup HTML file:

bash scripts/cross-review.sh requirements <X> <theme> \
  --artifacts specs/PROJ-<X>-<theme>/2_PRDs/*.md \
  --ground-truth specs/PROJ-<X>-<theme>/1_brainstorm/PROJ-<X>-concept.md \
    specs/PROJ-<X>-<theme>/1d_mockups/implementation-handoff.md \
  --author-provider <current-writer> --round 1

Use architecture with the concept, every PRD in 2_PRDs/, and the curated docs/ARCHITECTURE.md and docs/GUIDELINES.md as ground truth; plan takes the architecture and the same PRDs. Feasibility and traceability are only checked against what is supplied, so a PRD left out is a requirement nobody reviews. If a referenced input does not exist, omit it; do not invent a replacement.

After P0, omit --author-provider and use --author-key to resolve authorship from state.json. That is the persistent gate path: findings are added only via ledger.mjs, and the round is appended only via state.sh.

When the caller knows the author but must persist the review, pass both --author-provider <claude|codex> and --persist. --require-provider codex or claude makes an unavailable/opposite fallback fail rather than silently replacing the required reviewer. For Claude-authored QA, use qa --personas: it launches six separate Codex reviews in parallel. If Codex is unavailable, the script prints a degraded-mode warning, records degraded_fallback: true, and runs the same six personas on the strongest Claude model that is not the author model (CLAUDE_MODEL_RANK, default fable opus sonnet; override with CLAUDE_REVIEW_MODEL); the QA caller must tell the user that independent-provider review was unavailable. Codex-authored QA launches six separate Claude reviews and fails closed when claude auth status is not green; it never substitutes Codex for its own work. Keep --require-provider for handoffs where a fallback must instead stop the gate.

bash scripts/cross-review.sh docs <X> <theme> \
  --artifacts docs/ARCHITECTURE.md docs/PRODUCT.md docs/GUIDELINES.md \
  --author-key docs-delta \
  --diff-base "$(bash scripts/state.sh get <X> <theme> .base_sha)" \
  --diff-paths . ':(exclude)specs/**' ':(exclude)**/*.test.*' \
    ':(exclude)**/*.spec.*' ':(exclude)tests/**' ':(exclude)e2e/**' \
  --round 1

Exit codes: 0 clean or non-blocking only; 3 Critical/High findings; 1 infrastructure failure; 64 invalid use. Critical/High findings block the current handoff.

The producing skill automatically reconciles findings and re-reviews with --round 2, then --round 3 while findings remain, including Medium/Low. No confirmation is needed for another round or fixes within approved scope; ask only when resolving a finding requires a product decision. Stop early when there are no findings. Exit 0 alone does not mean zero findings: inspect the emitted findings or the persisted round's findings_added count. Each script invocation runs one read-only review; the producing skill applies fixes between calls (QA delegates fixes to its P6 controller). On persistent runs, update finding status through ledger.mjs before re-review. Three rounds is the automatic maximum: remaining Critical/High findings block handoff and go to the human; remaining Medium/Low findings are reported or deferred as debt. Additional manually requested rounds have no limit: continue with --round 4, --round 5, and so on, preserving the same finding and handoff gates. A manual request authorizes the requested rounds, not an unbounded automatic loop. Infrastructure failures are not completed review rounds.

Applying a finding: reconcile, don't narrate. Rewrite the affected section of the artifact as if it were correct the first time. Never leave "Correction (post-review)," "Post-cross-review addition," "an earlier draft said X," or similar narrated-diff scaffolding in the artifact itself — that turns every future reader into an archaeologist who has to reconstruct current truth from a change log. The round's findings and the fix are already recorded in the cross-review output consumed at handoff time; the artifact only needs to be correct, not annotated with its own history.

Routing and output integrity

• Claude-authored artifacts go to Codex; Codex-authored artifacts go to Claude. --joint runs both independently. If Codex is unavailable, the strongest Claude model that is not the author model is chosen automatically (rank fable opus sonnet, alias or full id compared by substring); that is marked as a degraded persistent review. Any route that selects Claude verifies CLI availability and authentication before launching the review.
• qa --personas starts six independent workers (security, principal engineering, performance, reliability, architecture, and minimalism), rather than asking one reviewer to impersonate a panel. The Claude-authored route prefers Codex and falls back loudly to six Claude workers only when Codex is unavailable.
• The Claude adapter requests validated --output-format json plus a JSON Schema, then normalizes structured_output.findings to the shared JSON Lines contract. Both adapters reject zero findings, review-blocked, recognizable Bubblewrap or user-namespace failures, and any output that mixes review-clean with a finding.
• Findings are deduplicated by category + file + line + summary before they reach stdout or the ledger. review-clean is a liveness marker, never a finding.
• Review prompts stream to both provider CLIs with a default 900,000-byte embedded-material ceiling. Set CROSS_REVIEW_MAX_CONTEXT_BYTES when the selected provider has a different verified limit (0 means consciously unlimited). --diff-paths scopes large diffs and always tells both operator and reviewer which changed paths were omitted. Claude Code itself imposes a 10 MB stdin transport ceiling; the Claude adapter detects it before launch and fails with the exact cause rather than truncating or silently narrowing review scope.