Multi-Provider Code Review

Run independent code reviews from Antigravity and Codex in parallel, verify each finding against the source, then present combined consensus / unique / rejected sections so the user sees what really matters and what was a false positive. (Gemini is one command away via the gemini-reviewer agent or /gemini-review if you want it in the mix.)

Why verification matters

Confidence scores are not an oracle. In a real session on 2026-04-17, Gemini returned two findings at 95/100 confidence that were factually wrong (a z.enum([]) claim that ignored an existing fallback, and an "MCP SDK doesn't support outputSchema" claim that was contradicted by the actual .d.ts). Both would have caused a mis-fix if accepted at face value. Always verify before presenting.

Two kinds of verification — pick the right skill

This skill verifies review findings — the bugs each provider claims it found. Phase 3 reads the file at the cited line and checks whether each finding is real before presenting it.

That is different from verifying assistant claims — the statements the assistant made in its prior turn ("I added retry logic," "I bumped the threshold to 16384"). For that, use /codex-verify. It dispatches the codex-verifier agent, decomposes the assistant's last message into atomic claims, and proves or disproves each with deterministic evidence. It returns a CONFIDENCE grade on a five-point ladder (PERFECT | VERIFIED | PARTIAL | FEEDBACK | FAILED) — PARTIAL and FAILED are first-class verdicts, surfacing gaps in your verification harness rather than hiding them under a confident-looking number.

The two skills compose. Run both when you want both questions answered; do not merge their outputs.

Instructions

Phase 1: Gather and prepare the diff

1. Get the working-tree state:

• git status --short to see what's modified/added/deleted
• For untracked files the user wants reviewed, run git add -N <files> so they appear in git diff (intent-to-add)
• Combine git diff (unstaged) and git diff --cached (staged) into a single diff

1. Filter the diff — exclude noise that providers don't need:

• Pathspec exclusions: :!docs/ :!apps/docs/ :!*.md :!yarn.lock :!*.lock :!*.png :!*.jpg :!*.svg
• Example: git diff -- ':!docs/' ':!*.md' ':!yarn.lock'
• The user's own ADR/docs additions are not what they want providers to review

1. Size-check the diff:

• Measure: wc -c diff.patch
• < 50KB: send as-is
• 50–150KB: warn the user "this is a large diff, providers may take 5–15 min" and continue
• > 150KB: tell the user, ask whether to truncate (head -c 150000) or split by package, do NOT silently send a giant payload
• Empty: stop and inform the user "no changes to review"

1. Create a Context Brief — a compact manifest that makes the handoff reproducible. Put it before the diff in every reviewer prompt; do not use it as an excuse to paste more raw files by default.

## Context Brief

Intent:
- User request:
- Review mode: multi-review
- Providers: <list the actual providers selected for this run>

Scope:
- Base ref:
- Changed files:
- Included files/docs:
- Excluded files/docs and reason:
- Diff bytes:

Repository signals:
- Relevant package/workspace:
- CLAUDE.md files read:
- ADRs/docs read:

Risk focus:
- Security:
- Data loss:
- Concurrency/state:
- API/contract:
- Tests/build:

Open questions:
- Items not verified before dispatch:

Keep the brief tiny for simple diffs. Escalate detail when the diff is over 50KB, spans more than 5 files, crosses package boundaries, includes untracked files, references ADRs/specs, or depends on conversation context the external providers cannot see.

Phase 2: Dispatch (with fallback)

Preferred: launch both reviewer agents in parallel using the Agent tool in a single message:

• antigravity-reviewer agent with the Context Brief + diff content
• codex-reviewer agent with the Context Brief + diff content
• Each agent performs its own multi-phase pipeline: Context → Prompt → Validation → Report

antigravity-reviewer requires agy installed + logged in and the Antigravity MCP server registered. If it's unavailable it will say so — present the codex-only result and note "antigravity skipped (agy not available)" rather than failing the whole review. To include Gemini instead/as well, also launch the gemini-reviewer agent.

Fallback when reviewer agents are unavailable (e.g., plugin not installed in this Claude Code session): dispatch directly via the project's dist/antigravity-run.js and dist/codex-run.js runner binaries using the ADR-050 dispatch pattern (single foreground blocking Bash call, direct backgrounding, per-PID wait, 25-min timeout):

GMCPT_TIMEOUT_MS=1500000 node ${CLAUDE_PLUGIN_ROOT}/dist/antigravity-run.js "$REVIEW_PROMPT" < diff.patch > /tmp/mr-antigravity.out 2> /tmp/mr-antigravity.err &
agy_pid=$!

GMCPT_TIMEOUT_MS=1500000 node ${CLAUDE_PLUGIN_ROOT}/dist/codex-run.js "$REVIEW_PROMPT" < diff.patch > /tmp/mr-codex.out 2> /tmp/mr-codex.err &
codex_pid=$!

agy_rc=0; wait $agy_pid || agy_rc=$?
codex_rc=0; wait $codex_pid || codex_rc=$?

Set the Bash tool's timeout parameter to 600000ms (10-min max). For diffs > 50KB, expect both providers to take real wall time — this is normal.

Do NOT use raw agy -p, gemini -p, or codex exec — those bypass the project's quota/transcript handling, Codex stdin handling (ADR-042), and PATH resolution (ADR-047). Use the runner binaries.

Phase 3: Verify each finding before presenting

For every finding from either provider at confidence ≥ 80:

1. Read the file at the cited line (use the Read tool)
2. Check whether the claim is actually true:

• "X function doesn't exist" → verify via Grep
• "Y line crashes when Z" → trace the actual code path
• "ADR-NNN is contradicted" → read the ADR

1. Mark each finding as one of:

• VERIFIED — claim holds against source
• REJECTED — false positive (with brief explanation of what the provider missed)
• UNVERIFIABLE — cannot confirm without runtime / external info; present as-is with a note

Phase 4: Resilient failure handling

When a provider fails (timeout, capacity exhaustion, exit code ≠ 0, 0-byte output):

• Do NOT silently drop it from the synthesis
• Surface the failure inline: "Antigravity failed (exit 1): <first 3 lines of stderr>"
• If both providers failed, say so explicitly and surface both stderr — don't pretend you have findings
• A single-provider review is still useful — present what you have, note what's missing

Phase 5: Present the synthesis

## Multi-Provider Review

**Context used:**
- Included: <files / packages>
- Excluded: <files / patterns and reason>
- Diff bytes: <N>

**Verified by both providers (highest confidence):**
- ⟨finding⟩ — Antigravity: 92, Codex: 88. Verified at <file>:<line>.

**Verified by Antigravity only:**
- ⟨finding⟩ — Confidence 85. Verified at <file>:<line>.

**Verified by Codex only:**
- ⟨finding⟩ — Confidence 90. Verified at <file>:<line>.

**Rejected (false positives caught during verification):**
- ⟨finding⟩ — Provider claimed X at <file>:<line>, but source shows Y. Skipped.

**Unverifiable:**
- ⟨finding⟩ — Cannot confirm without runtime; flagging for user attention.

**Provider stats:**
- Antigravity: ⟨N⟩ findings, ⟨V⟩ verified, ⟨R⟩ rejected. Status: ⟨ok | failed: ⟨reason⟩⟩
- Codex: ⟨N⟩ findings, ⟨V⟩ verified, ⟨R⟩ rejected. Status: ⟨ok | failed: ⟨reason⟩⟩

If you have to truncate either provider's response or skip verification due to time pressure, say so in the output. Hidden compromises mislead the user.