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description: Adversarial dual-review convergence loop — two independent model reviewers must both approve before code ships.

Santa Loop

Adversarial dual-review convergence loop using the santa-method skill. Two independent reviewers — different models, no shared context — must both return NICE before code ships.

Purpose

Run two independent reviewers (Claude Opus + an external model) against the current task output. Both must return NICE before the code is pushed. If either returns NAUGHTY, fix all flagged issues, commit, and re-run fresh reviewers — up to 3 rounds.

Usage

/santa-loop [file-or-glob | description]

Workflow

Step 1: Identify What to Review

Determine the scope from $ARGUMENTS or fall back to uncommitted changes:

git diff --name-only HEAD

Read all changed files to build the full review context. If $ARGUMENTS specifies a path, file, or description, use that as the scope instead.

Step 2: Build the Rubric

Construct a rubric appropriate to the file types under review. Every criterion must have an objective PASS/FAIL condition. Include at minimum:

Criterion	Pass Condition
Correctness	Logic is sound, no bugs, handles edge cases
Security	No secrets, injection, XSS, or OWASP Top 10 issues
Error handling	Errors handled explicitly, no silent swallowing
Completeness	All requirements addressed, no missing cases
Internal consistency	No contradictions between files or sections
No regressions	Changes don't break existing behavior

Add domain-specific criteria based on file types (e.g., type safety for TS, memory safety for Rust, migration safety for SQL).

Step 3: Dual Independent Review

Launch two reviewers in parallel using the Agent tool (both in a single message for concurrent execution). Both must complete before proceeding to the verdict gate.

Each reviewer evaluates every rubric criterion as PASS or FAIL, then returns structured JSON:

{
  "verdict": "PASS" | "FAIL",
  "checks": [
    {"criterion": "...", "result": "PASS|FAIL", "detail": "..."}
  ],
  "critical_issues": ["..."],
  "suggestions": ["..."]
}

The verdict gate (Step 4) maps these to NICE/NAUGHTY: both PASS → NICE, either FAIL → NAUGHTY.

Reviewer A: Claude Agent (always runs)

Launch an Agent (subagent_type: code-reviewer, model: opus) with the full rubric + all files under review. The prompt must include:

• The complete rubric
• All file contents under review
• "You are an independent quality reviewer. You have NOT seen any other review. Your job is to find problems, not to approve."
• Return the structured JSON verdict above

Reviewer B: External Model (Claude fallback only if no external CLI installed)

First, detect which CLIs are available:

command -v codex >/dev/null 2>&1 && echo "codex" || true
command -v gemini >/dev/null 2>&1 && echo "gemini" || true

Build the reviewer prompt (identical rubric + instructions as Reviewer A) and write it to a unique temp file:

PROMPT_FILE=$(mktemp /tmp/santa-reviewer-b-XXXXXX.txt)
cat > "$PROMPT_FILE" << 'EOF'
... full rubric + file contents + reviewer instructions ...
EOF

Use the first available CLI:

Codex CLI (if installed)

codex exec --sandbox read-only -m gpt-5.4 -C "$(pwd)" - < "$PROMPT_FILE"
rm -f "$PROMPT_FILE"

Gemini CLI (if installed and codex is not)

gemini -p "$(cat "$PROMPT_FILE")" -m gemini-2.5-pro
rm -f "$PROMPT_FILE"

Claude Agent fallback (only if neither codex nor gemini is installed) Launch a second Claude Agent (subagent_type: code-reviewer, model: opus). Log a warning that both reviewers share the same model family — true model diversity was not achieved but context isolation is still enforced.

In all cases, the reviewer must return the same structured JSON verdict as Reviewer A.

Step 4: Verdict Gate

• Both PASS → NICE — proceed to Step 6 (push)
• Either FAIL → NAUGHTY — merge all critical issues from both reviewers, deduplicate, proceed to Step 5

Step 5: Fix Cycle (NAUGHTY path)

1. Display all critical issues from both reviewers
2. Fix every flagged issue — change only what was flagged, no drive-by refactors
3. Commit all fixes in a single commit:

   fix: address santa-loop review findings (round N)
   

4. Re-run Step 3 with fresh reviewers (no memory of previous rounds)
5. Repeat until both return PASS

Maximum 3 iterations. If still NAUGHTY after 3 rounds, stop and present remaining issues:

SANTA LOOP ESCALATION (exceeded 3 iterations)

Remaining issues after 3 rounds:
- [list all unresolved critical issues from both reviewers]

Manual review required before proceeding.

Do NOT push.

Step 6: Push (NICE path)

When both reviewers return PASS:

git push -u origin HEAD

Step 7: Final Report

Print the output report (see Output section below).

Output

SANTA VERDICT: [NICE / NAUGHTY (escalated)]

Reviewer A (Claude Opus):   [PASS/FAIL]
Reviewer B ([model used]):  [PASS/FAIL]

Agreement:
  Both flagged:      [issues caught by both]
  Reviewer A only:   [issues only A caught]
  Reviewer B only:   [issues only B caught]

Iterations: [N]/3
Result:     [PUSHED / ESCALATED TO USER]

Notes

• Reviewer A (Claude Opus) always runs — guarantees at least one strong reviewer regardless of tooling.
• Model diversity is the goal for Reviewer B. GPT-5.4 or Gemini 2.5 Pro gives true independence — different training data, different biases, different blind spots. The Claude-only fallback still provides value via context isolation but loses model diversity.
• Strongest available models are used: Opus for Reviewer A, GPT-5.4 or Gemini 2.5 Pro for Reviewer B.
• External reviewers run with --sandbox read-only (Codex) to prevent repo mutation during review.
• Fresh reviewers each round prevents anchoring bias from prior findings.
• The rubric is the most important input. Tighten it if reviewers rubber-stamp or flag subjective style issues.
• Commits happen on NAUGHTY rounds so fixes are preserved even if the loop is interrupted.
• Push only happens after NICE — never mid-loop.