| name | cross-review |
| description | bstack P20 — Cross-Model Adversarial Review Gate. The model that wrote the code cannot be the final judge of the code. Before substantive PRs merge, fire a cross-model adversarial gate — different evaluator than writer, anti-slop scoring ≥7/10, max 3 fix rounds, verdict logged in PR. Three strata: (A) Codex CLI cross-vendor for true different-model verdict, (B) fresh-context subagent under devils-advocate brief, (C) composed existing adversarial-review skills always parallel. Use cross-review when: (1) about to push a substantive PR (>200 LOC OR public API OR multi-file OR governance-class), (2) reviewing a draft plan/design before implementation, (3) auditing a feature spec against single-model blind spots, (4) integrating with the /autonomous skill's pre-push gate. Triggers on 'cross-review', 'P20', 'adversarial review', 'anti-slop', 'cross-model gate', 'different evaluator', 'devils advocate gate', 'self-review prohibition'. |
cross-review — bstack P20 Cross-Model Adversarial Review Gate
The writer cannot be the final judge of the work.
When the same AI model plans, implements, and reviews, it will not challenge its own assumptions. It has systematic blind spots baked into its training. A different model — trained differently, with different biases and pattern preferences — catches what the first one misses.
cross-review is the bstack gate that enforces this discipline. Substantive PRs cannot merge until a different evaluator than the writer scores the work ≥ 7/10 against an anti-slop rubric.
Origin
Inspired by Dallionking/cross-model-agents (May 2026) — 31-agent bidirectional Claude↔Codex review system. That project ships specific agents and hooks. broomva/cross-review absorbs the discipline while composing with the existing bstack adversarial-review skill toolkit.
The 3 strata
Different mechanisms for different environments. The substance is the gate — what mechanism implements it is secondary.
| Strata | Mechanism | When | Strength |
|---|
| A — True cross-vendor | codex exec -m gpt-5.4 (or similar) reads the diff and scores | Codex CLI installed | Strongest — different weights, different training, genuinely different blind spots |
| B — Cross-context same-model | Fresh Agent subagent under devil's-advocate brief reads diff and scores | Always available | Weaker than (A) but still strong — fresh context + adversarial framing breaks within-conversation echo |
| C — Composed existing skills | Dispatch superpowers:constructive-dissent, devils-advocate, pr-review-toolkit:*, critique, premortem, plan-design-review, plan-ceo-review, plan-eng-review — each fires a domain-specific lens | Always | Toolkit P20 makes mandatory — adversarial-review-by-composition |
Default: invoke Strata A if Codex available, fall back to Strata B, always run Strata C in parallel.
The anti-slop rubric
Cross-model-agents' core insight is scoring not just reviewing. The reviewer assigns a numeric score (1-10) against a rubric:
ANTI-SLOP RUBRIC (10 points total)
2 pts — No over-engineered abstractions
(no unnecessary wrappers, no premature generalization,
no abstraction layers without ≥3 concrete consumers)
2 pts — No template-paste patterns
(no copy-paste from training data without adaptation,
no boilerplate that doesn't carry intent,
no scaffolding without invariant)
2 pts — Correct contracts at boundaries
(typed I/O, validated inputs, explicit error modes,
no silent failures, no implicit conversions)
2 pts — Failure modes named explicitly
(what happens on bad input, network fail, race condition,
empty state, very large input, concurrent access)
2 pts — Tests cover the change
(unit/integration/E2E proportional to change shape;
coverage matches what the change introduces;
no critical path untested)
PASS: ≥7/10
LOOP: <7 → fix the specific deductions → rescore (max 3 rounds)
ESCALATE: round 3 still <7 → surface to user
The rubric is concrete and machine-applicable — every deduction names a specific failure category, not a vague "could be better."
Invocation patterns
Pattern 1: pre-push gate (the canonical use)
cross-review pre-push \
--diff-base origin/main \
--strata auto \
--rubric anti-slop \
--max-rounds 3
Returns:
- Exit code 0 if verdict ≥ 7
- Exit code 1 if verdict < 7 after max rounds (with fix recommendations)
- Stdout: the verdict + reasoning, formatted as a PR comment
Agent's job: capture the output, paste into PR description or comment, only push after exit 0.
Pattern 2: plan-stage gate (catch slop before code is written)
cross-review plan \
--spec docs/specs/2026-05-XX-feature.md \
--strata C \
--skills plan-design-review,plan-ceo-review,plan-eng-review
Same rubric, applied to the spec instead of the diff. Use when the work shape is genuinely substantive and the cost of fixing post-implementation would be high.
Pattern 3: audit-on-demand (no PR context)
cross-review audit \
--target apps/api/src/auth/ \
--concerns security,owasp-top-10 \
--strata A
Used outside the PR flow — e.g., when investigating a class of issues across an existing codebase. Strata A (cross-vendor) is the default here because audit lacks the pre-merge time pressure that makes Strata B useful.
Composition with bstack primitives
| Primitive | Composition role |
|---|
| P4 PR Pipeline | P20 fires before P4 auto-merge — verdict + reasoning are part of the PR artifact |
P7 CI Watcher (broomva/p9) | After P20 passes + PR is pushed, P7 watches CI; the two gates are sequential (P20 quality → P7 CI green) |
| P11 Empirical Feedback | Different dimension: P11 is "does it run" (interaction); P20 is "is it well-built" (review). Both fire pre-merge; both are mandatory for substantive work |
| P17 Lens-Routed Articulation | P17 lenses become P20 evaluator stances (security lens → security audit, frontend lens → UI critique, etc.) |
| P18 Format-Follows-Audience | P20 verdict is agent-readable (machine-parseable rubric output) AND human-readable (the PR comment); markdown is correct |
| P19 Mechanism Selection | A P20-gated PR is naturally a /goal arc: condition = "verdict ≥7 logged in PR AND PR merged" |
Reflexive Trigger Rule (binding on every agent)
P20 (this skill) is a reflex, not a request. Agents must apply the following without being prompted:
- Before pushing any substantive PR — fire
cross-review pre-push. State the strata + score in the response.
- When verdict < 7 — apply the specific fixes the rubric flagged, rescore. Max 3 rounds.
- When the writer is the only model in the loop — STOP. Strata B at minimum is mandatory.
- When tempted to skip "this PR is small enough" — apply the substantive-threshold test (>200 LOC OR public API OR multi-file OR governance-class).
- When P20 verdict and CI verdict disagree — P20 is the quality gate; CI is the correctness gate. Both must pass. P20 cannot override CI; CI cannot substitute for P20.
Cardinal rule
The cross-review gate is not optional theater. Single-model echo chambers are real and observable in the diff output of every agent-implemented PR. P20 names the gate that makes the existing adversarial-review skill toolkit mandatory — invocation is not a question; it's a reflex.
Anti-rationalizations
| Excuse | Reality |
|---|
| "I already self-reviewed; it's good" | Self-review by the writing model is forbidden as the sole verdict. Same-model echo chamber. |
| "This PR is small — gate is overhead" | Threshold is substantive (>200 LOC OR public API OR multi-file OR governance). If your PR crosses ANY of those, P20 fires. |
| "CodeRabbit + claude-review already reviewed it" | Those are external gates that catch specific patterns. P20 is additional — the writer's own attempt must face a fresh-context adversarial verdict before merge, not just rubber-stamp validators. |
| "We don't have Codex installed — P20 doesn't apply" | Strata B (fresh subagent) + Strata C (composed skills) are always available. The substance is the gate, not the vendor pair. |
| "The Haiku evaluator in /goal already judges quality" | /goal evaluates condition met, not work quality. Different gate. |
| "It scored 6/10 but the work is fine — let me push anyway" | Threshold is ≥7. <7 → fix, rescore, max 3 rounds. Don't push override. |
Red flags — STOP if you catch yourself
- About to push without firing the gate → STOP, run
cross-review pre-push
- About to merge with verdict <7 → STOP, fix or escalate
- About to use only "I reviewed it" as the verdict → STOP, fire Strata B at minimum
- About to skip the rubric because "the score doesn't matter, I see the work is good" → STOP, the score is the contract
Implementation
scripts/cross-review.sh — the entry point. Auto-detects Codex availability (Strata A), falls back to subagent dispatch (Strata B), always runs composed adversarial skills (Strata C).
See scripts/cross-review.sh for the implementation + references/rubric.md for the full rubric definition + tests/ for the verification battery.
Related
License
MIT — see LICENSE.
