adversarial-collision

Adversarial Collision

The collide step applies P-deepen to every live branch: refuse the surface answer and find what tests, types, and lint cannot see. The adversary breaks; it never fixes — fixing your own findings is self-grading, the test-gaming failure mode.

When to use

• After superposition digests return and static early-kill has run, before verification results are ranked.
• NOT in decide mode — there is no adversary pass on a question; the judge weighs idea digests directly.

Protocol

1. Early-kill first, attack second. Run the project's lint/type/compile per branch (e.g. uv run ruff check . && uv run pyright) BEFORE dispatching any model. A branch that fails static checks is recorded to the failure taxonomy (death_reason: "failed static checks before collision") and excluded. The adversary is the most expensive judgment pass; it only attacks branches that could possibly win.
2. Dispatch per branch, in parallel, by path. ONE message, one fable Task per live branch, each given .pqa/branches/bN/ (or its worktree) — the adversary Reads the code and notes.md in its own context. Never inline branch code into dispatch prompts.
3. Attack the eight layers the verifier cannot reach:
   • solved the actual question vs a shallow restatement of it
   • input-distribution assumptions vs reality
   • behaviour at the boundaries no test exercises
   • security posture under adversarial input
   • complexity vs what it actually buys
   • failure-mode recoverability (vs silent data loss)
   • the promised contract vs what callers actually need
   • resource scaling (memory, time, lock contention)
4. Findings as structured JSON only: {branch_id, severity, category, title, detail, resolved: false} — detail names the trigger input/condition and why the verifier misses it. resolved is always false from the adversary.
5. Attack conviction-flagged branches harder. conviction: high protects a branch from early pruning — it buys attention, not leniency. "High-conviction branch failed under attack" is the best calibration row the system records.
6. Attack the branch's tests too. Would they pass on return None? Do they assert values or just shapes? Tests that would survive mutation are a critical finding — they compromise the verifier signal itself.
7. One defense pass, then score. Each attacked branch may answer its own findings (own context, reading its own findings JSON); then pqa.collision.score_all. A critical unresolved finding is a deadly hit.
8. Cross-branch comparison runs over findings JSON, never over code — one cheap second pass, only when genuinely needed.

Severity honesty

Severity	Meaning	Effect at collapse
critical	fails its purpose in a way the verifier misses (corruption, bypass, deadlock, silently wrong output)	unresolved = branch dies regardless of tests
high	real bug a competent reviewer blocks on	weighs against; not fatal
medium	suboptimal in a way that matters	tie-break material
low	style, naming	surface it; spend no budget

Critical inflation destroys the gate: if everything is critical, the orchestrator learns to discount the adversary, and the one finding that matters drowns.

Worked example

Branch b0, fixed-window rate limiter. Verifier: green, 91% coverage. The finding:

{"branch_id": "b0", "severity": "critical", "category": "correctness",
 "title": "burst-at-boundary admits 2x the limit",
 "detail": "Two windows sharing an edge each admit a full quota: 100 requests at
 09:59:59.9 plus 100 at 10:00:00.1 — 200 admitted in 200ms against a 100/min limit.
 No test exercises a window edge, so the verifier stays green.",
 "resolved": false}

b0's defense pass cannot resolve it without changing topology (sliding window), so the finding stands and b0 dies despite passing verification. That is the gate working: green tests are necessary, never sufficient.

Anti-patterns

• Politeness. Branches don't have feelings; soft findings are wasted fable tokens.
• Speculative theatre. A finding without a concrete trigger — specific input, condition, call sequence — is vibes, and the judge must discount it.
• Fixing. The adversary proposing patches collapses the attack/defense separation the loop depends on.
• Skipping the "obviously fine" branch. The verifier already certified looks-fine; the adversary's entire jurisdiction starts past that point.
• Severity theatre. Attacking style at low in volume crowds out the one critical that decides the run.