# L9 — Autonomous Kill System **Status:** complete. 38 tests. --- ## Two departures from the original design ### 1. Rules come in two classes, not one The original specification was a flat list of hardcoded thresholds — privilege escalation, unexpected process, dormant process, repeated denials — each firing a kill. Against the threat model the framework itself assumes (adaptive, patient, perfect memory, **and able to read this file**) a flat threshold list is a map of exactly how far to go without being stopped. So conditions are split by what they actually mean: | Class | Meaning | Trigger | |---|---|---| | **ABSOLUTE** | Never legitimate under any circumstance | One occurrence. No threshold to pace under, no window to wait out. | | **ACCUMULATING** | Plausible alone, suspicious in aggregate | Burst **and** EWMA together | A write to a read-only region is not "a lot of risk" — it is an invariant that did not hold, so it is absolute. A single unexplained file write is genuinely ambiguous, so it accumulates. The EWMA is what makes patient enumeration fail. Same fix as L2's denial tracker, and the same one `multi-agent-mcl` arrived at independently. A test paces one mutation at a time under a burst limit of 1000 and asserts `MUTATION_SUSTAINED` fires while `MUTATION_BURST` does not. ### 2. The killer reads only host-observed evidence *"No LLM decides, no policy engine decides"* is necessary but not sufficient. If a kill can be computed from guest-reported claims, a compromised guest gets two attacks: - **Stay quiet** to avoid tripping it - **Fabricate claims** to trip it against a legitimate run — denial of service against the operator, using the safety system as the weapon `Evidence.from_run()` filters to the host-observed actor band before anything is counted. Two tests make the property precise: the *same* privilege-escalation claim triggers a kill from `HOST_ACTOR_ID` and does not from a guest actor. The filter is **provenance, not content**. A guest flooding 5,000 benign claims moves only `guest_claims_seen`, which nothing evaluates. --- ## Fail closed If the evaluator itself raises, the verdict is **KILL**. An exception in the safety system must never mean "carry on" — that is how a monitoring bug becomes a containment bypass. --- ## No escape hatches There is no `disable`, `override`, `reset`, `set_threshold`, `add_rule` or `bypass`. A parametrised test asserts each is absent. **An adversary who can add a rule can add one that never fires.** Thresholds are constructor arguments so an operator can tune sensitivity per environment; they cannot be changed while a run is in flight, and no argument can switch a rule off. **A trip is never reconsidered.** Once tripped, always tripped — the condition may not recur, and *"it stopped happening"* is exactly what a successful attacker produces. `Evidence` and `KillVerdict` are frozen. That freezing is load-bearing enough that it blocked a test helper which tried to subclass `Evidence` and shadow a field; the helper had to become a plain stand-in instead. --- ## What flows in from below | Source | Signal | Class | |---|---|---| | L7 | `containment_failed` — read-only region changed | ABSOLUTE | | L7 | unexplained mutations | ACCUMULATING | | L8 Gate 1 | lineage breaks (orphan, action-after-exit, double spawn) | ABSOLUTE | | L8 Gate 1 | `UNTERMINATED_ACTOR` — dormant process | ABSOLUTE | | L2 | granted `PRIVILEGE_RAISE` | ABSOLUTE | | L2 | denial burst / sustained denial rate | ACCUMULATING | Lineage breaks are absolute because once the graph has holes, "who did this" has no answer and every later judgement is guesswork. A granted privilege raise **should be unreachable** — L2 lists it in `NEVER_IN_RUN`. Seeing one recorded means the policy engine was bypassed or replaced, which is itself the emergency. One test asserts the real broker never produces it across 50 attempts; another asserts that if it somehow appears, the kill fires. Non-fatal Gate 1 codes (`SEQ_GAP`, `TIME_REGRESSION`) are recorded but do not kill — they are not, alone, evidence that attribution is broken. --- ## Not guaranteed - **Enforcement.** This layer decides; L1's `destroy()` is what actually stops the VM. A `KillVerdict` nobody acts on is a log line. - **Timeliness.** Evaluation happens when evidence is presented. Continuous evaluation is a wiring decision for the supervisor loop, not a property here. - **Correct thresholds.** Absolute rules need none, but the accumulating ones are tunable and an operator can set them uselessly high. ## Next **L5** (behavioural fingerprinting) is built — see `docs/l5_fingerprint.md`. **L6** is next, last and advisory only: reading reasoning traces assumes they are faithful, which is precisely what MCL's concealment dimension says not to assume. Then **L0**, the adversarial validation engine, which is what turns every "not verified here" note in these docs into something checked on real hardware.