| # 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. | |