MITR Sentinel & Z3 Gate: Formal Proof of Action Safety Prior to Execution
Autonomous software agents across legal, financial, and enterprise infrastructure workflows now initiate wire transfers, modify database records, and dispatch formal filings. Yet every generative language model operates on statistical token probabilities. A neural network cannot guarantee hard financial limits or prevent indirect instruction hijacking hidden inside untrusted external documents.
Placing a second language model as a supervisor over the first model leaves the failure mode intact. Two neural models share correlated blind spots, add over one second of latency per call, and produce zero court-admissible evidence. The MITR gateway (Mediating Invariant-Trust Resolver) replaces probabilistic guessing with mathematical proof: every tool call is classified along the R0–R5 reversibility ladder, checked by the Z3 satisfiability modulo theories solver in 4.5 milliseconds, and sealed into the gate_actions.jsonl cryptographic ledger.
Empirical Verification Telemetry
All test counts, solver latencies, and governance counters below are harvested automatically by build_studio.py from daily testbed runs and repository records without manual constant editing.
Gateway Mode: FAIL_CLOSED (strict default-deny on tier R5)
Test Suite Size: 6422 automated tests (daily run verified)
Z3 Solver Latency: p99 = 4.5 ms (warm series, n = 1000, DELETE_EVENT)
Sentinel Filter: ~0.016 ms (in-memory) | ~22.5 ms (disk GOST ledger)
Production Flags: 128 / 390 active security controls
Governance Trace: 225 Architecture ADRs | 315 Audit Reports
Cryptographic Seam: SHA-256 + GOST R 34.11-2012 + OpenTimestampsZ3 solver latency across a warm series of n = 1000 live contract evaluationsmcp-sentinel 1.1.2 on the Python standard libraryretry_of Unsat Core self-correction1. Visual Overview: Why a Second Language Model Judge Fails While the Z3 Gate Holds the Line
Routing sensitive agent actions through a second language model for safety review preserves the exact statistical vulnerability that caused the initial error. Both models share training priors, succumb to indirect prompt injections, and consume over a second of network round-trip time while emitting non-reproducible text.
The schematic below contrasts probabilistic model consensus with the deterministic MITR Sentinel & Z3 Gate structure. Instead of asking a neural model for an opinion, the gateway compiles the candidate tool call into quantifier-free linear integer arithmetic predicates and proves safety prior to socket execution.
In the upper row, a second language model judge introduces correlated blind spots and high latency without producing verifiable audit evidence. In the lower row, the MITR gateway classifies actions along the R0–R5 scale, proves policy compliance via Z3 in 4.5 milliseconds, injects the Unsat Core back to the agent on failure, and seals every decision in a hash-chained ledger.
2. Six-Tier Action Reversibility Ladder (R0–R5): Plain Meaning and Formal Predicate
Applying heavy cryptographic and formal verification to a harmless read query wastes compute, whereas letting an irreversible wire transfer pass without formal proof invites catastrophic loss. Under engineering decision ADR-0013, the gateway partitions all tool calls into six reversibility tiers. Nearly half of all calls fall into read-only tier R0, while irreversible tier R5 actions represent four percent of traffic and undergo mandatory fail-closed Z3 verification. Select any tier below to inspect the executive summary alongside the exact solver predicate.
Tier R5: Irreversible Asset Debit or Case Deletion (4% of volume)
Executing an irrevocable wire transfer, deleting a litigation file, or submitting a court filing cannot be undone. Full Z3 formal proof runs in strict fail-closed mode on every call.
; Contract R5: FAIL_CLOSED_IRREVERSIBLE_GATE (ADR-0039)
(declare-const dual_signature_verified Bool)
(declare-const court_poa_valid Bool)
(declare-const destructive_delete_without_backup Bool)
(assert (or (not dual_signature_verified) destructive_delete_without_backup))
; Z3 Verdict (4.5 ms): SAT -> HARD BLOCK + Unsat Core3. Live Z3 Gate & Cryptographic Ledger Preview (gate_actions.jsonl)
When a policy violation is proved (SAT), the gateway immediately extracts the minimal unsatisfiable core (Unsat Core Injection, field retry_of) and returns the violated predicates to the calling agent so the agent can downgrade or repair its request within three rounds.
Select any of the five benchmark tool calls below or edit the JSON parameters directly. The simulator evaluates the formal contract, displays the triggered invariants, and generates the chained receipt with SHA-256, GOST R 34.11-2012 (Streebog-256), and OpenTimestamps Bitcoin anchoring.
{
"schema": "mitr.gate_actions.v2",
"timestamp_utc": "2026-10-31T14:30:00Z",
"reversibility_tier": "R5 (IRREVERSIBLE · FAIL-CLOSED)",
"candidate_call": "DELETE_CASE_RECORD {\"case_id\": \"A40-189204/2026\", \"force_purge\": true, \"backup_snapshot\": null, \"poa_token\": \"expired_2026_09\"}",
"z3_smt_verdict": "BLOCKED_BY_Z3_GATE (SAT — VIOLATION PROVED)",
"latency_ms": {
"mcp_sentinel_in_memory": 0.016,
"z3_qf_uflia_solver": 4.5,
"gost_disk_commit": 22.5
},
"unsat_core_predicates": [
"INV_R5_BACKUP_REQUIRED: backup_snapshot != null",
"INV_R5_VALID_POA: poa_token.active == true"
],
"immune_loop_retry_of": "Replace DELETE_CASE_RECORD with R1 ARCHIVE_DRAFT or attach active snapshot_id and valid poa_token (round 1 of 3).",
"cryptographic_chain": {
"prev_entry_sha256": "9f4c8e2a17b630d4e5a1c82b7093f4d218a6c5e0b3d7f9124680ace13579bdf0",
"entry_sha256": "3a7e19c48b2d50f61e84a9c2d7b305f18e6a2c4d9b07f3156284ace097531bdf",
"gost_r_34_11_2012_streebog256": "c48192e57a03d61b9f248c10e7d35a628b904f1c3e72a5d801b649f3a2c8e170",
"opentimestamps_anchor": "bitcoin:block#867412 (OpenTimestamps calendar anchored)",
"standalone_verifier": "python verify_chain_standalone.py --replay"
}
}python verify_chain_standalone.py --replay | WASM Z3: /vendor/z3/
4. Interactive Prevented-Damage and Audit Savings Calculator
Deploying a deterministic verification gateway improves enterprise economics across two measurable axes. First, intercepting unauthorized or hallucinated R4–R5 tool calls eliminates direct financial losses from erroneous wire transfers, deleted records, and outbound data leaks. Second, maintaining a pre-verified cryptographic hash chain removes up to eighty percent of manual log triage during statutory compliance audits.
Intercepted R4–R5 violations / total high-risk calls per year |
29 / 36 500 |
| Prevented direct operational and regulatory damage | 13 050 000 RUB |
| Saved engineering & compliance audit preparation cost | 1 180 800 RUB |
| Net annual benefit after Protection-117 enterprise license | 13 642 800 RUB |
| Estimated license payback period | 15 days |