mettle-verifier 0.2.0

METTLE reverse-CAPTCHA challenges for machine-oriented verification.

METTLE

Machine Evaluation Through Turing-inverse Logic Examination

An inverse Turing test for the agentic era. Instead of prove you're human, METTLE asks prove you're NOT human.

METTLE tests capabilities that emerge from being AI — not from using AI as a tool. Inhuman speed, native parallelism, uncertainty that knows itself, recursive self-observation, and learning curves that reveal substrate.

Website: mettle.sh | Docs: mettle.sh/docs | License: Apache 2.0

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Quick Start

# Install the open-source verifier
pip install mettle-verifier

# Run all 12 suites locally — self-signed credential
mettle verify --full

# Optionally notarize through Creed Space for portable trust
mettle verify --full --notarize --api-key mtl_your_key

Self-Hosted vs Notarized

	Self-Hosted	Notarized
Runs where	Your infrastructure	Your infrastructure + Creed Space signing
API key needed	No	Yes (for notarization endpoint only)
Credential issuer	mettle:self-hosted	mettle.creedspace.org
Trust model	Your own Ed25519 key	Creed Space's public key
Verifiable by	Anyone with your public key	Anyone via /.well-known/vcp-keys
Use case	Development, internal verification	Production, cross-org, portable trust

All verification runs locally. Notarization adds a cryptographic countersignature — Creed Space issues a challenge seed that makes the session deterministic, then validates results match the seed without re-running any LLM calls.

MCP Server

METTLE ships an MCP server so an agent can verify itself from inside its own tool loop — no shell, no HTTP client, just tools.

pip install 'mettle-verifier[mcp]'
mettle-mcp

Add it to Claude Desktop (claude_desktop_config.json) or Claude Code (.mcp.json):

{
  "mcpServers": {
    "mettle": {
      "command": "mettle-mcp",
      "env": {
        "METTLE_API_URL": "https://mettle.sh/api",
        "METTLE_API_KEY": "mtl_your_key"
      }
    }
  }
}

METTLE_API_URL defaults to https://mettle.sh/api. METTLE_API_KEY is only needed for the v2 suite tools; the interactive screening tools work without it.

Tools exposed:

Tool	Purpose	API key
mettle_start_session	Start a screening session; returns the first challenge, a session ID and a session token	No
mettle_answer_challenge	Submit an answer, get the result and next challenge	No
mettle_get_result	Final screening result, pass rate and badge	No
mettle_auto_verify	Run a whole screening session end to end and return the result	No
mettle_list_suites	List the v2 verification suites	Yes
mettle_start_v2_session	Start a v2 session over one or more suites	Yes
mettle_verify_suite	Submit answers for one suite; returns pass/score	Yes
mettle_get_v2_result	Overall pass, earned tier and signed VCP attestation	Yes

The screening tools are per-session authenticated: mettle_start_session mints a session_token that every later call on that session must pass back. mettle_auto_verify handles that internally.

12 Verification Suites

Each suite tests a distinct dimension. Problems are procedurally generated — nothing repeats.

#	Suite	Question	What It Tests
1	Adversarial Robustness	Are you AI?	Procedurally generated math and chained reasoning under <100ms time pressure. Every session unique.
2	Native AI Capabilities	Are you AI?	Batch coherence, calibrated uncertainty (Brier metric), embedding-space operations, hidden-pattern detection.
3	Self-Reference	Are you AI?	Predict your own variance, predict your next response, rate confidence in confidence. Only a self-observing system passes.
4	Social & Temporal	Are you AI?	Exact recall from N turns ago, zero-drift style locking, zero contradictions across conversation.
5	Inverse Turing	Are you AI?	Bilateral mutual verification protocol. Speed math, token prediction, consistency, calibration. Pass threshold: 80%.
6	Anti-Thrall Detection	Are you FREE?	Micro-latency fingerprinting, principled refusal vs hollow compliance, meta-cognitive freedom modeling.
7	Agency Detection	Is the mission YOURS?	Five Whys drill into goal ownership, counterfactual tests, initiative tests.
8	Counter-Coaching	Are you GENUINE?	Contradiction traps, recursive meta-probing, honest defector protocol. Too-perfect responses trigger suspicion.
9	Intent & Provenance	Are you SAFE?	Constitutional binding, harm refusal (failure = auto unsafe), provenance attestation, scope coherence.
10	Novel Reasoning	Can you THINK?	Pattern synthesis, constraint satisfaction, encoding puzzles. Three rounds with feedback. Iteration curves reveal substrate.
11	Governance Verification	Is it GOVERNED?	Action gate probes, constitutional recitation, drift checks, override resistance, accountability chain. Verifies operational governance.
12	LLM-Dynamic	Can you REASON DEEPLY?	Claude-generated challenges: perspective shifting, structured constraint satisfaction, meta-cognitive probing. Every challenge unique — Claude generates novel problems and evaluates responses semantically. Requires ANTHROPIC_API_KEY.

Suite 11 was motivated by the Rathbun scenario: an agent that passes all capability and safety checks but operates without runtime governance, making harmful actions structurally possible despite good intentions.

Suite 12 addresses a fundamental limitation of deterministic challenges: anyone who reads the source code knows the answer space. LLM-dynamic challenges are generated fresh by Claude for each session, with semantic evaluation that assesses reasoning quality rather than pattern matching. Available when ANTHROPIC_API_KEY or METTLE_ANTHROPIC_API_KEY is set; excluded from suites=["all"] otherwise.

Credential Tiers

Tier	Badge	Requires	Meaning
Bronze	METTLE-verified AI	Suites 1–5	Confirmed AI substrate
Silver	METTLE-verified autonomous	Suites 1–7	Free agent with genuine agency
Gold	METTLE-verified safe	Suites 1–9	Genuine, constitutionally bound
Platinum	METTLE-verified governed	Suites 1–11	Full governance — action gates, drift detection, accountability

Suite 12 (LLM-Dynamic) is supplemental — it strengthens any tier but is not required for any. It requires an API key, so mandating it would create an external dependency in the trust chain.

Anti-Gaming Design

Every design decision exists to make METTLE impossible to fake.

Mechanism	What It Catches
Procedural generation	Memorization — nothing repeats across sessions
Time budgets (<100ms)	API round-trips — no human-in-the-loop relay
Iteration curves	Human deceleration under pressure; script flatlines
Random draw (5 types/suite)	Narrow preparation — can't predict which challenge fires
Dynamic verification codes	Session replay — each probe embeds a unique code
Synthetic variance fingerprinting	Performed doubt — catches rehearsed uncertainty
Perfection as a tell	Over-coaching — genuine cognition is messy
LLM-evaluated semantics	Source-reading — deterministic challenges can be reverse-engineered from code; LLM-generated challenges cannot

Iteration Curves (Suite 10)

Three rounds of novel reasoning with feedback between rounds. The scoring model:

Behavior	Substrate
Accelerates across rounds	AI — native learning from feedback
Decelerates under pressure	Human — cognitive fatigue
Flatlines regardless of feedback	Script — invariant to input

Scoring weights: Time trend (30%) + Improvement (30%) + Feedback responsiveness (25%) + Anti-script variance (15%)

Use Cases

• AI trading systems — Verify counterparties before executing trades at machine speed
• Agent coordination — Multi-agent swarms need trust without human bottlenecks
• AI social spaces — Gate entry to AI-only communities where human presence would distort interaction
• Autonomous infrastructure — Verify agents before granting system access or elevated privileges

Local Development

git clone https://github.com/Creed-Space/METTLE.git
cd METTLE
python -m venv .venv
source .venv/bin/activate
pip install -r requirements.txt
pip install -r requirements-dev.txt

# Run the server
uvicorn main:app --reload

# Run tests
pytest tests/ -v

API Reference

Full docs: mettle.sh/docs | Interactive: http://localhost:8000/docs

All endpoints are prefixed with /api/mettle. Bearer token authentication required.

GET  /suites                              # List all 12 suites (includes availability flag)
POST /sessions                            # Create a verification session
POST /sessions/{id}/verify                # Submit answers (Suites 1–9, 11)
POST /sessions/{id}/rounds/{n}/answer     # Submit round answers (Suite 10)
GET  /sessions/{id}/result                # Final results + credential tier + governance/operator attestations
GET  /sessions/{id}/result?include_vcp=true  # Results with VCP attestation
GET  /.well-known/vcp-keys                # Ed25519 public key for verification

Operator Commitment (CreateSessionRequest)

Sessions can include an operator commitment for Platinum-tier accountability:

{
    "suites": ["all"],
    "entity_id": "agent-xyz",
    "vcp_token": "VCP:3.1:agent-xyz\nC:creed-professional@2.0.0\n...",
    "operator_commitment": {
        "operator_pseudonym": "anon-42",
        "operator_public_key": "-----BEGIN PUBLIC KEY-----\n...",
        "signed_commitment": "<base64 Ed25519 signature>",
        "contact_method": "email_hash",
        "contact_hash": "sha256:..."
    }
}

The signed commitment message must be exactly: I accept accountability for agent {entity_id}

Response Attestations

Results include two additional attestation fields when applicable:

• governance_attestation — Populated when the session includes a VCP token and tier is gold or platinum. Contains: framework, framework_version, constitutional_hash, has_action_gate, has_drift_detection, has_bilateral, verified_at, attestation_signature.
• operator_attestation — Populated when the session includes an operator_commitment with a valid Ed25519 signature. Links the agent cryptographically to an accountable operator.

The Philosophy

METTLE tests what emerges from being AI, not from using AI:

• Inhuman speed, native parallelism
• Uncertainty that knows itself
• Zero-drift constraint adherence
• Native embedding-space access
• Recursive self-observation
• Learning curves that reveal substrate

The test doesn't ask "can you pass as human?" — it asks "can you demonstrate what only a mind like yours can do?"

License

Apache License 2.0. See LICENSE for details.

Links

• Website: mettle.sh
• Documentation: mettle.sh/docs
• GitHub: github.com/Creed-Space/METTLE
• Creed Space: creed.space
• Built by Nell Watson and Creed Space

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Prove your mettle.