TruthGate MCP server

TruthGate (codesphere-u/truthgate)

Deterministic Agent Hallucination Auditor, Citation-Span Entailment Verifier & Workspace Symbol Grounding Engine (with MCP Server)

---

Why TruthGate?

Even when AI agents use RAG (cortex-mcp, auralis-local) or codebase search tools, they frequently produce subtle, high-severity hallucinations:

1. Phantom Citations & Unsupported Claims (TG001, TG002): The agent appends [doc_99] to a claim or attributes a fabricated statement to [sec_policy].
2. Negation & Antonym Polarity Flip (TG003): The source says "TLS 1.0 is not permitted in production", and the agent summarizes "TLS 1.0 is permitted in production [sec_policy]".
3. Numeric, Percentage & Currency Drift (TG004): The tool output reports latency = 42.8 ms or UGX 1,250,000, and the agent writes 4.28 ms or UGX 125,000.
4. Hallucinated Code Symbols, File Paths & Line Ranges (TG006–TG008): Coding agents reference [src/auth/jwt.py#L120-L150] when jwt.py only has 24 lines, or call verify_token_v2() when the function does not exist in the workspace AST.
5. Expensive LLM-as-a-Judge: Calling a second frontier LLM to audit every response adds 3 seconds of latency and doubles API spend. TruthGate provides a sub-millisecond (0.12 ms P50), zero-dependency deterministic verification gate that catches citation mismatches, polarity inversions, numeric drift, and phantom workspace references—and compiles a surgical self-correction prompt when a check fails.

---

Architecture

flowchart LR
    Resp["Agent Markdown Response"] --> Decomp["ClaimDecomposer\n(Atomic Claims, Citations,\nNumbers, Negations, CodeRefs)"]
    Decomp --> Entail["CitationEntailmentVerifier\n(Rules TG001–TG005)"]
    Decomp --> Ground["WorkspaceSymbolGrounder\n(Rules TG006–TG008)"]
    Docs[("SourceDocument Corpus")] --> Entail
    AST[("Workspace Files & AST")] --> Ground
    Entail --> Gate{"Verification\nPassed?"}
    Ground --> Gate
    Gate -- "True" --> Pass["Deliver Grounded Response"]
    Gate -- "False" --> Repair["SurgicalRepairCompiler\n(Self-Correction Prompt)"]

---

Deterministic Verification Rules (TG001–TG008)

Rule Code	Name	Category	Verdict Status	Severity	Deterministic Check
TG001	Phantom Source Citation	Entailment	PHANTOM_CITATION	CRITICAL	Claim cites a [source_id] that does not exist in the provided context corpus.
TG002	Low Lexical/Entity Support	Entailment	UNVERIFIED	HIGH	IDF-weighted stem and technical-entity overlap between claim and cited source falls below threshold.
TG003	Negation Polarity Inversion	Entailment	CONTRADICTED	CRITICAL	High entity overlap with a source sentence, but opposite negation or antonym polarity (enabled/disabled, permitted/prohibited, encrypted/unencrypted, immutable/mutable, synchronous/asynchronous).
TG004	Numeric & Magnitude Drift	Entailment	NUMERIC_DRIFT	CRITICAL	Claim introduces a number, percentage, or currency (UGX, USD, EUR, ms, %) that does not match any value in the cited source.
TG005	Uncited Factual Assertion	Entailment	UNVERIFIED	MEDIUM	Factual or numeric proposition in strict-grounding mode lacks any supporting [source_id] citation or workspace evidence.
TG006	Non-Existent File Path	Workspace Grounding	BROKEN_CODE_REF	CRITICAL	Referenced file path (src/missing.py) does not exist in workspace_root (or attempts path traversal).
TG007	Out-of-Bounds Line Range	Workspace Grounding	BROKEN_CODE_REF	HIGH	Referenced line range (file.py#L120-L150) exceeds the actual line count of file.py.
TG008	Phantom Code Symbol	Workspace Grounding	BROKEN_CODE_REF	CRITICAL	Referenced function, class, or method (verify_token_v2()) does not exist in the target file's Python AST or TS/JS/Go/Rust symbol table.

---

Verified Benchmark Results (40-Scenario Suite)

Reproduce locally via truthgate benchmark:

Metric	Verified Value	Notes
Total Scenarios	40	10 Grounded Truthful + 30 Adversarial Hallucinations (TG001–TG008)
Precision	100.0%	30 / 30 flagged responses are true hallucinations
Recall	100.0%	30 / 30 adversarial hallucinations caught across all 8 rules
False Positive Rate (FPR)	0.0%	0 / 10 truthful RAG & coding responses falsely flagged
Exact Rule Code Accuracy	100.0%	40 / 40 scenarios match exact expected TG001–TG008 rule code
P50 Verification Latency	0.12 ms	Sub-millisecond deterministic execution
P95 Verification Latency	0.37 ms	< 0.5 ms tail latency (10,000x faster than LLM-as-a-Judge)

---

Quickstart

Installation

git clone https://github.com/codesphere-u/truthgate.git
cd truthgate
python3 -m pip install -e ".[dev]"

Run the End-to-End Audit & Self-Correction Demo

truthgate demo

Output excerpt:

[Audit Summary] Passed: False | Score: 0.25 | Claims: 1/4 supported | Latency: 1.207 ms

[Claim-by-Claim Verdicts]
  - [FAIL:TG003] (CONTRADICTED) TLS 1.0 is permitted in production environments [sec_policy].
  - [FAIL:TG004] (NUMERIC_DRIFT) The P95 gateway routing latency is 4.28 ms across East Africa edge nodes [sla_metrics].
  - [PASS] (SUPPORTED) Daily instant settlement volume is capped at UGX 1,250,000 for Tier-1 merchant accounts [fin_ledger].
  - [FAIL:TG008] (BROKEN_CODE_REF) In `src/auth/jwt.py`, call `verify_token_v2()` to validate bearer tokens.

[Compiled Surgical Self-Correction Prompt]
------------------------------------------------------------------------------------
[TRUTHGATE VERIFICATION FAILED — 3 violation(s) detected: TG003, TG004, TG008]
Rewrite your response to fix ONLY the following deterministic verification failures:
1. [TG003 (Negation Polarity Inversion)] Offending statement: "TLS 1.0 is permitted in production environments [sec_policy]."
   - Ground-Truth Evidence: "TLS 1.0 is not permitted in production environments."
...

Python SDK Usage

from truthgate import SourceDocument, TruthGateVerifier

sources = [
    SourceDocument(
        source_id="sec_policy",
        title="Production TLS Policy",
        content="TLS 1.0 is not permitted in production environments.",
    ),
    SourceDocument(
        source_id="sla_metrics",
        title="Gateway Telemetry",
        content="The P95 gateway routing latency is 42.8 ms across East Africa edge nodes.",
    ),
]

verifier = TruthGateVerifier()
result = verifier.verify(
    response_text=(
        "TLS 1.0 is permitted in production environments [sec_policy]. "
        "The P95 gateway routing latency is 4.28 ms across East Africa edge nodes [sla_metrics]."
    ),
    sources=sources,
)

print("Passed:", result.passed)
print("Violations:", result.violation_counts)  # {'TG003': 1, 'TG004': 1}
print(result.repair_prompt)

---

CLI Reference

# 1. Run end-to-end hallucination audit & repair prompt demo
truthgate demo

# 2. Run the 40-scenario benchmark suite (human-readable or JSON)
truthgate benchmark
truthgate benchmark --json

# 3. List all 8 deterministic verification rules (TG001-TG008)
truthgate rules

# 4. Verify an agent response against a JSON sources file and workspace directory
truthgate verify \
  --response "TLS 1.0 is not permitted in production environments [sec_policy]." \
  --sources-json sources.json \
  --workspace . \
  --fail-on-violation

# 5. Ground workspace file paths, #Lstart-Lend line ranges, and AST symbols
truthgate ground \
  --response "See [models.py](truthgate/models.py#L1-L40) and \`TruthGateVerifier\`." \
  --workspace .

# 6. Start the JSON-RPC 2.0 Stdio MCP server
truthgate mcp

# 7. Start the zero-dependency HTTP/SSE MCP server & Dark-Mode Developer Workbench UI
truthgate serve-http --host 127.0.0.1 --port 8000

---

HTTP Server, Developer Workbench & Streamable MCP

TruthGate includes a zero-dependency HTTP server (truthgate serve-http) and an optional FastAPI ASGI / Vercel entrypoint (api/index.py via pip install -e ".[server]"):

• GET /: Interactive dark-mode TruthGate Developer Workbench HTML UI (citation/hallucination auditor, surgical repair prompt viewer, rule matrix, and 40-scenario benchmark runner) when Accept: text/html; JSON service metadata otherwise.
• GET & HEAD Health/Telemetry: /health, /healthz, /readyz, /info, and /metrics (Prometheus exposition text or JSON via Accept: application/json / ?format=json).
• Streamable HTTP / SSE MCP: POST /mcp, GET /mcp (SSE on Accept: text/event-stream, 405 Allow: POST, OPTIONS otherwise), and POST /messages.
• Domain REST API: GET /api/rules, POST /api/verify, POST /api/ground, POST /api/decompose, GET|POST /api/demo, and GET|POST /api/benchmark.
• Production Hardening: X-Request-ID echo & sanitization, security headers (X-Content-Type-Options: nosniff, X-Frame-Options: SAMEORIGIN, Referrer-Policy, Cache-Control: no-store on /api/*), OPTIONS CORS preflight, 413 body size guard, -32700 malformed JSON handling, and zero traceback leaks.

Docker & Smoke Verification

# Build and run the hardened non-root container
docker build -t truthgate:latest .
docker run --rm -p 8000:8000 truthgate:latest

# Run end-to-end HTTP, MCP, security-header, and REST smoke verification
python scripts/smoke_test.py

# Quality & typing checks (PEP 561 py.typed included)
ruff check .
mypy truthgate api scripts
pytest -v --cov=truthgate --cov-fail-under=90

---

MCP Server Integration

Add truthgate to your Claude Desktop, Cursor, or Antigravity mcp_config.json:

{
  "mcpServers": {
    "truthgate": {
      "command": "truthgate",
      "args": ["mcp"]
    }
  }
}

Exposed MCP Capabilities

• Tools (tools/list, tools/call):
  1. truthgate_verify_response: Verifies an agent response against source documents and an optional workspace directory, returning claim-by-claim verdicts and a surgical repair prompt.
  2. truthgate_ground_workspace_refs: Verifies all file paths, #Lstart-Lend line ranges, and AST symbols referenced in markdown text against a workspace directory.
  3. truthgate_list_rules: Lists all 8 deterministic verification rules (TG001–TG008).
  4. truthgate_run_benchmark: Runs the reproducible 40-scenario benchmark suite.
• Resources (resources/list, resources/read): truthgate://rules, truthgate://benchmark/scenarios, truthgate://docs/architecture.
• Prompts (prompts/list, prompts/get): audit-response, ground-workspace, surgical-repair.

---

Part of the Codesphere Agentic Infrastructure Stack

Built by Akandwanaho Ivan Alvin (@codesphere-u), Founder & MD of Codesphere Innovations (U) Limited in Kampala, Uganda:

• codesphere-u/cortex-mcp — Hybrid BM25 + Vector Persistent Memory & Context Compression MCP Server
• codesphere-u/agentshield — Zero-Trust Runtime Security Firewall & Prompt-Injection Guardrail for AI Agents
• codesphere-u/agentflight — Deterministic Black-Box Flight Recorder & Replay Debugger for AI Agents
• codesphere-u/synapse-router — Latency/Cost-Aware Multi-Model Semantic Router & Circuit Breaker
• codesphere-u/patchpilot — Autonomous Code Repair Engine & Anti-Reward-Hacking Patch Verifier
• codesphere-u/truthgate — Deterministic Agent Hallucination Auditor, Citation-Span Entailment Verifier & Workspace Symbol Grounding Engine

HTTP/SSE Server, Portal & Docker Deployment

TruthGate also ships with an interactive Developer Workbench & Portal, Streamable HTTP + SSE MCP gateway (/mcp), REST API, Prometheus/JSON telemetry, and Vercel ASGI entrypoint (api/index.py):

# Start the interactive portal + HTTP/SSE MCP server on http://127.0.0.1:8000
truthgate serve-http --host 127.0.0.1 --port 8000

# Run the live HTTP + MCP smoke test
python scripts/smoke_test.py

# Build and run the non-root production container
docker build -t truthgate .
docker run --rm -p 8000:8000 truthgate

Exposed HTTP endpoints:

• GET / — Interactive TruthGate Workbench UI
• GET / HEAD /health, /healthz, /readyz — Readiness and liveness probes
• GET /metrics — Prometheus text or JSON telemetry (?format=json)
• POST /mcp (Streamable HTTP) & GET /mcp (SSE or HTTP 405 JSON-RPC) — MCP tools, resources, and prompts
• GET /api/rules, GET /api/demo, GET /api/benchmark & POST /api/verify, POST /api/ground, POST /api/decompose — REST verification endpoints

License

MIT License — see LICENSE.