Securedact MCP

Securedact MCP is an Apache-2.0 local MCP server and reusable Python privacy engine. It detects sensitive text, applies versioned policies, redacts locally, and validates residual output before marking sanitized content approved.

MCP mode does not automatically intercept every prompt. The host must invoke the tool and send only sanitized_text when status == "ok"; a misconfigured or malicious MCP host can bypass that ordinary MCP workflow. Provider-native enforced hooks are separate integration assets: when a supported provider invokes such a hook at its prompt lifecycle boundary, it can apply the same deterministic decision before normal model processing. See SecuRedact Enforced.

Safe default workflow

Use prepare_for_external_ai for normal external-AI preparation:

{
  "text": "Contact alex@example.test",
  "policy": "strict_external_ai",
  "language": "auto",
  "response_mode": "minimal"
}

Approved response:

{
  "schema_version": "1",
  "status": "ok",
  "sanitized_text": "Contact [EMAIL_1]",
  "counts": {"email": 1},
  "policy": "strict_external_ai",
  "policy_version": 1,
  "policy_digest": "...",
  "reason_codes": []
}

review_required and blocked responses never contain approved sanitized_text. Minimal responses contain no original text, raw entity values, mapping, exception body, stack trace, model path, or restoration handle unless restore_capable was explicitly selected.

Architecture and trust boundary

flowchart LR
    H["MCP host"] --> M["Securedact MCP"]
    M --> D["deterministic detectors"]
    M --> C["contextual detectors"]
    D --> P["policy engine"]
    C --> P
    P --> R["redactor"]
    R --> V["residual validator"]
    V --> O["approved sanitized output"]
    O --> W["host-controlled downstream workflow"]
    H -. "host may bypass MCP" .-> W

The server has no provider clients, OpenAI-compatible proxy, reverse proxy, website, desktop chatbot, provider credentials, or provider-specific forwarding. See ADR 0001 and the threat model.

Tools

Response modes are minimal, review, debug, and restore_capable. Debug is disabled unless the process was started with SECUREDACT_ENABLE_DEBUG_RESPONSES=1; an MCP request cannot enable it. In-memory restoration sessions use cryptographic random handles, bounded capacity, expiration, concurrency protection, and single-use consumption. Process exit destroys all sessions.

See MCP tools, response privacy, and restoration sessions.

Installation

Python >=3.12,<3.13 is supported.

The first public PyPI release is not yet available. Until publication is confirmed, install from a reviewed source checkout:

git clone https://github.com/GigantesHJI/securedact-mcp.git
cd securedact-mcp
python -m pip install ".[ml]"
securedact-mcp install
securedact-mcp models verify
securedact-mcp

After the package is published and independently verified on PyPI, the primary installation command will be python -m pip install "securedact-mcp[ml]".

The last command starts a local stdio server. Standard output is reserved for MCP protocol messages. Model installation is explicit and consent-based; no model checkpoint is included in the repository or wheel, and startup never downloads one. Securedact does not redistribute these model weights. Upstream model weights retain their own licenses and are not relicensed by Apache-2.0. See model installation and third-party licenses.

Deterministic-only local development must be explicitly selected:

$env:SECUREDACT_REQUIRE_FLAIR = "0"
securedact-mcp

Production defaults to requiring contextual capability and fails closed while a configured model is missing, loading, corrupt, or unavailable.

Host packages

Tested configuration assets and safe-workflow instructions are under integrations/ for Codex, Cursor, and Windsurf. The automated MCP client harness validates server startup, tool listing, calls, minimal response shape, stdout integrity, and shutdown. It does not prove that a real host invokes the tool for every prompt. See the compatibility evidence.

Policies and Python API

Built-ins include default, strict_external_ai, gdpr, identifiers_only, and review_all_contextual; compatibility policies remain available. Local organization policy files load only from the controlled policy directory, use a strict declarative schema, and cannot disable fail-closed invariants. Unknown, duplicate, oversized, malformed, or symlinked policies fail closed.

from securedact_core import RedactionRequest, SecuredactEngine

engine = SecuredactEngine.from_environment()
result = engine.prepare(
    RedactionRequest(
        text="Contact alex@example.test",
        policy="strict_external_ai",
    )
)

from_environment() preserves the contextual-model requirement. Standalone deterministic development requires SECUREDACT_REQUIRE_FLAIR=0; applications may also inject tested detector implementations. See public API and policies.

Reproducible development

The committed uv.lock resolves runtime, ML, development, benchmark, and security extras for Python 3.12.

uv sync --frozen --extra dev --extra benchmark
uv run python scripts\verify.py

Never use real personal information, private documents, credentials, customer logs, or model weights in tests, issues, screenshots, fixtures, or pull requests. See CONTRIBUTING.md.

Evaluation and performance

uv run python -m securedact_eval quality --mode deterministic --gate `
  --thresholds benchmarks\thresholds.json `
  --baseline benchmarks\baselines\quality-deterministic.json
uv run python -m securedact_eval performance --mode deterministic

The versioned synthetic corpus reports exact and relaxed span precision, recall, F1, false-positive and false-negative rates, per-entity/language/domain/split results, action/category accuracy, and bootstrap recall intervals. True negatives are document-level negative examples, not token-level safety. The GDPR-related suite is detection evaluation, not legal compliance certification. Real Flair and GPU benchmarks require an explicitly configured local model and are not ordinary CI. See benchmarking. The benchmark framework documents local data tiers and large profiles; the migration plan defines its future extraction boundary. For a failure before GitHub executes repository steps, use the CI troubleshooting decision tree. Local success does not replace a required GitHub check.

Security and limitations

• No prompt, finding, mapping, restoration handle, secret, model input, or restored output is logged by application code.
• Deterministic and contextual detection can miss novel, ambiguous, or adversarial disclosure; coreference and universal obfuscation resistance are not claimed.
• Review offsets let a trusted local client with the original input reconstruct a value; keep review responses local.
• Host behavior and downstream provider behavior are outside the trust boundary.
• Repository security settings documented in files still require administrator verification.

Report vulnerabilities privately using SECURITY.md. Do not put vulnerability details or real data in a public issue.

License

Original repository source and documentation are licensed under the Apache License 2.0. Copyright attribution is recorded in NOTICE. Third-party dependencies and model weights retain their own licenses.