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MCP Hangar

The policy enforcement plane for MCP -- deterministic admission and egress policy, attributable audit, and SIEM export for your MCP server fleet. MIT, self-hosted, no SaaS.

PyPI CI License: MIT

Why

In MCP, the tool list is a hint the client caches; the call path is the only surface a provider mediates in real time. Every governance primitive worth having -- revocation, per-tenant scoping, audit -- attaches there, or attaches to nothing. Hangar puts a policy enforcement plane on that seam: one mediated path for lifecycle, policy, and telemetry across your whole MCP server fleet.

Background: The Advisory List -- Why MCP Governance Lives at the Call Path

Install

pip install mcp-hangar
# or: uv pip install mcp-hangar

Quickstart

Point Hangar at an MCP server in config.yaml:

mcp_servers:
  github:
    mode: subprocess
    command: [uvx, mcp-server-github]
    env:
      GITHUB_TOKEN: ${GITHUB_TOKEN}

Then serve it:

mcp-hangar serve --config config.yaml                     # stdio (Claude Desktop)
mcp-hangar serve --config config.yaml --http --port 8000  # HTTP + REST API at /api/

The 1.5 server refuses to bind a non-loopback interface without auth. For a quick/insecure demo, pass --unsafe-no-auth; for anything real, configure the auth block.

Or skip the config entirely -- get filesystem, fetch, and memory servers wired into Claude Desktop in one line:

curl -sSL https://mcp-hangar.io/install.sh | bash && mcp-hangar init -y && mcp-hangar serve

What you get

  • Parallel tool calls -- one hangar_call fans out to many MCP servers concurrently; all results returned together.
  • Lifecycle management -- lazy start, health checks, single-flight cold starts, idle shutdown, and per-server circuit breaking.
  • Hot config reload -- add or withdraw servers and tools via file watch, no restart.
  • Per-tenant tool projection -- front-door mode presents a different executable surface per caller, fail-closed on unknown identity.
  • OAuth ingress -- advertise as an RFC 9728 protected resource and challenge external agents for verified tokens.
  • Auth & RBAC -- API-key and OIDC/JWT identity with role-based access; bootstrap the first administrator with mcp-hangar auth bootstrap-admin, and every call carries a verified principal into the audit trail.
  • Observability built in -- OpenTelemetry traces, Prometheus metrics, structured logs, and an event-sourced audit trail.

Configuring tools:

The per-server tools: key is overloaded and accepts two distinct forms:

  • A list of tool schemas is a pre-start visibility projection. It lets a tool be listed before its provider has started, so callers can see it up front. It is not an access policy. On start, the provider's dynamic tools/list is authoritative and replaces this projection entirely — a statically-listed tool that the provider does not return becomes uncallable and fails with Tool not found: <name> at invocation (a warning naming the unconfirmed tool is logged at start).

  • A dict with allow: / deny: is an access policy (glob-pattern, three-level merge) that filters which discovered tools are exposed.

mcp_servers:
  math:
    mode: subprocess
    command: [python, -m, examples.provider_math.server]
    tools:                     # list form: pre-start schema projection
      - name: add
        description: "Add two numbers"
        inputSchema: { type: object, properties: { a: { type: number } } }
  github:
    mode: subprocess
    command: [uvx, mcp-server-github]
    tools:                     # dict form: allow/deny access policy
      allow: [create_issue, list_issues]
      deny: [delete_repository]

Documentation

License

MIT

Project links

Data verified by PyPI on Jul 28, 2026
Data provided by the project maintainers, verified at the time the release was uploaded to PyPI.

Key dates

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  • Released:
Newer release available (2.17.0)

1 maintainer

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Avatar for mapyr from gravatar.com mapyr

Credits

Author: Marcin Pyrka

GitHub Statistics

Data verified by PyPI on Jul 28, 2026
The GitHub source repository was provided by the project maintainers and verified by PyPI at the time of upload. Stars, forks, and open issues/PRs are derived from that repository and have not been independently verified.

License

MIT License (MIT)

Requires

Python >=3.11

Provides Extra

containers dev full langfuse opentelemetry postgres

Tags

ai infrastructure llm mcp model-context-protocol

Classifiers

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