Repro Capsule MCP

Turn a bug report into a portable, reviewable reproduction capsule without silently copying a repository or executing model-generated shell text. Every report, command plan, transcript, artifact, and export stays evidence-linked and redacted.

flowchart LR
    A[Bug report] --> B[Dynamic project profile]
    B --> C[Evidence-based hypotheses]
    B --> D[Reviewed command plan]
    D --> E[One-time approval]
    E --> F[Bounded execution]
    C --> G[Portable capsule]
    F --> G

Highlights

• Dynamic command discovery from current project manifests
• Secret-redacted reports, text artifacts, stdout, and stderr
• Binary artifacts represented by metadata and hashes instead of unreviewed content
• Direct argv execution without a shell
• One-time plan tokens with separate workspace-write and network approvals
• Process-group timeout cleanup and bounded output capture
• Run-to-run transcript comparison without guessing whether a fix is correct
• ZIP export containing a versioned manifest and reproduction guide
• Stdio and Streamable HTTP transports

Install

uv tool install "git+https://github.com/efficjump/repro-capsule-mcp.git"
repro-capsule-mcp --transport stdio

For source development:

git clone https://github.com/efficjump/repro-capsule-mcp.git
cd repro-capsule-mcp
uv sync --all-extras --locked
uv run repro-capsule-mcp --transport stdio

Generic MCP client configuration

{
  "mcpServers": {
    "repro-capsule": {
      "command": "repro-capsule-mcp",
      "args": ["--transport", "stdio"]
    }
  }
}

The installed command avoids embedding any local checkout path in client configuration.

Tool workflow

Tool	Purpose
start_case	Create a bounded case with a redacted bug report
list_cases / get_case	Browse persisted case state and evidence
inspect_project	Discover manifests, environment names, Git state, and commands
analyze_case	Produce host-model hypotheses from current evidence
add_artifact	Add reviewed text or hash-only binary evidence
plan_command	Prepare an exact non-shell command and one-time token
execute_plan	Run one approved plan with bounds and redaction
compare_runs	Compare two execution transcripts
export_capsule	Create a portable ZIP and manifest

Safety model

• Project roots must remain inside REPRO_CAPSULE_ALLOWED_ROOTS.
• Sensitive filenames, symlinks, oversized files, and unreviewed binary content are excluded.
• Commands not discovered from current project files are denied by default.
• Network intent and workspace-write intent require separate approval.
• Environment values and approval tokens are not written into capsule exports.
• Every process uses a timeout, bounded output, and redaction before persistence.

This server is not an operating-system sandbox. Inspect and execute untrusted projects only in an isolated container or virtual machine.

Streamable HTTP

repro-capsule-mcp --transport streamable-http --host 127.0.0.1 --port 8766

The default endpoint is http://127.0.0.1:8766/mcp.

Development

uv sync --all-extras --locked
uv run ruff format --check .
uv run ruff check .
uv run mypy src
uv run pytest --cov --cov-report=term-missing
uv build

See architecture, security policy, and contribution guide.

License

MIT