## Description
`headroom mcp serve` only exposed stdio, which blocked MCP clients that
require a Streamable HTTP endpoint. This PR adds an explicit HTTP
transport mode around the existing Headroom MCP server while keeping
stdio as the default and keeping tool registration single-sourced.
Closes#1346.
## Type of Change
- [ ] Bug fix (non-breaking change that fixes an issue)
- [x] New feature (non-breaking change that adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [x] Documentation update
- [ ] Performance improvement
- [ ] Code refactoring (no functional changes)
## Changes Made
- Add `headroom mcp serve --transport http` with host, port, and path
options.
- Serve `headroom_compress`, `headroom_retrieve`, and `headroom_stats`
through the same MCP server instance used by stdio.
- Keep `headroom mcp serve` defaulting to stdio for current Claude Code
and local MCP host configs.
- Update MCP docs for stdio and HTTP setup without implying the proxy
automatically owns `/mcp`.
- Keep the scope clean, rebased, and covered by focused tests.
## Testing
- [x] Unit tests pass (`uv run pytest tests/test_ccr_mcp_http.py
tests/test_cli/test_mcp.py -q`)
- [x] Linting passes (`uv run ruff check headroom/cli/mcp.py
headroom/ccr/mcp_server.py headroom/ccr/mcp_http.py
tests/test_ccr_mcp_http.py tests/test_cli/test_mcp.py`)
- [x] Type checking passes (`uv run mypy headroom
--ignore-missing-imports`)
- [x] New tests added for new functionality when applicable
- [x] Manual testing performed
### Test Output
```text
uv run pytest tests/test_ccr_mcp_http.py tests/test_cli/test_mcp.py -q
20 passed in 0.53s
uv run ruff check headroom/cli/mcp.py headroom/ccr/mcp_server.py headroom/ccr/mcp_http.py tests/test_ccr_mcp_http.py tests/test_cli/test_mcp.py
All checks passed!
uv run ruff format headroom/cli/mcp.py headroom/ccr/mcp_server.py headroom/ccr/mcp_http.py tests/test_ccr_mcp_http.py tests/test_cli/test_mcp.py --check
5 files already formatted
uv run mypy headroom --ignore-missing-imports
Success: no issues found in 407 source files
```
## Real Behavior Proof
- Environment: Local Python environment with Headroom dev dependencies
and MCP extra installed.
- Exact command / steps: Start `headroom mcp serve --transport http
--host 127.0.0.1 --port <test-port> --path /mcp`, then perform an MCP
SDK Streamable HTTP initialize/list-tools exchange.
- Observed result: The HTTP transport initializes and lists the existing
Headroom MCP tools; `headroom mcp serve` without `--transport` still
selects stdio, and mixed-case `--transport HTTP` routes to the HTTP
transport.
- Not tested: live validation against external MCP hosts
## Review Readiness
- [x] I have performed a self-review
- [x] This PR is ready for human review
## Additional Notes
`CHANGELOG.md` is not edited because this repository generates changelog
entries from conventional commits. Full-suite validation is left to CI.
