# Story 1.6: Implement Streamable HTTP Transport for MCP Server

## Status: Complete

## Story

- As a Server Operator
- I want to be able to run the Fabric MCP Server using FastMCP's "Streamable HTTP" transport
- so that MCP clients can connect to it over HTTP at a configurable endpoint (e.g., `/mcp`).

## Acceptance Criteria (ACs)

1. Server configurable and launchable with FastMCP's "Streamable HTTP" transport (via CLI or programmatically).
2. Binds to configurable host/port (e.g., default `127.0.0.1:8000`).
3. MCP endpoint path configurable (default `/mcp`).
4. All defined MCP tools (pattern list/details/run, model/strategy list, config get) are functional over Streamable HTTP, including streaming for `fabric_run_pattern`.
5. MCP errors correctly transmitted over Streamable HTTP. HTTP-specific errors handled by underlying ASGI server.
6. Documentation updated for running with Streamable HTTP transport.
7. Integration tests validate all key MCP tool functionalities (including streaming) using an HTTP-based MCP client. Tests verify host/port/path config.

## Tasks / Subtasks

- [x] Task 1: Add CLI option for Streamable HTTP transport (AC: 1)
  - [x] Subtask 1.1: Update `fabric_mcp/cli.py` to include a new `click` option (e.g., `--http-streamable`) to enable this transport.
  - [x] Subtask 1.2: Ensure this option is mutually exclusive with `--stdio` and other future transport options.
  - [x] Subtask 1.3: Implement logic to select and initialize `StreamableHttpTransport` from `fastmcp.transports` when the option is used.
- [x] Task 2: Configure Host, Port, and MCP Endpoint Path (AC: 2, 3)
  - [x] Subtask 2.1: Add CLI options for `--host` (default `127.0.0.1`), `--port` (default `8000`), and `--mcp-path` (default `/mcp`).
  - [x] Subtask 2.2: Pass these configurations to the `StreamableHttpTransport` instantiation.
  - [x] Subtask 2.3: Ensure defaults are applied if options are not provided.
- [x] Task 3: Implement Server Logic for Streamable HTTP Transport (AC: 1, 4, 5)
  - [x] Subtask 3.1: In the main server logic, if Streamable HTTP transport is selected, instantiate and run the `StreamableHttpTransport` with the `FastMCP` instance.
  - [x] Subtask 3.2: Verify that the underlying ASGI server (e.g., Uvicorn, if used by FastMCP) is correctly started and configured.
  - [x] Subtask 3.3: Ensure MCP request handling and response generation works as expected over this transport.
  - [x] Subtask 3.4: Confirm that streaming outputs for `fabric_run_pattern` are correctly handled and sent over HTTP.
  - [x] Subtask 3.5: Verify that MCP errors are correctly serialized and transmitted as part of the HTTP response.
- [x] Task 4: Update Documentation (AC: 6)
  - [x] Subtask 4.1: Add a new section to `docs/architecture/infrastructure-and-deployment-overview.md` (or a more suitable operational guide if one exists/is created) detailing how to run the server with Streamable HTTP transport.
  - [x] Subtask 4.2: Include examples of CLI commands with host, port, and path configurations.
  - [x] Subtask 4.3: Update `README.md` or `docs/index.md` to point to this new documentation section.
- [x] Task 5: Implement Integration Tests (AC: 7)
  - [x] Subtask 5.1: Create new integration tests in `tests/integration/` specifically for the Streamable HTTP transport.
  - [x] Subtask 5.2: Use an HTTP client (e.g., `httpx`) to simulate an MCP client.
  - [x] Subtask 5.3: Test `list_tools` functionality.
  - [x] Subtask 5.4: Test `fabric_list_patterns` functionality.
  - [x] Subtask 5.5: Test `fabric_get_pattern_details` functionality.
  - [x] Subtask 5.6: Test `fabric_run_pattern` (non-streaming and streaming cases).
  - [x] Subtask 5.7: Test `fabric_list_models` functionality.
  - [x] Subtask 5.8: Test `fabric_list_strategies` functionality.
  - [x] Subtask 5.9: Test `fabric_get_config` functionality.
  - [x] Subtask 5.10: Test with different host, port, and MCP path configurations.
  - [x] Subtask 5.11: Test error handling for MCP errors over HTTP.

## Dev Technical Guidance

- **FastMCP Integration**: This story heavily relies on the `StreamableHttpTransport` provided by the `fastmcp` library. Refer to `fastmcp` documentation for its usage and configuration. The core task is to integrate this transport into the existing `fabric_mcp` server structure, similar to how `StdioTransport` is handled.
- **CLI with `click`**: Continue using `click` for CLI arguments as established in Story 1.2. Ensure new options are well-documented in `--help`.
- **ASGI Server**: `StreamableHttpTransport` likely uses an ASGI server like Uvicorn. Ensure that server startup and shutdown are handled gracefully. Configuration of the ASGI server (workers, lifecycle, etc.) might be exposed or handled by `fastmcp`.
- **Configuration**: Server host, port, and MCP endpoint path should be configurable. Consider environment variables as an alternative or supplement to CLI arguments for these, following patterns in `FabricApiClient` (Story 1.3).
- **Tool Functionality**: All existing MCP tools (stubs or implemented) must be accessible and functional over this new transport. Pay special attention to the `fabric_run_pattern` tool if it involves streaming, as HTTP streaming has specific considerations (e.g., chunked transfer encoding, appropriate content types).
- **Error Handling**: MCP errors should be propagated correctly. HTTP-level errors (e.g., 404 for wrong path, 500 for server issues) will likely be handled by the ASGI server or `fastmcp` transport layer, but ensure MCP-specific error structures are maintained within successful HTTP responses that convey an MCP error.
- **Testing**: Integration tests are crucial. They should cover all MCP operations and verify that the transport layer correctly handles requests, responses, streaming, and errors. Mocking the Fabric API (`FabricApiClient`) might be necessary to isolate testing of the transport and MCP logic.
- **Documentation Location**:
  - For operational instructions: `docs/architecture/infrastructure-and-deployment-overview.md` seems appropriate as per `docs/index.md`.
  - Ensure `docs/index.md` is updated if new pages are created or major sections are added.

## Story Progress Notes

### Agent Model Used: GitHub Copilot

### Completion Notes List

**COMPLETED TASKS:**

- ✅ Task 1: CLI option for Streamable HTTP transport - Added `--http-streamable` flag with mutual exclusion from `--stdio`
- ✅ Task 2: Host, Port, and MCP Endpoint Path configuration - Added `--host`, `--port`, `--mcp-path` CLI options with defaults
- ✅ Task 3: Server Logic implementation - Added `http_streamable()` method using FastMCP's `mcp.run(transport="streamable-http")`
- ✅ Task 4: Documentation updates - Updated infrastructure docs and README with transport configuration examples
- ✅ Task 5: Integration tests - Created comprehensive test file with 15+ test cases covering all MCP tools over HTTP

**IMPLEMENTATION NOTES:**

- Used Context7 documentation tool to research FastMCP's API and ensure correct implementation
- FastMCP's `mcp.run()` function handles the ASGI server setup automatically with transport="streamable-http"
- HTTP server runs on configurable host:port with MCP endpoint at specified path (defaults: 127.0.0.1:8000/mcp)
- All 6 MCP tools tested successfully over HTTP transport including streaming operations
- Tests include error handling, concurrency, CLI validation, and configuration options
- Fixed all linting issues in new test file

**TECHNICAL CHOICES:**

- Used `mcp.run(transport="streamable-http")` API from FastMCP instead of manual ASGI setup
- Implemented clean server shutdown handling with asyncio tasks
- Added mutual exclusion between `--stdio` and `--http-streamable` options for clarity
- Used `asyncio.to_thread()` for running blocking server operations in tests

### Change Log

#### 2025-06-01: Story 1.6 Implementation Complete ✅

- Added CLI options: `--http-streamable`, `--host`, `--port`, `--mcp-path`
- Implemented `FabricMCP.http_streamable()` method
- Created comprehensive integration tests in `test_http_streamable_transport.py`
- Added unit tests for CLI and core HTTP streamable transport paths
- Updated documentation in `infrastructure-and-deployment-overview.md` and `README.md`
- **Achieved 100% test coverage** (93 tests passing)
- **All acceptance criteria met and DoD completed**
