## Stack Context
PR 6 of 6 in a stack that migrates every Coder MCP surface from the
archived `github.com/mark3labs/mcp-go` library to the official
`github.com/modelcontextprotocol/go-sdk` v1.7.0.
Stack: #28056 -> #28057 -> #28058 -> #28059 -> #28060 -> #28061
## Why
With every production surface migrated, this PR removes the mark3labs
dependency entirely and converts the remaining test fixtures.
- Migrates the remaining mark3labs test fixtures (coderd MCP e2e tests,
chatd fixtures, mcpclient fixtures, and the Force On MCP policy tests)
to official stateless SDK servers.
- Removes `github.com/mark3labs/mcp-go` from `go.mod` and drops the
corresponding dependabot ignore entry. Zero references remain repo-wide.
- Updates the MCP docs for the 2026-07-28 protocol: stateless Streamable
HTTP behavior, the supported 2024-11-05 through 2026-07-28 protocol
range, and explicit non-features (resources, prompts, structured output,
elicitation, MCP Tasks).
- The e2e ping assertion is removed because MCP 2026-07-28 removed the
ping method.
> Mux created this PR on Mike's behalf.
## Stack Context
PR 1 of 6 in a stack that migrates every Coder MCP surface from the
archived `github.com/mark3labs/mcp-go` library to the official
`github.com/modelcontextprotocol/go-sdk` v1.7.0, adding MCP 2026-07-28
support while keeping compatibility with clients speaking 2024-11-05
through 2025-06-18.
Stack: #28056 -> #28057 -> #28058 -> #28059 -> #28060 -> #28061
## Why
The coderd Streamable HTTP MCP server (`/api/experimental/mcp/http`) is
the foundation layer: it introduces the official SDK dependency and the
shared `RegisterSDKTool` helper the CLI server reuses.
- The server runs the SDK handler in stateless mode with `JSONResponse:
true`, preserving the previous `application/json` POST wire format. GET
and DELETE return 405, and no `Mcp-Session-Id` is issued, both permitted
by the Streamable HTTP spec.
- `DisableLocalhostProtection` is set because coderd commonly listens on
loopback behind a reverse proxy with a public Host header; the
endpoint's bearer authentication is the relevant access control.
- Tool registration builds raw JSON object schemas and omits empty
`required`, keeping `tools/list` output byte-identical to the previous
server (verified with a golden comparison).
- SDK logs are adapted to `cdr.dev/slog/v3`; only warnings and errors
are forwarded because the SDK logs several INFO lines per stateless
request.
- Tests cover the modern 2026-07-28 flow, legacy 2025-06-18 initialize,
unsupported protocol version rejection (`-32022`), and non-POST method
behavior.
## Known behavior deltas vs the old endpoint
Both deltas come from the SDK enforcing the Streamable HTTP spec where
mark3labs was lenient, on an experimental endpoint:
- POST requests whose `Accept` header lists `application/json` without
`text/event-stream` are now rejected with 400 (the spec requires clients
to list both; a missing `Accept` header is still tolerated). mark3labs
did not validate `Accept` at all.
- The old server generated an unvalidated `Mcp-Session-Id` response
header; the stateless SDK handler issues none. Clients that merely echo
the header back are unaffected.
## Validation
Beyond unit/integration tests, a remote dogfood UAT ran protocol
conformance against a live dev server built from the stack tip: version
negotiation matrix (2024-11-05 through bogus/omitted values), auth,
session/method semantics, tool schema sanity, tools/call happy and error
paths (unknown tool, schema-violating args, malformed JSON, jsonrpc
"1.0"), and a concurrency smoke test. No 500s or connection drops; error
shapes are clean JSON-RPC/HTTP errors.
> Mux created this PR on Mike's behalf.
Refactors `codersdk.Client`'s use of session tokens to use a `SessionTokenProvider`, which abstracts the obtaining and storing of the session token.
The main motiviation is to unify Agent authentication an an upstack PR, which can use cloud instance identity via token exchange, rather than a fixed session token.
However, the abstraction could also allow functionality like obtaining the session token from other external sources like the OS credential manager, or an external secret/key management system like Vault.
# Add MCP HTTP server with streamable transport support
- Add MCP HTTP server with streamable transport support
- Integrate with existing toolsdk for Coder workspace operations
- Add comprehensive E2E tests with OAuth2 bearer token support
- Register MCP endpoint at /api/experimental/mcp/http with authentication
- Support RFC 6750 Bearer token authentication for MCP clients
Change-Id: Ib9024569ae452729908797c42155006aa04330af
Signed-off-by: Thomas Kosiewski <tk@coder.com>
Michael Suchacz