Reject unsupported subscription streams - #3073
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SamMorrowDrums merged 2 commits intoAug 17, 2026
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Use the Mcp-Method header to reject subscriptions/listen with the spec-defined 404 Method Not Found response instead of opening an idle SSE stream. Preserve SDK validation for missing or mismatched headers. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 06d5dda1-4086-4996-8d18-152e45e611b0
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Pull request overview
Rejects unsupported subscriptions/listen requests to prevent idle SSE streams.
Changes:
- Adds the Mcp-Method header constant.
- Returns HTTP 404 with JSON-RPC -32601.
- Tests matching, missing, and mismatched headers.
| File | Description |
|---|---|
| pkg/http/headers/headers.go | Defines the MCP method header. |
| pkg/http/handler.go | Rejects unsupported subscription streams. |
| pkg/http/handler_test.go | Verifies rejection and header validation. |
Review details
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- Files reviewed: 3/3 changed files
- Comments generated: 0
- Review effort level: Balanced
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Document why header validation precedes the unsupported-method rejection and use named SDK error constants in tests. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 06d5dda1-4086-4996-8d18-152e45e611b0
IrynaKulakova
approved these changes
Aug 17, 2026
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Summary
Reject subscriptions/listen requests instead of opening an idle SSE stream when the HTTP server cannot provide change notifications.
Why
The remote server exposes a static MCP catalog and does not emit change notifications. Under MCP 2026-07-28, accepting subscriptions/listen would leave clients on a stream that cannot deliver useful events.
N/A — no linked issue.
What changed
MCP impact
MCP transport behavior changes for subscriptions/listen; no tool schemas changed.
Prompts tested (tool changes only)
Security / limits
Tool renaming
Lint & tests
Docs