René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Intermittent HTTP 500 from remote MCP endpoint: \"can't get copilot user by id\" twirp permission_denied","articleBody":"### Description\n\nSince approximately May 18, 2026 (coinciding with v1.0.5 release), the remote MCP endpoint at `https://api.githubcopilot.com/mcp/` intermittently returns HTTP 500 with a raw text/plain error body. The failure rate is approximately **7–10%** and affects write operations like `create_branch`. Read-only operations (`search_repositories`, `get_file_contents`) appear unaffected.\n\n### Error Response\n\n**HTTP Status:** `500 Internal Server Error`  \n**Content-Type:** `text/plain; charset=utf-8` (not a valid JSON-RPC or SSE response)\n\n```\ncan't get copilot user by id: error getting copilot user details: twirp error permission_denied: Error from intermediary with HTTP status code 403 \"Forbidden\"\n```\n\n### Full Request/Response Context\n\n**Request:**\n```http\nPOST https://api.githubcopilot.com/mcp/\nAuthorization: Bearer \u003cvalid-PAT-with-repo-scope\u003e\nContent-Type: application/json\nAccept: application/json, text/event-stream\nMcp-Session-Id: \u003cvalid-session-id\u003e\n```\n\n```json\n{\n  \"jsonrpc\": \"2.0\",\n  \"method\": \"tools/call\",\n  \"id\": 9,\n  \"params\": {\n    \"name\": \"create_branch\",\n    \"arguments\": {\n      \"owner\": \"\u003corg\u003e\",\n      \"repo\": \"\u003cprivate-repo\u003e\",\n      \"branch\": \"test-branch-name\",\n      \"from_branch\": \"main\"\n    }\n  }\n}\n```\n\n**Response Headers:**\n```\nHTTP/2 500\ncontent-type: text/plain; charset=utf-8\nx-github-backend: Kubernetes\nx-github-request-id: D44E:1D706B:5F7B92F:675BE79:6A0C6556\n```\n\n### Reproduction\n\n- **Frequency:** ~7–10% of `create_branch` calls (1 in 9 to 1 in 15 attempts)\n- **Pattern:** Random, not correlated with request timing or concurrency\n- **Session state:** Occurs on freshly initialized sessions (not stale session issue)\n- **Authentication:** PAT is valid (other calls in the same session succeed; `initialize` and `tools/list` always return 200)\n\nMinimal reproduction: send 15–30 consecutive `create_branch` tool calls (each with a new session). Typically 1–3 will return HTTP 500.\n\n### Analysis\n\nThe error chain suggests the failure occurs in the **Copilot hosting infrastructure** (not in the open-source MCP server logic):\n\n1. Request passes HTTP gateway authentication (PAT is valid → not 401)\n2. Hosting layer attempts internal twirp RPC: `getCopilotUserById`\n3. An internal service mesh intermediary returns **403 Forbidden** to the twirp call\n4. This unhandled error propagates as a raw HTTP 500 to the client\n\nThe 403 from the \"intermediary\" indicates a **service-to-service authentication failure** (likely mTLS cert rotation, internal token expiry, or inconsistent sidecar state during deployment), not a user-permission issue.\n\n### Impact\n\n- MCP clients using `streamablehttp_client` have their entire transport killed by this error (the SDK's `post_writer` TaskGroup crashes, closing read/write streams)\n- Simple in-session retries are ineffective because the session is dead after the 500\n- Automated workloads (CI/CD, evaluation pipelines) see cascading failures\n\n### Expected Behavior\n\n- HTTP 500 should not leak internal error details to clients\n- The `getCopilotUserById` lookup should have retry/circuit-breaker logic on the server side\n- Alternatively, the error should be wrapped in a proper JSON-RPC error response so MCP clients can handle it gracefully\n\n### Environment\n\n- MCP Protocol Version: `2024-11-05`\n- Transport: Streamable HTTP (POST)\n- Client: Python MCP SDK (`mcp` package)\n- Authentication: GitHub PAT (repo + read:org scopes)\n- GitHub MCP Server version: v1.0.5 (remote, hosted)\n\n### Related\n\n- microsoft/vscode-copilot-release#990 (same error pattern, reported March 2024)\n- PR #2478 (IFC marker change merged May 14, 2026 — temporal correlation with onset)","author":{"url":"https://github.com/KentWangYQ","@type":"Person","name":"KentWangYQ"},"datePublished":"2026-05-19T14:12:33.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/2508/github-mcp-server/issues/2508"}