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connect at cursor erro #1273
Description
Describe the bug
connect at cursor error
{
"mcpServers": {
"demo-streamable": {
"url": "http://xxxx:6559/mcp",
"enabled": true
}
}
}
To Reproduce
Steps to reproduce the behavior:
- open cursor
- ~/.cursor/mcp.json
- {
"mcpServers": {
"demo-streamable": {
"url": "http://xxxx:6559/mcp",
"enabled": true
}
}
}
Expected behavior
A clear and concise description of what you expected to happen.
Logs
2025-12-09 15:10:34.542 [info] Handling DeleteClient action
2025-12-09 15:10:36.408 [info] Handling CreateClient action
2025-12-09 15:10:36.408 [info] Creating streamableHttp transport
2025-12-09 15:10:36.408 [info] Connecting to streamableHttp server
2025-12-09 15:10:36.422 [info] Handling ListOfferings action, server stored: false
2025-12-09 15:10:36.422 [error] No server info found
2025-12-09 15:10:36.422 [info] No stored tokens found
2025-12-09 15:10:36.431 [info] Client closed for command
2025-12-09 15:10:36.431 [error] Error connecting to streamableHttp server, falling back to SSE: [
{
"code": "invalid_type",
"expected": "string",
"received": "array",
"path": [
"serverInfo",
"icons",
0,
"sizes"
],
"message": "Expected string, received array"
}
]
2025-12-09 15:10:36.431 [error] Error connecting to streamableHttp server, falling back to SSE: [
{
"code": "invalid_type",
"expected": "string",
"received": "array",
"path": [
"serverInfo",
"icons",
0,
"sizes"
],
"message": "Expected string, received array"
}
]
2025-12-09 15:10:36.431 [info] Connecting to SSE server
2025-12-09 15:10:36.432 [info] SSE stream disconnected, transport will reconnect automatically SSE stream disconnected: AbortError: This operation was aborted
2025-12-09 15:10:36.443 [info] Handling ListOfferings action, server stored: false
2025-12-09 15:10:36.443 [error] No server info found
2025-12-09 15:10:36.443 [info] No stored tokens found
2025-12-09 15:10:36.446 [error] Client error for command SSE error: Non-200 status code (400)
2025-12-09 15:10:36.446 [error] Error connecting to SSE server after fallback: SSE error: Non-200 status code (400)
2025-12-09 15:10:36.446 [info] Client closed for command
2025-12-09 15:10:36.467 [info] Handling ListOfferings action, server stored: false
2025-12-09 15:10:36.467 [error] No server info found
Additional context
Add any other context about the problem here.
Activity
githubsyf3527 commentedon Dec 9, 2025
src/examples/server/simpleStreamableHttp.ts
index ca13631..58ea0c1 100644
--- a/src/examples/server/simpleStreamableHttp.ts
+++ b/src/examples/server/simpleStreamableHttp.ts
@@ -34,7 +34,8 @@ const getServer = () => {
{
name: 'simple-streamable-http-server',
version: '1.0.0',
felixweinberger commentedon Dec 16, 2025
Thanks for the report! The
sizesfield was changed fromstringtostring[]in #981 - this was a fix to ensure the SDK stays as close to the spec as possible before the 2025-11-05 release. Some clients had built against the earlier format before the spec was finalized.Figma's MCP client ran into the same issue and updated their implementation. Since the SDK needs to stay spec-compliant, Cursor will need to make a similar update. You might want to file an issue with their team.