fix: show error toast when streamable-http MCP connection fails (fixes #2823)#2829
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giulio-leone wants to merge 1 commit intoChainlit:mainfrom
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fix: show error toast when streamable-http MCP connection fails (fixes #2823)#2829giulio-leone wants to merge 1 commit intoChainlit:mainfrom
giulio-leone wants to merge 1 commit intoChainlit:mainfrom
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When connecting to a streamable-http MCP server that is unreachable, the frontend showed a green 'MCP added!' success toast instead of an error message because the HTTP error was not thrown (fixes Chainlit#2823). Throw ClientError on non-ok response. Check res.ok before attempting JSON parse so proxy HTML error pages don't cause a SyntaxError. Use data.detail as the message so the toast shows the actual error reason (e.g. 'Connection refused') rather than generic status text.
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Summary
Fixes #2823 — Frontend shows "MCP added!" success toast when a streamable-http MCP connection fails with HTTP 400, while SSE correctly shows an error toast.
Root Cause
However, the frontend's
ExtendedChainlitAPI.connectStreamableHttpMCP()overrides the base method with a rawfetch()that does not throw on non-OK responses — it returns{ success: res.ok, ... }. The promise always resolves, sotoast.promise()always shows the success toast.Fix
Result
Summary by cubic
Show an error toast when a streamable-http MCP connection fails. We now throw a
ClientErroron non-OK responses, usedetailwhen present, and skip JSON parsing for HTML errors sotoast.promiseshows the real message (fixes #2823).Written for commit 3f15d96. Summary will update on new commits.