fix: MCP call_tool fails for streamable-http and SSE transports#550
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DoganK01 merged 2 commits intoUpsonic:masterfrom Mar 17, 2026
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call_tool treated the streamable-http context as a ready-made session, but it's actually a (read, write, session_id) tuple — same as stdio. This caused "unhandled errors in a TaskGroup" on every tool call. Also fix AnyUrl not being JSON serializable in _process_tool_result when handling EmbeddedResource responses. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Hey works fine! Thanks for the contribution |
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Summary
call_tooltreated the streamable-http/SSE client context as a session object, but it returns a(read, write, session_id)tuple — same as stdio. This causedTypeError: 'tuple' object does not support the asynchronous context manager protocol, surfaced as "unhandled errors in a TaskGroup" on every tool call._process_tool_resultfailed withTypeError: Object of type AnyUrl is not JSON serializablewhen handlingEmbeddedResourceresponses — fixed by castinguritostr().Note: the
connectmethod already handles the tuple correctly (line 483). This bringscall_toolin line with that pattern.Test plan
MCPHandler.call_tool()works with streamable-http transport against GitHub's MCP serverEmbeddedResourceresponses (e.g.get_file_contents) are processed without serialization errors🤖 Generated with Claude Code