fix: send sdkMcpServers field in initialize control request#637
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drillan wants to merge 1 commit intoanthropics:mainfrom
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fix: send sdkMcpServers field in initialize control request#637drillan wants to merge 1 commit intoanthropics:mainfrom
drillan wants to merge 1 commit intoanthropics:mainfrom
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The Python SDK's Query.initialize() was not including the sdkMcpServers field in the initialize control request. This caused the Claude Code CLI to never register SDK MCP servers, making their tools invisible to the model. The TypeScript SDK (v0.2.49) correctly sends this field. This fix aligns the Python SDK with the TypeScript SDK behavior, following the same pattern as PR anthropics#468 which added the agents field to initialize. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This was referenced Mar 5, 2026
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Summary
The Python SDK's
Query.initialize()does not include thesdkMcpServersfield in the initialize control request. This causes the Claude Code CLI to never register SDK MCP servers, making their tools invisible to the model.The TypeScript SDK correctly sends this field. This fix aligns the Python SDK with the TypeScript SDK behavior.
Supersedes #596 (which also included end_input fixes now covered by #630).
Relates to #597.
Changes
query.py: AddsdkMcpServersfield to initialize control request when SDK MCP servers are configuredtest_initialize_sdk_mcp_servers.py: 5 test cases covering all scenarios (present, empty, None, non-streaming, combined with agents)Test plan
pytest tests/test_initialize_sdk_mcp_servers.py)