Fix claude-code agent registration crash under spawn - #450
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…g spawn-safe passthrough builder - both is_claude_code branches in _register_workers built the tool_worker closure eagerly via make_claude_agent_sdk_worker, passed straight to _register_passthrough_worker for pickling - that closure is local to make_claude_agent_sdk_worker's frame, never picklable by reference -> SpawnSafetyError/PicklingError under the default spawn start method, for every claude-code agent (top-level or nested sub-agent) - _build_passthrough_func already builds a picklable PassthroughWorkerEntry for "claude_agent_sdk" -- just never called from these two sites; route both through it instead of hand-rolling the closure - adds TestClaudeCodeAgentRegistration (4 tests): entry-type assertions + regression tests confirming no SpawnSafetyError under the real chain
kowser-orkes
changed the title
Agent(model='claude-code/...') registration crash under spawn
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bradyyie
approved these changes
Jul 28, 2026
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Pull Request type
Changes in this PR
Both
is_claude_codebranches in_register_workers(runtime.py) built thetool_workerclosure eagerly in the parent process viamake_claude_agent_sdk_worker, then passed it straight to_register_passthrough_workerfor pickling. That closure is local tomake_claude_agent_sdk_worker's own frame and is never picklable byreference, so registration raised
SpawnSafetyError/PicklingErrorunderthe SDK's default
spawnstart method for everyclaude-codeagent — bothtop-level and nested as a sub-agent.
_build_passthrough_funcalready builds a picklablePassthroughWorkerEntryfor this exact framework (
"claude_agent_sdk") — it just wasn't called fromeither of these two sites. This PR routes both through it instead of
hand-rolling the closure.
Adds
TestClaudeCodeAgentRegistration(4 tests): two assert the entry handedto
_register_passthrough_workeris aPassthroughWorkerEntry, two areregression tests confirming no
SpawnSafetyErrorunder the realregistration chain (confirmed to fail pre-fix with the original traceback).
Issue #
Alternatives considered
Patch
make_claude_agent_sdk_worker's closure to be picklable directly —rejected because
_build_passthrough_funcalready solves this genericallyfor the framework, and duplicating that logic at the two call sites would
drift from it over time.