pi-coding-agent swallows its own exceptions onto session.state.errorMessage
without preserving a stack, so fusion sees only "Cannot read properties
of undefined (reading 'filter')" with no indication which message is
malformed. When promptSessionAndCheck rethrows an error that matches the
generic TypeError shape, dump the last few state.messages (role, content
type, toolName, stopReason) so the offending message can be identified
next run.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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