get_builtin_overrides() was swallowing all exceptions with a bare
`except Exception: pass`, so misconfigured tool-description overrides
would silently produce wrong agent behaviour with no log trace.
The background endpoint refresh loop had the same pattern: any probe
failure was silently ignored, giving operators no signal that the
refresh was broken.
Also removes a circular self-import (`from src.agent_loop import
_build_base_prompt`) inside _build_system_prompt; the function is
already in scope and the import created a latent circular reference risk.
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
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