model_not_supported errors from providers (e.g. OpenAI returning
{"error": {"code": "model_not_supported"}}) were not recognized as
retryable. Subagents would silently fail with no response, hanging the
parent session.
Fix:
- Add "model_not_supported", "model not supported", "model is not
supported" to RETRYABLE_MESSAGE_PATTERNS in model-error-classifier.ts
- Add regex patterns to RETRYABLE_ERROR_PATTERNS in
runtime-fallback/constants.ts to match "model ... is ... not ...
supported" with flexible spacing
- Add regression test covering all three variations
Now model_not_supported errors trigger the normal fallback chain instead
of silent failure.