fix(error_classifier): narrow max_tokens pattern to avoid matching empty-response advisories (#66818)

[webtecnica]

Summary

Empty-response advisories (e.g. nano-gpt / OpenRouter) include very low max_tokens as a possible cause. The literal substring max_tokens matched _CONTEXT_OVERFLOW_PATTERNS, causing Hermes to misclassify the error as context overflow, enter the compression loop, and end with Cannot compress further.

Fix

Narrowed max_tokens → max_tokens limit in _CONTEXT_OVERFLOW_PATTERNS.

• Advisory text like very low max_tokens no longer matches (does not contain limit)
• Real overflow messages like exceeds the max_tokens limit still match

Verification

• python3 -m py_compile agent/error_classifier.py ✅
• Existing tests pass (the GPT-5 max_tokens is not supported false positive is already guarded by the request-validation check that runs before context_overflow)
• No test asserted bare max_tokens alone matches an overflow

Closes #66818

[alt-glitch]

This was generated by AI during triage.

Duplicate of #66818. Both address empty-response advisories mentioning low max_tokens entering the compression loop; #66818 is the earlier, broader fix and preserves valid bare-max_tokens overflow handling.

[teknium1]

Thanks for this, @webtecnica — you nailed the exact root cause (the bare max_tokens substring in _CONTEXT_OVERFLOW_PATTERNS matching nano-gpt/OpenRouter empty-response advisories and sending healthy sessions into the compression death-spiral).

We landed the fix in #66818 (merged as 032a424). It takes a slightly different approach than narrowing max_tokens → max_tokens limit: bare max_tokens is load-bearing — the output-cap-retry path keys off it (e.g. max_tokens: 65536 > context_window: 200000), and some real-overflow phrasings don't contain "limit", so narrowing the pattern would lose coverage. Instead #66818 adds an _EMPTY_PROVIDER_RESPONSE_PATTERNS interceptor that runs before the overflow match in all four classifier paths (400, 500, 503/529, message-only), routing the advisory to retryable server_error with should_compress=False while leaving the overflow list intact.

Closing as redundant, but your diagnosis was spot-on. Appreciate you catching it.