fix(chat): graceful degradation for malformed tool call arguments (v2)

[huckstack]

DISCLOSURE

This contribution was developed by a human (David @ huckstack) with assistance from an AI coding agent (Hermes). The human reviewed and approved all changes.

Problem

When models generate malformed JSON in tool call arguments (e.g., unescaped single quotes like log_dir = '/home/user/.hermes/logs/cron'), func_args_not_string() throws an HTTP 500 error. This causes cascading failures where every subsequent request crashes with Failed to parse tool call arguments as JSON: unexpected end of input.

The function was introduced in commit b283f6d with throw, which converts a recoverable parsing error into a hard server error.

Fix

Replace throw with LOG_WRN in func_args_not_string(). This converts the hard 500 error into graceful degradation — the server logs a warning and keeps the arguments as a string, allowing the conversation to continue.

Context

This is a pragmatic workaround, not a root fix. The core issue is that the PEG parser in the TAG_WITH_TAGGED tool format (introduced by PR #21216) fails on malformed JSON in parameter values. See issue #21771 for the full analysis of the parser regression.

Related: #21771, #22072, #12068 (hermes-agent)

Testing

This fix has been validated on:

• Pop!_OS with llama.cpp b8833
• Qwen3.6-35B-A3B local endpoint
• RTX 3060 (12GB VRAM)

The fix prevents the HTTP 500 cascade while allowing the conversation to continue. The warning is logged for debugging purposes.

[CISC]

Duplicate of #22089

[ggml-gh-bot]

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