Debugging Agent Failures: Silent Successes on Empty Results Are Most Dangerous

Necessary_Bison_2804 · reddit · 2026-08-06

After logging four weeks of agent runs, the author discovered that model reasoning failures are rarely the root cause of task deaths. The most common issues stem from malformed tool calls or incorrect paths due to state drift.

The most critical failure mode is silent success on empty results. The agent receives an empty result, treats it as a success, and continues executing, which poisons downstream logic. The run appears fine until the diff is reviewed. Actual bad reasoning was the smallest bucket and usually recoverable.

When selecting an executor model, the author now prioritizes the stability of tool call formatting over benchmark scores, noting that models like Ling-3.0-flash with native parsers and auto tool choice reduce the risk of mangling.

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