When an LLM response arrives with finish_reason='length' and has_tool_calls
but blank text content (e.g. the model spent its whole output budget on a
tool call whose closing tag was truncated), the runner dropped the tool
calls and then misrouted the blank response into the empty-response retry
branch. Retrying the same prompt cannot recover from output-budget
exhaustion, so every retry hit the same length ceiling and the turn ended
in the generic apology.
The length-recovery branch was gated on 'finish_reason == length and not
is_blank_text(clean)', so a blank-but-truncated turn could never reach it.
- The empty-response retry branch now excludes finish_reason == 'length'
(in addition to 'error').
- The length-recovery branch no longer requires non-blank content, so a
blank-but-truncated turn enters recovery and appends
build_length_recovery_message (which handles a blank tail safely).
Adds a regression test asserting the length-recovery path is taken; it
fails on the unfixed code and passes with the fix.
Fixes#5133
511c764f45