A narrow research question could burn all 8 steps on tool calls and end the
turn with no assistant text (empty turn). Two changes:
- MAX_AGENT_STEPS = 20 (was a magic stepCountIs(8)) so multi-search turns
aren't cut off mid-investigation.
- prepareStep reserves the LAST allowed step for a text-only synthesis:
toolChoice 'none' + a FINAL_STEP_INSTRUCTION appended to (not replacing)
the system prompt, so a tool-heavy turn always ends with a real answer.
Logic extracted into the pure, exported prepareAgentStep(stepNumber, system)
for unit testing; earlier steps return undefined (default behavior).
Implements docs/backlog/ai-chat-step-limit-and-forced-final-answer.md.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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