A long build on Claude died at the Agent SDK's turn cap and showed the
CLI's token for it — "Claude stopped: error_max_turns" — with no sign-off
and no sign the work was resumable. The budget and the ending are now one
policy in lib/turnBudget, shared by all three providers.

A run that spends its steps is carried on: Gemini steers itself, and a
Claude run resumes from its own session id, so the next run carries the
whole tool history. Three extensions, 24 steps each, a 96 ceiling — Claude
gains 66 steps on what it had. Once the ceiling is spent the turn hands
back in a sentence, and a turn that ends saying nothing gets the same
line, which Codex needed: it has no step cap, but a turn of tool chips
with no words is not an ending either.

Provider stop tokens never reach the chat. Claude's non-success subtypes
and Codex's turn.failed both go through stopText, which prefers the
provider's own sentence and writes a plain one otherwise.