The CLI/TUI /model switch mutates the running agent, and its codex session
(and thread) is reused, so the model fixed at thread/start stayed in force
for the rest of the session. turn/start accepts a model that codex applies
to that turn and later ones (codex 0.147 schema; live: a thread started on
codex's default ran a turn on gpt-5.5 with modelContextWindow 258400).
Every turn now sends the agent's current wire model.
78cd32c81c