After `/model`, the header kept the previous model's window ("15K /
1.0M" on a 262K model) until the next turn or a restart. The pager
caches the window inside its context snapshot (streaming `totalTokens`
updates refresh it from the catalog) and nothing refreshed the cache
when the session's model changed. Comparing cached numbers against
catalog windows cannot tell a catalog-derived total from a shell
effective limit (KIGI_DEBUG_CONTEXT_WINDOW, header upgrades), so the
shell, which installs the effective window, now reports it:
- kigi-shell: `handle_set_session_model` returns the installed window;
`model_switch::apply` stamps it as `totalContextTokens` in the
`session/set_model` response meta and carries it on the
`ModelChanged` broadcast (`context_window`, serde-default: old pagers
ignore it, old leaders omit it). The response meta previously
serialized the actor's inner `Result` and reported success on an
actor failure; that error now propagates.
- kigi-tui: `Effect::SwitchModel` reads the meta; `SwitchModelComplete`
carries `Ok(Option<u64>)`; the completion handler and the follower
`ModelChanged` arm call `AgentView::apply_context_window`, which
re-derives the snapshot (pct, free tokens) and reports whether it
changed so a follower redraws on a window-only change.
- Tests: the bare `/model <name>` dispatch path asserts the snapshot and
the drawn header; follower with/without the field; same-model new
window redraw; actor returns the window; serde round trip.
Claude-Session: https://claude.ai/code/session_01RUqV8HVGXcAETyYbZ2tPQ4
雷电芽衣
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