[BUG] Model picker: `s` (use this session only) is honoured for the model but the effort column still writes effortLevel to settings.json globally

What's Wrong?

The /model picker has two commit actions in its footer: enter — set as default and s — use this session only. The picker edits two columns, model and effort.

Pressing s only applies session scope to the model column. The effort column is still written to ~/.claude/settings.json as effortLevel, so it becomes the global default and every session started afterwards inherits it.

So s is doing half of what it says. The user's intent when pressing it is "nothing here leaves this session", and one of the two things they just changed leaves anyway — silently, with no notice.

Observed (v2.1.233, macOS 26.6 arm64):

1. ~/.claude/settings.json before: "model": "opus[1m]", "effortLevel": "high" (file mtime 2026-08-13 21:04).
2. In a running session, /model → change the effort column to xhigh → commit with s (use this session only).
3. ~/.claude/settings.json after: "effortLevel": "xhigh", file mtime 2026-08-15 11:08:40 — rewritten by the s path.
4. Newly started sessions open at xhigh. The effort choice propagated globally despite s.

The model key was not observed to change in that run, consistent with s being honoured for the model column.

What Should Happen?

s should mean session-only for everything the picker just changed — both columns. Committing with s should leave settings.json byte-identical; enter should persist both model and effort.

This is what the standalone /effort command already does correctly — it distinguishes Set effort level to X (saved as your default for new sessions) from Set effort level to X (this session only). The picker's s path just isn't reaching that session-scoped write for its effort column.

Why this is worth fixing beyond the scope mismatch

The write happens on every commit through the picker, including when the user only meant to change the model — the effort column commits whatever value it is showing. Combined with effort levels that aren't offered for every model, this silently rewrites a user's global effort preference as a side effect of routine model switching. That downgrade path is already reported separately in #30726.

Related, and why this isn't a duplicate of any of them

• #49076 — /model silently persists effortLevel to settings.json. Same underlying write, reported in April, auto-closed as a duplicate by the bot against #30726 and #20745 without being addressed on its own terms.
• #20745 — model setting global across sessions. Closed as completed: the model half got session scope. The effort half was closed alongside it and did not. That is the asymmetry this issue is about, and it did not exist when #49076 was filed.
• #66402 — /model and /effort mutate global settings.json, framed around the agents/fleet view, and asserts both are global. That framing is now partly stale, and it is not about the s key.
• #85774 — /model <name> typed directly has no session-only equivalent. That is about the absence of s on the direct-typed form; this is about s being present and only half-applied.
• #85968 — feature request for session-scoped model selection. Already shipped as s; this issue is that s is incomplete.
• #30726 — effortLevel: max silently downgraded by the effort UI. A consequence of the same write, not the scope claim.

Environment Info

• Version: 2.1.233
• Platform: darwin (macOS 26.6, arm64)
• Terminal: fish / iTerm2