Model selection plugin, browser half: TWO entries over ONE per-session directory owned by ModelService (ctx.models). For ordinary sessions, the /model popupSelect contribution (registered through ctx.command) and the composer's named conversation.input.model seat both load the session's advisory directory through session.models and submit through session.selectModel via the same ModelDirectory instance. The compact composer trigger opens a two-level Model/Effort menu: models stay provider-grouped, while the selected exact model supplies its adapter-owned effort names, descriptions, and default. The Host-reported provider/model/reasoning target is the single fact both entries echo; /model applies the selected model's default effort, and the composer can then choose any advertised effort. Directory loads and selections share a generation counter so an older response never overwrites a newer one; a connection reset drops every resident projection and repulls the Host-restored target before display. Provider-local metadata failures list inline while usable groups stay selectable, and selection failures retain the prior target and directory. Directories are per-session, resolved lazily through ctx.models.directoryFor(sessionId), and disposed with the session scope. Addressed subagent sessions expose neither entry, and their directory rejects loads, selections, and reconnect refreshes, because ordinary Agent-bound model RPCs would activate persisted child history outside the direct-parent continuation seam.

The /client export surface is the plugin body (apply/inject), ModelService, ModelDirectory with its state shape, and the seat's injected face type.

Model Experience

Indirectly, through the session.selectModel RPC available to ordinary sessions, both entries submit the provider/model/reasoning target that the Host snapshots at the next prompt-assembly boundary, so the following request uses the chosen route and effort while a running step keeps its assembled target; the selection becomes durable only when the existing request header records a request that consumes it, and menu interaction adds no prompt content.

KV Cache effect

Switching the route can reduce or invalidate provider-side cache reuse for subsequent requests; the prompt prefix itself is untouched.

Known Limitations and Deferred Work

No create-time or addressed-subagent selection — both entries require an existing ordinary session's Agent; there is no draft-phase model choice to fold into session creation, and subagent continuation deliberately exposes no independent model-retargeting contract.
Directory names are presentation-only — selection and persistence use provider/model/effort ids; a provider whose catalog or exact-model metadata lookup fails lists as an unselectable failure row until reload.
No arbitrary effort input — the composer offers only the exact model's adapter-advertised levels; an adapter without reasoning metadata leaves the Effort row absent.