feat: per-axis Cursor model-state selector (effort/thinking/fast/context)

[justin-carper]

What

Adds a per-axis Cursor model-state selector to the plugin. Cursor models expose several independent state axes — effort/reasoning level, thinking on/off, fast on/off, context window — which the catalog pre-enumerates as a full cartesian variants[] (e.g. claude-opus-4-8 has 40 variants). A flat 40-entry cycler is unusable, so this feature lets the user cycle each axis independently via hotkeys, with a live status widget and per-session persistence.

Why

The plugin previously surfaced only a subset of states (effort + fast) folded into one cycler. Thinking, context, Max-mode (effort max), and per-axis composition were unreachable. This delivers the full state matrix through an efficient per-axis UI instead of an unusable flat list.

How

Two-target plugin package:

• ./server (existing Hooks) — unchanged behavior. chat.params gains an additive read+merge of the composed selection.
• ./tui (new TuiPlugin) — registers per-axis cycle hotkeys, a live status widget in the session_prompt_right slot, and persists the composed selection.

Pure, unit-tested core:

• src/model-axes.ts — buildModelAxes derives independent axes from item.variants[]; isValidCombo / snapCombo handle asymmetric models (e.g. gpt-5.5 only offers fast at context=272k).
• src/tui/axis-state.ts — seedSelection, cycleAxis (immutable, wraps), formatSelection, reconcileSelection.

Cross-half bridge: opencode exposes no client API for persistent session model options and no cross-half KV endpoint, so the two plugin halves share state through a file both compute identically: src/tui/state-file.ts writes <cacheDir>/cursor-states.json keyed by sessionID (atomic temp+rename); the server chat.params hook reads it and merges string-only params into output.options.params. src/provider/controls.ts (the Cursor wire-shaping path) is unchanged.

Default hotkeys (overridable in tui.json): ctrl+e effort/reasoning, ctrl+t thinking, ctrl+f fast, ctrl+k context; shift+<key> = previous. A toast shows each new value; the widget shows the composite (high · think · fast · 1m).

--pure / no-TUI fallback: buildModelVariants still feeds opencode's native variant_cycle, now re-sourced from axes as a curated, non-cartesian short list (one entry per non-default axis value — never 40).

Requirements

• opencode >= 1.17.0 (engines.opencode) — first version shipping the TUI plugin API.
• @opentui/core, @opentui/solid, solid-js are optional peer dependencies (host-provided at runtime, external in the build) so server-only / --pure installs are unaffected.

Testing

• npm test — 324 passing across 30 files (new model-axes, axis-state, state-file suites; updated model-variants, model-v2, model-discovery).
• npm run build and npm run typecheck clean.
• Pure logic is tested against a committed fixture of the live 30-model catalog (test/fixtures/cursor-catalog.json), covering the 40-variant, asymmetric, toggle-only, and no-axis shapes.

Manual smoke (requires a real opencode >= 1.17.0 runtime — not automatable here)

1. Build, npm pack, install the tarball's ./tui in a scratch tui.json plugin array and the ./server half as the provider plugin.
2. Open a session with cursor/claude-opus-4-8 and send one message (an assistant message is how the TUI half detects the active Cursor model).
3. ctrl+e → toast shows Effort: <next>, widget updates. shift+ctrl+e reverses.
4. ctrl+t / ctrl+f / ctrl+k → thinking / fast / context change; widget reflects the composite.
5. Switch to cursor/gemini-3.1-pro → no axes; hotkeys inert; widget shows model name only.
6. Confirm <cacheDir>/cursor-states.json contains { "<sessionID>": { ...selection } }.
7. Send another message; confirm (server logs) the Cursor request carries the composed params.

Known v1 limitations

• One global in-memory selection. The persisted state file is per-session-keyed, but the in-memory selection + widget are global, so two concurrently-rendered session prompts would display one shared selection. Fine for a single active prompt; revisit for multi-prompt.
• Native --pure fallback + default-ON toggles. A toggle that defaults ON (e.g. composer-2.5's fast) produces no curated fallback entry for that axis. The TUI cycler covers the full range; only the deprioritized --pure list is affected.
• Axis reflects the last Cursor assistant model in the session (there is no model-selection event to hook).