fix(grok): surface per-model reasoning effort in the composer

[ahmed-besic]

What Changed

Grok already advertises per-model reasoning effort menus over ACP (models.availableModels[]._meta.reasoningEfforts), but T3 published every Grok model with empty capabilities and never applied a selected effort. The composer therefore had no Reasoning control for Grok, unlike Claude/Codex.

This maps each model's advertised menu into optionDescriptors (reasoningEffort), passes _meta.reasoningEffort through session/set_model on session start and each turn (including mid-thread effort-only changes), and wires the same selection into Grok text generation.

Why

Grok Build supports Low/Medium/High (and other per-model menus for custom models). Without reading _meta and applying effort on session/set_model, T3 always ran at the CLI default and users could not change it from the UI.

Related open work: #5160 takes a spawn-flag approach and blocks mid-thread changes. This PR is narrower: discovery + apply via the existing ACP session/set_model _meta path, which Grok applies in place without restarting the process.

UI Changes

Uses the existing Traits picker — no new UI components. Once Grok ACP discovery succeeds, models with reasoningEfforts show a Reasoning select; models with different menus keep their own options.

• Before: Grok models have no Reasoning control in the composer traits menu.
• After: Grok models that advertise effort menus show Reasoning, and the selected value is applied on the next send (same thread is fine for effort-only changes).

Live-verified against grok agent stdio and the T3 web UI over Tailscale.

Validation

• vp test run src/provider/acp/GrokAcpSupport.test.ts src/provider/Layers/GrokProvider.test.ts — 17 passed
• Live ACP probe: session/set_model with _meta.reasoningEffort applies the override
• Manual web UI check: Reasoning control appears for discovered Grok models and updates per model

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes (happy to add if needed — behavior uses the existing traits control)
• A video is not applicable (no animation/timing change)

Made by Grok Build via the Grok Build harness while working on T3 Code.

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Note

Medium Risk
Changes the Grok ACP session/set_model path on every session start and turn; behavior is additive (_meta extension) and covered by tests, but incorrect effort values could affect model behavior at runtime.

Overview
Grok ACP models can advertise per-model reasoning effort menus in availableModels[]._meta, but T3 previously published empty capabilities and never applied a user’s effort choice. This PR wires that through end-to-end.

Discovery: buildGrokCapabilitiesFromModelMeta maps reasoningEfforts / reasoningEffort into a Reasoning select (reasoningEffort) on each discovered model, so the existing composer traits picker can show it after ACP discovery.

Apply: applyGrokAcpModelSelection now reads trait selections and calls session/set_model with _meta.reasoningEffort when the model changes or when only effort changes mid-thread. AcpSessionRuntime.setSessionModel passes optional _meta through. Grok adapter (session start + turns), and Grok text generation pass modelSelection.options into that path.

Unit tests cover capability mapping, discovered models, and effort-only / combined model+effort set_model calls.

^{Reviewed by Cursor Bugbot for commit 9e2fb80. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Surface per-model reasoning effort selection in the Grok composer

• Adds buildGrokCapabilitiesFromModelMeta in GrokProvider.ts to parse _meta.reasoningEfforts from model metadata into a select option descriptor, replacing the previous EMPTY_CAPABILITIES fallback.
• Extends applyGrokAcpModelSelection in GrokAcpSupport.ts to accept selections and call setSessionModel when a reasoningEffort selection is present, even if the model ID is unchanged.
• Updates AcpSessionRuntime.setSessionModel to accept and forward an optional options._meta payload so reasoning effort reaches the ACP set_model request.
• Propagates modelSelection.options through GrokAdapter.ts and GrokTextGeneration.ts to ensure selections apply during both session setup and text generation.

^{Macroscope summarized 9e2fb80.}

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[macroscopeapp]

Approvability

Verdict: Needs human review

This PR introduces new user-facing functionality (per-model reasoning effort selection in the composer), propagating new _meta configuration through multiple provider layers. New features that add user-facing behavior warrant human review.

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