fix(grok): allow model changes in existing threads

[ahmed-besic]

Grok supports session/set_model, and T3's adapter already applies a changed model before the next prompt. However, the provider snapshot still marked Grok as requiring a new thread, so the client disabled model changes and the server rejected them before they reached the adapter.

This removes that stale provider lock. Existing client and server behavior now passes the changed selection through to Grok, which switches models within the active session.

Fixes #8385. Builds on the Grok reliability work merged in #8358. The same lock removal appeared in the broader closed PRs #6383 and #7070; this PR isolates only the missing behavior. #6075 remains separate and tracks invalid synthetic grok-build model IDs.

Checks:

• vp test run apps/server/src/provider/Layers/GrokProvider.test.ts apps/server/src/orchestration/Layers/ProviderCommandReactor.test.ts apps/web/src/components/ChatView.logic.test.ts (111 passed)
• targeted format and lint checks
• server and web typechecks
• real Grok 1.0.5 ACP session: completed a prompt, then accepted session/set_model for another advertised model

No UI components changed, so there are no before/after screenshots.

Implemented with GPT-5.6 Sol through the Codex harness in T3 Code.

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Note

Low Risk
Single presentation-field removal with no auth or data-path changes; behavior aligns with already-implemented Grok ACP model switching.

Overview
Grok no longer advertises that model switches require a new thread. The provider presentation drops requiresNewThreadForModelChange: true, so snapshots no longer carry that lock even though Grok ACP already supports session/set_model in the active session.

With the flag gone, existing client and server paths can accept mid-thread model changes instead of blocking them up front. The initial snapshot test now expects requiresNewThreadForModelChange to be undefined rather than true.

^{Reviewed by Cursor Bugbot for commit c262aa9. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Remove requiresNewThreadForModelChange from GROK_PRESENTATION in GrokProvider

Allows Grok model changes in existing threads by removing the requiresNewThreadForModelChange: true flag from the GROK_PRESENTATION constant in GrokProvider.ts. Updates the pending snapshot test to expect the property as undefined.

• Risk: any consumer reading requiresNewThreadForModelChange from GROK_PRESENTATION or derived snapshots will now see undefined instead of true.

^{Macroscope summarized c262aa9.}

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[macroscopeapp]

Approvability

Verdict: Approved at c262aa9

Macroscope's review found this PR approvable — This is a minimal, self-contained fix removing Grok’s stale new-thread restriction so the existing session/set_model path can handle model changes in active threads. It introduces no schema, security, billing, deployment, or new component changes.

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