feat: New agent harness selector

[charlesvien]

Problem

Model and reasoning selection was split across per-surface dropdowns with drifting labels, five duplicated effort-type unions and no way to set context window or fast mode.

https://screen.studio/share/tvIw08EP

Changes

One merged control. Model and reasoning are a single pill ("Claude Opus 5 High") on the new-task composer, channel composer and session view. It opens on a Faster ($) / Smarter ($$$) slider with five preset notches that set model plus effort together (Claude: Sonnet 5 medium/high, Opus 5 medium/xhigh, Fable 5 max; GPT: 5.6 Terra low, then 5.6 Sol low/medium/high/xhigh). The drag is continuous, updates the pill live and snaps on release. A lightning toggle flips fast mode, with a themed hover tooltip showing "Fast Mode (ON/OFF)" and an adapter-specific "Learn more" docs link; the pill gets a yellow inset ring and lightning icon while it's on.

Advanced view. The menu morphs into per-setting submenus: Harness, Model (picker-ordered, restricted models gated), Reasoning (Default badge, "?" docs link on Ultracode), Context Window (200k/1M) and "Reset to default" (middle notch, default context, fast off). A custom off-preset combo opens straight on Advanced until reset.

Behavior.

• ultracode effort ships on extended Claude models; context window live-toggles the 1M beta; fast mode includes Opus 5 and sits behind posthog-desktop-fast-mode (default off).
• Selections persist across restarts and restore on the composers; switching harness resets to that harness's middle notch. Existing installs get their saved selections busted once via a store version bump.
• Cloud runs send the raw effort plus context_window/fast_mode (env-forwarded to the sandbox). Needs feat(tasks): Accept context window and fast mode on runs posthog#73803 deployed first.

Consolidation. EffortLevel, labels and docs URLs live once in @posthog/shared; loops, analytics, settings stores, mobile and the agent package alias them. Loops, settings default effort, autoresearch stage pickers and agent-application config all render the same shared dropdown in list form.

Slider (default view, shown with the fast-mode flag enabled):

Advanced (Reasoning submenu open):

How did you test this?

pnpm typecheck across all 24 packages; full agent/core/ui/workspace-server suites (three consecutive green UI runs after de-flaking the menu tests); drove the real app over CDP to verify the pill, slider, fast toggle, advanced submenus, model ordering and the post-migration defaults (screenshots above).

Automatic notifications

• Publish to changelog?
• Alert Sales and Marketing teams?

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[github-actions]

React Doctor found 3 issues in 2 files · 3 warnings.

3 warnings

src/features/sessions/components/ReasoningLevelDropdown.tsx

• ⚠️ src/features/sessions/components/ReasoningLevelDropdown.tsx:414 Role used instead of HTML tag prefer-tag-over-role

src/features/sessions/components/ReasoningLevelSelector.tsx

• ⚠️ src/features/sessions/components/ReasoningLevelSelector.tsx:45 Full Framer Motion import use-lazy-motion
• ⚠️ src/features/sessions/components/ReasoningLevelSelector.tsx:127 Large component is hard to read and change no-giant-component

_{Reviewed by React Doctor for commit 8033e36.}

[posthog]

✅ Visual changes approved by @charlesvien — baseline updated in 68d5078.

View this run in PostHog

6 changed.

[tatoalo]

noice

[k11kirky]

love it