WebShell Qwen 3.8 reasoning controls

Goal

Expose Thinking and effort controls for the exact qwen3.8-max model in the WebShell model popover, including the welcome state before a lazy session is created. A welcome selection applies to that lazy session before its first prompt; acknowledged live changes apply only to subsequent requests.

Design

A small agent-side model manifest declares that qwen3.8-max supports Thinking and the native effort values low, medium, and xhigh, with xhigh as its display default. The manifest is matched by exact model id and does not apply to preview, dated, aliased, or runtime models.

The agent projects that entry through ACP's existing reasoning_effort configuration option. For this model only, the option contains none plus the three manifest values. WebShell renders none as Thinking off and renders the remaining values as effort choices. No second effort configuration id is introduced.

Both workspace-provider producers expose that same manifest-built option as an optional, per-model configOptions preview. The field is an additive v1 projection: older clients can ignore it and older daemons simply omit it. The WebUI maps a valid option onto that model's own reasoningPreview, rather than onto connection-wide reasoning state, so changing models cannot leak the capability.

WebShell applies the following priority:

1. When both sessionId and session context are absent, it may render the selected model's workspace preview. The controls update a local, one-shot intent bound to that exact model.
2. Once a session id is allocated but its context has not arrived, WebShell hides the preview.
3. Once context for that session arrives, its currentValue, options, and Thinking state are authoritative. An absent or incompatible live option hides the controls and never falls back to the preview.

The welcome preview deliberately does not create an empty session. Hosts such as DataWorks use lazy creation so the first prompt can create or adopt the real daemon session; pre-creating one would change that contract and leave empty sessions behind. Selecting a welcome effort only records local intent. The first prompt creates and attaches the session, sets the selected model, applies the effort through the live config-option mutation, and then submits the prompt. A model or effort mutation that cannot be confirmed fails closed: WebShell releases the unused session, keeps the composer and intent available for retry, and does not send the prompt.

The intent is cleared after successful preparation or after an unrelated session is attached. It is not a workspace default and is never persisted or broadcast. If the user changes models before submission, the model-bound intent is not applied to the other model.

WebShell retains PR #8675's interaction design: the current reasoning state is shown as a suffix on the model chip, reasoning options occupy the first model popover, and model search is opened from its Model submenu.

Selecting none applies Thinking off to the next lazy session or the current live session. Selecting an effort applies that effort and enables reasoning. Reading the manifest alone does not inject a default into generation configuration, so sessions that never change the controls retain main's existing wire behavior.

If the live session already carries a generic effort outside the manifest (high or max), ACP preserves that value through its existing generic option and WebShell hides the model-specific controls. This avoids displaying an inaccurate tier or changing live configuration merely by opening the popover.

The daemon exposes one owner-routed config-option mutation. Its public route is restricted to reasoning_effort; the response carries fresh configOptions, which becomes the caller's authoritative UI state. No observer or broadcast is added.

Scope

Included:

• exact stable qwen3.8-max only;
• an editable, one-shot welcome preview with xhigh as the manifest default;
• application after lazy attach and model selection but before the first prompt;
• authoritative replacement by same-session context;
• the current WebShell conversation;
• Thinking on/off and low, medium, xhigh effort;
• browser coverage for welcome, live override, model switching, old daemons, and the existing live mutation behavior.

Excluded:

• persistence across sessions or restarts;
• persisted/default-model semantics;
• workspace-level, reusable, or cross-client reasoning defaults;
• preview, aliases, and future reasoning-control shapes;
• route and runtime models;
• TUI, channel, provider, auth-refresh, and runtime-snapshot behavior;
• capability flags and cross-client model/config broadcasts.

Compatibility

Only a raw, non-runtime, non-route model whose exact manifest id is qwen3.8-max receives the preview. Preview, dated, aliased, opaque route, runtime, and unrelated models do not. Older daemons omit the optional model field, so WebShell does not infer or invent welcome-state capability. Existing sessions continue to obey the daemon's live configOptions, including Thinking off, non-default effort, missing capability, and incompatible option shapes. Non-target sessions keep the existing generic ACP effort behavior, and clients that do not consume the additive field remain compatible.