feat(mothership): let the worker choose models when the model picker is off (#8669)

* feat(mothership): let the worker choose models when the model picker is off

With the picker off, chats sent the hidden hosted default selection (GPT-6 Astra),
which the worker treats as an explicit pick for both the main agent and subagents.
No selection is sent now, so the worker routes every model role itself. A stale
client selection is still cleared at admission. Picker-on chats and the Sim Chat
block are unchanged.

* test(mothership): assert the omitted selection on the serialized worker request

* test(mothership): read the serialized request without a JSON round trip

Author: waleedlatif1

apps/sim/app/workspace/[workspaceId]/home/components/user-input/components/model-selector.tsx

@@ -45,7 +45,7 @@ export function ModelSelector() {
     { effort: effortChoice ?? undefined, modelSelection: selection },
     advanced
   )
-  const options = advanced
+  const options = modelSelection
     ? mothershipEffortOptions(modelSelection.model)
     : MOTHERSHIP_SIMPLE_EFFORT_OPTIONS
   const setEffort = (choice: MothershipEffort) => {
@@ -59,13 +59,10 @@ export function ModelSelector() {
   }, [chatId])
 
   const effortLabel = options.find((option) => option.value === effort)?.label ?? effort
-  const modelLabel =
-    MOTHERSHIP_MODEL_OPTIONS.find((option) => option.value === modelSelection.model)?.label ??
-    modelSelection.model
 
   return (
     <div className='flex items-center gap-[inherit]'>
-      {advanced && (
+      {modelSelection && (
         <>
           {modelSelection.model !== 'claude-opus-5-5' && (
             <FastModeToggle
@@ -77,7 +74,10 @@ export function ModelSelector() {
           <DropdownMenu modal={false}>
             <ModelSettingTrigger
               label='Model'
-              valueLabel={modelLabel}
+              valueLabel={
+                MOTHERSHIP_MODEL_OPTIONS.find((option) => option.value === modelSelection.model)
+                  ?.label ?? modelSelection.model
+              }
               icon={Sparkles}
               showChevron
             />

apps/sim/lib/mothership/chat/post.test.ts

@@ -816,7 +816,7 @@ describe('handleUnifiedChatPost', () => {
     ['low', 'low'],
     ['none', 'high'],
   ])(
-    'enforces the default model and effort range on submitted %s effort',
+    'leaves the model to the worker and enforces the effort range on submitted %s effort',
     async (effort, expected) => {
       flags.models.mockResolvedValue(false)
       const response = await handleUnifiedChatPost(
@@ -831,12 +831,9 @@ describe('handleUnifiedChatPost', () => {
         })
       )
       expect(response.status).toBe(200)
-      expect(buildCopilotRequestPayload).toHaveBeenCalledWith(
-        expect.objectContaining({
-          effort: expected,
-          modelSelection: { model: 'gpt-6-astra', fastMode: false },
-        })
-      )
+      const { requestPayload } = createSSEStream.mock.lastCall?.[0] ?? {}
+      expect(requestPayload?.effort).toBe(expected)
+      expect(JSON.stringify(requestPayload)).not.toContain('modelSelection')
     }
   )
 

apps/sim/lib/mothership/model-options.ts

@@ -38,22 +38,29 @@ export function mothershipEffortOptions(model: ModelSelection['model']) {
     : MOTHERSHIP_EFFORT_OPTIONS
 }
 
-/** Shared by the visible controls, send path and server admission so hidden preferences cannot leak. */
+/**
+ * Shared by the visible controls, send path and server admission so hidden preferences cannot leak.
+ * Without the model picker no selection is sent, so the worker routes every model role itself.
+ */
 export function resolveMothershipModelSettings(
   settings: { effort?: MothershipEffort; modelSelection?: ModelSelection },
   advanced: boolean
-): { effort: MothershipEffort; modelSelection: ModelSelection } {
+): { effort: MothershipEffort; modelSelection: ModelSelection | undefined } {
   let effort = settings.effort ?? DEFAULT_MOTHERSHIP_EFFORT
   if (!advanced) {
     if (effort === 'none') effort = DEFAULT_MOTHERSHIP_EFFORT
     if (effort === 'max') effort = 'xhigh'
-    return { effort, modelSelection: { model: 'gpt-6-astra', fastMode: false } }
+    return { effort, modelSelection: undefined }
   }
-  const stored = settings.modelSelection ?? { model: 'gpt-6-astra', fastMode: false }
+  const modelSelection = normalizeModelSelection(
+    settings.modelSelection ?? { model: 'gpt-6-astra', fastMode: false }
+  )
+  if (effort === 'none' && modelSelection.model !== 'gpt-6-sol') effort = DEFAULT_MOTHERSHIP_EFFORT
+  return { effort, modelSelection }
+}
+
+/** A stored pick on the current catalog: Opus 5 reads as Opus 5.5, which has no Fast mode. */
+export function normalizeModelSelection(stored: ModelSelection): ModelSelection {
   const model = stored.model === 'claude-opus-5' ? 'claude-opus-5-5' : stored.model
-  if (effort === 'none' && model !== 'gpt-6-sol') effort = DEFAULT_MOTHERSHIP_EFFORT
-  return {
-    effort,
-    modelSelection: { model, fastMode: model === 'claude-opus-5-5' ? false : stored.fastMode },
-  }
+  return { model, fastMode: model === 'claude-opus-5-5' ? false : stored.fastMode }
 }

apps/sim/stores/mothership-effort/store.ts

@@ -2,10 +2,7 @@ import { omit, toRecord } from '@sim/utils/object'
 import { create } from 'zustand'
 import { devtools, persist } from 'zustand/middleware'
 import { type ModelSelection, ModelSelectionSchema } from '@/lib/mothership/generated/protocol'
-import {
-  type MothershipEffort,
-  resolveMothershipModelSettings,
-} from '@/lib/mothership/model-options'
+import { type MothershipEffort, normalizeModelSelection } from '@/lib/mothership/model-options'
 
 /** A chat's effort pick and the token that tells it apart from other picks of the same value. */
 interface ChatEffortPick {
@@ -52,7 +49,7 @@ let lastChatEffortPick = 0
 function withModelSelection(
   modelSelection: ModelSelection
 ): Pick<MothershipEffortState, 'modelSelection'> {
-  return { modelSelection: resolveMothershipModelSettings({ modelSelection }, true).modelSelection }
+  return { modelSelection: normalizeModelSelection(modelSelection) }
 }
 
 export const useMothershipEffortStore = create<MothershipEffortState>()(