fix(app): remember selected model variant when switching sessions/projects (#27029)

packages/app/src/context/local.tsx

@@ -44,7 +44,7 @@ const migrate = (value: unknown) => {
 }
 
 const clone = (value: State | undefined) => {
-  if (!value) return undefined
+  if (!value) return
   return {
     ...value,
     model: value.model ? { ...value.model } : undefined,
@@ -104,7 +104,7 @@ export const { use: useLocal, provider: LocalProvider } = createSimpleContext({
 
     const pickAgent = (name: string | undefined) => {
       const items = list()
-      if (items.length === 0) return undefined
+      if (items.length === 0) return
       return items.find((item) => item.name === name) ?? items[0]
     }
 
@@ -227,14 +227,14 @@ export const { use: useLocal, provider: LocalProvider } = createSimpleContext({
         () => agent.current()?.model,
         fallback,
       )
-      if (!item) return undefined
+      if (!item) return
       return models.find(item)
     }
 
     const configured = () => {
       const item = agent.current()
       const model = current()
-      if (!item || !model) return undefined
+      if (!item || !model) return
       return getConfiguredAgentVariant({
         agent: { model: item.model, variant: item.variant },
         model: { providerID: model.provider.id, modelID: model.id, variants: model.variants },
@@ -314,11 +314,16 @@ export const { use: useLocal, provider: LocalProvider } = createSimpleContext({
         configured,
         selected,
         current() {
-          return resolveModelVariant({
+          const resolved = resolveModelVariant({
             variants: this.list(),
             selected: this.selected(),
             configured: this.configured(),
           })
+          if (resolved) return resolved
+          const model = current()
+          if (!model) return
+          const saved = models.variant.get({ providerID: model.provider.id, modelID: model.id })
+          if (saved && this.list().includes(saved)) return saved
         },
         list() {
           const item = current()
@@ -335,6 +340,9 @@ export const { use: useLocal, provider: LocalProvider } = createSimpleContext({
               variant: value ?? null,
             })
             write({ variant: value ?? null })
+            if (model) {
+              models.variant.set({ providerID: model.provider.id, modelID: model.id }, value ?? undefined)
+            }
           })
         },
         cycle() {