fix(app): stage Build when hiding the agent picker

Stage the Build agent and its model for the next prompt in an existing session without changing the running server session. The normal submission path applies that selection when the next steered prompt is sent.

packages/app/src/providers/models/agent.test.ts

@@ -1,12 +1,8 @@
 import { expect, test } from "bun:test"
-import { hasCustomAgent, resolveAgent } from "./agent"
-
-test("hasCustomAgent detects only explicitly custom agents", () => {
-  expect(hasCustomAgent([{ native: true }, { native: false }])).toBe(true)
-  expect(hasCustomAgent([{ native: true }, {}])).toBe(false)
-})
+import { resolveAgent } from "./agent"
 
 const agents = [{ name: "plan" }, { name: "build" }, { name: "custom" }]
+
 const rows: { name: string; agents: { name: string }[]; requested?: string; expected: string }[] = [
   { name: "the requested available agent", agents, requested: "custom", expected: "custom" },
   { name: "build without a request", agents, requested: undefined, expected: "build" },

packages/app/src/providers/models/agent.ts

@@ -1,7 +1,3 @@
-export function hasCustomAgent(items: Array<{ native?: boolean }>) {
-  return items.some((item) => item.native === false)
-}
-
 export function resolveAgent<T extends { name: string }>(items: T[], name?: string) {
   return items.find((item) => item.name === name) ?? items.find((item) => item.name === "build") ?? items[0]
 }

packages/app/src/providers/models/selection.tsx

@@ -9,7 +9,7 @@ import { useSettings } from "@/settings/model"
 import { useProviders } from "@/providers/catalog/providers"
 import { Persist, persisted } from "@/runtime/persistence/storage"
 import { Persistence } from "@/runtime/persistence/schema"
-import { hasCustomAgent, resolveAgent } from "./agent"
+import { resolveAgent } from "./agent"
 import { cycleModelVariant, getConfiguredAgentVariant, resolveModelVariant } from "./variant"
 import { useWorkspaceLocation } from "@/workspaces/location"
 import { useData } from "@/runtime/server/current"
@@ -98,7 +98,7 @@ export const { use: useLocal, provider: LocalProvider } = createSimpleContext({
       ),
     )
 
-    const agentsVisible = createMemo(() => settings.visibility.customAgents() || hasCustomAgent(list()))
+    const agentsVisible = settings.visibility.customAgents
     const connected = createMemo(() => new Set(providers.connected().map((item) => item.id)))
 
     const [saved, setSaved, , savedReady] = persisted(
@@ -266,6 +266,11 @@ export const { use: useLocal, provider: LocalProvider } = createSimpleContext({
       },
     }
 
+    createEffect(() => {
+      if (agentsVisible() || agent.current()?.name === "build") return
+      agent.set("build")
+    })
+
     const current = createMemo(() => {
       if (!configuredModel.ready()) return
 

packages/app/test-browser/fixtures/model-selection.ts

@@ -183,12 +183,28 @@ function selection(local: ReturnType<typeof useLocal>) {
   }
 }
 
-test("restores durable agents even when the agent selector is hidden", () => {
-  const f = fixture({ session: durable("b", "high", "plan") })
+test("hiding agents selects Build for the next prompt without changing the server session", () => {
+  const f = fixture({
+    session: durable("b", "high", "plan"),
+    agents: [agent("build", key("a")), agent("plan", key("b")), { ...agent("custom"), native: false }],
+  })
+
+  const first = f.mount()
+  expect(selection(first.local)).toEqual({ agent: "plan", model: "b", variant: "high" })
   f.set("visible", false)
-  const { local } = f.mount()
+  const { local } = first
   expect(local.agent.visible()).toBe(false)
-  expect(selection(local)).toEqual({ agent: "plan", model: "b", variant: "high" })
+  expect(selection(local)).toEqual({ agent: "build", model: "a", variant: undefined })
+  expect(f.state.sessions.ses_a?.agent).toBe("plan")
+  first.dispose()
+  const second = f.mount()
+  expect(selection(second.local)).toEqual({ agent: "build", model: "a", variant: undefined })
+  f.set("route", "id", undefined)
+  expect(second.local.agent.current()?.name).toBe("build")
+  f.set("visible", true)
+  expect(second.local.agent.visible()).toBe(true)
+  f.set("route", "id", "ses_a")
+  expect(second.local.agent.current()?.name).toBe("build")
 })
 
 test("waits for initial configuration and reloads it after reconnecting", () => {