feat(app): better subagent experience

packages/app/e2e/session/session-child-navigation.spec.ts

@@ -1,7 +1,6 @@
 import { seedSessionTask, withSession } from "../actions"
 import { test, expect } from "../fixtures"
 import { inputMatch } from "../prompt/mock"
-import { promptSelector } from "../selectors"
 
 test("task tool child-session link does not trigger stale show errors", async ({ page, llm, project }) => {
   test.setTimeout(120_000)
@@ -30,15 +29,33 @@ test("task tool child-session link does not trigger stale show errors", async ({
 
       await project.gotoSession(session.id)
 
-      const link = page
-        .locator("a.subagent-link")
+      const header = page.locator("[data-session-title]")
+      await expect(header.getByRole("button", { name: "More options" })).toBeVisible({ timeout: 30_000 })
+
+      const card = page
+        .locator('[data-component="task-tool-card"]')
         .filter({ hasText: /open child session/i })
         .first()
-      await expect(link).toBeVisible({ timeout: 30_000 })
-      await link.click()
+      await expect(card).toBeVisible({ timeout: 30_000 })
+      await card.click()
 
       await expect(page).toHaveURL(new RegExp(`/session/${child.sessionID}(?:[/?#]|$)`), { timeout: 30_000 })
-      await expect(page.locator(promptSelector)).toBeVisible({ timeout: 30_000 })
+      await expect(header.locator('[data-slot="session-title-parent"]')).toHaveText(session.title)
+      await expect(header.locator('[data-slot="session-title-child"]')).toHaveText(taskInput.description)
+      await expect(header.locator('[data-slot="session-title-separator"]')).toHaveText("/")
+      await expect
+        .poll(
+          () =>
+            header.locator('[data-slot="session-title-separator"]').evaluate((el) => ({
+              left: getComputedStyle(el).paddingLeft,
+              right: getComputedStyle(el).paddingRight,
+            })),
+          { timeout: 30_000 },
+        )
+        .toEqual({ left: "8px", right: "8px" })
+      await expect(header.getByRole("button", { name: "More options" })).toHaveCount(0)
+      await expect(page.getByText("Subagent sessions cannot be prompted.")).toBeVisible({ timeout: 30_000 })
+      await expect(page.getByRole("button", { name: "Back to main session." })).toBeVisible({ timeout: 30_000 })
       await expect.poll(() => errs, { timeout: 5_000 }).toEqual([])
     })
   } finally {

packages/app/src/i18n/en.ts

@@ -238,6 +238,8 @@ export const dict = {
   "prompt.mode.shell": "Shell",
   "prompt.mode.normal": "Prompt",
   "prompt.mode.shell.exit": "esc to exit",
+  "session.child.promptDisabled": "Subagent sessions cannot be prompted.",
+  "session.child.backToParent": "Back to main session.",
 
   "prompt.example.1": "Fix a TODO in the codebase",
   "prompt.example.2": "What is the tech stack of this project?",

packages/app/src/index.css

@@ -1,6 +1,46 @@
 @import "@opencode-ai/ui/styles/tailwind";
 
 @layer components {
+  @keyframes session-progress-whip {
+    0% {
+      clip-path: inset(0 100% 0 0 round 999px);
+      animation-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1);
+    }
+
+    48% {
+      clip-path: inset(0 0 0 0 round 999px);
+      animation-timing-function: cubic-bezier(0.65, 0, 0.35, 1);
+    }
+
+    100% {
+      clip-path: inset(0 0 0 100% round 999px);
+    }
+  }
+
+  [data-component="session-progress"] {
+    position: absolute;
+    inset: 0 0 auto;
+    height: 2px;
+    overflow: hidden;
+    pointer-events: none;
+    opacity: 1;
+    transition: opacity 220ms ease-out;
+  }
+
+  [data-component="session-progress"][data-state="hiding"] {
+    opacity: 0;
+  }
+
+  [data-component="session-progress-bar"] {
+    width: 100%;
+    height: 100%;
+    border-radius: 999px;
+    background: var(--session-progress-color);
+    clip-path: inset(0 100% 0 0 round 999px);
+    animation: session-progress-whip var(--session-progress-ms, 1800ms) infinite;
+    will-change: clip-path;
+  }
+
   [data-component="getting-started"] {
     container-type: inline-size;
     container-name: getting-started;

packages/app/src/pages/layout.tsx

@@ -150,7 +150,6 @@ export default function Layout(props: ParentProps) {
   const [state, setState] = createStore({
     autoselect: !initialDirectory,
     busyWorkspaces: {} as Record<string, boolean>,
-    hoverSession: undefined as string | undefined,
     hoverProject: undefined as string | undefined,
     scrollSessionKey: undefined as string | undefined,
     nav: undefined as HTMLElement | undefined,
@@ -194,7 +193,6 @@ export default function Layout(props: ParentProps) {
     onActivate: (directory) => {
       globalSync.child(directory)
       setState("hoverProject", directory)
-      setState("hoverSession", undefined)
     },
   })
 
@@ -231,7 +229,6 @@ export default function Layout(props: ParentProps) {
     aim.reset()
   }
   const clearHoverProjectSoon = () => queueMicrotask(() => setHoverProject(undefined))
-  const setHoverSession = (id: string | undefined) => setState("hoverSession", id)
 
   const disarm = () => {
     if (navLeave.current === undefined) return
@@ -241,7 +238,6 @@ export default function Layout(props: ParentProps) {
 
   const reset = () => {
     disarm()
-    setState("hoverSession", undefined)
     setHoverProject(undefined)
   }
 
@@ -252,7 +248,6 @@ export default function Layout(props: ParentProps) {
     navLeave.current = window.setTimeout(() => {
       navLeave.current = undefined
       setHoverProject(undefined)
-      setState("hoverSession", undefined)
     }, 300)
   }
 
@@ -1972,9 +1967,6 @@ export default function Layout(props: ParentProps) {
     navList: currentSessions,
     sidebarExpanded,
     sidebarHovering,
-    nav: () => state.nav,
-    hoverSession: () => state.hoverSession,
-    setHoverSession,
     clearHoverProjectSoon,
     prefetchSession,
     archiveSession,
@@ -2003,7 +1995,6 @@ export default function Layout(props: ParentProps) {
     sidebarOpened: () => layout.sidebar.opened(),
     sidebarHovering,
     hoverProject: () => state.hoverProject,
-    nav: () => state.nav,
     onProjectMouseEnter: (worktree, event) => aim.enter(worktree, event),
     onProjectMouseLeave: (worktree) => aim.leave(worktree),
     onProjectFocus: (worktree) => aim.activate(worktree),
@@ -2022,15 +2013,10 @@ export default function Layout(props: ParentProps) {
     sessionProps: {
       navList: currentSessions,
       sidebarExpanded,
-      sidebarHovering,
-      nav: () => state.nav,
-      hoverSession: () => state.hoverSession,
-      setHoverSession,
       clearHoverProjectSoon,
       prefetchSession,
       archiveSession,
     },
-    setHoverSession,
   }
 
   const SidebarPanel = (panelProps: {
@@ -2041,7 +2027,6 @@ export default function Layout(props: ParentProps) {
     const project = panelProps.project
     const merged = createMemo(() => panelProps.mobile || (panelProps.merged ?? layout.sidebar.opened()))
     const hover = createMemo(() => !panelProps.mobile && panelProps.merged === false && !layout.sidebar.opened())
-    const popover = createMemo(() => !!panelProps.mobile || panelProps.merged === false || layout.sidebar.opened())
     const empty = createMemo(() => !params.dir && layout.projects.list().length === 0)
     const projectName = createMemo(() => {
       const item = project()
@@ -2243,7 +2228,6 @@ export default function Layout(props: ParentProps) {
                         project={project()!}
                         sortNow={sortNow}
                         mobile={panelProps.mobile}
-                        popover={popover()}
                       />
                     </div>
                   </>
@@ -2288,7 +2272,6 @@ export default function Layout(props: ParentProps) {
                                 project={project()!}
                                 sortNow={sortNow}
                                 mobile={panelProps.mobile}
-                                popover={popover()}
                               />
                             )}
                           </For>

packages/app/src/pages/layout/helpers.test.ts

@@ -8,6 +8,7 @@ import {
 } from "./deep-links"
 import { type Session } from "@opencode-ai/sdk/v2/client"
 import {
+  childSessionOnPath,
   displayName,
   effectiveWorkspaceOrder,
   errorMessage,
@@ -198,6 +199,19 @@ describe("layout workspace helpers", () => {
     expect(result?.id).toBe("root")
   })
 
+  test("finds the direct child on the active session path", () => {
+    const list = [
+      session({ id: "root", directory: "/workspace" }),
+      session({ id: "child", directory: "/workspace", parentID: "root" }),
+      session({ id: "leaf", directory: "/workspace", parentID: "child" }),
+    ]
+
+    expect(childSessionOnPath(list, "root", "leaf")?.id).toBe("child")
+    expect(childSessionOnPath(list, "child", "leaf")?.id).toBe("leaf")
+    expect(childSessionOnPath(list, "root", "root")).toBeUndefined()
+    expect(childSessionOnPath(list, "root", "other")).toBeUndefined()
+  })
+
   test("formats fallback project display name", () => {
     expect(displayName({ worktree: "/tmp/app" })).toBe("app")
     expect(displayName({ worktree: "/tmp/app", name: "My App" })).toBe("My App")

packages/app/src/pages/layout/helpers.ts

@@ -46,18 +46,17 @@ export function hasProjectPermissions<T>(
   return Object.values(request ?? {}).some((list) => list?.some(include))
 }
 
-export const childMapByParent = (sessions: Session[] | undefined) => {
-  const map = new Map<string, string[]>()
-  for (const session of sessions ?? []) {
-    if (!session.parentID) continue
-    const existing = map.get(session.parentID)
-    if (existing) {
-      existing.push(session.id)
-      continue
-    }
-    map.set(session.parentID, [session.id])
+export const childSessionOnPath = (sessions: Session[] | undefined, rootID: string, activeID?: string) => {
+  if (!activeID || activeID === rootID) return
+  const map = new Map((sessions ?? []).map((session) => [session.id, session]))
+  let id = activeID
+
+  while (id) {
+    const session = map.get(id)
+    if (!session?.parentID) return
+    if (session.parentID === rootID) return session
+    id = session.parentID
   }
-  return map
 }
 
 export const displayName = (project: { name?: string; worktree: string }) =>