Fork assistant turns into new drafts (#1788)

* feat(chat): fork assistant turns into new drafts

Builds chat-history attachments on the daemon and routes them into draft composers so users can continue an assistant turn in an existing workspace tab or New Workspace.

* fix(chat): clean up fork draft handling

* fix(chat): address fork draft review feedback

* fix(server): build fork context from bounded timeline

* fix(app): restore assistant turn footer in streams

* fix(app): preserve fork draft setup

* fix(app): tighten assistant fork footers

* fix(app): lock active fork draft handoff

* fix(app): preserve attachment-only draft retries

* fix(app): unify composer attachment scopes

* fix(app): align chat history attachment labels

* fix(app): centralize attachment pill content

* fix(app): trim fork context for workspace naming

packages/app/e2e/agent-stream-ui.spec.ts

@@ -9,6 +9,7 @@ import {
 import {
   expectScrollStaysFixed,
   readScrollMetrics,
+  scrollAgentChatToBottom,
   scrollChatAwayFromBottom,
   waitForScrollableChat,
 } from "./helpers/agent-bottom-anchor";
@@ -18,6 +19,8 @@ import { clickNewChat } from "./helpers/launcher";
 import { expectComposerVisible, startRunningMockAgent } from "./helpers/composer";
 import { openAgentRoute, seedMockAgentWorkspace } from "./helpers/mock-agent";
 
+const SCROLL_AWAY_MIN_SCROLLABLE_DISTANCE = 360;
+
 test.describe("Agent stream UI", () => {
   test("auto-scroll sticks to bottom across token bursts", async ({ page }) => {
     test.setTimeout(120_000);
@@ -54,7 +57,10 @@ test.describe("Agent stream UI", () => {
         timeout: 30_000,
       });
       await awaitAssistantMessage(page);
-      await waitForScrollableChat(page, { minScrollableDistance: 900, timeout: 30_000 });
+      await waitForScrollableChat(page, {
+        minScrollableDistance: SCROLL_AWAY_MIN_SCROLLABLE_DISTANCE,
+        timeout: 30_000,
+      });
       const baseline = await scrollChatAwayFromBottom(page, {
         deltaY: -900,
         minDistanceFromBottom: 300,
@@ -100,7 +106,10 @@ test.describe("Agent stream UI", () => {
       timeout: 30_000,
     });
     await awaitAssistantMessage(page);
-    await waitForScrollableChat(page, { minScrollableDistance: 900, timeout: 45_000 });
+    await waitForScrollableChat(page, {
+      minScrollableDistance: SCROLL_AWAY_MIN_SCROLLABLE_DISTANCE,
+      timeout: 45_000,
+    });
     const baseline = await scrollChatAwayFromBottom(page, {
       deltaY: -900,
       minDistanceFromBottom: 300,
@@ -122,6 +131,7 @@ test.describe("Agent stream UI", () => {
       await awaitAssistantMessage(page);
       await expectInlineWorkingIndicator(page);
       await expectAgentIdle(page, 30_000);
+      await scrollAgentChatToBottom(page);
       await expectTurnCopyButton(page);
     } finally {
       await agent.cleanup();

packages/app/e2e/assistant-fork-menu.spec.ts

@@ -0,0 +1,121 @@
+import { expect, test as base, type Page } from "./fixtures";
+import { scrollAgentChatToBottom } from "./helpers/agent-bottom-anchor";
+import { awaitAssistantMessage } from "./helpers/agent-stream";
+import { expectComposerVisible } from "./helpers/composer";
+import { getE2EDaemonPort } from "./helpers/daemon-port";
+import {
+  openAgentRoute,
+  seedMockAgentWorkspace,
+  type MockAgentOptions,
+  type MockAgentWorkspace,
+} from "./helpers/mock-agent";
+import { getServerId } from "./helpers/server-id";
+import { seedSavedSettingsHosts } from "./helpers/settings";
+
+const test = base.extend<{
+  seedForkWorkspace: (options: MockAgentOptions) => Promise<MockAgentWorkspace>;
+}>({
+  seedForkWorkspace: async ({ browserName: _browserName }, provide) => {
+    const sessions: MockAgentWorkspace[] = [];
+    await provide(async (options) => {
+      const session = await seedMockAgentWorkspace(options);
+      sessions.push(session);
+      return session;
+    });
+    await Promise.allSettled(sessions.map((session) => session.cleanup()));
+  },
+});
+
+async function openAssistantForkMenu(page: Page): Promise<void> {
+  await expect
+    .poll(
+      async () => {
+        await scrollAgentChatToBottom(page);
+        return page.getByTestId("assistant-fork-menu-trigger").count();
+      },
+      { timeout: 30_000 },
+    )
+    .toBeGreaterThan(0);
+  const trigger = page.getByTestId("assistant-fork-menu-trigger").last();
+  await expect(trigger).toBeVisible({ timeout: 30_000 });
+  await trigger.click();
+  await expect(page.getByTestId("assistant-fork-menu-content")).toBeVisible({
+    timeout: 10_000,
+  });
+}
+
+async function expectChatHistoryPill(page: Page): Promise<void> {
+  const pill = page.getByTestId("composer-chat-history-attachment-pill").first();
+  await expect(pill).toBeVisible({ timeout: 30_000 });
+  await expect(pill).toContainText("Chat history");
+}
+
+test.describe("Assistant fork menu", () => {
+  test.describe.configure({ timeout: 180_000 });
+
+  test("forks an assistant turn into a new workspace draft tab", async ({
+    page,
+    seedForkWorkspace,
+  }) => {
+    const session = await seedForkWorkspace({
+      repoPrefix: "assistant-fork-tab-",
+      title: "Assistant fork tab",
+      initialPrompt: "emit 1 coalesced agent stream updates for assistant fork tab.",
+      model: "ten-second-stream",
+    });
+
+    await openAgentRoute(page, session);
+    await expectComposerVisible(page);
+    await awaitAssistantMessage(page);
+    await session.client.waitForFinish(session.agentId, 45_000);
+
+    await openAssistantForkMenu(page);
+    await page.getByTestId("assistant-fork-menu-new-tab").click();
+
+    await expectChatHistoryPill(page);
+  });
+
+  test("forks an assistant turn into New Workspace and keeps the attachment across host changes", async ({
+    page,
+    seedForkWorkspace,
+  }) => {
+    await seedSavedSettingsHosts(page, [
+      {
+        serverId: getServerId(),
+        label: "localhost",
+        endpoint: `127.0.0.1:${getE2EDaemonPort()}`,
+      },
+      {
+        serverId: "secondary-assistant-fork-host",
+        label: "Secondary host",
+        // The host does not need to be reachable; this pins that the draft-scoped
+        // attachment survives changing the selected target host.
+        endpoint: "127.0.0.1:9",
+      },
+    ]);
+
+    const session = await seedForkWorkspace({
+      repoPrefix: "assistant-fork-workspace-",
+      title: "Assistant fork workspace",
+      initialPrompt: "emit 1 coalesced agent stream updates for assistant fork new workspace.",
+      model: "ten-second-stream",
+    });
+
+    await openAgentRoute(page, session);
+    await expectComposerVisible(page);
+    await awaitAssistantMessage(page);
+    await session.client.waitForFinish(session.agentId, 45_000);
+
+    await openAssistantForkMenu(page);
+    await page.getByTestId("assistant-fork-menu-new-workspace").click();
+
+    await expect(page).toHaveURL(/\/new\?.*draftId=/, { timeout: 30_000 });
+    await expectChatHistoryPill(page);
+
+    await page.getByTestId("host-picker-trigger").click();
+    await page
+      .getByTestId("new-workspace-host-picker-option-secondary-assistant-fork-host")
+      .click();
+    await expectChatHistoryPill(page);
+  });
+});

packages/app/e2e/helpers/agent-bottom-anchor.ts

@@ -55,6 +55,25 @@ export async function expectNearBottom(page: Page): Promise<void> {
     .toBeLessThanOrEqual(NEAR_BOTTOM_THRESHOLD_PX);
 }
 
+export async function scrollAgentChatToBottom(page: Page): Promise<void> {
+  const chatScroll = getVisibleChatScroll(page);
+  await chatScroll.evaluate((root: Element) => {
+    const scrollElement = root as HTMLElement;
+    scrollElement.scrollTop = scrollElement.scrollHeight;
+  });
+  await expect
+    .poll(async () =>
+      chatScroll.evaluate((root: Element) => {
+        const scrollElement = root as HTMLElement;
+        return Math.max(
+          0,
+          scrollElement.scrollHeight - (scrollElement.scrollTop + scrollElement.clientHeight),
+        );
+      }),
+    )
+    .toBeLessThanOrEqual(NEAR_BOTTOM_THRESHOLD_PX);
+}
+
 export async function waitForContentGrowth(
   page: Page,
   previousContentHeight: number,

packages/app/e2e/helpers/mock-agent.ts

@@ -1,7 +1,7 @@
 import type { Page } from "@playwright/test";
-import { buildHostWorkspaceRoute } from "../../src/utils/host-routes";
 import { seedWorkspace, type SeedDaemonClient } from "./seed-client";
 import { getServerId } from "./server-id";
+import { buildHostAgentDetailRoute } from "../../src/utils/host-routes";
 
 export interface MockAgentWorkspace {
   agentId: string;
@@ -54,9 +54,7 @@ export async function seedMockAgentWorkspace(
 }
 
 export function buildAgentRoute(workspaceId: string, agentId: string): string {
-  return `${buildHostWorkspaceRoute(getServerId(), workspaceId)}?open=${encodeURIComponent(
-    `agent:${agentId}`,
-  )}`;
+  return buildHostAgentDetailRoute(getServerId(), agentId, workspaceId);
 }
 
 /** Boots the app directly at the agent's workspace route and waits for the open intent to settle. */