feat(environments): add archive undo and continue in new thread

apps/app/src/components/promptbox/FollowUpPromptBox.stories.tsx

@@ -496,7 +496,7 @@ const archivedContextBannerElement: ReactNode = (
 const environmentGoneContextBannerElement: ReactNode = (
   <ThreadPromptContextBanner
     archivedSection={null}
-    environmentGoneSection={{ status: "destroyed" }}
+    environmentGoneSection={{ status: "destroyed", onHandoff: noop }}
     gitSection={null}
     gitSectionPending={false}
     parentThreadSection={null}

apps/app/src/components/promptbox/banner/ThreadPromptContextBanner.stories.tsx

@@ -646,10 +646,12 @@ const archivedFixture: ThreadPromptArchivedSection = {
 
 const destroyedEnvironmentFixture: ThreadPromptEnvironmentGoneSection = {
   status: "destroyed",
+  onHandoff: noop,
 };
 
 const destroyingEnvironmentFixture: ThreadPromptEnvironmentGoneSection = {
   status: "destroying",
+  onHandoff: noop,
 };
 
 export function Overview() {
@@ -689,14 +691,14 @@ export function Overview() {
         />
       </StoryRow>
       <StoryRow
-        label="environment destroyed"
-        hint="environment-gone row suppresses git/childThreads"
+        label="environment archived"
+        hint="archived-environment row suppresses git/childThreads"
       >
         <Row environmentGone={destroyedEnvironmentFixture} mergeBase={null} />
       </StoryRow>
       <StoryRow
-        label="environment destroying + child thread"
-        hint="environment-gone row plus parent context"
+        label="environment archiving + child thread"
+        hint="archiving-environment row plus parent context"
       >
         <Row
           environmentGone={destroyingEnvironmentFixture}
@@ -705,8 +707,8 @@ export function Overview() {
         />
       </StoryRow>
       <StoryRow
-        label="environment gone (with other context, all suppressed)"
-        hint="gone environment takes precedence — git/child work are hidden"
+        label="environment archived (with other context, all suppressed)"
+        hint="archived environment takes precedence — git/child work are hidden"
       >
         <Row
           environmentGone={destroyedEnvironmentFixture}

apps/app/src/components/promptbox/banner/ThreadPromptContextBanner.test.tsx

@@ -100,8 +100,9 @@ describe("ThreadPromptContextBanner", () => {
       />,
     );
 
-    expect(markup).toContain("Environment is unavailable");
-    expect(markup).toContain("This thread can't run any more work.");
+    expect(markup).toContain("Environment archived");
+    expect(markup).toContain("This environment has been archived.");
+    expect(markup).not.toContain("to keep working");
     expect(markup).toContain('role="status"');
     expect(markup).not.toContain("<button");
     expect(markup).not.toContain("Provision");
@@ -115,10 +116,10 @@ describe("ThreadPromptContextBanner", () => {
       expectedLabel: "Thread is archived",
     },
     {
-      label: "environment gone",
+      label: "environment archived",
       archivedSection: null,
       environmentGoneSection: { status: "destroyed" as const },
-      expectedLabel: "Environment is unavailable",
+      expectedLabel: "Environment archived",
     },
   ])(
     "keeps the $label read-only status visible in compact mode",
@@ -150,6 +151,88 @@ describe("ThreadPromptContextBanner", () => {
     },
   );
 
+  it("renders an enabled handoff action once the environment is destroyed", () => {
+    const markup = renderToStaticMarkup(
+      <ThreadPromptContextBanner
+        gitSection={null}
+        gitSectionPending={false}
+        archivedSection={null}
+        environmentGoneSection={{
+          status: "destroyed",
+          onHandoff: noop,
+        }}
+        parentThreadSection={null}
+        childThreadsSection={null}
+        pullRequestSection={null}
+        expandedSection={null}
+        onToggleSection={noop}
+      />,
+    );
+
+    expect(markup).toContain("Continue in new thread");
+    expect(markup).toContain(
+      "This environment has been archived. Continue in a new thread to keep working.",
+    );
+    expect(markup).toContain("<button");
+    expect(markup).not.toContain('disabled=""');
+  });
+
+  it("shows a disabled handoff action while the environment is destroying", () => {
+    const markup = renderToStaticMarkup(
+      <ThreadPromptContextBanner
+        gitSection={null}
+        gitSectionPending={false}
+        archivedSection={null}
+        environmentGoneSection={{
+          status: "destroying",
+          onHandoff: noop,
+        }}
+        parentThreadSection={null}
+        childThreadsSection={null}
+        pullRequestSection={null}
+        expandedSection={null}
+        onToggleSection={noop}
+      />,
+    );
+
+    expect(markup).toContain("Archiving environment...");
+    expect(markup).toContain("Continue in new thread");
+    expect(markup).toContain(
+      "This environment is being archived. Continue in a new thread when cleanup finishes.",
+    );
+    expect(markup).toContain('disabled=""');
+  });
+
+  it("prioritizes destroyed-environment handoff over unarchiving", () => {
+    const markup = renderToStaticMarkup(
+      <MemoryRouter>
+        <ThreadPromptContextBanner
+          gitSection={null}
+          gitSectionPending={false}
+          archivedSection={{
+            archivedAt: 1_731_456_000_000,
+            onUnarchive: noop,
+          }}
+          environmentGoneSection={{ status: "destroyed", onHandoff: noop }}
+          parentThreadSection={{
+            parentThreadTitle: "Parent thread",
+            href: "/threads/thr_parent",
+            relationship: "parent",
+          }}
+          childThreadsSection={null}
+          pullRequestSection={null}
+          expandedSection={null}
+          onToggleSection={noop}
+        />
+      </MemoryRouter>,
+    );
+
+    expect(markup).toContain("Environment archived");
+    expect(markup).toContain("Continue in new thread");
+    expect(markup).not.toContain("Thread is archived");
+    expect(markup).not.toContain(">Unarchive<");
+  });
+
   it("labels a standalone pull request without non-actionable attention text", () => {
     const markup = renderToStaticMarkup(
       <ThreadPromptContextBanner

apps/app/src/components/promptbox/banner/ThreadPromptContextBanner.tsx

@@ -118,6 +118,13 @@ export interface ThreadPromptArchivedSection {
  */
 export interface ThreadPromptEnvironmentGoneSection {
   status: Extract<EnvironmentStatus, "destroying" | "destroyed">;
+  /**
+   * Hands the surviving thread context off to a new thread. Enabled once the old
+   * environment is fully gone (`destroyed`); while `destroying` the action shows
+   * a disabled "Continue in new thread" state. Omitted when no safe environment
+   * target can be derived.
+   */
+  onHandoff?: () => void;
 }
 
 /**
@@ -193,9 +200,22 @@ const KIND_PREFIX: Record<WorkspaceChangedFilesSection["kind"], string> = {
 };
 
 const ARCHIVED_THREAD_STATUS_LABEL = "Thread is archived";
-const ENVIRONMENT_GONE_STATUS_LABEL = "Environment is unavailable";
-const ENVIRONMENT_GONE_ARIA_LABEL =
-  "Environment is unavailable. This thread can't run any more work.";
+const ENVIRONMENT_GONE_STATUS_COPY: Record<
+  ThreadPromptEnvironmentGoneSection["status"],
+  { ariaLabel: string; handoffInstruction: string; label: string }
+> = {
+  destroying: {
+    ariaLabel: "This environment is being archived.",
+    handoffInstruction:
+      "Continue in a new thread when cleanup finishes.",
+    label: "Archiving environment...",
+  },
+  destroyed: {
+    ariaLabel: "This environment has been archived.",
+    handoffInstruction: "Continue in a new thread to keep working.",
+    label: "Environment archived",
+  },
+};
 const PROMPT_BANNER_ACTION_FILL_CLASS = "bg-background shadow-xs";
 const PROMPT_BANNER_ACTION_INTERACTIVE_CLASS =
   "cursor-pointer text-muted-foreground transition-colors hover:bg-state-hover hover:text-foreground focus-visible:outline-none focus-visible:ring-1 focus-visible:ring-ring disabled:cursor-not-allowed disabled:opacity-60";
@@ -285,8 +305,7 @@ function SectionToggleButton({
         // icon — the icons' own internal padding provides enough separation,
         // and a gap here makes the pair look untethered.
         label !== null && label !== undefined ? "gap-1.5" : "gap-0",
-        !active &&
-          (isExpanded ? "text-foreground" : "text-muted-foreground"),
+        !active && (isExpanded ? "text-foreground" : "text-muted-foreground"),
       )}
     >
       {icon}
@@ -317,9 +336,7 @@ function SectionToggleButton({
       <Icon
         name="ChevronDown"
         className={cn(
-          active
-            ? activityIconClass("active")
-            : "text-subtle-foreground",
+          active ? activityIconClass("active") : "text-subtle-foreground",
           "size-3.5 shrink-0 transition-transform duration-200",
           isExpanded && "rotate-180",
         )}
@@ -526,6 +543,26 @@ function PullRequestReadyTextAction({
   );
 }
 
+function EnvironmentHandoffTextAction({
+  status,
+  onHandoff,
+}: {
+  status: Extract<EnvironmentStatus, "destroying" | "destroyed">;
+  onHandoff: () => void;
+}) {
+  const cleaningUp = status === "destroying";
+  return (
+    <button
+      type="button"
+      onClick={onHandoff}
+      disabled={cleaningUp}
+      className="rounded px-1 py-0.5 text-xs text-muted-foreground underline underline-offset-2 transition-colors hover:text-foreground focus-visible:outline-none focus-visible:ring-1 focus-visible:ring-ring disabled:cursor-not-allowed disabled:opacity-60"
+    >
+      Continue in new thread
+    </button>
+  );
+}
+
 const PULL_REQUEST_MERGE_ACTIONS: readonly {
   method: PullRequestMergeMethod;
   label: string;
@@ -771,8 +808,7 @@ function ReadOnlyContextBanner({
 }: ReadOnlyContextBannerProps) {
   const isParentThreadExpanded =
     expandedSection === "parentThread" && parentThreadSection !== null;
-  const hasMultipleSegments = parentThreadSection !== null;
-  const showStatusAction = statusAction !== null && !hasMultipleSegments;
+  const showStatusAction = statusAction !== null;
   return (
     <PromptStackCard
       ariaLabel="Thread context before sending"
@@ -815,10 +851,7 @@ function ReadOnlyContextBanner({
             className="size-3.5 shrink-0"
             aria-hidden="true"
           />
-          <span
-            className="min-w-0 truncate"
-            aria-hidden="true"
-          >
+          <span className="min-w-0 truncate" aria-hidden="true">
             {statusLabel}
           </span>
         </div>
@@ -863,21 +896,33 @@ export function ThreadPromptContextBanner({
   onToggleSection,
 }: ThreadPromptContextBannerProps) {
   if (archivedSection || environmentGoneSection) {
+    const environmentGone = environmentGoneSection !== null;
+    const environmentGoneCopy = environmentGoneSection
+      ? ENVIRONMENT_GONE_STATUS_COPY[environmentGoneSection.status]
+      : null;
+    const environmentGoneAriaLabel = environmentGoneCopy
+      ? `${environmentGoneCopy.ariaLabel}${
+          environmentGoneSection?.onHandoff
+            ? ` ${environmentGoneCopy.handoffInstruction}`
+            : ""
+        }`
+      : null;
     return (
       <ReadOnlyContextBanner
-        iconName={archivedSection ? "Archive" : "CircleX"}
+        iconName={environmentGone ? "CircleX" : "Archive"}
         statusAriaLabel={
-          archivedSection
-            ? ARCHIVED_THREAD_STATUS_LABEL
-            : ENVIRONMENT_GONE_ARIA_LABEL
+          environmentGoneAriaLabel ?? ARCHIVED_THREAD_STATUS_LABEL
         }
         statusLabel={
-          archivedSection
-            ? ARCHIVED_THREAD_STATUS_LABEL
-            : ENVIRONMENT_GONE_STATUS_LABEL
+          environmentGoneCopy?.label ?? ARCHIVED_THREAD_STATUS_LABEL
         }
         statusAction={
-          archivedSection?.onUnarchive ? (
+          environmentGoneSection?.onHandoff ? (
+            <EnvironmentHandoffTextAction
+              status={environmentGoneSection.status}
+              onHandoff={environmentGoneSection.onHandoff}
+            />
+          ) : archivedSection?.onUnarchive && !environmentGone ? (
             <ThreadUnarchiveTextAction
               isPending={archivedSection.unarchivePending}
               onUnarchive={archivedSection.onUnarchive}
@@ -974,8 +1019,7 @@ export function ThreadPromptContextBanner({
   // inline as "Parent <name>" with the name as a link. There's no other
   // context to compete for the row, so the icon-only toggle would be a strict
   // downgrade in legibility.
-  const isParentThreadOnly =
-    showParentThread && !showGit && !showPullRequest;
+  const isParentThreadOnly = showParentThread && !showGit && !showPullRequest;
 
   const pullRequest = pullRequestSection?.pullRequest ?? null;
   const showPullRequestLabel =