Show workspace changes and stale notices in issue threads (#5356)

## Thinking Path

> - Paperclip orchestrates AI agents for zero-human companies
> - The issue thread is the operator's durable audit trail for what
changed and why
> - Workspace changes and stale disposition notices need to be visible
in that same timeline without noisy or misleading rendering
> - The local branch already contained backend activity details,
timeline conversion, and UI rendering work for those events
> - This pull request isolates the issue-thread activity work into a
standalone branch against `origin/master`
> - The benefit is a focused audit-trail PR that can merge independently
of the sidebar/operator UI polish branch

## What Changed

- Adds readable workspace-change activity details to issue update
activity events.
- Surfaces workspace-change events in issue chat/timeline rendering.
- Makes the existing issue comment migration idempotent.
- Folds and renders stale disposition notices inline so they match
activity-log styling and spacing.
- Adds focused route, timeline, and issue-thread system notice coverage.

## Verification

- `pnpm install --frozen-lockfile`
- `pnpm exec vitest run
server/src/__tests__/issue-activity-events-routes.test.ts
ui/src/lib/issue-timeline-events.test.ts
ui/src/components/IssueChatThreadSystemNotice.test.tsx` — 3 files
passed, 22 tests passed.
- Confirmed the PR changes 9 files and does not include `pnpm-lock.yaml`
or `.github/workflows/*`.
- `pnpm exec vitest run
server/src/__tests__/issue-closed-workspace-routes.test.ts` — 1 file
passed, 4 tests passed.
- `pnpm exec vitest run
server/src/__tests__/issue-activity-events-routes.test.ts
ui/src/lib/issue-timeline-events.test.ts
ui/src/components/IssueChatThreadSystemNotice.test.tsx
server/src/services/recovery/successful-run-handoff.test.ts
packages/shared/src/validators/issue.test.ts` — 5 files passed, 54 tests
passed.
- `pnpm --filter @paperclipai/shared typecheck && pnpm --filter
@paperclipai/server typecheck && pnpm --filter @paperclipai/ui
typecheck`.
- `pnpm --filter @paperclipai/ui typecheck` after adding the Storybook
screenshot fixture.
- Captured Storybook screenshots for the new UI rendering paths:
- Collapsed stale notice + workspace-change row:
`docs/pr-screenshots/pr-5356/issue-thread-notices-collapsed.png`
- Expanded stale notice details:
`docs/pr-screenshots/pr-5356/issue-thread-notices-expanded.png`


### Screenshots

Collapsed stale notice with workspace-change row:

![Collapsed stale notice with workspace-change
row](docs/pr-screenshots/pr-5356/issue-thread-notices-collapsed.png)

Expanded stale notice details:

![Expanded stale notice
details](docs/pr-screenshots/pr-5356/issue-thread-notices-expanded.png)

## Risks

- Moderate risk: this touches issue activity serialization and
issue-thread rendering, both of which are central operator surfaces.
- Migration risk is low: the only migration change makes an existing
migration idempotent.
- No new migrations are introduced, so there is no cross-PR migration
ordering requirement.

> For core feature work, check [`ROADMAP.md`](ROADMAP.md) first and
discuss it in `#dev` before opening the PR. Feature PRs that overlap
with planned core work may need to be redirected — check the roadmap
first. See `CONTRIBUTING.md`.

## Model Used

- OpenAI Codex, GPT-5 coding agent, shell/tool-use enabled, used to
split the existing branch, verify the isolated PR branch, and create
this PR.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] If this change affects the UI, I have included before/after
screenshots
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge

---------

Co-authored-by: Paperclip <noreply@paperclip.ing>

ui/src/lib/issue-chat-messages.ts

@@ -455,6 +455,11 @@ function createTimelineEventMessage(args: {
       : (formatAssigneeUserLabel(event.assigneeChange.to.userId, currentUserId, userLabelMap) ?? "Unassigned");
     lines.push(`Assignee: ${from} -> ${to}`);
   }
+  if (event.workspaceChange) {
+    lines.push(
+      `Workspace: ${event.workspaceChange.from.label ?? "none"} -> ${event.workspaceChange.to.label ?? "none"}`,
+    );
+  }
 
   const message: ThreadSystemMessage = {
     id: `activity:${event.id}`,
@@ -471,6 +476,7 @@ function createTimelineEventMessage(args: {
         actorId: event.actorId,
         statusChange: event.statusChange ?? null,
         assigneeChange: event.assigneeChange ?? null,
+        workspaceChange: event.workspaceChange ?? null,
         followUpRequested: event.followUpRequested === true,
       },
     },

ui/src/lib/issue-timeline-events.test.ts

@@ -171,6 +171,67 @@ describe("extractIssueTimelineEvents", () => {
     ]);
   });
 
+  it("extracts workspace changes from issue update activity", () => {
+    const events = extractIssueTimelineEvents([
+      {
+        id: "evt-workspace",
+        companyId: "company-1",
+        actorType: "user",
+        actorId: "local-board",
+        action: "issue.updated",
+        entityType: "issue",
+        entityId: "issue-1",
+        agentId: null,
+        runId: null,
+        createdAt: new Date("2026-03-31T12:01:00.000Z"),
+        details: {
+          projectWorkspaceId: "workspace-2",
+          workspaceChange: {
+            from: {
+              label: "Main workspace",
+              projectWorkspaceId: "workspace-1",
+              executionWorkspaceId: null,
+              mode: "shared_workspace",
+            },
+            to: {
+              label: "Feature branch",
+              projectWorkspaceId: "workspace-2",
+              executionWorkspaceId: null,
+              mode: "shared_workspace",
+            },
+          },
+          _previous: {
+            projectWorkspaceId: "workspace-1",
+          },
+        },
+      },
+    ] satisfies ActivityEvent[]);
+
+    expect(events).toEqual([
+      {
+        id: "evt-workspace",
+        createdAt: new Date("2026-03-31T12:01:00.000Z"),
+        actorType: "user",
+        actorId: "local-board",
+        runId: null,
+        workspaceChange: {
+          from: {
+            label: "Main workspace",
+            projectWorkspaceId: "workspace-1",
+            executionWorkspaceId: null,
+            mode: "shared_workspace",
+          },
+          to: {
+            label: "Feature branch",
+            projectWorkspaceId: "workspace-2",
+            executionWorkspaceId: null,
+            mode: "shared_workspace",
+          },
+        },
+      },
+    ]);
+  });
+
   it("synthesizes non-status follow-up rows from comment activity", () => {
     const events = extractIssueTimelineEvents([
       {
@@ -205,7 +266,7 @@ describe("extractIssueTimelineEvents", () => {
     ]);
   });
 
-  it("ignores issue updates without visible status or assignee transitions", () => {
+  it("ignores issue updates without visible status, assignee, or workspace transitions", () => {
     const events = extractIssueTimelineEvents([
       {
         id: "evt-title",

ui/src/lib/issue-timeline-events.ts

@@ -19,10 +19,26 @@ export interface IssueTimelineEvent {
     from: IssueTimelineAssignee;
     to: IssueTimelineAssignee;
   };
+  workspaceChange?: {
+    from: IssueTimelineWorkspace;
+    to: IssueTimelineWorkspace;
+  };
   commentId?: string | null;
   followUpRequested?: boolean;
 }
 
+export interface IssueTimelineWorkspace {
+  label: string | null;
+  projectWorkspaceId: string | null;
+  executionWorkspaceId: string | null;
+  mode: string | null;
+}
+
+export function formatTimelineWorkspaceLabel(workspace: IssueTimelineWorkspace) {
+  const fallbackId = workspace.executionWorkspaceId ?? workspace.projectWorkspaceId;
+  return workspace.label ?? (fallbackId ? fallbackId.slice(0, 8) : "None");
+}
+
 function asRecord(value: unknown): Record<string, unknown> | null {
   if (typeof value !== "object" || value === null || Array.isArray(value)) return null;
   return value as Record<string, unknown>;
@@ -44,6 +60,33 @@ function sameAssignee(left: IssueTimelineAssignee, right: IssueTimelineAssignee)
   return left.agentId === right.agentId && left.userId === right.userId;
 }
 
+function sameWorkspace(left: IssueTimelineWorkspace, right: IssueTimelineWorkspace) {
+  return left.projectWorkspaceId === right.projectWorkspaceId
+    && left.executionWorkspaceId === right.executionWorkspaceId
+    && left.mode === right.mode
+    && left.label === right.label;
+}
+
+function workspaceFromRecord(value: unknown): IssueTimelineWorkspace | null {
+  const record = asRecord(value);
+  if (!record) return null;
+  return {
+    label: nullableString(record.label),
+    projectWorkspaceId: nullableString(record.projectWorkspaceId),
+    executionWorkspaceId: nullableString(record.executionWorkspaceId),
+    mode: nullableString(record.mode),
+  };
+}
+
+function workspaceChangeFromDetails(details: Record<string, unknown>) {
+  const change = asRecord(details.workspaceChange);
+  if (!change) return null;
+  const from = workspaceFromRecord(change.from);
+  const to = workspaceFromRecord(change.to);
+  if (!from || !to || sameWorkspace(from, to)) return null;
+  return { from, to };
+}
+
 function sortTimelineEvents<T extends { createdAt: Date | string; id: string }>(events: T[]) {
   return [...events].sort((a, b) => {
     const createdAtDiff = toTimestamp(a.createdAt) - toTimestamp(b.createdAt);
@@ -120,7 +163,17 @@ export function extractIssueTimelineEvents(activity: ActivityEvent[] | null | un
       }
     }
 
-    if (timelineEvent.statusChange || timelineEvent.assigneeChange || timelineEvent.followUpRequested) {
+    const workspaceChange = workspaceChangeFromDetails(details);
+    if (workspaceChange) {
+      timelineEvent.workspaceChange = workspaceChange;
+    }
+
+    if (
+      timelineEvent.statusChange
+      || timelineEvent.assigneeChange
+      || timelineEvent.workspaceChange
+      || timelineEvent.followUpRequested
+    ) {
       events.push(timelineEvent);
     }
   }