Default sub-issue assignees from parent issues

ui/src/components/IssuesList.tsx

@@ -53,6 +53,7 @@ import { Collapsible, CollapsibleTrigger, CollapsibleContent } from "@/component
 import { CircleDot, Plus, ArrowUpDown, Layers, Check, ChevronRight, List, Columns3, User, Search } from "lucide-react";
 import { KanbanBoard } from "./KanbanBoard";
 import { buildIssueTree, countDescendants } from "../lib/issue-tree";
+import { buildSubIssueDefaults } from "../lib/subIssueDefaults";
 import type { Issue, Project } from "@paperclipai/shared";
 const ISSUE_SEARCH_DEBOUNCE_MS = 150;
 
@@ -494,11 +495,13 @@ export function IssuesList({
         else defaults.assigneeAgentId = groupKey;
       }
       else if (viewState.groupBy === "parent" && groupKey !== "__no_parent") {
-        defaults.parentId = groupKey;
+        const parentIssue = issueById.get(groupKey);
+        if (parentIssue) Object.assign(defaults, buildSubIssueDefaults(parentIssue));
+        else defaults.parentId = groupKey;
       }
     }
     return defaults;
-  }, [projectId, viewState.groupBy]);
+  }, [issueById, projectId, viewState.groupBy]);
 
   const filterToWorkspace = useCallback((workspaceId: string) => {
     updateView({ workspaces: [workspaceId] });

ui/src/components/NewIssueDialog.test.tsx

@@ -372,6 +372,43 @@ describe("NewIssueDialog", () => {
     act(() => root.unmount());
   });
 
+  it("submits the parent assignee when a sub-issue opens with inherited defaults", async () => {
+    dialogState.newIssueDefaults = {
+      parentId: "issue-1",
+      parentIdentifier: "PAP-1",
+      parentTitle: "Parent issue",
+      title: "Child issue",
+      projectId: "project-1",
+      goalId: "goal-1",
+      assigneeAgentId: "agent-1",
+    };
+
+    const { root } = renderDialog(container);
+    await flush();
+
+    const submitButton = Array.from(container.querySelectorAll("button"))
+      .find((button) => button.textContent?.includes("Create Sub-Issue"));
+    expect(submitButton).not.toBeUndefined();
+
+    await act(async () => {
+      submitButton!.dispatchEvent(new MouseEvent("click", { bubbles: true }));
+    });
+    await flush();
+
+    expect(mockIssuesApi.create).toHaveBeenCalledWith(
+      "company-1",
+      expect.objectContaining({
+        title: "Child issue",
+        parentId: "issue-1",
+        goalId: "goal-1",
+        projectId: "project-1",
+        assigneeAgentId: "agent-1",
+      }),
+    );
+
+    act(() => root.unmount());
+  });
+
   it("keeps the mobile dialog bounded with an internal flexible scroll region", async () => {
     const { root } = renderDialog(container);
     await flush();

ui/src/lib/subIssueDefaults.test.ts

@@ -0,0 +1,117 @@
+import { describe, expect, it } from "vitest";
+import type { ExecutionWorkspace, Issue } from "@paperclipai/shared";
+import { buildSubIssueDefaults } from "./subIssueDefaults";
+
+function makeExecutionWorkspace(overrides: Partial<ExecutionWorkspace> = {}): ExecutionWorkspace {
+  return {
+    id: "workspace-1",
+    companyId: "company-1",
+    projectId: "project-1",
+    projectWorkspaceId: "project-workspace-1",
+    sourceIssueId: null,
+    status: "active",
+    mode: "isolated_workspace",
+    strategyType: "git_worktree",
+    name: "Parent workspace",
+    cwd: "/tmp/workspace-1",
+    repoUrl: null,
+    baseRef: null,
+    branchName: "feature/pap-1",
+    providerType: "git_worktree",
+    providerRef: null,
+    derivedFromExecutionWorkspaceId: null,
+    openedAt: new Date("2026-04-07T00:00:00.000Z"),
+    closedAt: null,
+    cleanupEligibleAt: null,
+    cleanupReason: null,
+    config: null,
+    metadata: null,
+    lastUsedAt: new Date("2026-04-07T00:00:00.000Z"),
+    createdAt: new Date("2026-04-07T00:00:00.000Z"),
+    updatedAt: new Date("2026-04-07T00:00:00.000Z"),
+    ...overrides,
+  };
+}
+
+function makeIssue(overrides: Partial<Issue> = {}): Issue {
+  return {
+    id: "issue-1",
+    identifier: "PAP-1",
+    companyId: "company-1",
+    projectId: "project-1",
+    projectWorkspaceId: "project-workspace-1",
+    goalId: "goal-1",
+    parentId: null,
+    title: "Parent issue",
+    description: null,
+    status: "todo",
+    priority: "medium",
+    assigneeAgentId: null,
+    assigneeUserId: null,
+    checkoutRunId: null,
+    executionRunId: null,
+    executionAgentNameKey: null,
+    executionLockedAt: null,
+    createdByAgentId: null,
+    createdByUserId: null,
+    issueNumber: 1,
+    requestDepth: 0,
+    billingCode: null,
+    assigneeAdapterOverrides: null,
+    executionWorkspaceId: null,
+    executionWorkspacePreference: "shared_workspace",
+    executionWorkspaceSettings: null,
+    currentExecutionWorkspace: null,
+    startedAt: null,
+    completedAt: null,
+    cancelledAt: null,
+    hiddenAt: null,
+    createdAt: new Date("2026-04-07T00:00:00.000Z"),
+    updatedAt: new Date("2026-04-07T00:00:00.000Z"),
+    ...overrides,
+  };
+}
+
+describe("buildSubIssueDefaults", () => {
+  it("inherits the parent agent assignee and workspace context", () => {
+    const defaults = buildSubIssueDefaults(
+      makeIssue({
+        assigneeAgentId: "agent-1",
+        executionWorkspaceId: "workspace-1",
+        currentExecutionWorkspace: makeExecutionWorkspace(),
+      }),
+    );
+
+    expect(defaults).toEqual({
+      parentId: "issue-1",
+      parentIdentifier: "PAP-1",
+      parentTitle: "Parent issue",
+      projectId: "project-1",
+      projectWorkspaceId: "project-workspace-1",
+      goalId: "goal-1",
+      executionWorkspaceId: "workspace-1",
+      executionWorkspaceMode: "reuse_existing",
+      parentExecutionWorkspaceLabel: "Parent workspace",
+      assigneeAgentId: "agent-1",
+    });
+  });
+
+  it("inherits a user assignee when the parent is assigned to a user", () => {
+    const defaults = buildSubIssueDefaults(
+      makeIssue({
+        assigneeUserId: "user-1",
+      }),
+    );
+
+    expect(defaults).toEqual({
+      parentId: "issue-1",
+      parentIdentifier: "PAP-1",
+      parentTitle: "Parent issue",
+      projectId: "project-1",
+      projectWorkspaceId: "project-workspace-1",
+      goalId: "goal-1",
+      executionWorkspaceMode: "shared_workspace",
+      assigneeUserId: "user-1",
+    });
+  });
+});

ui/src/lib/subIssueDefaults.ts

@@ -0,0 +1,43 @@
+import type { Issue } from "@paperclipai/shared";
+
+type SubIssueDefaultSource = Pick<
+  Issue,
+  | "id"
+  | "identifier"
+  | "title"
+  | "projectId"
+  | "projectWorkspaceId"
+  | "goalId"
+  | "executionWorkspaceId"
+  | "executionWorkspacePreference"
+  | "currentExecutionWorkspace"
+  | "assigneeAgentId"
+  | "assigneeUserId"
+>;
+
+export function buildSubIssueDefaults(issue: SubIssueDefaultSource) {
+  const parentExecutionWorkspaceLabel =
+    issue.currentExecutionWorkspace?.name
+    ?? issue.currentExecutionWorkspace?.branchName
+    ?? issue.currentExecutionWorkspace?.cwd
+    ?? issue.executionWorkspaceId
+    ?? null;
+
+  return {
+    parentId: issue.id,
+    parentIdentifier: issue.identifier ?? undefined,
+    parentTitle: issue.title,
+    ...(issue.projectId ? { projectId: issue.projectId } : {}),
+    ...(issue.projectWorkspaceId ? { projectWorkspaceId: issue.projectWorkspaceId } : {}),
+    ...(issue.goalId ? { goalId: issue.goalId } : {}),
+    ...(issue.executionWorkspaceId ? { executionWorkspaceId: issue.executionWorkspaceId } : {}),
+    ...(issue.executionWorkspaceId
+      ? { executionWorkspaceMode: "reuse_existing" }
+      : issue.executionWorkspacePreference
+        ? { executionWorkspaceMode: issue.executionWorkspacePreference }
+        : {}),
+    ...(parentExecutionWorkspaceLabel ? { parentExecutionWorkspaceLabel } : {}),
+    ...(issue.assigneeAgentId ? { assigneeAgentId: issue.assigneeAgentId } : {}),
+    ...(issue.assigneeUserId ? { assigneeUserId: issue.assigneeUserId } : {}),
+  };
+}

ui/src/pages/IssueDetail.tsx

@@ -78,6 +78,7 @@ import { Tabs, TabsContent, TabsList, TabsTrigger } from "@/components/ui/tabs";
 import { formatIssueActivityAction } from "@/lib/activity-format";
 import { buildIssuePropertiesPanelKey } from "../lib/issue-properties-panel-key";
 import { resolveIssueChatTranscriptRuns } from "../lib/issueChatTranscriptRuns";
+import { buildSubIssueDefaults } from "../lib/subIssueDefaults";
 import {
   Activity as ActivityIcon,
   Archive,
@@ -749,34 +750,9 @@ export function IssueDetail() {
   );
   const openNewSubIssue = useCallback(() => {
     if (!issue) return;
-    openNewIssue({
-      parentId: issue.id,
-      parentIdentifier: issue.identifier ?? undefined,
-      parentTitle: issue.title,
-      projectId: issue.projectId ?? undefined,
-      projectWorkspaceId: issue.projectWorkspaceId ?? undefined,
-      goalId: issue.goalId ?? undefined,
-      executionWorkspaceId: issue.executionWorkspaceId ?? undefined,
-      executionWorkspaceMode: issue.executionWorkspaceId ? "reuse_existing" : issue.executionWorkspacePreference ?? undefined,
-      parentExecutionWorkspaceLabel:
-        issue.currentExecutionWorkspace?.name
-          ?? issue.currentExecutionWorkspace?.branchName
-          ?? issue.currentExecutionWorkspace?.cwd
-          ?? issue.executionWorkspaceId
-          ?? undefined,
-    });
+    openNewIssue(buildSubIssueDefaults(issue));
   }, [
-    issue?.currentExecutionWorkspace?.branchName,
-    issue?.currentExecutionWorkspace?.cwd,
-    issue?.currentExecutionWorkspace?.name,
-    issue?.executionWorkspaceId,
-    issue?.executionWorkspacePreference,
-    issue?.goalId,
-    issue?.id,
-    issue?.identifier,
-    issue?.projectId,
-    issue?.projectWorkspaceId,
-    issue?.title,
+    issue,
     openNewIssue,
   ]);