diff --git a/ui/src/components/IssueProperties.test.tsx b/ui/src/components/IssueProperties.test.tsx
new file mode 100644
index 00000000..4c3a4f72
--- /dev/null
+++ b/ui/src/components/IssueProperties.test.tsx
@@ -0,0 +1,204 @@
+// @vitest-environment jsdom
+
+import { act } from "react";
+import type { ComponentProps, ReactNode } from "react";
+import { createRoot } from "react-dom/client";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+import type { Issue } from "@paperclipai/shared";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { IssueProperties } from "./IssueProperties";
+
+const mockAgentsApi = vi.hoisted(() => ({
+  list: vi.fn(),
+}));
+
+const mockProjectsApi = vi.hoisted(() => ({
+  list: vi.fn(),
+}));
+
+const mockIssuesApi = vi.hoisted(() => ({
+  listLabels: vi.fn(),
+}));
+
+const mockAuthApi = vi.hoisted(() => ({
+  getSession: vi.fn(),
+}));
+
+vi.mock("../context/CompanyContext", () => ({
+  useCompany: () => ({
+    selectedCompanyId: "company-1",
+  }),
+}));
+
+vi.mock("../api/agents", () => ({
+  agentsApi: mockAgentsApi,
+}));
+
+vi.mock("../api/projects", () => ({
+  projectsApi: mockProjectsApi,
+}));
+
+vi.mock("../api/issues", () => ({
+  issuesApi: mockIssuesApi,
+}));
+
+vi.mock("../api/auth", () => ({
+  authApi: mockAuthApi,
+}));
+
+vi.mock("../hooks/useProjectOrder", () => ({
+  useProjectOrder: ({ projects }: { projects: unknown[] }) => ({
+    orderedProjects: projects,
+  }),
+}));
+
+vi.mock("../lib/recent-assignees", () => ({
+  getRecentAssigneeIds: () => [],
+  sortAgentsByRecency: (agents: unknown[]) => agents,
+  trackRecentAssignee: vi.fn(),
+}));
+
+vi.mock("../lib/assignees", () => ({
+  formatAssigneeUserLabel: () => "Me",
+}));
+
+vi.mock("./StatusIcon", () => ({
+  StatusIcon: ({ status }: { status: string }) => <span>{status}</span>,
+}));
+
+vi.mock("./PriorityIcon", () => ({
+  PriorityIcon: ({ priority }: { priority: string }) => <span>{priority}</span>,
+}));
+
+vi.mock("./Identity", () => ({
+  Identity: ({ name }: { name: string }) => <span>{name}</span>,
+}));
+
+vi.mock("./AgentIconPicker", () => ({
+  AgentIcon: () => null,
+}));
+
+vi.mock("@/lib/router", () => ({
+  Link: ({ children, to, ...props }: { children: ReactNode; to: string } & ComponentProps<"a">) => <a href={to} {...props}>{children}</a>,
+}));
+
+vi.mock("@/components/ui/separator", () => ({
+  Separator: () => <hr />,
+}));
+
+vi.mock("@/components/ui/popover", () => ({
+  Popover: ({ children }: { children: ReactNode }) => <div>{children}</div>,
+  PopoverTrigger: ({ children }: { children: ReactNode }) => <>{children}</>,
+  PopoverContent: ({ children }: { children: ReactNode }) => <div>{children}</div>,
+}));
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+(globalThis as any).IS_REACT_ACT_ENVIRONMENT = true;
+
+async function flush() {
+  await act(async () => {
+    await new Promise((resolve) => setTimeout(resolve, 0));
+  });
+}
+
+function createIssue(overrides: Partial<Issue> = {}): Issue {
+  return {
+    id: "issue-1",
+    companyId: "company-1",
+    projectId: null,
+    projectWorkspaceId: null,
+    goalId: null,
+    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: "user-1",
+    issueNumber: 1,
+    identifier: "PAP-1",
+    requestDepth: 0,
+    billingCode: null,
+    assigneeAdapterOverrides: null,
+    executionWorkspaceId: null,
+    executionWorkspacePreference: null,
+    executionWorkspaceSettings: null,
+    startedAt: null,
+    completedAt: null,
+    cancelledAt: null,
+    hiddenAt: null,
+    labels: [],
+    labelIds: [],
+    blockedBy: [],
+    blocks: [],
+    createdAt: new Date("2026-04-06T12:00:00.000Z"),
+    updatedAt: new Date("2026-04-06T12:05:00.000Z"),
+    ...overrides,
+  };
+}
+
+function renderProperties(container: HTMLDivElement, props: ComponentProps<typeof IssueProperties>) {
+  const queryClient = new QueryClient({
+    defaultOptions: {
+      queries: { retry: false },
+    },
+  });
+  const root = createRoot(container);
+  act(() => {
+    root.render(
+      <QueryClientProvider client={queryClient}>
+        <IssueProperties {...props} />
+      </QueryClientProvider>,
+    );
+  });
+  return root;
+}
+
+describe("IssueProperties", () => {
+  let container: HTMLDivElement;
+
+  beforeEach(() => {
+    container = document.createElement("div");
+    document.body.appendChild(container);
+    mockAgentsApi.list.mockResolvedValue([]);
+    mockProjectsApi.list.mockResolvedValue([]);
+    mockIssuesApi.listLabels.mockResolvedValue([]);
+    mockAuthApi.getSession.mockResolvedValue({ user: { id: "user-1" } });
+  });
+
+  afterEach(() => {
+    document.body.innerHTML = "";
+  });
+
+  it("always exposes the add sub-issue action", async () => {
+    const onAddSubIssue = vi.fn();
+    const root = renderProperties(container, {
+      issue: createIssue(),
+      childIssues: [],
+      onAddSubIssue,
+      onUpdate: vi.fn(),
+    });
+    await flush();
+
+    expect(container.textContent).toContain("Sub-issues");
+    expect(container.textContent).toContain("Add sub-issue");
+
+    const addButton = Array.from(container.querySelectorAll("button"))
+      .find((button) => button.textContent?.includes("Add sub-issue"));
+    expect(addButton).not.toBeUndefined();
+
+    await act(async () => {
+      addButton!.dispatchEvent(new MouseEvent("click", { bubbles: true }));
+    });
+
+    expect(onAddSubIssue).toHaveBeenCalledTimes(1);
+
+    act(() => root.unmount());
+  });
+});
diff --git a/ui/src/components/IssueProperties.tsx b/ui/src/components/IssueProperties.tsx
index 6c204eab..397f930c 100644
--- a/ui/src/components/IssueProperties.tsx
+++ b/ui/src/components/IssueProperties.tsx
@@ -72,6 +72,8 @@ function defaultExecutionWorkspaceModeForProject(project: { executionWorkspacePo
 
 interface IssuePropertiesProps {
   issue: Issue;
+  childIssues?: Issue[];
+  onAddSubIssue?: () => void;
   onUpdate: (data: Record<string, unknown>) => void;
   inline?: boolean;
 }
@@ -147,7 +149,13 @@ function PropertyPicker({
   );
 }
 
-export function IssueProperties({ issue, onUpdate, inline }: IssuePropertiesProps) {
+export function IssueProperties({
+  issue,
+  childIssues = [],
+  onAddSubIssue,
+  onUpdate,
+  inline,
+}: IssuePropertiesProps) {
   const { selectedCompanyId } = useCompany();
   const queryClient = useQueryClient();
   const companyId = issue.companyId ?? selectedCompanyId;
@@ -713,6 +721,34 @@ export function IssueProperties({ issue, onUpdate, inline }: IssuePropertiesProp
           )}
         </PropertyRow>
 
+        <PropertyRow label="Sub-issues">
+          <div className="flex flex-wrap items-center gap-1.5">
+            {childIssues.length > 0 ? (
+              childIssues.map((child) => (
+                <Link
+                  key={child.id}
+                  to={`/issues/${child.identifier ?? child.id}`}
+                  className="inline-flex items-center rounded-full border border-border px-2 py-0.5 text-xs hover:bg-accent/50"
+                >
+                  {child.identifier ?? child.title}
+                </Link>
+              ))
+            ) : (
+              <span className="text-sm text-muted-foreground">None</span>
+            )}
+            {onAddSubIssue ? (
+              <button
+                type="button"
+                className="inline-flex items-center gap-1 rounded-full border border-border px-2 py-0.5 text-xs text-muted-foreground transition-colors hover:bg-accent/50 hover:text-foreground"
+                onClick={onAddSubIssue}
+              >
+                <Plus className="h-3 w-3" />
+                Add sub-issue
+              </button>
+            ) : null}
+          </div>
+        </PropertyRow>
+
         {issue.parentId && (
           <PropertyRow label="Parent">
             <Link
diff --git a/ui/src/components/NewIssueDialog.test.tsx b/ui/src/components/NewIssueDialog.test.tsx
new file mode 100644
index 00000000..149dd438
--- /dev/null
+++ b/ui/src/components/NewIssueDialog.test.tsx
@@ -0,0 +1,348 @@
+// @vitest-environment jsdom
+
+import { act } from "react";
+import type { ComponentProps, ReactNode } from "react";
+import { createRoot } from "react-dom/client";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { NewIssueDialog } from "./NewIssueDialog";
+
+const dialogState = vi.hoisted(() => ({
+  newIssueOpen: true,
+  newIssueDefaults: {} as Record<string, unknown>,
+  closeNewIssue: vi.fn(),
+}));
+
+const companyState = vi.hoisted(() => ({
+  companies: [
+    {
+      id: "company-1",
+      name: "Paperclip",
+      status: "active",
+      brandColor: "#123456",
+      issuePrefix: "PAP",
+    },
+  ],
+  selectedCompanyId: "company-1",
+  selectedCompany: {
+    id: "company-1",
+    name: "Paperclip",
+    status: "active",
+    brandColor: "#123456",
+    issuePrefix: "PAP",
+  },
+}));
+
+const toastState = vi.hoisted(() => ({
+  pushToast: vi.fn(),
+}));
+
+const mockIssuesApi = vi.hoisted(() => ({
+  create: vi.fn(),
+  upsertDocument: vi.fn(),
+  uploadAttachment: vi.fn(),
+}));
+
+const mockExecutionWorkspacesApi = vi.hoisted(() => ({
+  list: vi.fn(),
+}));
+
+const mockProjectsApi = vi.hoisted(() => ({
+  list: vi.fn(),
+}));
+
+const mockAgentsApi = vi.hoisted(() => ({
+  list: vi.fn(),
+  adapterModels: vi.fn(),
+}));
+
+const mockAuthApi = vi.hoisted(() => ({
+  getSession: vi.fn(),
+}));
+
+const mockAssetsApi = vi.hoisted(() => ({
+  uploadImage: vi.fn(),
+}));
+
+const mockInstanceSettingsApi = vi.hoisted(() => ({
+  getExperimental: vi.fn(),
+}));
+
+vi.mock("../context/DialogContext", () => ({
+  useDialog: () => dialogState,
+}));
+
+vi.mock("../context/CompanyContext", () => ({
+  useCompany: () => companyState,
+}));
+
+vi.mock("../context/ToastContext", () => ({
+  useToast: () => toastState,
+}));
+
+vi.mock("../api/issues", () => ({
+  issuesApi: mockIssuesApi,
+}));
+
+vi.mock("../api/execution-workspaces", () => ({
+  executionWorkspacesApi: mockExecutionWorkspacesApi,
+}));
+
+vi.mock("../api/projects", () => ({
+  projectsApi: mockProjectsApi,
+}));
+
+vi.mock("../api/agents", () => ({
+  agentsApi: mockAgentsApi,
+}));
+
+vi.mock("../api/auth", () => ({
+  authApi: mockAuthApi,
+}));
+
+vi.mock("../api/assets", () => ({
+  assetsApi: mockAssetsApi,
+}));
+
+vi.mock("../api/instanceSettings", () => ({
+  instanceSettingsApi: mockInstanceSettingsApi,
+}));
+
+vi.mock("../hooks/useProjectOrder", () => ({
+  useProjectOrder: ({ projects }: { projects: unknown[] }) => ({
+    orderedProjects: projects,
+  }),
+}));
+
+vi.mock("../lib/recent-assignees", () => ({
+  getRecentAssigneeIds: () => [],
+  sortAgentsByRecency: (agents: unknown[]) => agents,
+  trackRecentAssignee: vi.fn(),
+}));
+
+vi.mock("../lib/assignees", () => ({
+  assigneeValueFromSelection: ({
+    assigneeAgentId,
+    assigneeUserId,
+  }: {
+    assigneeAgentId?: string;
+    assigneeUserId?: string;
+  }) => assigneeAgentId ? `agent:${assigneeAgentId}` : assigneeUserId ? `user:${assigneeUserId}` : "",
+  currentUserAssigneeOption: () => [],
+  parseAssigneeValue: (value: string) => ({
+    assigneeAgentId: value.startsWith("agent:") ? value.slice("agent:".length) : null,
+    assigneeUserId: value.startsWith("user:") ? value.slice("user:".length) : null,
+  }),
+}));
+
+vi.mock("./MarkdownEditor", async () => {
+  const React = await import("react");
+  return {
+    MarkdownEditor: React.forwardRef<
+      { focus: () => void },
+      { value: string; onChange?: (value: string) => void; placeholder?: string }
+    >(function MarkdownEditorMock({ value, onChange, placeholder }, ref) {
+      React.useImperativeHandle(ref, () => ({
+        focus: () => undefined,
+      }));
+      return (
+        <textarea
+          aria-label={placeholder ?? "Description"}
+          value={value}
+          onChange={(event) => onChange?.(event.target.value)}
+        />
+      );
+    }),
+  };
+});
+
+vi.mock("./InlineEntitySelector", async () => {
+  const React = await import("react");
+  return {
+    InlineEntitySelector: React.forwardRef<
+      HTMLButtonElement,
+      {
+        value: string;
+        placeholder?: string;
+        renderTriggerValue?: (option: { id: string; label: string } | null) => ReactNode;
+      }
+    >(function InlineEntitySelectorMock({ value, placeholder, renderTriggerValue }, ref) {
+      return (
+        <button ref={ref} type="button">
+          {(renderTriggerValue?.(value ? { id: value, label: value } : null) ?? value) || placeholder}
+        </button>
+      );
+    }),
+  };
+});
+
+vi.mock("./AgentIconPicker", () => ({
+  AgentIcon: () => null,
+}));
+
+vi.mock("@/components/ui/dialog", () => ({
+  Dialog: ({ open, children }: { open: boolean; children: ReactNode }) => (open ? <div>{children}</div> : null),
+  DialogContent: ({
+    children,
+    showCloseButton: _showCloseButton,
+    onEscapeKeyDown: _onEscapeKeyDown,
+    onPointerDownOutside: _onPointerDownOutside,
+    ...props
+  }: ComponentProps<"div"> & {
+    showCloseButton?: boolean;
+    onEscapeKeyDown?: (event: unknown) => void;
+    onPointerDownOutside?: (event: unknown) => void;
+  }) => <div {...props}>{children}</div>,
+}));
+
+vi.mock("@/components/ui/button", () => ({
+  Button: ({ children, onClick, type = "button", ...props }: ComponentProps<"button">) => (
+    <button type={type} onClick={onClick} {...props}>{children}</button>
+  ),
+}));
+
+vi.mock("@/components/ui/toggle-switch", () => ({
+  ToggleSwitch: ({ checked, onCheckedChange }: { checked: boolean; onCheckedChange: () => void }) => (
+    <button type="button" aria-pressed={checked} onClick={onCheckedChange}>toggle</button>
+  ),
+}));
+
+vi.mock("@/components/ui/popover", () => ({
+  Popover: ({ children }: { children: ReactNode }) => <div>{children}</div>,
+  PopoverTrigger: ({ children }: { children: ReactNode }) => <>{children}</>,
+  PopoverContent: ({ children }: { children: ReactNode }) => <div>{children}</div>,
+}));
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+(globalThis as any).IS_REACT_ACT_ENVIRONMENT = true;
+
+async function flush() {
+  await act(async () => {
+    await new Promise((resolve) => setTimeout(resolve, 0));
+  });
+}
+
+function renderDialog(container: HTMLDivElement) {
+  const queryClient = new QueryClient({
+    defaultOptions: {
+      queries: { retry: false },
+      mutations: { retry: false },
+    },
+  });
+  const root = createRoot(container);
+  act(() => {
+    root.render(
+      <QueryClientProvider client={queryClient}>
+        <NewIssueDialog />
+      </QueryClientProvider>,
+    );
+  });
+  return { root, queryClient };
+}
+
+describe("NewIssueDialog", () => {
+  let container: HTMLDivElement;
+
+  beforeEach(() => {
+    container = document.createElement("div");
+    document.body.appendChild(container);
+    dialogState.newIssueOpen = true;
+    dialogState.newIssueDefaults = {};
+    dialogState.closeNewIssue.mockReset();
+    toastState.pushToast.mockReset();
+    mockIssuesApi.create.mockReset();
+    mockIssuesApi.upsertDocument.mockReset();
+    mockIssuesApi.uploadAttachment.mockReset();
+    mockExecutionWorkspacesApi.list.mockResolvedValue([]);
+    mockProjectsApi.list.mockResolvedValue([
+      {
+        id: "project-1",
+        name: "Alpha",
+        description: null,
+        archivedAt: null,
+        color: "#445566",
+      },
+    ]);
+    mockAgentsApi.list.mockResolvedValue([]);
+    mockAgentsApi.adapterModels.mockResolvedValue([]);
+    mockAuthApi.getSession.mockResolvedValue({ user: { id: "user-1" } });
+    mockAssetsApi.uploadImage.mockResolvedValue({ contentPath: "/uploads/asset.png" });
+    mockInstanceSettingsApi.getExperimental.mockResolvedValue({ enableIsolatedWorkspaces: false });
+    mockIssuesApi.create.mockResolvedValue({
+      id: "issue-2",
+      companyId: "company-1",
+      identifier: "PAP-2",
+    });
+  });
+
+  afterEach(() => {
+    document.body.innerHTML = "";
+  });
+
+  it("shows sub-issue context only when opened from a sub-issue action", async () => {
+    dialogState.newIssueDefaults = {
+      parentId: "issue-1",
+      parentIdentifier: "PAP-1",
+      parentTitle: "Parent issue",
+      projectId: "project-1",
+      goalId: "goal-1",
+    };
+
+    const { root } = renderDialog(container);
+    await flush();
+
+    expect(container.textContent).toContain("New sub-issue");
+    expect(container.textContent).toContain("Sub-issue of");
+    expect(container.textContent).toContain("PAP-1");
+    expect(container.textContent).toContain("Parent issue");
+    expect(container.textContent).toContain("Create Sub-Issue");
+
+    act(() => root.unmount());
+
+    dialogState.newIssueDefaults = {};
+    const rerendered = renderDialog(container);
+    await flush();
+
+    expect(container.textContent).toContain("New issue");
+    expect(container.textContent).toContain("Create Issue");
+    expect(container.textContent).not.toContain("Sub-issue of");
+
+    act(() => rerendered.root.unmount());
+  });
+
+  it("submits parent and goal context for sub-issues", async () => {
+    dialogState.newIssueDefaults = {
+      parentId: "issue-1",
+      parentIdentifier: "PAP-1",
+      parentTitle: "Parent issue",
+      title: "Child issue",
+      projectId: "project-1",
+      goalId: "goal-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();
+    expect(submitButton?.hasAttribute("disabled")).toBe(false);
+
+    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",
+      }),
+    );
+
+    act(() => root.unmount());
+  });
+});
diff --git a/ui/src/components/NewIssueDialog.tsx b/ui/src/components/NewIssueDialog.tsx
index 95d30d2b..f402af27 100644
--- a/ui/src/components/NewIssueDialog.tsx
+++ b/ui/src/components/NewIssueDialog.tsx
@@ -46,6 +46,7 @@ import {
   Paperclip,
   FileText,
   Loader2,
+  ListTree,
   X,
 } from "lucide-react";
 import { cn } from "../lib/utils";
@@ -297,6 +298,9 @@ export function NewIssueDialog() {
 
   const effectiveCompanyId = dialogCompanyId ?? selectedCompanyId;
   const dialogCompany = companies.find((c) => c.id === effectiveCompanyId) ?? selectedCompany;
+  const isSubIssueMode = Boolean(newIssueDefaults.parentId);
+  const parentIssueLabel = newIssueDefaults.parentIdentifier
+    ?? (newIssueDefaults.parentId ? newIssueDefaults.parentId.slice(0, 8) : "");
 
   // Popover states
   const [statusOpen, setStatusOpen] = useState(false);
@@ -510,7 +514,23 @@ export function NewIssueDialog() {
     executionWorkspaceDefaultProjectId.current = null;
 
     const draft = loadDraft();
-    if (newIssueDefaults.title) {
+    if (newIssueDefaults.parentId) {
+      const defaultProjectId = newIssueDefaults.projectId ?? "";
+      const defaultProject = orderedProjects.find((project) => project.id === defaultProjectId);
+      setTitle(newIssueDefaults.title ?? "");
+      setDescription(newIssueDefaults.description ?? "");
+      setStatus(newIssueDefaults.status ?? "todo");
+      setPriority(newIssueDefaults.priority ?? "");
+      setProjectId(defaultProjectId);
+      setProjectWorkspaceId(defaultProjectWorkspaceIdForProject(defaultProject));
+      setAssigneeValue(assigneeValueFromSelection(newIssueDefaults));
+      setAssigneeModelOverride("");
+      setAssigneeThinkingEffort("");
+      setAssigneeChrome(false);
+      setExecutionWorkspaceMode(defaultExecutionWorkspaceModeForProject(defaultProject));
+      setSelectedExecutionWorkspaceId("");
+      executionWorkspaceDefaultProjectId.current = defaultProjectId || null;
+    } else if (newIssueDefaults.title) {
       setTitle(newIssueDefaults.title);
       setDescription(newIssueDefaults.description ?? "");
       setStatus(newIssueDefaults.status ?? "todo");
@@ -616,6 +636,7 @@ export function NewIssueDialog() {
   }
 
   function handleCompanyChange(companyId: string) {
+    if (isSubIssueMode) return;
     if (companyId === effectiveCompanyId) return;
     setDialogCompanyId(companyId);
     setAssigneeValue("");
@@ -666,6 +687,8 @@ export function NewIssueDialog() {
       priority: priority || "medium",
       ...(selectedAssigneeAgentId ? { assigneeAgentId: selectedAssigneeAgentId } : {}),
       ...(selectedAssigneeUserId ? { assigneeUserId: selectedAssigneeUserId } : {}),
+      ...(newIssueDefaults.parentId ? { parentId: newIssueDefaults.parentId } : {}),
+      ...(newIssueDefaults.goalId ? { goalId: newIssueDefaults.goalId } : {}),
       ...(projectId ? { projectId } : {}),
       ...(projectWorkspaceId ? { projectWorkspaceId } : {}),
       ...(assigneeAdapterOverrides ? { assigneeAdapterOverrides } : {}),
@@ -908,6 +931,7 @@ export function NewIssueDialog() {
                     "px-1.5 py-0.5 rounded text-xs font-semibold cursor-pointer hover:opacity-80 transition-opacity",
                     !dialogCompany?.brandColor && "bg-muted",
                   )}
+                  disabled={isSubIssueMode}
                   style={
                     dialogCompany?.brandColor
                       ? {
@@ -955,7 +979,7 @@ export function NewIssueDialog() {
               </PopoverContent>
             </Popover>
             <span className="text-muted-foreground/60">&rsaquo;</span>
-            <span>New issue</span>
+            <span>{isSubIssueMode ? "New sub-issue" : "New issue"}</span>
           </div>
           <div className="flex items-center gap-1">
             <Button
@@ -1119,6 +1143,19 @@ export function NewIssueDialog() {
           </div>
         </div>
 
+        {isSubIssueMode ? (
+          <div className="px-4 pb-2 shrink-0">
+            <div className="inline-flex max-w-full items-center gap-1.5 rounded-md border border-border bg-muted/30 px-2.5 py-1 text-xs text-muted-foreground">
+              <ListTree className="h-3.5 w-3.5 shrink-0" />
+              <span className="shrink-0">Sub-issue of</span>
+              <span className="font-medium text-foreground">{parentIssueLabel}</span>
+              {newIssueDefaults.parentTitle ? (
+                <span className="truncate">· {newIssueDefaults.parentTitle}</span>
+              ) : null}
+            </div>
+          </div>
+        ) : null}
+
         {currentProject && currentProjectSupportsExecutionWorkspace && (
           <div className="px-4 py-3 shrink-0 space-y-2">
             <div className="space-y-1.5">
@@ -1455,7 +1492,7 @@ export function NewIssueDialog() {
             >
               <span className="inline-flex items-center justify-center gap-1.5">
                 {createIssue.isPending ? <Loader2 className="h-3.5 w-3.5 animate-spin" /> : null}
-                <span>{createIssue.isPending ? "Creating..." : "Create Issue"}</span>
+                <span>{createIssue.isPending ? "Creating..." : isSubIssueMode ? "Create Sub-Issue" : "Create Issue"}</span>
               </span>
             </Button>
           </div>
diff --git a/ui/src/context/DialogContext.tsx b/ui/src/context/DialogContext.tsx
index 904ceb88..bd475b33 100644
--- a/ui/src/context/DialogContext.tsx
+++ b/ui/src/context/DialogContext.tsx
@@ -4,6 +4,10 @@ interface NewIssueDefaults {
   status?: string;
   priority?: string;
   projectId?: string;
+  goalId?: string;
+  parentId?: string;
+  parentIdentifier?: string;
+  parentTitle?: string;
   assigneeAgentId?: string;
   assigneeUserId?: string;
   title?: string;
diff --git a/ui/src/pages/IssueDetail.tsx b/ui/src/pages/IssueDetail.tsx
index c1602d34..63a63938 100644
--- a/ui/src/pages/IssueDetail.tsx
+++ b/ui/src/pages/IssueDetail.tsx
@@ -1,4 +1,4 @@
-import { useEffect, useMemo, useRef, useState, type ChangeEvent, type DragEvent } from "react";
+import { useCallback, useEffect, useMemo, useRef, useState, type ChangeEvent, type DragEvent } from "react";
 import { pickTextColorForPillBg } from "@/lib/color-contrast";
 import { Link, useLocation, useNavigate, useParams } from "@/lib/router";
 import { useQuery, useMutation, useQueryClient } from "@tanstack/react-query";
@@ -11,6 +11,7 @@ import { agentsApi } from "../api/agents";
 import { authApi } from "../api/auth";
 import { projectsApi } from "../api/projects";
 import { useCompany } from "../context/CompanyContext";
+import { useDialog } from "../context/DialogContext";
 import { usePanel } from "../context/PanelContext";
 import { useToast } from "../context/ToastContext";
 import { useBreadcrumbs } from "../context/BreadcrumbContext";
@@ -291,6 +292,7 @@ function ActorIdentity({ evt, agentMap }: { evt: ActivityEvent; agentMap: Map<st
 export function IssueDetail() {
   const { issueId } = useParams<{ issueId: string }>();
   const { selectedCompanyId, selectedCompany } = useCompany();
+  const { openNewIssue } = useDialog();
   const { openPanel, closePanel, panelVisible, setPanelVisible } = usePanel();
   const { setBreadcrumbs } = useBreadcrumbs();
   const queryClient = useQueryClient();
@@ -496,6 +498,16 @@ export function IssueDetail() {
       .filter((i) => i.parentId === issue.id)
       .sort((a, b) => new Date(a.createdAt).getTime() - new Date(b.createdAt).getTime());
   }, [allIssues, issue]);
+  const openNewSubIssue = useCallback(() => {
+    if (!issue) return;
+    openNewIssue({
+      parentId: issue.id,
+      parentIdentifier: issue.identifier ?? undefined,
+      parentTitle: issue.title,
+      projectId: issue.projectId ?? undefined,
+      goalId: issue.goalId ?? undefined,
+    });
+  }, [issue, openNewIssue]);
 
   const commentReassignOptions = useMemo(() => {
     const options: Array<{ id: string; label: string; searchText?: string }> = [];
@@ -1042,11 +1054,16 @@ export function IssueDetail() {
   useEffect(() => {
     if (issue) {
       openPanel(
-        <IssueProperties issue={issue} onUpdate={(data) => updateIssue.mutate(data)} />
+        <IssueProperties
+          issue={issue}
+          childIssues={childIssues}
+          onAddSubIssue={openNewSubIssue}
+          onUpdate={(data) => updateIssue.mutate(data)}
+        />
       );
     }
     return () => closePanel();
-  }, [issue]); // eslint-disable-line react-hooks/exhaustive-deps
+  }, [childIssues, closePanel, issue, openNewSubIssue, openPanel, updateIssue]);
 
   const inboxQuickArchiveArmedRef = useRef(false);
   const canQuickArchiveFromInbox =
@@ -1639,6 +1656,11 @@ export function IssueDetail() {
         </TabsContent>
 
         <TabsContent value="subissues">
+          <div className="mb-3 flex items-center justify-end">
+            <Button variant="outline" size="sm" onClick={openNewSubIssue}>
+              Add sub-issue
+            </Button>
+          </div>
           {childIssues.length === 0 ? (
             <p className="text-xs text-muted-foreground">No sub-issues.</p>
           ) : (
@@ -1779,7 +1801,13 @@ export function IssueDetail() {
           </SheetHeader>
           <ScrollArea className="flex-1 overflow-y-auto">
             <div className="px-4 pb-4">
-              <IssueProperties issue={issue} onUpdate={(data) => updateIssue.mutate(data)} inline />
+              <IssueProperties
+                issue={issue}
+                childIssues={childIssues}
+                onAddSubIssue={openNewSubIssue}
+                onUpdate={(data) => updateIssue.mutate(data)}
+                inline
+              />
             </div>
           </ScrollArea>
         </SheetContent>