diff --git a/backend/apps/agents/core/models.py b/backend/apps/agents/core/models.py
index 4578ef7e..e66ac124 100644
--- a/backend/apps/agents/core/models.py
+++ b/backend/apps/agents/core/models.py
@@ -13,6 +13,9 @@ class AgentConfig(BaseModel):
     max_turns: Optional[int] = None
     target_directory: Optional[str] = None
     dashboard_id: Optional[str] = None
+    # App cards the user picked to edit. When exactly one resolves, launch
+    # binds the chat's cwd to that app instead of seeding a new "Untitled App".
+    selected_app_output_ids: Optional[list[str]] = None
 
 class ApprovalRequest(BaseModel):
     id: str = Field(default_factory=lambda: uuid4().hex)
diff --git a/backend/apps/agents/manager/AgentLaunchMixin.py b/backend/apps/agents/manager/AgentLaunchMixin.py
index 382a7b0f..ddf3abba 100644
--- a/backend/apps/agents/manager/AgentLaunchMixin.py
+++ b/backend/apps/agents/manager/AgentLaunchMixin.py
@@ -34,6 +34,21 @@ class AgentLaunchMixin:
     async def launch_agent(self, config: AgentConfig) -> AgentSession:
         session_id = uuid4().hex
 
+        # Editing an existing App: when the user selected exactly one App card
+        # in App Builder mode, point the chat at that app's workspace so it
+        # edits in place. Without this the view-builder seed below fires (no
+        # target_directory) and registers a fresh empty "Untitled App" dupe.
+        if (
+            config.mode == "view-builder"
+            and not config.target_directory
+            and config.selected_app_output_ids
+            and len(config.selected_app_output_ids) == 1
+        ):
+            from backend.apps.outputs.workspace_io import app_workspace_dir
+            bound = app_workspace_dir(config.selected_app_output_ids[0])
+            if bound:
+                config.target_directory = bound
+
         mode_tools, _, mode_folder = resolve_mode(config.mode, get_all_tool_names)
         tools = mode_tools
 
diff --git a/backend/apps/outputs/workspace_io.py b/backend/apps/outputs/workspace_io.py
index 33e6d44a..8f857e38 100644
--- a/backend/apps/outputs/workspace_io.py
+++ b/backend/apps/outputs/workspace_io.py
@@ -7,7 +7,7 @@ import os
 from fastapi import HTTPException
 
 from backend.apps.outputs.models import Output
-from backend.config.paths import OUTPUTS_DIR as DATA_DIR
+from backend.config.paths import OUTPUTS_DIR as DATA_DIR, OUTPUTS_WORKSPACE_DIR
 from backend.config.json_store import read_json_or_none, atomic_write_json
 
 logger = logging.getLogger(__name__)
@@ -46,6 +46,18 @@ def load_output(output_id: str) -> Output | None:
     return Output(**data) if data is not None else None
 
 
+def app_workspace_dir(output_id: str) -> str | None:
+    """Resolve an App (Output) id to its on-disk workspace folder, or None if
+    the app or its folder is gone. Shared by the prompt-context builder (which
+    files the agent should edit) and launch (binds the chat's cwd to the app so
+    editing it doesn't seed a duplicate 'Untitled App')."""
+    output = load_output(output_id)
+    if not output or not output.workspace_id:
+        return None
+    path = os.path.abspath(os.path.join(OUTPUTS_WORKSPACE_DIR, output.workspace_id))
+    return path if os.path.isdir(path) else None
+
+
 # Build/install/cache directories that the polling endpoint must never
 # descend into. Without this skip-list the workspace endpoint reads
 # `node_modules/` (300 MB of MUI source, when it's a real dir and not a
diff --git a/backend/tests/test_app_edit_bind.py b/backend/tests/test_app_edit_bind.py
new file mode 100644
index 00000000..be6a2420
--- /dev/null
+++ b/backend/tests/test_app_edit_bind.py
@@ -0,0 +1,58 @@
+"""Editing an existing App must bind to its workspace, never seed a dupe.
+
+`app_workspace_dir` is the resolver launch_agent uses to turn a selected App
+(Output) id into the cwd it should edit in place. If it returns a real path,
+launch sets target_directory and the view-builder seed is skipped; if it
+returns None the seed fires and a duplicate "Untitled App" is born (the bug
+this locks out). Path constants are module-level, so (like test_seed_no_clobber)
+we monkeypatch a temp tree.
+"""
+import json
+import os
+
+import pytest
+
+from backend.apps.outputs import workspace_io as wio
+from backend.apps.outputs.models import Output
+
+
+@pytest.fixture
+def out_root(tmp_path, monkeypatch):
+    data = tmp_path / "outputs"
+    ws = tmp_path / "outputs_workspace"
+    data.mkdir()
+    ws.mkdir()
+    monkeypatch.setattr(wio, "DATA_DIR", str(data))
+    monkeypatch.setattr(wio, "OUTPUTS_WORKSPACE_DIR", str(ws))
+    return data, ws
+
+
+def _write_output(data_dir, **kw):
+    o = Output(**kw)
+    with open(os.path.join(str(data_dir), f"{o.id}.json"), "w") as f:
+        json.dump(o.model_dump(), f)
+    return o
+
+
+def test_resolves_existing_app_workspace(out_root):
+    data, ws = out_root
+    os.makedirs(os.path.join(str(ws), "ws-app"))
+    o = _write_output(data, name="Voxelcraft", workspace_id="ws-app")
+    assert wio.app_workspace_dir(o.id) == os.path.abspath(os.path.join(str(ws), "ws-app"))
+
+
+def test_missing_output_returns_none(out_root):
+    # Deleted/bogus selection -> no bind -> launch falls through to a normal new build.
+    assert wio.app_workspace_dir("doesnotexist") is None
+
+
+def test_output_without_workspace_returns_none(out_root):
+    data, _ = out_root
+    o = _write_output(data, name="NoWorkspace", workspace_id=None)
+    assert wio.app_workspace_dir(o.id) is None
+
+
+def test_output_with_vanished_folder_returns_none(out_root):
+    data, _ = out_root
+    o = _write_output(data, name="Gone", workspace_id="ws-vanished")  # folder never created
+    assert wio.app_workspace_dir(o.id) is None
diff --git a/frontend/src/app/pages/AgentChat/AgentChat.tsx b/frontend/src/app/pages/AgentChat/AgentChat.tsx
index 9c1768c8..c8237d3b 100644
--- a/frontend/src/app/pages/AgentChat/AgentChat.tsx
+++ b/frontend/src/app/pages/AgentChat/AgentChat.tsx
@@ -407,6 +407,9 @@ const AgentChat: React.FC<AgentChatProps> = ({ sessionId: sessionIdProp, onClose
       // session lands dashboard_id=null, drops out of the reconcile filter, and its card vanishes
       // the instant you send (looked like "the chat quit when I clicked an option").
       if (session?.dashboard_id) config.dashboard_id = session.dashboard_id;
+      // Editing an existing app: bind the launch to it so the backend edits in
+      // place instead of seeding a duplicate empty app (App Builder mode only).
+      if (msg.selectedAppIds?.length) config.selected_app_output_ids = msg.selectedAppIds;
       dispatch(
         launchAndSendFirstMessage({ draftId: id, config, prompt: msg.prompt, mode, model, images: msg.images, contextPaths: msg.contextPaths, forcedTools: msg.forcedTools, attachedSkills: msg.attachedSkills, selectedBrowserIds: msg.selectedBrowserIds, selectedAppIds: msg.selectedAppIds, selectedSettingIds: msg.selectedSettingIds })
       ).then((action) => {
diff --git a/frontend/src/app/pages/Dashboard/DashboardToolbar.tsx b/frontend/src/app/pages/Dashboard/DashboardToolbar.tsx
index bedf49b5..ecf1cfc8 100644
--- a/frontend/src/app/pages/Dashboard/DashboardToolbar.tsx
+++ b/frontend/src/app/pages/Dashboard/DashboardToolbar.tsx
@@ -49,6 +49,7 @@ interface Props {
     forcedTools?: string[],
     attachedSkills?: Array<{ id: string; name: string; content: string }>,
     selectedBrowserIds?: string[],
+    selectedAppIds?: string[],
   ) => void;
   onAddView: (outputId: string) => void;
   onHistoryResume: (sessionId: string) => void;
@@ -213,8 +214,9 @@ const DashboardToolbar = React.forwardRef<HTMLDivElement, Props>(
         forcedTools?: string[],
         attachedSkills?: Array<{ id: string; name: string; content: string }>,
         selectedBrowserIds?: string[],
+        selectedAppIds?: string[],
       ) => {
-        onSend(message, mode, model, images, contextPaths, forcedTools, attachedSkills, selectedBrowserIds);
+        onSend(message, mode, model, images, contextPaths, forcedTools, attachedSkills, selectedBrowserIds, selectedAppIds);
       },
       [onSend, mode, model],
     );
diff --git a/frontend/src/app/pages/Dashboard/hooks/lifecycle/useAgentSpawn.ts b/frontend/src/app/pages/Dashboard/hooks/lifecycle/useAgentSpawn.ts
index 918ccc09..1cba1dc2 100644
--- a/frontend/src/app/pages/Dashboard/hooks/lifecycle/useAgentSpawn.ts
+++ b/frontend/src/app/pages/Dashboard/hooks/lifecycle/useAgentSpawn.ts
@@ -127,6 +127,7 @@ export function useAgentSpawn({
       forcedTools?: string[],
       attachedSkills?: Array<{ id: string; name: string; content: string }>,
       selectedBrowserIds?: string[],
+      selectedAppIds?: string[],
     ) => {
       setToolbarOpen(false);
       report('dashboard', 'agent_created', { mode, model, has_images: !!images?.length, has_context: !!contextPaths?.length, has_browser: !!selectedBrowserIds?.length });
@@ -148,6 +149,9 @@ export function useAgentSpawn({
       }
 
       const config: AgentConfig = { name: 'New chat', model, mode, dashboard_id: dashboardId };
+      // Editing an existing app: bind the launch to it so the backend edits in
+      // place instead of seeding a duplicate empty app (App Builder mode only).
+      if (selectedAppIds?.length) config.selected_app_output_ids = selectedAppIds;
 
       dispatch(
         launchAndSendFirstMessage({
@@ -161,6 +165,7 @@ export function useAgentSpawn({
           forcedTools,
           attachedSkills,
           selectedBrowserIds,
+          selectedAppIds,
           expand: expandNewChats,
         }),
       ).then((action) => {
diff --git a/frontend/src/shared/state/agentsSlice.ts b/frontend/src/shared/state/agentsSlice.ts
index 0592abe5..25631095 100644
--- a/frontend/src/shared/state/agentsSlice.ts
+++ b/frontend/src/shared/state/agentsSlice.ts
@@ -125,6 +125,7 @@ export interface AgentConfig {
   max_turns?: number;
   target_directory?: string;
   dashboard_id?: string;
+  selected_app_output_ids?: string[];
 }
 
 export interface HistorySession {