diff --git a/examples/chat/angular/src/app/shell/threads.service.ts b/examples/chat/angular/src/app/shell/threads.service.ts
index 182464197..b76fd2c13 100644
--- a/examples/chat/angular/src/app/shell/threads.service.ts
+++ b/examples/chat/angular/src/app/shell/threads.service.ts
@@ -74,7 +74,15 @@ export class ThreadsService {
     await this.refresh();
   }
 
-  /** Best-effort title from thread metadata; falls back to a truncated id. */
+  /** Best-effort title from thread metadata.
+   *
+   * The backend writes `metadata.title` from the first user message in a
+   * thread (see `_maybe_write_thread_title` in the Python graph). Threads
+   * created but never sent (e.g. via "+ New chat" then abandoned) have
+   * no title, so we fall back to "Untitled" — easier on the eye than
+   * the raw `Thread 019e1e98` id prefix, and consistent with how other
+   * chat apps surface drafts.
+   */
   private toThread(t: SdkThread): Thread {
     const meta = (t.metadata ?? {}) as { title?: unknown; archived?: unknown; pinned?: unknown; projectId?: unknown };
     const customTitle = meta.title;
@@ -87,7 +95,7 @@ export class ThreadsService {
       id: t.thread_id,
       title: typeof customTitle === 'string' && customTitle.length > 0
         ? customTitle
-        : `Thread ${t.thread_id.slice(0, 8)}`,
+        : 'Untitled',
       status: archived ? 'archived' : 'active',
       pinned,
       projectId,
diff --git a/examples/chat/python/src/streaming/envelope_tool.py b/examples/chat/python/src/streaming/envelope_tool.py
index 74270bc8b..1f32af91f 100644
--- a/examples/chat/python/src/streaming/envelope_tool.py
+++ b/examples/chat/python/src/streaming/envelope_tool.py
@@ -13,7 +13,7 @@
 from typing import Optional
 
 from langchain_core.tools import tool
-from pydantic import BaseModel, Field
+from pydantic import BaseModel, Field, model_validator
 
 
 class SurfaceUpdate(BaseModel):
@@ -42,11 +42,25 @@ class DataModelUpdate(BaseModel):
 
 class A2uiEnvelope(BaseModel):
     """Single A2UI v1 envelope. Exactly one of the three discriminators
-    is set per envelope."""
+    is set per envelope — the model_validator below enforces this so the
+    parent LLM cannot emit ambiguous or empty envelopes."""
     surfaceUpdate: Optional[SurfaceUpdate] = None
     beginRendering: Optional[BeginRendering] = None
     dataModelUpdate: Optional[DataModelUpdate] = None
 
+    @model_validator(mode="after")
+    def _exactly_one_discriminator(self) -> "A2uiEnvelope":
+        present = sum(
+            1 for v in (self.surfaceUpdate, self.beginRendering, self.dataModelUpdate)
+            if v is not None
+        )
+        if present != 1:
+            raise ValueError(
+                f"A2uiEnvelope requires exactly one of "
+                f"surfaceUpdate / beginRendering / dataModelUpdate; got {present}"
+            )
+        return self
+
 
 @tool
 def render_a2ui_surface(envelopes: list[A2uiEnvelope]) -> str:
diff --git a/examples/chat/python/tests/test_envelope_tool.py b/examples/chat/python/tests/test_envelope_tool.py
index d922763cd..4f848a9db 100644
--- a/examples/chat/python/tests/test_envelope_tool.py
+++ b/examples/chat/python/tests/test_envelope_tool.py
@@ -32,6 +32,19 @@ def test_a2ui_envelope_accepts_surface_update_field(self):
         assert e.beginRendering is None
         assert e.dataModelUpdate is None
 
+    def test_a2ui_envelope_rejects_empty(self):
+        """An envelope with zero discriminators set is rejected."""
+        with pytest.raises(ValueError, match="exactly one"):
+            A2uiEnvelope()
+
+    def test_a2ui_envelope_rejects_multiple_discriminators(self):
+        """An envelope with two discriminators set is rejected."""
+        with pytest.raises(ValueError, match="exactly one"):
+            A2uiEnvelope(
+                surfaceUpdate={"surfaceId": "s", "components": []},
+                beginRendering={"surfaceId": "s", "root": "r"},
+            )
+
 
 class TestRenderA2uiSurfaceTool:
     def test_serializes_envelopes_to_json_string(self):
diff --git a/examples/chat/smoke/CHECKLIST.md b/examples/chat/smoke/CHECKLIST.md
index d47738921..24cd0e10f 100644
--- a/examples/chat/smoke/CHECKLIST.md
+++ b/examples/chat/smoke/CHECKLIST.md
@@ -389,3 +389,32 @@ Components NOT yet exercised by the demo (deferred to future media-focused sugge
 - [ ] At viewport ≤ 768px: chat input + send remain accessible; sidenav does not push the chat horizontally
 - [ ] No horizontal scrollbar at any tested viewport
 - [ ] Toggling collapse manually overrides the responsive default until the next breakpoint crossing
+
+## Projects
+
+- [ ] Sidenav renders a **PROJECTS** section between Search and RECENT
+- [ ] "+ New project" affordance visible at the top of the section
+- [ ] Clicking "+ New project" replaces the affordance with an inline input ("New project name", autofocused)
+- [ ] Typing a name + Enter creates the project, persists to `localStorage` (`ngaf-chat-demo:projects`), and **auto-selects** it
+- [ ] Escape (or blur with empty value) cancels the inline create
+- [ ] Selecting a project filters the RECENT list to threads whose `metadata.projectId` matches
+- [ ] Selecting an empty project leaves RECENT empty; ARCHIVED section unaffected
+- [ ] Clicking the active project row again deselects it (RECENT returns to unfiltered)
+- [ ] Active project row is visually distinguished (`data-active`)
+- [ ] Hover a project row — kebab fades in
+- [ ] Kebab menu order: **Rename**, **Delete** (no Pin/Unpin/Archive — projects are a different surface)
+- [ ] **Rename** → inline edit input on the row; Enter commits, Escape cancels; persists across reload
+- [ ] **Delete** → confirmation dialog; on confirm, project removed; member threads remain (projectId becomes orphaned and threads fall back to default RECENT)
+- [ ] Project state (list + selected id) persists across reload
+
+## Move thread to project
+
+- [ ] With at least one project created, open a thread row's kebab in active mode
+- [ ] Menu order: **Rename**, **Pin/Unpin**, **Move to project**, **Archive**, **Delete**
+- [ ] Clicking "Move to project" opens a second overflow-menu (submenu) anchored to the same kebab
+- [ ] Submenu lists `[No project, ...projects]` with the thread's current projectId highlighted
+- [ ] Selecting a project moves the thread (PATCH `metadata.projectId`); the thread disappears from the current view (optimistic-hide)
+- [ ] After the next sidenav refresh, the thread appears under the new project's filtered list
+- [ ] Selecting "No project" clears the thread's projectId; thread returns to default RECENT
+- [ ] Move action is idempotent (selecting the current project is a no-op)
+- [ ] No `console.error` during project create / rename / delete / move