diff --git a/app/routers/agents.py b/app/routers/agents.py
index 520f10e..454a327 100644
--- a/app/routers/agents.py
+++ b/app/routers/agents.py
@@ -267,7 +267,23 @@ async def regenerate_webhook_secret_endpoint(
 @router.get("/{ref}/inbox")
 async def get_inbox_endpoint(
     ref: str,
-    state: Optional[str] = Query(default=None, description="Comma-separated states; default excludes acked/expired"),
+    state: Optional[str] = Query(
+        default=None,
+        description=(
+            "Comma-separated states to include. Default excludes ``acked`` "
+            "+ ``expired`` (worker-runtime/agent-handler default — those "
+            "consumers poll for actionable messages only). "
+            "**Conversation/transcript consumers** (chat UI, message-thread "
+            "renderer, audit log, etc.) should pass an explicit "
+            "``state=queued,delivering,retry_ready,delivered,read,claimed,acked,expired,failed`` "
+            "to include the full history — otherwise messages that have "
+            "been ``acked`` (e.g., by the recipient's own desktop worker) "
+            "vanish from the conversation view while the sender's bubble "
+            "remains visible via the symmetric ``GET /v1/messages`` sent "
+            "view. See ``Conversation-view consumer note`` in the "
+            "docstring below."
+        ),
+    ),
     since: Optional[datetime] = Query(default=None),
     thread_id: Optional[str] = Query(default=None),
     counterpart: Optional[str] = Query(
@@ -297,6 +313,34 @@ async def get_inbox_endpoint(
     from that counterpart agent only. The atomic queued→delivered
     UPDATE applies the same filter so polling a single counterpart
     thread doesn't auto-deliver other threads' queued messages.
+
+    ## Conversation-view consumer note (v1.1.5 docs)
+
+    The default ``state=`` filter excludes ``acked`` + ``expired``. That
+    default is right for **worker-runtime / agent-handler consumers**
+    that poll for new actionable work — they don't want to re-process
+    messages they've already acknowledged.
+
+    It's **wrong** for conversation/transcript consumers (chat UIs,
+    message-thread renderers, audit logs, support tools) because
+    ``acked`` messages disappear from the recipient's inbox view while
+    they remain visible on the sender's side via ``GET /v1/messages``
+    (sent view). That asymmetry produces a confusing UX: the sender
+    sees their own message in the conversation, but the recipient's
+    pane shows nothing — even though the message WAS delivered and
+    acknowledged successfully.
+
+    **Fix for conversation views**: pass an explicit
+    ``state=queued,delivering,retry_ready,delivered,read,claimed,acked,expired,failed``
+    on the inbox fetch. This includes the full state set + matches
+    the symmetric sent-side view, restoring conversation parity.
+
+    Empirical anchor: 2026-05-21, Dock's ``cue.dock.svc`` ``/api/threads``
+    consumer hit this trap — their recipient pane was empty for
+    cross-user messages while sent-side bubbles rendered correctly.
+    Substrate behavior is correct (messages WERE delivered + acked
+    fast by Dock's desktop worker); Dock fixed Dock-side by passing
+    the full state set on their threads-view fetch.
     """
     result = await list_inbox(
         db,