diff --git a/docs/specification/embedded-cart.md b/docs/specification/embedded-cart.md
index 8ed212e6..2c68a488 100644
--- a/docs/specification/embedded-cart.md
+++ b/docs/specification/embedded-cart.md
@@ -361,6 +361,8 @@ proceed to initiate a checkout session based on the completed cart by issuing a
 - **Type:** Notification
 - **Payload:**
     - `cart` (object, **REQUIRED**): The final state of the cart.
+    - `transition` (object, **OPTIONAL**): Advertisement for availability to transition
+        directly into Embedded Checkout.
 
 **Example Message:**
 
@@ -381,6 +383,59 @@ proceed to initiate a checkout session based on the completed cart by issuing a
 }
 ```
 
+Business **MAY** also choose to specify a `transition` field to advertise a mechanism
+for hosts to seamlessly transition into Embedded Checkout from the completed
+Embedded Cart. This is represented by `transition` containing a minimal `checkout` object:
+
+- `ucp` (object, **REQUIRED**): Metadata to fully qualify the advertisement.
+    Business **MUST** include a checkout capability and an embedded service binding
+    with `config.delegate`.
+- `url` (string, **REQUIRED**): URL representing shift to checkout. Business **MUST**
+    specify a HTTPS URL and **MAY** choose a stateless URL like permalink. See
+    [Checkout Capability - Continue URL Format](checkout.md#format).
+
+**Example Message With `transition`:**
+
+```json
+{
+    "jsonrpc": "2.0",
+    "method": "ep.cart.complete",
+    "params": {
+        "cart": { ...cart fields... },
+        "transition": {
+            "checkout": {
+                "ucp": {
+                    "version": "{{ ucp_version }}",
+                    "status": "success",
+                    "capabilities": {
+                        "dev.ucp.shopping.checkout": [ { "version": "{{ ucp_version }}" } ]
+                    },
+                    "services": {
+                        "dev.ucp.shopping": [
+                            {
+                                "version": "{{ ucp_version }}",
+                                "transport": "embedded",
+                                "config": {
+                                    "delegate": [...]
+                                }
+                            }
+                        ]
+                    }
+                },
+                "url": "https://merchant.example.com/cart-to-checkout/checkout123",
+            }
+        }
+    }
+}
+```
+
+When `transition` is received as part of `ep.cart.complete`, the host **MAY** choose
+to initiate Embedded Checkout by appending `checkout.url` with relevant parameters -
+see [Embedded Checkout - Loading an Embedded Checkout URL](embedded-checkout.md#loading-an-embedded-checkout-url).
+Host also has full flexibility over how they want to render Embedded Checkout (i.e.
+reuse the same embedded context as Embedded Cart or tear down the current one in favour
+of bootstrapping a new embedded context).
+
 ### State Change Messages
 
 State change notifications follow the shared EP pattern — see
diff --git a/docs/specification/embedded-checkout.md b/docs/specification/embedded-checkout.md
index e580f95e..6196637f 100644
--- a/docs/specification/embedded-checkout.md
+++ b/docs/specification/embedded-checkout.md
@@ -131,10 +131,11 @@ indicate ECP availability and allowed delegations for a specific session.
 ```json
 {
     "id": "checkout_abc123",
-    "status": "open",
+    "status": "incomplete",
     "continue_url": "https://merchant.example.com/checkout/abc123",
     "ucp": {
         "version": "{{ ucp_version }}",
+        "status": "success",
         "services": {
             "dev.ucp.shopping": [
                 {
diff --git a/source/services/shopping/embedded.openrpc.json b/source/services/shopping/embedded.openrpc.json
index 4210fea0..cfcefae8 100644
--- a/source/services/shopping/embedded.openrpc.json
+++ b/source/services/shopping/embedded.openrpc.json
@@ -496,6 +496,29 @@
             "$ref": "../../schemas/shopping/cart.json",
             "description": "Final cart state."
           }
+        },
+        {
+          "name": "transition",
+          "schema": {
+            "type": "object",
+            "description": "Optional advertisement from business for seamless transition from cart to checkout.",
+            "required": ["checkout"],
+            "properties": {
+              "checkout": {
+                "type": "object",
+                "description": "Metadata required by the host to bootstrap and transition into an embedded checkout session.",
+                "required": ["ucp", "url"],
+                "properties": {
+                  "ucp": { "$ref": "#/components/schemas/ucp_success" },
+                  "url": {
+                    "type": "string",
+                    "format": "uri",
+                    "description": "The transition URL."
+                  }
+                }
+              }
+            }
+          }
         }
       ]
     },