diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4d64bf3..5ed049a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+- The inbound telegram simulation delivers a complete `Update` (`update_id`,
+  `message_id`, `date`, `from` and a typed `chat`), so clients that parse it
+  with `Update.de_json` no longer fail on the webhook they just received.
+
 ## [0.2.0] - 2026-08-13
 
 ### Added
diff --git a/mockpost/routers/telegram.py b/mockpost/routers/telegram.py
index 8aada01..3448ad1 100644
--- a/mockpost/routers/telegram.py
+++ b/mockpost/routers/telegram.py
@@ -38,6 +38,7 @@
 TOKEN_RE = re.compile(r"^\d+:[A-Za-z0-9_-]{35}$")
 
 _message_ids = count(1000)
+_update_ids = count(1)
 
 
 class ClientMessage(BaseModel):
@@ -70,6 +71,29 @@ def chat_of(chat_id: Any) -> dict:
     return {"id": numeric, "type": "supergroup" if numeric < 0 else "private"}
 
 
+def inbound_update(chat_id: int | str, text: str, from_user: str | None,
+                   message_id_seed: str) -> dict:
+    """A complete Update, the shape every Bot API client deserializes.
+
+    Clients do not read the raw dict: python-telegram-bot calls
+    `Update.de_json`, which needs `update_id` and, inside `message`,
+    `message_id`, `date`, `chat` and `from`. Delivering a partial body made
+    those clients raise on the webhook they had just received."""
+    numeric_seed = abs(hash(message_id_seed)) % 1_000_000
+    return {
+        "update_id": next(_update_ids),
+        "message": {
+            "message_id": numeric_seed,
+            "date": int(time.time()),
+            "chat": chat_of(chat_id),
+            "from": {"id": numeric_seed, "is_bot": False,
+                     "first_name": from_user or "Simulated",
+                     "username": from_user or "simulated"},
+            "text": text,
+        },
+    }
+
+
 def message_object(token: str, chat_id: Any, **content) -> dict:
     return {"message_id": next(_message_ids), "from": bot_user(token),
             "chat": chat_of(chat_id), "date": int(time.time()), **content}
@@ -287,7 +311,8 @@ async def client_send_message(payload: ClientMessage, request: Request):
         raw_payload=payload.model_dump(), status="received", test_id=test_id, app_id=app_id,
     )
     results = await deliver_to_app_webhooks(
-        "telegram", "message", {"message": {"chat": {"id": payload.chat_id}, "text": payload.text}},
+        "telegram", "message",
+        inbound_update(payload.chat_id, payload.text, payload.from_user, msg_id),
         test_id=test_id, app_id=app_id,
     )
     return {"ok": True, "message_id": msg_id, "app_id": app_id, "webhooks_delivered": results}
diff --git a/tests/test_telegram.py b/tests/test_telegram.py
index ec64fa1..1e4cbb6 100644
--- a/tests/test_telegram.py
+++ b/tests/test_telegram.py
@@ -111,3 +111,23 @@ def test_get_updates_returns_simulated_inbound_messages(client):
     updates = client.post(f"/telegram/bot{TOKEN}/getUpdates").json()["result"]
     assert updates[0]["message"]["text"] == "from a user"
     assert updates[0]["message"]["chat"]["id"] == 555
+
+
+def test_inbound_simulation_delivers_a_complete_update(client):
+    """The delivered body must be a full Update: clients deserialize it with
+    Update.de_json, which needs update_id, message_id, date, chat and from."""
+    client.post("/api/apps", json={"name": "bot-app", "creds": {"bot_token": TOKEN}})
+    client.post("/api/webhooks", json={"channel": "telegram", "app": "bot-app",
+                                       "target_url": "http://127.0.0.1:9/tg"})
+    client.post("/telegram/client/sendMessage",
+                headers={"X-MockPost-App": "bot-app"},
+                json={"chat_id": 778899, "text": "/start ABC12345", "from_user": "tester"})
+
+    delivery = client.get("/api/webhooks/deliveries", params={"channel": "telegram"}).json()[0]
+    update = json.loads(delivery["payload"])
+    assert update["update_id"] >= 1
+    message = update["message"]
+    assert message["message_id"] and message["date"]
+    assert message["chat"] == {"id": 778899, "type": "private"}
+    assert message["from"]["username"] == "tester"
+    assert message["text"] == "/start ABC12345"