diff --git a/agents/deploy/protocol.mdx b/agents/deploy/protocol.mdx
index 5808bbd..a4b8a59 100644
--- a/agents/deploy/protocol.mdx
+++ b/agents/deploy/protocol.mdx
@@ -55,13 +55,13 @@ The response is a discriminated union on `transport`. The `livekit` arm carries
 
 Once connected, a session uses these channels. The two `*-event` topics carry reliable [data packets](https://docs.livekit.io/home/client/data/messages/): one complete JSON object per packet.
 
-| Channel                                | Direction      | Carries                                                   |
-| -------------------------------------- | -------------- | --------------------------------------------------------- |
-| Audio tracks                           | both           | Your microphone up, the agent's speech down               |
-| `agent-event` topic                    | agent → client | Control events: client tool calls, tool lifecycle, errors |
-| `client-event` topic                   | client → agent | Text turns, activity, interrupts, hangup, tool results    |
-| `lk.transcription` text streams        | agent → client | Streaming transcripts for both sides                      |
-| `lk.agent.state` participant attribute | agent → client | Agent pipeline state (sticky)                             |
+| Channel                                | Direction      | Carries                                                                |
+| -------------------------------------- | -------------- | ---------------------------------------------------------------------- |
+| Audio tracks                           | both           | Your microphone up, the agent's speech down                            |
+| `agent-event` topic                    | agent → client | Control events: client tool calls, tool lifecycle, errors, session end |
+| `client-event` topic                   | client → agent | Text turns, activity, interrupts, hangup, tool results                 |
+| `lk.transcription` text streams        | agent → client | Streaming transcripts for both sides                                   |
+| `lk.agent.state` participant attribute | agent → client | Agent pipeline state (sticky)                                          |
 
 Data-channel message fields are camelCase; REST bodies are snake_case.
 
@@ -166,6 +166,14 @@ These events are on by default and their payloads travel to the end user's clien
 
 `code` is a coarse category only: `provider_error` (an upstream model or voice provider failed) or `internal_error` (the runtime failed). The message deliberately carries no raw error detail.
 
+### `session.ended`
+
+```json session.ended
+{ "type": "session.ended", "reason": "conversation_timeout" }
+```
+
+Sent once, right before the server ends the call (before the agent leaves the room or the room is deleted), so a client learns the cause instead of inferring it from the disconnect. `reason` is `user_hangup` (the user hung up, or a backend ended the session through the API), `agent_hangup` (the agent hung up or the workflow reached an end node), `conversation_timeout` (the session reached its maximum duration), or `escalated` (the call was transferred to a human). The values match `end_reason` on the [session record](/agents/monitor/conversation-history#status-and-end-reason); treat the set as open, per the [compatibility rules](#compatibility-rules). A call that drops without this message has no announced reason: the SDKs report `connection_lost` once reconnection fails.
+
 ## Client events: `client-event`
 
 Publish these on the `client-event` topic. The agent ignores malformed JSON and unknown types.
diff --git a/agents/deploy/web-sdk.mdx b/agents/deploy/web-sdk.mdx
index 275cfca..6962b02 100644
--- a/agents/deploy/web-sdk.mdx
+++ b/agents/deploy/web-sdk.mdx
@@ -105,11 +105,15 @@ connecting → connected ⇄ reconnecting → ended(reason)
 
 When the session ends, `disconnect` fires with a reason (also available as `session.endReason`):
 
-| `EndReason`       | Meaning                                                                                                                                                                                                                        |
-| ----------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
-| `user_hangup`     | You called `session.end()`, or the user left the page                                                                                                                                                                          |
-| `agent_hangup`    | The server ended the session: the agent hung up (for example via the hang-up [system tool](/agents/build/system-tools)), the session hit its maximum duration, or it was force-ended; the protocol does not distinguish these |
-| `connection_lost` | The connection dropped and could not be recovered, or the agent never joined                                                                                                                                                   |
+| `EndReason`            | Meaning                                                                                                                                                          |
+| ---------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| `user_hangup`          | You called `session.end()`, the user left the page, or your backend [ended the session](/agents/deploy/authenticated-sessions#ending-sessions-from-your-backend) |
+| `agent_hangup`         | The agent ended the call: the hang-up [system tool](/agents/build/system-tools), a workflow end node, or an idle hangup                                          |
+| `conversation_timeout` | The session reached the agent's [maximum duration](/agents/build/configuration#call-duration)                                                                    |
+| `escalated`            | The call was transferred to a human                                                                                                                              |
+| `connection_lost`      | The connection dropped and could not be recovered, the agent never joined, or the call ended before the server could say why                                     |
+
+Every reason except `connection_lost` comes from the server: it sends the protocol's [`session.ended` event](/agents/deploy/protocol#session-ended) just before tearing the call down, and the values match `end_reason` on the [session record](/agents/monitor/conversation-history#status-and-end-reason), so your client and your backend agree about how a session ended. This needs `@fishaudio/agent-client` 0.3.0 or later; older clients infer the reason from the disconnect and report every server-side end as `agent_hangup`.
 
 Brief network drops don't end the session: the SDK moves to `reconnecting` and back to `connected` automatically, reusing the same session. It never creates a new session, so you never need a new token mid-call.