diff --git a/crates/protocol/tests/parity_protocol.rs b/crates/protocol/tests/parity_protocol.rs
index 0b6f082d..1a05026e 100644
--- a/crates/protocol/tests/parity_protocol.rs
+++ b/crates/protocol/tests/parity_protocol.rs
@@ -64,6 +64,7 @@ fn runtime_event_envelope_roundtrip() {
         "turn_id": "turn_456",
         "item_id": "item_789",
         "timestamp": "2026-02-11T20:18:49.123Z",
+        "created_at": "2026-02-11T20:18:49.123Z",
         "payload": { "delta": "ok", "kind": "agent_message" },
     });
     let envelope: RuntimeEventEnvelope =
@@ -76,7 +77,17 @@ fn runtime_event_envelope_roundtrip() {
 
     let encoded = serde_json::to_value(&envelope).expect("serialize runtime event envelope");
     assert_eq!(encoded["event"], encoded["kind"]);
+    assert_eq!(encoded["schema_version"], 1);
     assert_eq!(encoded["seq"], 12);
+    assert_eq!(encoded["thread_id"], "thr_123");
+    assert_eq!(encoded["turn_id"], "turn_456");
+    assert_eq!(encoded["item_id"], "item_789");
+    assert_eq!(encoded["timestamp"], "2026-02-11T20:18:49.123Z");
+    assert_eq!(encoded["created_at"], "2026-02-11T20:18:49.123Z");
+    assert_eq!(
+        encoded["payload"],
+        json!({ "delta": "ok", "kind": "agent_message" })
+    );
 }
 
 #[test]
diff --git a/crates/tui/src/runtime_api.rs b/crates/tui/src/runtime_api.rs
index 4eb3aff5..1b8d9fff 100644
--- a/crates/tui/src/runtime_api.rs
+++ b/crates/tui/src/runtime_api.rs
@@ -2779,7 +2779,6 @@ mod tests {
             seq_b > seq_a,
             "expected seq after cursor: {seq_b} <= {seq_a}"
         );
-        assert_eq!(payload_b["thread_id"], thread_id);
 
         handle.abort();
         Ok(())
diff --git a/docs/RUNTIME_API.md b/docs/RUNTIME_API.md
index 8e5d5b2e..d57960bd 100644
--- a/docs/RUNTIME_API.md
+++ b/docs/RUNTIME_API.md
@@ -314,8 +314,9 @@ Compatibility notes:
 - `kind` mirrors `event` in the stable envelope for typed clients.
 - `thread.started`, `turn.started`, and `turn.completed` are emitted as SSE event
   names exactly as before.
-- `created_at` is currently a duplicate of `timestamp` (`timestamp` is the existing
-  canonical field).
+- `timestamp` remains the canonical event time for schema version 1. `created_at`
+  is an equivalent alias for clients that use `created_at` naming elsewhere; do
+  not require both fields to be present.
 
 Common event names: `thread.started`, `thread.forked`, `turn.started`,
 `turn.lifecycle`, `turn.steered`, `turn.interrupt_requested`,