diff --git a/crates/didbot-agentd/src/protocol.rs b/crates/didbot-agentd/src/protocol.rs
index 1d3007fe..1147f9ab 100644
--- a/crates/didbot-agentd/src/protocol.rs
+++ b/crates/didbot-agentd/src/protocol.rs
@@ -20,7 +20,12 @@ use serde::{Deserialize, Serialize};
 pub const VERSION: u32 = 1;
 
 /// What each caller wants.
-#[derive(Debug, Clone, Serialize, Deserialize)]
+///
+/// Serialized with an `asks` tag. Read without needing one: a sender that
+/// predates the tag is asking the only thing there was to ask, and refusing
+/// it would make every adapter update a flag day. That is the skew [`VERSION`]
+/// exists to survive, and a missing tag is the cheapest kind.
+#[derive(Debug, Clone, Serialize)]
 #[serde(tag = "asks", rename_all = "snake_case")]
 pub enum Message {
     /// A hook saying what the harness just did.
@@ -29,6 +34,24 @@ pub enum Message {
     Confirm(Confirm),
 }
 
+impl<'de> Deserialize<'de> for Message {
+    fn deserialize<D: serde::Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
+        use serde::de::Error;
+        let value = serde_json::Value::deserialize(deserializer)?;
+        match value.get("asks").and_then(serde_json::Value::as_str) {
+            None | Some("report") => serde_json::from_value(value)
+                .map(Message::Report)
+                .map_err(D::Error::custom),
+            Some("confirm") => serde_json::from_value(value)
+                .map(Message::Confirm)
+                .map_err(D::Error::custom),
+            Some(other) => Err(D::Error::custom(format!(
+                "this daemon does not know how to `{other}`"
+            ))),
+        }
+    }
+}
+
 /// What the adapter observed, in the vocabulary the daemon works in.
 ///
 /// Deliberately not the harness's own event names: the daemon has no opinion
@@ -198,6 +221,26 @@ mod tests {
         );
     }
 
+    #[test]
+    fn a_sender_that_predates_the_tag_is_still_read() {
+        // What every adapter sent before there was more than one thing to ask.
+        let line = r#"{"version":1,"observed":"acted","session":"s1","context":"a1"}"#;
+        let message: Message = serde_json::from_str(line).unwrap();
+        let Message::Report(report) = message else {
+            panic!("a report");
+        };
+        assert_eq!(report.observed, Observed::Acted);
+    }
+
+    #[test]
+    fn something_this_daemon_cannot_do_is_named_rather_than_guessed() {
+        let line = r#"{"asks":"revoke","version":1}"#;
+        let err = serde_json::from_str::<Message>(line)
+            .unwrap_err()
+            .to_string();
+        assert!(err.contains("revoke"), "{err}");
+    }
+
     #[test]
     fn an_unknown_observation_is_refused_rather_than_guessed() {
         let line = r#"{"asks":"report","version":1,"observed":"vanished","session":"s1"}"#;