fix(nats): delete+recreate stream when retention policy is incompatible

crates/adapters/nats/src/lib.rs

@@ -19,25 +19,28 @@ fn stream_config() -> StreamConfig {
     }
 }
 
-/// Ensure the JetStream stream exists and has the current subject list.
-/// Idempotent — creates if absent, updates subjects if already present.
+/// Ensure the JetStream stream exists with the current config.
+/// If an incompatible stream exists (e.g. wrong retention policy), deletes and recreates it.
 pub async fn ensure_stream(client: &async_nats::Client) -> Result<(), DomainError> {
     let js = jetstream::new(client.clone());
-    // Try to update first (covers the case where stream exists with stale subjects).
-    // Falls back to create if the stream doesn't exist yet.
-    match js.update_stream(stream_config()).await {
-        Ok(_) => {
-            tracing::info!(subject = STREAM_SUBJECT, "JetStream stream updated");
-            Ok(())
-        }
-        Err(e) => {
-            tracing::warn!("JetStream stream update failed ({e}), falling back to get_or_create");
-            js.get_or_create_stream(stream_config())
-                .await
-                .map(|_| ())
-                .map_err(|e| DomainError::Internal(format!("JetStream stream setup failed: {e}")))
-        }
+
+    // Happy path: stream exists and config is compatible.
+    if js.update_stream(stream_config()).await.is_ok() {
+        tracing::info!(subject = STREAM_SUBJECT, "JetStream stream updated");
+        return Ok(());
     }
+
+    // Update failed — retention policy mismatch or other incompatibility.
+    // Delete the old stream and recreate with current config.
+    tracing::warn!(
+        "JetStream stream update failed (incompatible config), deleting '{STREAM_NAME}' and recreating"
+    );
+    let _ = js.delete_stream(STREAM_NAME).await;
+
+    js.create_stream(stream_config())
+        .await
+        .map(|_| ())
+        .map_err(|e| DomainError::Internal(format!("JetStream stream create failed: {e}")))
 }
 
 // ── NatsTransport — JetStream publish ──────────────────────────────────────