fix(provider): retry anthropic overloaded errors (SSE event + HTTP 529) (#2595)

Author: tusharmath

crates/forge_domain/src/retry_config.rs

@@ -42,7 +42,7 @@ impl Default for RetryConfig {
             min_delay_ms: 1000,
             backoff_factor: 2,
             max_retry_attempts: 8,
-            retry_status_codes: vec![429, 500, 502, 503, 504, 408, 522, 520],
+            retry_status_codes: vec![429, 500, 502, 503, 504, 408, 522, 520, 529],
             max_delay: None,
             suppress_retry_errors: false,
         }
@@ -71,7 +71,7 @@ mod tests {
         assert_eq!(config.max_retry_attempts, 8);
         assert_eq!(
             config.retry_status_codes,
-            vec![429, 500, 502, 503, 504, 408, 522, 520]
+            vec![429, 500, 502, 503, 504, 408, 522, 520, 529]
         );
         assert_eq!(config.suppress_retry_errors, false);
     }

crates/forge_repo/src/provider/openai_responses/repository.rs

@@ -1082,7 +1082,7 @@ mod tests {
 
         assert_eq!(
             repo.retry_config.retry_status_codes,
-            vec![429, 500, 502, 503, 504, 408, 522, 520]
+            vec![429, 500, 502, 503, 504, 408, 522, 520, 529]
         );
     }
 

crates/forge_repo/src/provider/retry.rs

@@ -1,4 +1,5 @@
 use forge_app::domain::{Error as DomainError, RetryConfig};
+use forge_app::dto::anthropic::Error as AnthropicError;
 use forge_app::dto::openai::{Error, ErrorResponse};
 
 const TRANSPORT_ERROR_CODES: [&str; 3] = ["ERR_STREAM_PREMATURE_CLOSE", "ECONNRESET", "ETIMEDOUT"];
@@ -16,13 +17,22 @@ pub fn into_retry(error: anyhow::Error, retry_config: &RetryConfig) -> anyhow::E
         || is_req_transport_error(&error)
         || is_event_transport_error(&error)
         || is_empty_error(&error)
+        || is_anthropic_overloaded_error(&error)
     {
         return DomainError::Retryable(error).into();
     }
 
     error
 }
 
+/// Checks if the error is an Anthropic `overloaded_error`, which arrives as an
+/// SSE event payload rather than an HTTP status code and must be retried.
+fn is_anthropic_overloaded_error(error: &anyhow::Error) -> bool {
+    error
+        .downcast_ref::<AnthropicError>()
+        .is_some_and(|e| matches!(e, AnthropicError::OverloadedError { .. }))
+}
+
 fn get_api_status_code(error: &anyhow::Error) -> Option<u16> {
     error.downcast_ref::<Error>().and_then(|error| match error {
         Error::Response(error) => error
@@ -294,6 +304,21 @@ mod tests {
         assert!(get_event_req_status_code(&error).is_none());
     }
 
+    #[test]
+    fn test_anthropic_overloaded_error_is_retryable() {
+        let retry_config = fixture_retry_config(vec![]);
+
+        // overloaded_error arriving as an SSE event must be retried
+        let error = anyhow::Error::from(AnthropicError::OverloadedError {
+            message: "Overloaded".to_string(),
+        });
+        assert!(is_retryable(into_retry(error, &retry_config)));
+
+        // Generic errors are still not retryable
+        let error = anyhow!("Generic error");
+        assert!(!is_retryable(into_retry(error, &retry_config)));
+    }
+
     #[tokio::test]
     async fn test_incomplete_message_is_retryable() {
         use tokio::net::TcpListener;