fix(ai): retry Cloudflare 520 responses

closes #9627

packages/ai/CHANGELOG.md

@@ -24,6 +24,7 @@
 - Fixed Mistral-hosted GLM-5.2 reasoning requests to use `reasoning_effort` instead of the ignored `prompt_mode` ([#9375](https://github.com/earendil-works/pi/issues/9375)).
 - Fixed OpenAI-compatible Responses errors to identify the actual provider instead of always labeling them as OpenAI errors ([#9298](https://github.com/earendil-works/pi/issues/9298)).
 - Fixed Baseten requests to send session-affinity headers from `sessionId` for automatic prompt-cache routing ([#9629](https://github.com/earendil-works/pi/issues/9629)).
+- Fixed retry classification for Cloudflare 520 responses ([#9627](https://github.com/earendil-works/pi/issues/9627)).
 
 ## [0.85.1] - 2026-09-05
 

packages/ai/src/utils/retry.ts

@@ -33,6 +33,7 @@ const RETRYABLE_PROVIDER_ERROR_PATTERN = buildProviderErrorPattern([
 	"502",
 	"503",
 	"504",
+	"520",
 	"524",
 	"service.?unavailable",
 	"server.?error",

packages/ai/test/retry.test.ts

@@ -80,6 +80,12 @@ describe("provider retry classification", () => {
 		expect(
 			isRetryableAssistantError(fauxAssistantMessage("", { stopReason: "error", errorMessage: "overloaded_error" })),
 		).toBe(true);
+		// Regression for #9627.
+		expect(
+			isRetryableAssistantError(
+				fauxAssistantMessage("", { stopReason: "error", errorMessage: "520 status code (no body)" }),
+			),
+		).toBe(true);
 		expect(
 			isRetryableAssistantError(
 				fauxAssistantMessage("", { stopReason: "error", errorMessage: "524 status code (no body)" }),