Q69: provider failures classify by status and code; cooldowns follow Retry-After or back off

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/main/services/provider-failure.ts

@@ -0,0 +1,37 @@
+import { isTransientProviderFailure } from "../../shared/provider-runtime-domain";
+import { ProviderHttpError } from "./provider-http";
+
+/** Whether a failed call is the provider's passing trouble, and how long it asked us to wait. */
+export interface ProviderFailure {
+  transient: boolean;
+  retryAfterMs: number | null;
+}
+
+/** Request timeout, too early, rate limited; every 5xx (server, gateway, Cloudflare 52x, Anthropic 529 overload) is transient too. */
+const TRANSIENT_STATUSES = new Set([408, 425, 429]);
+/** Connection-level failures from Node's fetch (undici) and sockets. */
+const TRANSIENT_CODES = new Set([
+  "ECONNRESET", "ETIMEDOUT", "ECONNREFUSED", "EAI_AGAIN", "EPIPE",
+  "UND_ERR_SOCKET", "UND_ERR_CONNECT_TIMEOUT", "UND_ERR_HEADERS_TIMEOUT", "UND_ERR_BODY_TIMEOUT",
+]);
+
+/** Classifies by status, timeout and network error code first; the message text is the last resort. */
+export function classifyProviderFailure(error: unknown, now: number): ProviderFailure {
+  if (error instanceof ProviderHttpError) {
+    const state = error.rateLimitState;
+    const resetIn = state?.resetAt ? Date.parse(state.resetAt) - now : null;
+    const retryAfterMs = state?.retryAfterMs ?? (resetIn !== null && resetIn > 0 ? resetIn : null);
+    if (error.timedOut || (error.status !== null && (TRANSIENT_STATUSES.has(error.status) || (error.status >= 500 && error.status < 600)))) return { transient: true, retryAfterMs };
+    if (error.status !== null) return { transient: isTransientProviderFailure(error.message), retryAfterMs };
+  }
+  if (TRANSIENT_CODES.has(errorCode(error) ?? "")) return { transient: true, retryAfterMs: null };
+  return { transient: isTransientProviderFailure(error instanceof Error ? error.message : String(error)), retryAfterMs: null };
+}
+
+function errorCode(error: unknown): string | null {
+  if (!(error instanceof Error)) return null;
+  const own = (error as NodeJS.ErrnoException).code;
+  if (typeof own === "string") return own;
+  const cause = (error as Error & { cause?: unknown }).cause;
+  return cause instanceof Error ? errorCode(cause) : null;
+}