fix: treat provider-unavailable errors as failover-eligible

OpenRouter returns 404 "No endpoints found that support tool use" when
no provider endpoint supports the requested parameters (e.g. tools).
This was not recognized as a failover reason, so configured fallback
models were never tried.

Add `provider_unavailable` to FailoverReason and match patterns like
"no endpoints found" and "model is currently unavailable" so the
fallback chain proceeds to the next candidate model.

Closes #XXXX

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/agents/auth-profiles/types.ts

@@ -37,6 +37,7 @@ export type AuthProfileFailureReason =
   | "rate_limit"
   | "billing"
   | "timeout"
+  | "provider_unavailable"
   | "unknown";
 
 /** Per-profile usage statistics for round-robin and cooldown tracking */

src/agents/failover-error.test.ts

@@ -47,6 +47,38 @@ describe("failover-error", () => {
     expect(err?.status).toBe(400);
   });
 
+  it("infers provider_unavailable from OpenRouter no-endpoints error", () => {
+    expect(
+      resolveFailoverReasonFromError({
+        status: 404,
+        message: "No endpoints found that support tool use",
+      }),
+    ).toBe("provider_unavailable");
+  });
+
+  it("infers provider_unavailable from model-unavailable messages", () => {
+    expect(
+      resolveFailoverReasonFromError({
+        message: "model is currently unavailable",
+      }),
+    ).toBe("provider_unavailable");
+    expect(
+      resolveFailoverReasonFromError({
+        message: "model not available for this request",
+      }),
+    ).toBe("provider_unavailable");
+  });
+
+  it("coerces provider_unavailable errors with a 404 status", () => {
+    const err = coerceToFailoverError(
+      { message: "No endpoints found that support tool use", status: 404 },
+      { provider: "openrouter", model: "deepseek/deepseek-chat-v3-0324" },
+    );
+    expect(err?.reason).toBe("provider_unavailable");
+    expect(err?.status).toBe(404);
+    expect(err?.provider).toBe("openrouter");
+  });
+
   it("describes non-Error values consistently", () => {
     const described = describeFailoverError(123);
     expect(described.message).toBe("123");

src/agents/failover-error.ts

@@ -50,6 +50,8 @@ export function resolveFailoverStatus(reason: FailoverReason): number | undefine
       return 408;
     case "format":
       return 400;
+    case "provider_unavailable":
+      return 404;
     default:
       return undefined;
   }

src/agents/pi-embedded-helpers.classifyfailoverreason.test.ts

@@ -38,4 +38,16 @@ describe("classifyFailoverReason", () => {
       "rate_limit",
     );
   });
+  it("classifies OpenRouter no-endpoints errors as provider_unavailable", () => {
+    expect(classifyFailoverReason("No endpoints found that support tool use")).toBe(
+      "provider_unavailable",
+    );
+    expect(classifyFailoverReason("No endpoints found that support this request")).toBe(
+      "provider_unavailable",
+    );
+  });
+  it("classifies model-unavailable errors as provider_unavailable", () => {
+    expect(classifyFailoverReason("model is currently unavailable")).toBe("provider_unavailable");
+    expect(classifyFailoverReason("model not available")).toBe("provider_unavailable");
+  });
 });

src/agents/pi-embedded-helpers/errors.ts

@@ -396,6 +396,12 @@ const ERROR_PATTERNS = {
     "messages.1.content.1.tool_use.id",
     "invalid request format",
   ],
+  providerUnavailable: [
+    "no endpoints found",
+    /no .* endpoints? available/,
+    "model is currently unavailable",
+    "model not available",
+  ],
 } as const;
 
 const IMAGE_DIMENSION_ERROR_RE =
@@ -496,6 +502,10 @@ export function isAuthAssistantError(msg: AssistantMessage | undefined): boolean
   return isAuthErrorMessage(msg.errorMessage ?? "");
 }
 
+export function isProviderUnavailableErrorMessage(raw: string): boolean {
+  return matchesErrorPatterns(raw, ERROR_PATTERNS.providerUnavailable);
+}
+
 export function classifyFailoverReason(raw: string): FailoverReason | null {
   if (isImageDimensionErrorMessage(raw)) return null;
   if (isImageSizeError(raw)) return null;
@@ -505,6 +515,7 @@ export function classifyFailoverReason(raw: string): FailoverReason | null {
   if (isBillingErrorMessage(raw)) return "billing";
   if (isTimeoutErrorMessage(raw)) return "timeout";
   if (isAuthErrorMessage(raw)) return "auth";
+  if (isProviderUnavailableErrorMessage(raw)) return "provider_unavailable";
   return null;
 }
 

src/agents/pi-embedded-helpers/types.ts

@@ -1,3 +1,10 @@
 export type EmbeddedContextFile = { path: string; content: string };
 
-export type FailoverReason = "auth" | "format" | "rate_limit" | "billing" | "timeout" | "unknown";
+export type FailoverReason =
+  | "auth"
+  | "format"
+  | "rate_limit"
+  | "billing"
+  | "timeout"
+  | "provider_unavailable"
+  | "unknown";