fix(failover): classify HTTP 402 as rate_limit when payload indicates usage limit (#30484) (#36802)

* fix(failover): classify HTTP 402 as rate_limit when payload indicates usage limit (#30484)

Some providers (notably Anthropic Claude Max plan) surface temporary
usage/rate-limit failures as HTTP 402 instead of 429. Before this change,
all 402s were unconditionally mapped to 'billing', which produced a
misleading 'run out of credits' warning for Max plan users who simply
hit their usage window.

This follows the same pattern introduced for HTTP 400 in #36783: check
the error message for an explicit rate-limit signal before falling back
to the default status-code classification.

- classifyFailoverReasonFromHttpStatus now returns 'rate_limit' for 402
  when isRateLimitErrorMessage matches the payload text
- Added regression tests covering both the rate-limit and billing paths
  on 402

* fix: narrow 402 rate-limit matcher to prevent billing misclassification

The original implementation used isRateLimitErrorMessage(), which matches
phrases like 'quota exceeded' that legitimately appear in billing errors.

This commit replaces it with a narrow, 402-specific matcher that requires
BOTH retry language (try again/retry/temporary/cooldown) AND limit
terminology (usage limit/rate limit/organization usage).

Prevents misclassification of errors like:
'HTTP 402: exceeded quota, please add credits' -> billing (not rate_limit)

Added regression test for the ambiguous case.

---------

Co-authored-by: Val Alexander <bunsthedev@gmail.com>

src/agents/failover-error.test.ts

@@ -41,6 +41,27 @@ const GROQ_SERVICE_UNAVAILABLE_MESSAGE =
 describe("failover-error", () => {
   it("infers failover reason from HTTP status", () => {
     expect(resolveFailoverReasonFromError({ status: 402 })).toBe("billing");
+    // Anthropic Claude Max plan surfaces rate limits as HTTP 402 (#30484)
+    expect(
+      resolveFailoverReasonFromError({
+        status: 402,
+        message: "HTTP 402: request reached organization usage limit, try again later",
+      }),
+    ).toBe("rate_limit");
+    // Explicit billing messages on 402 stay classified as billing
+    expect(
+      resolveFailoverReasonFromError({
+        status: 402,
+        message: "insufficient credits — please top up your account",
+      }),
+    ).toBe("billing");
+    // Ambiguous "quota exceeded" + billing signal → billing wins
+    expect(
+      resolveFailoverReasonFromError({
+        status: 402,
+        message: "HTTP 402: You have exceeded your current quota. Please add more credits.",
+      }),
+    ).toBe("billing");
     expect(resolveFailoverReasonFromError({ statusCode: "429" })).toBe("rate_limit");
     expect(resolveFailoverReasonFromError({ status: 403 })).toBe("auth");
     expect(resolveFailoverReasonFromError({ status: 408 })).toBe("timeout");

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

@@ -261,6 +261,24 @@ export function classifyFailoverReasonFromHttpStatus(
   }
 
   if (status === 402) {
+    // Some providers (e.g. Anthropic Claude Max plan) surface temporary
+    // usage/rate-limit failures as HTTP 402. Use a narrow matcher for
+    // temporary limits to avoid misclassifying billing failures (#30484).
+    if (message) {
+      const lower = message.toLowerCase();
+      // Temporary usage limit signals: retry language + usage/limit terminology
+      const hasTemporarySignal =
+        (lower.includes("try again") ||
+          lower.includes("retry") ||
+          lower.includes("temporary") ||
+          lower.includes("cooldown")) &&
+        (lower.includes("usage limit") ||
+          lower.includes("rate limit") ||
+          lower.includes("organization usage"));
+      if (hasTemporarySignal) {
+        return "rate_limit";
+      }
+    }
     return "billing";
   }
   if (status === 429) {