refactor(agents): absorb overflow, retry, and matcher duplicates into the failover substrate (#121817)

* refactor(ai): centralize context overflow matching

* refactor(agents): add retry evidence and guarded status facets

* refactor(agents): absorb assistant retry and key matchers

* chore(plugin-sdk): refresh failover closure hashes

* fix(agents): consume retry evidence at altitude zero

* test(agents): narrow retry corpus provider fixtures

* test(agents): keep retry corpus sorting immutable

src/shared/assistant-error-format.test.ts

@@ -1,5 +1,6 @@
 import { describe, expect, it } from "vitest";
 import {
+  extractErrorHttpStatus,
   extractLeadingHttpStatus,
   extractProviderWrappedHttpStatus,
   formatRawAssistantErrorForUi,
@@ -58,6 +59,27 @@ describe("extractProviderWrappedHttpStatus", () => {
   });
 });
 
+describe("extractErrorHttpStatus", () => {
+  it.each([
+    ["HTTP 429 too many requests", 429],
+    ["OpenAI API error (500): upstream failed", 500],
+    ["error, status code: 400, message: invalid request", 400],
+    ["unexpected status 503 from upstream", 503],
+    ["Error: HTTP status: 504, gateway timeout", 504],
+  ])("extracts guarded status from %s", (message, code) => {
+    expect(extractErrorHttpStatus(message)?.code).toBe(code);
+  });
+
+  it.each([
+    "request id req-4291 failed",
+    "input length 14295 tokens exceeds the model limit",
+    "model model-x-500-preview not found",
+    "Image width 500 exceeds the maximum allowed size",
+  ])("rejects embedded numeric text: %s", (message) => {
+    expect(extractErrorHttpStatus(message)).toBeNull();
+  });
+});
+
 describe("HTTP status consumers", () => {
   it("formats only status lines inside the HTTP range", () => {
     expect(formatRawAssistantErrorForUi("100 Continue")).toBe("HTTP 100: Continue");

src/shared/assistant-error-format.ts

@@ -16,6 +16,9 @@ const HTTP_STATUS_CODE_PREFIX_RE = new RegExp(
 // like model ids or image dimensions never become fake HTTP statuses.
 const PROVIDER_WRAPPED_HTTP_STATUS_RE =
   /^(?:[a-z][\w-]*(?:\s+[a-z][\w-]*){0,3}\s+)?api\s*error\s*\((\d{3})\)(?:\s*:\s*([\s\S]*))?$/i;
+const LABELED_HTTP_STATUS_RE =
+  /^(?:status code|unexpected status|http status)\s*[:=]?\s*(\d{3})\b(?:\s*[:,]?\s*(?:message\s*:\s*)?([\s\S]*))?$/i;
+const ERROR_STATUS_ENVELOPE_RE = /^error\s*[:,]\s*/i;
 const HTML_ERROR_PREFIX_RE = /^\s*(?:<!doctype\s+html\b|<html\b)/i;
 const HTML_CLOSE_RE = /<\/html>/i;
 const CLOUDFLARE_HTML_ERROR_CODES = new Set([521, 522, 523, 524, 525, 526, 530]);
@@ -122,6 +125,27 @@ export function extractProviderWrappedHttpStatus(
   return extractHttpStatusMatch(raw.match(PROVIDER_WRAPPED_HTTP_STATUS_RE));
 }
 
+/** Extract an explicitly labeled provider HTTP status without matching embedded numeric text. */
+export function extractErrorHttpStatus(raw: string): { code: number; rest: string } | null {
+  const trimmed = raw.trim();
+  const direct =
+    extractLeadingHttpStatus(trimmed) ??
+    extractProviderWrappedHttpStatus(trimmed) ??
+    extractHttpStatusMatch(trimmed.match(LABELED_HTTP_STATUS_RE));
+  if (direct) {
+    return direct;
+  }
+  const unwrapped = trimmed.replace(ERROR_STATUS_ENVELOPE_RE, "");
+  if (unwrapped === trimmed) {
+    return null;
+  }
+  return (
+    extractLeadingHttpStatus(unwrapped) ??
+    extractProviderWrappedHttpStatus(unwrapped) ??
+    extractHttpStatusMatch(unwrapped.match(LABELED_HTTP_STATUS_RE))
+  );
+}
+
 export function isCloudflareOrHtmlErrorPage(raw: string): boolean {
   const trimmed = raw.trim();
   if (!trimmed) {