diff --git a/actions/setup/js/check_workflow_timestamp_api.cjs b/actions/setup/js/check_workflow_timestamp_api.cjs
index beabdbf49f5..45ab8befddb 100644
--- a/actions/setup/js/check_workflow_timestamp_api.cjs
+++ b/actions/setup/js/check_workflow_timestamp_api.cjs
@@ -20,7 +20,7 @@ const path = require("path");
 const { getErrorMessage } = require("./error_helpers.cjs");
 const { extractHashFromLockFile, extractBodyHashFromLockFile, computeFrontmatterHash, computeBodyHash, createGitHubFileReader } = require("./frontmatter_hash_pure.cjs");
 const { getFileContent } = require("./github_api_helpers.cjs");
-const { ERR_CONFIG } = require("./error_codes.cjs");
+const { ERR_CONFIG, SAFE_OUTPUT_E009, CONFIG_HASH_MISMATCH } = require("./error_codes.cjs");
 
 // Matches GitHub workflow ref paths of the form "owner/repo/...[@ref]"
 // and captures: [1] owner, [2] repo, [3] optional ref
@@ -423,7 +423,7 @@ async function main() {
     await summary.write();
 
     core.setOutput("stale_lock_file_failed", "true");
-    core.setFailed(`${ERR_CONFIG}: ${warningMessage}`);
+    core.setFailed(`${ERR_CONFIG}: ${SAFE_OUTPUT_E009} ${CONFIG_HASH_MISMATCH}: ${warningMessage}`);
   } else if (hashComparison.match) {
     // Hashes match - lock file is up to date
     core.info("✅ Lock file is up to date (hashes match)");
@@ -450,7 +450,7 @@ async function main() {
     core.setOutput("stale_lock_file_failed", "true");
 
     // Fail the step to prevent workflow from running with outdated configuration
-    core.setFailed(`${ERR_CONFIG}: ${warningMessage}`);
+    core.setFailed(`${ERR_CONFIG}: ${SAFE_OUTPUT_E009} ${CONFIG_HASH_MISMATCH}: ${warningMessage}`);
   }
 }
 
diff --git a/actions/setup/js/check_workflow_timestamp_api.test.cjs b/actions/setup/js/check_workflow_timestamp_api.test.cjs
index f93d1dcff13..de7c5834063 100644
--- a/actions/setup/js/check_workflow_timestamp_api.test.cjs
+++ b/actions/setup/js/check_workflow_timestamp_api.test.cjs
@@ -173,6 +173,8 @@ model: claude-sonnet-4
       await main();
 
       expect(mockCore.setFailed).toHaveBeenCalledWith(expect.stringContaining("Lock file"));
+      expect(mockCore.setFailed).toHaveBeenCalledWith(expect.stringContaining("E009"));
+      expect(mockCore.setFailed).toHaveBeenCalledWith(expect.stringContaining("CONFIG_HASH_MISMATCH"));
       expect(mockCore.setFailed).toHaveBeenCalledWith(expect.stringContaining("is outdated"));
       expect(mockCore.setFailed).toHaveBeenCalledWith(expect.stringContaining("frontmatter has changed"));
       expect(mockCore.setFailed).toHaveBeenCalledWith(expect.stringContaining("gh aw compile"));
@@ -241,6 +243,8 @@ jobs:
       await main();
 
       expect(mockCore.warning).toHaveBeenCalledWith(expect.stringContaining("Could not compare frontmatter hashes"));
+      expect(mockCore.setFailed).toHaveBeenCalledWith(expect.stringContaining("E009"));
+      expect(mockCore.setFailed).toHaveBeenCalledWith(expect.stringContaining("CONFIG_HASH_MISMATCH"));
       expect(mockCore.setFailed).toHaveBeenCalledWith(expect.stringContaining("is outdated"));
       expect(mockCore.summary.addRaw).toHaveBeenCalled();
       expect(mockCore.summary.write).toHaveBeenCalled();
diff --git a/actions/setup/js/error_codes.cjs b/actions/setup/js/error_codes.cjs
index a7260c71f4d..3fd758187eb 100644
--- a/actions/setup/js/error_codes.cjs
+++ b/actions/setup/js/error_codes.cjs
@@ -45,9 +45,21 @@ const ERR_SYSTEM = "ERR_SYSTEM";
 /** @type {string} Safe output validation/input errors (legacy numeric taxonomy) */
 const SAFE_OUTPUT_E001 = "E001";
 
+/** @type {string} Safe output lock file frontmatter hash mismatch (legacy numeric taxonomy) */
+const SAFE_OUTPUT_E009 = "E009";
+
+/** @type {string} Safe output retry exhaustion due to rate limiting (legacy numeric taxonomy) */
+const SAFE_OUTPUT_E010 = "E010";
+
 /** @type {string} Safe output operation/runtime failures (legacy numeric taxonomy) */
 const SAFE_OUTPUT_E099 = "E099";
 
+/** @type {string} Named code for lock file frontmatter hash mismatch */
+const CONFIG_HASH_MISMATCH = "CONFIG_HASH_MISMATCH";
+
+/** @type {string} Named code for rate limit retry exhaustion */
+const RATE_LIMIT_EXCEEDED = "RATE_LIMIT_EXCEEDED";
+
 module.exports = {
   ERR_VALIDATION,
   ERR_PERMISSION,
@@ -57,5 +69,9 @@ module.exports = {
   ERR_PARSE,
   ERR_SYSTEM,
   SAFE_OUTPUT_E001,
+  SAFE_OUTPUT_E009,
+  SAFE_OUTPUT_E010,
   SAFE_OUTPUT_E099,
+  CONFIG_HASH_MISMATCH,
+  RATE_LIMIT_EXCEEDED,
 };
diff --git a/actions/setup/js/error_codes.test.cjs b/actions/setup/js/error_codes.test.cjs
index fbd589095e2..edaec1b0474 100644
--- a/actions/setup/js/error_codes.test.cjs
+++ b/actions/setup/js/error_codes.test.cjs
@@ -1,6 +1,20 @@
 // @ts-check
 import { describe, it, expect } from "vitest";
-const { ERR_VALIDATION, ERR_PERMISSION, ERR_API, ERR_CONFIG, ERR_NOT_FOUND, ERR_PARSE, ERR_SYSTEM, SAFE_OUTPUT_E001, SAFE_OUTPUT_E099 } = require("./error_codes.cjs");
+const {
+  ERR_VALIDATION,
+  ERR_PERMISSION,
+  ERR_API,
+  ERR_CONFIG,
+  ERR_NOT_FOUND,
+  ERR_PARSE,
+  ERR_SYSTEM,
+  SAFE_OUTPUT_E001,
+  SAFE_OUTPUT_E009,
+  SAFE_OUTPUT_E010,
+  SAFE_OUTPUT_E099,
+  CONFIG_HASH_MISMATCH,
+  RATE_LIMIT_EXCEEDED,
+} = require("./error_codes.cjs");
 
 describe("error_codes", () => {
   describe("module exports", () => {
@@ -13,11 +27,15 @@ describe("error_codes", () => {
       expect(ERR_PARSE).toBeDefined();
       expect(ERR_SYSTEM).toBeDefined();
       expect(SAFE_OUTPUT_E001).toBeDefined();
+      expect(SAFE_OUTPUT_E009).toBeDefined();
+      expect(SAFE_OUTPUT_E010).toBeDefined();
       expect(SAFE_OUTPUT_E099).toBeDefined();
+      expect(CONFIG_HASH_MISMATCH).toBeDefined();
+      expect(RATE_LIMIT_EXCEEDED).toBeDefined();
     });
 
     it("exports string values only", () => {
-      const codes = [ERR_VALIDATION, ERR_PERMISSION, ERR_API, ERR_CONFIG, ERR_NOT_FOUND, ERR_PARSE, ERR_SYSTEM, SAFE_OUTPUT_E001, SAFE_OUTPUT_E099];
+      const codes = [ERR_VALIDATION, ERR_PERMISSION, ERR_API, ERR_CONFIG, ERR_NOT_FOUND, ERR_PARSE, ERR_SYSTEM, SAFE_OUTPUT_E001, SAFE_OUTPUT_E009, SAFE_OUTPUT_E010, SAFE_OUTPUT_E099, CONFIG_HASH_MISMATCH, RATE_LIMIT_EXCEEDED];
       for (const code of codes) {
         expect(typeof code).toBe("string");
       }
@@ -59,9 +77,25 @@ describe("error_codes", () => {
       expect(SAFE_OUTPUT_E001).toBe("E001");
     });
 
+    it("SAFE_OUTPUT_E009 is 'E009'", () => {
+      expect(SAFE_OUTPUT_E009).toBe("E009");
+    });
+
+    it("SAFE_OUTPUT_E010 is 'E010'", () => {
+      expect(SAFE_OUTPUT_E010).toBe("E010");
+    });
+
     it("SAFE_OUTPUT_E099 is 'E099'", () => {
       expect(SAFE_OUTPUT_E099).toBe("E099");
     });
+
+    it("CONFIG_HASH_MISMATCH is 'CONFIG_HASH_MISMATCH'", () => {
+      expect(CONFIG_HASH_MISMATCH).toBe("CONFIG_HASH_MISMATCH");
+    });
+
+    it("RATE_LIMIT_EXCEEDED is 'RATE_LIMIT_EXCEEDED'", () => {
+      expect(RATE_LIMIT_EXCEEDED).toBe("RATE_LIMIT_EXCEEDED");
+    });
   });
 
   describe("usage as error message prefixes", () => {
@@ -82,7 +116,7 @@ describe("error_codes", () => {
     });
 
     it("legacy codes are distinct from primary codes", () => {
-      const all = [ERR_VALIDATION, ERR_PERMISSION, ERR_API, ERR_CONFIG, ERR_NOT_FOUND, ERR_PARSE, ERR_SYSTEM, SAFE_OUTPUT_E001, SAFE_OUTPUT_E099];
+      const all = [ERR_VALIDATION, ERR_PERMISSION, ERR_API, ERR_CONFIG, ERR_NOT_FOUND, ERR_PARSE, ERR_SYSTEM, SAFE_OUTPUT_E001, SAFE_OUTPUT_E009, SAFE_OUTPUT_E010, SAFE_OUTPUT_E099, CONFIG_HASH_MISMATCH, RATE_LIMIT_EXCEEDED];
       const unique = new Set(all);
       expect(unique.size).toBe(all.length);
     });
diff --git a/actions/setup/js/error_recovery.cjs b/actions/setup/js/error_recovery.cjs
index 22f8d4cdb40..8814641a932 100644
--- a/actions/setup/js/error_recovery.cjs
+++ b/actions/setup/js/error_recovery.cjs
@@ -7,7 +7,7 @@
  */
 
 const { getErrorMessage } = require("./error_helpers.cjs");
-const { ERR_API } = require("./error_codes.cjs");
+const { ERR_API, SAFE_OUTPUT_E010, RATE_LIMIT_EXCEEDED } = require("./error_codes.cjs");
 const { logRetryEvent } = require("./github_rate_limit_logger.cjs");
 
 /**
@@ -53,6 +53,22 @@ const RATE_LIMIT_RETRY_CONFIG = {
   shouldRetry: isTransientError,
 };
 
+/**
+ * Message indicators used to detect GitHub API rate-limit errors.
+ * Matched case-insensitively against lower-cased error messages.
+ * Entries are kept lower-case because we lower-case input messages before substring matching.
+ * @type {string[]}
+ */
+const RATE_LIMIT_INDICATORS = ["rate limit", "secondary rate limit", "abuse detection", "too many requests"];
+
+/**
+ * @param {string} messageLower - Lower-cased error message
+ * @returns {boolean} True when message indicates GitHub rate limiting
+ */
+function hasRateLimitIndicator(messageLower) {
+  return RATE_LIMIT_INDICATORS.some(pattern => messageLower.includes(pattern));
+}
+
 /**
  * Determine if an error is transient and worth retrying
  * @param {any} error - The error to check
@@ -69,6 +85,13 @@ function isTransientError(error) {
     return true;
   }
 
+  // Status-based rate-limit detection handles cases where the message text is
+  // not descriptive enough (e.g. Octokit errors with status 429 and a generic
+  // "Request failed" message). Must be checked before the text patterns.
+  if (isRateLimitError(error)) {
+    return true;
+  }
+
   // Network-related errors that are likely transient
   const transientPatterns = [
     "network",
@@ -81,9 +104,7 @@ function isTransientError(error) {
     "502 bad gateway",
     "503 service unavailable",
     "504 gateway timeout",
-    "rate limit", // GitHub API rate limiting
-    "secondary rate limit", // GitHub secondary rate limits
-    "abuse detection", // GitHub abuse detection
+    ...RATE_LIMIT_INDICATORS, // GitHub rate limiting signals (including HTTP 429 text)
     "temporarily unavailable",
     "no server is currently available", // GitHub API server unavailability
   ];
@@ -155,6 +176,25 @@ function getRetryAfterMs(error) {
   return null;
 }
 
+/**
+ * Determine whether an error is specifically a GitHub API rate-limit error.
+ * @param {any} error - The error to classify
+ * @returns {boolean} True when the error indicates primary or secondary rate limiting
+ */
+function isRateLimitError(error) {
+  const status = error?.response?.status ?? error?.status ?? null;
+  const headers = error?.response?.headers ?? error?.headers ?? null;
+  const remainingHeader = headers?.["x-ratelimit-remaining"];
+  const retryAfterHeader = headers?.["retry-after"];
+  const hasRateLimitHeaders = status === 403 && (retryAfterHeader != null || (remainingHeader != null && parseInt(remainingHeader, 10) === 0));
+  if (status === 429 || hasRateLimitHeaders) {
+    return true;
+  }
+
+  const errorMsg = getErrorMessage(error).toLowerCase();
+  return hasRateLimitIndicator(errorMsg);
+}
+
 /**
  * Execute an operation with retry logic and exponential backoff
  * @template T
@@ -204,6 +244,18 @@ async function withRetry(operation, config = {}, operationName = "operation") {
       // If this was the last attempt, throw the enhanced error
       if (attempt === fullConfig.maxRetries) {
         core.warning(`${operationName} failed after ${fullConfig.maxRetries} retry attempts: ${errorMsg}`);
+        // E010 applies only when retry budget is at least 3 retries.
+        const hasEnoughRetriesForE010 = fullConfig.maxRetries >= 3;
+        if (hasEnoughRetriesForE010 && isRateLimitError(error)) {
+          throw enhanceError(error, {
+            operation: operationName,
+            attempt: attempt + 1,
+            maxRetries: fullConfig.maxRetries,
+            retryable: true,
+            code: `${SAFE_OUTPUT_E010} ${RATE_LIMIT_EXCEEDED}`,
+            suggestion: "RATE_LIMIT_EXCEEDED: GitHub API rate limit persisted after 3 retries.",
+          });
+        }
         throw enhanceError(error, {
           operation: operationName,
           attempt: attempt + 1,
diff --git a/actions/setup/js/error_recovery.test.cjs b/actions/setup/js/error_recovery.test.cjs
index 761bd5435d6..3ccf74f9b0c 100644
--- a/actions/setup/js/error_recovery.test.cjs
+++ b/actions/setup/js/error_recovery.test.cjs
@@ -35,6 +35,7 @@ describe("error_recovery", () => {
     it("should identify rate limit errors as transient", () => {
       expect(isTransientError(new Error("Rate limit exceeded"))).toBe(true);
       expect(isTransientError(new Error("Secondary rate limit hit"))).toBe(true);
+      expect(isTransientError(new Error("Too Many Requests"))).toBe(true);
       expect(isTransientError(new Error("Abuse detection triggered"))).toBe(true);
     });
 
@@ -50,6 +51,12 @@ describe("error_recovery", () => {
       expect(isTransientError(new Error("  <!DOCTYPE html><html>..."))).toBe(true);
     });
 
+    it("should identify status-only 429 errors as transient even with a non-descriptive message", () => {
+      // Octokit can produce errors where status=429 but the message contains no rate-limit text.
+      expect(isTransientError({ status: 429, message: "Request failed" })).toBe(true);
+      expect(isTransientError({ response: { status: 429 }, message: "Request failed" })).toBe(true);
+    });
+
     it("should not identify validation errors as transient", () => {
       expect(isTransientError(new Error("Invalid input"))).toBe(false);
       expect(isTransientError(new Error("Field is required"))).toBe(false);
@@ -103,6 +110,45 @@ describe("error_recovery", () => {
       expect(core.warning).toHaveBeenCalledWith(expect.stringContaining("failed after 2 retry attempts"));
     });
 
+    it("should emit E010 RATE_LIMIT_EXCEEDED when rate limit persists after 3 retries", async () => {
+      const rateLimitError = {
+        message: "Too Many Requests",
+        response: { status: 429, headers: { "retry-after": "1" } },
+      };
+      const operation = vi.fn().mockRejectedValue(rateLimitError);
+
+      await expect(withRetry(operation, { maxRetries: 3, initialDelayMs: 1 }, "test-operation")).rejects.toThrow("E010 RATE_LIMIT_EXCEEDED");
+
+      expect(operation).toHaveBeenCalledTimes(4); // Initial + 3 retries
+    });
+
+    it("should emit E010 for exhausted retries on 403 with retry-after header", async () => {
+      const rateLimitError = {
+        message: "secondary rate limit",
+        response: { status: 403, headers: { "retry-after": "1" } },
+      };
+      const operation = vi.fn().mockRejectedValue(rateLimitError);
+
+      await expect(withRetry(operation, { maxRetries: 3, initialDelayMs: 1 }, "test-operation")).rejects.toThrow("E010 RATE_LIMIT_EXCEEDED");
+    });
+
+    it("should emit E010 for exhausted retries on abuse-detection message without status", async () => {
+      const rateLimitError = new Error("Abuse detection mechanism triggered");
+      const operation = vi.fn().mockRejectedValue(rateLimitError);
+
+      await expect(withRetry(operation, { maxRetries: 3, initialDelayMs: 1 }, "test-operation")).rejects.toThrow("E010 RATE_LIMIT_EXCEEDED");
+    });
+
+    it("should emit E010 for status-only 429 with non-descriptive message persisting after 3 retries", async () => {
+      // Verifies that an Octokit-style error with status=429 and a generic message
+      // is retried (isTransientError returns true via isRateLimitError) and emits E010 on exhaustion.
+      const rateLimitError = { status: 429, message: "Request failed" };
+      const operation = vi.fn().mockRejectedValue(rateLimitError);
+
+      await expect(withRetry(operation, { maxRetries: 3, initialDelayMs: 1 }, "test-operation")).rejects.toThrow("E010 RATE_LIMIT_EXCEEDED");
+      expect(operation).toHaveBeenCalledTimes(4); // Initial + 3 retries
+    });
+
     it("should use exponential backoff", async () => {
       const operation = vi.fn().mockRejectedValueOnce(new Error("Network timeout")).mockRejectedValueOnce(new Error("Network timeout")).mockResolvedValue("success");