diff --git a/actions/setup/js/set_issue_field.cjs b/actions/setup/js/set_issue_field.cjs
index 292c5534117..37d59d85c6d 100644
--- a/actions/setup/js/set_issue_field.cjs
+++ b/actions/setup/js/set_issue_field.cjs
@@ -47,7 +47,6 @@ async function fetchIssueFields(githubClient, owner, repo) {
         issueFields(first: 100) {
           nodes {
             __typename
-            ... on IssueField { id name }
             ... on IssueFieldText { id name }
             ... on IssueFieldNumber { id name }
             ... on IssueFieldDate { id name }
@@ -61,7 +60,6 @@ async function fetchIssueFields(githubClient, owner, repo) {
             issueFields(first: 100) {
               nodes {
                 __typename
-                ... on IssueField { id name }
                 ... on IssueFieldText { id name }
                 ... on IssueFieldNumber { id name }
                 ... on IssueFieldDate { id name }
diff --git a/actions/setup/js/set_issue_field.test.cjs b/actions/setup/js/set_issue_field.test.cjs
index f841ec88abe..9d9bfc316fb 100644
--- a/actions/setup/js/set_issue_field.test.cjs
+++ b/actions/setup/js/set_issue_field.test.cjs
@@ -274,7 +274,7 @@ describe("set_issue_field (Handler Factory Architecture)", () => {
     expect(mockCore.error).not.toHaveBeenCalled();
   });
 
-  it("fetchIssueFields query uses concrete type fragments (no direct id/name on IssueFields union)", async () => {
+  it("fetchIssueFields query uses only concrete issue field type fragments", async () => {
     let capturedQuery = "";
     mockGraphql.mockImplementation(query => {
       if (query.includes("repository(owner")) {
@@ -295,8 +295,8 @@ describe("set_issue_field (Handler Factory Architecture)", () => {
     // Bare "id" or "name" would appear on their own line; inside a fragment they appear as "{ id name }"
     expect(capturedQuery).not.toMatch(/^\s+id\s*$/m);
     expect(capturedQuery).not.toMatch(/^\s+name\s*$/m);
-    // The query must include a base IssueField fragment to cover unknown/future field types
-    expect(capturedQuery).toContain("... on IssueField");
+    // The query must not include the non-existent IssueField type fragment
+    expect(capturedQuery).not.toMatch(/\.\.\.\s+on\s+IssueField\s*\{/);
     // The query must include at least the concrete IssueFieldText fragment
     expect(capturedQuery).toContain("... on IssueFieldText");
     // The query must include the IssueFieldSingleSelect fragment with options
@@ -324,7 +324,7 @@ describe("set_issue_field (Handler Factory Architecture)", () => {
     expect(capturedQuery).not.toContain("... on User");
   });
 
-  it("fetchIssueFields filters out nodes missing id or name (null entries and unknown types without base fragment)", async () => {
+  it("fetchIssueFields filters out nodes missing id or name (null entries and unknown types)", async () => {
     mockGraphql.mockImplementation(query => {
       if (query.includes("issueFields")) {
         return Promise.resolve({
diff --git a/actions/setup/js/set_issue_field_api_query.integration.test.cjs b/actions/setup/js/set_issue_field_api_query.integration.test.cjs
new file mode 100644
index 00000000000..da39dd94284
--- /dev/null
+++ b/actions/setup/js/set_issue_field_api_query.integration.test.cjs
@@ -0,0 +1,60 @@
+// @ts-check
+import { describe, expect, it } from "vitest";
+
+const ISSUE_FIELDS_DISCOVERY_QUERY = `query($owner: String!, $repo: String!) {
+  repository(owner: $owner, name: $repo) {
+    issueFields(first: 100) {
+      nodes {
+        __typename
+        ... on IssueFieldText { id name }
+        ... on IssueFieldNumber { id name }
+        ... on IssueFieldDate { id name }
+        ... on IssueFieldSingleSelect { id name options { id name } }
+        ... on IssueFieldMultiSelect { id name options { id name } }
+      }
+    }
+    owner {
+      __typename
+      ... on Organization {
+        issueFields(first: 100) {
+          nodes {
+            __typename
+            ... on IssueFieldText { id name }
+            ... on IssueFieldNumber { id name }
+            ... on IssueFieldDate { id name }
+            ... on IssueFieldSingleSelect { id name options { id name } }
+            ... on IssueFieldMultiSelect { id name options { id name } }
+          }
+        }
+      }
+    }
+  }
+}`;
+
+describe("set_issue_field GraphQL discovery query integration", () => {
+  it("validates against live schema and excludes the removed IssueField fragment", async () => {
+    const token = process.env.GITHUB_TOKEN || process.env.GH_TOKEN;
+    if (!token) {
+      console.log("Skipping live GraphQL schema test - no GITHUB_TOKEN or GH_TOKEN available");
+      return;
+    }
+
+    const owner = process.env.GITHUB_REPOSITORY_OWNER || "github";
+    const repo = process.env.GITHUB_REPOSITORY?.split("/")[1] || "gh-aw";
+
+    const { getOctokit } = await import("@actions/github");
+    const octokit = getOctokit(token);
+
+    try {
+      const result = await octokit.graphql(ISSUE_FIELDS_DISCOVERY_QUERY, { owner, repo });
+      expect(result?.repository).toBeDefined();
+    } catch (error) {
+      const message = error instanceof Error ? error.message : String(error);
+      if (message.includes("Blocked by DNS monitoring proxy")) {
+        console.log("Skipping live GraphQL schema test - api.github.com blocked by DNS monitoring proxy");
+        return;
+      }
+      throw error;
+    }
+  });
+});
diff --git a/actions/setup/js/vitest.integration.config.mjs b/actions/setup/js/vitest.integration.config.mjs
index 9d46fbe4197..c18b5d11338 100644
--- a/actions/setup/js/vitest.integration.config.mjs
+++ b/actions/setup/js/vitest.integration.config.mjs
@@ -4,7 +4,7 @@ export default defineConfig({
   test: {
     environment: "node",
     globals: true,
-    include: ["frontmatter_hash_github_api.test.cjs"],
+    include: ["frontmatter_hash_github_api.test.cjs", "set_issue_field_api_query.integration.test.cjs"],
     testTimeout: 30000,
     hookTimeout: 10000,
   },