diff --git a/actions/setup/js/remove_trigger_label.cjs b/actions/setup/js/remove_trigger_label.cjs
index 102342778a8..b9dd6df6de5 100644
--- a/actions/setup/js/remove_trigger_label.cjs
+++ b/actions/setup/js/remove_trigger_label.cjs
@@ -2,6 +2,7 @@
 /// <reference types="@actions/github-script" />
 
 const { ERR_API, ERR_CONFIG } = require("./error_codes.cjs");
+const { getErrorMessage } = require("./error_helpers.cjs");
 
 /**
  * Remove the label that triggered this workflow from the issue, pull request, or discussion.
@@ -13,8 +14,6 @@ const { ERR_API, ERR_CONFIG } = require("./error_codes.cjs");
 async function main() {
   const labelNamesJSON = process.env.GH_AW_LABEL_NAMES;
 
-  const { getErrorMessage } = require("./error_helpers.cjs");
-
   if (!labelNamesJSON) {
     core.setFailed(`${ERR_CONFIG}: Configuration error: GH_AW_LABEL_NAMES not specified.`);
     return;
diff --git a/actions/setup/js/remove_trigger_label.test.cjs b/actions/setup/js/remove_trigger_label.test.cjs
new file mode 100644
index 00000000000..59d8ed413f5
--- /dev/null
+++ b/actions/setup/js/remove_trigger_label.test.cjs
@@ -0,0 +1,220 @@
+// @ts-check
+import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
+const { ERR_CONFIG, ERR_API } = require("./error_codes.cjs");
+
+const mockCore = {
+  info: vi.fn(),
+  warning: vi.fn(),
+  error: vi.fn(),
+  setFailed: vi.fn(),
+  setOutput: vi.fn(),
+};
+
+const mockGithub = {
+  rest: {
+    issues: {
+      removeLabel: vi.fn(),
+    },
+  },
+  graphql: vi.fn(),
+};
+
+/** @type {any} */
+let mockContext = {
+  eventName: "issues",
+  repo: { owner: "testowner", repo: "testrepo" },
+  payload: {
+    label: { name: "ai-label", node_id: "LA_label1" },
+    issue: { number: 42 },
+  },
+};
+
+global.core = mockCore;
+global.github = mockGithub;
+global.context = mockContext;
+
+/** @returns {Promise<void>} */
+async function runScript() {
+  const { main } = await import("./remove_trigger_label.cjs?" + Date.now());
+  await main();
+}
+
+describe("remove_trigger_label", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    vi.resetModules();
+
+    process.env.GH_AW_LABEL_NAMES = JSON.stringify(["ai-label", "bot-run"]);
+
+    mockContext = {
+      eventName: "issues",
+      repo: { owner: "testowner", repo: "testrepo" },
+      payload: {
+        label: { name: "ai-label", node_id: "LA_label1" },
+        issue: { number: 42 },
+      },
+    };
+    global.context = mockContext;
+
+    mockGithub.rest.issues.removeLabel.mockResolvedValue({});
+    mockGithub.graphql.mockResolvedValue({});
+  });
+
+  afterEach(() => {
+    delete process.env.GH_AW_LABEL_NAMES;
+  });
+
+  describe("missing configuration", () => {
+    it("should fail when GH_AW_LABEL_NAMES is not set", async () => {
+      delete process.env.GH_AW_LABEL_NAMES;
+      await runScript();
+      expect(mockCore.setFailed).toHaveBeenCalledWith(expect.stringContaining(ERR_CONFIG));
+    });
+
+    it("should fail when GH_AW_LABEL_NAMES is invalid JSON", async () => {
+      process.env.GH_AW_LABEL_NAMES = "not-valid-json";
+      await runScript();
+      expect(mockCore.setFailed).toHaveBeenCalledWith(expect.stringContaining(ERR_CONFIG));
+    });
+
+    it("should fail when GH_AW_LABEL_NAMES is not an array", async () => {
+      process.env.GH_AW_LABEL_NAMES = JSON.stringify({ label: "ai-label" });
+      await runScript();
+      expect(mockCore.setFailed).toHaveBeenCalledWith(expect.stringContaining(ERR_CONFIG));
+    });
+  });
+
+  describe("workflow_dispatch event", () => {
+    it("should skip label removal for workflow_dispatch", async () => {
+      global.context = { ...mockContext, eventName: "workflow_dispatch", payload: {} };
+      await runScript();
+      expect(mockGithub.rest.issues.removeLabel).not.toHaveBeenCalled();
+      expect(mockCore.setOutput).toHaveBeenCalledWith("label_name", "");
+    });
+  });
+
+  describe("no trigger label in payload", () => {
+    it("should skip removal when payload has no label", async () => {
+      global.context = { ...mockContext, payload: { issue: { number: 42 } } };
+      await runScript();
+      expect(mockGithub.rest.issues.removeLabel).not.toHaveBeenCalled();
+      expect(mockCore.setOutput).toHaveBeenCalledWith("label_name", "");
+    });
+  });
+
+  describe("label not in configured list", () => {
+    it("should skip removal when label is not configured", async () => {
+      global.context = {
+        ...mockContext,
+        payload: { label: { name: "random-label" }, issue: { number: 42 } },
+      };
+      await runScript();
+      expect(mockGithub.rest.issues.removeLabel).not.toHaveBeenCalled();
+      expect(mockCore.setOutput).toHaveBeenCalledWith("label_name", "random-label");
+    });
+  });
+
+  describe("issues event", () => {
+    it("should remove label from issue", async () => {
+      await runScript();
+      expect(mockGithub.rest.issues.removeLabel).toHaveBeenCalledWith({
+        owner: "testowner",
+        repo: "testrepo",
+        issue_number: 42,
+        name: "ai-label",
+      });
+      expect(mockCore.setOutput).toHaveBeenCalledWith("label_name", "ai-label");
+    });
+
+    it("should skip when issue number is missing", async () => {
+      global.context = {
+        ...mockContext,
+        payload: { label: { name: "ai-label" } },
+      };
+      await runScript();
+      expect(mockGithub.rest.issues.removeLabel).not.toHaveBeenCalled();
+      expect(mockCore.setOutput).toHaveBeenCalledWith("label_name", "ai-label");
+    });
+  });
+
+  describe("pull_request event", () => {
+    it("should remove label from pull request", async () => {
+      global.context = {
+        ...mockContext,
+        eventName: "pull_request",
+        payload: {
+          label: { name: "ai-label" },
+          pull_request: { number: 99 },
+        },
+      };
+      await runScript();
+      expect(mockGithub.rest.issues.removeLabel).toHaveBeenCalledWith({
+        owner: "testowner",
+        repo: "testrepo",
+        issue_number: 99,
+        name: "ai-label",
+      });
+      expect(mockCore.setOutput).toHaveBeenCalledWith("label_name", "ai-label");
+    });
+
+    it("should skip when PR number is missing", async () => {
+      global.context = {
+        ...mockContext,
+        eventName: "pull_request",
+        payload: { label: { name: "ai-label" } },
+      };
+      await runScript();
+      expect(mockGithub.rest.issues.removeLabel).not.toHaveBeenCalled();
+    });
+  });
+
+  describe("discussion event", () => {
+    it("should remove label from discussion via graphql", async () => {
+      global.context = {
+        ...mockContext,
+        eventName: "discussion",
+        payload: {
+          label: { name: "ai-label", node_id: "LA_label1" },
+          discussion: { node_id: "D_disc1" },
+        },
+      };
+      await runScript();
+      expect(mockGithub.graphql).toHaveBeenCalledWith(
+        expect.stringContaining("removeLabelsFromLabelable"),
+        expect.objectContaining({
+          labelableId: "D_disc1",
+          labelIds: ["LA_label1"],
+        })
+      );
+      expect(mockCore.setOutput).toHaveBeenCalledWith("label_name", "ai-label");
+    });
+
+    it("should skip when discussion node_id is missing", async () => {
+      global.context = {
+        ...mockContext,
+        eventName: "discussion",
+        payload: { label: { name: "ai-label" } },
+      };
+      await runScript();
+      expect(mockGithub.graphql).not.toHaveBeenCalled();
+    });
+  });
+
+  describe("error handling", () => {
+    it("should treat 404 error as already-removed (non-fatal)", async () => {
+      const err = Object.assign(new Error("Not Found"), { status: 404 });
+      mockGithub.rest.issues.removeLabel.mockRejectedValue(err);
+      await runScript();
+      expect(mockCore.setFailed).not.toHaveBeenCalled();
+      expect(mockCore.setOutput).toHaveBeenCalledWith("label_name", "ai-label");
+    });
+
+    it("should warn on non-404 API errors", async () => {
+      const err = Object.assign(new Error("Server error"), { status: 500 });
+      mockGithub.rest.issues.removeLabel.mockRejectedValue(err);
+      await runScript();
+      expect(mockCore.warning).toHaveBeenCalledWith(expect.stringContaining(ERR_API));
+      expect(mockCore.setFailed).not.toHaveBeenCalled();
+    });
+  });
+});