diff --git a/actions/setup/js/messages_staged.cjs b/actions/setup/js/messages_staged.cjs
index de684e1041f..73ef4ba9c99 100644
--- a/actions/setup/js/messages_staged.cjs
+++ b/actions/setup/js/messages_staged.cjs
@@ -22,15 +22,9 @@ const { getMessages, renderTemplate, toSnakeCase } = require("./messages_core.cj
  */
 function getStagedTitle(ctx) {
   const messages = getMessages();
-
-  // Create context with both camelCase and snake_case keys
   const templateContext = toSnakeCase(ctx);
-
-  // Default staged title template
-  const defaultTitle = "## 🔍 Preview: {operation}";
-
-  // Use custom title if configured
-  return messages?.stagedTitle ? renderTemplate(messages.stagedTitle, templateContext) : renderTemplate(defaultTitle, templateContext);
+  const configuredTemplate = typeof messages?.stagedTitle === "string" ? messages.stagedTitle : "";
+  return renderTemplate(configuredTemplate || "## 🔍 Preview: {operation}", templateContext);
 }
 
 /**
@@ -40,15 +34,9 @@ function getStagedTitle(ctx) {
  */
 function getStagedDescription(ctx) {
   const messages = getMessages();
-
-  // Create context with both camelCase and snake_case keys
   const templateContext = toSnakeCase(ctx);
-
-  // Default staged description template
-  const defaultDescription = "📋 The following operations would be performed if staged mode was disabled:";
-
-  // Use custom description if configured
-  return messages?.stagedDescription ? renderTemplate(messages.stagedDescription, templateContext) : renderTemplate(defaultDescription, templateContext);
+  const configuredTemplate = typeof messages?.stagedDescription === "string" ? messages.stagedDescription : "";
+  return renderTemplate(configuredTemplate || "📋 The following operations would be performed if staged mode was disabled:", templateContext);
 }
 
 module.exports = {
diff --git a/actions/setup/js/messages_staged.test.cjs b/actions/setup/js/messages_staged.test.cjs
new file mode 100644
index 00000000000..ed0d4da1e2b
--- /dev/null
+++ b/actions/setup/js/messages_staged.test.cjs
@@ -0,0 +1,145 @@
+// @ts-check
+import { describe, it, expect, beforeEach, vi } from "vitest";
+
+// messages_core.cjs calls core.warning on parse failures - provide a stub
+const mockCore = {
+  info: vi.fn(),
+  warning: vi.fn(),
+  error: vi.fn(),
+  setFailed: vi.fn(),
+  setOutput: vi.fn(),
+};
+global.core = mockCore;
+
+const { getStagedTitle, getStagedDescription } = require("./messages_staged.cjs");
+
+const OPERATION = "Create Issues";
+
+describe("messages_staged", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    delete process.env.GH_AW_SAFE_OUTPUT_MESSAGES;
+  });
+
+  describe("getStagedTitle", () => {
+    it("returns the default title with operation substituted", () => {
+      const title = getStagedTitle({ operation: OPERATION });
+      expect(title).toBe(`## 🔍 Preview: ${OPERATION}`);
+    });
+
+    it("substitutes a different operation value", () => {
+      const title = getStagedTitle({ operation: "Add Comments" });
+      expect(title).toBe("## 🔍 Preview: Add Comments");
+    });
+
+    it("uses custom template from config", () => {
+      process.env.GH_AW_SAFE_OUTPUT_MESSAGES = JSON.stringify({ stagedTitle: "Staging: {operation}" });
+      const title = getStagedTitle({ operation: OPERATION });
+      expect(title).toBe(`Staging: ${OPERATION}`);
+    });
+
+    it("falls back to default when stagedTitle is absent from config", () => {
+      process.env.GH_AW_SAFE_OUTPUT_MESSAGES = JSON.stringify({ runSuccess: "other" });
+      const title = getStagedTitle({ operation: OPERATION });
+      expect(title).toBe(`## 🔍 Preview: ${OPERATION}`);
+    });
+
+    it("falls back to default when stagedTitle is an empty string", () => {
+      process.env.GH_AW_SAFE_OUTPUT_MESSAGES = JSON.stringify({ stagedTitle: "" });
+      const title = getStagedTitle({ operation: OPERATION });
+      expect(title).toBe(`## 🔍 Preview: ${OPERATION}`);
+    });
+
+    it("falls back to default when stagedTitle is a falsy non-string value", () => {
+      process.env.GH_AW_SAFE_OUTPUT_MESSAGES = JSON.stringify({ stagedTitle: 0 });
+      const title = getStagedTitle({ operation: OPERATION });
+      expect(title).toBe(`## 🔍 Preview: ${OPERATION}`);
+    });
+
+    it("falls back to default when config is invalid JSON", () => {
+      process.env.GH_AW_SAFE_OUTPUT_MESSAGES = "not-json";
+      const title = getStagedTitle({ operation: OPERATION });
+      expect(title).toBe(`## 🔍 Preview: ${OPERATION}`);
+    });
+
+    it("supports snake_case placeholders from camelCase context keys", () => {
+      process.env.GH_AW_SAFE_OUTPUT_MESSAGES = JSON.stringify({ stagedTitle: "{operation_name}: {operation}" });
+      const title = getStagedTitle({ operation: OPERATION, operationName: "Create Comment" });
+      expect(title).toBe(`Create Comment: ${OPERATION}`);
+    });
+
+    it("returns an empty-operation title when operation is an empty string", () => {
+      const title = getStagedTitle({ operation: "" });
+      expect(title).toBe("## 🔍 Preview: ");
+    });
+
+    it("leaves unrecognised placeholders unchanged in custom template", () => {
+      process.env.GH_AW_SAFE_OUTPUT_MESSAGES = JSON.stringify({ stagedTitle: "{operation} | {unknown}" });
+      const title = getStagedTitle({ operation: OPERATION });
+      expect(title).toBe(`${OPERATION} | {unknown}`);
+    });
+  });
+
+  describe("getStagedDescription", () => {
+    it("returns the default description", () => {
+      const desc = getStagedDescription({ operation: OPERATION });
+      expect(desc).toBe("📋 The following operations would be performed if staged mode was disabled:");
+    });
+
+    it("uses custom description template from config", () => {
+      process.env.GH_AW_SAFE_OUTPUT_MESSAGES = JSON.stringify({ stagedDescription: "Preview of: {operation}" });
+      const desc = getStagedDescription({ operation: OPERATION });
+      expect(desc).toBe(`Preview of: ${OPERATION}`);
+    });
+
+    it("falls back to default when stagedDescription is absent from config", () => {
+      process.env.GH_AW_SAFE_OUTPUT_MESSAGES = JSON.stringify({ stagedTitle: "title only" });
+      const desc = getStagedDescription({ operation: OPERATION });
+      expect(desc).toBe("📋 The following operations would be performed if staged mode was disabled:");
+    });
+
+    it("falls back to default when stagedDescription is an empty string", () => {
+      process.env.GH_AW_SAFE_OUTPUT_MESSAGES = JSON.stringify({ stagedDescription: "" });
+      const desc = getStagedDescription({ operation: OPERATION });
+      expect(desc).toBe("📋 The following operations would be performed if staged mode was disabled:");
+    });
+
+    it("falls back to default when stagedDescription is a falsy non-string value", () => {
+      process.env.GH_AW_SAFE_OUTPUT_MESSAGES = JSON.stringify({ stagedDescription: false });
+      const desc = getStagedDescription({ operation: OPERATION });
+      expect(desc).toBe("📋 The following operations would be performed if staged mode was disabled:");
+    });
+
+    it("falls back to default when config is invalid JSON", () => {
+      process.env.GH_AW_SAFE_OUTPUT_MESSAGES = "{bad json";
+      const desc = getStagedDescription({ operation: OPERATION });
+      expect(desc).toBe("📋 The following operations would be performed if staged mode was disabled:");
+    });
+
+    it("supports custom description with operation placeholder", () => {
+      process.env.GH_AW_SAFE_OUTPUT_MESSAGES = JSON.stringify({ stagedDescription: "Would run: {operation}" });
+      const desc = getStagedDescription({ operation: "Close PRs" });
+      expect(desc).toBe("Would run: Close PRs");
+    });
+
+    it("default description does not contain unfilled placeholders", () => {
+      const desc = getStagedDescription({ operation: OPERATION });
+      expect(desc).not.toMatch(/\{[^}]+\}/);
+    });
+  });
+
+  describe("independent config keys", () => {
+    it("getStagedTitle and getStagedDescription use their own config keys independently", () => {
+      process.env.GH_AW_SAFE_OUTPUT_MESSAGES = JSON.stringify({
+        stagedTitle: "Custom title: {operation}",
+        stagedDescription: "Custom desc: {operation}",
+      });
+
+      const title = getStagedTitle({ operation: OPERATION });
+      const desc = getStagedDescription({ operation: OPERATION });
+
+      expect(title).toBe(`Custom title: ${OPERATION}`);
+      expect(desc).toBe(`Custom desc: ${OPERATION}`);
+    });
+  });
+});