diff --git a/src/github/validation/permissions.ts b/src/github/validation/permissions.ts
index 731fcd41c..6a71bfc7b 100644
--- a/src/github/validation/permissions.ts
+++ b/src/github/validation/permissions.ts
@@ -66,7 +66,18 @@ export async function checkWritePermissions(
       core.warning(`Actor has insufficient permissions: ${permissionLevel}`);
       return false;
     }
-  } catch (error) {
+  } catch (error: any) {
+    // Handle 404 errors for non-user actors (e.g., "Copilot")
+    // The collaborator permission API returns 404 when the actor is not a
+    // regular GitHub user. These are GitHub system actors that inherently
+    // operate with the permissions granted by the workflow configuration.
+    if (error?.status === 404) {
+      core.info(
+        `Actor "${actor}" is not a GitHub user (received 404). Treating as a non-user actor and allowing.`,
+      );
+      return true;
+    }
+
     core.error(`Failed to check permissions: ${error}`);
     throw new Error(`Failed to check permissions for ${actor}: ${error}`);
   }
diff --git a/test/permissions.test.ts b/test/permissions.test.ts
index cf2efdb0e..0050a1bce 100644
--- a/test/permissions.test.ts
+++ b/test/permissions.test.ts
@@ -140,7 +140,53 @@ describe("checkWritePermissions", () => {
     expect(result).toBe(true);
   });
 
-  test("should throw error when permission check fails", async () => {
+  test("should return true when API returns 404 for non-user actor", async () => {
+    const httpError = Object.assign(
+      new Error("Copilot is not a user"),
+      { status: 404 },
+    );
+    const mockOctokit = {
+      repos: {
+        getCollaboratorPermissionLevel: async () => {
+          throw httpError;
+        },
+      },
+    } as any;
+    const context = createContext();
+    context.actor = "Copilot";
+
+    const result = await checkWritePermissions(mockOctokit, context);
+
+    expect(result).toBe(true);
+    expect(coreInfoSpy).toHaveBeenCalledWith(
+      'Actor "Copilot" is not a GitHub user (received 404). Treating as a non-user actor and allowing.',
+    );
+  });
+
+  test("should return true when API returns 404 for any non-user actor name", async () => {
+    const httpError = Object.assign(
+      new Error("some-service is not a user"),
+      { status: 404 },
+    );
+    const mockOctokit = {
+      repos: {
+        getCollaboratorPermissionLevel: async () => {
+          throw httpError;
+        },
+      },
+    } as any;
+    const context = createContext();
+    context.actor = "some-service";
+
+    const result = await checkWritePermissions(mockOctokit, context);
+
+    expect(result).toBe(true);
+    expect(coreInfoSpy).toHaveBeenCalledWith(
+      'Actor "some-service" is not a GitHub user (received 404). Treating as a non-user actor and allowing.',
+    );
+  });
+
+  test("should throw error when permission check fails with non-404 error", async () => {
     const error = new Error("API error");
     const mockOctokit = {
       repos: {
@@ -160,6 +206,27 @@ describe("checkWritePermissions", () => {
     );
   });
 
+  test("should throw error for 500 server errors", async () => {
+    const httpError = Object.assign(
+      new Error("Internal Server Error"),
+      { status: 500 },
+    );
+    const mockOctokit = {
+      repos: {
+        getCollaboratorPermissionLevel: async () => {
+          throw httpError;
+        },
+      },
+    } as any;
+    const context = createContext();
+
+    await expect(checkWritePermissions(mockOctokit, context)).rejects.toThrow(
+      "Failed to check permissions for test-user",
+    );
+
+    expect(coreErrorSpy).toHaveBeenCalled();
+  });
+
   test("should call API with correct parameters", async () => {
     let capturedParams: any;
     const mockOctokit = {