fix: handle non-user actors (e.g. Copilot) in permission and actor checks (#1144)

GitHub Apps like Copilot SWE Agent set GITHUB_ACTOR to a value (e.g.
"Copilot") that is neither a valid GitHub user nor ends with "[bot]".
This caused two independent crashes:

1. checkWritePermissions (permissions.ts): called the collaborator
   permission API which returns 404 "is not a user" for non-user actors.
2. checkHumanActor (actor.ts): called the Users API first, which 404s,
   before ever reaching the allowed_bots check.

Fix both by:
- Checking allowed_bots BEFORE making API calls, so known bots skip the
  API entirely.
- In permissions.ts, catching "is not a user" 404 errors and falling
  back to the allowed_bots list instead of crashing.
- In actor.ts, catching 404 errors and providing a clear error message
  telling the user to add the bot to allowed_bots.

Closes #900, #903, #1018, #1133

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

test/actor.test.ts

@@ -93,4 +93,78 @@ describe("checkHumanActor", () => {
       "Workflow initiated by non-human actor: other-bot (type: Bot). Add bot to allowed_bots list or use '*' to allow all bots.",
     );
   });
+
+  describe("non-[bot] actors (e.g. GitHub Copilot)", () => {
+    // GitHub Copilot SWE Agent sets GITHUB_ACTOR="Copilot" which is not a
+    // valid GitHub user and doesn't end with [bot], causing 404 on the
+    // Users API. These tests verify the fix handles this gracefully.
+
+    function createMockOctokitThat404s(): Octokit {
+      return {
+        users: {
+          getByUsername: async () => {
+            const err = new Error("Not Found");
+            (err as any).status = 404;
+            throw err;
+          },
+        },
+      } as unknown as Octokit;
+    }
+
+    test("should pass for non-[bot] actor when in allowed_bots list", async () => {
+      const mockOctokit = createMockOctokitThat404s();
+      const context = createMockContext();
+      context.actor = "Copilot";
+      context.inputs.allowedBots = "copilot,cursor";
+
+      // Should not even call the API — allowed_bots check happens first
+      await expect(
+        checkHumanActor(mockOctokit, context),
+      ).resolves.toBeUndefined();
+    });
+
+    test("should pass for non-[bot] actor when all bots are allowed", async () => {
+      const mockOctokit = createMockOctokitThat404s();
+      const context = createMockContext();
+      context.actor = "Copilot";
+      context.inputs.allowedBots = "*";
+
+      await expect(
+        checkHumanActor(mockOctokit, context),
+      ).resolves.toBeUndefined();
+    });
+
+    test("should throw with clear message for non-[bot] actor that 404s and is not in allowed list", async () => {
+      const mockOctokit = createMockOctokitThat404s();
+      const context = createMockContext();
+      context.actor = "Copilot";
+      context.inputs.allowedBots = "cursor";
+
+      await expect(checkHumanActor(mockOctokit, context)).rejects.toThrow(
+        "Workflow initiated by non-human actor: copilot (actor not found on GitHub). Add bot to allowed_bots list or use '*' to allow all bots.",
+      );
+    });
+
+    test("should throw with clear message for non-[bot] actor that 404s and allowed_bots is empty", async () => {
+      const mockOctokit = createMockOctokitThat404s();
+      const context = createMockContext();
+      context.actor = "Copilot";
+      context.inputs.allowedBots = "";
+
+      await expect(checkHumanActor(mockOctokit, context)).rejects.toThrow(
+        "Workflow initiated by non-human actor: copilot (actor not found on GitHub). Add bot to allowed_bots list or use '*' to allow all bots.",
+      );
+    });
+
+    test("should match allowed_bots case-insensitively for non-[bot] actors", async () => {
+      const mockOctokit = createMockOctokitThat404s();
+      const context = createMockContext();
+      context.actor = "Copilot";
+      context.inputs.allowedBots = "COPILOT";
+
+      await expect(
+        checkHumanActor(mockOctokit, context),
+      ).resolves.toBeUndefined();
+    });
+  });
 });

test/permissions.test.ts

@@ -303,4 +303,104 @@ describe("checkWritePermissions", () => {
       );
     });
   });
+
+  describe("non-[bot] actors (e.g. GitHub Copilot)", () => {
+    // GitHub Copilot SWE Agent sets GITHUB_ACTOR="Copilot" which doesn't
+    // end with [bot] and is not a valid GitHub user, so the collaborator
+    // permission API returns 404 with "is not a user".
+
+    const createMockOctokitThat404s = () => ({
+      repos: {
+        getCollaboratorPermissionLevel: async () => {
+          const err = new Error(
+            "HttpError: Copilot is not a user - https://docs.github.com/rest/collaborators/collaborators#get-repository-permissions-for-a-user",
+          );
+          (err as any).status = 404;
+          throw err;
+        },
+      },
+    } as any);
+
+    test("should return true for non-[bot] actor in allowed_bots (pre-API check)", async () => {
+      // The allowed_bots check should happen BEFORE calling the API,
+      // so this should succeed even with a 404-ing mock.
+      const mockOctokit = createMockOctokitThat404s();
+      const context = createContext();
+      context.actor = "Copilot";
+      context.inputs.allowedBots = "copilot,cursor";
+
+      const result = await checkWritePermissions(mockOctokit, context);
+
+      expect(result).toBe(true);
+      expect(coreInfoSpy).toHaveBeenCalledWith(
+        "Actor Copilot is in allowed_bots list, skipping permission check",
+      );
+    });
+
+    test("should return true for non-[bot] actor when allowed_bots is '*' (pre-API check)", async () => {
+      const mockOctokit = createMockOctokitThat404s();
+      const context = createContext();
+      context.actor = "Copilot";
+      context.inputs.allowedBots = "*";
+
+      const result = await checkWritePermissions(mockOctokit, context);
+
+      expect(result).toBe(true);
+    });
+
+    test("should return true for non-[bot] actor in allowed_bots via 404 fallback", async () => {
+      // Even if somehow we reach the API call (e.g. race condition or
+      // future refactor), the 404 catch path should also check allowed_bots.
+      const mockOctokit = createMockOctokitThat404s();
+      const context = createContext();
+      context.actor = "SomeNewBot";
+      context.inputs.allowedBots = "somenewbot";
+
+      const result = await checkWritePermissions(mockOctokit, context);
+
+      expect(result).toBe(true);
+    });
+
+    test("should return false for non-[bot] actor that 404s and is not in allowed_bots", async () => {
+      const mockOctokit = createMockOctokitThat404s();
+      const context = createContext();
+      context.actor = "Copilot";
+      context.inputs.allowedBots = "cursor";
+
+      const result = await checkWritePermissions(mockOctokit, context);
+
+      expect(result).toBe(false);
+      expect(coreWarningSpy).toHaveBeenCalledWith(
+        "Non-user actor Copilot is not in allowed_bots list. Add it to allowed_bots or use '*' to allow all bots.",
+      );
+    });
+
+    test("should return false for non-[bot] actor that 404s with empty allowed_bots", async () => {
+      const mockOctokit = createMockOctokitThat404s();
+      const context = createContext();
+      context.actor = "Copilot";
+      context.inputs.allowedBots = "";
+
+      const result = await checkWritePermissions(mockOctokit, context);
+
+      expect(result).toBe(false);
+    });
+
+    test("should still throw for non-404 API errors", async () => {
+      const mockOctokit = {
+        repos: {
+          getCollaboratorPermissionLevel: async () => {
+            throw new Error("Internal Server Error");
+          },
+        },
+      } as any;
+      const context = createContext();
+      context.actor = "Copilot";
+      context.inputs.allowedBots = "";
+
+      await expect(checkWritePermissions(mockOctokit, context)).rejects.toThrow(
+        "Failed to check permissions for Copilot",
+      );
+    });
+  });
 });