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>

src/github/validation/actor.ts

@@ -8,53 +8,75 @@
 import type { Octokit } from "@octokit/rest";
 import type { GitHubContext } from "../context";
 
+function isAllowedBot(actor: string, allowedBots: string): boolean {
+  const trimmed = allowedBots.trim();
+  if (trimmed === "*") return true;
+  if (!trimmed) return false;
+
+  const allowedList = trimmed
+    .split(",")
+    .map((bot) =>
+      bot
+        .trim()
+        .toLowerCase()
+        .replace(/\[bot\]$/, ""),
+    )
+    .filter((bot) => bot.length > 0);
+
+  const normalizedActor = actor.toLowerCase().replace(/\[bot\]$/, "");
+  return allowedList.includes(normalizedActor);
+}
+
 export async function checkHumanActor(
   octokit: Octokit,
   githubContext: GitHubContext,
 ) {
-  // Fetch user information from GitHub API
+  const allowedBots = githubContext.inputs.allowedBots;
-  const { data: userData } = await octokit.users.getByUsername({
-    username: githubContext.actor,
-  });
 
-  const actorType = userData.type;
+  // Check allowed_bots BEFORE calling the GitHub Users API.
+  // Some bot actors (e.g. GitHub Copilot with GITHUB_ACTOR="Copilot") are
+  // not resolvable via the Users API and would cause a 404 if we called it
+  // first.  By checking the allow-list early we avoid the unnecessary API
+  // call and the resulting crash.
+  if (isAllowedBot(githubContext.actor, allowedBots)) {
+    console.log(
+      `Actor ${githubContext.actor} is in allowed_bots list, skipping human actor check`,
+    );
+    return;
+  }
+
+  // Fetch user information from GitHub API
+  let actorType: string;
+  try {
+    const { data: userData } = await octokit.users.getByUsername({
+      username: githubContext.actor,
+    });
+    actorType = userData.type;
+  } catch (error) {
+    // Handle 404 for non-user actors (GitHub Apps whose GITHUB_ACTOR
+    // doesn't match any user account, e.g. "Copilot").
+    if (
+      error instanceof Error &&
+      (error.message.includes("Not Found") ||
+        error.message.includes("is not a user"))
+    ) {
+      const botName = githubContext.actor
+        .toLowerCase()
+        .replace(/\[bot\]$/, "");
+      throw new Error(
+        `Workflow initiated by non-human actor: ${botName} (actor not found on GitHub). Add bot to allowed_bots list or use '*' to allow all bots.`,
+      );
+    }
+    throw error;
+  }
 
   console.log(`Actor type: ${actorType}`);
 
   // Check bot permissions if actor is not a User
   if (actorType !== "User") {
-    const allowedBots = githubContext.inputs.allowedBots;
-
-    // Check if all bots are allowed
-    if (allowedBots.trim() === "*") {
-      console.log(
-        `All bots are allowed, skipping human actor check for: ${githubContext.actor}`,
-      );
-      return;
-    }
-
-    // Parse allowed bots list
-    const allowedBotsList = allowedBots
-      .split(",")
-      .map((bot) =>
-        bot
-          .trim()
-          .toLowerCase()
-          .replace(/\[bot\]$/, ""),
-      )
-      .filter((bot) => bot.length > 0);
-
     const botName = githubContext.actor.toLowerCase().replace(/\[bot\]$/, "");
 
-    // Check if specific bot is allowed
+    // Bot not allowed (we already checked allowed_bots above)
-    if (allowedBotsList.includes(botName)) {
-      console.log(
-        `Bot ${botName} is in allowed list, skipping human actor check`,
-      );
-      return;
-    }
-
-    // Bot not allowed
     throw new Error(
       `Workflow initiated by non-human actor: ${botName} (type: ${actorType}). Add bot to allowed_bots list or use '*' to allow all bots.`,
     );

src/github/validation/permissions.ts

@@ -2,6 +2,28 @@ import * as core from "@actions/core";
 import type { ParsedGitHubContext } from "../context";
 import type { Octokit } from "@octokit/rest";
 
+/**
+ * Check if a bot actor is in the allowed bots list.
+ */
+function isAllowedBot(actor: string, allowedBots: string): boolean {
+  const trimmed = allowedBots.trim();
+  if (trimmed === "*") return true;
+  if (!trimmed) return false;
+
+  const allowedList = trimmed
+    .split(",")
+    .map((bot) =>
+      bot
+        .trim()
+        .toLowerCase()
+        .replace(/\[bot\]$/, ""),
+    )
+    .filter((bot) => bot.length > 0);
+
+  const normalizedActor = actor.toLowerCase().replace(/\[bot\]$/, "");
+  return allowedList.includes(normalizedActor);
+}
+
 /**
  * Check if the actor has write permissions to the repository
  * @param octokit - The Octokit REST client
@@ -17,6 +39,7 @@ export async function checkWritePermissions(
   githubTokenProvided?: boolean,
 ): Promise<boolean> {
   const { repository, actor } = context;
+  const allowedBots = context.inputs.allowedBots ?? "";
 
   try {
     core.info(`Checking permissions for actor: ${actor}`);
@@ -43,12 +66,21 @@ export async function checkWritePermissions(
       }
     }
 
-    // Check if the actor is a GitHub App (bot user)
+    // Check if the actor is a GitHub App (bot user with [bot] suffix)
     if (actor.endsWith("[bot]")) {
       core.info(`Actor is a GitHub App: ${actor}`);
       return true;
     }
 
+    // Check if the actor is in the allowed bots list (handles non-[bot] actors
+    // like GitHub Copilot whose GITHUB_ACTOR is "Copilot", not "Copilot[bot]")
+    if (isAllowedBot(actor, allowedBots)) {
+      core.info(
+        `Actor ${actor} is in allowed_bots list, skipping permission check`,
+      );
+      return true;
+    }
+
     // Check permissions directly using the permission endpoint
     const response = await octokit.repos.getCollaboratorPermissionLevel({
       owner: repository.owner,
@@ -67,6 +99,28 @@ export async function checkWritePermissions(
       return false;
     }
   } catch (error) {
+    // Handle 404 errors for non-user actors (e.g. GitHub Apps like Copilot
+    // whose GITHUB_ACTOR doesn't end with [bot]).
+    // The collaborator permission API only works for user accounts.
+    if (
+      error instanceof Error &&
+      error.message.includes("is not a user")
+    ) {
+      core.info(
+        `Actor ${actor} is not a GitHub user (likely a GitHub App). Checking allowed_bots...`,
+      );
+      if (isAllowedBot(actor, allowedBots)) {
+        core.info(
+          `Non-user actor ${actor} is in allowed_bots list, granting access`,
+        );
+        return true;
+      }
+      core.warning(
+        `Non-user actor ${actor} is not in allowed_bots list. Add it to allowed_bots or use '*' to allow all bots.`,
+      );
+      return false;
+    }
+
     core.error(`Failed to check permissions: ${error}`);
     throw new Error(`Failed to check permissions for ${actor}: ${error}`);
   }

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",
+      );
+    });
+  });
 });