feat: send additional_permissions in token exchange request

Parse the ADDITIONAL_PERMISSIONS env var and send it as a JSON body
in the OIDC token exchange request. Permissions are merged on top of
the standard defaults (contents: write, pull_requests: write,
issues: write).

docs/configuration.md

@@ -172,9 +172,11 @@ jobs:
 
 **Important Notes**:
 
-- The GitHub token must have the `actions: read` permission in your workflow
+- The GitHub token must have the corresponding permission in your workflow
 - If the permission is missing, Claude will warn you and suggest adding it
-- Currently, only `actions: read` is supported, but the format allows for future extensions
+- Any GitHub App permission can be requested (e.g. `actions: read`, `workflows: write`, `deployments: read`)
+- The GitHub App installation must have the requested permission enabled for it to take effect
+- Standard permissions (`contents: write`, `pull_requests: write`, `issues: write`) are always included and do not need to be specified
 
 ## Custom Environment Variables
 

src/github/token.ts

@@ -16,15 +16,60 @@ async function getOidcToken(): Promise<string> {
   }
 }
 
-async function exchangeForAppToken(oidcToken: string): Promise<string> {
+const DEFAULT_PERMISSIONS: Record<string, string> = {
+  contents: "write",
+  pull_requests: "write",
+  issues: "write",
+};
+
+export function parseAdditionalPermissions():
+  | Record<string, string>
+  | undefined {
+  const raw = process.env.ADDITIONAL_PERMISSIONS;
+  if (!raw || !raw.trim()) {
+    return undefined;
+  }
+
+  const additional: Record<string, string> = {};
+  for (const line of raw.split("\n")) {
+    const trimmed = line.trim();
+    if (!trimmed) continue;
+    const colonIndex = trimmed.indexOf(":");
+    if (colonIndex === -1) continue;
+    const key = trimmed.slice(0, colonIndex).trim();
+    const value = trimmed.slice(colonIndex + 1).trim();
+    if (key && value) {
+      additional[key] = value;
+    }
+  }
+
+  if (Object.keys(additional).length === 0) {
+    return undefined;
+  }
+
+  return { ...DEFAULT_PERMISSIONS, ...additional };
+}
+
+async function exchangeForAppToken(
+  oidcToken: string,
+  permissions?: Record<string, string>,
+): Promise<string> {
+  const headers: Record<string, string> = {
+    Authorization: `Bearer ${oidcToken}`,
+  };
+  const fetchOptions: RequestInit = {
+    method: "POST",
+    headers,
+  };
+
+  if (permissions) {
+    headers["Content-Type"] = "application/json";
+    fetchOptions.body = JSON.stringify({ permissions });
+  }
+
   const response = await fetch(
     "https://api.anthropic.com/api/github/github-app-token-exchange",
-    {
-      method: "POST",
-      headers: {
-        Authorization: `Bearer ${oidcToken}`,
-      },
-    },
+    fetchOptions,
   );
 
   if (!response.ok) {
@@ -89,9 +134,11 @@ export async function setupGitHubToken(): Promise<string> {
     const oidcToken = await retryWithBackoff(() => getOidcToken());
     console.log("OIDC token successfully obtained");
 
+    const permissions = parseAdditionalPermissions();
+
     console.log("Exchanging OIDC token for app token...");
     const appToken = await retryWithBackoff(() =>
-      exchangeForAppToken(oidcToken),
+      exchangeForAppToken(oidcToken, permissions),
     );
     console.log("App token successfully obtained");
 

test/parse-permissions.test.ts

@@ -0,0 +1,97 @@
+import { describe, expect, test, beforeEach, afterEach } from "bun:test";
+import { parseAdditionalPermissions } from "../src/github/token";
+
+describe("parseAdditionalPermissions", () => {
+  let originalEnv: string | undefined;
+
+  beforeEach(() => {
+    originalEnv = process.env.ADDITIONAL_PERMISSIONS;
+  });
+
+  afterEach(() => {
+    if (originalEnv === undefined) {
+      delete process.env.ADDITIONAL_PERMISSIONS;
+    } else {
+      process.env.ADDITIONAL_PERMISSIONS = originalEnv;
+    }
+  });
+
+  test("returns undefined when env var is not set", () => {
+    delete process.env.ADDITIONAL_PERMISSIONS;
+    expect(parseAdditionalPermissions()).toBeUndefined();
+  });
+
+  test("returns undefined when env var is empty string", () => {
+    process.env.ADDITIONAL_PERMISSIONS = "";
+    expect(parseAdditionalPermissions()).toBeUndefined();
+  });
+
+  test("returns undefined when env var is only whitespace", () => {
+    process.env.ADDITIONAL_PERMISSIONS = "   \n  \n  ";
+    expect(parseAdditionalPermissions()).toBeUndefined();
+  });
+
+  test("parses single permission and merges with defaults", () => {
+    process.env.ADDITIONAL_PERMISSIONS = "actions: read";
+    expect(parseAdditionalPermissions()).toEqual({
+      contents: "write",
+      pull_requests: "write",
+      issues: "write",
+      actions: "read",
+    });
+  });
+
+  test("parses multiple permissions", () => {
+    process.env.ADDITIONAL_PERMISSIONS = "actions: read\nworkflows: write";
+    expect(parseAdditionalPermissions()).toEqual({
+      contents: "write",
+      pull_requests: "write",
+      issues: "write",
+      actions: "read",
+      workflows: "write",
+    });
+  });
+
+  test("additional permissions can override defaults", () => {
+    process.env.ADDITIONAL_PERMISSIONS = "contents: read";
+    expect(parseAdditionalPermissions()).toEqual({
+      contents: "read",
+      pull_requests: "write",
+      issues: "write",
+    });
+  });
+
+  test("handles extra whitespace around keys and values", () => {
+    process.env.ADDITIONAL_PERMISSIONS = "  actions :  read  ";
+    expect(parseAdditionalPermissions()).toEqual({
+      contents: "write",
+      pull_requests: "write",
+      issues: "write",
+      actions: "read",
+    });
+  });
+
+  test("skips empty lines", () => {
+    process.env.ADDITIONAL_PERMISSIONS =
+      "actions: read\n\n\nworkflows: write\n\n";
+    expect(parseAdditionalPermissions()).toEqual({
+      contents: "write",
+      pull_requests: "write",
+      issues: "write",
+      actions: "read",
+      workflows: "write",
+    });
+  });
+
+  test("skips lines without colons", () => {
+    process.env.ADDITIONAL_PERMISSIONS =
+      "actions: read\ninvalid line\nworkflows: write";
+    expect(parseAdditionalPermissions()).toEqual({
+      contents: "write",
+      pull_requests: "write",
+      issues: "write",
+      actions: "read",
+      workflows: "write",
+    });
+  });
+});