feat: add --api-key flag to set provider API keys as env vars

aider/args.py

@@ -779,6 +779,13 @@ def get_parser(default_config_files, git_root):
         help="Set an environment variable (can be used multiple times)",
         default=[],
     )
+    group.add_argument(
+        "--api-key",
+        action="append",
+        metavar="PROVIDER=KEY",
+        help="Set an API key for a provider (eg: --api-key anthropic=sk-123)",
+        default=[],
+    )
 
     ##########
     group = parser.add_argument_group("Voice Settings")

aider/main.py

@@ -537,6 +537,18 @@ def main(argv=None, input=None, output=None, force_git_root=None, return_coder=F
                 io.tool_output("Format should be: ENV_VAR_NAME=value")
                 return 1
 
+    # Process any API keys set via --api-key
+    if args.api_key:
+        for api_setting in args.api_key:
+            try:
+                provider, key = api_setting.split("=", 1)
+                env_var = f"{provider.strip().upper()}_API_KEY"
+                os.environ[env_var] = key.strip()
+            except ValueError:
+                io.tool_error(f"Invalid --api-key format: {api_setting}")
+                io.tool_output("Format should be: provider=key")
+                return 1
+
     analytics = Analytics(logfile=args.analytics_log, permanently_disable=args.analytics_disable)
     if args.analytics is not False:
         if analytics.need_to_ask(args.analytics):

tests/basic/test_main.py

@@ -706,6 +706,29 @@ class TestMain(TestCase):
             result = main(["--set-env", "INVALID_FORMAT", "--exit", "--yes"])
             self.assertEqual(result, 1)
 
+    def test_api_key_single(self):
+        # Test setting a single API key
+        with GitTemporaryDirectory():
+            main(["--api-key", "anthropic=test-key", "--exit", "--yes"])
+            self.assertEqual(os.environ.get("ANTHROPIC_API_KEY"), "test-key")
+
+    def test_api_key_multiple(self):
+        # Test setting multiple API keys
+        with GitTemporaryDirectory():
+            main([
+                "--api-key", "anthropic=key1",
+                "--api-key", "openai=key2",
+                "--exit", "--yes"
+            ])
+            self.assertEqual(os.environ.get("ANTHROPIC_API_KEY"), "key1")
+            self.assertEqual(os.environ.get("OPENAI_API_KEY"), "key2")
+
+    def test_api_key_invalid_format(self):
+        # Test invalid format handling
+        with GitTemporaryDirectory():
+            result = main(["--api-key", "INVALID_FORMAT", "--exit", "--yes"])
+            self.assertEqual(result, 1)
+
     def test_invalid_edit_format(self):
         with GitTemporaryDirectory():
             with patch("aider.io.InputOutput.offer_url") as mock_offer_url: