diff --git a/plain2code.py b/plain2code.py
index b4e2cd7..904d496 100644
--- a/plain2code.py
+++ b/plain2code.py
@@ -17,7 +17,7 @@
 from module_renderer import ModuleRenderer
 from plain2code_arguments import parse_arguments
 from plain2code_console import console
-from plain2code_exceptions import PlainSyntaxError
+from plain2code_exceptions import MissingAPIKey, PlainSyntaxError
 from plain2code_logger import (
     CrashLogHandler,
     IndentedFormatter,
@@ -208,6 +208,12 @@ def main():
     run_state = RunState(spec_filename=args.filename, replay_with=args.replay_with)
 
     try:
+        # Validate API key is present
+        if not args.api_key:
+            raise MissingAPIKey(
+                "API key is required. Please set the CODEPLAIN_API_KEY environment variable or provide it with the --api-key argument."
+            )
+
         render(args, run_state, codeplain_api, event_bus)
     except InvalidFridArgument as e:
         console.error(f"Error rendering plain code: {str(e)}.\n")
@@ -237,6 +243,8 @@ def main():
         console.error(f"Error rendering plain code: {str(e)}\n")
         console.debug(f"Render ID: {run_state.render_id}")
         dump_crash_logs(args)
+    except MissingAPIKey as e:
+        console.error(f"Missing API key: {str(e)}\n")
     except Exception as e:
         console.error(f"Error rendering plain code: {str(e)}\n")
         console.debug(f"Render ID: {run_state.render_id}")
diff --git a/plain2code_arguments.py b/plain2code_arguments.py
index 35c7db4..60e3c2d 100644
--- a/plain2code_arguments.py
+++ b/plain2code_arguments.py
@@ -5,10 +5,6 @@
 from plain2code_read_config import get_args_from_config
 
 CODEPLAIN_API_KEY = os.getenv("CODEPLAIN_API_KEY")
-if not CODEPLAIN_API_KEY:
-    CLAUDE_API_KEY = os.getenv("CLAUDE_API_KEY")
-    if not CLAUDE_API_KEY:
-        raise ValueError("CODEPLAIN_API_KEY or CLAUDE_API_KEY environment variable is not set")
 
 
 DEFAULT_BUILD_FOLDER = "plain_modules"
diff --git a/plain2code_exceptions.py b/plain2code_exceptions.py
index e48e34e..cafdbbb 100644
--- a/plain2code_exceptions.py
+++ b/plain2code_exceptions.py
@@ -43,3 +43,7 @@ class MultipleRendersFound(Exception):
 
 class UnexpectedState(Exception):
     pass
+
+
+class MissingAPIKey(Exception):
+    pass