Restore prompt to editor on API key validation failure

fixes #77

packages/coding-agent/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- **Prompt Restoration on API Key Error**: When submitting a message fails due to missing API key, the prompt is now restored to the editor instead of being lost. ([#77](https://github.com/badlogic/pi-mono/issues/77))
+
 ## [0.10.2] - 2025-11-27
 
 ### Changed

packages/coding-agent/src/tui/tui-renderer.ts

@@ -418,6 +418,7 @@ export class TuiRenderer {
 					`No API key found for ${currentModel.provider}.\n\n` +
 						`Set the appropriate environment variable or update ~/.pi/agent/models.json`,
 				);
+				this.editor.setText(text);
 				return;
 			}