Pass return value through execution-complete message instead of logging

- Return value now passed to window.complete(error, returnValue)
- execution-complete message includes returnValue field
- SandboxResult interface updated to include returnValue
- executionConsumer passes returnValue in resolved promise
- Return values properly captured and available to callers

packages/web-ui/src/components/SandboxedIframe.ts

@@ -16,6 +16,7 @@ export interface SandboxResult {
 	console: Array<{ type: string; text: string }>;
 	files?: SandboxFile[];
 	error?: { message: string; stack: string };
+	returnValue?: any;
 }
 
 /**
@@ -189,7 +190,7 @@ export class SandboxIframe extends LitElement {
 					} else if (message.type === "execution-complete") {
 						completed = true;
 						cleanup();
-						resolve({ success: true, console: logs, files });
+						resolve({ success: true, console: logs, files, returnValue: message.returnValue });
 						return true;
 					} else if (message.type === "execution-error") {
 						completed = true;
@@ -335,11 +336,6 @@ export class SandboxIframe extends LitElement {
 
 				const returnValue = await userCodeFunc();
 
-				// Log return value if present
-				if (returnValue !== undefined) {
-					console.log('Return value:', returnValue);
-				}
-
 				// Call completion callbacks before complete()
 				if (window.__completionCallbacks && window.__completionCallbacks.length > 0) {
 					try {
@@ -349,7 +345,7 @@ export class SandboxIframe extends LitElement {
 					}
 				}
 
-				await window.complete();
+				await window.complete(null, returnValue);
 			} catch (error) {
 				console.error(error?.stack || error?.message || String(error));
 

packages/web-ui/src/components/sandbox/ConsoleRuntimeProvider.ts

@@ -120,7 +120,7 @@ export class ConsoleRuntimeProvider implements SandboxRuntimeProvider {
 
 			// Expose complete() method for user code to call
 			let completionSent = false;
-			(window as any).complete = async (error?: { message: string; stack: string }) => {
+			(window as any).complete = async (error?: { message: string; stack: string }, returnValue?: any) => {
 				if (completionSent) return;
 				completionSent = true;
 
@@ -138,6 +138,7 @@ export class ConsoleRuntimeProvider implements SandboxRuntimeProvider {
 						console.log("Reporting execution complete");
 						await (window as any).sendRuntimeMessage({
 							type: "execution-complete",
+							returnValue,
 						});
 						console.log("Execution completed");
 					}