Merge createArtifact and updateArtifact into createOrUpdateArtifact

LLMs get confused about when to use create vs update. The single function
automatically detects if the artifact exists and chooses the right operation.

Changes:
- Replace createArtifact/updateArtifact with createOrUpdateArtifact in runtime
- Update handler to check existence and use appropriate command (create/rewrite)
- Simplify prompt documentation and examples

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

@@ -90,9 +90,13 @@ export class ArtifactsRuntimeProvider implements SandboxRuntimeProvider {
 				return content;
 			};
 
-			(window as any).createArtifact = async (filename: string, content: any, mimeType?: string): Promise<void> => {
+			(window as any).createOrUpdateArtifact = async (
+				filename: string,
+				content: any,
+				mimeType?: string,
+			): Promise<void> => {
 				if (!(window as any).sendRuntimeMessage) {
-					throw new Error("Cannot create artifacts in offline mode (read-only)");
+					throw new Error("Cannot create/update artifacts in offline mode (read-only)");
 				}
 
 				let finalContent = content;
@@ -105,30 +109,7 @@ export class ArtifactsRuntimeProvider implements SandboxRuntimeProvider {
 
 				const response = await (window as any).sendRuntimeMessage({
 					type: "artifact-operation",
-					action: "create",
-					filename,
-					content: finalContent,
-					mimeType,
-				});
-				if (!response.success) throw new Error(response.error);
-			};
-
-			(window as any).updateArtifact = async (filename: string, content: any, mimeType?: string): Promise<void> => {
-				if (!(window as any).sendRuntimeMessage) {
-					throw new Error("Cannot update artifacts in offline mode (read-only)");
-				}
-
-				let finalContent = content;
-				// Auto-stringify .json files
-				if (isJsonFile(filename) && typeof content !== "string") {
-					finalContent = JSON.stringify(content, null, 2);
-				} else if (typeof content !== "string") {
-					finalContent = JSON.stringify(content, null, 2);
-				}
-
-				const response = await (window as any).sendRuntimeMessage({
-					type: "artifact-operation",
-					action: "update",
+					action: "createOrUpdate",
 					filename,
 					content: finalContent,
 					mimeType,
@@ -176,40 +157,23 @@ export class ArtifactsRuntimeProvider implements SandboxRuntimeProvider {
 					break;
 				}
 
-				case "create": {
+				case "createOrUpdate": {
 					try {
-						await this.artifactsPanel.tool.execute("", {
-							command: "create",
-							filename,
-							content,
-						});
-						this.agent?.appendMessage({
-							role: "artifact",
-							action: "create",
-							filename,
-							content,
-							title: filename,
-							timestamp: new Date().toISOString(),
-						});
-						respond({ success: true });
-					} catch (err: any) {
-						respond({ success: false, error: err.message });
-					}
-					break;
-				}
+						const exists = this.artifactsPanel.artifacts.has(filename);
+						const command = exists ? "rewrite" : "create";
+						const action = exists ? "update" : "create";
 
-				case "update": {
-					try {
 						await this.artifactsPanel.tool.execute("", {
-							command: "rewrite",
+							command,
 							filename,
 							content,
 						});
 						this.agent?.appendMessage({
 							role: "artifact",
-							action: "update",
+							action,
 							filename,
 							content,
+							...(action === "create" && { title: filename }),
 							timestamp: new Date().toISOString(),
 						});
 						respond({ success: true });

packages/web-ui/src/prompts/tool-prompts.ts

@@ -193,29 +193,26 @@ Artifact Management (persistent session files you can access/modify programmatic
   * Auto-parses .json files to objects, otherwise returns raw string content
   * Example: const data = await getArtifact('data.json'); // Returns parsed object
   * Example: const markdown = await getArtifact('notes.md'); // Returns string
-- await createArtifact(filename, content) - Create new persistent artifact
+- await createOrUpdateArtifact(filename, content, mimeType?) - Create or update a persistent artifact
+  * Automatically creates if new, updates if exists (no need to check hasArtifact first)
   * Auto-stringifies objects for .json files
-  * Example: await createArtifact('data.json', {items: []}) // Auto-stringifies
-  * Example: await createArtifact('research-notes.md', '# Research Notes\\n', 'text/markdown')
-- await updateArtifact(filename, content) - Completely replace artifact content
-  * Auto-stringifies objects for .json files
-  * Full content replacement (not diff-based)
-  * Example: const data = await getArtifact('data.json'); data.items.push(newItem); await updateArtifact('data.json', data);
-  * Example: await updateArtifact('research-notes.md', updatedMarkdown, 'text/markdown')
+  * Example: await createOrUpdateArtifact('data.json', {items: []}) // Auto-stringifies
+  * Example: await createOrUpdateArtifact('research-notes.md', '# Research Notes\\n', 'text/markdown')
+  * Full content replacement (not diff-based) when updating
 - await deleteArtifact(filename) - Delete an artifact
   * Example: await deleteArtifact('old-notes.md')
 
 Powerful pattern for evolving data:
   const data = await hasArtifact('data.json') ? await getArtifact('data.json') : {items: []};
   data.items.push(newScrapedItem);
-  await (await hasArtifact('data.json') ? updateArtifact : createArtifact)('data.json', data);
+  await createOrUpdateArtifact('data.json', data);
 
-Binary data must be converted to a base64 string before passing to createArtifact or updateArtifact.
+Binary data must be converted to a base64 string before passing to createOrUpdateArtifact.
 Example:
   const blob = await new Promise(resolve => canvas.toBlob(resolve, 'image/png'));
   const arrayBuffer = await blob.arrayBuffer();
   const base64 = btoa(String.fromCharCode(...new Uint8Array(arrayBuffer)));
-  await createArtifact('image.png', base64);
+  await createOrUpdateArtifact('image.png', base64);
 `;
 
 // ============================================================================