feat: implement incremental message updates for improved UI performance

src/core/task/Task.ts

@@ -562,7 +562,14 @@ export class Task extends EventEmitter<TaskEvents> implements TaskLike {
 	private async addToClineMessages(message: ClineMessage) {
 		this.clineMessages.push(message)
 		const provider = this.providerRef.deref()
-		await provider?.postStateToWebview()
+		// Send only the new message instead of the entire state
+		if (provider) {
+			try {
+				await provider.postMessageToWebview({ type: "messageCreated", clineMessage: message })
+			} catch (error) {
+				// provider.postMessageToWebview already logs; leave as non-fatal
+			}
+		}
 		this.emit(RooCodeEventName.Message, { action: "created", message })
 		await this.saveClineMessages()
 
@@ -584,7 +591,13 @@ export class Task extends EventEmitter<TaskEvents> implements TaskLike {
 
 	private async updateClineMessage(message: ClineMessage) {
 		const provider = this.providerRef.deref()
-		await provider?.postMessageToWebview({ type: "messageUpdated", clineMessage: message })
+		if (provider) {
+			try {
+				await provider.postMessageToWebview({ type: "messageUpdated", clineMessage: message })
+			} catch (error) {
+				// provider.postMessageToWebview already logs; leave as non-fatal
+			}
+		}
 		this.emit(RooCodeEventName.Message, { action: "updated", message })
 
 		const shouldCaptureMessage = message.partial !== true && CloudService.isEnabled()
@@ -1172,6 +1185,9 @@ export class Task extends EventEmitter<TaskEvents> implements TaskLike {
 		// the task first.
 		this.apiConversationHistory = await this.getSavedApiConversationHistory()
 
+		// Send initial state to webview (this will now handle incremental message loading)
+		await this.providerRef.deref()?.postStateToWebview()
+
 		const lastClineMessage = this.clineMessages
 			.slice()
 			.reverse()

src/core/webview/ClineProvider.ts

@@ -888,7 +888,15 @@ export class ClineProvider
 	}
 
 	public async postMessageToWebview(message: ExtensionMessage) {
-		await this.view?.webview.postMessage(message)
+		try {
+			await this.view?.webview.postMessage(message)
+		} catch (error) {
+			// Guard against unhandled promise rejections from webview messaging
+			const errMsg =
+				error instanceof Error ? error.message : typeof error === "string" ? error : JSON.stringify(error)
+			this.log(`[postMessageToWebview] failed to post message '${message.type}': ${errMsg}`)
+			// Non-fatal: continue without throwing to avoid crashing extension host
+		}
 	}
 
 	private async getHMRHtmlContent(webview: vscode.Webview): Promise<string> {
@@ -1554,7 +1562,7 @@ export class ClineProvider
 
 		// Check MDM compliance and send user to account tab if not compliant
 		if (!this.checkMdmCompliance()) {
-			await this.postMessageToWebview({ type: "action", action: "accountButtonClicked" })
+			this.postMessageToWebview({ type: "action", action: "accountButtonClicked" })
 		}
 	}
 

src/shared/ExtensionMessage.ts

@@ -66,6 +66,7 @@ export interface ExtensionMessage {
 		| "workspaceUpdated"
 		| "invoke"
 		| "messageUpdated"
+		| "messageCreated"
 		| "mcpServers"
 		| "enhancedPrompt"
 		| "commitSearchResults"

webview-ui/src/context/ExtensionStateContext.tsx

@@ -333,6 +333,14 @@ export const ExtensionStateContextProvider: React.FC<{ children: React.ReactNode
 					setCommands(message.commands ?? [])
 					break
 				}
+				case "messageCreated": {
+					const clineMessage = message.clineMessage!
+					setState((prevState) => ({
+						...prevState,
+						clineMessages: [...prevState.clineMessages, clineMessage],
+					}))
+					break
+				}
 				case "messageUpdated": {
 					const clineMessage = message.clineMessage!
 					setState((prevState) => {