diff --git a/packages/opencode/src/cli/cmd/tui/app.tsx b/packages/opencode/src/cli/cmd/tui/app.tsx
index 4b177e292cf..0d553d935ba 100644
--- a/packages/opencode/src/cli/cmd/tui/app.tsx
+++ b/packages/opencode/src/cli/cmd/tui/app.tsx
@@ -105,6 +105,7 @@ export function tui(input: {
   directory?: string
   fetch?: typeof fetch
   events?: EventSource
+  startServer?: () => Promise<string>
   onExit?: () => Promise<void>
 }) {
   // promise to prevent immediate exit
@@ -131,6 +132,7 @@ export function tui(input: {
                         directory={input.directory}
                         fetch={input.fetch}
                         events={input.events}
+                        startServer={input.startServer}
                       >
                         <SyncProvider>
                           <ThemeProvider mode={mode}>
@@ -491,8 +493,36 @@ function App() {
     {
       title: "Open WebUI",
       value: "webui.open",
-      onSelect: () => {
-        open(sdk.url).catch(() => {})
+      onSelect: async () => {
+        let url = sdk.url
+        if (sdk.url.includes("opencode.internal")) {
+          if (!sdk.startServer) {
+            toast.show({
+              variant: "warning",
+              message: "WebUI requires server mode. Restart with: opencode --port 4096",
+              duration: 5000,
+            })
+            dialog.clear()
+            return
+          }
+          toast.show({
+            variant: "info",
+            message: "Starting server...",
+            duration: 2000,
+          })
+          try {
+            url = await sdk.startServer()
+          } catch (e) {
+            toast.show({
+              variant: "error",
+              message: "Failed to start server",
+              duration: 3000,
+            })
+            dialog.clear()
+            return
+          }
+        }
+        open(url).catch(() => {})
         dialog.clear()
       },
       category: "System",
diff --git a/packages/opencode/src/cli/cmd/tui/context/sdk.tsx b/packages/opencode/src/cli/cmd/tui/context/sdk.tsx
index 3339e7b00d2..549fd336678 100644
--- a/packages/opencode/src/cli/cmd/tui/context/sdk.tsx
+++ b/packages/opencode/src/cli/cmd/tui/context/sdk.tsx
@@ -9,7 +9,13 @@ export type EventSource = {
 
 export const { use: useSDK, provider: SDKProvider } = createSimpleContext({
   name: "SDK",
-  init: (props: { url: string; directory?: string; fetch?: typeof fetch; events?: EventSource }) => {
+  init: (props: {
+    url: string
+    directory?: string
+    fetch?: typeof fetch
+    events?: EventSource
+    startServer?: () => Promise<string>
+  }) => {
     const abort = new AbortController()
     const sdk = createOpencodeClient({
       baseUrl: props.url,
@@ -89,6 +95,6 @@ export const { use: useSDK, provider: SDKProvider } = createSimpleContext({
       if (timer) clearTimeout(timer)
     })
 
-    return { client: sdk, event: emitter, url: props.url }
+    return { client: sdk, event: emitter, url: props.url, startServer: props.startServer }
   },
 })
diff --git a/packages/opencode/src/cli/cmd/tui/thread.ts b/packages/opencode/src/cli/cmd/tui/thread.ts
index 05714268545..3e51f391f28 100644
--- a/packages/opencode/src/cli/cmd/tui/thread.ts
+++ b/packages/opencode/src/cli/cmd/tui/thread.ts
@@ -151,6 +151,12 @@ export const TuiThreadCommand = cmd({
         model: args.model,
         prompt,
       },
+      startServer: shouldStartServer
+        ? undefined
+        : async () => {
+            const server = await client.call("server", networkOpts)
+            return server.url
+          },
       onExit: async () => {
         await client.call("shutdown", undefined)
       },