feat(tui): show progress and confirmation when forking a session

Forking gave no feedback: the dialog stayed open during the (potentially
slow) fork, then silently navigated to a near-identical copy. Now the
dialog shows a "Forking session…" spinner while the fork runs, then lands
on the new session with a "Forked session" toast (or an error toast on
failure).

Mount <Toast/> once in the app shell instead of per-route, so a toast
fired around route.navigate survives the route remount.

packages/opencode/src/cli/cmd/tui/app.tsx

@@ -50,7 +50,7 @@ import { FrecencyProvider } from "./component/prompt/frecency"
 import { PromptStashProvider } from "./component/prompt/stash"
 import { DialogAlert } from "./ui/dialog-alert"
 import { DialogConfirm } from "./ui/dialog-confirm"
-import { ToastProvider, useToast } from "./ui/toast"
+import { Toast, ToastProvider, useToast } from "./ui/toast"
 import { createExit, ExitProvider, useExit, type Exit } from "./context/exit"
 import { Session as SessionApi } from "@/session/session"
 import { TuiEvent } from "./event"
@@ -1072,6 +1072,8 @@ function App(props: { onSnapshot?: () => Promise<string[]> }) {
           <TuiPluginRuntime.Slot name="app_bottom" />
         </box>
         <TuiPluginRuntime.Slot name="app" />
+        {/* One Toast for the whole app, not per-route, so toasts survive route.navigate */}
+        <Toast />
       </Show>
       <StartupLoading ready={ready} />
     </box>

packages/opencode/src/cli/cmd/tui/routes/home.tsx

@@ -2,7 +2,6 @@ import { Prompt, type PromptRef } from "@tui/component/prompt"
 import { createEffect, createMemo, createSignal, onMount } from "solid-js"
 import { Logo } from "../component/logo"
 import { useSync } from "../context/sync"
-import { Toast } from "../ui/toast"
 import { useArgs } from "../context/args"
 import { useRouteData } from "@tui/context/route"
 import { usePromptRef } from "../context/prompt"
@@ -83,7 +82,6 @@ export function Home() {
         </box>
         <TuiPluginRuntime.Slot name="home_bottom" />
         <box flexGrow={1} minHeight={0} />
-        <Toast />
       </box>
       <box width="100%" flexShrink={0}>
         <TuiPluginRuntime.Slot name="home_footer" mode="single_winner" />

packages/opencode/src/cli/cmd/tui/routes/session/dialog-fork-from-timeline.tsx

@@ -5,6 +5,8 @@ import type { TextPart } from "@opencode-ai/sdk/v2"
 import { Locale } from "@/util/locale"
 import { useSDK } from "@tui/context/sdk"
 import { useRoute } from "@tui/context/route"
+import { useToast } from "../../ui/toast"
+import { Spinner } from "../../component/spinner"
 import { useDialog, type DialogContext } from "../../ui/dialog"
 import type { PromptInfo } from "@tui/component/prompt/history"
 import { strip } from "@tui/component/prompt/part"
@@ -14,24 +16,37 @@ export function DialogForkFromTimeline(props: { sessionID: string; onMove: (mess
   const dialog = useDialog()
   const sdk = useSDK()
   const route = useRoute()
+  const toast = useToast()
 
   onMount(() => {
     dialog.setSize("large")
   })
 
+  // Forking a large session can take a moment, so swap the dialog to a progress view instead of
+  // leaving it open (which looks frozen), then navigate to the fork and confirm with a toast.
+  const fork = async (dialog: DialogContext, messageID?: string, prompt?: PromptInfo) => {
+    dialog.replace(() => (
+      <box paddingLeft={2} paddingRight={2} paddingBottom={1}>
+        <Spinner>Forking session…</Spinner>
+      </box>
+    ))
+    const forked = await sdk.client.session.fork({ sessionID: props.sessionID, messageID })
+    if (!forked.data) {
+      toast.show({ variant: "error", message: "Failed to fork session" })
+      dialog.clear()
+      return
+    }
+    route.navigate({ sessionID: forked.data.id, type: "session", prompt })
+    dialog.clear()
+    toast.show({ variant: "success", message: "Forked session", duration: 4000 })
+  }
+
   const options = createMemo((): DialogSelectOption<string | undefined>[] => {
     const messages = sync.data.message[props.sessionID] ?? []
     const fullSession = {
       title: "Full session",
       value: undefined,
-      onSelect: async (dialog: DialogContext) => {
-        const forked = await sdk.client.session.fork({ sessionID: props.sessionID })
-        route.navigate({
-          sessionID: forked.data!.id,
-          type: "session",
-        })
-        dialog.clear()
-      },
+      onSelect: fork,
     } satisfies DialogSelectOption<string | undefined>
     const result = [] as DialogSelectOption<string | undefined>[]
     for (const message of messages) {
@@ -44,13 +59,8 @@ export function DialogForkFromTimeline(props: { sessionID: string; onMove: (mess
         title: part.text.replace(/\n/g, " "),
         value: message.id,
         footer: Locale.time(message.time.created),
-        onSelect: async (dialog) => {
-          const forked = await sdk.client.session.fork({
-            sessionID: props.sessionID,
-            messageID: message.id,
-          })
-          const parts = sync.data.part[message.id] ?? []
-          const prompt = parts.reduce(
+        onSelect: (dialog) => {
+          const prompt = (sync.data.part[message.id] ?? []).reduce(
             (agg, part) => {
               if (part.type === "text") {
                 if (!part.synthetic) agg.input += part.text
@@ -60,12 +70,7 @@ export function DialogForkFromTimeline(props: { sessionID: string; onMove: (mess
             },
             { input: "", parts: [] as PromptInfo["parts"] },
           )
-          route.navigate({
-            sessionID: forked.data!.id,
-            type: "session",
-            prompt,
-          })
-          dialog.clear()
+          return fork(dialog, message.id, prompt)
         },
       })
     }

packages/opencode/src/cli/cmd/tui/routes/session/index.tsx

@@ -67,7 +67,7 @@ import { LANGUAGE_EXTENSIONS } from "@/lsp/language"
 import parsers from "../../../../../../parsers-config.ts"
 import * as Clipboard from "../../util/clipboard"
 import { errorMessage } from "@/util/error"
-import { Toast, useToast } from "../../ui/toast"
+import { useToast } from "../../ui/toast"
 import { useKV } from "../../context/kv.tsx"
 import * as Editor from "../../util/editor"
 import stripAnsi from "strip-ansi"
@@ -1263,7 +1263,6 @@ export function Session() {
                 </Show>
               </box>
             </Show>
-            <Toast />
           </box>
           <Show when={sidebarVisible()}>
             <Switch>