diff --git a/packages/opencode/src/cli/cmd/run.ts b/packages/opencode/src/cli/cmd/run.ts
index bd9d29b4deb..1aeb9afad13 100644
--- a/packages/opencode/src/cli/cmd/run.ts
+++ b/packages/opencode/src/cli/cmd/run.ts
@@ -1,6 +1,7 @@
 import type { Argv } from "yargs"
 import path from "path"
 import { UI } from "../ui"
+import { buildOsc9Notification } from "../util/osc"
 import { cmd } from "./cmd"
 import { Flag } from "../../flag/flag"
 import { bootstrap } from "../bootstrap"
@@ -151,6 +152,46 @@ export const RunCommand = cmd({
         return false
       }
 
+      const notifiedMessages = new Set<string>()
+      const messageTextParts = new Map<string, Map<string, string>>()
+
+      const recordTextPart = (part: { messageID: string; id: string; text: string; synthetic?: boolean; ignored?: boolean }) => {
+        if (part.synthetic || part.ignored || !part.text) return
+        let perMessage = messageTextParts.get(part.messageID)
+        if (!perMessage) {
+          perMessage = new Map()
+          messageTextParts.set(part.messageID, perMessage)
+        }
+        perMessage.set(part.id, part.text)
+      }
+
+      const buildPreview = (messageID: string) => {
+        const parts = messageTextParts.get(messageID)
+        if (!parts) return ""
+        return Array.from(parts.values()).join("\n")
+      }
+
+      const canNotify = () => process.stdout.isTTY && args.format !== "json"
+
+      const notifyOsc9 = (messageID: string) => {
+        if (!canNotify()) return
+        const preview = buildPreview(messageID)
+        const payload = buildOsc9Notification(preview, { fallback: "OpenCode response complete" })
+        if (!payload) return
+        process.stdout.write(payload)
+      }
+
+      const shouldNotifyAssistant = (info: {
+        role: string
+        time?: { completed?: number }
+        finish?: string
+      }) => {
+        if (info.role !== "assistant") return false
+        if (!info.time?.completed) return false
+        if (!info.finish) return true
+        return !["tool-calls", "unknown"].includes(info.finish)
+      }
+
       const events = await sdk.event.subscribe()
       let errorMsg: string | undefined
 
@@ -160,6 +201,10 @@ export const RunCommand = cmd({
             const part = event.properties.part
             if (part.sessionID !== sessionID) continue
 
+            if (part.type === "text") {
+              recordTextPart(part)
+            }
+
             if (part.type === "tool" && part.state.status === "completed") {
               if (outputJsonEvent("tool_use", { part })) continue
               const [tool, color] = TOOL[part.tool] ?? [part.tool, UI.Style.TEXT_INFO_BOLD]
@@ -190,6 +235,17 @@ export const RunCommand = cmd({
             }
           }
 
+          if (event.type === "message.updated") {
+            const info = event.properties.info
+            if (info.sessionID !== sessionID) continue
+            if (info.role !== "assistant" || !info.time?.completed) continue
+            if (shouldNotifyAssistant(info) && !notifiedMessages.has(info.id)) {
+              notifiedMessages.add(info.id)
+              notifyOsc9(info.id)
+            }
+            messageTextParts.delete(info.id)
+          }
+
           if (event.type === "session.error") {
             const props = event.properties
             if (props.sessionID !== sessionID || !props.error) continue
diff --git a/packages/opencode/src/cli/cmd/tui/app.tsx b/packages/opencode/src/cli/cmd/tui/app.tsx
index 91be02bb978..25413861b83 100644
--- a/packages/opencode/src/cli/cmd/tui/app.tsx
+++ b/packages/opencode/src/cli/cmd/tui/app.tsx
@@ -35,6 +35,7 @@ import { ArgsProvider, useArgs, type Args } from "./context/args"
 import open from "open"
 import { writeHeapSnapshot } from "v8"
 import { PromptRefProvider, usePromptRef } from "./context/prompt"
+import { buildOsc9Notification } from "../../util/osc"
 
 async function getTerminalBackgroundColor(): Promise<"dark" | "light"> {
   // can't set raw mode if not a TTY
@@ -178,6 +179,61 @@ function App() {
   const sync = useSync()
   const exit = useExit()
   const promptRef = usePromptRef()
+  const notifiedMessages = new Set<string>()
+  const messageTextParts = new Map<string, Map<string, string>>()
+
+  const recordTextPart = (part: {
+    messageID: string
+    id: string
+    text: string
+    synthetic?: boolean
+    ignored?: boolean
+  }) => {
+    if (part.synthetic || part.ignored || !part.text) return
+    let perMessage = messageTextParts.get(part.messageID)
+    if (!perMessage) {
+      perMessage = new Map()
+      messageTextParts.set(part.messageID, perMessage)
+    }
+    perMessage.set(part.id, part.text)
+  }
+
+  const buildPreview = (messageID: string) => {
+    const parts = sync.data.part[messageID]
+    const textParts: string[] = []
+    if (parts) {
+      for (const part of parts) {
+        if (part.type !== "text" || part.synthetic || part.ignored) continue
+        textParts.push(part.text)
+      }
+    }
+    if (textParts.length === 0) {
+      const cached = messageTextParts.get(messageID)
+      if (cached) textParts.push(...cached.values())
+    }
+    return textParts.join("\n")
+  }
+
+  const notifyOsc9 = (messageID: string) => {
+    if (!process.stdout.isTTY) return
+    const preview = buildPreview(messageID)
+    const payload = buildOsc9Notification(preview, { fallback: "OpenCode response complete" })
+    if (!payload) return
+    // @ts-expect-error writeOut is not in type definitions
+    renderer.writeOut(payload)
+    messageTextParts.delete(messageID)
+  }
+
+  const shouldNotifyAssistant = (info: {
+    role: string
+    time?: { completed?: number }
+    finish?: string
+  }) => {
+    if (info.role !== "assistant") return false
+    if (!info.time?.completed) return false
+    if (!info.finish) return true
+    return !["tool-calls", "unknown"].includes(info.finish)
+  }
 
   // Wire up console copy-to-clipboard via opentui's onCopySelection callback
   renderer.console.onCopySelection = async (text: string) => {
@@ -537,6 +593,21 @@ function App() {
     }
   })
 
+  sdk.event.on("message.part.updated", (evt) => {
+    const part = evt.properties.part
+    if (part.type === "text") recordTextPart(part)
+  })
+
+  sdk.event.on("message.updated", (evt) => {
+    const info = evt.properties.info
+    if (info.role !== "assistant" || !info.time?.completed) return
+    if (shouldNotifyAssistant(info) && !notifiedMessages.has(info.id)) {
+      notifiedMessages.add(info.id)
+      notifyOsc9(info.id)
+    }
+    messageTextParts.delete(info.id)
+  })
+
   sdk.event.on(TuiEvent.CommandExecute.type, (evt) => {
     command.trigger(evt.properties.command)
   })
diff --git a/packages/opencode/src/cli/util/osc.ts b/packages/opencode/src/cli/util/osc.ts
new file mode 100644
index 00000000000..3d56435d215
--- /dev/null
+++ b/packages/opencode/src/cli/util/osc.ts
@@ -0,0 +1,36 @@
+const OSC9_DEFAULT_MAX_LENGTH = 200
+
+export type Osc9NotificationOptions = {
+  fallback?: string
+  maxLength?: number
+  prefix?: string
+}
+
+function normalizeNotificationText(input: string, maxLength: number) {
+  const sanitized = input.replace(/[\x07\x1b\x9c]/g, "")
+  const collapsed = sanitized.replace(/\s+/g, " ").trim()
+  if (!collapsed) return ""
+
+  const limit = Math.max(1, maxLength)
+  if (collapsed.length <= limit) return collapsed
+  if (limit <= 3) return collapsed.slice(0, limit)
+  return collapsed.slice(0, limit - 3) + "..."
+}
+
+function wrapForTmux(sequence: string) {
+  if (!process.env["TMUX"]) return sequence
+  return `\x1bPtmux;\x1b${sequence}\x1b\\`
+}
+
+export function buildOsc9Notification(input: string, options?: Osc9NotificationOptions) {
+  const maxLength = options?.maxLength ?? OSC9_DEFAULT_MAX_LENGTH
+  let message = normalizeNotificationText(input, maxLength)
+  if (!message && options?.fallback) {
+    message = normalizeNotificationText(options.fallback, maxLength)
+  }
+  if (!message) return undefined
+  if (options?.prefix) {
+    message = `${options.prefix} ${message}`
+  }
+  return wrapForTmux(`\x1b]9;${message}\x07`)
+}