feat(tui): copy last assistant message formatted

packages/tui/src/routes/session/index.tsx

@@ -55,6 +55,7 @@ import { DialogSessionRename } from "../../component/dialog-session-rename"
 import { Sidebar } from "./sidebar"
 import { SubagentFooter } from "./subagent-footer.tsx"
 import { filetype } from "../../util/filetype"
+import { formatAnswer } from "../../util/format"
 import parsers from "../../parsers-config"
 import { errorMessage } from "../../util/error"
 import { Toast, useToast } from "../../ui/toast"
@@ -913,6 +914,57 @@ export function Session() {
         dialog.clear()
       },
     },
+    {
+      title: "Copy last assistant message formatted",
+      value: "messages.copy.formatted",
+      category: "Session",
+      run: () => {
+        const lastAssistantMessage = messagesBeforeRevert().findLast((message) => message.role === "assistant")
+        if (!lastAssistantMessage) {
+          toast.show({ message: "No assistant messages found", variant: "error" })
+          dialog.clear()
+          return
+        }
+        if (
+          lastAssistantMessage.error ||
+          !lastAssistantMessage.finish ||
+          ["tool-calls", "unknown"].includes(lastAssistantMessage.finish)
+        ) {
+          toast.show({ message: "Last assistant message is not complete", variant: "error" })
+          dialog.clear()
+          return
+        }
+
+        const parts = sync.data.part[lastAssistantMessage.id] ?? []
+        const textParts = parts.filter((part) => part.type === "text")
+        if (textParts.length === 0) {
+          toast.show({ message: "No text parts found in last assistant message", variant: "error" })
+          dialog.clear()
+          return
+        }
+
+        const text = formatAnswer(
+          textParts
+            .map((part) => part.text)
+            .join("\n")
+            .trim(),
+        )
+        if (!text) {
+          toast.show({
+            message: "No text content found in last assistant message",
+            variant: "error",
+          })
+          dialog.clear()
+          return
+        }
+
+        clipboard
+          .write?.(text)
+          .then(() => toast.show({ message: "Formatted message copied to clipboard!", variant: "success" }))
+          .catch(() => toast.show({ message: "Failed to copy to clipboard", variant: "error" }))
+        dialog.clear()
+      },
+    },
     {
       title: "Copy session transcript",
       value: "session.copy",

packages/tui/src/util/format.ts

@@ -1,3 +1,41 @@
+export function formatAnswer(text: string) {
+  const lines = text.replace(/\r\n?/g, "\n").split("\n")
+  const out: string[] = []
+  let fenceChar = ""
+  let fenceLen = 0
+  let blanks = 0
+  for (const line of lines) {
+    const fence = line.match(/^\s*(`{3,}|~{3,})/)
+    if (fence) {
+      const mark = fence[1] ?? ""
+      const char = mark[0] ?? ""
+      if (!fenceChar) {
+        fenceChar = char
+        fenceLen = mark.length
+      } else if (char === fenceChar && mark.length >= fenceLen) {
+        fenceChar = ""
+        fenceLen = 0
+      }
+      blanks = 0
+      out.push(line)
+      continue
+    }
+    if (fenceChar) {
+      out.push(line)
+      continue
+    }
+    if (line.trim() === "") {
+      blanks += 1
+      if (blanks <= 1 && out.length > 0) out.push("")
+      continue
+    }
+    blanks = 0
+    out.push(line.replace(/[ \t]+$/, ""))
+  }
+  while (out.length > 0 && out[out.length - 1] === "") out.pop()
+  return out.join("\n")
+}
+
 export function formatDuration(secs: number) {
   if (secs <= 0) return ""
   if (secs < 60) return `${secs}s`

packages/tui/test/util/format.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, test } from "bun:test"
-import { formatDuration } from "../../src/util/format"
+import { formatAnswer, formatDuration } from "../../src/util/format"
 
 describe("util.format", () => {
   describe("formatDuration", () => {
@@ -56,4 +56,28 @@ describe("util.format", () => {
       expect(formatDuration(604800)).toBe("~1 week")
     })
   })
+
+  describe("formatAnswer", () => {
+    test("keeps prose text unchanged", () => {
+      expect(formatAnswer("hello world")).toBe("hello world")
+      expect(formatAnswer("")).toBe("")
+    })
+
+    test("trims trailing whitespace outside code blocks", () => {
+      expect(formatAnswer("hello   \nworld\t ")).toBe("hello\nworld")
+    })
+
+    test("collapses repeated blank lines and trims ends", () => {
+      expect(formatAnswer("\n\na\n\n\n\nb\n\n")).toBe("a\n\nb")
+    })
+
+    test("preserves fenced code blocks byte-for-byte", () => {
+      const code = "```js\nline one   \n\n\nline two\t\n```"
+      expect(formatAnswer(`before   \n\n${code}\n\nafter   `)).toBe(`before\n\n${code}\n\nafter`)
+    })
+
+    test("treats unclosed fences as code to the end", () => {
+      expect(formatAnswer("text   \n```\nkeep   \n\n\nkeep")).toBe("text\n```\nkeep   \n\n\nkeep")
+    })
+  })
 })