fix(tui): preserve streamed code on completion

tui/src/app.test.ts

@@ -9,6 +9,7 @@ import {
 } from "@opentui/core"
 import {
   MockTreeSitterClient,
+  TestRecorder,
   createTestRenderer,
   type TestRendererSetup,
 } from "@opentui/core/testing"
@@ -491,6 +492,17 @@ describe("NanobotTui layout", () => {
     expect(ui.composer.plainText).toContain("replacement")
     expect(ui.composer.plainText).not.toContain("Image #1")
 
+    ui.composer.setText("")
+    setup.mockInput.pressKey("v", { ctrl: true })
+    await waitUntil(() => ui.composer.plainText === "[Image #1] ")
+    ui.composer.cursorOffset = 10
+    setup.mockInput.pressArrow("left", { shift: true })
+    await waitUntil(() => ui.composer.cursorOffset === 0)
+    await setup.mockInput.typeText("replacement")
+    await waitUntil(() => ui.draft.imageCount === 0)
+    expect(ui.composer.plainText).toContain("replacement")
+    expect(ui.composer.plainText).not.toContain("Image #1")
+
     ui.composer.setText("")
     setup.mockInput.pressKey("v", { ctrl: true })
     await waitUntil(() => ui.composer.plainText === "[Image #1] ")
@@ -2052,6 +2064,44 @@ describe("NanobotTui layout", () => {
     }
   })
 
+  test("keeps streamed fenced code visible while completing the response", async () => {
+    setup = await createRenderer({ width: 100, height: 30, screenMode: "alternate-screen" })
+    const app = mount(setup)
+    const response = [
+      "Commit types:",
+      "",
+      "```text",
+      "feat:",
+      "fix:",
+      "perf:",
+      "docs:",
+      "test:",
+      "refactor:",
+      "chore:",
+      "```",
+      "",
+      "Include the reason in the body.",
+    ].join("\n")
+
+    app.accept({ event: "attached", chat_id: "chat" })
+    app.accept({ event: "delta", chat_id: "chat", text: response })
+    await setup.flush()
+    expect(setup.captureCharFrame()).toContain("feat:")
+
+    const recorder = new TestRecorder(setup.renderer)
+    recorder.rec()
+    app.accept({ event: "stream_end", chat_id: "chat" })
+    app.accept({ event: "turn_end", chat_id: "chat" })
+    await setup.flush()
+    recorder.stop()
+
+    expect(recorder.recordedFrames.length).toBeGreaterThan(0)
+    expect(recorder.recordedFrames.every(({ frame }) => frame.includes("feat:"))).toBeTrue()
+    expect(recorder.recordedFrames.every(({ frame }) => (
+      frame.includes("Include the reason in the body.")
+    ))).toBeTrue()
+  })
+
   test("renders assistant LaTeX as Unicode text without changing code", async () => {
     setup = await createRenderer({ width: 96, height: 24, screenMode: "alternate-screen" })
     const app = mount(setup)

tui/src/app.ts

@@ -1738,16 +1738,30 @@ export class NanobotTui {
       key.preventDefault()
       return
     }
-    if (!key.ctrl && !key.meta && !key.shift && (key.name === "left" || key.name === "right")) {
+    if (!key.ctrl && !key.meta && (key.name === "left" || key.name === "right")) {
       const direction = key.name === "left" ? -1 : 1
+      const cursor = this.composerStringCursor()
       const target = this.draft.moveImageCursor(
         this.composer.plainText,
-        this.composerStringCursor(),
+        cursor,
         direction,
       )
       if (target !== null) {
         this.composerCursor = target
-        this.setComposerStringCursor(this.composer.plainText, target)
+        if (key.shift) {
+          const cursorOffset = this.composerOffsetForStringIndex(this.composer.plainText, cursor)
+          const targetOffset = this.composerOffsetForStringIndex(this.composer.plainText, target)
+          this.composer.setSelection(
+            Math.min(cursorOffset, targetOffset),
+            Math.max(cursorOffset, targetOffset),
+          )
+          // OpenTUI 0.5.10 clears the selection through the public cursor
+          // setter. Move the native edit cursor directly so the placeholder
+          // remains one selected, replaceable unit.
+          this.composer.editBuffer.setCursorByOffset(targetOffset)
+        } else {
+          this.setComposerStringCursor(this.composer.plainText, target)
+        }
         key.preventDefault()
         return
       }