style(tui): simplify the composer surface

tui/src/app.test.ts

@@ -766,7 +766,13 @@ describe("NanobotTui layout", () => {
     const internals = app as unknown as {
       palette: { referenceBackground: string; text: string; border: string }
       shell: { backgroundColor: { intent: string } }
-      composer: { backgroundColor: { intent: string }; textColor: { toInts(): number[] } }
+      composerFrame: {
+        backgroundColor: { intent: string; toInts(): number[] }
+      }
+      composer: {
+        backgroundColor: { intent: string; toInts(): number[] }
+        textColor: { toInts(): number[] }
+      }
       transcript: {
         markdown: Set<{ syntaxStyle: object }>
         frames: Set<{ borderColor: { toInts(): number[] } }>
@@ -791,13 +797,44 @@ describe("NanobotTui layout", () => {
       border: "#D4D4D8",
     })
     expect(internals.shell.backgroundColor.intent).toBe("default")
-    expect(internals.composer.backgroundColor.intent).toBe("default")
+    expect(internals.composerFrame.backgroundColor.toInts().slice(0, 3)).toEqual([240, 240, 240])
+    expect(internals.composer.backgroundColor.toInts().slice(0, 3)).toEqual([240, 240, 240])
     expect(internals.composer.textColor.toInts().slice(0, 3)).toEqual([24, 24, 27])
     expect(sessionFrame?.borderColor.toInts().slice(0, 3)).toEqual([212, 212, 216])
     expect(userRow?.backgroundColor.toInts().slice(0, 3)).toEqual([240, 240, 240])
     expect(markdown?.syntaxStyle).not.toBe(darkSyntax)
   })
 
+  test("uses a quiet surface instead of a boxed composer", async () => {
+    setup = await createRenderer({ width: 72, height: 20, screenMode: "alternate-screen" })
+    const app = NanobotTui.mount(
+      setup.renderer,
+      { ...options, theme: "light" },
+      client(),
+      new MockTreeSitterClient({ autoResolveTimeout: 0 }),
+    )
+    const internals = app as unknown as {
+      ready: boolean
+      composerFrame: {
+        border: boolean | string[]
+        backgroundColor: { toInts(): number[] }
+      }
+      composer: { backgroundColor: { toInts(): number[] } }
+    }
+
+    expect(internals.composerFrame.border).toBeFalse()
+    expect(internals.composerFrame.backgroundColor.toInts().slice(0, 3)).toEqual([240, 240, 240])
+    expect(internals.composer.backgroundColor.toInts().slice(0, 3)).toEqual([240, 240, 240])
+
+    app.accept({ event: "attached", chat_id: "chat" })
+    await waitUntil(() => internals.ready)
+    await setup.renderOnce()
+
+    const composerLine = setup.captureCharFrame().split("\n")
+      .find((line) => line.includes("Ask nanobot anything")) || ""
+    expect(composerLine).not.toContain("│")
+  })
+
   test("uses asymmetric roles instead of chat bubbles", async () => {
     setup = await createRenderer({ width: 72, height: 24, screenMode: "alternate-screen" })
     const app = NanobotTui.mount(

tui/src/app.ts

@@ -411,17 +411,16 @@ export class NanobotTui {
     })
     this.title.add(this.titleText)
     this.title.add(this.modelText)
+    const composerSurface = this.composerSurface()
     this.composerFrame = new BoxRenderable(renderer, {
       id: "nanobot-tui-composer-frame",
       width: "100%",
-      minHeight: 3,
+      minHeight: 1,
       flexShrink: 0,
-      border: true,
-      borderStyle: "rounded",
-      borderColor: this.palette.border,
+      border: false,
       paddingLeft: 1,
       paddingRight: 1,
-      backgroundColor: RGBA.defaultBackground(),
+      backgroundColor: composerSurface,
     })
     this.composer = new TextareaRenderable(renderer, {
       id: "nanobot-tui-composer",
@@ -433,8 +432,8 @@ export class NanobotTui {
       placeholderColor: this.palette.faint,
       textColor: this.palette.text,
       focusedTextColor: this.palette.text,
-      backgroundColor: RGBA.defaultBackground(),
-      focusedBackgroundColor: RGBA.defaultBackground(),
+      backgroundColor: composerSurface,
+      focusedBackgroundColor: composerSurface,
       cursorColor: this.palette.accent,
       showCursor: true,
       keyBindings: [
@@ -1040,7 +1039,7 @@ export class NanobotTui {
     this.sessionMenu.setTheme(commandMenuTheme(this.palette))
     this.contextPanel.setTheme(contextPanelTheme(this.palette))
     this.diffViewer.setTheme(diffViewerTheme(this.palette, this.backgroundKnown))
-    this.composerFrame.borderColor = this.palette.border
+    this.updateComposerAppearance()
     this.composer.textColor = this.palette.text
     this.composer.focusedTextColor = this.palette.text
     this.composer.cursorColor = this.palette.accent
@@ -1113,7 +1112,20 @@ export class NanobotTui {
   private resizeComposer(): void {
     const maxHeight = Math.max(1, Math.min(12, Math.floor(this.renderer.height / 3)))
     this.composer.maxHeight = maxHeight
-    this.composerFrame.maxHeight = maxHeight + 2
+    this.composerFrame.maxHeight = maxHeight
+  }
+
+  private composerSurface(): RGBA {
+    return this.backgroundKnown
+      ? RGBA.fromHex(this.palette.userBackground)
+      : RGBA.defaultBackground()
+  }
+
+  private updateComposerAppearance(): void {
+    const surface = this.composerSurface()
+    this.composerFrame.backgroundColor = surface
+    this.composer.backgroundColor = surface
+    this.composer.focusedBackgroundColor = surface
   }
 
   private syncComposerPlaceholder(): void {