feat(opentui-v2): Phase 2a — scrollbox transcript + textarea composer + header

Turns the read-only Phase-1 view into an interactive shell, split into focused
view components (spec v4 §2 layout):

- view/transcript.tsx: ONE full-height <scrollbox> with a reactive <For>
  (opencode's no-scrollback model). Applies the §8 #2 gotchas exactly:
  minHeight:0 on the wrapper AND the scrollbox, NO flexDirection on the
  scrollbox root, stickyScroll + stickyStart="bottom".
- view/composer.tsx: a native <textarea> captured by ref — flexShrink:0,
  focus-on-mount, Enter->submit via keyBindings, imperative .clear() on submit,
  and a `submitting` re-entrancy guard. Wired by the entry to fire prompt.submit
  (Effect.runFork on the in-hand service value); it's now the PRIMARY input, with
  the HERMES_TUI_PROMPT stand-in kept only for launch-with-prompt.
- view/header.tsx + view/messageLine.tsx: extracted, themed (no hardcoded
  styles). MessageLine stays flat-text this slice; ordered parts (§7) land in 2b.

test/lib/render.ts now flushes 3 renderOnce passes before capture — a <scrollbox>
needs more than one pass to measure content + apply sticky, else the transcript
row paints blank.

Verified: bun run check green (12 tests / 4 files / 31 expects). Live tmux drive:
typed into the composer -> cleared -> user row -> streamed reply ("Here are three
words"); Ctrl+C quits cleanly even with the textarea focused, no orphan child.
Composer placeholder rendered the live skin's welcome string (skin->theme live).
Smoke P2a + parity matrix updated. Phase 2b (ordered parts/tool render/markdown)
is the next slice.

ui-tui-opentui-v2/src/entry/main.tsx

@@ -92,6 +92,25 @@ export const run = Effect.fn('Tui.run')(function* (input: TuiInput) {
       const gateway = yield* GatewayService
       yield* gateway.subscribe(event => store.apply(event))
 
+      // Composer submit: a plain callback the Solid view calls. The service value
+      // is already in hand, so `gateway.request(...)` is Effect<…, never> — fire it
+      // detached with runFork; failures are logged, never thrown into the view.
+      const submit = (text: string) => {
+        store.pushUser(text)
+        const sid = gateway.sessionId()
+        if (!sid) {
+          getLog().warn('submit', 'no session yet — dropping prompt', { text })
+          return
+        }
+        Effect.runFork(
+          gateway
+            .request('prompt.submit', { session_id: sid, text })
+            .pipe(
+              Effect.catchCause(cause => Effect.sync(() => getLog().warn('submit', 'failed', { cause: String(cause) })))
+            )
+        )
+      }
+
       // Live backend: drive a session (create + optional initial prompt) concurrently.
       if (!input.fake) yield* Effect.forkScoped(bootstrapSession(gateway, store, input))
 
@@ -101,7 +120,7 @@ export const run = Effect.fn('Tui.run')(function* (input: TuiInput) {
         render(
           () => (
             <ThemeProvider theme={() => store.state.theme}>
-              <App store={store} />
+              <App store={store} onSubmit={submit} />
             </ThemeProvider>
           ),
           renderer

ui-tui-opentui-v2/src/test/render.test.tsx

@@ -29,12 +29,13 @@ describe('App render (Phase 1, themed)', () => {
           <App store={store} />
         </ThemeProvider>
       ),
-      { width: 60, height: 8 }
+      { width: 60, height: 16 }
     )
 
     expect(frame).toContain('Hermes Agent') // default brand.name
     expect(frame).toContain('ready')
     expect(frame).toContain('Hi there, glitch!')
+    expect(frame).toContain('Type your message') // composer placeholder (brand.welcome)
   })
 
   test('applying a skin re-themes the brand name (skinnable, no hardcoding)', async () => {
@@ -48,7 +49,7 @@ describe('App render (Phase 1, themed)', () => {
           <App store={store} />
         </ThemeProvider>
       ),
-      { width: 60, height: 8 }
+      { width: 60, height: 16 }
     )
 
     expect(frame).toContain('Zephyr')

ui-tui-opentui-v2/src/view/App.tsx

@@ -1,49 +1,33 @@
 /**
- * App — the Solid view shell (spec v4 §2 `view/App.tsx`). Phase 1: header +
- * transcript, fully themed via `useTheme()` — NO hardcoded styles (spec §7.5).
- * The streamed message + skin both come from the store; the boundary feeds them.
+ * App — the Solid view shell (spec v4 §2 `view/App.tsx`). Phase 2: header +
+ * scrolling transcript + composer, composed in a flex column. Fully themed via
+ * the ThemeProvider — NO hardcoded styles (§7.5).
  *
- * Rich text uses <b>/<span> children, never an attributes bitmask (gotcha §8 #1).
- * Inline color goes in `style={{ fg }}` on <span>; <text> accepts `fg` directly.
+ *   header     flexShrink:0            (top chrome line)
+ *   transcript flexGrow:1, minHeight:0 (the one <scrollbox>; §8 #2 gotchas)
+ *   composer   flexShrink:0            (the <textarea>; clears on submit, §8 #3)
+ *
+ * `onSubmit` is wired by the entry (Effect boundary) to fire `prompt.submit`;
+ * it's optional so headless frame tests can mount the shell without a gateway.
  */
-import { For, Show } from 'solid-js'
-
 import type { SessionStore } from '../logic/store.ts'
-import { useTheme } from './theme.tsx'
+import { Composer } from './composer.tsx'
+import { Header } from './header.tsx'
+import { Transcript } from './transcript.tsx'
 
 export interface AppProps {
   readonly store: SessionStore
+  readonly onSubmit?: (text: string) => void
 }
 
-export function App(props: AppProps) {
-  const theme = useTheme()
+const NOOP = () => {}
 
+export function App(props: AppProps) {
   return (
     <box style={{ flexDirection: 'column', flexGrow: 1, padding: 1 }}>
-      <box style={{ flexShrink: 0 }}>
-        <text>
-          <b>{theme().brand.name}</b>
-          <span style={{ fg: theme().color.muted }}> · opentui · </span>
-          <Show when={props.store.state.ready} fallback={<span style={{ fg: theme().color.muted }}>connecting…</span>}>
-            <span style={{ fg: theme().color.ok }}>ready</span>
-          </Show>
-        </text>
-      </box>
-      <box style={{ flexDirection: 'column', flexGrow: 1, minHeight: 0, marginTop: 1 }}>
-        <For each={props.store.state.messages}>
-          {message => (
-            <text>
-              <span style={{ fg: message.role === 'assistant' ? theme().color.accent : theme().color.prompt }}>
-                {message.role === 'assistant' ? `${theme().brand.icon} ` : `${theme().brand.prompt} `}
-              </span>
-              <span style={{ fg: theme().color.text }}>{message.text}</span>
-              <Show when={message.streaming}>
-                <span style={{ fg: theme().color.muted }}>▍</span>
-              </Show>
-            </text>
-          )}
-        </For>
-      </box>
+      <Header store={props.store} />
+      <Transcript store={props.store} />
+      <Composer onSubmit={props.onSubmit ?? NOOP} />
     </box>
   )
 }

ui-tui-opentui-v2/src/view/composer.tsx

@@ -0,0 +1,50 @@
+/**
+ * Composer — the input row (spec v4 §2 `view/composer.tsx`). Phase 2: a native
+ * <textarea> captured by ref; Enter submits, the input clears imperatively.
+ *
+ * Gotchas (§8 #3): `flexShrink:0` on the wrapper so it never collapses onto its
+ * rule under a full transcript; clear via the renderable's `.clear()` (NOT a
+ * `key`-remount or controlled `value=""`); a `submitting` re-entrancy guard so a
+ * double-Enter can't read the now-empty buffer and submit a phantom prompt.
+ *
+ * `onSubmit` is a plain callback wired by the entry (Effect boundary) — it fires
+ * the `prompt.submit` RPC. The composer itself stays pure Solid (no Effect).
+ */
+import { type TextareaRenderable } from '@opentui/core'
+import { onMount } from 'solid-js'
+
+import { useTheme } from './theme.tsx'
+
+export function Composer(props: { onSubmit: (text: string) => void }) {
+  const theme = useTheme()
+  let ta: TextareaRenderable | undefined
+  let submitting = false
+
+  const submit = () => {
+    if (submitting || !ta) return
+    const text = ta.plainText.trim()
+    if (!text) return
+    submitting = true
+    props.onSubmit(text)
+    ta.clear()
+    submitting = false
+  }
+
+  onMount(() => ta?.focus())
+
+  return (
+    <box style={{ flexShrink: 0, marginTop: 1 }}>
+      <textarea
+        ref={el => (ta = el)}
+        style={{ height: 3, width: '100%' }}
+        placeholder={theme().brand.welcome}
+        placeholderColor={theme().color.muted}
+        textColor={theme().color.text}
+        cursorColor={theme().color.accent}
+        focusedBackgroundColor={theme().color.statusBg}
+        keyBindings={[{ action: 'submit', name: 'return' }]}
+        onSubmit={submit}
+      />
+    </box>
+  )
+}

ui-tui-opentui-v2/src/view/header.tsx

@@ -0,0 +1,25 @@
+/**
+ * Header — the top chrome line (spec v4 §2 `view/header.tsx`). Phase 2 skeleton:
+ * brand · engine · ready/connecting, fully themed (`useTheme()`, NO hardcoded
+ * styles — §7.5). Model / cwd / context% / cost land in Phase 5b once
+ * `session.info` + `Usage` are wired.
+ */
+import { Show } from 'solid-js'
+
+import type { SessionStore } from '../logic/store.ts'
+import { useTheme } from './theme.tsx'
+
+export function Header(props: { store: SessionStore }) {
+  const theme = useTheme()
+  return (
+    <box style={{ flexShrink: 0 }}>
+      <text>
+        <b>{theme().brand.name}</b>
+        <span style={{ fg: theme().color.muted }}> · opentui · </span>
+        <Show when={props.store.state.ready} fallback={<span style={{ fg: theme().color.muted }}>connecting…</span>}>
+          <span style={{ fg: theme().color.ok }}>ready</span>
+        </Show>
+      </text>
+    </box>
+  )
+}

ui-tui-opentui-v2/src/view/messageLine.tsx

@@ -0,0 +1,34 @@
+/**
+ * MessageLine — renders one transcript row (spec v4 §2 `view/messageLine.tsx`).
+ * Phase 2 slice: flat text messages with a role gutter + streaming `▍` cursor,
+ * fully themed. The ordered-parts dispatch (text/tool/reasoning §7) replaces the
+ * flat `text` field in the next slice — this file grows into that `<Switch>` loop.
+ *
+ * Rich text via <b>/<span> children, never an attributes bitmask (gotcha §8 #1);
+ * inline color is `<span style={{ fg }}>`.
+ */
+import { Show } from 'solid-js'
+
+import type { Message } from '../logic/store.ts'
+import { useTheme } from './theme.tsx'
+
+export function MessageLine(props: { message: Message }) {
+  const theme = useTheme()
+  const gutter = () =>
+    props.message.role === 'assistant'
+      ? `${theme().brand.icon} `
+      : props.message.role === 'user'
+        ? `${theme().brand.prompt} `
+        : ''
+  const gutterFg = () => (props.message.role === 'assistant' ? theme().color.accent : theme().color.prompt)
+
+  return (
+    <text style={{ flexShrink: 0 }}>
+      <span style={{ fg: gutterFg() }}>{gutter()}</span>
+      <span style={{ fg: theme().color.text }}>{props.message.text}</span>
+      <Show when={props.message.streaming}>
+        <span style={{ fg: theme().color.muted }}>▍</span>
+      </Show>
+    </text>
+  )
+}

ui-tui-opentui-v2/src/view/transcript.tsx

@@ -0,0 +1,27 @@
+/**
+ * Transcript — the scrolling message pane (spec v4 §2 `view/transcript.tsx`).
+ *
+ * ONE full-height <scrollbox> with a reactive <For> (opencode's model — the
+ * viewport clips growing output so terminal scrollback is never corrupted; no
+ * `writeToScrollback`). Carries the §8 #2 gotchas EXACTLY:
+ *   - `minHeight:0` on BOTH the wrapper box AND the <scrollbox> (so the flex
+ *     child can shrink below content height instead of pushing the composer off),
+ *   - NO `flexDirection` on the <scrollbox> ROOT style (it has internal
+ *     viewport/content children; setting it there breaks content-height
+ *     measurement → phantom scroll offset that clips the top + leaves a gap),
+ *   - `stickyScroll` + `stickyStart="bottom"` to pin the latest line.
+ */
+import { For } from 'solid-js'
+
+import type { SessionStore } from '../logic/store.ts'
+import { MessageLine } from './messageLine.tsx'
+
+export function Transcript(props: { store: SessionStore }) {
+  return (
+    <box style={{ flexGrow: 1, minHeight: 0, marginTop: 1 }}>
+      <scrollbox style={{ flexGrow: 1, minHeight: 0 }} stickyScroll stickyStart="bottom">
+        <For each={props.store.state.messages}>{message => <MessageLine message={message} />}</For>
+      </scrollbox>
+    </box>
+  )
+}