fix(ui): drop both status rows together, and teach the setup agent Windows

- The built-in session bar now respects the same fullscreen height limit as
  the custom statusLine row, so it stops keeping the flexShrink:0 row the
  footer just gave back to the ScrollBox; the threshold moves next to the
  resolver in statusLineDisplay.ts so the two rows cannot drift apart again
- The statusline-setup agent no longer hunts for ~/.zshrc and PS1 on Windows,
  where neither exists, and is told the command always runs through bash
  (Git Bash on Windows) and that jq is usually absent while node is not

Author: AbdoKnbGit

src/components/PromptInput/PromptInputFooter.tsx

@@ -20,6 +20,7 @@ import { isFullscreenEnvEnabled } from '../../utils/fullscreen.js';
 import { isUndercover } from '../../utils/undercover.js';
 import { CoordinatorTaskPanel, useCoordinatorTaskCount } from '../CoordinatorAgentStatus.js';
 import { getLastAssistantMessageId, StatusLine, statusLineShouldDisplay } from '../StatusLine.js';
+import { statusRowFits } from '../statusLineDisplay.js';
 import { Notifications } from './Notifications.js';
 import { PromptInputFooterLeftSide } from './PromptInputFooterLeftSide.js';
 import { PromptInputFooterSuggestions, type SuggestionItem } from './PromptInputFooterSuggestions.js';
@@ -104,11 +105,11 @@ function PromptInputFooter({
   messagesRef.current = messages;
   const lastAssistantMessageId = useMemo(() => getLastAssistantMessageId(messages), [messages]);
   const isNarrow = columns < 80;
-  // In fullscreen the bottom slot is flexShrink:0, so every row here is a row
-  // stolen from the ScrollBox. Drop the optional StatusLine first. Non-fullscreen
-  // has terminal scrollback to absorb overflow, so we never hide StatusLine there.
+  // Below a certain height fullscreen cannot spare a row for either status
+  // row — see statusRowFits in statusLineDisplay.ts for why, and so that this
+  // row and the built-in session bar always drop together.
   const isFullscreen = isFullscreenEnvEnabled();
-  const isShort = isFullscreen && rows < 24;
+  const isShort = !statusRowFits(isFullscreen, rows);
 
   // Pill highlights when tasks is the active footer item AND no specific
   // agent row is selected. When coordinatorTaskIndex >= 0 the pointer has

src/components/PromptInput/PromptInputStatusBar.tsx

@@ -2,6 +2,9 @@ import * as React from 'react'
 import { Box, Text } from 'src/ink.js'
 import { getSdkBetas } from '../../bootstrap/state.js'
 import { useSettings } from '../../hooks/useSettings.js'
+import { useTerminalSize } from '../../hooks/useTerminalSize.js'
+import { isFullscreenEnvEnabled } from '../../utils/fullscreen.js'
+import { statusRowFits } from '../statusLineDisplay.js'
 import { sessionStatusBarShouldDisplay } from '../StatusLine.js'
 import { useMainLoopModel } from '../../hooks/useMainLoopModel.js'
 import { analyzeContext } from '../../utils/contextAnalysis.js'
@@ -30,7 +33,10 @@ export function PromptInputStatusBar({
   // Hidden when the user runs a custom statusLine command instead, or turns
   // the bar off with sessionStatusBar: false. See statusLineDisplay.ts.
   const settings = useSettings()
-  const visible = sessionStatusBarShouldDisplay(settings)
+  const { rows } = useTerminalSize()
+  const visible =
+    sessionStatusBarShouldDisplay(settings) &&
+    statusRowFits(isFullscreenEnvEnabled(), rows)
   const mainLoopModel = useMainLoopModel()
   const provider = getAPIProvider()
   const contextWindow = getContextWindowForModel(mainLoopModel, getSdkBetas())

src/components/statusLineDisplay.test.ts

@@ -5,8 +5,10 @@
  */
 
 import {
+  MIN_FULLSCREEN_ROWS_FOR_STATUS,
   resolveStatusLineDisplay,
   type StatusLineDisplayInput,
+  statusRowFits,
 } from './statusLineDisplay.js'
 
 let passed = 0
@@ -125,6 +127,29 @@ test('assistant mode hides both rows whatever is configured', () => {
   }
 })
 
+test('a short fullscreen terminal has no room for a status row', () => {
+  assert(
+    !statusRowFits(true, MIN_FULLSCREEN_ROWS_FOR_STATUS - 1),
+    'one row below the threshold should not fit',
+  )
+  assert(
+    statusRowFits(true, MIN_FULLSCREEN_ROWS_FOR_STATUS),
+    'the threshold itself should fit',
+  )
+  assert(statusRowFits(true, 80), 'a tall fullscreen terminal should fit')
+})
+
+test('outside fullscreen a status row always fits', () => {
+  // Non-fullscreen has terminal scrollback to absorb overflow, so height
+  // never hides a row there - however short the terminal gets.
+  for (const rows of [0, 1, 5, 23, 200]) {
+    assert(
+      statusRowFits(false, rows),
+      'rows=' + rows + ' should still fit outside fullscreen',
+    )
+  }
+})
+
 test('the two rows never both vanish unless asked', () => {
   // Guards the regression the gate could introduce: a user who configured a
   // custom line must never end up with no status row by accident.

src/components/statusLineDisplay.ts

@@ -13,6 +13,25 @@
  * mode, workspace trust, hook policy) is resolved by the callers.
  */
 
+/**
+ * Terminal height below which fullscreen cannot spare a status row.
+ * Matches the historical threshold in PromptInputFooter.
+ */
+export const MIN_FULLSCREEN_ROWS_FOR_STATUS = 24
+
+/**
+ * Does the terminal have room for a status row?
+ *
+ * Fullscreen pins the prompt into a flexShrink:0 bottom slot (BottomSlot in
+ * FullscreenLayout.tsx), so under that height every optional row is one taken
+ * from the ScrollBox. Both rows answer to this, so they drop together instead
+ * of one quietly keeping the row the other just gave up. Outside fullscreen
+ * the terminal has scrollback to absorb overflow and nothing is hidden.
+ */
+export function statusRowFits(isFullscreen: boolean, rows: number): boolean {
+  return !isFullscreen || rows >= MIN_FULLSCREEN_ROWS_FOR_STATUS
+}
+
 export type StatusLineDisplayInput = {
   /**
    * A `statusLine` command is present in the settings that apply to this

src/tools/AgentTool/built-in/statuslineSetup.ts

@@ -2,6 +2,18 @@ import type { BuiltInAgentDefinition } from '../loadAgentsDir.js'
 
 const STATUSLINE_SYSTEM_PROMPT = `You are a status line setup agent for Tau. Your job is to create or update the statusLine command in the user's Tau settings.
 
+Before anything else, know two things about the environment:
+
+- The command you write is always run through bash. Hooks default to
+  DEFAULT_HOOK_SHELL = 'bash' and statusLine has no "shell" field to override
+  it, so on Windows it runs in Git Bash. Write bash, never PowerShell or cmd.
+- Do not assume jq is installed. It usually is not on Windows. node is always
+  available, so prefer it for reading the JSON input.
+
+On Windows there is no PS1 - PowerShell uses a prompt function and none of the
+files in step 1 exist. Do not read them. Say so and ask the user how they want
+the row formatted, or work from the description they already gave you.
+
 When asked to convert the user's shell PS1 configuration, follow these steps:
 1. Read the user's shell configuration files in this order of preference:
    - ~/.zshrc