command.js: autocomplete by candidate window

CLAUDE.md

@@ -436,3 +436,112 @@ The different weights for Mid and Side channels reflect the perceptual importanc
 - DC frequency underamplification (using 1.0 instead of 4.0/6.0)
 - Incorrect stereo imaging and extreme side channel distortion
 - Severe frequency response errors that manifest as "clipping-like" distortion
+
+## Virtual Consoles (vtmgr)
+
+Linux-style virtual consoles for TVDOS: up to 6 independent shell sessions,
+switched with **Alt-1..Alt-6** or the **`chvt N`** builtin, **Alt-0** to exit.
+Implemented entirely in JS — **no tsvm_core changes**.
+
+### Architecture
+
+- **Dispatcher**: `assets/disk0/tvdos/sbin/vtmgr.js`. Launched directly by the
+  `TVDOS.SYS` boot block (only when `!_TVDOS_IS_VT_PANE`); when it exits (Alt-0)
+  the boot block runs `AUTOEXEC.BAT` as the bare fallback shell. Owns the
+  physical keyboard and screen. Each VT runs in its own GraalVM context/thread
+  via the existing `parallel.spawnNewContext` / `attachProgram` / `launch` API
+  (see `VMJSR223Delegate.kt` `class Parallel`). VT 1 spawns at boot; VT 2-6 are
+  lazy-spawned on first switch and re-spawned if their shell exits.
+- **Concurrency model**: truly concurrent — switching works mid-command, not
+  just at the prompt. Background panes keep running (no `Thread.suspend`; it is
+  unusable on JDK 21). A cooperative gate inside the shimmed `con.getch` parks
+  panes blocked on input; CPU-bound background panes are allowed to run.
+- **Shared memory**: one `sys.malloc` region holds a control block (active VT,
+  switch request, debounce, spawned-bits) plus, per VT, an input ring buffer and
+  a 7682-byte text-plane buffer mirroring the GPU text-area layout
+  (cursor 2 + fore 2560 + back 2560 + char 2560).
+- **Compositor** (30 Hz): blits the active VT's text plane to the physical GPU
+  text area via `sys.memcpy`, and pushes that VT's cursor-visibility into the GPU
+  blink bit (MMIO attribute byte 6, addressed at `-1 - (131072*gpuSlot + 6)`).
+- **Boot config split (`commandrc` + `AUTOEXEC.BAT`)**: environment setup and
+  app-launch are split into two files so panes can replay one without the other.
+  `\commandrc` holds the `set` commands (PATH/INCLPATH/HELPPATH/KEYBOARD) and is
+  run by the `TVDOS.SYS` boot block in **every** context (boot and pane) — it has
+  no `.BAT` extension, so the boot block runs it line-by-line (`set` mutates the
+  shared `_TVDOS.variables`, so the effect persists). `\AUTOEXEC.BAT` is the
+  **per-console launch** script (Korean IME `tvdos/i18n/korean`, then
+  `command -fancy`); it is run once per console — by each pane's bootstrap, and
+  by the boot block as the post-vtmgr fallback. No env snapshot/replay anymore;
+  each pane gets PATH/KEYBOARD/etc. natively from `commandrc`, and Korean IME
+  (a per-context `unicode.uniprint` handler) now registers in every pane.
+- **Per-pane bootstrap**: each pane re-evals `TVDOS.SYS` (with `_TVDOS_IS_VT_PANE`
+  set — which makes the boot block run `commandrc` but skip the vtmgr/AUTOEXEC
+  launch — and a `_BIOS` stub captured live from the main context) then runs
+  `command -c \AUTOEXEC.BAT`, all in ONE direct `eval` so the launcher shares
+  scope with `_TVDOS`/`files`/`execApp`.
+
+### Output/input shimming (in the pane bootstrap)
+
+`con` and the global `print`/`println` family are plain JS, so the bootstrap
+overrides them to read/write the per-VT shared-memory buffers instead of the
+physical GPU. **`sys` and `graphics` are host objects and CANNOT be overridden
+from JS** — this is the key constraint that shapes everything below.
+
+- The shimmed `print` is a faithful JS port of the GPU's TTY interpreter
+  (`GlassTty.acceptChar` + `GraphicsAdapter` handlers): control bytes, the
+  `\x84<decimal>u` "emit char by code" escape (used by `con.prnch`), CSI cursor
+  moves / erase / SGR colours, and the `?25` cursor-visibility private sequence.
+  A swallow-only parser is NOT enough — TVDOS apps drive the screen through
+  these `print` escapes.
+- `con.move`/`con.getyx` are **1-based** (mirroring `graphics.setCursorYX`'s
+  `cx-1` and `getCursorYX`'s `cx+1`); `con.addch` does NOT advance the cursor
+  (matches `graphics.putSymbol`), while `con.prnch` DOES.
+- `command.js`'s `shell.execute` reassigns the global print family to
+  `shell.stdio.out.*`, which call `sys.print` (→ physical GPU). `shell.stdio.out`
+  was made to delegate to a `globalThis.__VT_OUT` hook when present (set by the
+  bootstrap); outside a VT the hook is absent and the path is byte-identical.
+
+### Direct-VRAM apps need a VT-aware base (the `vaddr` pattern)
+
+Apps that write the text area directly via `graphics.getGpuMemBase()` (rather
+than `con.*`/`print`) bypass the shims and paint the physical screen, invading
+whatever VT is visible. They must resolve text-area byte `m` through a
+VT-aware base:
+
+```js
+// physical: backward  (byte m at gpuBase - m)   — getDev inverts to forward-native
+// VT pane:  forward   (byte m at VT_TEXT_PLANE + m, the pane buffer the compositor blits)
+const VT = (typeof globalThis.VT_TEXT_PLANE !== 'undefined')
+const VRAM_BASE = VT ? globalThis.VT_TEXT_PLANE : (graphics.getGpuMemBase() - 253950)
+const VRAM_SGN  = VT ? 1 : -1
+function vaddr(m) { return VRAM_BASE + VRAM_SGN * m }
+```
+
+`sys.memcpy`/`sys.pokeBytes` copy forward in the resolved native memory, so this
+works for both directions. The physical branch is identical to the original
+arithmetic (no regression outside vtmgr). Applied so far in
+`assets/disk0/tvdos/bin/taut.js` and `assets/disk0/hopper/include/aa.mjs`
+(used by `bb.js`). Any future direct-VRAM app needs the same one-line `vaddr`.
+
+### Files
+
+- New: `assets/disk0/tvdos/sbin/vtmgr.js` (dispatcher + per-pane bootstrap)
+- `assets/disk0/tvdos/bin/command.js`: `chvt` builtin, `[N]` prompt prefix for
+  VT 2-6, `shell.stdio.out` → `__VT_OUT` delegation
+- `assets/disk0/tvdos/TVDOS.SYS`: boot block runs `\commandrc` (env) in every
+  context, then — only when `!_TVDOS_IS_VT_PANE` — launches `tvdos/sbin/vtmgr`
+  and, on its exit, `\AUTOEXEC.BAT` as the fallback shell
+- `assets/disk0/commandrc`: env-only `set` commands (PATH/INCLPATH/HELPPATH/KEYBOARD)
+- `assets/disk0/AUTOEXEC.BAT`: per-console launch (Korean IME + `command -fancy`)
+- `assets/disk0/tvdos/bin/taut.js`, `assets/disk0/hopper/include/aa.mjs`:
+  `vaddr` VT-aware direct-VRAM addressing
+
+### Gotcha: injectIntChk vs. embedded source
+
+`execApp`/`require` run a program's source through `injectIntChk` (TVDOS.SYS),
+which sed-rewrites the **first** `while`/`for`/`do` of each kind to call a
+per-exec `tvdosSIGTERM_<hash>()` SIGTERM check. When vtmgr embeds the pane
+bootstrap as a string literal, one of those rewrites can land inside the literal
+— and the pane context has no such symbol. vtmgr strips them from the bootstrap
+string with `raw.replace(/tvdosSIGTERM_[A-Za-z0-9_]+\(\);?/g, '')`. Any future
+code that builds executable source as a string literal must do the same.

assets/disk0/AUTOEXEC.BAT

@@ -1,12 +1,11 @@
-echo "Starting TVDOS..."
-
-rem put set-xxx commands here:
-set PATH=\tvdos\installer;\tvdos\tuidev;\tbas;\hopper\bin;$PATH
-set INCLPATH=\hopper\include;$INCLPATH
-set HELPPATH=\hopper\help;$HELPPATH
-set KEYBOARD=us_colemak
-
-rem this line specifies which shell to be presented after the boot precess:
+rem AUTOEXEC.BAT -- per-console launch script. Run once for every console:
+rem each virtual-console pane runs it (via vtmgr's bootstrap), and the boot
+rem shell runs it as the fallback once vtmgr exits (Alt-0). Environment setup
+rem (`set` commands) lives in \commandrc, which TVDOS.SYS runs before this.
+rem
+rem Korean IME registers a per-CONTEXT handler (unicode.uniprint), so it must
+rem run per-console here rather than once at boot.
 tvdos/i18n/korean
-zfm
+
+rem The interactive shell for this console.
 command -fancy

assets/disk0/commandrc

@@ -0,0 +1,9 @@
+rem commandrc -- environment setup, run by TVDOS.SYS in EVERY context
+rem (the boot shell AND every virtual-console pane). Put `set` commands and
+rem other env-only configuration here. Do NOT launch apps from this file:
+rem app launches belong in AUTOEXEC.BAT (run per-console by vtmgr).
+
+set PATH=\tvdos\installer;\tvdos\tuidev;\tbas;\hopper\bin;$PATH
+set INCLPATH=\hopper\include;$INCLPATH
+set HELPPATH=\hopper\help;$HELPPATH
+set KEYBOARD=us_colemak

assets/disk0/tvdos/TVDOS.SYS

@@ -1471,9 +1471,40 @@ try {
     serial.println("Warning: Could not load HSDPA driver: " + e.message)
 }
 
-// Boot script
-serial.println(`TVDOS.SYS initialised on VM ${sys.getVmId()}, running boot script...`);
+// Boot script. The work is split across two files:
+//   \commandrc    -- environment (`set` commands); run in EVERY context.
+//   \AUTOEXEC.BAT -- per-console launch (IME + interactive shell).
+// vtmgr re-evaluates TVDOS.SYS inside each per-VT pane; a pane sets
+// _TVDOS_IS_VT_PANE so it only replays the environment here and leaves the
+// AUTOEXEC launch to vtmgr's pane bootstrap (which avoids recursively
+// spawning vtmgr inside a pane).
+{
+    let cmdsrc = files.open("A:/tvdos/bin/command.js").sread()
+    let runBatch = (path) => eval(`var _BAT=function(exec_args){${cmdsrc}\n};_BAT`)(["", "-c", path])
 
-let cmdfile = files.open("A:/tvdos/bin/command.js")
-eval(`var _AUTOEXEC=function(exec_args){${cmdfile.sread()}\n};` +
-      `_AUTOEXEC`)(["", "-c", "\\AUTOEXEC.BAT"])
+    // Environment first, boot and pane alike. Gives every pane the same
+    // PATH / KEYBOARD / etc. natively, with no env-snapshot replay needed.
+    // \commandrc has no .BAT extension (so command.js's batch-file path,
+    // which keys off the extension, won't pick it up); run it line-by-line.
+    // `set` mutates the shared _TVDOS.variables, so the effect persists across
+    // the per-line shell invocations. Skip blanks and `rem` comments.
+    let rcFile = files.open("A:/commandrc")
+    if (rcFile.exists) {
+        rcFile.sread().split('\n').forEach((line) => {
+            let t = line.trim()
+            if (t.length > 0 && !/^rem(\s|$)/i.test(t)) runBatch(line)
+        })
+    }
+
+    if (typeof _TVDOS_IS_VT_PANE === "undefined" || !_TVDOS_IS_VT_PANE) {
+        serial.println(`TVDOS.SYS initialised on VM ${sys.getVmId()}, running boot script...`);
+        // Boot console: hand the screen to the virtual-console multiplexer.
+        // When it exits (Alt-0), fall through to AUTOEXEC so the console is
+        // never left bare.
+        runBatch("tvdos/sbin/vtmgr")
+        runBatch("\\AUTOEXEC.BAT")
+    }
+    else {
+        serial.println(`TVDOS.SYS re-initialised in VT pane on VM ${sys.getVmId()}`);
+    }
+}

assets/disk0/tvdos/bin/command.js

@@ -30,7 +30,18 @@ function makeHash() {
 const shellID = makeHash()
 
 function print_prompt_text() {
+    // VT pane indicator: shown for VT 2..6, not VT 1 (the default) so the
+    // unmodified prompt is what users see when they never touch virtual
+    // consoles. VT_NUM is set by vtmgr's pane bootstrap.
+    let vtPrefix = ""
+    if (typeof VT_NUM !== "undefined" && VT_NUM > 1) vtPrefix = "[" + VT_NUM + "] "
     if (goFancy) {
+        if (vtPrefix) {
+            con.color_pair(161,253)
+            print(`\u00DD${VT_NUM}`)
+            con.color_pair(253,161)
+            con.addch(16);con.curs_right()
+        }
         con.color_pair(239,161)
         print(" "+CURRENT_DRIVE+":")
         con.color_pair(161,253)
@@ -49,9 +60,9 @@ function print_prompt_text() {
     else {
 //        con.color_pair(253,255)
         if (errorlevel != 0 && errorlevel != "undefined" && errorlevel != undefined)
-            print(CURRENT_DRIVE + ":\\" + shell_pwd.join("\\") + " [" + errorlevel + "]" + PROMPT_TEXT)
+            print(vtPrefix + CURRENT_DRIVE + ":\\" + shell_pwd.join("\\") + " [" + errorlevel + "]" + PROMPT_TEXT)
         else
-            print(CURRENT_DRIVE + ":\\" + shell_pwd.join("\\") + PROMPT_TEXT)
+            print(vtPrefix + CURRENT_DRIVE + ":\\" + shell_pwd.join("\\") + PROMPT_TEXT)
     }
 }
 
@@ -620,6 +631,21 @@ shell.coreutils = {
     },
     panic: function(args) {
         throw Error("Panicking command.js")
+    },
+    chvt: function(args) {
+        // Request a switch to another virtual console. Only meaningful when
+        // running inside a pane spawned by vtmgr (VT_CTRL_ADDR is set by the
+        // pane bootstrap). Outside that environment this is a no-op error.
+        if (args[1] === undefined) { printerrln("Usage: chvt N (1..6)"); return 1 }
+        let n = parseInt(args[1])
+        if (isNaN(n) || n < 1 || n > 6) { printerrln("chvt: N must be in 1..6"); return 1 }
+        if (typeof VT_CTRL_ADDR === "undefined") {
+            printerrln("chvt: not running under vtmgr (no VT context)"); return 1
+        }
+        // CTRL_SWITCH_REQUEST is byte +1 of the shared CTRL area. Dispatcher
+        // picks this up on its next 30 Hz tick and performs the switch.
+        sys.poke(VT_CTRL_ADDR + 1, n)
+        return 0
     }
 }
 // define command aliases here
@@ -636,10 +662,14 @@ shell.coreutils.where = shell.coreutils.which
 Object.freeze(shell.coreutils)
 shell.stdio = {
     out: {
-        print:      function(s) { sys.print(s) },
-        println:    function(s) { if (s === undefined) sys.print("\n"); else sys.print(s+"\n") },
-        printerr:   function(s) { sys.print("\x1B[31m"+s+"\x1B[m") },
-        printerrln: function(s) { if (s === undefined) sys.print("\n"); else sys.print("\x1B[31m"+s+"\x1B[m\n") },
+        // When running inside a vtmgr virtual console, __VT_OUT routes output
+        // to the pane's text-plane buffer instead of the physical GPU (which
+        // the compositor would otherwise overwrite). Outside a VT the hook is
+        // absent and these fall through to sys.print exactly as before.
+        print:      function(s) { if (globalThis.__VT_OUT) globalThis.__VT_OUT.print(s); else sys.print(s) },
+        println:    function(s) { if (globalThis.__VT_OUT) globalThis.__VT_OUT.println(s); else { if (s === undefined) sys.print("\n"); else sys.print(s+"\n") } },
+        printerr:   function(s) { if (globalThis.__VT_OUT) globalThis.__VT_OUT.printerr(s); else sys.print("\x1B[31m"+s+"\x1B[m") },
+        printerrln: function(s) { if (globalThis.__VT_OUT) globalThis.__VT_OUT.printerrln(s); else { if (s === undefined) sys.print("\n"); else sys.print("\x1B[31m"+s+"\x1B[m\n") } },
     },
     pipe: {
         print:      function(s) { if (shell.getPipe() === undefined) throw Error("No pipe opened"); shell.appendToCurrentPipe(s);  },
@@ -955,6 +985,180 @@ shell.removePipe = function() {
 Object.freeze(shell)
 _G.shell = shell
 
+///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+// TAB AUTOCOMPLETION
+//
+// Invoked by TAB at the interactive prompt. Only active when BOTH:
+//   1. wintex.mjs is available (provides the selection popup), AND
+//   2. goFancy == true.
+// One candidate  -> expand immediately (no popup).
+// Many candidates -> wintex popup; user scrolls and selects, or Esc/Cancel to
+//                    discard. The popup over-draws the screen without saving
+//                    what was beneath it, so we snapshot the text plane before
+//                    and copy it back after (the shell can't just redraw like a
+//                    full-screen TUI — there's scrollback above the prompt).
+///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+
+// Lazily-resolved wintex module. undefined = not probed yet, null = unavailable.
+let _acWin = undefined
+function getAutocompleteWin() {
+    if (_acWin !== undefined) return _acWin
+    _acWin = null
+    try {
+        let w = require("wintex") // resolved through INCLPATH (\tvdos\include\wintex.mjs)
+        if (w && typeof w.showDialog === "function") _acWin = w
+    } catch (e) {
+        debugprintln("command.js > autocomplete: wintex unavailable: " + e)
+    }
+    return _acWin
+}
+
+// List a directory's entries, swallowing any IO error.
+function _acListDir(fullPath) {
+    try {
+        let f = files.open(fullPath)
+        if (!f.exists || !f.isDirectory) return []
+        return f.list() || []
+    } catch (e) { return [] }
+}
+
+// Strip a trailing PATHEXT extension so command names show without ".js" etc.
+function _acStripExt(name) {
+    let lower = name.toLowerCase()
+    let exts = (_TVDOS.variables.PATHEXT || "").split(';').filter(function(e){ return e.length > 0 })
+    for (let i = 0; i < exts.length; i++) {
+        let e = exts[i].toLowerCase()
+        if (lower.endsWith(e)) return name.substring(0, name.length - e.length)
+    }
+    return name
+}
+
+// Candidates for the command position (first word, no path separators):
+// shell built-ins + runnable files found along the current dir, drive root and PATH.
+function _acCommandCandidates(prefix) {
+    let lower = prefix.toLowerCase()
+    let seen = {}
+    let out = []
+    function add(name) {
+        let k = name.toLowerCase()
+        if (seen[k]) return
+        seen[k] = true
+        out.push({ label: name, value: name + ' ', isDir: false })
+    }
+
+    // shell built-ins (and their aliases)
+    Object.keys(shell.coreutils).forEach(function(k) {
+        if (k.toLowerCase().startsWith(lower)) add(k)
+    })
+
+    // runnable files: search the same places shell.execute does, in the same order
+    let exts = (_TVDOS.variables.PATHEXT || "").split(';')
+        .filter(function(e){ return e.length > 0 }).map(function(e){ return e.toLowerCase() })
+    let dirFulls = [shell.resolvePathInput('.').full] // current directory first
+    _TVDOS.getPath().forEach(function(d) {
+        dirFulls.push((d === '' || d === undefined) ? `${CURRENT_DRIVE}:\\` : shell.resolvePathInput(d).full)
+    })
+    dirFulls.forEach(function(full) {
+        _acListDir(full).forEach(function(it) {
+            if (it.isDirectory) return
+            let nameLower = (it.name || '').toLowerCase()
+            if (!exts.some(function(e){ return nameLower.endsWith(e) })) return // only runnables
+            let stripped = _acStripExt(it.name)
+            if (stripped.toLowerCase().startsWith(lower)) add(stripped)
+        })
+    })
+    return out
+}
+
+// Candidates for a path argument. The word may carry a directory prefix
+// (kept verbatim) and a partial basename that we match against the directory.
+function _acPathCandidates(word) {
+    let sepIdx = Math.max(word.lastIndexOf('\\'), word.lastIndexOf('/'))
+    let dirPart, basePart, listArg
+    if (sepIdx >= 0) {
+        dirPart  = word.substring(0, sepIdx + 1) // includes the trailing separator
+        basePart = word.substring(sepIdx + 1)
+        listArg  = dirPart
+    } else {
+        dirPart  = ''
+        basePart = word
+        listArg  = '.'
+    }
+    let resolved = shell.resolvePathInput(listArg)
+    if (resolved === undefined) return []
+    let sep = (dirPart.length > 0 && dirPart.charAt(dirPart.length - 1) === '/') ? '/' : '\\'
+    let lower = basePart.toLowerCase()
+    let out = []
+    _acListDir(resolved.full).forEach(function(it) {
+        let name = it.name || ''
+        if (!name.toLowerCase().startsWith(lower)) return
+        out.push({
+            // directories get a trailing separator so completion can continue into them;
+            // files get a trailing space so the next argument can be typed straight away.
+            label: name + (it.isDirectory ? '\\' : ''),
+            value: dirPart + name + (it.isDirectory ? sep : ' '),
+            isDir: it.isDirectory
+        })
+    })
+    return out
+}
+
+// Work out what is being completed at `caret` within `line`.
+// Returns { wordStart, word, candidates } (candidates sorted by label).
+function computeCompletion(line, caret) {
+    let wordStart = caret
+    while (wordStart > 0 && line.charAt(wordStart - 1) !== ' ') wordStart -= 1
+    let word = line.substring(wordStart, caret)
+    let isFirstWord = (line.substring(0, wordStart).trim().length === 0)
+    let hasPathSep = (word.indexOf('\\') >= 0 || word.indexOf('/') >= 0 || word.indexOf(':') >= 0)
+    let candidates = (isFirstWord && !hasPathSep) ? _acCommandCandidates(word) : _acPathCandidates(word)
+    candidates.sort(function(a, b) { return (a.label < b.label) ? -1 : (a.label > b.label) ? 1 : 0 })
+    return { wordStart: wordStart, word: word, candidates: candidates }
+}
+
+// --- text-plane snapshot/restore (so the popup leaves no artefacts) ---------
+// In a vtmgr pane the shimmed con/print draw into the pane buffer
+// (globalThis.VT_TEXT_PLANE, forward layout); on the physical console they
+// draw into the GPU text area (mapped at getGpuMemBase()-253950). vaddr(0) is
+// that base in either case; sys.memcpy reads/writes it forward-native.
+// NOTE: 7681, not the full 7682-byte text area: relPtrInDev() bounds-checks
+// `from+len` inclusively, so the final byte (bottom-right char cell, never
+// touched by a centred popup) is unreachable by a single memcpy.
+const _AC_TEXTAREA_BYTES = 7681
+let _acTextBase = null
+let _acScratchPtr = 0
+function _acTextAreaBase() {
+    if (_acTextBase === null) {
+        _acTextBase = (typeof globalThis.VT_TEXT_PLANE !== 'undefined')
+            ? globalThis.VT_TEXT_PLANE
+            : (graphics.getGpuMemBase() - 253950)
+    }
+    return _acTextBase
+}
+function _acSnapshotScreen() {
+    if (_acScratchPtr === 0) _acScratchPtr = sys.malloc(_AC_TEXTAREA_BYTES)
+    sys.memcpy(_acTextAreaBase(), _acScratchPtr, _AC_TEXTAREA_BYTES)
+}
+function _acRestoreScreen() {
+    if (_acScratchPtr === 0) return
+    sys.memcpy(_acScratchPtr, _acTextAreaBase(), _AC_TEXTAREA_BYTES)
+}
+
+// Modal popup of candidates. Returns the chosen item, or null if discarded.
+function _acShowPopup(win, candidates) {
+    let res = win.showDialog({
+        title: `Complete (${candidates.length})`,
+        list: {
+            items: candidates,
+            height: Math.min(12, candidates.length),
+            onActivate: function(item, idx, key) { return 'select' }
+        },
+        buttons: [{ label: 'Cancel', action: 'cancel' }]
+    })
+    if (res && res.action === 'select' && res.listItem) return res.listItem
+    return null
+}
+
 ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 
 // ensure USERCONFIGPATH directory exists
@@ -1012,23 +1216,133 @@ if (goInteractive) {
         print_prompt_text()
 
         var cmdbuf = ""
+        var caret = 0 // insertion point within cmdbuf, 0..cmdbuf.length
+
+        // Self-contained line editor with a movable caret (so command.js does
+        // NOT depend on wintex being installed). The prompt has just been
+        // printed, so the current cursor marks where the editable text begins.
+        // We track that anchor and rebuild the on-screen line from it, decoding
+        // line-wrap ourselves so the maths holds in both the physical console
+        // and a vtmgr pane (whose con.move CLAMPS x instead of wrapping it).
+        let [baseY, baseX] = con.getyx() // 1-based
+        let termCols = con.getmaxyx()[1]
+
+        // absolute (y,x) on screen for caret index `idx`
+        function caretPos(idx) {
+            let abs = (baseX - 1) + idx
+            return [baseY + ((abs / termCols) | 0), (abs % termCols) + 1]
+        }
+        function gotoCaret() {
+            let [cy, cx] = caretPos(caret)
+            con.move(cy, cx)
+        }
+        // reprint cmdbuf from index `from` to the end, optionally padding with
+        // `clearTrail` blanks to wipe characters left over by a now-shorter
+        // line, then park the hardware cursor back on the caret.
+        function refresh(from, clearTrail) {
+            let [py, px] = caretPos(from)
+            con.move(py, px)
+            print(cmdbuf.substring(from))
+            for (let i = 0; i < clearTrail; i++) print(" ")
+            gotoCaret()
+        }
+        // replace the whole buffer (used by history recall)
+        function setBuf(next) {
+            let oldLen = cmdbuf.length
+            cmdbuf = next
+            caret = cmdbuf.length
+            refresh(0, Math.max(0, oldLen - cmdbuf.length))
+        }
+
+        // Replace the word [wordStart, caret) with `value`, keeping any text to
+        // the right of the caret, then reprint the line from `wordStart`.
+        function applyCompletion(wordStart, value) {
+            let oldLen = cmdbuf.length
+            cmdbuf = cmdbuf.substring(0, wordStart) + value + cmdbuf.substring(caret)
+            caret = wordStart + value.length
+            con.color_pair(shell.usrcfg.textCol, 255)
+            refresh(wordStart, Math.max(0, oldLen - cmdbuf.length))
+        }
+
+        // TAB handler. No-op unless fancy mode is on and wintex is installed.
+        function tryAutocomplete() {
+            if (!goFancy) return
+            let win = getAutocompleteWin()
+            if (!win) return
+
+            let comp = computeCompletion(cmdbuf, caret)
+            let cands = comp.candidates
+            if (cands.length === 0) return
+            if (cands.length === 1) { applyCompletion(comp.wordStart, cands[0].value); return }
+
+            _acSnapshotScreen()
+            let chosen = _acShowPopup(win, cands)
+            _acRestoreScreen()
+
+            // The popup drives input through input.withEvent (physical held-key
+            // state), which bypasses the buffer con.getch reads. Inside a vtmgr
+            // pane the dispatcher keeps draining physical keystrokes into this
+            // pane's input ring the whole time the popup is open, so the navigation
+            // keys (and the closing Enter) would otherwise surface as phantom input
+            // afterwards. Flush them. (On the physical console readKey self-clears,
+            // so this is harmless there.)
+            con.resetkeybuf()
+
+            // The popup hid the caret and clobbered colours; restore the prompt
+            // editing state. The screen content is already back from the snapshot.
+            con.curs_set(1)
+            con.color_pair(shell.usrcfg.textCol, 255)
+            gotoCaret()
+
+            if (chosen) applyCompletion(comp.wordStart, chosen.value)
+        }
 
         while (true) {
             let key = con.getch()
 
             // printable chars
             if (key >= 32 && key <= 126) {
-                var s = String.fromCharCode(key)
-                cmdbuf += s
-                print(s)
+                let s = String.fromCharCode(key)
+                let atEnd = (caret === cmdbuf.length)
+                cmdbuf = cmdbuf.substring(0, caret) + s + cmdbuf.substring(caret)
+                caret += 1
+                if (atEnd) print(s) // fast path: simple append
+                else refresh(caret - 1, 0)
             }
-            // backspace
-            else if (key === con.KEY_BACKSPACE && cmdbuf.length > 0) {
-                cmdbuf = cmdbuf.substring(0, cmdbuf.length - 1)
-                print(String.fromCharCode(key))
+            // TAB: autocomplete (fancy mode + wintex only; otherwise a no-op)
+            else if (key === con.KEY_TAB) {
+                tryAutocomplete()
+            }
+            // backspace: delete the char to the left of the caret
+            else if (key === con.KEY_BACKSPACE && caret > 0) {
+                cmdbuf = cmdbuf.substring(0, caret - 1) + cmdbuf.substring(caret)
+                caret -= 1
+                refresh(caret, 1)
+            }
+            // forward delete: delete the char under the caret
+            else if (key === con.KEY_DELETE && caret < cmdbuf.length) {
+                cmdbuf = cmdbuf.substring(0, caret) + cmdbuf.substring(caret + 1)
+                refresh(caret, 1)
+            }
+            // caret left
+            else if (key === con.KEY_LEFT) {
+                if (caret > 0) { caret -= 1; gotoCaret() }
+            }
+            // caret right
+            else if (key === con.KEY_RIGHT) {
+                if (caret < cmdbuf.length) { caret += 1; gotoCaret() }
+            }
+            // jump to start of line
+            else if (key === con.KEY_HOME) {
+                caret = 0; gotoCaret()
+            }
+            // jump to end of line
+            else if (key === con.KEY_END) {
+                caret = cmdbuf.length; gotoCaret()
             }
             // enter
             else if (key === 10 || key === con.KEY_RETURN) {
+                caret = cmdbuf.length; gotoCaret()
                 println()
 
                 errorlevel = shell.execute(cmdbuf)
@@ -1044,32 +1358,17 @@ if (goInteractive) {
             // up arrow
             else if (key === con.KEY_UP && cmdHistory.length > 0 && cmdHistoryScroll < cmdHistory.length) {
                 cmdHistoryScroll += 1
-
-                // back the cursor in order to type new cmd
-                var x = 0
-                for (x = 0; x < cmdbuf.length; x++) print(String.fromCharCode(8))
-                cmdbuf = cmdHistory[cmdHistory.length - cmdHistoryScroll]
-                // re-type the new command
-                print(cmdbuf)
-
+                setBuf(cmdHistory[cmdHistory.length - cmdHistoryScroll])
             }
             // down arrow
             else if (key === con.KEY_DOWN) {
-                if (cmdHistoryScroll > 0) {
-                    // back the cursor in order to type new cmd
-                    var x = 0
-                    for (x = 0; x < cmdbuf.length; x++) print(String.fromCharCode(8))
-                    cmdbuf = cmdHistory[cmdHistory.length - cmdHistoryScroll]
-                    // re-type the new command
-                    print(cmdbuf)
-
+                if (cmdHistoryScroll > 1) {
                     cmdHistoryScroll -= 1
+                    setBuf(cmdHistory[cmdHistory.length - cmdHistoryScroll])
                 }
-                else {
-                    // back the cursor in order to type new cmd
-                    var x = 0
-                    for (x = 0; x < cmdbuf.length; x++) print(String.fromCharCode(8))
-                    cmdbuf = ""
+                else if (cmdHistoryScroll === 1) {
+                    cmdHistoryScroll = 0
+                    setBuf("")
                 }
             }
         }

assets/disk0/tvdos/bin/taut.js

@@ -1042,6 +1042,7 @@ const colVoiceHdr  = 230
 const colVoiceHdrMuted = 249
 const colVoiceHdrMutedCursorUp = 180
 const colSep       = 252
+const colScrollBar = 249
 const colPushBtnBack = 143
 const colTabBarBack = 187
 const colTabBarBack2 = 136
@@ -1231,7 +1232,7 @@ function drawSeparators(style) {
         for (let x = PTNVIEW_OFFSET_X; x < SCRW - 3; x += COLSIZE_TIMELINE_FULL) {
             for (let y = 0; y < PTNVIEW_HEIGHT+1; y++) {
                 let memOffset = (y+PTNVIEW_OFFSET_Y-2) * SCRW + (x-1)
-                let bgColOffset = GPU_MEM - TEXT_BACK_OFF - memOffset
+                let bgColOffset = vaddr(TEXT_BACK_OFF + memOffset)
                 let oldBgCol = sys.peek(bgColOffset)
                 if (oldBgCol == 255) {
                     sys.poke(bgColOffset, colColumnSep)
@@ -1806,6 +1807,17 @@ const TEXT_BACK_OFF = 2 + 2560
 const TEXT_CHAR_OFF = 2 + 2560 + 2560
 const TEXT_PLANES   = [TEXT_CHAR_OFF, TEXT_BACK_OFF, TEXT_FORE_OFF]
 
+// Direct text-VRAM addressing. On real hardware the GPU text area is addressed
+// backward (byte m at GPU_MEM - m). Under vtmgr's virtual consoles the physical
+// GPU is owned by the compositor, so direct writes must instead target this
+// pane's forward text-plane buffer (VT_TEXT_PLANE + m), which the compositor
+// blits to the screen. vaddr(m) returns the address of text-area byte m for the
+// current environment; the physical branch is identical to the old arithmetic.
+const _VT_VRAM     = (typeof globalThis.VT_TEXT_PLANE !== 'undefined')
+const VRAM_BASE    = _VT_VRAM ? globalThis.VT_TEXT_PLANE : GPU_MEM
+const VRAM_SGN     = _VT_VRAM ? 1 : -1
+function vaddr(m) { return VRAM_BASE + VRAM_SGN * m }
+
 // One scratch strip, reused across shifts
 const SCRATCH_PTR = sys.malloc(SCRW * PTNVIEW_HEIGHT)
 
@@ -1828,8 +1840,8 @@ function shiftPatternArea(dy) {
 
     for (let p = 0; p < 3; p++) {
         const chanOff = TEXT_PLANES[p]
-        const srcAddr = GPU_MEM - chanOff - (srcTopY - 1) * SCRW
-        const dstAddr = GPU_MEM - chanOff - (dstTopY - 1) * SCRW
+        const srcAddr = vaddr(chanOff + (srcTopY - 1) * SCRW)
+        const dstAddr = vaddr(chanOff + (dstTopY - 1) * SCRW)
         sys.memcpy(srcAddr, SCRATCH_PTR, stripBytes)
         sys.memcpy(SCRATCH_PTR, dstAddr, stripBytes)
     }
@@ -1850,9 +1862,9 @@ function shiftPatternAreaHorizontal(dVoice) {
     for (let p = 0; p < 3; p++) {
         const chanOff = TEXT_PLANES[p]
         for (let vr = 0; vr < PTNVIEW_HEIGHT; vr++) {
-            const rowBase = GPU_MEM - chanOff - (PTNVIEW_OFFSET_Y + vr - 1) * SCRW
-            sys.memcpy(rowBase - srcOff, SCRATCH_PTR, SALVAGE_HORIZ_LEN)
-            sys.memcpy(SCRATCH_PTR, rowBase - dstOff, SALVAGE_HORIZ_LEN)
+            const idxBase = chanOff + (PTNVIEW_OFFSET_Y + vr - 1) * SCRW
+            sys.memcpy(vaddr(idxBase + srcOff), SCRATCH_PTR, SALVAGE_HORIZ_LEN)
+            sys.memcpy(SCRATCH_PTR, vaddr(idxBase + dstOff), SALVAGE_HORIZ_LEN)
         }
     }
 }
@@ -2165,9 +2177,9 @@ function shiftOrdersAreaHorizontal(dVoice) {
     for (let p = 0; p < 3; p++) {
         const chanOff = TEXT_PLANES[p]
         for (let vr = 0; vr < PTNVIEW_HEIGHT; vr++) {
-            const rowBase = GPU_MEM - chanOff - (PTNVIEW_OFFSET_Y + vr - 1) * SCRW
-            sys.memcpy(rowBase - srcOff, SCRATCH_PTR, stripWidth)
-            sys.memcpy(SCRATCH_PTR, rowBase - dstOff, stripWidth)
+            const idxBase = chanOff + (PTNVIEW_OFFSET_Y + vr - 1) * SCRW
+            sys.memcpy(vaddr(idxBase + srcOff), SCRATCH_PTR, stripWidth)
+            sys.memcpy(SCRATCH_PTR, vaddr(idxBase + dstOff), stripWidth)
         }
     }
 }
@@ -3271,7 +3283,7 @@ function drawSamplesListColumn() {
         const indPos = (maxScroll === 0) ? 0 : ((smpListScroll * (SMP_LIST_H - 1) / maxScroll) | 0)
         for (let r = 0; r < SMP_LIST_H; r++) {
             con.move(SMP_LIST_Y + r, SMP_LIST_SCROLL_X)
-            con.color_pair(colStatus, colSmpListBg)
+            con.color_pair(colScrollBar, colSmpListBg)
 
             let scrollChar = (r == 0) ? sym.taut_scrollgutter_top : (r == SMP_LIST_H - 1) ? sym.taut_scrollgutter_bot : sym.taut_scrollgutter_mid
             if (r == indPos) scrollChar += 3;
@@ -3888,7 +3900,7 @@ function drawInstrumentsListColumn() {
         const indPos = (maxScroll === 0) ? 0 : ((instListScroll * (INST_LIST_H - 1) / maxScroll) | 0)
         for (let r = 0; r < INST_LIST_H; r++) {
             con.move(INST_LIST_Y + r, INST_LIST_SCROLL_X)
-            con.color_pair(colStatus, colInstListBg)
+            con.color_pair(colScrollBar, colInstListBg)
 
             let scrollChar = (r == 0) ? sym.taut_scrollgutter_top : (r == INST_LIST_H - 1) ? sym.taut_scrollgutter_bot : sym.taut_scrollgutter_mid
             if (r == indPos) scrollChar += 3;
@@ -5133,6 +5145,7 @@ function openHelpPopup() {
             bg: colPopupBack,
             height: HELP_CONTENT_H,
             width: HELP_CONTENT_W+4,
+            scrollbarChars: popupScrollbarChars,
             selectable: () => false,
             renderItem: (ctx) => {
                 con.color_pair(colText, ctx.listBg)
@@ -5177,6 +5190,12 @@ const popupDrawFrame = (wo) => {
     }
 }
 
+// Taut's charset carries dedicated scrollbar glyphs at 0xBA..0xBF (empty
+// top/mid/bottom caps 0xBA..0xBC, filled top/mid/bottom thumb 0xBD..0xBF).
+// wintex defaults to the CP437-safe 0xBA/0xDB pair, so pass these to every
+// list popup to render the scrollbar in taut's style.
+const popupScrollbarChars = [0xBA, 0xBB, 0xBC, 0xBD, 0xBE, 0xBF]
+
 // Standard colour palette shared by every taut popup so wintex's defaults blend
 // with taut's popup chrome.
 const popupColours = {
@@ -5291,6 +5310,7 @@ function openRetunePopup() {
             height: listH,
             width: 36,
             cursor: selIdx,
+            scrollbarChars: popupScrollbarChars,
             renderItem: (ctx) => {
                 const e = ctx.item.preset
                 const isCur = (e.index === PITCH_PRESET_IDX)
@@ -5362,6 +5382,7 @@ function openFlagsPopup() {
             width: 22,
             drawWell: false,
             showScrollbar: false,
+            scrollbarChars: popupScrollbarChars,
             selectable: (it) => it.kind === 'tone' || it.kind === 'intp',
             renderItem: (ctx) => {
                 const it = ctx.item

assets/disk0/tvdos/include/wintex.mjs

@@ -217,6 +217,13 @@ function scrollHorz(dx, stringSize, stringViewSize, currentCursorPos, currentScr
 //                                               action string to close the dialog,
 //                                               or null to stay open.
 //     showScrollbar: bool?,                  -- default: auto (true when overflowing).
+//     scrollbarChars: number[6]?,            -- glyph codes for the scrollbar:
+//                                               [troughTopEmpty, troughMidEmpty,
+//                                                troughBotEmpty, troughTopFilled,
+//                                                troughMidFilled, troughBotFilled].
+//                                               Default [0xBA,0xBA,0xBA,0xDB,0xDB,0xDB]
+//                                               (CP437-safe). Callers with a custom
+//                                               charset (e.g. taut) pass their own.
 //     drawWell: bool?,                       -- draw the list background
 //     bg: number?,                           -- list background colour (default 242).
 //   },
@@ -307,6 +314,12 @@ function showDialog(opts) {
     const hasList        = !!list
     const listOnActivate = list ? list.onActivate : null
     const listBgColour   = (list && list.bg != null) ? list.bg : listBg
+    // Scrollbar glyphs: [trough top/mid/bottom empty, then top/mid/bottom filled].
+    // Default is CP437-safe (0xBA track, 0xDB thumb); callers with their own
+    // charset (e.g. taut's 0xBA..0xBF) pass a 6-item override.
+    const listScrollbarChars = (list && Array.isArray(list.scrollbarChars) && list.scrollbarChars.length >= 6)
+        ? list.scrollbarChars
+        : [0xBA, 0xBA, 0xBA, 0xDB, 0xDB, 0xDB]
     function firstSelectable(from, dir) {
         if (!hasList || listItems.length === 0) return -1
         let i = from
@@ -531,8 +544,10 @@ function showDialog(opts) {
                 con.move(lbRow + 1 + r, lbCol + lw - 2)
                 const maxScroll = Math.max(1, listItems.length - listHeight)
                 const indPos = (maxScroll <= 0) ? 0 : ((listScroll * (listHeight - 1) / maxScroll) | 0)
-                let trough = (r === 0) ? 0xBA : (r === listHeight - 1) ? 0xBC : 0xBB
-                con.addch(r === indPos ? (trough + 3) : trough)
+                // seg: 0 = top cap, 1 = middle, 2 = bottom cap; +3 selects the
+                // filled (thumb) variant over the empty (trough) one.
+                const seg = (r === 0) ? 0 : (r === listHeight - 1) ? 2 : 1
+                con.addch(listScrollbarChars[(r === indPos) ? seg + 3 : seg])
             }
         }
 

assets/disk0/tvdos/sbin/vtmgr.js

@@ -0,0 +1,561 @@
+// vtmgr — virtual console manager for TVDOS
+//
+// Spawns up to 6 independent shell sessions (virtual consoles), each in its
+// own parallel GraalVM context with its own thread. Each pane runs a real
+// `command -fancy` shell. The dispatcher (this file) owns the physical
+// keyboard, polls Alt-N hotkeys at 30 Hz, blits the active pane's text
+// plane to the GPU's text area, and routes typed characters into the
+// active pane's input ring buffer.
+//
+// Hotkeys: Alt-1..Alt-6 switch to that VT (lazy-spawn on first use).
+//          Alt-0 cleanly tears down vtmgr.
+// Builtins: `chvt N` from inside a pane writes to the switch register.
+
+// ─── shared memory layout ───────────────────────────────────────────────────
+// CTRL_AREA (64 bytes from base)
+//   +0  active_vt        u8 (1..6)
+//   +1  switch_request   u8 (0 = none, 1..6 = target; set by chvt, cleared by dispatcher)
+//   +2  debounce_held    u8
+//   +3  vt_spawned_bits  u8 (bit n-1 set if VT n is alive)
+//   +4..63 reserved
+// VT block (× MAX_VT) starting at base + 64, each VT_BLOCK_SIZE bytes
+//   +0..7 reserved (cursor & color state lives inside text plane itself)
+//   +8    queue_head       u8 (next-read index)
+//   +9    queue_tail       u8 (next-write index)
+//   +10..11 reserved
+//   +12..267 queue_data    (256-byte ring buffer; one slot lost to full/empty disambiguation)
+//   +268..271 reserved (alignment)
+//   +272..7953 text_plane (7682 bytes; mirrors GPU textArea layout exactly)
+
+const MAX_VT = 6
+const CTRL_AREA_SIZE = 64
+const VT_BLOCK_SIZE = 8000
+const TEXT_PLANE_OFFSET = 272
+const TEXT_PLANE_SIZE = 7682
+const QUEUE_DATA_OFFSET = 12
+
+const CTRL_ACTIVE_VT      = 0
+const CTRL_SWITCH_REQUEST = 1
+const CTRL_DEBOUNCE_HELD  = 2
+const CTRL_SPAWNED_BITS   = 3
+
+const GPU_TEXTAREA_OFFSET = 253950
+const TEXT_COLS = 80
+const TEXT_ROWS = 32
+
+const TP_FORE_BASE = 2
+const TP_BACK_BASE = 2 + 2560
+const TP_TEXT_BASE = 2 + 2560 + 2560
+
+const TOTAL_ALLOC_SIZE = CTRL_AREA_SIZE + MAX_VT * VT_BLOCK_SIZE
+const BASE = sys.malloc(TOTAL_ALLOC_SIZE)
+if (!BASE || BASE === 0) { printerrln("vtmgr: sys.malloc failed"); return 1 }
+for (let i = 0; i < TOTAL_ALLOC_SIZE; i++) sys.poke(BASE + i, 0)
+
+const CTRL = BASE
+function vtBlockAddr(n)     { return BASE + CTRL_AREA_SIZE + (n - 1) * VT_BLOCK_SIZE }
+function vtTextPlaneAddr(n) { return vtBlockAddr(n) + TEXT_PLANE_OFFSET }
+
+// ─── pane bootstrap ─────────────────────────────────────────────────────────
+// Read TVDOS.SYS once at startup. Each pane's bootstrap embeds the source
+// (via JSON.stringify-escaped string literal) and evaluates it together with
+// the shell-start code as ONE direct-eval call. This matters because strict-
+// mode direct eval is scope-isolated; if TVDOS.SYS and the shell launcher
+// were two separate evals, the shell launcher wouldn't see `_TVDOS`,
+// `files`, `execApp`, etc. defined by the first eval.
+
+const TVDOS_SYS_SRC = files.open("A:/tvdos/TVDOS.SYS").sread()
+
+// _BIOS is set by the real BIOS before TVDOS.SYS runs; TVDOS.SYS reads
+// _BIOS.FIRST_BOOTABLE_PORT during init. Each pane is a fresh context with no
+// BIOS, so capture the live value here (vtmgr runs in the main context where
+// _BIOS is visible) and re-declare it in every pane bootstrap.
+const BIOS_FIRST_BOOTABLE_PORT = JSON.stringify(_BIOS.FIRST_BOOTABLE_PORT)
+
+// Environment no longer needs snapshotting/replaying: each pane re-evaluates
+// TVDOS.SYS, whose boot block runs \commandrc in every context, so the pane
+// gets the same PATH / KEYBOARD / etc. natively. The pane then runs
+// \AUTOEXEC.BAT (the per-console launch script: IME + interactive shell).
+
+function makePaneBootstrap(vtNum) {
+    const TP_BASE = vtTextPlaneAddr(vtNum)
+    const VT_BLK = vtBlockAddr(vtNum)
+
+    // Launcher code runs after TVDOS.SYS in the SAME eval scope, so `files`,
+    // `eval`, `_TVDOS` etc. resolve via lexical closure. TVDOS.SYS's boot
+    // block already ran \commandrc (env) and skipped its own AUTOEXEC because
+    // the pane sets _TVDOS_IS_VT_PANE; here we run \AUTOEXEC.BAT to launch the
+    // per-console shell.
+    const SHELL_START = ";\n"
+        + "var _cmdfileSrc = files.open('A:/tvdos/bin/command.js').sread();\n"
+        + "eval('var _VTSHELL=function(exec_args){' + _cmdfileSrc + '\\n};_VTSHELL')(['', '-c', '\\\\AUTOEXEC.BAT']);\n"
+
+    const combined = TVDOS_SYS_SRC + SHELL_START
+
+    const raw = `
+globalThis.VT_NUM = ${vtNum}
+globalThis.VT_TEXT_PLANE = ${TP_BASE}
+globalThis.VT_BLOCK_ADDR = ${VT_BLK}
+globalThis.VT_CTRL_ADDR = ${CTRL}
+const TP = ${TP_BASE}
+const VT_BLK = ${VT_BLK}
+const CTRL = ${CTRL}
+const QUEUE_DATA = VT_BLK + ${QUEUE_DATA_OFFSET}
+const QUEUE_HEAD_ADDR = VT_BLK + 8
+const QUEUE_TAIL_ADDR = VT_BLK + 9
+const ACTIVE_VT_ADDR = CTRL + ${CTRL_ACTIVE_VT}
+const COLS = ${TEXT_COLS}, ROWS = ${TEXT_ROWS}
+const FORE_BASE = ${TP_FORE_BASE}, BACK_BASE = ${TP_BACK_BASE}, TEXT_BASE = ${TP_TEXT_BASE}
+
+// ── output shims (write into the per-VT text-plane buffer in shared mem) ──
+// This is a faithful JS port of the GPU's TTY interpreter (GlassTty.acceptChar
+// + GraphicsAdapter handlers). TVDOS apps drive the screen by printing control
+// bytes and escape sequences through print(), so the shim must interpret them
+// exactly as the hardware would: the \\x84<decimal>u "emit char by code" escape
+// (used by con.prnch), CSI cursor moves / erase / SGR colours, and the ?25
+// cursor-visibility private sequence.
+let curX = 0, curY = 0
+let foreCol = 254
+let backCol = 255
+
+// Per-pane cursor visibility lives at VT_BLK+2 (1 = blink on, 0 = hidden).
+// The compositor pushes the active pane's value into the GPU's blink bit.
+const CURSOR_VIS_ADDR = VT_BLK + 2
+sys.poke(CURSOR_VIS_ADDR, 1)
+
+// SGR 30-37 / 40-47 → default 8-colour palette (matches GraphicsAdapter).
+const SGR_PAL = [240, 211, 61, 230, 49, 219, 114, 254]
+
+function writeCursor() {
+    let pos = curY * COLS + curX
+    sys.poke(TP + 0, pos & 0xFF)
+    sys.poke(TP + 1, (pos >> 8) & 0xFF)
+}
+function scrollBufUp(n) {
+    if (n < 1) n = 1
+    if (n > ROWS) n = ROWS
+    for (let p of [FORE_BASE, BACK_BASE, TEXT_BASE]) {
+        for (let y = 0; y < ROWS - n; y++) {
+            for (let x = 0; x < COLS; x++) {
+                sys.poke(TP + p + y * COLS + x, sys.peek(TP + p + (y + n) * COLS + x))
+            }
+        }
+        let clearVal = (p === TEXT_BASE) ? 0 : (p === FORE_BASE ? foreCol : backCol)
+        for (let y = ROWS - n; y < ROWS; y++)
+            for (let x = 0; x < COLS; x++) sys.poke(TP + p + y * COLS + x, clearVal)
+    }
+}
+function putCharRaw(x, y, c) {
+    if (x < 0 || x >= COLS || y < 0 || y >= ROWS) return
+    let off = y * COLS + x
+    sys.poke(TP + TEXT_BASE + off, c & 0xFF)
+    sys.poke(TP + FORE_BASE + off, foreCol)
+    sys.poke(TP + BACK_BASE + off, backCol)
+}
+// Mirror of GraphicsAdapter.setCursorPos: wrap on overflow x, scroll on
+// overflow y, clamp y above the screen.
+function setCursorPos(x, y) {
+    let nx = x, ny = y
+    if (nx >= COLS) { nx = 0; ny += 1 }
+    else if (nx < 0) nx = 0
+    if (ny < 0) ny = 0
+    else if (ny >= ROWS) { scrollBufUp(ny - ROWS + 1); ny = ROWS - 1 }
+    curX = nx; curY = ny
+    writeCursor()
+}
+
+// ── TTY actions (mirror the GraphicsAdapter overrides) ────────────────────
+function ttyPrintable(c) { putCharRaw(curX, curY, c); setCursorPos(curX + 1, curY) }
+function ttyCrlf() {
+    let ny = curY + 1
+    setCursorPos(0, (ny >= ROWS) ? ROWS - 1 : ny)
+    if (ny >= ROWS) scrollBufUp(1)
+}
+function ttyBackspace() { let x = curX, y = curY; setCursorPos(x - 1, y); putCharRaw(curX, curY, 0x20) }
+function ttyTab() { setCursorPos(((curX / 8 | 0) + 1) * 8, curY) }
+function ttyResetStatus() { foreCol = 253; backCol = 255 }
+function ttyEmitChar(code) { putCharRaw(curX, curY, code); setCursorPos(curX + 1, curY) }
+function ttyCursorUp(n) { setCursorPos(curX, curY - n) }
+function ttyCursorDown(n) { let ny = curY + n; setCursorPos(curX, (ny >= ROWS) ? ROWS - 1 : ny) }
+function ttyCursorFwd(n) { setCursorPos(curX + n, curY) }
+function ttyCursorBack(n) { setCursorPos(curX - n, curY) }
+function ttyCursorNextLine(n) { let ny = curY + n; setCursorPos(0, (ny >= ROWS) ? ROWS - 1 : ny); if (ny >= ROWS) scrollBufUp(ny - ROWS + 1) }
+function ttyCursorPrevLine(n) { setCursorPos(0, curY - n) }
+function ttyCursorX(n) { setCursorPos(n, curY) }
+function ttyCursorXY(row, col) { setCursorPos(col - 1, row - 1) }
+function ttyEraseInDisp(arg) {
+    if (arg === 2) {
+        for (let i = 0; i < COLS * ROWS; i++) {
+            sys.poke(TP + TEXT_BASE + i, 0)
+            sys.poke(TP + FORE_BASE + i, foreCol)
+            sys.poke(TP + BACK_BASE + i, backCol)
+        }
+        curX = 0; curY = 0; writeCursor()
+    }
+    // other args: GraphicsAdapter TODOs (throws); we no-op for safety
+}
+function ttySgr1(arg) {
+    if (arg >= 30 && arg <= 37) foreCol = SGR_PAL[arg - 30]
+    else if (arg >= 40 && arg <= 47) backCol = SGR_PAL[arg - 40]
+    else if (arg === 7) { let t = foreCol; foreCol = backCol; backCol = t }
+    else if (arg === 0) { foreCol = 253; backCol = 255; sys.poke(CURSOR_VIS_ADDR, 1) }
+}
+function ttySgr3(a1, a2, a3) {
+    if (a1 === 38 && a2 === 5) foreCol = a3
+    else if (a1 === 48 && a2 === 5) backCol = a3
+}
+function ttyPrivH(arg) { if (arg === 25) sys.poke(CURSOR_VIS_ADDR, 1) }
+function ttyPrivL(arg) { if (arg === 25) sys.poke(CURSOR_VIS_ADDR, 0) }
+
+// ── escape-sequence state machine (mirror of GlassTty.acceptChar) ─────────
+// States: 0 INITIAL, 1 ESC, 2 CSI, 3 NUM1, 4 SEP1, 5 NUM2, 6 SEP2, 7 NUM3,
+//         8 PRIVATESEQ, 9 PRIVATENUM, 10 XCSI, 11 XNUM1
+let escState = 0
+let escArgs = []
+function isDig(c) { return c >= 0x30 && c <= 0x39 }
+function escReset() { escState = 0; escArgs.length = 0 }
+// reject() in hardware returns the char as printable; replicate by printing it
+function escRejectPrint(c) { escReset(); ttyPrintable(c) }
+
+function processByte(c) {
+    switch (escState) {
+        case 0: // INITIAL
+            if (c === 0x1B) escState = 1
+            else if (c === 0x84) escState = 10
+            else if (c === 0x0A) ttyCrlf()
+            else if (c === 0x08) ttyBackspace()
+            else if (c === 0x09) ttyTab()
+            else if (c === 0x07) { /* bell */ }
+            else if (c >= 0x00 && c <= 0x1F) { /* other control: ignored */ }
+            else ttyPrintable(c)
+            break
+        case 1: // ESC
+            if (c === 0x63) { ttyResetStatus(); escReset() }       // 'c'
+            else if (c === 0x5B) escState = 2                       // '['
+            else escRejectPrint(c)
+            break
+        case 2: // CSI
+            if (c === 0x41) { ttyCursorUp(1); escReset() }
+            else if (c === 0x42) { ttyCursorDown(1); escReset() }
+            else if (c === 0x43) { ttyCursorFwd(1); escReset() }
+            else if (c === 0x44) { ttyCursorBack(1); escReset() }
+            else if (c === 0x45) { ttyCursorNextLine(1); escReset() }
+            else if (c === 0x46) { ttyCursorPrevLine(1); escReset() }
+            else if (c === 0x47) { ttyCursorX(1); escReset() }
+            else if (c === 0x4A) { ttyEraseInDisp(0); escReset() }
+            else if (c === 0x4B) { escReset() }                    // eraseInLine: no-op
+            else if (c === 0x53) { scrollBufUp(1); escReset() }    // S
+            else if (c === 0x54) { escReset() }                    // T scrollDown: no-op
+            else if (c === 0x6D) { ttySgr1(0); escReset() }        // m
+            else if (c === 0x3F) escState = 8                      // '?'
+            else if (c === 0x3B) { escArgs.push(0); escState = 4 } // ';'
+            else if (isDig(c)) { escArgs.push(c - 0x30); escState = 3 }
+            else escRejectPrint(c)
+            break
+        case 3: // NUM1
+            if (c === 0x41) { ttyCursorUp(escArgs.pop()); escReset() }
+            else if (c === 0x42) { ttyCursorDown(escArgs.pop()); escReset() }
+            else if (c === 0x43) { ttyCursorFwd(escArgs.pop()); escReset() }
+            else if (c === 0x44) { ttyCursorBack(escArgs.pop()); escReset() }
+            else if (c === 0x45) { ttyCursorNextLine(escArgs.pop()); escReset() }
+            else if (c === 0x46) { ttyCursorPrevLine(escArgs.pop()); escReset() }
+            else if (c === 0x47) { ttyCursorX(escArgs.pop()); escReset() }
+            else if (c === 0x4A) { ttyEraseInDisp(escArgs.pop()); escReset() }
+            else if (c === 0x4B) { escArgs.pop(); escReset() }
+            else if (c === 0x53) { scrollBufUp(escArgs.pop()); escReset() }
+            else if (c === 0x54) { escArgs.pop(); escReset() }
+            else if (c === 0x6D) { ttySgr1(escArgs.pop()); escReset() }
+            else if (c === 0x3B) escState = 4
+            else if (isDig(c)) escArgs.push(escArgs.pop() * 10 + (c - 0x30))
+            else escRejectPrint(c)
+            break
+        case 4: // SEP1 (seen "n;")
+            if (isDig(c)) { escArgs.push(c - 0x30); escState = 5 }
+            else if (c === 0x48) { let a1 = escArgs.pop(); ttyCursorXY(a1, 0); escReset() }   // H
+            else if (c === 0x6D) { ttySgr1(escArgs.pop()); escReset() }                       // m (2-arg unimpl in HW)
+            else if (c === 0x3B) { escArgs.push(0); escState = 6 }
+            else escRejectPrint(c)
+            break
+        case 5: // NUM2 (seen "n;n")
+            if (isDig(c)) escArgs.push(escArgs.pop() * 10 + (c - 0x30))
+            else if (c === 0x48) { let a2 = escArgs.pop(), a1 = escArgs.pop(); ttyCursorXY(a1, a2); escReset() }
+            else if (c === 0x6D) { escArgs.pop(); escArgs.pop(); escReset() }  // 2-arg SGR unimpl in HW
+            else if (c === 0x3B) escState = 6
+            else escRejectPrint(c)
+            break
+        case 6: // SEP2 (seen "n;n;")
+            if (c === 0x6D) { let a2 = escArgs.pop(), a1 = escArgs.pop(); ttySgr3(a1, a2, 0); escReset() }
+            else if (isDig(c)) { escArgs.push(c - 0x30); escState = 7 }
+            else escRejectPrint(c)
+            break
+        case 7: // NUM3 (seen "n;n;n")
+            if (isDig(c)) escArgs.push(escArgs.pop() * 10 + (c - 0x30))
+            else if (c === 0x6D) { let a3 = escArgs.pop(), a2 = escArgs.pop(), a1 = escArgs.pop(); ttySgr3(a1, a2, a3); escReset() }
+            else escRejectPrint(c)
+            break
+        case 8: // PRIVATESEQ (seen "?")
+            if (isDig(c)) { escArgs.push(c - 0x30); escState = 9 }
+            else escRejectPrint(c)
+            break
+        case 9: // PRIVATENUM (seen "?n")
+            if (c === 0x68) { ttyPrivH(escArgs.pop()); escReset() }       // h
+            else if (c === 0x6C) { ttyPrivL(escArgs.pop()); escReset() }  // l
+            else if (isDig(c)) escArgs.push(escArgs.pop() * 10 + (c - 0x30))
+            else escRejectPrint(c)
+            break
+        case 10: // XCSI (seen \\x84)
+            if (c === 0x75) { ttyEmitChar(0); escReset() }                // 'u'
+            else if (isDig(c)) { escArgs.push(c - 0x30); escState = 11 }
+            else escRejectPrint(c)
+            break
+        case 11: // XNUM1 (seen \\x84<digits>)
+            if (c === 0x75) { ttyEmitChar(escArgs.pop()); escReset() }     // 'u'
+            else if (isDig(c)) escArgs.push(escArgs.pop() * 10 + (c - 0x30))
+            else escRejectPrint(c)
+            break
+    }
+}
+
+print = function(s) {
+    if (s === undefined || s === null) return
+    let str = '' + s
+    for (let i = 0; i < str.length; i++) processByte(str.charCodeAt(i))
+}
+println = function(s) {
+    if (s === undefined) print("\\n")
+    else print(s + "\\n")
+}
+printerr = function(s) { print(s) }
+printerrln = function(s) { println(s) }
+
+// command.js's shell.execute reassigns the global print/println/printerr/
+// printerrln to shell.stdio.out.* (which call sys.print → physical GPU,
+// bypassing these shims). Expose the buffer writers through a global hook so
+// shell.stdio.out can delegate to them when running inside a VT pane. The
+// non-VT path in command.js stays unchanged (hook is undefined there).
+globalThis.__VT_OUT = { print: print, println: println, printerr: printerr, printerrln: printerrln }
+
+// con.move / con.getyx are 1-based in TVDOS (graphics.setCursorYX does cx-1,
+// getCursorYX returns cx+1). Internal curX/curY are 0-based, so convert.
+con.move = function(y, x) {
+    curY = Math.max(0, Math.min(ROWS - 1, (y | 0) - 1))
+    curX = Math.max(0, Math.min(COLS - 1, (x | 0) - 1))
+    writeCursor()
+}
+con.getyx = function() { return [curY + 1, curX + 1] }
+con.getmaxyx = function() { return [ROWS, COLS] }
+con.color_pair = function(f, b) { foreCol = f & 0xFF; backCol = b & 0xFF }
+con.color_fore = function(n) { foreCol = n & 0xFF }
+con.color_back = function(n) { backCol = n & 0xFF }
+con.get_color_fore = function() { return foreCol }
+con.get_color_back = function() { return backCol }
+// addch writes a glyph at the cursor WITHOUT advancing — matching
+// graphics.putSymbol(). TVDOS code pairs addch with explicit curs_right();
+// advancing here would double-step and leave gaps (e.g. the fancy prompt).
+con.addch = function(c) { putCharRaw(curX, curY, c) }
+con.mvaddch = function(y, x, c) { con.move(y, x); con.addch(c) }
+con.curs_up = function(n) { n = n || 1; curY = Math.max(0, curY - n); writeCursor() }
+con.curs_down = function(n) { n = n || 1; curY = Math.min(ROWS - 1, curY + n); writeCursor() }
+con.curs_left = function(n) { n = n || 1; curX = Math.max(0, curX - n); writeCursor() }
+con.curs_right = function(n) { n = n || 1; curX = Math.min(COLS - 1, curX + n); writeCursor() }
+con.curs_set = function(arg) { sys.poke(CURSOR_VIS_ADDR, ((arg | 0) === 0) ? 0 : 1) }
+con.video_reverse = function() { /* unsupported; ANSI swallowed */ }
+con.reset_graphics = function() { foreCol = 254; backCol = 255 }
+con.clear = function() {
+    for (let i = 0; i < COLS * ROWS; i++) {
+        sys.poke(TP + TEXT_BASE + i, 0)
+        sys.poke(TP + FORE_BASE + i, foreCol)
+        sys.poke(TP + BACK_BASE + i, backCol)
+    }
+    curX = 0; curY = 0; writeCursor()
+}
+// prnch prints a glyph and DOES advance (unlike addch) — the real impl emits
+// it through print() as \\x84<code>u, so route it through the interpreter.
+con.prnch = function(c) {
+    if (Array.isArray(c)) c.forEach(x => ttyEmitChar(x))
+    else ttyEmitChar(c)
+}
+
+// ── input shims ──────────────────────────────────────────────────────────
+// Pane reads from its own ring buffer in shared mem. NEVER touches physical
+// keyboard MMIO — that's the dispatcher's exclusive territory. Cooperative
+// gate on active_vt keeps background panes parked when they call getch.
+
+function queuePop() {
+    let head = sys.peek(QUEUE_HEAD_ADDR)
+    let tail = sys.peek(QUEUE_TAIL_ADDR)
+    if (head === tail) return -1
+    let b = sys.peek(QUEUE_DATA + head)
+    sys.poke(QUEUE_HEAD_ADDR, (head + 1) & 0xFF)
+    return b
+}
+con.getch = function() {
+    while (true) {
+        if (sys.peek(ACTIVE_VT_ADDR) === VT_NUM) {
+            let k = queuePop()
+            if (k >= 0) return k
+        }
+        sys.sleep(20)
+    }
+}
+con.hitterminate = function() { return false }
+con.hiteof = function() { return false }
+con.resetkeybuf = function() { sys.poke(QUEUE_HEAD_ADDR, sys.peek(QUEUE_TAIL_ADDR)) }
+con.poll_keys = function() { return [0,0,0,0,0,0,0,0] }
+
+// ── TVDOS.SYS init flags + BIOS stub ───────────────────────────────────────
+globalThis._TVDOS_IS_VT_PANE = true
+globalThis._BIOS = { FIRST_BOOTABLE_PORT: ${BIOS_FIRST_BOOTABLE_PORT} }
+
+// ── load TVDOS.SYS and run AUTOEXEC.BAT (the per-console shell) in one direct-eval ─────
+// Strict-mode direct eval is scope-isolated, so TVDOS.SYS's \`const _TVDOS\`
+// only survives within the eval scope. The shell launcher must run inside
+// the same eval to access it (via lexical closure into nested evals).
+eval(${JSON.stringify(combined)})
+`
+    // The outer execApp's injectIntChk rewrote the first while/for/do (each
+    // kind) in our literal source to call a per-exec SIGTERM check function.
+    // Some of those rewrites landed inside this template literal — the pane
+    // has no such symbol in scope. Strip them; panes don't need SIGTERM
+    // checks (parallel.kill handles teardown).
+    return raw.replace(/tvdosSIGTERM_[A-Za-z0-9_]+\(\);?/g, '')
+}
+
+// ─── pane lifecycle ─────────────────────────────────────────────────────────
+// Lazy spawn: VT 1 at boot; VT 2-6 the first time the user requests them.
+// Re-spawn if the previous pane's thread has died (e.g. user typed `exit`).
+
+const panes = {}  // n -> { runner, thread }
+
+function isPaneAlive(n) {
+    return panes[n] && parallel.isRunning(panes[n].thread)
+}
+
+function spawnPane(n) {
+    serial.println("[vtmgr] spawning VT " + n)
+    let runner = parallel.spawnNewContext()
+    let thread = parallel.attachProgram("vt" + n, runner, makePaneBootstrap(n))
+    parallel.launch(thread)
+    panes[n] = { runner: runner, thread: thread }
+    sys.poke(CTRL + CTRL_SPAWNED_BITS, sys.peek(CTRL + CTRL_SPAWNED_BITS) | (1 << (n - 1)))
+}
+
+function ensurePane(n) {
+    if (!isPaneAlive(n)) {
+        sys.poke(CTRL + CTRL_SPAWNED_BITS, sys.peek(CTRL + CTRL_SPAWNED_BITS) & ~(1 << (n - 1)))
+        spawnPane(n)
+    }
+}
+
+ensurePane(1)
+sys.poke(CTRL + CTRL_ACTIVE_VT, 1)
+// VT 1's TVDOS.SYS eval is slow; give it room before we start compositing.
+sys.sleep(800)
+
+// ─── compositor / dispatcher loop ───────────────────────────────────────────
+// 30 Hz: blit active pane → GPU text area; honour switch_request; detect
+// Alt-N with debounce; drain typed chars into active pane's queue.
+
+const gpuBase = graphics.getGpuMemBase()
+const TEXTAREA_BASE_ABS = gpuBase - GPU_TEXTAREA_OFFSET
+function blitVt(srcAddr) {
+    sys.memcpy(srcAddr, TEXTAREA_BASE_ABS, TEXT_PLANE_SIZE - 2)
+    sys.poke(TEXTAREA_BASE_ABS - (TEXT_PLANE_SIZE - 2), sys.peek(srcAddr + TEXT_PLANE_SIZE - 2))
+    sys.poke(TEXTAREA_BASE_ABS - (TEXT_PLANE_SIZE - 1), sys.peek(srcAddr + TEXT_PLANE_SIZE - 1))
+}
+
+// GPU textmode-attribute MMIO byte (offset 6): bit 0 = blinkCursor, bit 1 =
+// rawMode, bits 4-7 = chrrom. We flip only bit 0 to match the active pane's
+// cursor visibility. getGpuMemBase() = -1 - 1MB*slot; the peripheral's MMIO
+// window sits at IOSpace offset 128KB*slot, so MMIO byte k = -1 - (128KB*slot + k).
+const gpuSlot = (((-gpuBase) - 1) / 1048576) | 0
+const GPU_MMIO_ATTR = -1 - (131072 * gpuSlot + 6)
+let lastCursorVis = -1
+function applyCursorVis(active) {
+    let vis = sys.peek(vtBlockAddr(active) + 2)
+    if (vis === lastCursorVis) return
+    let attr = sys.peek(GPU_MMIO_ATTR)
+    sys.poke(GPU_MMIO_ATTR, vis ? (attr | 1) : (attr & 0xFE))
+    lastCursorVis = vis
+}
+
+function queuePush(vtN, byte) {
+    let qBase = vtBlockAddr(vtN)
+    let head = sys.peek(qBase + 8)
+    let tail = sys.peek(qBase + 9)
+    let next = (tail + 1) & 0xFF
+    if (next === head) return false
+    sys.poke(qBase + QUEUE_DATA_OFFSET + tail, byte)
+    sys.poke(qBase + 9, next)
+    return true
+}
+
+function switchTo(n) {
+    if (n < 1 || n > MAX_VT) return
+    ensurePane(n)
+    sys.poke(CTRL + CTRL_ACTIVE_VT, n)
+}
+
+sys.poke(-39, 1)  // enable physical keyboard input collection
+
+let running = true
+while (running) {
+    let active = sys.peek(CTRL + CTRL_ACTIVE_VT)
+    if (active < 1 || active > MAX_VT) active = 1
+    blitVt(vtTextPlaneAddr(active))
+    applyCursorVis(active)
+
+    // honour chvt's switch request
+    let req = sys.peek(CTRL + CTRL_SWITCH_REQUEST)
+    if (req >= 1 && req <= MAX_VT) {
+        if (req !== active) {
+            serial.println("[vtmgr] chvt switch -> VT " + req)
+            switchTo(req)
+        }
+        sys.poke(CTRL + CTRL_SWITCH_REQUEST, 0)
+    }
+
+    // Alt-N (and Alt-0 = exit) detection
+    sys.poke(-40, 1)
+    let keys = [sys.peek(-41), sys.peek(-42), sys.peek(-43), sys.peek(-44),
+                sys.peek(-45), sys.peek(-46), sys.peek(-47), sys.peek(-48)]
+    let altHeld = keys.indexOf(57) >= 0 || keys.indexOf(58) >= 0
+    let digit = -1
+    for (let n = 0; n <= MAX_VT; n++) {
+        if (keys.indexOf(7 + n) >= 0) { digit = n; break }
+    }
+    let debounce = sys.peek(CTRL + CTRL_DEBOUNCE_HELD) !== 0
+
+    if (debounce) {
+        if (!altHeld && digit < 0) sys.poke(CTRL + CTRL_DEBOUNCE_HELD, 0)
+    }
+    else if (altHeld && digit === 0) {
+        serial.println("[vtmgr] Alt-0 -> exit")
+        running = false
+        sys.poke(CTRL + CTRL_DEBOUNCE_HELD, 1)
+        sys.poke(-39, 1)
+    }
+    else if (altHeld && digit >= 1) {
+        serial.println("[vtmgr] Alt-" + digit + " -> switching to VT " + digit)
+        switchTo(digit)
+        sys.poke(CTRL + CTRL_DEBOUNCE_HELD, 1)
+        sys.poke(-39, 1)  // swallow the digit char so it doesn't leak into the queue
+    }
+
+    if (!running) break
+
+    // drain typed chars into the active pane's queue
+    while (sys.peek(-50) !== 0) {
+        let k = sys.peek(-38)
+        if (k < 0) k += 256
+        queuePush(active, k)
+    }
+
+    sys.sleep(33)
+}
+
+for (let n = 1; n <= MAX_VT; n++) if (panes[n]) parallel.kill(panes[n].thread)
+con.color_pair(254, 255)
+con.clear()
+println("vtmgr exited.")
+return 0