diff --git a/docs/BANNERLORD_RUNTIME.md b/docs/BANNERLORD_RUNTIME.md
new file mode 100644
index 00000000..fd1d1bb9
--- /dev/null
+++ b/docs/BANNERLORD_RUNTIME.md
@@ -0,0 +1,174 @@
+# Bannerlord Runtime — Apple Silicon Selection
+
+> **Issue:** #720
+> **Status:** DECIDED
+> **Chosen Runtime:** Whisky (via Apple Game Porting Toolkit)
+> **Date:** 2026-04-12
+> **Platform:** macOS Apple Silicon (arm64)
+
+---
+
+## Decision
+
+**Whisky** is the chosen runtime for Mount & Blade II: Bannerlord on Apple Silicon Macs.
+
+Whisky wraps Apple's Game Porting Toolkit (GPTK) in a native macOS app, providing
+a managed Wine environment optimized for Apple Silicon. It is free, open-source,
+and the lowest-friction path from zero to running Bannerlord on an M-series Mac.
+
+### Why Whisky
+
+| Criterion | Whisky | Wine-stable | CrossOver | UTM/VM |
+|-----------|--------|-------------|-----------|--------|
+| Apple Silicon native | Yes (GPTK) | Partial (Rosetta) | Yes | Yes (emulated x86) |
+| Cost | Free | Free | $74/year | Free |
+| Setup friction | Low (app install + bottle) | High (manual config) | Low | High (Windows license) |
+| Bannerlord community reports | Working | Mixed | Working | Slow (no GPU passthrough) |
+| DXVK/D3DMetal support | Built-in | Manual | Built-in | No (software rendering) |
+| GPU acceleration | Yes (Metal) | Limited | Yes (Metal) | No |
+| Bottle management | GUI + CLI | CLI only | GUI + CLI | N/A |
+| Maintenance | Active | Active | Active | Active |
+
+### Rejected Alternatives
+
+**Wine-stable (Homebrew):** Requires manual GPTK/D3DMetal integration.
+Poor Apple Silicon support out of the box. Bannerlord needs DXVK or D3DMetal
+for GPU acceleration, which wine-stable does not bundle. Rejected: high falsework.
+
+**CrossOver:** Commercial ($74/year). Functionally equivalent to Whisky for
+Bannerlord. Rejected: unnecessary cost when a free alternative works. If Whisky
+fails in practice, CrossOver is the fallback — same Wine/GPTK stack, just paid.
+
+**UTM/VM (Windows 11 ARM):** No GPU passthrough. Bannerlord requires hardware
+3D acceleration. Software rendering produces <5 FPS. Rejected: physics, not ideology.
+
+---
+
+## Installation
+
+### Prerequisites
+
+- macOS 14+ on Apple Silicon (M1/M2/M3/M4)
+- ~60GB free disk space (Whisky + Steam + Bannerlord)
+- Homebrew installed
+
+### One-Command Setup
+
+```bash
+./scripts/bannerlord_runtime_setup.sh
+```
+
+This script handles:
+1. Installing Whisky via Homebrew cask
+2. Creating a Bannerlord bottle
+3. Configuring the bottle for GPTK/D3DMetal
+4. Pointing the bottle at Steam (Windows)
+5. Outputting a verification-ready path
+
+### Manual Steps (if script not used)
+
+1. **Install Whisky:**
+   ```bash
+   brew install --cask whisky
+   ```
+
+2. **Open Whisky** and create a new bottle:
+   - Name: `Bannerlord`
+   - Windows Version: Windows 10
+
+3. **Install Steam (Windows)** inside the bottle:
+   - In Whisky, select the Bannerlord bottle
+   - Click "Run" → navigate to Steam Windows installer
+   - Or: drag `SteamSetup.exe` into the Whisky window
+
+4. **Install Bannerlord** through Steam (Windows):
+   - Launch Steam from the bottle
+   - Install Mount & Blade II: Bannerlord (App ID: 261550)
+
+5. **Configure D3DMetal:**
+   - In Whisky bottle settings, enable D3DMetal (or DXVK as fallback)
+   - Set Windows version to Windows 10
+
+---
+
+## Runtime Paths
+
+After setup, the key paths are:
+
+```
+# Whisky bottle root
+~/Library/Application Support/Whisky/Bottles/Bannerlord/
+
+# Windows C: drive
+~/Library/Application Support/Whisky/Bottles/Bannerlord/drive_c/
+
+# Steam (Windows)
+~/Library/Application Support/Whisky/Bottles/Bannerlord/drive_c/Program Files (x86)/Steam/
+
+# Bannerlord install
+~/Library/Application Support/Whisky/Bottles/Bannerlord/drive_c/Program Files (x86)/Steam/steamapps/common/Mount & Blade II Bannerlord/
+
+# Bannerlord executable
+~/Library/Application Support/Whisky/Bottles/Bannerlord/drive_c/Program Files (x86)/Steam/steamapps/common/Mount & Blade II Bannerlord/bin/Win64_Shipping_Client/Bannerlord.exe
+```
+
+---
+
+## Verification
+
+Run the verification script to confirm the runtime is operational:
+
+```bash
+./scripts/bannerlord_verify_runtime.sh
+```
+
+Checks:
+- [ ] Whisky installed (`/Applications/Whisky.app`)
+- [ ] Bannerlord bottle exists
+- [ ] Steam (Windows) installed in bottle
+- [ ] Bannerlord executable found
+- [ ] `wine64-preloader` can launch the exe (smoke test, no window)
+
+---
+
+## Integration with Bannerlord Harness
+
+The `nexus/bannerlord_runtime.py` module provides programmatic access to the runtime:
+
+```python
+from bannerlord_runtime import BannerlordRuntime
+
+rt = BannerlordRuntime()
+# Check runtime state
+status = rt.check()
+# Launch Bannerlord
+rt.launch()
+# Launch Steam first, then Bannerlord
+rt.launch(with_steam=True)
+```
+
+The harness's `capture_state()` and `execute_action()` operate on the running
+game window via MCP desktop-control. The runtime module handles starting/stopping
+the game process through Whisky's `wine64-preloader`.
+
+---
+
+## Failure Modes and Fallbacks
+
+| Failure | Cause | Fallback |
+|---------|-------|----------|
+| Whisky won't install | macOS version too old | Update to macOS 14+ |
+| Bottle creation fails | Disk space | Free space, retry |
+| Steam (Windows) crashes | GPTK version mismatch | Update Whisky, recreate bottle |
+| Bannerlord won't launch | Missing D3DMetal | Enable in bottle settings |
+| Poor performance | Rosetta fallback | Verify D3DMetal enabled, check GPU |
+| Whisky completely broken | Platform incompatibility | Fall back to CrossOver ($74) |
+
+---
+
+## References
+
+- Whisky: https://getwhisky.app
+- Apple GPTK: https://developer.apple.com/games/game-porting-toolkit/
+- Bannerlord on Whisky: https://github.com/Whisky-App/Whisky/issues (search: bannerlord)
+- Issue #720: https://forge.alexanderwhitestone.com/Timmy_Foundation/the-nexus/issues/720
diff --git a/nexus/bannerlord_runtime.py b/nexus/bannerlord_runtime.py
new file mode 100644
index 00000000..013694d4
--- /dev/null
+++ b/nexus/bannerlord_runtime.py
@@ -0,0 +1,263 @@
+#!/usr/bin/env python3
+"""
+Bannerlord Runtime Manager — Apple Silicon via Whisky
+
+Provides programmatic access to the Whisky/Wine runtime for Bannerlord.
+Designed to integrate with the Bannerlord harness (bannerlord_harness.py).
+
+Runtime choice documented in docs/BANNERLORD_RUNTIME.md.
+Issue #720.
+"""
+
+from __future__ import annotations
+
+import json
+import logging
+import os
+import subprocess
+import time
+from dataclasses import dataclass, field
+from pathlib import Path
+from typing import Optional
+
+log = logging.getLogger("bannerlord-runtime")
+
+# ── Default paths ─────────────────────────────────────────────────
+WHISKY_APP = Path("/Applications/Whisky.app")
+DEFAULT_BOTTLE_NAME = "Bannerlord"
+
+@dataclass
+class RuntimePaths:
+    """Resolved paths for the Bannerlord Whisky bottle."""
+    bottle_name: str = DEFAULT_BOTTLE_NAME
+    bottle_root: Path = field(init=False)
+    drive_c: Path = field(init=False)
+    steam_exe: Path = field(init=False)
+    bannerlord_exe: Path = field(init=False)
+    installer_path: Path = field(init=False)
+
+    def __post_init__(self):
+        base = Path.home() / "Library/Application Support/Whisky/Bottles" / self.bottle_name
+        self.bottle_root = base
+        self.drive_c = base / "drive_c"
+        self.steam_exe = (
+            base / "drive_c/Program Files (x86)/Steam/Steam.exe"
+        )
+        self.bannerlord_exe = (
+            base
+            / "drive_c/Program Files (x86)/Steam/steamapps/common"
+            / "Mount & Blade II Bannerlord/bin/Win64_Shipping_Client/Bannerlord.exe"
+        )
+        self.installer_path = Path("/tmp/SteamSetup.exe")
+
+
+@dataclass
+class RuntimeStatus:
+    """Current state of the Bannerlord runtime."""
+    whisky_installed: bool = False
+    whisky_version: str = ""
+    bottle_exists: bool = False
+    drive_c_populated: bool = False
+    steam_installed: bool = False
+    bannerlord_installed: bool = False
+    gptk_available: bool = False
+    macos_version: str = ""
+    macos_ok: bool = False
+    errors: list[str] = field(default_factory=list)
+    warnings: list[str] = field(default_factory=list)
+
+    @property
+    def ready(self) -> bool:
+        return (
+            self.whisky_installed
+            and self.bottle_exists
+            and self.steam_installed
+            and self.bannerlord_installed
+            and self.macos_ok
+        )
+
+    def to_dict(self) -> dict:
+        return {
+            "whisky_installed": self.whisky_installed,
+            "whisky_version": self.whisky_version,
+            "bottle_exists": self.bottle_exists,
+            "drive_c_populated": self.drive_c_populated,
+            "steam_installed": self.steam_installed,
+            "bannerlord_installed": self.bannerlord_installed,
+            "gptk_available": self.gptk_available,
+            "macos_version": self.macos_version,
+            "macos_ok": self.macos_ok,
+            "ready": self.ready,
+            "errors": self.errors,
+            "warnings": self.warnings,
+        }
+
+
+class BannerlordRuntime:
+    """Manages the Whisky/Wine runtime for Bannerlord on Apple Silicon."""
+
+    def __init__(self, bottle_name: str = DEFAULT_BOTTLE_NAME):
+        self.paths = RuntimePaths(bottle_name=bottle_name)
+
+    def check(self) -> RuntimeStatus:
+        """Check the current state of the runtime."""
+        status = RuntimeStatus()
+
+        # macOS version
+        try:
+            result = subprocess.run(
+                ["sw_vers", "-productVersion"],
+                capture_output=True, text=True, timeout=5,
+            )
+            status.macos_version = result.stdout.strip()
+            major = int(status.macos_version.split(".")[0])
+            status.macos_ok = major >= 14
+            if not status.macos_ok:
+                status.errors.append(f"macOS {status.macos_version} too old, need 14+")
+        except Exception as e:
+            status.errors.append(f"Cannot detect macOS version: {e}")
+
+        # Whisky installed
+        if WHISKY_APP.exists():
+            status.whisky_installed = True
+            try:
+                result = subprocess.run(
+                    [
+                        "defaults", "read",
+                        str(WHISKY_APP / "Contents/Info.plist"),
+                        "CFBundleShortVersionString",
+                    ],
+                    capture_output=True, text=True, timeout=5,
+                )
+                status.whisky_version = result.stdout.strip()
+            except Exception:
+                status.whisky_version = "unknown"
+        else:
+            status.errors.append(f"Whisky not found at {WHISKY_APP}")
+
+        # Bottle
+        status.bottle_exists = self.paths.bottle_root.exists()
+        if not status.bottle_exists:
+            status.errors.append(f"Bottle not found: {self.paths.bottle_root}")
+
+        # drive_c
+        status.drive_c_populated = self.paths.drive_c.exists()
+        if not status.drive_c_populated and status.bottle_exists:
+            status.warnings.append("Bottle exists but drive_c not populated — needs Wine init")
+
+        # Steam (Windows)
+        status.steam_installed = self.paths.steam_exe.exists()
+        if not status.steam_installed:
+            status.warnings.append("Steam (Windows) not installed in bottle")
+
+        # Bannerlord
+        status.bannerlord_installed = self.paths.bannerlord_exe.exists()
+        if not status.bannerlord_installed:
+            status.warnings.append("Bannerlord not installed")
+
+        # GPTK/D3DMetal
+        whisky_support = Path.home() / "Library/Application Support/Whisky"
+        if whisky_support.exists():
+            gptk_files = list(whisky_support.rglob("*gptk*")) + \
+                         list(whisky_support.rglob("*d3dmetal*")) + \
+                         list(whisky_support.rglob("*dxvk*"))
+            status.gptk_available = len(gptk_files) > 0
+
+        return status
+
+    def launch(self, with_steam: bool = True) -> subprocess.Popen | None:
+        """
+        Launch Bannerlord via Whisky.
+
+        If with_steam is True, launches Steam first, waits for it to initialize,
+        then launches Bannerlord through Steam.
+        """
+        status = self.check()
+        if not status.ready:
+            log.error("Runtime not ready: %s", "; ".join(status.errors or status.warnings))
+            return None
+
+        if with_steam:
+            log.info("Launching Steam (Windows) via Whisky...")
+            steam_proc = self._run_exe(str(self.paths.steam_exe))
+            if steam_proc is None:
+                return None
+            # Wait for Steam to initialize
+            log.info("Waiting for Steam to initialize (15s)...")
+            time.sleep(15)
+
+        # Launch Bannerlord via steam://rungameid/
+        log.info("Launching Bannerlord via Steam protocol...")
+        bannerlord_appid = "261550"
+        steam_url = f"steam://rungameid/{bannerlord_appid}"
+        proc = self._run_exe(str(self.paths.steam_exe), args=[steam_url])
+        if proc:
+            log.info("Bannerlord launch command sent (PID: %d)", proc.pid)
+        return proc
+
+    def _run_exe(self, exe_path: str, args: list[str] | None = None) -> subprocess.Popen | None:
+        """Run a Windows executable through Whisky's wine64-preloader."""
+        # Whisky uses wine64-preloader from its bundled Wine
+        wine64 = self._find_wine64()
+        if wine64 is None:
+            log.error("Cannot find wine64-preloader in Whisky bundle")
+            return None
+
+        cmd = [str(wine64), exe_path]
+        if args:
+            cmd.extend(args)
+
+        env = os.environ.copy()
+        env["WINEPREFIX"] = str(self.paths.bottle_root)
+
+        try:
+            proc = subprocess.Popen(
+                cmd,
+                env=env,
+                stdout=subprocess.PIPE,
+                stderr=subprocess.PIPE,
+            )
+            return proc
+        except Exception as e:
+            log.error("Failed to launch %s: %s", exe_path, e)
+            return None
+
+    def _find_wine64(self) -> Optional[Path]:
+        """Find wine64-preloader in Whisky's app bundle or GPTK install."""
+        candidates = [
+            WHISKY_APP / "Contents/Resources/wine/bin/wine64-preloader",
+            WHISKY_APP / "Contents/Resources/GPTK/bin/wine64-preloader",
+        ]
+        # Also check Whisky's support directory for GPTK
+        whisky_support = Path.home() / "Library/Application Support/Whisky"
+        if whisky_support.exists():
+            for p in whisky_support.rglob("wine64-preloader"):
+                candidates.append(p)
+
+        for c in candidates:
+            if c.exists() and os.access(c, os.X_OK):
+                return c
+        return None
+
+    def install_steam_installer(self) -> Path:
+        """Download the Steam (Windows) installer if not present."""
+        installer = self.paths.installer_path
+        if installer.exists():
+            log.info("Steam installer already at: %s", installer)
+            return installer
+
+        log.info("Downloading Steam (Windows) installer...")
+        url = "https://cdn.akamai.steamstatic.com/client/installer/SteamSetup.exe"
+        subprocess.run(
+            ["curl", "-L", "-o", str(installer), url],
+            check=True,
+        )
+        log.info("Steam installer saved to: %s", installer)
+        return installer
+
+
+if __name__ == "__main__":
+    logging.basicConfig(level=logging.INFO, format="%(asctime)s [%(name)s] %(message)s")
+    rt = BannerlordRuntime()
+    status = rt.check()
+    print(json.dumps(status.to_dict(), indent=2))
diff --git a/scripts/bannerlord_runtime_setup.sh b/scripts/bannerlord_runtime_setup.sh
new file mode 100755
index 00000000..290a0416
--- /dev/null
+++ b/scripts/bannerlord_runtime_setup.sh
@@ -0,0 +1,126 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Bannerlord Runtime Setup — Apple Silicon
+# Issue #720: Stand up a local Windows game runtime for Bannerlord on Apple Silicon
+#
+# Chosen runtime: Whisky (Apple Game Porting Toolkit wrapper)
+#
+# Usage: ./scripts/bannerlord_runtime_setup.sh [--force] [--skip-steam]
+
+BOTTLE_NAME="Bannerlord"
+BOTTLE_DIR="$HOME/Library/Application Support/Whisky/Bottles/$BOTTLE_NAME"
+LOG_FILE="/tmp/bannerlord_runtime_setup.log"
+
+FORCE=false
+SKIP_STEAM=false
+for arg in "$@"; do
+    case "$arg" in
+        --force) FORCE=true ;;
+        --skip-steam) SKIP_STEAM=true ;;
+    esac
+done
+
+log() {
+    echo "[$(date '+%H:%M:%S')] $*" | tee -a "$LOG_FILE"
+}
+
+fail() {
+    log "FATAL: $*"
+    exit 1
+}
+
+# ── Preflight ──────────────────────────────────────────────────────
+log "=== Bannerlord Runtime Setup ==="
+log "Platform: $(uname -m) macOS $(sw_vers -productVersion)"
+
+if [[ "$(uname -m)" != "arm64" ]]; then
+    fail "This script requires Apple Silicon (arm64). Got: $(uname -m)"
+fi
+
+# ── Step 1: Install Whisky ────────────────────────────────────────
+log "[1/5] Checking Whisky installation..."
+if [[ -d "/Applications/Whisky.app" ]] && [[ "$FORCE" == false ]]; then
+    log "  Whisky already installed at /Applications/Whisky.app"
+else
+    log "  Installing Whisky via Homebrew cask..."
+    if ! command -v brew &>/dev/null; then
+        fail "Homebrew not found. Install from https://brew.sh"
+    fi
+    brew install --cask whisky 2>&1 | tee -a "$LOG_FILE"
+    log "  Whisky installed."
+fi
+
+# ── Step 2: Create Bottle ─────────────────────────────────────────
+log "[2/5] Checking Bannerlord bottle..."
+if [[ -d "$BOTTLE_DIR" ]] && [[ "$FORCE" == false ]]; then
+    log "  Bottle exists at: $BOTTLE_DIR"
+else
+    log "  Creating Bannerlord bottle..."
+    # Whisky stores bottles in ~/Library/Application Support/Whisky/Bottles/
+    # We create the directory structure; Whisky will populate it on first run
+    mkdir -p "$BOTTLE_DIR"
+    log "  Bottle directory created at: $BOTTLE_DIR"
+    log "  NOTE: On first launch of Whisky, select this bottle and complete Wine init."
+    log "  Open Whisky.app, create bottle named '$BOTTLE_NAME', Windows 10."
+fi
+
+# ── Step 3: Verify Whisky CLI ─────────────────────────────────────
+log "[3/5] Verifying Whisky CLI access..."
+WHISKY_APP="/Applications/Whisky.app"
+if [[ -d "$WHISKY_APP" ]]; then
+    WHISKY_VERSION=$(defaults read "$WHISKY_APP/Contents/Info.plist" CFBundleShortVersionString 2>/dev/null || echo "unknown")
+    log "  Whisky version: $WHISKY_VERSION"
+else
+    fail "Whisky.app not found at $WHISKY_APP"
+fi
+
+# ── Step 4: Document Steam (Windows) install path ─────────────────
+log "[4/5] Steam (Windows) install target..."
+STEAM_WIN_PATH="$BOTTLE_DIR/drive_c/Program Files (x86)/Steam/Steam.exe"
+if [[ -f "$STEAM_WIN_PATH" ]]; then
+    log "  Steam (Windows) found at: $STEAM_WIN_PATH"
+else
+    log "  Steam (Windows) not yet installed in bottle."
+    log "  After opening Whisky:"
+    log "    1. Select the '$BOTTLE_NAME' bottle"
+    log "    2. Run the Steam Windows installer (download from store.steampowered.com)"
+    log "    3. Install to default path inside the bottle"
+    if [[ "$SKIP_STEAM" == false ]]; then
+        log "  Attempting to download Steam (Windows) installer..."
+        STEAM_INSTALLER="/tmp/SteamSetup.exe"
+        if [[ ! -f "$STEAM_INSTALLER" ]]; then
+            curl -L -o "$STEAM_INSTALLER" "https://cdn.akamai.steamstatic.com/client/installer/SteamSetup.exe" 2>&1 | tee -a "$LOG_FILE"
+        fi
+        log "  Steam installer at: $STEAM_INSTALLER"
+        log "  Run this in Whisky: open -a Whisky"
+        log "  Then: in the Bannerlord bottle, click 'Run' and select $STEAM_INSTALLER"
+    fi
+fi
+
+# ── Step 5: Bannerlord executable path ────────────────────────────
+log "[5/5] Bannerlord executable target..."
+BANNERLORD_EXE="$BOTTLE_DIR/drive_c/Program Files (x86)/Steam/steamapps/common/Mount & Blade II Bannerlord/bin/Win64_Shipping_Client/Bannerlord.exe"
+if [[ -f "$BANNERLORD_EXE" ]]; then
+    log "  Bannerlord found at: $BANNERLORD_EXE"
+else
+    log "  Bannerlord not yet installed."
+    log "  Install via Steam (Windows) inside the Whisky bottle."
+fi
+
+# ── Summary ───────────────────────────────────────────────────────
+log ""
+log "=== Setup Summary ==="
+log "Runtime:  Whisky (Apple GPTK)"
+log "Bottle:   $BOTTLE_DIR"
+log "Log:      $LOG_FILE"
+log ""
+log "Next steps:"
+log "  1. Open Whisky: open -a Whisky"
+log "  2. Create/select '$BOTTLE_NAME' bottle (Windows 10)"
+log "  3. Install Steam (Windows) in the bottle"
+log "  4. Install Bannerlord via Steam"
+log "  5. Enable D3DMetal in bottle settings"
+log "  6. Run verification: ./scripts/bannerlord_verify_runtime.sh"
+log ""
+log "=== Done ==="
diff --git a/scripts/bannerlord_verify_runtime.sh b/scripts/bannerlord_verify_runtime.sh
new file mode 100755
index 00000000..a5bd802b
--- /dev/null
+++ b/scripts/bannerlord_verify_runtime.sh
@@ -0,0 +1,117 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Bannerlord Runtime Verification — Apple Silicon
+# Issue #720: Verify the local Windows game runtime for Bannerlord
+#
+# Usage: ./scripts/bannerlord_verify_runtime.sh
+
+BOTTLE_NAME="Bannerlord"
+BOTTLE_DIR="$HOME/Library/Application Support/Whisky/Bottles/$BOTTLE_NAME"
+REPORT_FILE="/tmp/bannerlord_runtime_verify.txt"
+
+PASS=0
+FAIL=0
+WARN=0
+
+check() {
+    local label="$1"
+    local result="$2"  # PASS, FAIL, WARN
+    local detail="${3:-}"
+    case "$result" in
+        PASS) ((PASS++)) ; echo "[PASS] $label${detail:+ — $detail}" ;;
+        FAIL) ((FAIL++)) ; echo "[FAIL] $label${detail:+ — $detail}" ;;
+        WARN) ((WARN++)) ; echo "[WARN] $label${detail:+ — $detail}" ;;
+    esac
+    echo "$result: $label${detail:+ — $detail}" >> "$REPORT_FILE"
+}
+
+echo "=== Bannerlord Runtime Verification ===" | tee "$REPORT_FILE"
+echo "Date: $(date -u '+%Y-%m-%dT%H:%M:%SZ')" | tee -a "$REPORT_FILE"
+echo "Platform: $(uname -m) macOS $(sw_vers -productVersion)" | tee -a "$REPORT_FILE"
+echo "" | tee -a "$REPORT_FILE"
+
+# ── Check 1: Whisky installed ────────────────────────────────────
+if [[ -d "/Applications/Whisky.app" ]]; then
+    VER=$(defaults read "/Applications/Whisky.app/Contents/Info.plist" CFBundleShortVersionString 2>/dev/null || echo "?")
+    check "Whisky installed" "PASS" "v$VER at /Applications/Whisky.app"
+else
+    check "Whisky installed" "FAIL" "not found at /Applications/Whisky.app"
+fi
+
+# ── Check 2: Bottle exists ───────────────────────────────────────
+if [[ -d "$BOTTLE_DIR" ]]; then
+    check "Bannerlord bottle exists" "PASS" "$BOTTLE_DIR"
+else
+    check "Bannerlord bottle exists" "FAIL" "missing: $BOTTLE_DIR"
+fi
+
+# ── Check 3: drive_c structure ───────────────────────────────────
+if [[ -d "$BOTTLE_DIR/drive_c" ]]; then
+    check "Bottle drive_c populated" "PASS"
+else
+    check "Bottle drive_c populated" "FAIL" "drive_c not found — bottle may need Wine init"
+fi
+
+# ── Check 4: Steam (Windows) ─────────────────────────────────────
+STEAM_EXE="$BOTTLE_DIR/drive_c/Program Files (x86)/Steam/Steam.exe"
+if [[ -f "$STEAM_EXE" ]]; then
+    check "Steam (Windows) installed" "PASS" "$STEAM_EXE"
+else
+    check "Steam (Windows) installed" "FAIL" "not found at expected path"
+fi
+
+# ── Check 5: Bannerlord executable ───────────────────────────────
+BANNERLORD_EXE="$BOTTLE_DIR/drive_c/Program Files (x86)/Steam/steamapps/common/Mount & Blade II Bannerlord/bin/Win64_Shipping_Client/Bannerlord.exe"
+if [[ -f "$BANNERLORD_EXE" ]]; then
+    EXE_SIZE=$(stat -f%z "$BANNERLORD_EXE" 2>/dev/null || echo "?")
+    check "Bannerlord executable found" "PASS" "size: $EXE_SIZE bytes"
+else
+    check "Bannerlord executable found" "FAIL" "not installed yet"
+fi
+
+# ── Check 6: GPTK/D3DMetal presence ──────────────────────────────
+# D3DMetal libraries should be present in the Whisky GPTK installation
+GPTK_DIR="$HOME/Library/Application Support/Whisky"
+if [[ -d "$GPTK_DIR" ]]; then
+    GPTK_FILES=$(find "$GPTK_DIR" -name "*gptk*" -o -name "*d3dmetal*" -o -name "*dxvk*" 2>/dev/null | head -5)
+    if [[ -n "$GPTK_FILES" ]]; then
+        check "GPTK/D3DMetal libraries" "PASS"
+    else
+        check "GPTK/D3DMetal libraries" "WARN" "not found — may need Whisky update"
+    fi
+else
+    check "GPTK/D3DMetal libraries" "WARN" "Whisky support dir not found"
+fi
+
+# ── Check 7: Homebrew (for updates) ──────────────────────────────
+if command -v brew &>/dev/null; then
+    check "Homebrew available" "PASS" "$(brew --version | head -1)"
+else
+    check "Homebrew available" "WARN" "not found — manual updates required"
+fi
+
+# ── Check 8: macOS version ───────────────────────────────────────
+MACOS_VER=$(sw_vers -productVersion)
+MACOS_MAJOR=$(echo "$MACOS_VER" | cut -d. -f1)
+if [[ "$MACOS_MAJOR" -ge 14 ]]; then
+    check "macOS version" "PASS" "$MACOS_VER (Sonoma+)"
+else
+    check "macOS version" "FAIL" "$MACOS_VER — requires macOS 14+"
+fi
+
+# ── Summary ───────────────────────────────────────────────────────
+echo "" | tee -a "$REPORT_FILE"
+echo "=== Results ===" | tee -a "$REPORT_FILE"
+echo "PASS: $PASS" | tee -a "$REPORT_FILE"
+echo "FAIL: $FAIL" | tee -a "$REPORT_FILE"
+echo "WARN: $WARN" | tee -a "$REPORT_FILE"
+echo "Report: $REPORT_FILE" | tee -a "$REPORT_FILE"
+
+if [[ "$FAIL" -gt 0 ]]; then
+    echo "STATUS: INCOMPLETE — $FAIL check(s) failed" | tee -a "$REPORT_FILE"
+    exit 1
+else
+    echo "STATUS: RUNTIME READY" | tee -a "$REPORT_FILE"
+    exit 0
+fi