feat(scripts): read-only, allow-listed Files global for site scripts; Delmia test receiver parses recipe files

Script file access (design docs/plans/2026-09-28-script-file-access-design.md): Files.ReadTextAsync /
ReadLinesAsync / ExistsAsync on site ScriptGlobals (+ Instance.Files), backed by the site-singleton
ScriptFileReader. The one host-mediated exception to the System.IO ban - scripts still never name a
System.IO type. OFF by default: ScadaBridge:SiteRuntime:ScriptFileAccess:AllowedRoots (empty = every call
throws Disabled) + MaxFileBytes (1 MiB, validated 1..64 MiB, roots must be absolute). Guard: fully
qualified, no device paths / ADS, canonical path strictly inside a root (directory-boundary match), no
reparse point on the file or any directory below the root, size cap before and during the read.
Errors are one Commons type, ScriptFileAccessException(+ScriptFileAccessFailure); Commons.Types.Scripts
joins the default script imports on every surface so it binds by short name. Mirrored on
ScriptCompileSurface (CompileFiles, parity-pinned) and the Test Run sandbox (binds, refuses Disabled).
Inbound (central) scripts do not get it.

Rig: docker/recipes (sample RecipeValueName,RecipeValue files incl. an invalid one) bind-mounted
read-only at /app/recipes on both site-a nodes with AllowedRoots [/app/recipes]. The TestMesMachine
SimDelmiaRecipe simulator now reads + parses the downloaded file, converts each value to its recipe tag's
type and loads it all-or-nothing (14 new TestDelmiaReceiver attributes); verify-mes-test-machine.sh
group A covers accept / re-download / invalid lines / NotFound / OutsideAllowedRoots, VERIFY_GROUPS
selects groups (rig: AD).

src/ZB.MOM.WW.ScadaBridge.CentralUI/ScriptAnalysis/SandboxScriptHost.cs

@@ -96,6 +96,46 @@ public class SandboxScriptHost
     /// <c>Log</c> and <c>Instance.Log</c> are the same object here too.
     /// </summary>
     public SandboxLog Log => Instance.Log;
+
+    /// <summary>
+    /// Sandbox mirror of the site runtime's <c>Files</c> global (design 2026-09-28), so a script
+    /// that reads a file BINDS in the Test Run editor. The central sandbox has no access to a
+    /// site node's filesystem, so every call throws the same
+    /// <see cref="ScriptFileAccessException"/> (<see cref="ScriptFileAccessFailure.Disabled"/>) a
+    /// site without configured roots throws — a script's own error handling runs as it would there.
+    /// </summary>
+    public SandboxFilesAccessor Files => Instance.Files;
+}
+
+/// <summary>
+/// Sandbox mirror of the SiteRuntime <c>FilesAccessor</c>: binds identically, refuses at run time.
+/// </summary>
+public class SandboxFilesAccessor
+{
+    private const string Message =
+        "Files.* reads the SITE node's filesystem (under ScadaBridge:SiteRuntime:ScriptFileAccess:AllowedRoots), " +
+        "which the central Test Run sandbox cannot reach — deploy to a site to exercise file-reading scripts.";
+
+    /// <summary>Mirrors <c>FilesAccessor.ReadTextAsync</c>; always refused in the sandbox.</summary>
+    /// <param name="path">The file path.</param>
+    /// <param name="cancellationToken">Unused in the sandbox.</param>
+    /// <returns>Never returns.</returns>
+    public Task<string> ReadTextAsync(string path, CancellationToken cancellationToken = default)
+        => throw new ScriptFileAccessException(ScriptFileAccessFailure.Disabled, Message);
+
+    /// <summary>Mirrors <c>FilesAccessor.ReadLinesAsync</c>; always refused in the sandbox.</summary>
+    /// <param name="path">The file path.</param>
+    /// <param name="cancellationToken">Unused in the sandbox.</param>
+    /// <returns>Never returns.</returns>
+    public Task<IReadOnlyList<string>> ReadLinesAsync(string path, CancellationToken cancellationToken = default)
+        => throw new ScriptFileAccessException(ScriptFileAccessFailure.Disabled, Message);
+
+    /// <summary>Mirrors <c>FilesAccessor.ExistsAsync</c>; always refused in the sandbox.</summary>
+    /// <param name="path">The file path.</param>
+    /// <param name="cancellationToken">Unused in the sandbox.</param>
+    /// <returns>Never returns.</returns>
+    public Task<bool> ExistsAsync(string path, CancellationToken cancellationToken = default)
+        => throw new ScriptFileAccessException(ScriptFileAccessFailure.Disabled, Message);
 }
 
 /// <summary>
@@ -263,6 +303,9 @@ public class SandboxInstanceContext
     /// </summary>
     public SandboxLog Log { get; } = new();
 
+    /// <summary>Sandbox mirror of <c>ScriptRuntimeContext.Files</c> (design 2026-09-28); always refuses.</summary>
+    public SandboxFilesAccessor Files { get; } = new();
+
     /// <summary>
     /// Initializes a new instance of the SandboxInstanceContext.
     /// </summary>

src/ZB.MOM.WW.ScadaBridge.CentralUI/ScriptAnalysis/ScriptAnalysisService.cs

@@ -71,7 +71,9 @@ public class ScriptAnalysisService
             "System.Collections.Generic",
             "System.Linq",
             "System.Text",
-            "System.Threading.Tasks");
+            "System.Threading.Tasks",
+            // Mirrors the site runtime's imports (design 2026-09-28).
+            "ZB.MOM.WW.ScadaBridge.Commons.Types.Scripts");
 
     /// <summary>
     /// Options for a sandbox run — <see cref="DefaultOptions"/> plus the sandbox host assembly

src/ZB.MOM.WW.ScadaBridge.Commons/Types/Scripts/ScriptFileAccessException.cs

@@ -0,0 +1,50 @@
+namespace ZB.MOM.WW.ScadaBridge.Commons.Types.Scripts;
+
+/// <summary>
+/// Why a script's <c>Files.*</c> call was refused or failed (design 2026-09-28).
+/// </summary>
+public enum ScriptFileAccessFailure
+{
+    /// <summary>No allowed roots are configured on this node (the default), or the surface has no file access at all (Test Run sandbox).</summary>
+    Disabled,
+
+    /// <summary>The path is empty, relative, a device/alternate-stream path, or otherwise malformed.</summary>
+    InvalidPath,
+
+    /// <summary>The canonical path is not under any configured allowed root.</summary>
+    OutsideAllowedRoots,
+
+    /// <summary>The file, or a directory between the allowed root and the file, is a symbolic link / junction / reparse point.</summary>
+    LinkNotAllowed,
+
+    /// <summary>The file does not exist (or the path names a directory).</summary>
+    NotFound,
+
+    /// <summary>The file is larger than the configured size cap.</summary>
+    TooLarge,
+
+    /// <summary>The operating system refused or failed the read (permissions, sharing violation, I/O error).</summary>
+    IoError,
+}
+
+/// <summary>
+/// The single exception type a script's <c>Files.*</c> calls throw. Scripts cannot name
+/// <c>System.IO</c> exception types (the trust policy forbids the namespace), so every refusal
+/// and every I/O failure is surfaced as this Commons type, which a script can catch by name and
+/// branch on via <see cref="Failure"/>.
+/// </summary>
+public sealed class ScriptFileAccessException : Exception
+{
+    /// <summary>Initializes a new instance.</summary>
+    /// <param name="failure">The failure category.</param>
+    /// <param name="message">A message naming the path and the reason.</param>
+    /// <param name="innerException">The underlying exception, if any.</param>
+    public ScriptFileAccessException(ScriptFileAccessFailure failure, string message, Exception? innerException = null)
+        : base(message, innerException)
+    {
+        Failure = failure;
+    }
+
+    /// <summary>Why the call was refused or failed.</summary>
+    public ScriptFileAccessFailure Failure { get; }
+}

src/ZB.MOM.WW.ScadaBridge.ScriptAnalysis/ScriptCompileSurface.cs

@@ -70,6 +70,9 @@ public sealed class ScriptCompileSurface
     /// <summary>Mirrors <c>ScriptGlobals.Log</c>.</summary>
     public CompileLog Log => throw new NotSupportedException(CompileOnly);
 
+    /// <summary>Mirrors <c>ScriptGlobals.Files</c>.</summary>
+    public CompileFiles Files => throw new NotSupportedException(CompileOnly);
+
     /// <summary>Compile-only mirror of <c>ScriptRuntimeContext</c> (the <c>Instance</c> global).</summary>
     public sealed class CompileInstance
     {
@@ -110,6 +113,37 @@ public sealed class ScriptCompileSurface
 
         /// <summary>Mirrors <c>ScriptRuntimeContext.Log</c>.</summary>
         public CompileLog Log => throw new NotSupportedException(CompileOnly);
+
+        /// <summary>Mirrors <c>ScriptRuntimeContext.Files</c>.</summary>
+        public CompileFiles Files => throw new NotSupportedException(CompileOnly);
+    }
+
+    /// <summary>
+    /// Compile-only mirror of the SiteRuntime <c>FilesAccessor</c> (design 2026-09-28) — the
+    /// <c>Files</c> global's read-only, allow-listed file access.
+    /// </summary>
+    public sealed class CompileFiles
+    {
+        /// <summary>Mirrors <c>FilesAccessor.ReadTextAsync</c>.</summary>
+        /// <param name="path">Absolute path under an allowed root.</param>
+        /// <param name="cancellationToken">Cancels the read.</param>
+        /// <returns>The file's text.</returns>
+        public Task<string> ReadTextAsync(string path, CancellationToken cancellationToken = default)
+            => throw new NotSupportedException(CompileOnly);
+
+        /// <summary>Mirrors <c>FilesAccessor.ReadLinesAsync</c>.</summary>
+        /// <param name="path">Absolute path under an allowed root.</param>
+        /// <param name="cancellationToken">Cancels the read.</param>
+        /// <returns>The file's lines.</returns>
+        public Task<IReadOnlyList<string>> ReadLinesAsync(string path, CancellationToken cancellationToken = default)
+            => throw new NotSupportedException(CompileOnly);
+
+        /// <summary>Mirrors <c>FilesAccessor.ExistsAsync</c>.</summary>
+        /// <param name="path">Absolute path under an allowed root.</param>
+        /// <param name="cancellationToken">Cancels the check.</param>
+        /// <returns>Whether the file exists.</returns>
+        public Task<bool> ExistsAsync(string path, CancellationToken cancellationToken = default)
+            => throw new NotSupportedException(CompileOnly);
     }
 
     /// <summary>

src/ZB.MOM.WW.ScadaBridge.ScriptAnalysis/ScriptTrustPolicy.cs

@@ -342,5 +342,8 @@ public static class ScriptTrustPolicy
         "System.Collections.Generic",
         "System.Linq",
         "System.Threading.Tasks",
+        // Script-facing Commons types (ScriptAlarm, ScriptFileAccessException, …) — mirrors the
+        // site runtime's imports so the deploy gate binds the same short names (design 2026-09-28).
+        "ZB.MOM.WW.ScadaBridge.Commons.Types.Scripts",
     ];
 }

src/ZB.MOM.WW.ScadaBridge.SiteRuntime/Scripts/FilesAccessor.cs

@@ -0,0 +1,75 @@
+using ZB.MOM.WW.ScadaBridge.Commons.Types.Scripts;
+
+namespace ZB.MOM.WW.ScadaBridge.SiteRuntime.Scripts;
+
+/// <summary>
+/// The <c>Files</c> script global (design 2026-09-28): READ-ONLY access to files under the site
+/// node's configured <c>ScadaBridge:SiteRuntime:ScriptFileAccess:AllowedRoots</c> — e.g. a
+/// recipe file whose path a MES/Delmia call handed to the machine. Off by default. Every
+/// refusal or failure throws <see cref="ScriptFileAccessException"/>; reads are bounded by the
+/// script's own execution deadline as well as the caller's token.
+/// <code>
+/// foreach (var line in await Files.ReadLinesAsync(path)) { … }
+/// </code>
+/// </summary>
+public sealed class FilesAccessor
+{
+    private readonly IScriptFileReader? _reader;
+    private readonly CancellationToken _scriptToken;
+
+    /// <summary>Initializes a new instance.</summary>
+    /// <param name="reader">The host reader; null when the node has none wired (then every call throws Disabled).</param>
+    /// <param name="scriptToken">The running script's execution-timeout token.</param>
+    public FilesAccessor(IScriptFileReader? reader, CancellationToken scriptToken)
+    {
+        _reader = reader;
+        _scriptToken = scriptToken;
+    }
+
+    /// <summary>Reads a whole text file (BOM-detected, UTF-8 by default).</summary>
+    /// <param name="path">Absolute path under an allowed root.</param>
+    /// <param name="cancellationToken">Cancels the read.</param>
+    /// <returns>The file's text.</returns>
+    public async Task<string> ReadTextAsync(string path, CancellationToken cancellationToken = default)
+    {
+        using var linked = CancellationTokenSource.CreateLinkedTokenSource(_scriptToken, cancellationToken);
+        return await Reader.ReadTextAsync(path, linked.Token).ConfigureAwait(false);
+    }
+
+    /// <summary>
+    /// Reads a text file as lines (<c>\r\n</c>, <c>\n</c> or <c>\r</c>); a trailing line break does
+    /// not produce a final empty line.
+    /// </summary>
+    /// <param name="path">Absolute path under an allowed root.</param>
+    /// <param name="cancellationToken">Cancels the read.</param>
+    /// <returns>The file's lines.</returns>
+    public async Task<IReadOnlyList<string>> ReadLinesAsync(string path, CancellationToken cancellationToken = default)
+    {
+        var text = await ReadTextAsync(path, cancellationToken).ConfigureAwait(false);
+        return SplitLines(text);
+    }
+
+    /// <summary>True when an existing file is at the path; false when nothing is there. Still refuses paths outside the allowed roots.</summary>
+    /// <param name="path">Absolute path under an allowed root.</param>
+    /// <param name="cancellationToken">Cancels the check.</param>
+    /// <returns>Whether the file exists.</returns>
+    public async Task<bool> ExistsAsync(string path, CancellationToken cancellationToken = default)
+    {
+        using var linked = CancellationTokenSource.CreateLinkedTokenSource(_scriptToken, cancellationToken);
+        return await Reader.ExistsAsync(path, linked.Token).ConfigureAwait(false);
+    }
+
+    private IScriptFileReader Reader => _reader
+        ?? throw new ScriptFileAccessException(ScriptFileAccessFailure.Disabled,
+            "Script file access is not available on this node.");
+
+    internal static IReadOnlyList<string> SplitLines(string text)
+    {
+        if (text.Length == 0)
+            return Array.Empty<string>();
+        var lines = text.Split(["\r\n", "\n", "\r"], StringSplitOptions.None).ToList();
+        if (lines.Count > 0 && lines[^1].Length == 0)
+            lines.RemoveAt(lines.Count - 1);
+        return lines;
+    }
+}

src/ZB.MOM.WW.ScadaBridge.SiteRuntime/Scripts/ScriptCompilationService.cs

@@ -134,7 +134,10 @@ public class ScriptCompilationService
             "System",
             "System.Collections.Generic",
             "System.Linq",
-            "System.Threading.Tasks");
+            "System.Threading.Tasks",
+            // Script-facing Commons types (ScriptAlarm, ScriptFileAccessException, …) — lets a
+            // script `catch (ScriptFileAccessException)` by its short name (design 2026-09-28).
+            "ZB.MOM.WW.ScadaBridge.Commons.Types.Scripts");
 
     /// <summary>
     /// Compiles a script into a reusable delegate that takes a ScriptRuntimeContext
@@ -347,6 +350,14 @@ public class ScriptGlobals
     /// <summary>Leveled per-run logging (design 2026-09-09). Usage: <c>Log.Info("…")</c>, <c>Log.Warn("…", ex)</c>. Always reaches the node log; becomes Flow Debugger trace rows only for a traced run.</summary>
     public ScriptLogger Log => Instance.Log;
 
+    /// <summary>
+    /// Read-only file access under the node's configured allowed roots (design 2026-09-28).
+    /// Usage: <c>var lines = await Files.ReadLinesAsync(path);</c>. Off by default — every call
+    /// throws <c>ScriptFileAccessException(Disabled)</c> until
+    /// <c>ScadaBridge:SiteRuntime:ScriptFileAccess:AllowedRoots</c> is configured.
+    /// </summary>
+    public FilesAccessor Files => Instance.Files;
+
     /// <summary>
     /// Parent composition (null when this script is on a root-level template).
     /// <c>Parent.Attributes["SpeedRPM"]</c> reaches the parent's attribute;

src/ZB.MOM.WW.ScadaBridge.SiteRuntime/Scripts/ScriptFileAccessOptions.cs

@@ -0,0 +1,30 @@
+namespace ZB.MOM.WW.ScadaBridge.SiteRuntime.Scripts;
+
+/// <summary>
+/// <c>ScadaBridge:SiteRuntime:ScriptFileAccess</c> — the read-only file access a site script gets
+/// through the <c>Files</c> global (design 2026-09-28). The script trust policy still forbids
+/// <c>System.IO</c> outright; this is the one sanctioned, host-mediated exception, and it is
+/// <b>off by default</b>: with no <see cref="AllowedRoots"/> every <c>Files.*</c> call throws
+/// <c>ScriptFileAccessException(Disabled)</c>.
+/// </summary>
+public sealed class ScriptFileAccessOptions
+{
+    /// <summary>Largest value accepted for <see cref="MaxFileBytes"/> (64 MiB).</summary>
+    public const long MaxFileBytesCeiling = 64L * 1024 * 1024;
+
+    /// <summary>
+    /// Absolute directories (local or UNC) a script may read beneath. A path is allowed only when
+    /// its canonical form (after <c>..</c> resolution) is strictly inside one of these roots, and
+    /// no file or directory below the root is a symbolic link / junction. Empty (the default)
+    /// disables script file access on this node. The node's service account still needs NTFS/share
+    /// read permission — the allow-list narrows access, it never widens it.
+    /// </summary>
+    public List<string> AllowedRoots { get; set; } = new();
+
+    /// <summary>
+    /// Per-read size cap in bytes (default 1 MiB, at most <see cref="MaxFileBytesCeiling"/>). A
+    /// larger file throws <c>ScriptFileAccessException(TooLarge)</c> instead of being loaded into
+    /// the script's memory.
+    /// </summary>
+    public long MaxFileBytes { get; set; } = 1024 * 1024;
+}

src/ZB.MOM.WW.ScadaBridge.SiteRuntime/Scripts/ScriptFileReader.cs

@@ -0,0 +1,198 @@
+using System.Text;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
+using ZB.MOM.WW.ScadaBridge.Commons.Types.Scripts;
+
+namespace ZB.MOM.WW.ScadaBridge.SiteRuntime.Scripts;
+
+/// <summary>
+/// Host-side, read-only file access behind the script <c>Files</c> global (design 2026-09-28).
+/// Scripts never touch <c>System.IO</c> themselves; every path they pass is validated here
+/// against <see cref="ScriptFileAccessOptions.AllowedRoots"/>.
+/// </summary>
+public interface IScriptFileReader
+{
+    /// <summary>Reads the whole file as text (BOM-detected, UTF-8 by default).</summary>
+    /// <param name="path">Absolute path under an allowed root.</param>
+    /// <param name="cancellationToken">Cancels the read.</param>
+    /// <returns>The file's text.</returns>
+    Task<string> ReadTextAsync(string path, CancellationToken cancellationToken);
+
+    /// <summary>True when the path names an existing file under an allowed root; false when it does not exist.</summary>
+    /// <param name="path">Absolute path under an allowed root.</param>
+    /// <param name="cancellationToken">Cancels the check.</param>
+    /// <returns>Whether the file exists.</returns>
+    Task<bool> ExistsAsync(string path, CancellationToken cancellationToken);
+}
+
+/// <summary>
+/// Default <see cref="IScriptFileReader"/>. The guard, in order: access enabled (at least one
+/// root) → path well-formed and fully qualified (no device <c>\\?\</c>/<c>\\.\</c> paths, no
+/// alternate data streams) → canonical path strictly inside an allowed root (directory-boundary
+/// match, so root <c>C:\recipes</c> does not admit <c>C:\recipes2\x</c>) → no symbolic link,
+/// junction or other reparse point on the file or any directory between the root and the file
+/// (so a link planted inside a root cannot point outside it) → size under
+/// <see cref="ScriptFileAccessOptions.MaxFileBytes"/>, enforced again while reading in case the
+/// file grows. Every refusal and I/O failure is a <see cref="ScriptFileAccessException"/>.
+/// </summary>
+public sealed class ScriptFileReader : IScriptFileReader
+{
+    private readonly IOptionsMonitor<SiteRuntimeOptions> _options;
+    private readonly ILogger<ScriptFileReader> _logger;
+
+    /// <summary>Initializes a new instance.</summary>
+    /// <param name="options">Site runtime options (read per call, so a config reload applies).</param>
+    /// <param name="logger">Logger for refusals and reads.</param>
+    public ScriptFileReader(IOptionsMonitor<SiteRuntimeOptions> options, ILogger<ScriptFileReader> logger)
+    {
+        _options = options;
+        _logger = logger;
+    }
+
+    private static StringComparison PathComparison =>
+        OperatingSystem.IsWindows() ? StringComparison.OrdinalIgnoreCase : StringComparison.Ordinal;
+
+    /// <inheritdoc />
+    public async Task<string> ReadTextAsync(string path, CancellationToken cancellationToken)
+    {
+        var (full, root, settings) = Resolve(path);
+        var info = new FileInfo(full);
+        if (!info.Exists)
+            throw Fail(ScriptFileAccessFailure.NotFound, $"File not found: '{full}'.");
+        EnsureNoLinks(info, root);
+        if (info.Length > settings.MaxFileBytes)
+            throw Fail(ScriptFileAccessFailure.TooLarge,
+                $"File '{full}' is {info.Length} bytes; the limit is {settings.MaxFileBytes} (ScriptFileAccess:MaxFileBytes).");
+
+        try
+        {
+            using var buffer = new MemoryStream();
+            await using (var stream = new FileStream(full, FileMode.Open, FileAccess.Read,
+                             FileShare.ReadWrite | FileShare.Delete, bufferSize: 16 * 1024, useAsync: true))
+            {
+                var chunk = new byte[16 * 1024];
+                int n;
+                while ((n = await stream.ReadAsync(chunk, cancellationToken).ConfigureAwait(false)) > 0)
+                {
+                    if (buffer.Length + n > settings.MaxFileBytes)
+                        throw Fail(ScriptFileAccessFailure.TooLarge,
+                            $"File '{full}' grew past the {settings.MaxFileBytes}-byte limit while it was being read.");
+                    buffer.Write(chunk, 0, n);
+                }
+            }
+            buffer.Position = 0;
+            using var reader = new StreamReader(buffer, Encoding.UTF8, detectEncodingFromByteOrderMarks: true);
+            var text = await reader.ReadToEndAsync(cancellationToken).ConfigureAwait(false);
+            _logger.LogDebug("Script file read {Path} ({Bytes} bytes)", full, buffer.Length);
+            return text;
+        }
+        catch (ScriptFileAccessException) { throw; }
+        catch (OperationCanceledException) { throw; }
+        catch (FileNotFoundException ex)
+        {
+            throw Fail(ScriptFileAccessFailure.NotFound, $"File not found: '{full}'.", ex);
+        }
+        catch (DirectoryNotFoundException ex)
+        {
+            throw Fail(ScriptFileAccessFailure.NotFound, $"File not found: '{full}'.", ex);
+        }
+        catch (Exception ex) when (ex is IOException or UnauthorizedAccessException)
+        {
+            throw Fail(ScriptFileAccessFailure.IoError, $"Could not read '{full}': {ex.Message}", ex);
+        }
+    }
+
+    /// <inheritdoc />
+    public Task<bool> ExistsAsync(string path, CancellationToken cancellationToken)
+    {
+        cancellationToken.ThrowIfCancellationRequested();
+        var (full, root, _) = Resolve(path);
+        var info = new FileInfo(full);
+        if (!info.Exists)
+            return Task.FromResult(false);
+        EnsureNoLinks(info, root);
+        return Task.FromResult(true);
+    }
+
+    private (string Full, string Root, ScriptFileAccessOptions Settings) Resolve(string path)
+    {
+        var settings = _options.CurrentValue.ScriptFileAccess ?? new ScriptFileAccessOptions();
+        var roots = settings.AllowedRoots.Where(r => !string.IsNullOrWhiteSpace(r)).ToList();
+        if (roots.Count == 0)
+            throw Fail(ScriptFileAccessFailure.Disabled,
+                "Script file access is disabled on this node (ScadaBridge:SiteRuntime:ScriptFileAccess:AllowedRoots is empty).");
+
+        if (string.IsNullOrWhiteSpace(path) || path.IndexOf('\0') >= 0)
+            throw Fail(ScriptFileAccessFailure.InvalidPath, "A file path is required.");
+        path = path.Trim();
+        if (path.StartsWith(@"\\?\", StringComparison.Ordinal) || path.StartsWith(@"\\.\", StringComparison.Ordinal)
+            || path.StartsWith("//?/", StringComparison.Ordinal) || path.StartsWith("//./", StringComparison.Ordinal))
+            throw Fail(ScriptFileAccessFailure.InvalidPath, $"Device paths are not allowed: '{path}'.");
+        if (!Path.IsPathFullyQualified(path))
+            throw Fail(ScriptFileAccessFailure.InvalidPath, $"The path must be absolute: '{path}'.");
+
+        string full;
+        try
+        {
+            full = Path.GetFullPath(path);
+        }
+        catch (Exception ex) when (ex is ArgumentException or NotSupportedException or PathTooLongException)
+        {
+            throw Fail(ScriptFileAccessFailure.InvalidPath, $"Invalid path '{path}': {ex.Message}", ex);
+        }
+        // NTFS alternate data streams ("file.txt:hidden") — only the drive-letter colon is legal.
+        if (OperatingSystem.IsWindows() && full.IndexOf(':', 2) >= 0)
+            throw Fail(ScriptFileAccessFailure.InvalidPath, $"Alternate data streams are not allowed: '{path}'.");
+
+        foreach (var configured in roots)
+        {
+            var root = NormalizeRoot(configured);
+            if (full.Length > root.Length && full.StartsWith(root, PathComparison))
+                return (full, root, settings);
+        }
+
+        _logger.LogWarning("Script file access refused: '{Path}' is outside the allowed roots ({Roots})",
+            full, string.Join(", ", roots));
+        throw Fail(ScriptFileAccessFailure.OutsideAllowedRoots,
+            $"'{full}' is outside the allowed roots (ScadaBridge:SiteRuntime:ScriptFileAccess:AllowedRoots).");
+    }
+
+    /// <summary>Canonical root with exactly one trailing separator, for a directory-boundary prefix match.</summary>
+    private static string NormalizeRoot(string configured)
+    {
+        var root = Path.GetFullPath(configured.Trim());
+        return Path.EndsInDirectorySeparator(root) ? root : root + Path.DirectorySeparatorChar;
+    }
+
+    /// <summary>
+    /// Refuses a reparse point (symlink / junction / mount) on the file or on any directory strictly
+    /// below the root: a link inside an allowed root could otherwise point anywhere. The root itself
+    /// may be a link — an administrator configured it.
+    /// </summary>
+    private void EnsureNoLinks(FileInfo file, string root)
+    {
+        if (IsLink(file))
+            throw LinkRefused(file.FullName);
+        for (var dir = file.Directory; dir != null; dir = dir.Parent)
+        {
+            var withSep = Path.EndsInDirectorySeparator(dir.FullName) ? dir.FullName : dir.FullName + Path.DirectorySeparatorChar;
+            if (withSep.Length <= root.Length)
+                break;
+            if (IsLink(dir))
+                throw LinkRefused(dir.FullName);
+        }
+    }
+
+    private static bool IsLink(FileSystemInfo info) =>
+        info.LinkTarget != null || (info.Exists && info.Attributes.HasFlag(FileAttributes.ReparsePoint));
+
+    private ScriptFileAccessException LinkRefused(string at)
+    {
+        _logger.LogWarning("Script file access refused: '{Path}' is a symbolic link / reparse point", at);
+        return Fail(ScriptFileAccessFailure.LinkNotAllowed,
+            $"'{at}' is a symbolic link, junction or reparse point; links below an allowed root are not followed.");
+    }
+
+    private static ScriptFileAccessException Fail(ScriptFileAccessFailure failure, string message, Exception? inner = null)
+        => new(failure, message, inner);
+}

src/ZB.MOM.WW.ScadaBridge.SiteRuntime/Scripts/ScriptRunLauncher.cs

@@ -263,6 +263,7 @@ internal static class ScriptRunLauncher
         IAuditWriter? auditWriter = null;
         var siteId = string.Empty;
         string? sourceNode = null;
+        IScriptFileReader? fileReader = null;
         // ISiteEventLogger is a singleton; resolve from the root provider so
         // it is available to the catch blocks regardless of scope state.
         var siteEventLogger = serviceProvider?.GetService<ISiteEventLogger>();
@@ -346,6 +347,7 @@ internal static class ScriptRunLauncher
                 operationTrackingStore = serviceScope.ServiceProvider.GetService<IOperationTrackingStore>();
                 cachedForwarder = serviceScope.ServiceProvider.GetService<ICachedCallTelemetryForwarder>();
                 sourceNode = serviceScope.ServiceProvider.GetService<INodeIdentityProvider>()?.NodeName;
+                fileReader = serviceScope.ServiceProvider.GetService<IScriptFileReader>();
             }
 
             context = new ScriptRuntimeContext(
@@ -407,7 +409,9 @@ internal static class ScriptRunLauncher
                 // effectiveOptions (the IOptionsMonitor snapshot taken at the top of this run),
                 // so an operator's live edit applies from the NEXT run, like the event-policy
                 // flags above.
-                maxLogLinesPerRun: effectiveOptions.MaxLogLinesPerRun);
+                maxLogLinesPerRun: effectiveOptions.MaxLogLinesPerRun,
+                // Script file access (design 2026-09-28): the Files global's host reader.
+                fileReader: fileReader);
 
             var globals = new ScriptGlobals
             {
@@ -737,7 +741,9 @@ internal static class ScriptRunLauncher
                 // script's per-script execution-timeout token so a
                 // Attributes.WaitAsync inside an on-trigger script is bounded
                 // by the same script deadline.
-                scriptTimeoutToken: cts.Token);
+                scriptTimeoutToken: cts.Token,
+                // Script file access (design 2026-09-28): the Files global's host reader.
+                fileReader: services?.GetService<IScriptFileReader>());
 
             var globals = new ScriptGlobals
             {

src/ZB.MOM.WW.ScadaBridge.SiteRuntime/Scripts/ScriptRuntimeContext.cs

@@ -335,7 +335,8 @@ public class ScriptRuntimeContext
         bool isTraced = false,
         FlowTraceCollector? traceCollector = null,
         int maxLogLinesPerRun = 200,
-        ScriptLogger? sharedLog = null)
+        ScriptLogger? sharedLog = null,
+        IScriptFileReader? fileReader = null)
     {
         _instanceActor = instanceActor;
         _sharedScriptLibrary = sharedScriptLibrary;
@@ -368,6 +369,8 @@ public class ScriptRuntimeContext
         // WaitForAttribute (spec §4.3): default(CancellationToken) == None when
         // not threaded in — the WaitAsync Ask is then bounded only by its own timeout.
         _scriptTimeoutToken = scriptTimeoutToken;
+        // Script file access (design 2026-09-28): null when the host wired no reader — Files.* then throws Disabled.
+        _fileReader = fileReader;
         _isTraced = isTraced;
         _traceCollector = traceCollector;
         _traceSink = traceCollector is null ? null : Collect;
@@ -503,7 +506,9 @@ public class ScriptRuntimeContext
             // Step logs (design §5): the inline shared script is its own execution node for step
             // rows, but it SHARES this run's Log — one line cap and one anchor for the whole
             // inline chain, so its lines carry this run's ExecutionId.
-            sharedLog: Log);
+            sharedLog: Log,
+            // Script file access (design 2026-09-28): the inline shared script reads through the same host reader.
+            fileReader: _fileReader);
     }
 
     /// <summary>
@@ -1248,6 +1253,15 @@ public class ScriptRuntimeContext
     /// </summary>
     public AlarmsAccessor Alarms => _alarms ??= new(this);
 
+    private readonly IScriptFileReader? _fileReader;
+    private FilesAccessor? _files;
+
+    /// <summary>
+    /// Read-only access to files under the node's configured allowed roots (design 2026-09-28).
+    /// Bounded by this run's execution deadline. Off by default.
+    /// </summary>
+    public FilesAccessor Files => _files ??= new(_fileReader, _scriptTimeoutToken);
+
     /// <summary>
     /// Backing read for <see cref="AlarmsAccessor.CurrentAsync"/>: Asks THIS instance's
     /// Instance Actor for its retained alarm rows and projects them to

src/ZB.MOM.WW.ScadaBridge.SiteRuntime/ServiceCollectionExtensions.cs

@@ -73,6 +73,11 @@ public static class ServiceCollectionExtensions
         // construction, which is what runs SiteLocalDbSetup.OnReady.
         services.AddSingleton<Commons.Interfaces.IOperationTrackingStore, Tracking.OperationTrackingStore>();
 
+        // Script file access (design 2026-09-28): the host reader behind the Files global.
+        // Always registered — with no ScriptFileAccess:AllowedRoots configured it refuses every
+        // call (Disabled), so an unconfigured site behaves exactly as before.
+        services.AddSingleton<Scripts.IScriptFileReader, Scripts.ScriptFileReader>();
+
         // Site-local repository implementations backed by SQLite.
         // WP2.6a: ExternalSystemDefinitionCache is a singleton shared by every scoped
         // SiteExternalSystemRepository instance (one per script-execution DI scope), so

src/ZB.MOM.WW.ScadaBridge.SiteRuntime/SiteRuntimeOptions.cs

@@ -257,4 +257,10 @@ public class SiteRuntimeOptions
     /// Must be greater than 0. Default: 200.</para>
     /// </summary>
     public int MaxLogLinesPerRun { get; set; } = 200;
+
+    /// <summary>
+    /// Read-only script file access through the <c>Files</c> global (design 2026-09-28) — the
+    /// allow-listed roots and per-read size cap. Off by default (no roots).
+    /// </summary>
+    public Scripts.ScriptFileAccessOptions ScriptFileAccess { get; set; } = new();
 }

src/ZB.MOM.WW.ScadaBridge.SiteRuntime/SiteRuntimeOptionsValidator.cs

@@ -119,5 +119,17 @@ public sealed class SiteRuntimeOptionsValidator : OptionsValidatorBase<SiteRunti
             $"(was {options.MaxLogLinesPerRun}); it is the per-run cap on Flow Debugger ScriptLog " +
             "rows a script's Log.* calls may produce (design 2026-09-09 D7), and a run that may " +
             "emit no lines at all cannot report its own truncation.");
+
+        var files = options.ScriptFileAccess ?? new Scripts.ScriptFileAccessOptions();
+        builder.RequireThat(files.MaxFileBytes > 0 && files.MaxFileBytes <= Scripts.ScriptFileAccessOptions.MaxFileBytesCeiling,
+            $"ScadaBridge:SiteRuntime:ScriptFileAccess:MaxFileBytes must be between 1 and " +
+            $"{Scripts.ScriptFileAccessOptions.MaxFileBytesCeiling} (was {files.MaxFileBytes}); it caps one Files.* read.");
+        for (var i = 0; i < files.AllowedRoots.Count; i++)
+        {
+            var root = files.AllowedRoots[i];
+            builder.RequireThat(!string.IsNullOrWhiteSpace(root) && System.IO.Path.IsPathFullyQualified(root),
+                $"ScadaBridge:SiteRuntime:ScriptFileAccess:AllowedRoots:{i} must be an absolute directory path " +
+                $"(was '{root}'); a relative root would resolve against the service's working directory.");
+        }
     }
 }