fix(media): enforce the 90-second video limit on the server

Read the duration from the MP4/MOV movie header (moov/mvhd) on both the
dispatcher media endpoint and the vendor portal completion upload, so a
direct request cannot bypass the browser check. Unreadable metadata still
never blocks an upload.

Api.SeaHavenIndustries.Tests/VendorPortalDocumentTests.cs

@@ -453,6 +453,50 @@ public sealed class VendorPortalDocumentTests : IDisposable
         context.VendorCompletionDocuments.Should().BeEmpty();
     }
 
+    /// <summary>ftyp + mdat + moov/mvhd (moov last, as phones write it).</summary>
+    private static byte[] PhoneVideoBytes(uint durationSeconds)
+    {
+        static byte[] Box(string type, byte[] body)
+        {
+            var box = new byte[8 + body.Length];
+            System.Buffers.Binary.BinaryPrimitives.WriteUInt32BigEndian(box, (uint)box.Length);
+            System.Text.Encoding.ASCII.GetBytes(type).CopyTo(box, 4);
+            body.CopyTo(box, 8);
+            return box;
+        }
+
+        var mvhd = new byte[20];
+        System.Buffers.Binary.BinaryPrimitives.WriteUInt32BigEndian(mvhd.AsSpan(12), 600);
+        System.Buffers.Binary.BinaryPrimitives.WriteUInt32BigEndian(mvhd.AsSpan(16), durationSeconds * 600);
+        return Box("ftyp", System.Text.Encoding.ASCII.GetBytes("qt  \0\0\0\0"))
+            .Concat(Box("mdat", new byte[4096]))
+            .Concat(Box("moov", Box("mvhd", mvhd)))
+            .ToArray();
+    }
+
+    [Theory]
+    [InlineData(95u, false)]
+    [InlineData(89u, true)]
+    public async Task UploadCompletionDocument_EnforcesNinetySecondVideoLimit(uint seconds, bool accepted)
+    {
+        using var context = NewContext();
+        var (_, dispatch) = await SeedDispatch(context);
+
+        var result = await NewController(context).UploadCompletionDocument(
+            dispatch.Id,
+            FormFile(PhoneVideoBytes(seconds), "IMG_0042.MOV", "video/quicktime"));
+
+        if (accepted)
+        {
+            result.Should().BeOfType<OkObjectResult>();
+        }
+        else
+        {
+            result.Should().BeOfType<BadRequestObjectResult>();
+            context.VendorCompletionDocuments.Should().BeEmpty();
+        }
+    }
+
     [Fact]
     public async Task UploadCompletionDocument_RejectsFourthVideoAcrossDispatcherAndVendorUploads()
     {

Api.SeaHavenIndustries.Tests/WorkOrderMediaControllerTests.cs

@@ -182,6 +182,60 @@ public class WorkOrderMediaControllerTests
         Assert.Equal(5, Assert.IsType<WorkOrderMediaFileDto>(ok.Value).Id);
     }
 
+    [Fact]
+    public async Task AddMedia_VideoLongerThanNinetySeconds_ReturnsStableUnprocessableEntity()
+    {
+        var storage = new Mock<IFileStoragePort>(MockBehavior.Strict);
+        var controller = CreateController(storage: storage);
+        var file = PhoneVideo(durationSeconds: 95, "IMG_0042.MOV", "video/quicktime");
+
+        var result = await controller.AddMedia(1, null, file, CancellationToken.None);
+
+        var response = Assert.IsType<UnprocessableEntityObjectResult>(result);
+        var error = Assert.IsType<WorkOrderBoardValidationErrorDto>(response.Value);
+        Assert.Equal("VideoTooLong", error.Code);
+        Assert.Equal("Videos must be 90 seconds or shorter.", error.Message);
+        storage.VerifyNoOtherCalls();
+    }
+
+    [Fact]
+    public async Task AddMedia_VideoWithinNinetySeconds_IsAccepted()
+    {
+        var (service, storage) = SetupSuccessfulAddMedia();
+        var controller = CreateController(service, storage);
+        var file = PhoneVideo(durationSeconds: 60, "IMG_0043.MOV", "");
+
+        var result = await controller.AddMedia(1, null, file, CancellationToken.None);
+
+        Assert.IsType<OkObjectResult>(result);
+    }
+
+    /// <summary>ftyp + mdat + moov/mvhd (moov last, as phones write it).</summary>
+    private static FormFile PhoneVideo(uint durationSeconds, string fileName, string contentType)
+    {
+        static byte[] Box(string type, byte[] body)
+        {
+            var box = new byte[8 + body.Length];
+            System.Buffers.Binary.BinaryPrimitives.WriteUInt32BigEndian(box, (uint)box.Length);
+            System.Text.Encoding.ASCII.GetBytes(type).CopyTo(box, 4);
+            body.CopyTo(box, 8);
+            return box;
+        }
+
+        var mvhd = new byte[20];
+        System.Buffers.Binary.BinaryPrimitives.WriteUInt32BigEndian(mvhd.AsSpan(12), 1000);
+        System.Buffers.Binary.BinaryPrimitives.WriteUInt32BigEndian(mvhd.AsSpan(16), durationSeconds * 1000);
+        var bytes = Box("ftyp", System.Text.Encoding.ASCII.GetBytes("qt  \0\0\0\0"))
+            .Concat(Box("mdat", new byte[4096]))
+            .Concat(Box("moov", Box("mvhd", mvhd)))
+            .ToArray();
+        return new FormFile(new MemoryStream(bytes), 0, bytes.Length, "file", fileName)
+        {
+            Headers = new HeaderDictionary(),
+            ContentType = contentType
+        };
+    }
+
     [Fact]
     public async Task AddMedia_SixtyMegabyteQuicktimeMov_IsAccepted()
     {

Api.SeaHavenIndustries/Controllers/WorkOrderMediaController.cs

@@ -98,6 +98,15 @@ namespace Api.SeaHavenIndustries.Controllers
                 }
 
                 WorkOrderMediaFileRules.EnsureAllowed(file, category);
+                if (WorkOrderMediaContract.ResolveKind(
+                        WorkOrderMediaFileRules.ResolveUploadContentType(file), file.FileName)
+                    == WorkOrderMediaContract.UploadKind.Video)
+                {
+                    using var content = file.OpenReadStream();
+                    var durationMessage = WorkOrderMediaContract.ValidateVideoDuration(content);
+                    if (durationMessage != null)
+                        throw new WorkOrderBoardValidationException("VideoTooLong", durationMessage);
+                }
                 var actorId = User.FindFirstValue(ClaimTypes.NameIdentifier);
                 await _workOrderMediaService.EnsureCanMutateMediaAsync(id, User, actorId, cancellationToken, category);
 

SeaHaven.Services/Helpers/VideoDurationProbe.cs

@@ -0,0 +1,129 @@
+using System.Buffers.Binary;
+using System.Text;
+
+namespace SeaHaven.Services.Helpers
+{
+    /// <summary>
+    /// Reads a video's duration from the ISO base media (MP4 / QuickTime) movie header:
+    /// top-level <c>moov</c> box → <c>mvhd</c> timescale and duration. It seeks over box
+    /// headers only (the <c>moov</c> box may sit after a large <c>mdat</c>), never decodes
+    /// media and never allocates more than a few bytes. Returns null whenever the structure
+    /// cannot be read, so callers can let unreadable files through (SH-116: unreadable
+    /// metadata never blocks an upload).
+    /// </summary>
+    public static class VideoDurationProbe
+    {
+        private const int MaxBoxesPerLevel = 1024;
+
+        public static double? TryReadDurationSeconds(Stream? stream)
+        {
+            if (stream == null || !stream.CanSeek || !stream.CanRead)
+                return null;
+
+            try
+            {
+                var moov = FindBox(stream, 0, stream.Length, "moov");
+                if (moov == null)
+                    return null;
+
+                var mvhd = FindBox(stream, moov.Value.BodyStart, moov.Value.End, "mvhd");
+                return mvhd == null ? null : ReadMovieHeaderSeconds(stream, mvhd.Value);
+            }
+            catch (IOException)
+            {
+                return null;
+            }
+        }
+
+        private readonly record struct Box(long BodyStart, long End);
+
+        private static Box? FindBox(Stream stream, long start, long end, string type)
+        {
+            var header = new byte[8];
+            var position = start;
+            for (var i = 0; i < MaxBoxesPerLevel && position + 8 <= end; i++)
+            {
+                stream.Position = position;
+                if (!ReadExactly(stream, header, 8))
+                    return null;
+
+                long size = BinaryPrimitives.ReadUInt32BigEndian(header);
+                var boxType = Encoding.ASCII.GetString(header, 4, 4);
+                var headerLength = 8;
+                if (size == 1)
+                {
+                    // 64-bit "largesize" follows the type.
+                    var large = new byte[8];
+                    if (!ReadExactly(stream, large, 8))
+                        return null;
+                    var largeSize = BinaryPrimitives.ReadUInt64BigEndian(large);
+                    if (largeSize > long.MaxValue)
+                        return null;
+                    size = (long)largeSize;
+                    headerLength = 16;
+                }
+                else if (size == 0)
+                {
+                    size = end - position;
+                }
+
+                if (size < headerLength || position + size > end)
+                    return null;
+
+                if (boxType == type)
+                    return new Box(position + headerLength, position + size);
+
+                position += size;
+            }
+
+            return null;
+        }
+
+        private static double? ReadMovieHeaderSeconds(Stream stream, Box mvhd)
+        {
+            // version(1) flags(3), then v0: creation(4) modification(4) timescale(4) duration(4)
+            //                          v1: creation(8) modification(8) timescale(4) duration(8)
+            var body = new byte[32];
+            stream.Position = mvhd.BodyStart;
+            var available = (int)Math.Min(body.Length, mvhd.End - mvhd.BodyStart);
+            if (available < 20 || !ReadExactly(stream, body, available))
+                return null;
+
+            uint timescale;
+            ulong duration;
+            if (body[0] == 0)
+            {
+                timescale = BinaryPrimitives.ReadUInt32BigEndian(body.AsSpan(12, 4));
+                duration = BinaryPrimitives.ReadUInt32BigEndian(body.AsSpan(16, 4));
+            }
+            else if (body[0] == 1 && available >= 32)
+            {
+                timescale = BinaryPrimitives.ReadUInt32BigEndian(body.AsSpan(20, 4));
+                duration = BinaryPrimitives.ReadUInt64BigEndian(body.AsSpan(24, 8));
+            }
+            else
+            {
+                return null;
+            }
+
+            // All-ones duration means "unknown" in the spec.
+            if (timescale == 0 || duration == uint.MaxValue || duration == ulong.MaxValue)
+                return null;
+
+            return (double)duration / timescale;
+        }
+
+        private static bool ReadExactly(Stream stream, byte[] buffer, int count)
+        {
+            var read = 0;
+            while (read < count)
+            {
+                var n = stream.Read(buffer, read, count - read);
+                if (n <= 0)
+                    return false;
+                read += n;
+            }
+            return true;
+        }
+    }
+}

SeaHaven.Services/Helpers/WorkOrderMediaContract.cs

@@ -4,9 +4,9 @@ namespace SeaHaven.Services.Helpers
     /// SH-116 client-confirmed media contract (2026-09-22): photos up to 10 MB (JPEG/PNG/HEIC),
     /// videos up to 100 MB and 90 seconds (MP4/MOV), at most 10 photos and 3 videos per work
     /// order, across the dispatcher media modal, the completion-doc media tab and the vendor
-    /// portal upload. Documents (PDF/DOC/DOCX) keep the 50 MB document cap. Duration is only
-    /// checkable client-side (the server cannot probe it cheaply), so it is enforced in the
-    /// browser and documented here as part of the same contract.
+    /// portal upload. Documents (PDF/DOC/DOCX) keep the 50 MB document cap. Duration is read
+    /// from the MP4/MOV movie header (<see cref="VideoDurationProbe"/>); the browser pre-checks
+    /// it and the server enforces it, and unreadable metadata never blocks an upload.
     /// </summary>
     public static class WorkOrderMediaContract
     {
@@ -103,6 +103,18 @@ namespace SeaHaven.Services.Helpers
             return null;
         }
 
+        /// <summary>
+        /// 90-second video limit, read from the MP4/QuickTime movie header. A video whose
+        /// duration cannot be read is not blocked. Returns the stable message or null.
+        /// </summary>
+        public static string? ValidateVideoDuration(Stream? content)
+        {
+            var seconds = VideoDurationProbe.TryReadDurationSeconds(content);
+            return seconds > MaxVideoDurationSeconds
+                ? $"Videos must be {MaxVideoDurationSeconds} seconds or shorter."
+                : null;
+        }
+
         /// <summary>Stable, generic per-kind size message; never echoes file metadata.</summary>
         public static string? ValidateSize(long length, UploadKind kind)
         {

SeaHaven.Services/Implementation/VendorPortalService.cs

@@ -900,6 +900,16 @@ namespace SeaHaven.Services.Implementation
                 throw new InvalidOperationException("The uploaded file signature does not match its declared content type.");
             }
 
+            if (kind == WorkOrderMediaContract.UploadKind.Video)
+            {
+                using var content = new MemoryStream(bytes, writable: false);
+                var durationMessage = WorkOrderMediaContract.ValidateVideoDuration(content);
+                if (durationMessage != null)
+                {
+                    throw new InvalidOperationException(durationMessage);
+                }
+            }
+
             var dispatch = await _dispatchData.GetVendorDispatchForMutationAsync(dispatchId, session.Id, cancellationToken);
             if (dispatch == null)
             {

SeaHavenIndustries.Tests/VideoDurationProbeTests.cs

@@ -0,0 +1,112 @@
+using System.Buffers.Binary;
+using System.Text;
+using SeaHaven.Services.Helpers;
+
+namespace SeaHavenIndustries.Tests;
+
+public class VideoDurationProbeTests
+{
+    internal static byte[] Box(string type, params byte[][] children)
+    {
+        var body = children.SelectMany(child => child).ToArray();
+        var box = new byte[8 + body.Length];
+        BinaryPrimitives.WriteUInt32BigEndian(box, (uint)box.Length);
+        Encoding.ASCII.GetBytes(type).CopyTo(box, 4);
+        body.CopyTo(box, 8);
+        return box;
+    }
+
+    internal static byte[] MovieHeader(uint timescale, ulong duration, bool version1 = false)
+    {
+        var body = new byte[version1 ? 32 : 20];
+        body[0] = version1 ? (byte)1 : (byte)0;
+        if (version1)
+        {
+            BinaryPrimitives.WriteUInt32BigEndian(body.AsSpan(20), timescale);
+            BinaryPrimitives.WriteUInt64BigEndian(body.AsSpan(24), duration);
+        }
+        else
+        {
+            BinaryPrimitives.WriteUInt32BigEndian(body.AsSpan(12), timescale);
+            BinaryPrimitives.WriteUInt32BigEndian(body.AsSpan(16), (uint)duration);
+        }
+        return Box("mvhd", body);
+    }
+
+    /// <summary>A phone-style file: ftyp, a large mdat, then moov at the end (not fast-start).</summary>
+    internal static byte[] Mp4(uint timescale, ulong duration, bool version1 = false, int mediaBytes = 4096)
+    {
+        var ftyp = Box("ftyp", Encoding.ASCII.GetBytes("isom"), new byte[4]);
+        var mdat = Box("mdat", new byte[mediaBytes]);
+        var moov = Box("moov", MovieHeader(timescale, duration, version1));
+        return ftyp.Concat(mdat).Concat(moov).ToArray();
+    }
+
+    [Fact]
+    public void ReadsDurationFromMoovAfterMediaData()
+    {
+        Assert.Equal(95.0, VideoDurationProbe.TryReadDurationSeconds(new MemoryStream(Mp4(600, 57_000))));
+    }
+
+    [Fact]
+    public void ReadsVersionOneMovieHeader()
+    {
+        Assert.Equal(30.5, VideoDurationProbe.TryReadDurationSeconds(
+            new MemoryStream(Mp4(1000, 30_500, version1: true))));
+    }
+
+    [Fact]
+    public void FollowsSixtyFourBitBoxSizes()
+    {
+        var ftyp = Box("ftyp", Encoding.ASCII.GetBytes("qt  "), new byte[4]);
+        var mdatBody = new byte[512];
+        var mdat = new byte[16 + mdatBody.Length];
+        BinaryPrimitives.WriteUInt32BigEndian(mdat, 1);
+        Encoding.ASCII.GetBytes("mdat").CopyTo(mdat, 4);
+        BinaryPrimitives.WriteUInt64BigEndian(mdat.AsSpan(8), (ulong)mdat.Length);
+        var moov = Box("moov", MovieHeader(90_000, 90_000UL * 120));
+        var file = ftyp.Concat(mdat).Concat(moov).ToArray();
+
+        Assert.Equal(120.0, VideoDurationProbe.TryReadDurationSeconds(new MemoryStream(file)));
+    }
+
+    [Theory]
+    [InlineData("no-moov")]
+    [InlineData("truncated")]
+    [InlineData("zero-timescale")]
+    [InlineData("oversized-box")]
+    public void UnreadableStructureReturnsNull(string shape)
+    {
+        var bytes = shape switch
+        {
+            "no-moov" => Box("ftyp", Encoding.ASCII.GetBytes("isom"), new byte[4]).Concat(Box("mdat", new byte[64])).ToArray(),
+            "truncated" => Mp4(600, 57_000)[..^10],
+            "zero-timescale" => Mp4(0, 57_000),
+            _ => Box("ftyp", new byte[8]).Concat(new byte[] { 0x7F, 0xFF, 0xFF, 0xFF, (byte)'m', (byte)'o', (byte)'o', (byte)'v' }).ToArray(),
+        };
+
+        Assert.Null(VideoDurationProbe.TryReadDurationSeconds(new MemoryStream(bytes)));
+    }
+
+    [Fact]
+    public void NonSeekableStreamReturnsNull()
+    {
+        Assert.Null(VideoDurationProbe.TryReadDurationSeconds(new NonSeekableStream(Mp4(600, 57_000))));
+    }
+
+    [Theory]
+    [InlineData(90.0, true)]
+    [InlineData(90.5, false)]
+    public void ContractAllowsUpToNinetySeconds(double seconds, bool allowed)
+    {
+        var message = WorkOrderMediaContract.ValidateVideoDuration(
+            new MemoryStream(Mp4(1000, (ulong)(seconds * 1000))));
+
+        Assert.Equal(allowed ? null : "Videos must be 90 seconds or shorter.", message);
+    }
+
+    private sealed class NonSeekableStream(byte[] bytes) : MemoryStream(bytes)
+    {
+        public override bool CanSeek => false;
+    }
+}