diff --git a/src/SharpEmu.Libs/Kernel/KernelAprCompatExports.cs b/src/SharpEmu.Libs/Kernel/KernelAprCompatExports.cs
index e363383..1242b9d 100644
--- a/src/SharpEmu.Libs/Kernel/KernelAprCompatExports.cs
+++ b/src/SharpEmu.Libs/Kernel/KernelAprCompatExports.cs
@@ -166,19 +166,6 @@ public static class KernelAprCompatExports
         return (int)OrbisGen2Result.ORBIS_GEN2_OK;
     }
 
-    // Success stub: the argument layout is unknown and callers tolerate the
-    // empty answer (Quake streams fine), so no output payload is written until
-    // the real signature is reversed.
-    [SysAbiExport(
-        Nid = "WvEu7yl3Ivg",
-        ExportName = "sceKernelAprGetFileSize",
-        Target = Generation.Gen4 | Generation.Gen5,
-        LibraryName = "libKernel")]
-    public static int KernelAprGetFileSize(CpuContext ctx)
-    {
-        return ctx.SetReturn(0);
-    }
-
     private static bool TryWriteAprResult(
         CpuContext ctx,
         ulong resultAddress,
diff --git a/src/SharpEmu.Libs/Kernel/KernelMemoryCompatExports.cs b/src/SharpEmu.Libs/Kernel/KernelMemoryCompatExports.cs
index d2d94fb..5093b89 100644
--- a/src/SharpEmu.Libs/Kernel/KernelMemoryCompatExports.cs
+++ b/src/SharpEmu.Libs/Kernel/KernelMemoryCompatExports.cs
@@ -1993,6 +1993,48 @@ public static partial class KernelMemoryCompatExports
         return (int)OrbisGen2Result.ORBIS_GEN2_OK;
     }
 
+    // Signature: (SceKernelAprFileId id, uint64_t* size). Callers size their read buffer from the
+    // answer and may pass an uninitialized slot, so the size must always be written on success.
+    [SysAbiExport(
+        Nid = "WvEu7yl3Ivg",
+        ExportName = "sceKernelAprGetFileSize",
+        Target = Generation.Gen4 | Generation.Gen5,
+        LibraryName = "libKernel")]
+    public static int KernelAprGetFileSize(CpuContext ctx)
+    {
+        var fileId = unchecked((uint)ctx[CpuRegister.Rdi]);
+        var sizeAddress = ctx[CpuRegister.Rsi];
+        if (sizeAddress == 0)
+        {
+            KernelRuntimeCompatExports.TrySetErrno(ctx, Einval);
+            return (int)OrbisGen2Result.ORBIS_GEN2_ERROR_INVALID_ARGUMENT;
+        }
+
+        if (!AmprFileRegistry.TryGetHostPath(fileId, out var hostPath))
+        {
+            LogIoTrace("apr_get_file_size", $"id=0x{fileId:X8}", "result=id_not_registered");
+            KernelRuntimeCompatExports.TrySetErrno(ctx, 2);
+            return (int)OrbisGen2Result.ORBIS_GEN2_ERROR_NOT_FOUND;
+        }
+
+        if (!TryGetAprFileSize(hostPath, out var size))
+        {
+            LogIoTrace("apr_get_file_size", hostPath, $"id=0x{fileId:X8} result=not_found");
+            KernelRuntimeCompatExports.TrySetErrno(ctx, 2);
+            return (int)OrbisGen2Result.ORBIS_GEN2_ERROR_NOT_FOUND;
+        }
+
+        if (!TryWriteUInt64Compat(ctx, sizeAddress, size))
+        {
+            KernelRuntimeCompatExports.TrySetErrno(ctx, Efault);
+            return (int)OrbisGen2Result.ORBIS_GEN2_ERROR_MEMORY_FAULT;
+        }
+
+        LogIoTrace("apr_get_file_size", hostPath, $"id=0x{fileId:X8} size={size}");
+        ctx[CpuRegister.Rax] = 0;
+        return (int)OrbisGen2Result.ORBIS_GEN2_OK;
+    }
+
     [SysAbiExport(
         Nid = "kBwCPsYX-m4",
         ExportName = "sceKernelFstat",
diff --git a/tests/SharpEmu.Libs.Tests/Ampr/AprStreamingContractTests.cs b/tests/SharpEmu.Libs.Tests/Ampr/AprStreamingContractTests.cs
index cbc87d5..b41491b 100644
--- a/tests/SharpEmu.Libs.Tests/Ampr/AprStreamingContractTests.cs
+++ b/tests/SharpEmu.Libs.Tests/Ampr/AprStreamingContractTests.cs
@@ -22,6 +22,7 @@ public sealed class AprStreamingContractTests
         const ulong pathAddress = memoryBase + 0x200;
         const ulong idsAddress = memoryBase + 0x800;
         const ulong statAddress = memoryBase + 0x900;
+        const ulong sizeAddress = memoryBase + 0x9A0;
         const ulong commandBufferAddress = memoryBase + 0x1000;
         const ulong recordBufferAddress = memoryBase + 0x1100;
         const ulong destinationAddress = memoryBase + 0x2000;
@@ -68,6 +69,16 @@ public sealed class AprStreamingContractTests
             Assert.True(memory.TryRead(statAddress, stat));
             Assert.Equal(fileContents.Length, BinaryPrimitives.ReadInt64LittleEndian(stat[72..]));
 
+            WriteUInt64(memory, sizeAddress, 0xDEAD_BEEF);
+            context[CpuRegister.Rdi] = fileId;
+            context[CpuRegister.Rsi] = sizeAddress;
+
+            Assert.Equal(0, KernelMemoryCompatExports.KernelAprGetFileSize(context));
+            Assert.Equal((ulong)fileContents.Length, ReadUInt64(memory, sizeAddress));
+
+            context[CpuRegister.Rdi] = 0xFFFF_FFFE;
+            Assert.NotEqual(0, KernelMemoryCompatExports.KernelAprGetFileSize(context));
+
             context[CpuRegister.Rdi] = commandBufferAddress;
             context[CpuRegister.Rsi] = recordBufferAddress;
             context[CpuRegister.Rdx] = 0x100;