diff --git a/library/core/src/commonMain/kotlin/com/linroid/ketch/core/file/PathFileAccessor.kt b/library/core/src/commonMain/kotlin/com/linroid/ketch/core/file/PathFileAccessor.kt
index 38a812f..d81f0db 100644
--- a/library/core/src/commonMain/kotlin/com/linroid/ketch/core/file/PathFileAccessor.kt
+++ b/library/core/src/commonMain/kotlin/com/linroid/ketch/core/file/PathFileAccessor.kt
@@ -71,9 +71,23 @@ internal class PathFileAccessor(
   }
 
   override suspend fun preallocate(size: Long) {
+    if (size <= 0) return
     log.d { "Preallocating $size bytes: $realPath" }
     withContext(dispatcher) {
-      getOrCreateHandle().resize(size)
+      val handle = getOrCreateHandle()
+      val current = handle.size()
+      when {
+        size > current -> {
+          // okio 3.16.4 JvmFileHandle.protectedResize() grows by
+          // allocating ByteArray((size - current).toInt()) and writing
+          // it whole — this overflows Int and crashes with
+          // NegativeArraySizeException once delta exceeds 2 GB. Extend
+          // via a single sparse-byte write to avoid the bug and the
+          // gratuitous allocation.
+          handle.write(size - 1, byteArrayOf(0), 0, 1)
+        }
+        size < current -> handle.resize(size)
+      }
     }
   }
 }
diff --git a/library/core/src/jvmTest/kotlin/com/linroid/ketch/file/PathFileAccessorPreallocateTest.kt b/library/core/src/jvmTest/kotlin/com/linroid/ketch/file/PathFileAccessorPreallocateTest.kt
new file mode 100644
index 0000000..d179cff
--- /dev/null
+++ b/library/core/src/jvmTest/kotlin/com/linroid/ketch/file/PathFileAccessorPreallocateTest.kt
@@ -0,0 +1,74 @@
+package com.linroid.ketch.file
+
+import com.linroid.ketch.core.file.PathFileAccessor
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.test.runTest
+import java.nio.file.Files
+import kotlin.io.path.absolutePathString
+import kotlin.io.path.deleteIfExists
+import kotlin.io.path.fileSize
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+/**
+ * Regression tests for [PathFileAccessor.preallocate] — particularly
+ * around files larger than 2 GB. okio 3.16.4's `JvmFileHandle.protectedResize`
+ * allocates a `ByteArray(delta.toInt())` when growing a file, which throws
+ * `NegativeArraySizeException` once `delta` exceeds `Int.MAX_VALUE`. We
+ * extend via a single sparse write instead.
+ *
+ * Files are created sparse, so the disk footprint is one filesystem block,
+ * not the logical size.
+ */
+class PathFileAccessorPreallocateTest {
+
+  private fun tempPath(): String {
+    val dir = Files.createTempDirectory("ketch-preallocate-test")
+    return dir.resolve("file.bin").absolutePathString()
+  }
+
+  @Test
+  fun preallocate_smallFile() = runTest {
+    val path = tempPath()
+    val accessor = PathFileAccessor(path, Dispatchers.IO)
+    try {
+      accessor.preallocate(1024L)
+      assertEquals(1024L, java.nio.file.Path.of(path).fileSize())
+    } finally {
+      accessor.close()
+      java.nio.file.Path.of(path).deleteIfExists()
+    }
+  }
+
+  @Test
+  fun preallocate_above2GB_doesNotOverflow() = runTest {
+    val path = tempPath()
+    val size = 2_918_598_656L  // ~2.72 GB, matches the reported failure
+    val accessor = PathFileAccessor(path, Dispatchers.IO)
+    try {
+      accessor.preallocate(size)
+      assertEquals(size, java.nio.file.Path.of(path).fileSize())
+    } finally {
+      accessor.close()
+      java.nio.file.Path.of(path).deleteIfExists()
+    }
+  }
+
+  @Test
+  fun preallocate_zero_isNoOp() = runTest {
+    val path = tempPath()
+    val accessor = PathFileAccessor(path, Dispatchers.IO)
+    try {
+      accessor.preallocate(0L)
+      // No file written; size() opens the handle lazily — verify the
+      // file system path has no file or has size zero.
+      val p = java.nio.file.Path.of(path)
+      if (java.nio.file.Files.exists(p)) {
+        assertEquals(0L, p.fileSize())
+      }
+    } finally {
+      accessor.close()
+      java.nio.file.Path.of(path).deleteIfExists()
+    }
+  }
+}