From d56b676ee94e2c177ffd9e89f79b0feed243013f Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 17 Mar 2026 12:25:29 +0000
Subject: [PATCH] fix: increase RewindableBufferSize to 160KB to cover
 ZStandard worst-case first block

Co-authored-by: adamhathcock <527620+adamhathcock@users.noreply.github.com>
---
 src/SharpCompress/Common/Constants.cs      | 6 ++++--
 src/SharpCompress/Readers/ReaderOptions.cs | 3 ++-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/SharpCompress/Common/Constants.cs b/src/SharpCompress/Common/Constants.cs
index 5fba5ed9..9812501d 100644
--- a/src/SharpCompress/Common/Constants.cs
+++ b/src/SharpCompress/Common/Constants.cs
@@ -22,7 +22,9 @@ public static class Constants
     /// by rewinding and re-reading the same data.
     /// </para>
     /// <para>
-    /// <b>Default:</b> 81920 bytes (81KB) - sufficient for typical format detection.
+    /// <b>Default:</b> 163840 bytes (160KB) - sized to cover ZStandard's worst-case
+    /// first block on a tar archive (~131KB including frame header overhead).
+    /// ZStandard blocks can be up to 128KB, exceeding the previous 81KB default.
     /// </para>
     /// <para>
     /// <b>Typical usage:</b> 500-1000 bytes for most archives
@@ -39,7 +41,7 @@ public static class Constants
     /// </list>
     /// </para>
     /// </remarks>
-    public static int RewindableBufferSize { get; set; } = 81920;
+    public static int RewindableBufferSize { get; set; } = 163840;
 
     public static CultureInfo DefaultCultureInfo { get; set; } = CultureInfo.InvariantCulture;
 }
diff --git a/src/SharpCompress/Readers/ReaderOptions.cs b/src/SharpCompress/Readers/ReaderOptions.cs
index dd384d2d..6a063611 100644
--- a/src/SharpCompress/Readers/ReaderOptions.cs
+++ b/src/SharpCompress/Readers/ReaderOptions.cs
@@ -76,7 +76,8 @@ public sealed record ReaderOptions : IReaderOptions
     /// by rewinding and re-reading the same data.
     /// </para>
     /// <para>
-    /// <b>Default:</b> Constants.RewindableBufferSize (81920 bytes / 81KB)
+    /// <b>Default:</b> Constants.RewindableBufferSize (163840 bytes / 160KB) - sized to cover
+    /// ZStandard's worst-case first block on a tar archive (~131KB including header overhead).
     /// </para>
     /// <para>
     /// <b>Typical usage:</b> 500-1000 bytes for most archives