diff --git a/AGENTS.md b/AGENTS.md
index 32bbb942..3c960eea 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -126,10 +126,15 @@ SharpCompress supports multiple archive and compression formats:
 - See [docs/FORMATS.md](docs/FORMATS.md) for complete format support matrix
 
 ### Stream Handling Rules
-- **Disposal**: As of version 0.21, SharpCompress closes wrapped streams by default
-- Use `ReaderOptions` or `WriterOptions` with `LeaveStreamOpen = true` to control stream disposal
+- **Disposal**: As of version 0.21, SharpCompress **closes wrapped streams by default** (`LeaveStreamOpen = false`)
+  - File-based overloads (e.g., `OpenArchive(string filePath)`) use `ReaderOptions.ForFilePath` automatically
+  - Stream-based overloads (e.g., `OpenArchive(Stream stream)`) use `ReaderOptions.ForExternalStream` by default, which sets `LeaveStreamOpen = true`
+- **For caller-provided streams**: Use `ReaderOptions` with `LeaveStreamOpen = true` or the `ForExternalStream` preset to prevent automatic disposal
+  - Example: `var options = new ReaderOptions { LeaveStreamOpen = true };`
+  - Or: `var options = ReaderOptions.ForExternalStream;`
+- **For file paths**: SharpCompress manages the stream lifecycle; no manual disposal needed beyond the archive/reader itself
 - Use `NonDisposingStream` wrapper when working with compression streams directly to prevent disposal
-- Always dispose of readers, writers, and archives in `using` blocks
+- Always dispose of readers, writers, and archives in `using` / `await using` blocks
 - For forward-only operations, use Reader/Writer APIs; for random access, use Archive APIs
 
 ### Async/Await Patterns
diff --git a/src/SharpCompress/Readers/ReaderOptions.cs b/src/SharpCompress/Readers/ReaderOptions.cs
index 6a063611..ed496101 100644
--- a/src/SharpCompress/Readers/ReaderOptions.cs
+++ b/src/SharpCompress/Readers/ReaderOptions.cs
@@ -24,9 +24,36 @@ namespace SharpCompress.Readers;
 public sealed record ReaderOptions : IReaderOptions
 {
     /// <summary>
-    /// SharpCompress will keep the supplied streams open.  Default is true.
+    /// SharpCompress will keep the supplied streams open.
+    /// Default is false as of v0.21: streams are closed when the archive/reader is disposed.
+    /// Set to true when passing caller-owned streams that should not be disposed.
     /// </summary>
-    public bool LeaveStreamOpen { get; init; } = true;
+    /// <remarks>
+    /// <para>
+    /// <b>Default behavior (LeaveStreamOpen = false):</b>
+    /// When you open an archive from a file path (e.g., <c>GZipArchive.OpenArchive(filePath)</c>),
+    /// SharpCompress manages the stream lifetime and closes it on Dispose.
+    /// </para>
+    /// <para>
+    /// <b>Caller-provided streams (LeaveStreamOpen = true):</b>
+    /// When you pass a stream you created (FileStream, MemoryStream, NetworkStream, etc.),
+    /// set LeaveStreamOpen = true to prevent SharpCompress from disposing it.
+    /// Use <see cref="ForExternalStream"/> preset for convenience.
+    /// </para>
+    /// <para>
+    /// <b>Example:</b>
+    /// <code>
+    /// // File-based: stream managed by library
+    /// using var archive = GZipArchive.OpenArchive(filePath); // LeaveStreamOpen = false
+    ///
+    /// // Caller-provided stream: caller manages lifetime
+    /// using var stream = File.OpenRead(filePath);
+    /// var options = new ReaderOptions { LeaveStreamOpen = true };
+    /// using var archive = GZipArchive.OpenArchive(stream, options);
+    /// </code>
+    /// </para>
+    /// </remarks>
+    public bool LeaveStreamOpen { get; init; } = false;
 
     /// <summary>
     /// Encoding to use for archive entry names.