Fix --sort-reexports crash with non-seekable streams (e.g. stdin)

isort/api.py

@@ -203,6 +203,11 @@ def sort_stream(
         if not output_stream.readable():
             _internal_output = StringIO()
 
+    if config.sort_reexports and not _internal_output.seekable():
+        raise ValueError(
+            "sort_reexports requires a seekable output stream "
+            "and cannot be used with non-seekable streams such as stdout."
+        )
     try:
         changed = core.process(
             input_stream,

tests/unit/test_regressions.py

@@ -1985,3 +1985,36 @@ def test_comment_on_opening_line_of_aliased_import_does_not_move():
         isort.code(short_line, profile="black")
         == "from mod import attr as alias  # type: ignore[attr-defined]  # My comment\n"
     )
+
+
+def test_sort_reexports_with_non_seekable_stream_issue_2393():
+    """Ensure --sort-reexports raises a clear error when output stream is
+    issues #2393
+    """
+    import io
+    import sys
+
+    code = "from test import B, A\n__all__ = ['B', 'A']\n"
+
+    # Simulate a non-seekable stream (like a pipe/stdout)
+    class NonSeekableStream(io.StringIO):
+        def seekable(self):
+            return False
+
+    with pytest.raises(ValueError, match="sort_reexports"):
+        isort.api.sort_stream(
+            input_stream=io.StringIO(code),
+            output_stream=NonSeekableStream(),
+            sort_reexports=True,
+        )
+
+    # Seekable stream should still work correctly
+    output_stream = io.StringIO()
+    isort.api.sort_stream(
+        input_stream=io.StringIO(code),
+        output_stream=output_stream,
+        sort_reexports=True,
+    )
+    output_stream.seek(0)
+    assert "import A, B" in output_stream.read()
+