diff --git a/crates/pptx/src/lib.rs b/crates/pptx/src/lib.rs
index a6018b71..92274b62 100644
--- a/crates/pptx/src/lib.rs
+++ b/crates/pptx/src/lib.rs
@@ -34,8 +34,14 @@ pub enum PptxError {
 }
 
 /// Does this look like an OOXML package (zip with `[Content_Types].xml`)?
+///
+/// The part is looked up in the zip's central directory, not in the leading bytes: writers may
+/// store it anywhere in the archive (recent PowerPoint builds put it last, megabytes in).
 pub fn sniff(bytes: &[u8]) -> bool {
-    bytes.starts_with(b"PK") && bytes.windows(19).take(4096).any(|w| w == b"[Content_Types].xml")
+    if !bytes.starts_with(b"PK") {
+        return false;
+    }
+    zip::ZipArchive::new(std::io::Cursor::new(bytes)).map(|z| z.index_for_name("[Content_Types].xml").is_some()).unwrap_or(false)
 }
 
 /// Read a `.pptx` / `.potx` / `.ppsx` package.
diff --git a/crates/pptx/tests/sniff.rs b/crates/pptx/tests/sniff.rs
new file mode 100644
index 00000000..69d9c961
--- /dev/null
+++ b/crates/pptx/tests/sniff.rs
@@ -0,0 +1,58 @@
+//! `sniff` must recognise a package wherever the writer put `[Content_Types].xml`: recent
+//! PowerPoint builds store it as the last zip entry, well past the first few kilobytes.
+
+use std::io::{Cursor, Read, Write};
+
+use deckcraft_engine::Session;
+use zip::write::SimpleFileOptions;
+
+fn sample_pptx() -> Vec<u8> {
+    let mut s = Session::new();
+    deckcraft_engine::sample::open_sample(&mut s).expect("sample");
+    let p = s.doc().expect("doc").doc.as_ref().clone();
+    deckcraft_pptx::export(&p).expect("export")
+}
+
+/// Re-pack `bytes` with `[Content_Types].xml` moved to the end and a padding part in front, so
+/// the content-types name first appears far beyond any fixed-size prefix.
+fn content_types_last(bytes: &[u8]) -> Vec<u8> {
+    let mut src = zip::ZipArchive::new(Cursor::new(bytes)).expect("zip");
+    let mut out = zip::ZipWriter::new(Cursor::new(Vec::new()));
+    let stored = SimpleFileOptions::default().compression_method(zip::CompressionMethod::Stored);
+    out.start_file("ppt/media/padding.bin", stored).expect("start");
+    out.write_all(&vec![0u8; 64 * 1024]).expect("padding");
+    let names: Vec<String> = (0..src.len()).map(|i| src.by_index(i).expect("entry").name().to_string()).collect();
+    for name in names.iter().filter(|n| *n != "[Content_Types].xml").chain(std::iter::once(&"[Content_Types].xml".to_string())) {
+        let mut data = Vec::new();
+        src.by_name(name).expect("by_name").read_to_end(&mut data).expect("read");
+        out.start_file(name, SimpleFileOptions::default()).expect("start");
+        out.write_all(&data).expect("write");
+    }
+    out.finish().expect("finish").into_inner()
+}
+
+#[test]
+fn sniff_accepts_content_types_anywhere_in_the_archive() {
+    let bytes = sample_pptx();
+    assert!(deckcraft_pptx::sniff(&bytes));
+
+    let moved = content_types_last(&bytes);
+    let first_4k = &moved[..4096.min(moved.len())];
+    assert!(!first_4k.windows(19).any(|w| w == b"[Content_Types].xml"), "test setup: name must not be in the prefix");
+    assert!(deckcraft_pptx::sniff(&moved));
+    let p = deckcraft_pptx::import(&moved).expect("import");
+    assert!(!p.slides.is_empty());
+}
+
+#[test]
+fn sniff_rejects_non_packages() {
+    assert!(!deckcraft_pptx::sniff(b""));
+    assert!(!deckcraft_pptx::sniff(b"PK"));
+    assert!(!deckcraft_pptx::sniff(b"%PDF-1.7 [Content_Types].xml"));
+
+    let mut out = zip::ZipWriter::new(Cursor::new(Vec::new()));
+    out.start_file("hello.txt", SimpleFileOptions::default()).expect("start");
+    out.write_all(b"not an office package").expect("write");
+    let plain_zip = out.finish().expect("finish").into_inner();
+    assert!(!deckcraft_pptx::sniff(&plain_zip));
+}