diff --git a/crates/pptx/src/read/timing.rs b/crates/pptx/src/read/timing.rs
index 44f6d2a1a..3beb7fd69 100644
--- a/crates/pptx/src/read/timing.rs
+++ b/crates/pptx/src/read/timing.rs
@@ -330,9 +330,10 @@ pub fn animations(imp: &mut Imp, part: &Part, ctx: &IdCtx, timing: &El, shapes:
     for run in out.chunk_by(same_build) {
         let effects: Vec<&Animation> = run.iter().map(|(a, ..)| a).collect();
         let build = run.first().is_some_and(|r| r.3);
+        let explicit_bld = run.first().is_some_and(|r| bld_p.get(&(r.1, r.2.clone())) == Some(&true));
         let text = effects.first().and_then(|a| find_shape(shapes, a.shape)).and_then(|s| s.text.as_ref());
         match (effects.first(), text) {
-            (Some(first), Some(text)) if build && plays_as_build(&effects, text) => {
+            (Some(first), Some(text)) if build && plays_as_build(&effects, text, explicit_bld) => {
                 anims.push(Animation { text_build: TextBuild::ByParagraph, paragraph: None, ..(*first).clone() });
             }
             _ => anims.extend(effects.into_iter().cloned()),
@@ -345,7 +346,7 @@ pub fn animations(imp: &mut Imp, part: &Part, ctx: &IdCtx, timing: &El, shapes:
 /// first one plays: one effect per paragraph the build animates, in paragraph order, later top
 /// paragraphs on click (after previous when the build doesn't start on click), deeper ones with
 /// their parent, all with the same settings?
-fn plays_as_build(effects: &[&Animation], text: &TextBody) -> bool {
+fn plays_as_build(effects: &[&Animation], text: &TextBody, explicit_bld: bool) -> bool {
     let roles = paragraph_build_roles(text);
     let expected = roles.iter().enumerate().filter(|(i, r)| match r {
         BuildRole::Top => true,
@@ -353,6 +354,9 @@ fn plays_as_build(effects: &[&Animation], text: &TextBody) -> bool {
         BuildRole::Unowned => false,
     });
     let Some(first) = effects.first() else { return false };
+    if !explicit_bld && first.start != AnimStart::OnClick && (span_ms(first) != 500 || first.delay_ms != 0) {
+        return false;
+    }
     let settings = |a: &Animation| Animation { start: AnimStart::OnClick, paragraph: None, ..a.clone() };
     let base = settings(first);
     let mut matched = 0;
diff --git a/crates/pptx/tests/it/corpus_style.rs b/crates/pptx/tests/it/corpus_style.rs
index ed4f353ae..10e973c1a 100644
--- a/crates/pptx/tests/it/corpus_style.rs
+++ b/crates/pptx/tests/it/corpus_style.rs
@@ -317,6 +317,7 @@ fn right_of(p: &Presentation) -> ShapeId {
     by_name(p, "Right").id
 }
 
+/// Return a copy of the `.pptx` archive `bytes` with `entry_name` rewritten by `f`.
 fn rewrite_zip_entry(bytes: &[u8], entry_name: &str, f: impl Fn(&str) -> String) -> Vec<u8> {
     use std::io::{Cursor, Read, Write};
     let mut r = zip::ZipArchive::new(Cursor::new(bytes)).unwrap();
@@ -370,22 +371,26 @@ fn paragraph_build_without_bld_lst_still_folds_into_by_paragraph() {
     assert_eq!(back.slides[0].animations.len(), 1);
     assert_eq!(back.slides[0].animations[0].text_build, TextBuild::ByParagraph);
 
-    // Non-500ms After Previous paragraph build without bldLst is also inferred.
+    // Explicit bldP build="p" folds non-500ms After Previous builds, while without bldLst an 800ms
+    // After Previous run stays separate so playback does not alter its 800ms stagger to 500ms.
     let mut pres_after = pres.clone();
     let s_after = Arc::make_mut(&mut pres_after.slides[0]);
     s_after.animations[0].start = AnimStart::AfterPrevious;
     s_after.animations[0].duration_ms = 800;
     let bytes_after = deckcraft_pptx::export(&pres_after).unwrap();
+    let back_explicit_after = deckcraft_pptx::import(&bytes_after).unwrap();
+    assert_eq!(back_explicit_after.slides[0].animations.len(), 1);
+    assert_eq!(back_explicit_after.slides[0].animations[0].text_build, TextBuild::ByParagraph);
+    assert_eq!(back_explicit_after.slides[0].animations[0].duration_ms, 800);
+
     let without_bld_after = rewrite_zip_entry(&bytes_after, "ppt/slides/slide1.xml", |xml| {
         let start = xml.find("<p:bldLst>").expect("bldLst");
         let end = xml.find("</p:bldLst>").expect("/bldLst") + "</p:bldLst>".len();
         format!("{}{}", &xml[..start], &xml[end..])
     });
     let back_after = deckcraft_pptx::import(&without_bld_after).unwrap();
-    assert_eq!(back_after.slides[0].animations.len(), 1);
-    assert_eq!(back_after.slides[0].animations[0].text_build, TextBuild::ByParagraph);
-    assert_eq!(back_after.slides[0].animations[0].duration_ms, 800);
-
+    assert_eq!(back_after.slides[0].animations.len(), 2);
+    assert!(back_after.slides[0].animations.iter().all(|a| a.text_build == TextBuild::default()));
     // Explicit bldP with build!="p" (e.g. build="cust") opts out of folding.
     let custom_bld = rewrite_zip_entry(&bytes, "ppt/slides/slide1.xml", |xml| xml.replace(r#"build="p""#, r#"build="cust""#));
     let back_cust = deckcraft_pptx::import(&custom_bld).unwrap();