diff --git a/native/src/layout.rs b/native/src/layout.rs
index bb7e995..6e386bf 100644
--- a/native/src/layout.rs
+++ b/native/src/layout.rs
@@ -1248,6 +1248,13 @@ impl StyleTemplate {
     }
 }
 
+pub(crate) fn style_registry_extends_exact_prefix(
+    old: &[StyleTemplate],
+    target: &[StyleTemplate],
+) -> bool {
+    target.starts_with(old)
+}
+
 fn composed_face(
     properties: &AtomProperties,
     styles: &[CompiledStyle],
@@ -2269,6 +2276,17 @@ fn root_metadata_payload(
     }))
 }
 
+fn validate_tape_style_ids(properties: &AtomProperties, style_count: u32) -> Result<(), String> {
+    if properties
+        .style_ids
+        .iter()
+        .any(|style_id| *style_id >= style_count)
+    {
+        return Err("Native layout tape has invalid style id".to_owned());
+    }
+    Ok(())
+}
+
 fn flatten_layout_tape(tape: LayoutTape, complete: bool) -> Result<FlatLayoutTape, String> {
     if tape.lines.is_empty() {
         return Err("Native layout tape has no lines".to_owned());
@@ -2289,6 +2307,7 @@ fn flatten_layout_tape(tape: LayoutTape, complete: bool) -> Result<FlatLayoutTap
                     width,
                     properties,
                 } => {
+                    validate_tape_style_ids(&properties, tape.style_count)?;
                     let width = tape_width(width, "text width")?;
                     if text.is_empty() || text.contains('\n') {
                         return Err("Native layout tape has invalid text atom".to_owned());
@@ -2304,6 +2323,7 @@ fn flatten_layout_tape(tape: LayoutTape, complete: bool) -> Result<FlatLayoutTap
                         .ok_or_else(|| "Native layout tape width overflow".to_owned())?;
                 }
                 TapeAtom::Space { width, properties } => {
+                    validate_tape_style_ids(&properties, tape.style_count)?;
                     let width = tape_width(width, "space width")?;
                     if width == 0 {
                         return Err("Native layout tape has empty pixel space".to_owned());
@@ -2323,6 +2343,7 @@ fn flatten_layout_tape(tape: LayoutTape, complete: bool) -> Result<FlatLayoutTap
             return Err("Native layout tape line width invariant failed".to_owned());
         }
         if let Some(properties) = line.break_after {
+            validate_tape_style_ids(&properties, tape.style_count)?;
             characters.push(TapeCharacter {
                 value: '\n',
                 pixel_width: None,
@@ -2616,7 +2637,7 @@ pub(crate) fn encode_layout_patch_tape(
 ) -> Result<Vec<u8>, String> {
     let old = flatten_layout_tape(old_tape, identity.complete)?;
     let target = flatten_layout_tape(target_tape, identity.complete)?;
-    if old.style_count != target.style_count || target.style_count as usize != styles.len() {
+    if old.style_count > target.style_count || target.style_count as usize != styles.len() {
         return Err("Native layout patch style table mismatch".to_owned());
     }
     let compiled_styles = styles
@@ -5922,6 +5943,10 @@ mod tests {
         serde_json::from_str(json).unwrap()
     }
 
+    fn styles(json: &str) -> Vec<StyleTemplate> {
+        serde_json::from_str(json).unwrap()
+    }
+
     fn cluster(text: &str, width: i64, source_template_id: Option<u32>) -> MeasuredCluster {
         MeasuredCluster {
             text: text.to_owned(),
@@ -6115,6 +6140,77 @@ mod tests {
         }
     }
 
+    #[test]
+    fn style_registry_reuse_requires_an_exact_stable_prefix() {
+        let old = styles(
+            r##"[{"mode":"set","face":{"foreground":"#111111"}},{"mode":"add","face":{"background":"#222222"}}]"##,
+        );
+        let appended = styles(
+            r##"[{"mode":"set","face":{"foreground":"#111111"}},{"mode":"add","face":{"background":"#222222"}},{"mode":"set","face":{"foreground":"#333333"}}]"##,
+        );
+        let changed = styles(
+            r##"[{"mode":"set","face":{"foreground":"#999999"}},{"mode":"add","face":{"background":"#222222"}},{"mode":"set","face":{"foreground":"#333333"}}]"##,
+        );
+        let removed = styles(r##"[{"mode":"set","face":{"foreground":"#111111"}}]"##);
+        let renumbered = styles(
+            r##"[{"mode":"add","face":{"background":"#222222"}},{"mode":"set","face":{"foreground":"#111111"}},{"mode":"set","face":{"foreground":"#333333"}}]"##,
+        );
+
+        assert!(style_registry_extends_exact_prefix(&old, &appended));
+        assert!(!style_registry_extends_exact_prefix(&old, &changed));
+        assert!(!style_registry_extends_exact_prefix(&old, &removed));
+        assert!(!style_registry_extends_exact_prefix(&old, &renumbered));
+    }
+
+    #[test]
+    fn layout_patch_accepts_appended_styles_but_validates_each_tape_count() {
+        fn tape(style_count: u32, style_id: u32) -> LayoutTape {
+            LayoutTape {
+                style_count,
+                lines: vec![TapeLine {
+                    width: 1,
+                    atoms: vec![TapeAtom::Text {
+                        text: "x".to_owned(),
+                        width: 1,
+                        properties: AtomProperties {
+                            style_ids: vec![style_id],
+                            ..AtomProperties::default()
+                        },
+                    }],
+                    break_after: None,
+                }],
+            }
+        }
+
+        let registry = styles(
+            r##"[{"mode":"set","face":{"foreground":"#111111"}},{"mode":"set","face":{"background":"#222222"}}]"##,
+        );
+        let encoded = encode_layout_patch_tape(
+            tape(1, 0),
+            tape(2, 1),
+            &registry,
+            complete_identity(),
+            false,
+            4096,
+        )
+        .unwrap();
+        assert_ne!(
+            u16::from_le_bytes(encoded[6..8].try_into().unwrap()) & (1 << 2),
+            0
+        );
+
+        let error = encode_layout_patch_tape(
+            tape(1, 1),
+            tape(2, 1),
+            &registry,
+            complete_identity(),
+            false,
+            4096,
+        )
+        .unwrap_err();
+        assert_eq!(error, "Native layout tape has invalid style id");
+    }
+
     #[test]
     fn typed_column_lowering_stretches_centered_child() {
         let mut text = auto_text_box(3, measured_text(vec![vec![cluster("x", 10, None)]]), None);
diff --git a/native/src/lib.rs b/native/src/lib.rs
index de40b2b..1464fa3 100644
--- a/native/src/lib.rs
+++ b/native/src/lib.rs
@@ -1349,7 +1349,10 @@ fn render_layout_payload(
                                 baseline,
                                 document_base_revision,
                                 &base_identity,
-                            ) && baseline.styles == document.styles
+                            ) && layout::style_registry_extends_exact_prefix(
+                                &baseline.styles,
+                                &document.styles,
+                            )
                         })
                         .cloned();
                     if require_confirmed_patch_base && base_hit.is_none() {
@@ -2011,6 +2014,35 @@ mod tests {
             .into_bytes()
     }
 
+    fn styled_layout_payload(
+        document_base_revision: u64,
+        document_target_revision: u64,
+        style_count: u32,
+        styles: &str,
+        foreground_style: u32,
+        frames: &str,
+    ) -> Vec<u8> {
+        let payload = String::from_utf8(replacement_layout_payload(
+            document_base_revision,
+            document_target_revision,
+            frames,
+        ))
+        .unwrap();
+        payload
+            .replacen(
+                r#""style-count":0"#,
+                &format!(r#""style-count":{style_count}"#),
+                1,
+            )
+            .replacen(r#""styles":[]"#, &format!(r#""styles":{styles}"#), 1)
+            .replacen(
+                r#""foreground-style":null"#,
+                &format!(r#""foreground-style":{foreground_style}"#),
+                1,
+            )
+            .into_bytes()
+    }
+
     fn column_proof_layout_payload(frames: &str) -> Vec<u8> {
         format!(
             r#"{{"version":1,"document-base-revision":0,"document-target-revision":1,"document":{{"version":2,"space-width":8,"style-count":0,"styles":[],"root":{{"type":"column","children":[{{"type":"box","region-id":1,"content":{{"lines":[{{"clusters":[{{"text":"x","width":8,"cjk":false,"space":false}}]}}]}},"child":null,"content-width-exact":false,"width":{{"kind":"content"}},"min-width":{{"kind":"pixels","value":0}},"max-width":{{"kind":"none"}},"height":{{"kind":"auto"}},"min-height":{{"kind":"lines","value":0}},"max-height":{{"kind":"none"}},"box-sizing":"border-box","padding-left":0,"padding-right":0,"padding-top":0,"padding-bottom":0,"margin-left":0,"margin-right":0,"margin-top":0,"margin-bottom":0,"border-left":0,"border-right":0,"foreground-style":null,"background-style":null,"border-left-style":null,"border-right-style":null,"border-top-style":null,"border-bottom-style":null,"text-align":"left","vertical-align":"top","overflow":"scroll","wrap-mode":"word","scroll-offset":0}},{{"type":"box","region-id":2,"content":{{"lines":[{{"clusters":[{{"text":"yy","width":16,"cjk":false,"space":false}}]}}]}},"child":null,"content-width-exact":false,"width":{{"kind":"content"}},"min-width":{{"kind":"pixels","value":0}},"max-width":{{"kind":"none"}},"height":{{"kind":"auto"}},"min-height":{{"kind":"lines","value":0}},"max-height":{{"kind":"none"}},"box-sizing":"border-box","padding-left":0,"padding-right":0,"padding-top":0,"padding-bottom":0,"margin-left":0,"margin-right":0,"margin-top":0,"margin-bottom":0,"border-left":0,"border-right":0,"foreground-style":null,"background-style":null,"border-left-style":null,"border-right-style":null,"border-top-style":null,"border-bottom-style":null,"text-align":"left","vertical-align":"top","overflow":"scroll","wrap-mode":"word","scroll-offset":0}}]}}}},"frames":{frames}}}"#
@@ -2440,6 +2472,55 @@ mod tests {
         child.stop(true);
     }
 
+    #[test]
+    fn confirmed_patch_base_accepts_only_append_stable_style_registries() {
+        let parent = Session::new(1, 4, 4, 64 * 1024).unwrap();
+        let first = styled_layout_payload(
+            0,
+            1,
+            1,
+            r##"[{"mode":"set","face":{"foreground":"#111111"}}]"##,
+            0,
+            r#"[{"key":1,"viewport-width":120,"viewport-height":10,"root-width":120,"runtime-revision":0,"context-hash":77}]"#,
+        );
+        assert!(!tape_patch_p(&parent.render_sync(1, &first).unwrap()));
+        assert!(parent.confirm(1, 1, 1).unwrap());
+
+        let appended_child = parent.fork_confirmed().unwrap();
+        let appended = styled_layout_payload(
+            1,
+            2,
+            2,
+            r##"[{"mode":"set","face":{"foreground":"#111111"}},{"mode":"set","face":{"background":"#222222"}}]"##,
+            1,
+            r#"[{"key":2,"viewport-width":120,"viewport-height":10,"root-width":120,"patch":true,"base-viewport-width":120,"base-viewport-height":10,"base-root-width":120,"runtime-revision":1,"context-hash":77}]"#,
+        );
+        assert!(tape_patch_p(
+            &appended_child.render_sync(1, &appended).unwrap()
+        ));
+        assert_eq!(appended_child.stats().baseline_hits, 1);
+        assert_eq!(appended_child.stats().base_renders, 0);
+
+        let changed_child = parent.fork_confirmed().unwrap();
+        let changed = styled_layout_payload(
+            1,
+            2,
+            2,
+            r##"[{"mode":"set","face":{"foreground":"#999999"}},{"mode":"set","face":{"background":"#222222"}}]"##,
+            1,
+            r#"[{"key":3,"viewport-width":120,"viewport-height":10,"root-width":120,"patch":true,"base-viewport-width":120,"base-viewport-height":10,"base-root-width":120,"runtime-revision":1,"context-hash":77}]"#,
+        );
+        assert!(!tape_patch_p(
+            &changed_child.render_sync(1, &changed).unwrap()
+        ));
+        assert_eq!(changed_child.stats().baseline_hits, 0);
+        assert_eq!(changed_child.stats().base_renders, 0);
+
+        parent.stop(true);
+        appended_child.stop(true);
+        changed_child.stop(true);
+    }
+
     #[test]
     fn synchronous_proof_render_returns_full_tape_without_session() {
         let payload =
diff --git a/tests/ebox-surface-tests.el b/tests/ebox-surface-tests.el
index 3c228fc..b868a0e 100644
--- a/tests/ebox-surface-tests.el
+++ b/tests/ebox-surface-tests.el
@@ -1673,6 +1673,58 @@ candidate cannot hide mutations by restoring the old hash-table pointer."
       (when next-session
         (should (ebox-native-reflow-session-released-p next-session))))))
 
+(ert-deftest ebox-native-appended-style-keeps-a-local-property-patch ()
+  "An appended style preserves native and TP locality with exact output."
+  (skip-unless (ebox-native-reflow-layout-ready-p))
+  (ebox-surface-test--reset-render-state)
+  (let ((buffer (generate-new-buffer " *ebox-native-appended-style*")))
+    (unwind-protect
+        (cl-labels
+            ((source
+              (background)
+              (apply
+               #'ebox-test-column
+               (cl-loop
+                for index below 32
+                collect
+                (apply
+                 #'ebox-test-box
+                 (append
+                  (list :key index :source-identity index
+                        (ebox-test-text (char-to-string (+ ?A index))))
+                  (and (= index 16) background
+                       (list :bgcolor background)))))))
+             (node-ids
+              (state)
+              (let (ids)
+                (ebox-surface-test--walk-runtime
+                 (plist-get state :root-node)
+                 (lambda (node) (push (plist-get node :node-id) ids)))
+                (nreverse ids))))
+          (let ((ebox-viewport-width 240)
+                (ebox-viewport-height 40)
+                (ebox-runtime-idle-prewarm nil)
+                (ebox-runtime-idle-reflow-cache-prewarm nil))
+            (ebox-render-to-buffer buffer (source nil))
+            (let* ((surface
+                    (with-current-buffer buffer ebox-surface--buffer-surface))
+                   (old-state (tp-surface-client-state surface))
+                   (old-node-ids (node-ids old-state))
+                   (report (ebox-commit buffer (source "#224466")))
+                   (state (tp-surface-client-state surface))
+                   (tp-report (tp-surface-report surface))
+                   (expected (ebox-surface-test--render-runtime state))
+                   (actual
+                    (with-current-buffer buffer
+                      (buffer-substring (point-min) (point-max)))))
+              (should (eq (plist-get report :projection-kind) 'native-frame))
+              (should (eq (plist-get report :native-frame-kind) 'patch))
+              (should (= (plist-get tp-report :touched-characters) 2))
+              (should (equal (node-ids state) old-node-ids))
+              (should (equal-including-properties actual expected)))))
+      (when (buffer-live-p buffer)
+        (kill-buffer buffer)))))
+
 (ert-deftest ebox-viewport-reflow-retains-final-sized-flex-child-fragments ()
   "Viewport reflow should reuse final-sized Flex child fragments exactly."
   (ebox-surface-test--reset-render-state)