diff --git a/ROADMAP.md b/ROADMAP.md
index ed35121..a6d55df 100644
--- a/ROADMAP.md
+++ b/ROADMAP.md
@@ -132,6 +132,7 @@ Ranked; estimates in Opus 5.5 agent-hours. Detail and the full beta-gate list in
 
 | Date | What landed |
 |---|---|
+| 2026-10-12 | SUBTOTAL(109) over hidden rows recalculates after Row Height, AutoFit Row Height and Ungroup reveal rows (found by the command-sequence fuzz) |
 | 2026-10-12 | Page Layout view: drag the margin edges on the rulers to set the page margins (resize cursor, live preview, value tooltip, one undo step, Esc cancels) (#792) |
 | 2026-10-12 | Forecast Sheet gets Forecast Start: begin the forecast inside the history to compare it with the actuals (#785) |
 | 2026-10-12 | Ink strokes save as unfilled DrawingML paths and reopen as editable ink with their points, colour and width; icons in #551 remain a follow-up |
diff --git a/crates/engine/src/cmd/data.rs b/crates/engine/src/cmd/data.rs
index 1e4b1d0..311121e 100644
--- a/crates/engine/src/cmd/data.rs
+++ b/crates/engine/src/cmd/data.rs
@@ -1158,6 +1158,7 @@ fn group(s: &mut Session, p: &Json, on: bool) -> Result<Json> {
         {
             e.collapsed = false;
         }
+        cx.structural = true; // ungrouping reveals hidden rows: SUBTOTAL(10x) depends on it
         Ok(Json::Null)
     })
 }
diff --git a/crates/engine/src/cmd/format.rs b/crates/engine/src/cmd/format.rs
index c3c7fb4..3ed8ac1 100644
--- a/crates/engine/src/cmd/format.rs
+++ b/crates/engine/src/cmd/format.rs
@@ -963,6 +963,7 @@ fn row_height(s: &mut Session, p: &Json) -> Result<Json> {
                 e.custom = true;
             }
         }
+        cx.structural = true; // setting a height shows or hides rows: SUBTOTAL(10x) depends on it
         Ok(Json::Null)
     })
 }
@@ -1077,6 +1078,7 @@ fn autofit_rows(s: &mut Session, p: &Json) -> Result<Json> {
             }
             cx.fit_rows.extend((a..=b).map(|r| (si, r)));
         }
+        cx.structural = true; // autofit reveals hidden rows: SUBTOTAL(10x) depends on it
         Ok(Json::Null)
     })
 }
diff --git a/crates/engine/src/tests.rs b/crates/engine/src/tests.rs
index 33b5228..de592f5 100644
--- a/crates/engine/src/tests.rs
+++ b/crates/engine/src/tests.rs
@@ -3041,6 +3041,19 @@ fn a_decrypted_workbook_never_overwrites_its_encrypted_original() {
 }
 
 #[test]
+fn subtotal_109_recalculates_when_row_height_or_autofit_reveals_rows() {
+    let mut s = s();
+    s.execute("range.setValues", json!({"range": "A1", "values": [[1], [2], [4], [8]]})).unwrap();
+    s.execute("cell.set", json!({"cell": "C1", "input": "=SUBTOTAL(109,A1:A4)"})).unwrap();
+    s.execute("home.hideRows", json!({"rows": "2:3"})).unwrap();
+    assert_eq!(v(&s, "C1"), Value::Number(9.0));
+    // A non-zero height unhides the rows (the fuzz found the stale SUBTOTAL).
+    s.execute("home.rowHeight", json!({"rows": "2:3", "height": 60.0})).unwrap();
+    assert_eq!(v(&s, "C1"), Value::Number(15.0));
+    s.execute("home.hideRows", json!({"rows": "2:3"})).unwrap();
+    assert_eq!(v(&s, "C1"), Value::Number(9.0));
+    s.execute("home.autofitRowHeight", json!({"rows": "2:3"})).unwrap();
+    assert_eq!(v(&s, "C1"), Value::Number(15.0));
 fn paste_special_validation_copies_the_rule() {
     let mut s = s();
     let ok = |s: &mut Session, cell: &str, input: &str| s.execute("data.validate", json!({"cell": cell, "input": input})).unwrap()["ok"] == true;