diff --git a/crates/ty_project/src/db.rs b/crates/ty_project/src/db.rs
index 8e55f2fc7a..27be21058b 100644
--- a/crates/ty_project/src/db.rs
+++ b/crates/ty_project/src/db.rs
@@ -957,6 +957,7 @@ mod tests {
     use ruff_db::system::{DbWithWritableSystem as _, SystemPathBuf, TestSystem};
     use ruff_db::testing::assert_function_query_was_not_run_by_name;
     use ruff_python_trivia::textwrap::dedent;
+    use salsa::plumbing::current_revision;
     use ty_module_resolver::list_modules;
     use ty_python_semantic::Db as _;
 
@@ -996,6 +997,29 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn unrelated_file_change_does_not_advance_revision() -> anyhow::Result<()> {
+        let system = TestSystem::default();
+        let fs = system.memory_file_system().clone();
+        fs.write_files_all([
+            ("/project/main.py", ""),
+            ("/project/unrelated.log", "before"),
+        ])?;
+        let metadata = ProjectMetadata::new("test", SystemPathBuf::from("/project"));
+        let mut db = ProjectDatabase::fallible(metadata, system)?;
+        db.project().files(&db);
+        let revision = current_revision(&db);
+
+        fs.write_file_all("/project/unrelated.log", "after")?;
+        db.apply_changes(&[ChangeEvent::file_content_changed(SystemPathBuf::from(
+            "/project/unrelated.log",
+        ))]);
+
+        assert_eq!(current_revision(&db), revision);
+
+        Ok(())
+    }
+
     #[test]
     fn changed_script_metadata_updates_import_resolution() -> anyhow::Result<()> {
         let system = TestSystem::default();
diff --git a/crates/ty_project/src/files.rs b/crates/ty_project/src/files.rs
index b225872a6b..4e8118be8a 100644
--- a/crates/ty_project/src/files.rs
+++ b/crates/ty_project/src/files.rs
@@ -267,6 +267,7 @@ impl IndexedMut<'_> {
 
     pub(super) fn set_diagnostics(&mut self, diagnostics: Vec<Diagnostic>) {
         self.inner_mut().diagnostics = diagnostics;
+        self.did_change = true;
     }
 
     fn inner_mut(&mut self) -> &mut IndexedInner {
diff --git a/crates/ty_project/src/lib.rs b/crates/ty_project/src/lib.rs
index f6eb4362a3..513bfde3b5 100644
--- a/crates/ty_project/src/lib.rs
+++ b/crates/ty_project/src/lib.rs
@@ -766,6 +766,13 @@ impl Project {
     ///
     /// This is a no-op if the project files haven't been indexed yet.
     fn replace_index_diagnostics(self, db: &mut dyn Db, diagnostics: Vec<Diagnostic>) {
+        // Check before acquiring a mutable index, which cancels pending queries.
+        match self.file_set(db).get() {
+            Index::Lazy(_) => return,
+            Index::Indexed(index) if index.diagnostics() == diagnostics => return,
+            Index::Indexed(_) => {}
+        }
+
         let Some(mut index) = IndexedFiles::indexed_mut(db, self) else {
             return;
         };