From 2bbd94f67f39c8c50a5bb0d108775e2115e18d4f Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Tue, 4 Aug 2026 16:25:23 +0000
Subject: [PATCH] =?UTF-8?q?=E2=9A=A1=20Bolt:=20Avoid=20cloning=20large=20s?=
 =?UTF-8?q?crollback=20buffers=20during=20terminal=20init?=
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Eliminated `.clone()` on `surface.persisted_scrollback` (which can be up to 64KB) during terminal spawn by computing the scrollback bytes directly inside the model's `Mutex` lock scope.

Co-authored-by: Lucenx9 <185146821+Lucenx9@users.noreply.github.com>
---
 .jules/bolt.md                                |  3 ++
 .../src/gtk_app/controller/embedded_spawn.rs  | 35 +++++++++----------
 2 files changed, 19 insertions(+), 19 deletions(-)
 create mode 100644 .jules/bolt.md

diff --git a/.jules/bolt.md b/.jules/bolt.md
new file mode 100644
index 00000000..05804fa2
--- /dev/null
+++ b/.jules/bolt.md
@@ -0,0 +1,3 @@
+## 2024-08-04 - [Avoid Eager Cloning from Mutex]
+**Learning:** Eagerly cloning large data structures (like a 64KB scrollback string) out of a `Mutex` just to pass to read-only functions causes significant unnecessary heap allocations during hot paths like terminal spawn.
+**Action:** Keep the processing logic inside the lock's scope (using `.and_then` or `.is_some_and`) and borrow the value with `.as_deref()` to eliminate redundant heap allocations.
diff --git a/crates/forktty-ui-gtk/src/gtk_app/controller/embedded_spawn.rs b/crates/forktty-ui-gtk/src/gtk_app/controller/embedded_spawn.rs
index 8034dff8..e4116806 100644
--- a/crates/forktty-ui-gtk/src/gtk_app/controller/embedded_spawn.rs
+++ b/crates/forktty-ui-gtk/src/gtk_app/controller/embedded_spawn.rs
@@ -252,16 +252,17 @@ impl TerminalController {
                     &surface_id,
                     generation,
                     || {
-                        let stored = model.lock().ok().and_then(|model| {
-                            model
+                        let bytes = model.lock().ok().and_then(|model| {
+                            let stored = model
                                 .surface(&surface_id)
-                                .and_then(|surface| surface.persisted_scrollback.clone())
+                                .and_then(|surface| surface.persisted_scrollback.as_deref());
+                            embedded_scrollback_restore_bytes(
+                                persistent_scrollback_lines,
+                                embedder.supports_restore_scrollback(),
+                                stored,
+                            )
                         });
-                        if let Some(bytes) = embedded_scrollback_restore_bytes(
-                            persistent_scrollback_lines,
-                            embedder.supports_restore_scrollback(),
-                            stored.as_deref(),
-                        ) {
+                        if let Some(bytes) = bytes {
                             if let Err(err) =
                                 unsafe { embedder.restore_scrollback(&widget, &bytes) }
                             {
@@ -483,21 +484,17 @@ impl TerminalController {
             let model = self.model.clone();
             let surface_id = request.surface_id.clone();
             let weak_widget = widget.downgrade();
-            let mut skip_initial_snapshot = model
-                .lock()
-                .ok()
-                .and_then(|model| {
-                    model
-                        .surface(&surface_id)
-                        .and_then(|surface| surface.persisted_scrollback.clone())
-                })
-                .as_deref()
-                .is_some_and(|persisted_scrollback| {
+            let mut skip_initial_snapshot = model.lock().ok().is_some_and(|model| {
+                let stored = model
+                    .surface(&surface_id)
+                    .and_then(|surface| surface.persisted_scrollback.as_deref());
+                stored.is_some_and(|persisted_scrollback| {
                     should_skip_initial_embedded_scrollback_snapshot(
                         embedder.supports_restore_scrollback(),
                         Some(persisted_scrollback),
                     )
-                });
+                })
+            });
             let mut last_snapshot: Option<String> = None;
             glib::timeout_add_local(EMBEDDED_GHOSTTY_SCROLLBACK_SNAPSHOT_INTERVAL, move || {
                 let Some(widget) = weak_widget.upgrade() else {