fix(terminal): stop re-running composer prompt on user-initiated splits (#778)

src/renderer/src/components/terminal-pane/pty-connection.ts

@@ -19,13 +19,12 @@ export function connectPanePty(
   let disposed = false
   let connectFrame: number | null = null
   let startupInjectTimer: ReturnType<typeof setTimeout> | null = null
-  // Why: setup commands must only run once — in the initial pane of the tab.
-  // Capture and clear the startup reference synchronously so that panes
-  // created later by splits or layout restoration cannot re-execute the
-  // setup script, which would be confusing and potentially destructive.
-  // Note: this intentionally mutates `deps` so the caller's object no
-  // longer carries the startup payload — preventing any later consumer
-  // from accidentally replaying it.
+  // Why: startup commands must only run once — in the pane they were
+  // targeted at. Capture `deps.startup` into a local and clear the field on
+  // the (already spread-copied) `deps` so nothing else inside this function
+  // can accidentally re-read it. The caller is responsible for clearing its
+  // own outer reference, since `deps` here is a shallow copy and our
+  // mutation does not propagate back.
   const paneStartup = deps.startup ?? null
   deps.startup = undefined
 

src/renderer/src/components/terminal-pane/use-terminal-pane-lifecycle.ts

@@ -293,6 +293,18 @@ export function useTerminalPaneLifecycle({
           ...ptyDeps,
           restoredLeafId
         })
+        // Why: connectPanePty receives a spread copy of ptyDeps, so the
+        // `deps.startup = undefined` it performs internally only clears its
+        // local copy. If we don't also clear the outer ptyDeps.startup here,
+        // a later user-initiated splitPane (e.g. Cmd+D, context-menu "Split
+        // Right") fires onPaneCreated again with the original startup still
+        // attached — which re-runs the initial composer prompt in the newly
+        // created pane. Clearing here ensures the initial-startup payload is
+        // consumed exactly once, by the first pane. Setup/issue splits
+        // inject their own payload via splitPaneWithOneShotStartup, which
+        // sets deps.startup immediately before splitPane() and is therefore
+        // unaffected by this clear.
+        ptyDeps.startup = null
         panePtyBindings.set(pane.id, panePtyBinding)
         scheduleRuntimeGraphSync()
         queueResizeAll(true)