diff --git a/src/renderer/src/components/terminal-pane/pty-connection/pty-input-forward.ts b/src/renderer/src/components/terminal-pane/pty-connection/pty-input-forward.ts
index 8d91e498dea..6ff7c244443 100644
--- a/src/renderer/src/components/terminal-pane/pty-connection/pty-input-forward.ts
+++ b/src/renderer/src/components/terminal-pane/pty-connection/pty-input-forward.ts
@@ -23,6 +23,7 @@ import { TERMINAL_FOCUS_IN_SEQUENCE, TERMINAL_FOCUS_OUT_SEQUENCE } from './foreg
 import { isRemoteRuntimePtyId } from './paired-parked-terminal-restore'
 import { isCodexPaneStale } from './codex-pane-stale'
 import { installTerminalSelectionFitGuard } from '../terminal-selection-fit-guard'
+import { initializePaneGeometry, readPaneSize } from './read-pane-size'
 
 import type { ConnectPanePtySession } from './connect-pane-pty-session'
 
@@ -308,12 +309,9 @@ export function installPtyInputForward(session: ConnectPanePtySession): void {
         if (reattachCols > 0 && reattachRows > 0) {
           session.transport.resize(reattachCols, reattachRows)
         }
-        // Why: POSIX only sends SIGWINCH on an actual dimension change; signal explicitly so restored TUIs repaint at the correct cursor after replay.
         if (!isRemoteRuntimePtyId(reattachPtyId)) {
           window.api.pty.signal(reattachPtyId, 'SIGWINCH')
         }
-        // Why here: a deferred reveal resolves the fit handle as incomplete, so an awaited
-        // reassertion at the call site would never run for that path.
         if (session.deps.isVisibleRef.current) {
           session.ptySizeReassertion.request({ fit: false })
         }
@@ -341,8 +339,6 @@ export function installPtyInputForward(session: ConnectPanePtySession): void {
     )
   }
   session.scheduleForegroundGridDriftCheck = (force = false): void => {
-    // Why: mobile-owned PTYs intentionally keep a non-desktop grid; drift
-    // healing would refit xterm even if resize forwarding is later suppressed.
     if (
       session.disposed ||
       !session.deps.isVisibleRef.current ||
@@ -371,27 +367,12 @@ export function installPtyInputForward(session: ConnectPanePtySession): void {
       ) {
         return
       }
-      // Why: xterm cell metrics can settle after the DOM box stops resizing, so
-      // ResizeObserver never fires even though FitAddon now proposes more cols.
       requestStablePaneFit(session.pane as ManagedPaneInternal, () =>
         session.ptySizeReassertion.request({ fit: false })
       )
     })
   }
 
-  // Why: observe the outer pane as the layout signal for both desktop drift
-  // healing and mobile take-back. Normal desktop panes compare xterm against
-  // the PTY's applied size; mobile-fit panes only report desktop geometry so
-  // the parked phone-sized PTY is not resized. See docs/mobile-fit-hold.md.
-  session.pendingGeometryReportRaf = null
-  session.lastObservedDesktopGrid = null
-  session.readPaneSize = (): { width: number; height: number } | null => {
-    if (typeof session.pane.container.getBoundingClientRect !== 'function') {
-      return null
-    }
-    const rect = session.pane.container.getBoundingClientRect()
-    return { width: rect.width, height: rect.height }
-  }
-  session.lastObservedPaneSize = session.readPaneSize()
-  session.pendingPaneGeometryChanged = false
+  session.readPaneSize = () => readPaneSize(session)
+  initializePaneGeometry(session)
 }
diff --git a/src/renderer/src/components/terminal-pane/pty-connection/read-pane-size.ts b/src/renderer/src/components/terminal-pane/pty-connection/read-pane-size.ts
new file mode 100644
index 00000000000..bf316160926
--- /dev/null
+++ b/src/renderer/src/components/terminal-pane/pty-connection/read-pane-size.ts
@@ -0,0 +1,18 @@
+import type { ConnectPanePtySession } from './connect-pane-pty-session'
+
+export function readPaneSize(
+  session: ConnectPanePtySession
+): { width: number; height: number } | null {
+  if (typeof session.pane.container.getBoundingClientRect !== 'function') {
+    return null
+  }
+  const rect = session.pane.container.getBoundingClientRect()
+  return { width: rect.width, height: rect.height }
+}
+
+export function initializePaneGeometry(session: ConnectPanePtySession): void {
+  session.pendingGeometryReportRaf = null
+  session.lastObservedDesktopGrid = null
+  session.lastObservedPaneSize = readPaneSize(session)
+  session.pendingPaneGeometryChanged = false
+}
diff --git a/src/renderer/src/components/terminal-pane/terminal-selection-fit-guard.ts b/src/renderer/src/components/terminal-pane/terminal-selection-fit-guard.ts
index 0130aac82c6..f9f6befc6bb 100644
--- a/src/renderer/src/components/terminal-pane/terminal-selection-fit-guard.ts
+++ b/src/renderer/src/components/terminal-pane/terminal-selection-fit-guard.ts
@@ -37,17 +37,23 @@ export function installTerminalSelectionFitGuard(
     active = false
   }
 
-  terminalElement?.addEventListener('mousedown', handleMouseDown, true)
-  ownerDocument?.addEventListener('mouseup', handleMouseUp, true)
-  ownerWindow?.addEventListener('blur', clear)
+  if (terminalElement && typeof terminalElement.addEventListener === 'function') {
+    terminalElement.addEventListener('mousedown', handleMouseDown, true)
+  }
+  if (ownerDocument && typeof ownerDocument.addEventListener === 'function') {
+    ownerDocument.addEventListener('mouseup', handleMouseUp, true)
+  }
+  if (ownerWindow && typeof ownerWindow.addEventListener === 'function') {
+    ownerWindow.addEventListener('blur', clear)
+  }
 
   return {
     isActive: () => active,
     dispose: () => {
       clear()
-      terminalElement?.removeEventListener('mousedown', handleMouseDown, true)
-      ownerDocument?.removeEventListener('mouseup', handleMouseUp, true)
-      ownerWindow?.removeEventListener('blur', clear)
+      terminalElement?.removeEventListener?.('mousedown', handleMouseDown, true)
+      ownerDocument?.removeEventListener?.('mouseup', handleMouseUp, true)
+      ownerWindow?.removeEventListener?.('blur', clear)
     }
   }
 }