[macOS][Computer History] Apple Mail message selection and scrolling lag; pausing history restores responsiveness

What version of the Codex App are you using (From “About Codex” dialog)?

Codex Desktop 26.901.51231 (build 8109), read from the installed app bundle.

What subscription do you have?

Not provided.

What platform is your computer?

• macOS 26.6.2 (25G83)
• uname -mprs: Darwin 25.6.0 arm64 arm
• Apple Mail 16.0 (3864.700.51.1.1)

What issue are you seeing?

With Computer History running, Apple Mail has noticeable input and scrolling delays:

• Clicking a message highlights its row with a delay; displaying its contents takes longer still.
• A trackpad scroll gesture initially does nothing, then scrolling starts approximately one second later (subjective timing, not instrumented).
• The delay persists with the message preview pane hidden and conversation grouping disabled.
• Two email accounts are connected, including Google. Both show delays, although one seems more affected.
• Other applications do not show the same scrolling delay.

Restarting Mail or rebooting the Mac had not resolved this longstanding symptom.

The following manual comparisons were performed:

1. Quitting Codex eliminated the delay.
2. Launching Codex again brought the delay back.
3. Pausing Computer History, while keeping Codex open, made the Mail interface immediately responsive again.

What steps can reproduce the bug?

On the affected setup:

1. Run Codex Desktop with Computer History active.
2. Open Apple Mail and display a message list.
3. Select different messages and scroll the list using the trackpad.
4. Observe delayed row selection and delayed onset of scrolling.
5. Pause Computer History without quitting Codex.
6. Repeat the same Mail interactions; they become responsive.

The close/reopen Codex comparison and the active-to-paused Computer History comparison were observed. A separate pause/resume Computer History cycle has not yet been tested.

What is the expected behavior?

Background Computer History collection should not cause noticeable input latency or scrolling stalls in Apple Mail. Pausing the feature should not be necessary for responsive interaction with the message list.

Additional information

A 40-second sample Mail capture was collected, and the user confirmed the delay occurred during that capture. The main-thread profile includes the following abbreviated ancestor/descendant chain:

mshMIGPerform
  _XCopyHierarchy
    _AXXMIGCopyHierarchy
      __AXCopyAttributeValueForHierarchy
        ...
        -[NSTableViewCellMockElement accessibilityColumnIndexRangeAttribute]
          -[NSTableViewCellMockElement isFullRowViewCell]
            -[NSTableRowData rowViewAtRow:createIfNeeded:]
              -[NSTableRowData _preparedRowViewForRow:storageHandler:]
                -[NSTableRowData _initializeRowView:atRow:]
                  ...
                  -[NSTableView makeViewWithIdentifier:owner:]
                    ...
                    -[RichMessageCellView initWithCoder:]

This suggests accessibility hierarchy collection is causing Mail to materialize message-list row views on its main thread. The sample alone does not identify the requesting process or establish the duration of an individual stall; the Computer History pause test provides the behavioral link. No paired profile with Computer History paused was captured.

Basic resource checks did not show system-wide CPU saturation or swap use: overall CPU was approximately 79–86% idle in subsequent top intervals, and swap usage was zero in the earlier check. Approximately 421 GiB of disk space was available.

Potentially related:

• #38873 — Accessibility traversal freezes IntelliJ IDEA's Git Log table. This report concerns Apple Mail and includes a successful Computer History pause comparison.
• #38562 — Computer History causes macOS UI/input hitching. Here, the observed delay was confined to Mail.

Workaround: keep Computer History paused.

No raw logs, email contents, account addresses, screenshots, or session transcripts are attached. The stack excerpt above contains only diagnostic symbols.

Start with the reported 40-second sample Mail capture and reproduce the interaction with Computer History active, then compare it while history is paused. Trace the accessibility hierarchy path through mshMIGPerform and NSTableViewCellMockElement to determine whether collection causes the delay; done means Mail selection and scrolling stay responsive while collection remains active.