Desktop App (Claude for Mac): Stale/ghost content appears transiently mid-session without compaction

Description

In the Claude for Mac Desktop app, stale progress notes and context fragments appear transiently below actual responses mid-session. This happens without compaction being triggered — no "This session is being continued..." block is present. The stale content disappears after a short time, making it a transient rendering artifact.

Behavior

• Mid-session, after Claude responds to a prompt, stale content (progress notes, narration from earlier in the session) briefly appears below the actual response
• The stale content is not related to the current task — e.g., session was about a dev server but random earlier notes appeared
• The content disappears after a while without any user action
• This is not triggered by compaction — no compaction summary block is present

Expected behavior

Only the current response should render below the user's prompt. No stale content from earlier in the session should appear.

Environment

• Platform: Claude for Mac (Desktop app)
• Hooks: SessionStart (compact matcher), PreToolUse (Bash), PostToolUse (Bash)
• Plugins: github, code-review, typescript-lsp, context7, frontend-design, playwright, vercel

Notes

• Distinct from #1913 (terminal flickering) and #23253 (TUI text cleanup) — those are CLI terminal issues. This is Desktop app specific.
• The transient nature (appears then disappears) suggests a rendering/state caching issue in the Desktop app's conversation view.