[BUG] SEVERITY: CRITICAL — THIS IS BLOCKING PRODUCTIVE WORK AND SHOULD BE ADDRESSED IMMEDIATELY
Preflight Checklist
- [x] I have searched existing issues and this hasn't been reported yet
- [x] This is a single bug report (please file separate reports for different bugs)
- [x] I am using the latest version of Claude Code
What's Wrong?
Here's the bug report in English:
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🚨 CRITICAL BUG REPORT — URGENT ACTION REQUIRED 🚨
⚠️ SEVERITY: CRITICAL — THIS IS BLOCKING PRODUCTIVE WORK AND MUST BE ADDRESSED IMMEDIATELY ⚠️
Product: Claude macOS Desktop App
Issue type: Severe UI freeze / performance regression / rendering failure
Reproducibility: 100% — persistent and continuous across sessions
---
Summary
The Claude macOS desktop application is exhibiting severe performance degradation and UI unresponsiveness when navigating between chat sessions via the left-hand sidebar. What used to be a fluid, instant interaction in previous versions has now become effectively unusable, making it impossible to work across multiple parallel sessions — which is a core workflow for power users.
Detailed Behavior
- Session switching latency: Clicking on any session in the left sidebar to switch context results in extreme delays before the session loads and becomes interactive. This occurs even when the target sessions are idle (no active streaming, no running tools, no pending operations).
- Full UI thread blocking: Upon clicking to open/view any session, the entire application becomes completely unresponsive for tens of seconds. During this freeze:
- No UI element can be clicked or selected
- The sidebar itself is frozen
- Even opening Settings triggers the same blocking behavior
- The app appears to be stuck on the main thread with no responsiveness to user input
- Complete UI disappearance / blank window rendering: Frequently, the entire app interface disappears completely, leaving only an empty window with no UI chrome, no sidebar, no chat view — just a blank canvas. This is a rendering/lifecycle failure that makes recovery impossible without force-quitting.
- Forced app termination: Because of the blank-window failure mode, I am repeatedly forced to quit and relaunch the Claude Mac app just to regain a functional interface. This destroys workflow continuity.
Regression
This behavior is a clear regression. Previous versions of the Claude macOS app handled session switching smoothly and fluidly. The current build has made parallel multi-session workflows practically impossible.
Environment & Ruling Out Local Causes
To preempt any assumption that this is a local resource or connectivity issue — it is not:
- Hardware: MacBook Pro, high-performance configuration, 96 GB RAM
- Network: FTTH fiber connection (high bandwidth, low latency)
- Other applications: No other software on this machine exhibits any comparable slowdown, freezing, or rendering failure. CPU, memory, GPU, and I/O all have ample headroom. This rules out local performance, thermal throttling, memory pressure, or network-related explanations.
- Persistence: The issue is persistent and continuous — it reproduces reliably every session, not intermittently.
The problem is isolated to the Claude Mac app itself, strongly indicating a client-side defect (likely main-thread blocking on session hydration, inefficient IPC/rendering in the Electron/native layer, a memory leak in session state management, or a broken window lifecycle causing the blank-window state).
Suspected Root Cause Areas Worth Investigating
- Main-thread work during session switching (synchronous I/O, heavy re-renders, or large state rehydration on click)
- Session list / conversation history data fetching being blocking rather than async/non-blocking
- Renderer process crashing or detaching, causing the blank-window failure mode
- Memory retention across sessions causing cumulative slowdown
- Possible regression introduced in a recent release — worth bisecting against prior versions
Impact
THIS IS BLOCKING PRODUCTIVE WORK. The inability to rapidly switch between parallel sessions — a core use case for professional users — combined with the forced app restarts caused by the blank-window bug, makes the Mac app currently unfit for serious daily use. PLEASE TREAT AS URGENT.
---
Please escalate to the desktop/client engineering team and confirm receipt. Happy to provide logs, sample timings, screen recordings of the blank-window state, or run diagnostic builds if needed.
What Should Happen?
Here's the bug report in English:
---
🚨 CRITICAL BUG REPORT — URGENT ACTION REQUIRED 🚨
⚠️ SEVERITY: CRITICAL — THIS IS BLOCKING PRODUCTIVE WORK AND MUST BE ADDRESSED IMMEDIATELY ⚠️
Product: Claude macOS Desktop App
Issue type: Severe UI freeze / performance regression / rendering failure
Reproducibility: 100% — persistent and continuous across sessions
---
Summary
The Claude macOS desktop application is exhibiting severe performance degradation and UI unresponsiveness when navigating between chat sessions via the left-hand sidebar. What used to be a fluid, instant interaction in previous versions has now become effectively unusable, making it impossible to work across multiple parallel sessions — which is a core workflow for power users.
Detailed Behavior
- Session switching latency: Clicking on any session in the left sidebar to switch context results in extreme delays before the session loads and becomes interactive. This occurs even when the target sessions are idle (no active streaming, no running tools, no pending operations).
- Full UI thread blocking: Upon clicking to open/view any session, the entire application becomes completely unresponsive for tens of seconds. During this freeze:
- No UI element can be clicked or selected
- The sidebar itself is frozen
- Even opening Settings triggers the same blocking behavior
- The app appears to be stuck on the main thread with no responsiveness to user input
- Complete UI disappearance / blank window rendering: Frequently, the entire app interface disappears completely, leaving only an empty window with no UI chrome, no sidebar, no chat view — just a blank canvas. This is a rendering/lifecycle failure that makes recovery impossible without force-quitting.
- Forced app termination: Because of the blank-window failure mode, I am repeatedly forced to quit and relaunch the Claude Mac app just to regain a functional interface. This destroys workflow continuity.
Regression
This behavior is a clear regression. Previous versions of the Claude macOS app handled session switching smoothly and fluidly. The current build has made parallel multi-session workflows practically impossible.
Environment & Ruling Out Local Causes
To preempt any assumption that this is a local resource or connectivity issue — it is not:
- Hardware: MacBook Pro, high-performance configuration, 96 GB RAM
- Network: FTTH fiber connection (high bandwidth, low latency)
- Other applications: No other software on this machine exhibits any comparable slowdown, freezing, or rendering failure. CPU, memory, GPU, and I/O all have ample headroom. This rules out local performance, thermal throttling, memory pressure, or network-related explanations.
- Persistence: The issue is persistent and continuous — it reproduces reliably every session, not intermittently.
The problem is isolated to the Claude Mac app itself, strongly indicating a client-side defect (likely main-thread blocking on session hydration, inefficient IPC/rendering in the Electron/native layer, a memory leak in session state management, or a broken window lifecycle causing the blank-window state).
Suspected Root Cause Areas Worth Investigating
- Main-thread work during session switching (synchronous I/O, heavy re-renders, or large state rehydration on click)
- Session list / conversation history data fetching being blocking rather than async/non-blocking
- Renderer process crashing or detaching, causing the blank-window failure mode
- Memory retention across sessions causing cumulative slowdown
- Possible regression introduced in a recent release — worth bisecting against prior versions
Impact
THIS IS BLOCKING PRODUCTIVE WORK. The inability to rapidly switch between parallel sessions — a core use case for professional users — combined with the forced app restarts caused by the blank-window bug, makes the Mac app currently unfit for serious daily use. PLEASE TREAT AS URGENT.
---
Please escalate to the desktop/client engineering team and confirm receipt. Happy to provide logs, sample timings, screen recordings of the blank-window state, or run diagnostic builds if needed.
Error Messages/Logs
Steps to Reproduce
Open Claude software from MacOS, start multiple sessions, Claude mode too, with many commands and usage time by time. Click to switch from a session to another and on other icons in the interface, setting and so on. The interface is extremely slow to open internal sessions and pages. Please read the description, thank you
Claude Model
Not sure / Multiple models
Is this a regression?
I don't know
Last Working Version
_No response_
Claude Code Version
Claude 1.3109.0 (35cbf6) 2026-04-16T20:32:01.000Z
Platform
Anthropic API
Operating System
macOS
Terminal/Shell
Other
Additional Information
_No response_
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