App-wide input lag on Windows 11 Desktop (build 1.10628.0.0) - renderer main-thread blocking; continuation of closed #55149

Still happening on the latest build (1.10628.0.0). Per the stale-close note on #55149 ("open a new issue if still relevant"), filing fresh with diagnostics.

Environment

• Claude Desktop 1.10628.0.0 (MSIX), Windows 11 Pro
• Ryzen 7 7800X3D, RTX 5080, 32 GB DDR5; during the lag the system is idle (~12 GB RAM free, CPU ~19%)

Symptom

• Every keystroke lags ~1-2s to appear - in both the slash-command picker and normal message input
• Switching between conversations is slow; app-wide, independent of conversation content/length

Same root cause as #55149 (renderer main-thread blocking), NOT #26302

• #26302's root cause is Cowork VM + GPU compositing/G-Sync - there, disabling hardware acceleration or G-Sync fixes it.
• In my case, disabling hardware acceleration makes it WORSE, and Task Manager shows the GPU engine idle while typing (it only wakes on tab switch). So this is main-thread bound, not GPU compositing - matching #55149's StorageArea/IndexedDB analysis.

Ruled out via diagnostics

• Latest build (auto-updated same day); Clear Cache + full reinstall: no lasting change
• Single monitor only (Win+P "PC screen only"): no change - not multi-monitor/mixed-refresh
• Disabled ALL MCP servers/connectors AND removed all custom skills: no change - not tool/state volume
• Cowork idle (18 MB), system resources healthy, fresh/empty conversation identical
• GPU acceleration confirmed working (wakes on tab switch) but uninvolved in typing

Looks like the LocalStorage/IndexedDB main-thread blocking from #55149 persists on 1.10628. Happy to capture a performance trace if useful.

Related: #55149 (closed stale, same root cause + traces), #26302 (similar symptom, different GPU-side root cause).

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Issue written by Claude Code, diagnosed collaboratively with the reporter.