High CPU Usage (100%) with AI Assistant (Codex) in IntelliJ IDEA 2026.1

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yinyi147741
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Description:
Using the AI Assistant with Codex in IntelliJ IDEA 2026.1 consistently causes CPU usage to spike to 100%.

After triggering actions like code generation or chat, the IDE becomes slow and sometimes unresponsive. The issue is more noticeable with larger contexts. CPU usage only returns to normal after closing the AI Assistant panel or restarting the IDE.

Expected:
AI features should not significantly impact IDE performance or cause sustained high CPU usage.

Environment:

  • IntelliJ IDEA 2026.1
  • AI Assistant (latest)
  • Model: Codex

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Arina Efremova
Created

Hi there,

The issue could be related to LLM-25345 or LLM-24887. To help me analyze it, please provide:

  1. A CPU snapshot that captures at least 20-30 seconds of IDE performance during high CPU usage: Help | Diagnostic Tools | Start/Stop CPU Usage profiling
    To keep the readings clean and on point, start the profiling only when performance actually drops, and stop it right after you are done.
  2. Recent IDE logs (see How to collect IntelliJ IDE logs for AI Assistant troubleshooting). I will search for concurrent exceptions, check automatically generated application thread dumps and inspect your system environment settings.

Files can be uploaded securely to our server (share the Upload ID here so that I can find it).

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