[Bug] Claude Code performance degradation after recent update

Found 3 possible duplicate issues:

1. https://github.com/anthropics/claude-code/issues/19056
2. https://github.com/anthropics/claude-code/issues/17590
3. https://github.com/anthropics/claude-code/issues/17563

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🤖 Generated with Claude Code

I had the same problem since sunday, I canceled my plan and requested a refund.

제 것은 멍청해졌습니다. 확연히 멍청해졌습니다. 이전 Sonnet 4.5보다 Opus 4.5가 멍청하고, 토큰만 더 많이 소모합니다.

downgraded to v2.1.2 which seems to be working fine for now

how do you downgrade?

using Claude Code itself and explicitly asking it to disable auto-update.

It triggered these commands:

• npm install -g @anthropic-ai/claude-code@2.1.2
• which claude
• Claude --version

You can use the command line: curl -fsSL https://claude.ai/install.sh | bash -s -- 2.1.2

+1

It is still slow with version 2.1.2. It isn't the terminal application that is slow. It's the Anthropic servers. Unusable. Same issue with the VS Code extension.

Claude models in Antigravity are fast, i believe they're on Google's servers.

@benji-farquhar No, then you have a different issue. Claude Code definitely gets slow with sessions that have large terminal outputs. Reverting to 2.1.2 solves that issue for me.

@slhck Okay. Lucky you then.

I see that the node version is still more fluid than the native one.

+1
Even entering characters occasionally starts to lag and slow down, just like the entire Claude code.

It runs super slow, I am suspicious of the API rate issue, after checking, the LLM API is working quick with opencode, but every slow with claude code. (claude v2.1.81)

Also seeing on .81 lots of red text and not starting to process and think for minutes sometimes.

I created a .cloudignore and now is a bit faster, maybe helps someone. Using the native version .81

Performance degradation after updates can have several causes. Here's a diagnostic and mitigation checklist:
Diagnosis — check which part is slow:

claude --version
time claude --version  # Should be < 2 seconds
time curl -s https://api.anthropic.com/v1/messages -H "x-api-key: test" -H "anthropic-version: 2023-06-01" -d '{}' > /dev/null

Workaround 1 — Clear cache and restart:

rm -rf ~/.claude/cache/
rm -rf ~/.claude/Code\ Cache/
claude

Stale cache can slow down startup and tool operations.
Workaround 2 — Reduce context size:
Long conversations slow down every API call (more tokens = more processing). Compact regularly:

/compact

Or start fresh sessions for new tasks.
Workaround 3 — Disable unused MCP servers:
Each MCP server adds overhead. Remove any you're not actively using from settings.json.
Workaround 4 — Check for background processes:

ps aux | grep claude

Kill any orphaned processes.
Workaround 5 — Increase system resources:

export NODE_OPTIONS="--max-old-space-size=8192"
claude

Workaround 6 — Monitor with a hook:

{
  "hooks": {
    "PostToolUse": [
      {
        "matcher": "*",
        "hook": "bash -c 'echo \"[$(date +%H:%M:%S)] tool done\" >> /tmp/claude-perf.log'"
      }
    ]
  }
}

Check /tmp/claude-perf.log to see how long between tool calls.
If the slowness is API-side (not local): Check status.anthropic.com. Max plan users sometimes experience slower responses during high-load periods.