Fix Claude AI 'Capacity Limit Reached' & Message Errors

Updated: 11/29/2025

You are in the middle of a research session, you hit enter, and Claude stops responding. A red error appears: 'Message not sent. You have reached the capacity limit for this conversation' or simply 'Overloaded'. Unlike ChatGPT, Claude has a very specific 'context window' limit per chat. Once a single conversation gets too long, the AI physically cannot hold any more tokens in its short-term memory, causing this error.

Table of Contents

Method 1: Start a New Chat (The Context Fix)

Claude's token limit (roughly 100k-200k tokens) includes every word you and the AI have typed in the current session. Once full, it breaks.

Step 1: Copy Prompt

Copy your last unanswered prompt to your clipboard.

Step 2: Reset

Click the Claude Logo in the top left to return to the dashboard. Click 'New Chat'.

Step 3: Paste

Paste your prompt. Since the memory is fresh, the error will disappear instantly.

Method 2: Clear Site Cookies

If you get 'Unexpected Error' on login, your authentication token is stale.

  • Chrome: Click the Lock icon in the URL bar > Site Settings > Delete Data.
  • Edge: Click the Lock icon > Cookies > Remove claude.ai.
Tip: You will need to log in again via email code after doing this.

Method 3: Disable 'Dark Reader' Extensions

Anthropic's UI uses dynamic rendering that conflicts with forced Dark Mode extensions.

If the chat box disappears or the 'Send' button is grayed out, disable Dark Reader or Midnight Lizard for the claude.ai domain. Refresh the page.