[BUG] Opus 4.6 returns "Rate limit reached" mid-session on Claude Pro plan

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?

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Title: Opus 4.6 returns "Rate limit reached" mid-session on Claude Pro plan

Description:

I was using Claude Code (v2.1.76) with Opus 4.6 (1M context) in an ongoing project session. After a period of inactivity, I started a new session and immediately
received a rate limit error on the very first prompt — before any significant token usage in the new session.

Steps to Reproduce:

1. Use Claude Code with Opus 4.6 on Claude Max plan across multiple sessions
2. Start a new session
3. Send the first message

Expected Behavior:
Opus 4.6 should be available at the start of a new session without hitting rate limits immediately.

Actual Behavior:
API Error: Rate limit reached
Had to switch to Sonnet 4.6 via /model command to continue working.

Environment:

• Claude Code version: v2.1.76
• Model: claude-opus-4-6 (1M context)
• Plan: Claude Pro
• OS: WSL2 (Ubuntu) on Windows 11
• Shell: bash

Impact:
Users who rely on Opus for complex tasks are forced to switch models mid-workflow without warning, disrupting continuity.

What Should Happen?

! claude --version
⎿  2.1.76 (Claude Code)

❯ /model
⎿ Set model to Opus 4.6 (1M context) (default)

❯ 2.1.76 (Claude Code)
⎿  API Error: Rate limit reached

Error Messages/Logs

API Error: Rate limit reached

Steps to Reproduce

1. Subscribe to Claude Pro plan
2. Open Claude Code v2.1.76
3. Use Opus 4.6 (1M context) across multiple sessions over the course of a day
4. Start a new session (after a period of inactivity)
5. Send the very first message in the new session

Note: The rate limit error occurs immediately on the first prompt, before any significant token usage in the new session. The error provides no information about when
the limit will reset.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.76 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

WSL (Windows Subsystem for Linux)

Additional Information

_No response_