Extended usage limit exceeded all at once without progressive billing feedback (Opus 1M context)

Bug Description

I enabled the extended usage feature as a test, setting a monthly spending limit of R$10 (BRL). While using Claude Code CLI with the Opus model (1 million token context), the following issues occurred:

Problems

1. Spending limit completely ignored: The system charged R$27.36 against a R$10 limit — that's 274% of the set limit — without stopping or warning during usage.

1. No progressive billing feedback: Unlike other models that show billing progression during use, the Opus 1M token context charged everything at once after the session, with no intermediate feedback or warnings that the limit was being approached or exceeded.

1. No rate limiting or session interruption: The system should have stopped or warned when approaching the R$10 limit, but instead allowed the full charge to go through in a single shot.

Expected Behavior

• The system should respect the configured spending limit and either stop or warn before exceeding it
• Billing progression should be shown during usage (as it works with other models), not charged all at once after the fact
• When approaching the limit, there should be a clear warning or graceful degradation

Environment

• Tool: Claude Code CLI
• Model: Opus (1M token context window)
• Spending Limit Set: R$10/month
• Amount Charged: R$27.36 (274% over limit)
• Balance: R$247.63
• Auto-reload: Disabled

Screenshot

The screenshot below shows the billing page after the session, confirming the overage:

<img width="1005" height="372" alt="Image" src="https://github.com/user-attachments/assets/44b114de-6a26-4b3a-87a9-1f3528fb3534" />

Steps to Reproduce

1. Enable "Extended usage" (Uso extra) in billing settings
2. Set monthly spending limit to a low value (e.g., R$10)
3. Use Claude Code CLI with Opus model and large context (1M tokens)
4. Observe that no progressive billing feedback is shown during use
5. After session ends, check billing — limit was exceeded without any warning

Impact

This is a billing/trust issue. Users who set spending limits expect them to be enforced. Being charged 274% of the configured limit without warning undermines confidence in the billing controls.