GPT-5.6 Sol Medium depletes Pro 5-hour usage allowance extremely quickly

What version of Codex is running?

Codex desktop app (macOS). Exact build number is not currently visible in the usage dialog.

What subscription do you have?

ChatGPT Pro (€200/month).

Which model were you using?

GPT-5.6 Sol with reasoning effort set to Medium.

What issue are you seeing?

The 5-hour usage allowance is being depleted at an unexpectedly high rate during a very short conversation.

In one short task, the remaining 5-hour allowance dropped from 87% to 76% (11 percentage points). The task consisted mainly of discussing Codex usage limits and performing a small number of GitHub searches. After the initial research, several trivial follow-up messages—without any additional tool calls—each appeared to consume approximately 1 percentage point.

This is especially unexpected because the same user's prior workflow with GPT-5.5 at xhigh reasoning did not show comparable consumption. GPT-5.6 Sol was deliberately used at Medium to reduce usage.

Screenshots were captured showing:

• 78% remaining, reset at 02:22
• 76% remaining, reset at 02:22

Steps to reproduce

1. Use Codex desktop with a ChatGPT Pro subscription.
2. Select GPT-5.6 Sol and Medium reasoning effort.
3. Record the remaining 5-hour allowance.
4. Run a short research conversation involving a few GitHub searches.
5. Continue with several very short follow-up messages without additional tool calls.
6. Recheck the usage dialog after each message.

Expected behavior

A short conversation with Medium reasoning should consume a small and predictable portion of the Pro 5-hour allowance. Trivial follow-up messages should not each consume approximately 1 percentage point.

Usage accounting should also expose enough detail to distinguish model multiplier, input/context tokens, cached input, reasoning tokens, and tool-call overhead.

Actual behavior

• Remaining allowance fell from 87% to 76% during one short task.
• Even short follow-ups without new tool calls appeared to reduce the allowance by about 1 percentage point each.
• The UI provides no breakdown explaining the consumption.

Additional information

Possible areas to investigate:

• GPT-5.6 Sol usage multiplier
• prompt-cache misses or lack of context reuse
• repeated charging of the full accumulated tool context
• reasoning-token accounting
• incorrect or delayed usage reporting

The contrast with GPT-5.5 xhigh under the same user's normal workflow suggests this is not explained by reasoning effort alone.