[Bug]: Usage cost ignores Fast mode pricing #6306

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Area

apps/server

Steps to reproduce

1. Enable Fast mode for a Codex or Claude provider session in T3 Code.
2. Run one or more turns that are served in Fast mode.
3. Open the Usage page.
4. Compare the displayed raw token cost with the provider’s Fast/Priority token rates.

Expected behavior

Fast mode should use the provider’s applicable Fast/Priority rates.
Standard responses should use standard rates, including when the provider falls back to standard processing.

Actual behavior

The Usage page prices all transcript usage at the base rate, so Fast mode price is under-reported

Impact

Cosmetic issue

Version or commit

main @ 5a84614

Environment

All T3 Code server environments using Fast mode for Codex or Claude

Logs or stack traces

Screenshots, recordings, or supporting files

No response

Workaround

Ignore as inconsequential, or use the provider dashboard if the real number is important