"requires usage credits" error for Fable 5 despite all quotas well under limit (session 3%, week 26%, week Fable 24%)

Title: "requires usage credits" error for Fable 5 despite all quotas well under limit (session 3%, week 26%, week Fable 24%)

Body:

Bug description

While using Fable 5 in a Claude Code CLI session, I got a dialog claiming I need to purchase/pay for usage credits. This contradicts the /status output from the very same session, which shows plenty of headroom left on every relevant quota:

Current session
█▌                                                 3% used
Resets 4:50pm (Europe/Berlin)

Current week (all models)
█████████████                                      26% used
Resets Jul 21, 6pm (Europe/Berlin)

Current week (Fable)
████████████                                       24% used
Resets Jul 21, 6pm (Europe/Berlin)

Session cost/usage summary for context:

Total cost:            $53.30
Total duration (API):  1h 56m 10s
Usage by model:
    claude-haiku-4-5:  1.3k input, 51 output, 0 cache read, 0 cache write ($0.0016)
     claude-opus-4-8:  50.1k input, 299.6k output, 23.7m cache read, 1.8m cache write ($36.55)
    claude-sonnet-5:   7.0k input, 111.7k output, 10.2m cache read, 647.6k cache write ($8.13)
     claude-fable-5:   1.1k input, 36.2k output, 2.0m cache read, 238.5k cache write ($8.61)

Steps to reproduce

1. In an active CLI session, switch model to Fable 5 via /model.
2. Continue the conversation — a dialog appears stating usage credits are required / must be purchased.
3. Switch back to Sonnet 5 via /model (confirmed via "Kept model as Sonnet 5") — the same credits-required condition persists in the session, even though /model reports Sonnet is active.
4. Run /status in the same session — all three quota bars (session, weekly all-models, weekly Fable) are well below 100%, as shown above.

Expected behavior
No "usage credits required" prompt should appear while every quota shown in /status has headroom remaining. If Fable 5 draws from a separate, unlisted credit pool distinct from the weekly Fable bar shown in /status, that pool and its remaining balance should be surfaced somewhere — currently there is no way to see why it thinks credits are needed.

Environment

• Claude Code CLI
• Session includes model switches: Fable 5 → Sonnet 5 (confirmed via /model)
• Web interface (claude.ai) usage view for Fable shows 24% used, consistent with the CLI's own /status, further confirming the credits-required dialog is inconsistent with all visible usage data.

Impact
Blocks continued use of the session/model despite no quota being exhausted; inconsistent messaging between the credits dialog, /status, and the web usage view is confusing and makes it unclear whether this is a real billing block or a display/logic bug.