[BUG] Fable 5 [1m] prompts 'usage credits required' during active 1M promo window (Jul 17, promo extended to Jul 19)

Description

With the saved default model claude-fable-5[1m] (set via /model → Fable 5), Claude Code prompted for Usage Credits on 2026-07-17, even though the account's 1M-context promotion had been extended by Anthropic through 2026-07-19. Switching between opus[1m] and fable[1m] in the same environment, only Fable produced the credits prompt.

Environment

• Claude Code 2.1.207 (CLI), devcontainer on Debian 12 / WSL2 (linux)
• ~/.claude/settings.json: "model": "claude-fable-5[1m]"
• Account has the 1M-context Usage Credits promotion, extended through 2026-07-19

Corroborating observation (matches #74562)

The /model confirmation label differs between models in this same session:

• /model → Opus: "Set model to Opus 4.8 (1M context)" — 1M label present
• /model → Fable: "Set model to Fable 5" — 1M label absent

This is exactly the symptom documented in #74562 (sonnet[1m]/fable[1m] aliases do not apply the 1M context window; only opus[1m] works). It suggests the Fable credits prompt may share a root cause: if the client mis-resolves fable[1m] when checking entitlements, the promo entitlement would not match and the user gets a credits prompt despite a valid promo.

Possibly related

• #74562 — sonnet[1m] / fable[1m] aliases do not apply 1M context (only opus[1m] works)
• #67650 — internal quota probe sends model ID with literal [1m] suffix → 404 not_found_error
• #65359 — 'usage credits required for 1M context' (different trigger: auto-switch on long sessions; already marked duplicate)

Expected behaviour

With an active 1M promotion, selecting Fable 5 with the [1m] alias should not prompt for usage credits (or, if the promotion legitimately does not cover Fable 1M, the prompt should say so rather than appearing as a generic credits requirement two days before the promo's end).

Caveat

We cannot see the account-side promo scoping from the client, so we cannot fully rule out that the promotion covers opus[1m] only — but the missing "(1M context)" label for Fable in /model points to client-side alias resolution as the likelier culprit. Happy to provide account details to triage privately.