feat: add ANTHROPIC_DEFAULT_FABLE_MODEL env vars + hide unsupported models in /model picker when CLAUDE_CODE_USE_BEDROCK=1

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

When CLAUDE_CODE_USE_BEDROCK=1 and org uses Application Inference Profile ARNs (policy: no direct Anthropic API), the /model picker still shows Fable 5. Selecting it writes "model":
"eu.anthropic.claude-fable-5" into ~/.claude/settings.json, which calls Anthropic directly — bypassing Bedrock entirely. Result: 400 error ("data retention mode 'default' is not
available for this model") and a policy violation.

Additionally, there is no ANTHROPIC_DEFAULT_FABLE_MODEL env var, so even if the org creates a Bedrock inference profile for Fable, there is no supported way to wire it up — unlike
Sonnet/Haiku/Opus which all have ANTHROPIC_DEFAULT_*_MODEL env vars.

What Should Happen?

1. ANTHROPIC_DEFAULT_FABLE_MODEL (+ _NAME, _DESCRIPTION) env vars should exist, matching the pattern for the other three models.

1. When CLAUDE_CODE_USE_BEDROCK=1, the /model picker should only show models that have a corresponding ANTHROPIC_DEFAULT_*_MODEL ARN configured. Selecting a model with no ARN should

be blocked or show a warning — it should never write a bare model ID string into settings.json.

Error Messages/Logs

Steps to Reproduce

1. Set CLAUDE_CODE_USE_BEDROCK=1 in ~/.claude/settings.json env block
2. Configure ANTHROPIC_DEFAULT_SONNET_MODEL, _HAIKU_MODEL, _OPUS_MODEL with Bedrock ARNs (do NOT set any Fable ARN — none exists)
3. Run Claude Code and type /model
4. Observe: "Fable 5" appears in the picker
5. Select Fable 5
6. Observe: settings.json now contains "model": "eu.anthropic.claude-fable-5"
7. Send any message
8. Observe: 400 error — request goes to Anthropic direct instead of Bedrock

Claude Model

Other

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.1.170

Platform

AWS Bedrock

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_