[FEATURE] Configure custom models in the /model picker

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

I like to switch model versions during Claude Code sessions, depending on the task. There is a built-in /model command to do so, but it is not possible to configure custom models available in the /model picker in the settings file. This is especially relevant when routing through AWS Bedrock rather than the Claude API, which require custom model id's ("us." prefix and ":0" suffix) for all models.

Proposed Solution

Enable the /model picker list to be configurable in the ~/.claude/settings.json or through shell variables.

Alternative Solutions

There are several workarounds possible:

1. Create a local shell variable local HAIKU_MODEL='us.anthropic.claude-haiku-4-5-20251101-v1:0' with the logic to default to this model with an alias claude --haiku
2. Create an environment variable export ANTHROPIC_DEFAULT_HAIKU_MODEL='us.anthropic.claude-haiku-4-5-20251101-v1:0'. I can now select this specific model in two ways: I can either run the /model haiku command, or I can select the "haiku" model in the /model picker selection which will then select the new Bedrock version rather than the default Haiku API model id.

Priority

Medium - Would be very helpful

Feature Category

Configuration and settings

Use Case Example

1. I'm working in a Claude Code session on a codebase
2. I want to switch to quick execution from Opus to Haiku for some testing.
3. I hit /model , but now my options don't show what I need (Haiku is missing, Opus is showing 4.1 and 4.5 with API model id's rather than Bedrock)
4. With the configurable picker, I can instead automatically select what I need.

Additional Context

Here's a screenshot showing Claude suggestion on the implementation:
<img width="1514" height="220" alt="Image" src="https://github.com/user-attachments/assets/a097f6e3-4bd2-41f9-b178-29459115e24b" />