Model Discovery

Discovery (GET /v1/models) can populate Claude Code’s /model picker automatically — but Claude Code ignores any id that doesn’t begin with claude/anthropic (protocol reference). So a gpt-* id is dropped client-side no matter what; discovery is only useful when you expose a Claude-named alias that a [[routes]] entry rewrites to the real upstream slug:

[[models]]
id = "claude-gpt-5.6-sol-via-codex"     # must begin with claude/anthropic
display_name = "GPT-5.6-Sol (via Codex)"

[[routes]]
model = "claude-gpt-5.6-sol-via-codex"  # the alias Claude Code sends
provider = "codex"
upstream_model = "gpt-5.6-sol"          # real slug forwarded to the ChatGPT backend

Then enable discovery (Claude Code v2.1.129+) and restart shunt + Claude Code:

export CLAUDE_CODE_ENABLE_GATEWAY_MODEL_DISCOVERY=1

The alias appears in /model labeled From gateway; selecting it sends claude-gpt-5.6-sol-via-codex, which shunt routes to codex and rewrites to gpt-5.6-sol.

For gpt-* ids without an alias, use ANTHROPIC_CUSTOM_MODEL_OPTION instead — see Connect Claude Code.

Discovery needs a gateway credential

A claude.ai OAuth login alone won’t trigger discovery. Claude Code only issues the /v1/models request when ANTHROPIC_AUTH_TOKEN, an API key, or an apiKeyHelper is set; under a plain Max/Pro subscription login it sends nothing — no request reaches shunt, no cache is written — even with the flag on. See choosing the credential; claude setup-token is the recommended route.

Debugging

Discovery fails silently (3-second timeout, any redirect counts as failure) and falls back to the cached/built-in list. Run claude --debug and look for [gatewayDiscovery] lines to confirm it ran.