GET /models is not part of the Anthropic API spec and many compatible
proxies do not implement it, causing the connection test to always fail
even with a valid API key.
Switch to POST /v1/messages with max_tokens=1 — the same approach used
for the built-in anthropic provider — and treat any non-401/403 response
as valid, since 400/529 still confirms the key was accepted.
Use node.defaultModel / connection.defaultModel when set so the test
respects the configured model rather than always falling back to
claude-3-haiku-20240307.
Co-authored-by: Rehan Choirul <rehanchrl@users.noreply.github.com>
Co-authored-by: Cursor <cursoragent@cursor.com>
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