Fix "There's an issue with the selected model" (404 model not found) in Claude Code

Other forms of the same error

• API Error: 404 {"type":"error","error":{"type":"not_found_error","message":"Unknown model \"opus 4.6\". Did you mean \"claude-opus-4-6\"? Model IDs use hyphens, e.g. claude-opus-4-6 (not \"opus 4.6\"). Full list: https://www.ccsub.net/api/v1/models | ..."}}
• unexpected status 404 Not Found: <!DOCTYPE html><html lang="zh">...

Two very different causes behind one message

When Claude Code gets a 404, it usually shows There's an issue with the selected model (...). Several reports on the Claude Code issue tracker confirm it does this even when the gateway URL itself is what returned 404. So first figure out which of these you have:

1. Unknown model name. The request reached CCSub, but the model ID isn't one it recognizes. CCSub answers with a JSON not_found_error whose message starts with Unknown model "...", tries to suggest the closest valid name, and links the full list.
2. Wrong URL. The request never hit the API route, and the server returned the website's 404 page — a full HTML document. Every model fails, and Claude Code still reports it as a model issue.

Quick test: if switching models doesn't help, it's almost certainly #2. Check whether the endpoint answers with JSON or HTML:

curl -sS -X POST https://www.ccsub.net/v1/messages -o /dev/null -w '%{http_code} %{content_type}\n'

The correct URL returns 401 application/json (no key was sent, so 401 — but the endpoint exists). Substitute the URL from your own config: 404 text/html means the URL is wrong.

Misspelled model IDs we actually see

• Spaces or dots: opus 4.6, claude-opus-4.6. CCSub's Claude IDs use hyphens throughout, e.g. claude-opus-4-6, claude-sonnet-4-6.
• Versions that don't exist, like claude-opus-6.
• Names copied from another platform with a provider prefix or a custom suffix.
• Things that aren't model IDs at all — pro, chat gpt 4o. Both show up in CCSub's 404 logs from the last 30 days.

The authoritative list is https://www.ccsub.net/api/v1/models; every id there can be pasted into your config as-is. The website's model list shows the same IDs.

Where Claude Code picks the model from

Per the Claude Code docs, the model can come from several places. If one change didn't stick, check them all:

• /model in the session and the --model flag, which win over everything else.
• The ANTHROPIC_MODEL environment variable, which beats the model key in any settings file.
• The model key in ~/.claude/settings.json or the project's .claude/settings.json.
• ANTHROPIC_DEFAULT_SONNET_MODEL, ANTHROPIC_DEFAULT_OPUS_MODEL, and ANTHROPIC_DEFAULT_HAIKU_MODEL, which decide what the sonnet, opus, and haiku aliases resolve to. The haiku one also drives background tasks.

If you set any of these to another platform's model names, update them when you move to CCSub.

Base URL mistakes that cause HTML 404s

• ANTHROPIC_BASE_URL=https://www.ccsub.net/v1. Claude Code appends /v1/messages itself, so you end up at /v1/v1/messages and get an HTML 404. Use https://www.ccsub.net with no /v1.
• A language prefix in the URL, such as https://www.ccsub.net/en. API endpoints don't take one.
• For Codex, Cursor and other OpenAI-compatible tools, the base URL is https://www.ccsub.net/api/v1. When Codex prints unexpected status 404 Not Found: <!DOCTYPE html>..., the url at the end of the error shows exactly which address it requested.

After fixing the config, open a new terminal and restart the tool so it picks up the change.

FAQ

Related errors

• API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"Invalid JSON in request body: Unterminated string in JSON at position 10407567 (line 1 column 10407568)"}}A position in the millions means the body was truncated in transit: /compact or /clear, stop re-pasting big screenshots, read large files in chunks. A tiny position means the JSON itself is malformed.
• API Error: 401 {"type":"error","error":{"type":"authentication_error","message":"Invalid or disabled API key"}}The key never arrived or it's the wrong one. Check /status, re-copy the full key from the dashboard, and unset any leftover ANTHROPIC_API_KEY.
• unexpected status 401 Unauthorized: {"type":"error","error":{"type":"authentication_error","message":"Missing or invalid API key"}}, url: https://www.ccsub.net/api/v1/responsesCheck the url in the error to see where the request went, then define a custom provider with env_key and set that variable in the same environment Codex runs in.