Claude Code on sference

Claude Code talks to the Anthropic Messages API, and sference serves that API for open models. Point it at sference and your agent loop runs on moonshotai/Kimi-K2.7-Code, zai-org/GLM-5.2, or your own fine-tune, on European GPUs, at open-model token prices, with the same request-level audit trail as the rest of the platform.

Fastest path: sference launch claude

The sference CLI ships a launcher that configures everything and starts Claude Code for you:

curl -fsSL https://raw.githubusercontent.com/s-ference/sference/main/install.sh | sh
sference auth login --api-key 'sk_...'
sference launch claude

By default this runs in proxy mode: a local mitmproxy forward proxy is started, Claude Code launches with HTTPS_PROXY pointed at it, and ANTHROPIC_BASE_URL is left unset so Claude Code's first-party detection stays on. The result is hybrid routing: sference models appear in Claude Code's /model picker and are routed to sference's /v1/messages, while real claude-* models pass straight through to Anthropic. You can switch between them mid-session.

Proxy mode needs mitmdump on your PATH. The installer adds it; on an existing install, uv tool install mitmproxy. If it is missing, the launcher tells you and suggests --no-anthropic.

Default model: moonshotai/Kimi-K2.7-Code. Override with --model or the SFERENCE_MODEL environment variable.

Manual configuration

If you would rather not run a proxy, configure Claude Code directly. Everything goes through ANTHROPIC_BASE_URL, so all traffic, including claude-* model names, hits sference, and the model is whatever you pin.

Add to ~/.claude/settings.json (or .claude/settings.json in a project):

{
  "env": {
    "ANTHROPIC_BASE_URL": "https://api.sference.com",
    "ANTHROPIC_AUTH_TOKEN": "sk_your_sference_key",
    "ANTHROPIC_MODEL": "moonshotai/Kimi-K2.7-Code"
  }
}

• Prefer ANTHROPIC_AUTH_TOKEN (sent as Authorization: Bearer). ANTHROPIC_API_KEY also works (sference accepts x-api-key), but set one or the other, not both.
• ANTHROPIC_MODEL must be a sference catalog id. There are no claude-* aliases; a Claude model name returns 400. See Models.
• Restart Claude Code after editing settings.

Verify the endpoint independently of Claude Code:

curl https://api.sference.com/v1/messages \
  -H "Authorization: Bearer $SFERENCE_API_KEY" \
  -H "content-type: application/json" \
  -d '{
    "model": "moonshotai/Kimi-K2.7-Code",
    "max_tokens": 256,
    "messages": [{ "role": "user", "content": "hi" }]
  }'

Choosing a model

Live ids and pricing: GET https://api.sference.com/v1/models.

What to expect

Two API calls per prompt is normal. Claude Code fires a separate title-generation request alongside your actual turn: no tools, a <session> user body, asking for a JSON title. sference detects it, caps it at 512 completion tokens, and forces reasoning off so it does not burn tokens on chain-of-thought before emitting a title. Seeing two requests per prompt in the console is expected, not a bug.

Thinking works, signatures do not. Reasoning models stream thinking blocks that Claude Code renders normally, but signature is always empty. Multi-turn thinking continuity is best-effort: sference re-injects the inbound thinking text rather than a verified signed block.

No vision. Catalog coding models are text-only. Screenshot tools and image attachments are replaced with a placeholder, and sference injects a system notice telling the agent it has no vision so it stops retrying image capture and verifies with Read, grep, and build output instead. If you specifically need image input, use Qwen/Qwen3-VL-30B-A3B-Instruct, but it is not a coding model.

Tool search may be off. Claude Code disables tool search on non-Anthropic hosts unless told otherwise. In direct mode, sference launch claude --no-anthropic --enable-tool-search sets ENABLE_TOOL_SEARCH=true for you.

Known limits

The full compatibility surface, covering every supported field, block type, and streaming event, is on the Anthropic Messages API page.

Troubleshooting

401 Unauthorized. The key must be a sference sk_... key. If both ANTHROPIC_API_KEY and ANTHROPIC_AUTH_TOKEN are set, unset one. A stale Anthropic key in your shell profile overriding the sference key is the usual cause.

400 with an unknown-model message. ANTHROPIC_MODEL is a Claude name, or a catalog id your key is not entitled to. Check GET /v1/models.

402 Payment Required. The team credit balance is exhausted. Top up in the console.

Raw <tool_call> or </think> text in replies instead of tool calls. The model emitted tool syntax the parser did not extract, usually because max_tokens was too low and the call was truncated mid-JSON. Raise max_tokens (Claude Code tool turns need real headroom) or switch to a model with better tool support.

Slow first token. Long time-to-first-token on a queued request is normal under load; the stream sends ping keepalives while waiting. A request that never completes within the 600s sync window returns 504 and is cancelled server-side.

504 Gateway Timeout. A single turn exceeded the sync inference window. Shorten the turn, reduce context, or pick a faster model.

Related