Use BigModel.io with Claude Code

Claude Code talks the Anthropic Messages protocol. BigModel.io serves it at https://bigmodel.io/v1/messages, so you configure the gateway root and Claude Code adds /v1/messages itself. For OpenAI-protocol code, the base URL is https://bigmodel.io/v1 instead.

Anthropic states that Claude Code does not officially support non-Claude models through a gateway. GLM, Kimi, DeepSeek and MiniMax models work through BigModel.io, but Anthropic will not help with problems specific to them, and quality on long agentic tasks varies by model.

#Before you start

1. Install Claude Code and confirm claude --version works.
2. Create a key in API Keys. Its group decides which models and endpoints you can call.
3. Check that the key's group serves the Messages endpoint. GLM and DeepSeek groups that are "Chat Completions only" return 404 on /v1/messages; for those keys, use an OpenAI-protocol tool such as OpenCode or Cline.

This request should return a short reply. Replace glm-5.3 with the model you plan to use:

curl https://bigmodel.io/v1/messages \
  -H "Authorization: Bearer $BIGMODEL_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -H "Content-Type: application/json" \
  -d '{"model":"glm-5.3","max_tokens":64,"messages":[{"role":"user","content":"ping"}]}'

#Configure with environment variables

For a single terminal session:

export ANTHROPIC_BASE_URL="https://bigmodel.io"
export ANTHROPIC_AUTH_TOKEN="${BIGMODEL_API_KEY:?Set BIGMODEL_API_KEY first}"
export ANTHROPIC_MODEL="glm-5.3"
# Claude Code also runs small background tasks; point them at a model you can call.
export ANTHROPIC_DEFAULT_HAIKU_MODEL="glm-5.3-flash"

claude

Use ANTHROPIC_AUTH_TOKEN, not ANTHROPIC_API_KEY. ANTHROPIC_API_KEY is sent as x-api-key and needs a one-time approval in interactive mode; if both are set, Claude Code reports an auth conflict. Run unset ANTHROPIC_API_KEY.

#Configure in settings.json

To keep the setting across sessions, add an env block to ~/.claude/settings.json (all projects) or .claude/settings.local.json (one project, not committed):

{
  "env": {
    "ANTHROPIC_BASE_URL": "https://bigmodel.io",
    "ANTHROPIC_AUTH_TOKEN": "sk-your-bigmodel-key",
    "ANTHROPIC_MODEL": "glm-5.3",
    "ANTHROPIC_DEFAULT_OPUS_MODEL": "glm-5.3",
    "ANTHROPIC_DEFAULT_SONNET_MODEL": "glm-5.3",
    "ANTHROPIC_DEFAULT_HAIKU_MODEL": "glm-5.3-flash"
  }
}

Never put the key in a committed .claude/settings.json. Values in a settings file win over a shell export. Claude Code's opus, sonnet and haiku aliases in /model map to the three ANTHROPIC_DEFAULT_*_MODEL values, and the haiku slot is also used for background tasks, so set all three to models your key can call. ANTHROPIC_SMALL_FAST_MODEL is deprecated.

#VS Code extension

The Claude Code extension for VS Code does not read the variables you export in a terminal. Either:

• put the env block above in ~/.claude/settings.json, which the extension and the CLI share (recommended), or
• add the variables to the extension's claudeCode.environmentVariables setting in VS Code.

Also turn on Disable Login Prompt (claudeCode.disableLoginPrompt) so the extension does not ask for a claude.ai sign-in.

Claude Desktop ignores ANTHROPIC_BASE_URL, so it cannot be pointed at BigModel.io this way.

#Choosing a model

Model IDs are lowercase and keep their dots (deepseek-v4-pro, not DeepSeek-V4-Pro). Copy the ID from the model page; availability depends on your key's group.

Switch inside a session with /model glm-5.3, or start with claude --model kimi-k3. Try a small task before a long agentic run.

#Context window for non-Claude models

Claude Code does not know these model IDs. It shows a warning that the model "isn't recognized" and assumes a 200k-token context. Set CLAUDE_CODE_MAX_CONTEXT_TOKENS to the model's real context window (from its model page) so automatic compaction starts at the right time:

export CLAUDE_CODE_MAX_CONTEXT_TOKENS=128000   # replace with the model's context window

Do not enable CLAUDE_CODE_ENABLE_GATEWAY_MODEL_DISCOVERY: it keeps only model IDs that contain claude or anthropic, so BigModel.io models will not appear. Use ANTHROPIC_MODEL and the alias variables instead.

#Other useful variables

#Verify the setup

Run /status inside Claude Code. It should show https://bigmodel.io as the Anthropic base URL and an auth token line from your environment or settings. Then send one prompt and confirm the request appears in Usage. A reply alone does not prove the right base URL was used.

#Troubleshooting

403 permission_error: This group does not allow /v1/messages dispatch. The key's group doesn't offer the Anthropic Messages endpoint. Use a key from a group that supports it, or connect your tool through the OpenAI-compatible endpoint instead (OpenCode, Cline). Contact support if you're unsure which group to use.

404 not_found_error: ... platform only supports /v1/chat/completions; /v1/messages is not available. The key belongs to a Chat Completions-only group (GLM or DeepSeek platform). Use a key from a group that serves Messages, or use an OpenAI-protocol tool.

404 on every request. Check ANTHROPIC_BASE_URL. With https://bigmodel.io/v1 the client calls /v1/v1/messages. Remove the /v1.

401 INVALID_API_KEY or API_KEY_REQUIRED. The token is missing or mistyped, or Claude Code is still using a claude.ai login. Check /status, make sure ANTHROPIC_AUTH_TOKEN is set where claude starts, and remove any ANTHROPIC_API_KEY.

503 api_error: No available accounts: no available accounts supporting model: .... The model ID is misspelled, or your key's group does not serve it. List what your key can call with curl https://bigmodel.io/v1/models -H "Authorization: Bearer $BIGMODEL_API_KEY".

400 "Extra inputs are not permitted". Claude Code sent a beta field or anthropic-beta header that the model path rejects. Set CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS=1 and restart.

Warning "isn't recognized · context assumed to be 200k tokens". Expected for non-Claude models. Set CLAUDE_CODE_MAX_CONTEXT_TOKENS as shown above.

Main replies work but titles, summaries or subagents fail. Background tasks use the haiku slot. Set ANTHROPIC_DEFAULT_HAIKU_MODEL to a model your key can call.

403 INSUFFICIENT_BALANCE or 429 API_KEY_QUOTA_EXHAUSTED. Top up in Billing or raise the key's quota in API Keys. A 429 rate_limit_exceeded with a message like "api key 5小时限额已用完" means a key spend window is used up; it resets when the window ends.

409 malformed_session_state. The conversation history has thinking blocks or tool IDs the model cannot accept, often after switching models mid-session. Start a new session with /clear.

Settings seem ignored. A settings file beats a shell export, and a project .claude/settings.json or .claude/settings.local.json can override your user file. Run env | grep ANTHROPIC, check the project's settings files, and restart Claude Code after changes.

#Related

• Configure Base URL in Codex, Claude Code, Cursor and Cline — the same settings side by side.
• CC Switch to import a key into Claude Code with one click.
• Codex CLI and OpenCode for OpenAI-protocol terminal agents.
• Errors for every error code.
• API quickstart for keys, billing and first requests.