# Use BigModel.io with Codex CLI

> Add BigModel.io as a Codex CLI model provider in config.toml with base_url https://bigmodel.io/v1 and wire_api "responses", and pick a key group that serves the Responses API.

Web version: https://bigmodel.io/docs/codex-cli · Updated 2026-10-18

Codex CLI reads custom providers from `~/.codex/config.toml` and only speaks the OpenAI **Responses** API. BigModel.io serves it at `https://bigmodel.io/v1/responses`, but not every key group does, so check your group first.

| Setting | Value |
|---|---|
| `base_url` | `https://bigmodel.io/v1` |
| `wire_api` | `"responses"` (the only supported value) |
| `env_key` | `BIGMODEL_API_KEY` (the variable holding your key) |
| `model` | a model ID from the [model catalog](https://bigmodel.io/models) |

> Codex no longer supports `wire_api = "chat"`. Old configs fail with `wire_api = "chat" is no longer supported`. There is no Chat Completions fallback, so a key whose group only serves Chat Completions cannot be used with Codex.

## Before you start

1. Create a key in [API Keys](https://bigmodel.io/keys).
2. Check that the key's group serves `/v1/responses` for the model you want. OpenAI- and Anthropic-platform groups do. GLM and DeepSeek groups are Chat Completions only and return 404 here, even though the same model works on `/v1/chat/completions`.

```bash
curl https://bigmodel.io/v1/responses \
  -H "Authorization: Bearer $BIGMODEL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model":"glm-5.3","input":"ping"}'
```

A JSON response with `output` means the group works with Codex. A 404 `not_found_error` saying the platform "only supports /v1/chat/completions" means it does not: use a key from another group, or use a Chat Completions agent such as [OpenCode](https://bigmodel.io/docs/opencode) or [Cline](https://bigmodel.io/docs/cline).

## Configure config.toml

Add this to `~/.codex/config.toml` (create it if needed):

```toml
model = "glm-5.3"
model_provider = "bigmodel"

[model_providers.bigmodel]
name = "BigModel"
base_url = "https://bigmodel.io/v1"
env_key = "BIGMODEL_API_KEY"
wire_api = "responses"
```

Then export your key in the shell that runs Codex and start it:

```bash
export BIGMODEL_API_KEY="sk-..."
codex
```

`env_key` names the environment variable; do not paste the key itself into `config.toml`. Do not name the provider `openai`, `ollama` or `lmstudio`; those IDs are reserved. If Codex misjudges the model's context, set `model_context_window` to the value on the model page.

## Switch models with profiles

Profiles are separate files named `~/.codex/<name>.config.toml`, selected with `--profile <name>`. For example, `~/.codex/fast.config.toml`:

```toml
model = "glm-5.3-flash"
model_provider = "bigmodel"
```

```bash
codex --profile fast
codex -m kimi-k3 "explain this repository"
```

The provider block stays in `~/.codex/config.toml`. Every model you use must be served on `/v1/responses` by your key's group.

## Verify the setup

```bash
codex exec "say hi"
```

You should get a short reply, and the request should appear in [Usage](https://bigmodel.io/usage) with the `/v1/responses` endpoint.

## Troubleshooting

**`wire_api = "chat" is no longer supported`.** Your config is from an older Codex release. Change it to `wire_api = "responses"`.

**404 `not_found_error`: `... platform only supports /v1/chat/completions; /v1/responses is not available`.** The key's group is Chat Completions only (GLM or DeepSeek platform). Codex cannot fall back to chat. Use a key from a group that serves Responses, or switch to [OpenCode](https://bigmodel.io/docs/opencode) or [Cline](https://bigmodel.io/docs/cline).

**404 on every request.** Check `base_url`. It must end in `/v1`, and must not include `/responses`.

**401 `API_KEY_REQUIRED` or "missing environment variable".** `BIGMODEL_API_KEY` is not set in the shell that started Codex. Run `echo ${BIGMODEL_API_KEY:0:5}` to check, and export it in `~/.zshrc` or `~/.bashrc` to make it permanent.

**400 `invalid_request_error` mentioning `previous_response_id`.** BigModel.io does not keep response state over HTTP; the client must send the full input each turn. Update Codex, and report it to [support](https://bigmodel.io/support) if it persists.

**Codex still uses OpenAI.** The top-level `model_provider = "bigmodel"` is missing, or a profile file overrides it. Run with `--profile` explicitly to rule out profile mix-ups.

**503 `api_error`: `No available accounts: no available accounts supporting model: ...`.** The model ID is misspelled or not served by your key's group. Copy the ID from the model page, and list what your key can call with `curl https://bigmodel.io/v1/models -H "Authorization: Bearer $BIGMODEL_API_KEY"`.

**403 `INSUFFICIENT_BALANCE` or 429 `API_KEY_QUOTA_EXHAUSTED`.** Top up in [Billing](https://bigmodel.io/purchase) or raise the key's quota. A 429 `rate_limit_error` ("Concurrency limit exceeded for user") means too many parallel requests; Codex retries, but lower concurrency if it keeps happening.

## Related

- [Configure Base URL in Codex, Claude Code, Cursor and Cline](https://bigmodel.io/blog/configure-base-url-codex-claude-code-cursor) uses the same `config.toml` block.
- [CC Switch](https://bigmodel.io/docs/cc-switch) can write the Codex provider for you.
- [Claude Code](https://bigmodel.io/docs/claude-code) for the Anthropic-protocol terminal agent.
- [Responses API reference](https://bigmodel.io/docs/api-responses).