Fix Codex OpenRouter Model Name Error

Fix Codex OpenRouter Model Name Error | Generated by AI

Home 2026.02

Question: Why does Codex CLI show error “anthropic/claude-4-sonnet is not a valid model ID” even after setting model_provider to openrouter, and how to fix it?

Answer:

The model name anthropic/claude-4-sonnet is not the correct format that OpenRouter expects in 2026.

OpenRouter uses a different naming convention than what you see in their website dropdown or what people casually write.

Correct model names for OpenRouter (as of February 2026)

Here are the actual strings you should put in the model = "..." field when using OpenRouter provider:

What people call it	Correct OpenRouter model string	Notes
Claude 4 Sonnet	`anthropic/claude-sonnet-4-20250514`	latest Claude 4 Sonnet
Claude 3.7 Sonnet	`anthropic/claude-3-7-sonnet-20250219`	very popular in early 2026
Claude 3.5 Sonnet	`anthropic/claude-3.5-sonnet`	still good & cheaper
DeepSeek R1	`deepseek/deepseek-r1`	best price/performance
DeepSeek V3 0324	`deepseek/deepseek-v3-0324`	very strong coding model
Qwen 2.5 Coder 32B	`qwen/qwen2.5-coder-32b-instruct`	excellent coding & cheap
Gemini 2.5 Pro	`google/gemini-2.5-pro-exp-03-25`	or check exact date suffix
Gemini 2.5 Flash	`google/gemini-2.5-flash`	fast & cheap
Grok 3	`xai/grok-3`	creative & good at code

How to fix your config right now

Edit ~/.codex/config.toml and change the model line to one of these valid names.

Recommended quick fix – use a proven strong & cheap model:

model = "deepseek/deepseek-r1"           # ← this almost always works
model_provider = "openrouter"

[model_providers.openrouter]
name     = "OpenRouter"
base_url = "https://openrouter.ai/api/v1"
env_key  = "OPENROUTER_API_KEY"
# Optional but nice to have
headers = { "HTTP-Referer" = "https://github.com/lzwjava", "X-Title" = "Codex CLI" }

Then in terminal:

export OPENROUTER_API_KEY="sk-or-v1-..."
codex

Or if you really want Claude-level quality (more expensive):

model = "anthropic/claude-sonnet-4-20250514"
# ... rest same as above

Quick diagnostic commands

See what Codex actually loaded:

codex --debug config

List models Codex knows about (helps confirm provider):

codex --debug models

Most common mistakes that cause “not a valid model ID”:

Using website-friendly name instead of OpenRouter API name
Typo in model string (especially dashes / dates)
model_provider line missing or misspelled
Wrong section header: must be exactly [model_providers.openrouter]
Old cached config — sometimes delete ~/.codex/config.toml and start over

After fixing the model name → restart codex (just quit and run again).

You should see no more 400 error and the model name should appear correctly in the header.

References:

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