GPT-5 Codex is a version of GPT-5 optimized for agentic coding in Codex or similar environments, available exclusively through the Responses API with regular underlying snapshot refreshes. It supports a 400,000-token input context with 128,000 output tokens, text and image inputs, and exposes reasoning tokens, streaming, function calling, and structured outputs.
Chat Completions API
/api/v1/chat/completions
OpenAI-compatible endpoint with a messages array. Standard interface for chat-based interactions.
Responses API
/api/v1/responses
Native OpenAI Responses format with a simplified input parameter for single-turn requests.
These providers haven't been health-probed for this model yet. The router still routes around upstreams that fail live requests — uptime fills in once probe history accrues.
curl https://anyrouter.dev/api/v1/chat/completions \
-H "Authorization: Bearer $ANYROUTER_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "openai/gpt-5-codex",
"messages": [
{"role": "user", "content": "Say hi in 3 words."}
]
}'ANYROUTER_API_KEY — Dashboard → Keys{
"model": "openai/gpt-5-codex",
"messages": [
{
"role": "user",
"content": "Say hi in 3 words."
}
]
}Change sort, ZDR, effort, or pin a provider to add routing params.