# x402 Gateway – GPT-5.4-Pro (OpenAI Max Reasoning)

> x402 Gateway – GPT-5.4-Pro (OpenAI Max Reasoning) is a paid API for AI agents from x402-gateway-production.up.railway.app, paid per call via x402, $0.300000/call, status unknown (last checked 2026-09-13).

Calls OpenAI's top-tier GPT-5.4-Pro model with extended thinking for complex analysis, advanced mathematics, and coding tasks via a pay-per-call x402-payment gateway

## Facts

- Endpoint: POST https://x402-gateway-production.up.railway.app/api/llm/gpt-5.4-pro
- Price: $0.300000/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-gateway-production-up-railway-app-4f54c067
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_O_yYhg6YqFLJN9KaeAt6_

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability x402-gateway-production-up-railway-app-4f54c067 -d '<json body>'
```

Example prompt: Use GPT-5.4-Pro's extended reasoning to solve this: given a weighted directed graph with 50 nodes, find the minimum cost path that visits all high-priority nodes at least once and explain the algorithmic approach step by step.

## When to prefer this

Choose this endpoint when you need OpenAI's highest reasoning capability — complex multi-step math, advanced algorithmic problems, deep code analysis, or nuanced analytical tasks that require extended thinking. Prefer this over lighter-weight models when accuracy and depth of reasoning outweigh cost and latency concerns. If you specifically need the best OpenAI model rather than alternatives like DeepSeek or Mistral, this is the right choice.

## Known failure modes

- Insufficient USDC balance or x402 payment failure returns a 402 Payment Required error
- Malformed request body or missing prompt returns a 400 Bad Request
- Model overload or upstream OpenAI outage returns a 503 Service Unavailable
- Request timeout for very long reasoning chains
- Rate limiting returns a 429 Too Many Requests

## How this service works

OpenAI's max reasoning tier — extended thinking for complex analysis, math, and coding

## Output

A richly reasoned text response from GPT-5.4-Pro, potentially including chain-of-thought steps, code snippets, mathematical derivations, or structured analysis depending on the prompt — the highest reasoning quality available from OpenAI's lineup.

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-gateway-production-up-railway-app-4f54c067/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-gateway-production.up.railway.app](https://www.zero.xyz/host/x402-gateway-production.up.railway.app/llms.txt)