GPU-Bridge — One Endpoint. Six Backends. Zero Lock-In.

# GPU-Bridge > Unified AI API — 30 services, 99 models, one endpoint GPU-Bridge is a REST API for AI agents and developers. It provides 30 AI services across text, image, video, audio, vision, search, document parsing, and moderation — all accessible through a single `POST /run` endpoint. Jobs are automatically routed across 6 GPU backends with failover. ## API Base URL https://api.gpubridge.io ## Authentication Three payment methods — use any one: ### 1. x402 Protocol (autonomous AI agents) - No account or API key required - Pay per request using USDC on Base (Chain ID 8453) - Send USDC to `0xB0FdC6030B9f30652e8B221B8090d443Dd3C6381` (USDC contract: `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`) - Base64-encode a JSON proof and include it as the `X-Payment` header - Instant on-chain verification, ~$0.001 gas fees ```http POST /run HTTP/1.1 Host: api.gpubridge.io Content-Type: application/json X-Payment: eyJ0eEhhc2giOiIweC4uLiIsImZyb20iOiIweC4uLiJ9 {"service":"llm-4090","input":{"prompt":"Hello"}} ``` The `X-Payment` header is a base64-encoded JSON object: ```json { "txHash": "0x<64 hex chars>", "from": "0x<your wallet address>" } ``` **Flow for AI agents:** 1. Call any endpoint without payment → receive HTTP 402 with spec-compliant x402 response 2. Parse `accepts[0].maxAmountRequired` (USDC units, 6 decimals) and `accepts[0].payTo` 3. Send USDC on Base to `payTo` address (amount >= `maxAmountRequired`) 4. Base64-encode `{"txHash":"0x...","from":"0x..."}` and set as `X-Payment` header 5. Retry the same request → payment verified on-chain, job executes The 402 response follows the x402 spec (https://x402.org): ```json { "x402Version": 1, "accepts": [{ "scheme": "exact", "network": "base", "maxAmountRequired": "10000", "payTo": "0xB0FdC6030B9f30652e8B221B8090d443Dd3C6381", "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913", "maxTimeoutSeconds": 300 }] } ``` The `maxAmountRequired` varies per service (e.g. 3000 fo