# TxWhy

> Failed Solana transaction in, working transaction out. TxWhy finds the exact reason a Solana transaction fails, rebuilds it, proves the rebuilt one passes by simulating it against live mainnet state, and lets the caller verify offline that nothing else changed.

Live: https://txwhy.vercel.app - MIT - no API key - agents are the primary users.

## What it repairs
- Compute unit limit (measured usage + 15%), expired blockhash, priority fee (75th percentile for the exact accounts, capped at 0.001 SOL), loaded-accounts data limit.
- Jupiter v6 swap on a stale quote: only the swap instruction is replaced, same tokens, amount and tolerance.
- Direct Pump.fun / PumpSwap / Raydium AMM v4 swap on slippage: same amount and accounts, only the limit moved to the current price, never more than 25% against the user.
- Legacy, v0 and version 1 (SIMD-0385) transactions; durable nonces.
- Anything else is diagnosed: failing instruction, program, decoded error (1,934 published codes across 40 programs), what to do.

## Rules a repair can never break (verifiable offline)
Same fee payer, same signers, every non-ComputeBudget instruction byte for byte in order, at most one equivalent swap replacement or one bounded limit move. The verifier ships in the npm package and has no network access.

## Use it
- HTTP: POST https://txwhy.vercel.app/api/v1/repair with body {"transaction": "<base64>"} or {"signature": "<sig>"}. Response: {status, cause, changes, repairedTransaction, simulation, verification, notes}. status is one of repaired, valid, needs_requote, not_repairable.
- Paid, no rate limit: POST https://txwhy.vercel.app/api/x402/repair ($0.001 USDC on Solana via x402, settled only on success).
- MCP (Streamable HTTP): https://txwhy.vercel.app/api/mcp with tools repair_transaction, diagnose_transaction, explain_error.
- npm: @txwhy/sdk with sendWithRepair(connection, tx, sign), repair(), verifyRepair(), and the CLI npx txwhy <signature>. @txwhy/sdk/kit is the same for @solana/kit (rpc, tx, sign) and handles version 1.
- Rust: crate txwhy-verify on crates.io (cargo add txwhy-verify), the offline verifier with no Solana dependencies.
- Error code pages: https://txwhy.vercel.app/errors/{program}/{code}
- OpenAPI: https://txwhy.vercel.app/openapi.json - Agent skill: https://txwhy.vercel.app/skill.md
- Telegram: https://t.me/txwhy_bot

## Data
Live failure index of Solana's busiest programs: https://txwhy.vercel.app/failures - Public usage: https://txwhy.vercel.app/stats