Slippage on pump.fun Explained: Settings, Errors and Fixes

"Transaction failed: custom program error 6003." If you have traded on pump.fun for more than a day, you have probably seen something like that. It looks like a bug. It is actually the program doing its job: your trade would have filled at a worse price than you agreed to, so it refused.

That is slippage, and once you understand what the number in your settings controls, the errors stop being mysterious.

#What is slippage on pump.fun?

When you press buy, your wallet or tool asks for a quote: "1 SOL gets you about this many tokens right now." Then it builds a transaction and sends it. Between the quote and the moment your transaction executes, other trades can land on the same bonding curve and move the price.

Slippage is the gap between the price you were quoted and the price you actually get. Your slippage setting is how much of that gap you are willing to accept.

The pump.fun program enforces it with a hard limit inside every trade:

If the curve has moved past your limit by the time your trade runs, the program stops it. Nothing is bought or sold. You pay the network fee for the failed transaction, and that is it.

1. Quote

   your tool prices the trade against the curve as it is now

2. Other trades land

   buyers or sellers move the price first

3. Your trade runs

   the program checks your max cost or min return

4. Refused

   6002 on a buy, 6003 on a sell, no tokens move

#Why does the price move so much?

Every pump.fun coin trades on a bonding curve, and on a curve the price is a direct function of how many tokens have been sold. Every buy raises the price and every sell lowers it. There is no order book absorbing trades at a fixed level.

Early on, the effect is large. On a fresh mainnet curve, a 1 SOL first buy gets roughly 3.4% of supply, and the next 1 SOL buy gets less because the price has already risen. When a coin is busy, a dozen trades can land in the same second, and your quote is stale before you even sign. The pump.fun bonding curve explained goes into the math.

After a coin migrates to PumpSwap the same idea applies, just with a pool instead of a curve. Your trade moves the pool's price, and so does everyone else's.

#How much slippage should you set?

There is no correct number, but there is a clear trade-off.

What it depends on:

• How active the coin is. A coin with constant trades needs more room than one that trades every few minutes.
• Your trade size relative to the curve. A large buy moves the price itself, so a quote for it is more sensitive to anything landing first.
• How much the exact price matters to you. If you just want in or out, a wider setting is fine. If the price is the whole point, keep it tight and accept retries.

#Slippage when trading from many wallets

This is where most people get burned. Imagine you sell 50% from five wallets at once, and the tool quotes all five against the current curve. The first sell lands and lowers the price. The other four were quoted against the price before that sell, so their minimum SOL out is now above what the curve can pay. They fail with 6003, even though your slippage setting looked generous.

The fix is not to crank slippage up. It is to quote each wallet in the order it will be sent, against the price the previous wallets leave behind. DevBundler does this for every batch, buys and sells, so each wallet's limit is reachable. Why batch sells fail tells the whole story.

The same logic applies to launch buys. In a bundled launch, DevBundler quotes the dev wallet first, then each buyer after the ones before it, which is why later wallets show slightly higher SOL costs for the same percentage.

#Other things that look like slippage but are not

Not every failed trade is a price problem. Before you widen slippage, check the actual error:

In DevBundler, dashboard trading switches to PumpSwap automatically once the curve completes. Slow landings are what the Normal, Fast and Turbo speed presets are for; they set the priority fee. Solana priority fees explained covers when they are worth paying.

#A sensible default routine

1. Start with a moderate slippage setting for normal trades.
2. If a trade fails with 6002 or 6003 once, retry before changing anything. The price may have just ticked.
3. If it keeps failing on a busy coin, widen slippage a step and raise the speed preset.
4. For multi-wallet trades, use a tool that quotes in order rather than widening slippage to paper over bad quotes.