By What a Burst launch is
Burst is TokenBundle's default launch mode on Base. The whitelist call, the open-trading call and one buy per bundle wallet are built as separate transactions and signed up front. They are dry-run in order with eth_simulateV1, which names any failing transaction together with its sender, so problems surface before anything is sent.
The signed transactions are then sent as one ordered JSON-RPC batch straight to the Base sequencer, with the same priority fee on every transaction.
Why the ordered batch lands together
Base has no public mempool, so no one sees the transactions before the sequencer does. Inside a Flashblock, the sequencer orders transactions by priority fee, then by arrival. With equal priority fees and the batch arriving in order, the buys land right behind the open, usually in the same 200 ms Flashblock.
Each buy is its own transaction from its own wallet, paying its own gas. On BaseScan that looks like ordinary, separate buys rather than one linked transaction.
Where a Burst launch can be exposed
Burst is not atomic. If a buy misses the Flashblock of the open, it competes in the next one, and snipers who saw the open can be there too. Without any protection in the token, that is the gap a sniper could use.
Bundle Fren's own documentation describes the same limit for its Base Burst Bundle: it states about 99% success and that snipers can occasionally slip in. TokenBundle's figure for a token without a whitelist is the same, about 99%.
How the anti-snipe whitelist closes the gap
Tokens created with Deploy Token include an anti-snipe whitelist window. The default is 15 blocks, about 30 seconds on Base. During the window only whitelisted wallets can buy.
At Execute, the first transaction in the Burst batch whitelists every bundle wallet, and only then does trading open. Any buy from a wallet that is not whitelisted reverts during the window, even if it lands between your transactions. A buy of yours that slips into the next Flashblock still succeeds, because your wallet is whitelisted, while the sniper's buy fails.
That is why a Burst launch with a Deploy Token contract reaches about 100%: the timing gap still exists, but no outside wallet can use it.
The order inside the batch matters. Because the whitelist call comes before the open-trading call and both carry the same priority fee as the buys, the bundle wallets are already whitelisted at the moment trading opens. There is no point in the sequence where trading is open and your wallets are not yet allowed to buy.
The window is measured in blocks, not in transactions. Once the 15 blocks have passed, the token trades normally and anyone can buy, so the window covers the opening moments right after trading opens.
What the fork test showed
- On a Base mainnet fork, open trading plus 7 separate buys all landed in the same block, right after the open.
- A buy from a non-whitelisted wallet sent right after the open reverted with UniswapV2: TRANSFER_FAILED.
- The dry run with eth_simulateV1 ran the full ordered sequence before submission, so a failing transaction would have been named with its sender.
When to choose Atomic instead
If you launch a token that was not created with Deploy Token and has no whitelist, the gap between Flashblocks is not covered. In that case Atomic mode, which puts the open and every buy into one EIP-7702 transaction, removes the gap entirely. The trade-off is that all wallets appear inside one transaction on BaseScan, and Atomic fits up to 75 of your own wallets.
FAQ
- Is a Burst launch atomic? No. Each transaction is separate, so a buy can occasionally land in the Flashblock after the open.
- How long is the anti-snipe window? The default in Deploy Token is 15 blocks, which is about 30 seconds on Base.
- What happens to a sniper's buy during the window? It reverts, because only whitelisted wallets can buy and Execute whitelists every bundle wallet before trading opens.
- Can I use Burst for a token I did not deploy with TokenBundle? Yes, but without a whitelist the success rate is about 99% rather than about 100%.
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