By The BSC block-builder market
BNB Chain (chain id 56) has a public mempool and a proposer-builder (PBS) market for blocks. Validators take blocks assembled by builders, and builders compete to fill them. 48 Club (Puissant) and BlockRazor build most BSC blocks.
Blocks arrive roughly every 0.45 seconds, so the window between a transaction appearing in the public mempool and being included is short, but it is still visible to anyone watching.
What eth_sendBundle does
eth_sendBundle is the RPC method builders use to accept a bundle: an ordered list of signed transactions that must be included together. On BSC, both 48 Club and BlockRazor accept it with two fields: txs, the signed raw transactions in order, and maxBlockNumber, the last block in which the bundle may be included.
Neither builder requires an API key. The bundle is sent directly to the builder instead of the public mempool, so it is not visible to other traders before it lands.
All-or-nothing inclusion
- A bundle lands whole, in order, in one block, or not at all.
- Transactions inside it cannot be split up or reordered by other traders.
- If it is not included before maxBlockNumber, nothing is spent and the nonces stay free for the next attempt.
- Because inclusion is atomic, dependent steps such as opening trading and buying can safely go in the same bundle.
Simulating without eth_callBundle
On Ethereum, eth_callBundle is often used to dry-run a bundle on the builder before sending it. Neither 48 Club nor BlockRazor implements eth_callBundle.
TokenBundle works around this by simulating the signed transactions in order with eth_simulateV1 on a normal RPC. The simulation runs against current chain state and shows whether every transaction succeeds and what each buy returns. Only after it passes is the bundle sent.
How TokenBundle sends BNB bundles: gas and priority
TokenBundle sends the same bundle to both 48 Club and BlockRazor, valid for about 40 blocks. Sending to both covers most BSC blocks, and because the bundle is atomic it can only be included once.
The same approach is used for everyday trading. In the Terminal on BNB, every buy or sell is sent privately as a one-transaction builder bundle rather than through the public mempool, so it cannot be sandwiched.
| Setting | Value | Why |
|---|---|---|
| Normal network gas | About 0.05 gwei | Typical BSC gas price for regular transactions |
| Bundle priority fee | At least 1 gwei | Builders rank bundles by priority fee |
| Bundle validity | About 40 blocks | Roughly 18 seconds at about 0.45 s per block |
How BSC bundles compare to Flashbots
The idea is the same as a Flashbots bundle on Ethereum: private submission to builders and atomic, ordered inclusion. The practical differences are the builders you send to, the missing eth_callBundle on BSC builders, and much shorter block times, which is why validity is counted as a window of blocks rather than a single target block.
On Ethereum, TokenBundle relies on the Flashbots-style builder market, covered in our Flashbots bundle guide. On BNB Chain the same atomic idea is applied through 48 Club and BlockRazor, with eth_simulateV1 doing the pre-send check that eth_callBundle would otherwise do.
What a bundle does not guarantee
- Inclusion is not guaranteed. A bundle competes with everything else the builders are considering and may simply not be picked within its window.
- A bundle only reaches blocks built by the builders it was sent to. Sending to both 48 Club and BlockRazor covers most BSC blocks, not every block.
- Transactions inside a bundle still pay gas if included, including the priority fee builders use to rank bundles.
- A bundle does not fix a flawed contract or a mispriced buy. That is why every transaction is simulated in order before the bundle is sent.
- State can change between simulation and inclusion. Buy floors and tolerances protect each wallet from executing far from the simulated result.
FAQ
- Do I need an API key to send a bundle to 48 Club or BlockRazor? No. Both accept eth_sendBundle with txs and maxBlockNumber and do not require an API key.
- Can I simulate a bundle with eth_callBundle on BSC? Not on these builders, since neither implements it. TokenBundle simulates the signed transactions in order with eth_simulateV1 on a normal RPC instead.
- What happens if my BSC bundle is not included? Nothing is spent and nonces stay free once the window passes, so you can try again.
- Why pay 1 gwei priority when gas is about 0.05 gwei? Builders rank bundles by priority fee, so bundle transactions pay at least 1 gwei to be picked up.
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