What is Block Assembly Marketplace (BAM)?
Block Assembly Marketplace (BAM) is a Jito system that creates Solana blocks inside secure, tamper-proof hardware. BAM went live on mainnet September 25, 2025. BAM takes transaction ordering out of validator software and puts it inside a network of BAM nodes, which run Trusted Execution Environments- TEEs are secure hardware enclaves that work on data without the node operator seeing the raw data (it remains encrypted in memory throughout). BAM thus makes block building have provably fair ordering, not just assumed.
Imagine sealed envelopes in an auction. Bidders drop their sealed bids into a secure machine. A tamperproof device- not a person- opens the envelopes, implements a pre-announced set of rules, and outputs an order receipt that proves the rules were followed. The machine owner can't peek at the bids in advance or re-order the envelopes. BAM is Solana blockspace's machine.
How BAM works
Normally, a Solana leader receives transactions through Gulf Stream and orders transactions itself, with full visibility into all transactions in the leader pipeline. This is where most of MEV comes from.
BAM changes the order of operations. Transactions go to a BAM node, where a TEE keeps transactions encrypted until after scheduling decisions are made (so the BAM node operator can't see before execution). The BAM enclave orders transactions according to a pre-defined set of rules, then passes the ordered transactions to a Solana validator. BAM creates an attestation for every BAM ordering decision, i.e. a cryptographic signature that says “here is an order of transactions. I saw this order at this timestamp” and this lets anyone verify that the transactions executed in an order consistent with the ordering rules.
One of the most interesting parts of BAM are plugins. Plugins let developers customize how transactions are sequenced for their use case- e.g. a derivatives DEX such as Drift can require a “cancel first” rule for users’ trades, while Pyth can guarantee that price updates execute before dependent trades. At launch, Drift, Pyth, and DFlow are working plugins. With BAM, the ACE vision is being delivered first- Solana plans for application-controlled execution in the near-term.
How does BAM compare to Ethereum’s approach
In the same era, Ethereum addressed MEV using proposer-builder separation, i.e. specialized block-building services construct transactions and validators then choose a builder to include the highest bidder through a relay like Flashbots. In the PBS approach, a builder market emerges but the power remains concentrated in a few block builders that assemble most Ethereum blocks. Users still trust builders not to steal.
BAM’s bet is different: users need not trust the builder but can verify that the BAM device has done its job. As with all engineering trade-offs, this also brings real trade-offs. TEEs bring their own attack surfaces- Intel SGX TEEs have been attacked with side-channel attacks before- as do any BAM devices (the node network is a new infrastructure layer between user and chain). Moreover, BAM’s growth will make a single company’s client stack (already used by most stake) more powerful; we already have 30%+ of stake running Jito-Solana and BAM brings more stake closer to this stack- a valid concern about centralization but not an invalid one.
Why BAM matters
In a DeFi transaction- swapping on Jupiter on a 15-second volatile minute, e.g.- BAM is replacing hidden games to order transactions for the end-user. The ordering of transactions will be verifiable, not just assumed by users. Developers will have plugins that turn market microstructure into a design space for their users. That’s the Solana roadmap- internet capital markets, which starts with BAM. Finally, BAM lets validators keep growing their MEV share (now with verifiable execution) into a shared revenue stream with validators on a chain where the average transaction fee is $0.00025 while Ethereum users can pay a dollar per transaction.
