Robinhood Chain vs Solana and priority auction chains, BLCK

This is the one document in BLCK that discusses Solana and Jito. BLCK does not use that vocabulary anywhere else, because most of what it means does not exist on Robinhood Chain and importing it leads to wrong strategies. If you learned MEV on Solana, read this before anything else in The Meta.

Three ordering models are compared. Solana with Jito, because that is the background this document assumes for Rust searchers. Arbitrum One with Timeboost, because Robinhood Chain runs the same Nitro stack and Arbitrum One shows what a priority auction on that stack looks like. Robinhood Chain, which as of 2026-09-16 has neither.

Facts about Robinhood Chain below are from STATUS.md in this repo, verified against live RPC, the L1 contracts, a raw feed capture, and the official docs. Descriptions of Solana, Jito, and Arbitrum One are taken from their own public documentation, are not covered by STATUS.md verification, and are kept to the minimum needed for contrast.

The comparison

	Solana with Jito	Arbitrum One with Timeboost (PGA voted)	Robinhood Chain
Who orders	The leader for the current slot. With Jito, a Block Engine sits in front of the leader and runs an auction for bundle position.	The Arbitrum One sequencer. Timeboost adds an auctioned express lane in front of it.	A single sequencer operated by Robinhood. One batch poster (0xDaa526086787d9DEbE1D7F3FFdb1fE50cf8687F4). No backup sequencer listed on L2BEAT.
Ordering rule	The leader decides. Jito bundles are placed by tip auction.	Timeboost: an express lane controller, chosen by a per-round auction, gets its transactions sequenced ahead of everyone else for that round. An ArbitrumDAO Constitutional AIP has passed to move Arbitrum One to priority gas auctions plus a paid Fast Feed.	Strict first come, first served by arrival time at the sequencer. That is the official description. Nothing BLCK checked contradicts it: `eth_maxPriorityFeePerGas` returns 0, txpool methods are absent, and 789 captured feed messages carry no Timeboost markers. Arrival-time ordering itself has not been measured yet; blck-probe is where that happens.
Can you pay for position	Yes. Tips, auctioned through the Block Engine.	Yes. Express lane bids per round today. Priority fees once the PGA move lands.	No. `eth_maxPriorityFeePerGas` returns 0. The docs state that raising your fee does not move you ahead of transactions already queued. One caveat: Ordo, a third party, runs a private RPC with sealed-bid 200 ms backrun auctions and a searcher SDK. It has no disclosed agreement with Robinhood and it does not change how the sequencer orders.
Atomic multi-transaction guarantees	Jito bundles: a small fixed set of transactions executed atomically, in order, all or nothing.	None at the protocol level. Atomicity is per transaction.	None. Atomicity is per transaction. A strategy with several legs is one call into a contract that does all of them and reverts as a unit.
What a searcher optimizes	Bundle construction, tip sizing, land rate.	Bid strategy for the express lane, then latency. Under PGA: fee bidding plus latency.	Arrival time at the sequencer submission endpoint, and having the complete transaction signed before the trigger fires. Nothing else moves you.
Where the race is decided	In the Block Engine auction, then at the leader.	In the round auction, then at the sequencer.	At the sequencer's ingress. Wire time from your process to `https://sequencer.mainnet.chain.robinhood.com`. The sequencer's location is inferred from DNS and Glassnode as AWS us-east-2 (Ohio), not published by Robinhood.
Public mempool	No traditional mempool. Transactions are forwarded toward the leader. Jito adds its own submission path.	Same Nitro stack as Robinhood Chain. BLCK has not checked Arbitrum One's RPC surface. The passed AIP adds a paid Fast Feed.	No. `txpool_content`, `txpool_status`, and `eth_newPendingTransactionFilter` return method not found on both networks. The sequencer feed (`wss://feed.mainnet.chain.robinhood.com`) is public, but it shows transactions after they are ordered, not before.
Failure modes	Outbid on tip. Bundle not landed.	Losing the round auction. Under PGA, losing on fee. What an unused winning bid or a reverted transaction under PGA costs is not something BLCK has verified.	Arriving second: the transaction still lands, reverts, and you pay gas for it. Sequencer downtime with no listed failover. L1 batch posting can pause while L2 blocks continue: about 14 minutes across two windows on Sept 4, 2026. Force inclusion through the L1 delayed inbox exists but the delay is 4 days. Open question: an ArbOS 61 transaction filtering precompile that L2BEAT says can nullify force inclusion; BLCK has not probed it.

Translation table for people arriving from Solana

What you optimized on Solana	What it becomes on Robinhood Chain
Bundle efficiency	Arrival-time latency. There is no bundle. Your unit is one transaction, and the only thing that decides whether it is first is when it reaches the sequencer. blck-probe exists to measure that path.
Block packing	Single-call atomic strategies. One transaction, one contract call that does every leg and reverts as a unit if any leg fails. The Solidity executor with Foundry tests is Milestone 3. blck-sim (revm) is where you check it before you send.
Tips and auctions	Nothing. There is no protocol-level way to pay for position and BLCK does not invent one. Ordo's third-party backrun auction is the closest thing that exists and it sits beside the sequencer, not inside it.
Rust programs	Rust moves off-chain. Contracts are Solidity. Rust is the searcher stack: alloy for RPC, signing, and ABI encoding; revm for local simulation. blck-common, blck-probe, blck-sim, and blck-arb are all built on it.
No Solana equivalent	Stock-token gap trading. Robinhood Stock Tokens are 194 active tickers issued as ERC-20s with 18 decimals. Chainlink's US equity streams run 24/5 and report Closed on weekends, so onchain weekend prices have no oracle anchor. Primary mint and burn is limited to KYB'd Authorized Participants in a Monday 02:00 CET to Saturday 02:00 CET window. blck-gaps studies this, read-only.

A few habits to drop on day one:

Do not simulate a set of transactions and expect them to land together. Put the set inside one call.
Do not budget for a tip. Budget for the gas of a reverted transaction, because arriving second means paying for nothing.
Do not look for a leader schedule. There is one sequencer, always, at one endpoint.
Do not treat the feed as a mempool. It is post-ordering. It tells you what already happened, earlier than block RPC does. How much earlier is a blck-probe measurement, not a number BLCK states yet.

What changes if Robinhood adds Timeboost or a PGA

Nothing is announced. No statement from Robinhood or Offchain Labs, and the docs still say fees cannot buy position (STATUS.md, Q3). But Arbitrum One has Timeboost live and a passed DAO vote to move to PGAs, and Robinhood Chain runs the same stack. The discipline is named sequencer-edge engineering rather than FCFS engineering so that it survives either change. The sequencer is still the venue and its ingress is still where things land. What changes is which levers exist.

If Timeboost arrives:

A per-round auction for an express lane appears. Winning it buys sequencing ahead of everyone else for that round.
If Timeboost behaves here as it does on Arbitrum One, latency would still matter for whoever holds the lane and for everyone on the non-express path. BLCK has not verified the mechanics and would measure them first.
blck-arb would need a bid model and a way to price a round. blck-probe would need a mode that times the non-express path.
The feed would start carrying blockMetadata that is not null, and receipts would gain a timeboosted field. Today every captured feed message has blockMetadata: null and receipts have no such field.

If a priority gas auction arrives:

Fee becomes a second lever alongside latency. eth_maxPriorityFeePerGas stops returning 0.
A reverted transaction costs its priority fee as well as its gas. Simulation must price the cost of losing, not only the cost of executing.
Whether a paid fast feed comes with it, as voted for Arbitrum One, is unknown for Robinhood Chain. If it did, feed latency would be tiered and BLCK's feed measurements would need a paid-tier column.

How you would notice, from the outside:

timeboost_ or auctioneer_ RPC namespaces appear. They are absent today.
blockMetadata in feed messages stops being null.
Receipts gain a timeboosted field.
eth_maxPriorityFeePerGas returns a non-zero value.
The docs line stating that priority gas auctions do not exist here is removed.

Until one of those happens, every strategy in BLCK assumes pure FCFS, and everything you know about tips, bundles, and leaders stays in this document.