Use BuilderNet docs for refund rule

Author: sketsdever

docs/flashbots-auction/advanced/gas-fee-refunds.md

@@ -4,37 +4,37 @@ title: Gas Fee Refunds
 
 ## Introduction
 
-Searchers and private transaction API users are automatically eligible to receive gas fee refunds. If Flashbots can include a bundle on chain for a lower price, you are eligible to receive a refund.
+Searchers and private transaction API users are automatically eligible to receive gas fee refunds. If a bundle can be included on chain for a lower price, you are eligible to receive a refund.
 
 Gas fee refunds do not change how bundles are executed and searchers do not need to make any changes to be eligible for them.
 
 ## Where do refunds come from
 
 Gas fee refunds include both priority fees and coinbase transfers.
 
-In an optimal case, searchers are refunded the difference between their bid and the bid of the next-best bundle or transaction targeting the same state. Ie. the refund effectively results in the searcher paying the second price. In practice, searchers will receive some fraction of this amount depending on how much profit the Flashbots builder makes.
+In an optimal case, searchers are refunded the difference between their bid and the bid of the next-best bundle or transaction targeting the same state. Ie. the refund effectively results in the searcher paying the second price. In practice, searchers will receive some fraction of this amount depending on how much profit BuilderNet makes.
 
 ## Which bundles receive refunds
 
-Flashbots provides refunds for bundles in blocks landed by the Flashbots block builder. Whether a bundle receives a refund depends on a few factors that vary from block to block:
+Flashbots provides refunds for bundles in blocks landed by BuilderNet. Whether a bundle receives a refund depends on a few factors that vary from block to block:
 * How much network congestion and competition there was
-* Whether the Flashbots builder made a profit and how much
+* Whether BuilderNet made a profit and how much
 * How much the specific bundle contributed to the value of the block
-* If the bundle was sent directly to Flashbots, or shared with other block builders by the searcher
+* If the bundle was sent directly to Flashbots or BuilderNet, or shared with other block builders by the searcher
 
 Note that transactions seen in the public mempool are excluded and bundles containing only public mempool transactions do not receive refunds.
 
 ## How to maximize both refunds and speed
 
-Transactions which are sent directly to the Flashbots Builder via the Bundle Relay, and not multiplexed _by the searcher_ to other block builders, are likely to receive higher refunds. This is because they increase the profit of the Flashbots builder which is used to provide refunds.
+Transactions which are sent directly to the Flashbots Bundle Relay or BuilderNet, and not multiplexed _by the searcher_ to other block builders, are likely to receive higher refunds. This is because they increase the profit of BuilderNet which is used to provide refunds.
 
-The Flashbots block builder does not land 100% of blocks. In order to land bundles in all blocks, searchers can ask Flashbots to share their bundles with other block builders in cases where the Flashbots builder does not win a block. Flashbots will automatically share with all specified builders on the searcher's behalf.
+BuilderNet does not land 100% of blocks. In order to land bundles in all blocks, searchers can ask Flashbots to share their bundles with other block builders in cases where BuilderNet does not win a block. Flashbots will automatically share with all specified builders on the searcher's behalf.
 
 ### Smart multiplexing
 
 To share bundles with other builders, add the `builders` field to your `eth_sendBundle` request. The `builders` field accepts a list of strings which correspond to the "name" tags of [registered builders](https://github.com/flashbots/dowg/blob/main/builder-registrations.json).
 
-All `eth_sendBundle` requests are shared with the Flashbots builder. They are multiplexed to other block builders at the end of the slot if the Flashbots builder determines it will not win that block.
+All `eth_sendBundle` requests are shared with BuilderNet. They are multiplexed to other block builders at the end of the slot if BuilderNet determines it will not win that block.
 
 For example:
 
@@ -55,7 +55,7 @@ For example:
 }
 ```
 
-Searchers can also use `mev_sendBundle` to multiplex bundles if they prefer. Though this method is more complex and not necessary for gas fee refunds.
+Searchers can also use `mev_sendBundle` to multiplex bundles if they prefer. This method is more complex and not necessary for gas fee refunds.
 
 _Note: Smart multiplexing has a 1% rate of false positives, meaning that in 1% of MEV-Boost blocks there is a risk that searcher bundles will not be landed._
 
@@ -65,63 +65,15 @@ To view bundle stats on multiplexed `eth_sendBundle` requests, use the `flashbot
 
 ## How are refunds calculated
 
-The Flashbots builder uses a refund rule to retroactively calculate refunds for all bundles landed in its blocks.
-
-The refund rule aims to have bundles make the minimum net payment so that bidding optimally is as straight forward as possible. We do this by measuring the contribution of bundles above the other bundles the builder has received, and refunding as much of that as possible. 
-
-Bundles sent by the same signer will be treated as non-competitive.
-
-See the [explainer](https://collective.flashbots.net/t/refund-rule-wat-dis-how-to-and-faq/4049/2) for more details about how to bid and interact with the refund rule.
-
-### The Flat Tax Rule
-
-- **$B(T)$** is the most profitable block produced from bundles in $T$.
-- **$v(T)$** is the value of $B(T)$.
-- **$b_i(T)$** is the payment of all bundles sent by identity $i$ if block $B(T)$ is realized.
-- **$\mu_i(T) = \min\{b_i(T), v(T) - v(T \setminus \{i\})\}$** is the marginal contribution of all bundles sent by identity $i$ if $B(T)$ is realized. We bound the marginal contribution so that the net payment can't be negative.
-- **$c$** is the amount the builder pays to the proposer to win the block.
-  
-$$
-\phi_i(T, c) = \frac{\mu_i(T)}{\sum_j \mu_j(T)} \min\{v(B(T)) - c, \sum_j \mu_j(T)\}
-$$
-
-So the net payment per identity (assuming it's included) is $p_i(T) = b_i(B(T)) - \phi_i(T, c)$.
-
-Notice that if the block generates enough value after paying the proposer, everyone should be refunded their contribution, meaning everyone pays the minimum they need to pay to beat competition. 
-
-### Identity constraint
-
-To avoid the rule being gamed by submitting bundles from multiple identities, we impose an additional constraint that no set of identities can receive in total more refunds than they contribute to the block.
-
-For each set of identities $I$ we define
-
-$$
-\mu_I(T) = \min\{\sum_{i\in I} b_i(T), v(T) - v(T \setminus I)\},
-$$
-
-to be the joint marginal contribution of the identities in $I$ to the block. Then we choose rebates that are minimally different from the flat-tax rule subject to the constraint that they don't rebate a set of bundles more in total than its joint marginal contribution. This means the vector of rebates $\psi(T, c)$ solves
-
-$$
-\min_{r\in\mathbb{R}^n_+} \sum_i (r_i - \phi_i(T, c))^2
-$$
-
-$$
-\text{subject to} \sum_{i\in I} r_i \leq \mu_I(T) \text{ for each } I \subseteq B(T),
-$$
-
-$$
-\sum_i r_i \leq v(T) - c
-$$
-
-where $\phi(T, c)$ are the orginal flat-tax rebates as defined above.
+BuilderNet uses a refund rule to retroactively calculate refunds for all bundles landed in its blocks. For more information, see the [BuilderNet docs](https://buildernet.org/docs/refunds).
 
 ## Who receives refunds
 
 By default, the refund recipient is the signer used on the `eth_sendBundle`, `mev_sendBundle`, or `eth_sendPrivateTransaction` request. You can delegate your recipient to a different address using the `flashbots_setFeeRefundRecipient` API.
 
 ## How to track refunds
 
-Refunds are tracked from a start date of July 8, 2024. Refunds are sent to recipients in batches, the first batch originated from our builder address `0xdf99A0839818B3f120EBAC9B73f82B617Dc6A555` while newer batches originate from [`refunds.buildernet.eth`](https://etherscan.io/address/0x62a29205f7ff00f4233d9779c210150787638e7f). 
+Refunds are tracked from a start date of July 8, 2024. Refunds are sent to recipients in batches, the first batch originated from the Flashbots builder address `0xdf99A0839818B3f120EBAC9B73f82B617Dc6A555` while newer batches originate from [`refunds.buildernet.eth`](https://etherscan.io/address/0x62a29205f7ff00f4233d9779c210150787638e7f). 
 
 Track your refunds using the [`flashbots_getFeeRefundTotalsByRecipient`](/flashbots-auction/advanced/rpc-endpoint#flashbots_getfeerefundtotalsbyrecipient) RPC method or the [refund dashboard](https://app.hex.tech/9eb1e790-53f7-4c16-be76-4a22c1aa7d17/app/0c2d34ef-1304-481a-b3d6-b773ce9e0e19/latest) on Dune.