2027 protocol upgrade ideas

#1

To continue a bit of a tradition (2021-2023, 2026), this thread is to discuss our collective 2027 upgrade wishlist.

Jeremy, Ryan, Fiendish, and I briefly discussed our opinions on the current CHIP landscape on the 2026 end of year BCH Podcast episode. At the time of writing, it seems that CHIP-2025-03 Faster Blocks for Bitcoin Cash is a potential candidate for the 2027 upgrade cycle, but the CHIP is not complete nor does it have clearly unanimous consensus.

I don’t believe any other CHIP is “on-track” at this time, but that could change. There’s also the potential for 2027 to be a “no-op” year, which may be of some benefit purely to demonstrate discipline in our upgrade process.

Some other notable CHIPs to review and discuss:

All of these CHIPs are currently incomplete and lacking consensus, but may be of interest for further research and development.

An interesting observation: searching this forum for “CHIP” shows how far we’ve come… I would almost believe that if BCH were to ossify today, we’d still be in a great position. The search also shows that we peaked in development activity between 2023 and 2025 - there are only a few new or outstanding CHIPs that have been formally proposed and NOT merged or withdrawn at this point.

On a personal note, I’d like to poke at the idea of “OP_PFX” for purchasing more VM compute budget without inflating script sizes… and I have an inkling that it may be acceptable to raise the OP_RETURN limit to fill up to the maximum transaction size of 100,000 bytes (where OP_RETURN would NOT purchase additional VM compute). Just want to bring these topics up for discussion :slight_smile:

Total aside: when should we fix the 2106 problem? :grin:

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#2

Today I’ve been looking into TXv5 in more depth in order to better understand its current status.

The TXv5 CHIP currently aims for mainnet deployment in May 2027. But the CHIP author asserts that if the cost of introducing a new transaction format is too high in 2027, there is still value to be gained by considering some of its components:

CHIP-2025-01 TXv5: Transaction Version 5 - #6 by bitjson

…two components could reasonably be extracted from TXv5 (if BCH doesn’t have sufficient market dominance by 2026 to lock-in a transaction format upgrade), making this into 3 CHIPs:

  1. Read-only inputs – the implementation in the CHIP is already backwards compatible, the TXv5 part just adds a more efficient encoding
  2. Unified bytecode length limits
  3. The v5 encoding itself (everything else in this CHIP)

If an improved encoding format still looks too disruptive in early 2026, I’ll just propose the smaller, backwards-compatible items (1 and 2) for 2027, and re-propose the v5 encoding for 2028.

#3

For anyone interested in this, it’s elaborated here: CHIP 2021-05 Targeted Virtual Machine Limits - #137 by bitcoincashautist

Since you highlighted this aspect, it prompted a few thoughts. It already doesn’t purchase VM compute budget (but in the past VM limits CHIP iteration, a shared TX budget, it would’ve). But why shouldn’t it be able to “purchase” budget? The objective of VM limits is to control CPU density per byte to avoid hot spots, and all outputs are “dumb” bytes and reduce CPU density of the TX because they don’t contribute to budget so they dilute TX’s CPU load. But maybe we could include them: sum all output bytes and divide by number of inputs then add that to each input’s budget. Or, any PREFIX_EXTRA_BUDGET invoked would first “claim” bytes from these currently unclaimed places in the TX, before claiming imaginary bytes (which would count against TX size and block size limits, just not be encoded anywhere and use bandwidth for nothing).

But I’m not sure if all this will really be needed, because a bunch of 0s from a data push are highly compressible and could be transmitted over network in compressed form.

#4

This may be very positive for the growing of the community. Having new stuff every year makes people already there excited, but it doesn’t do much for attracting new blood. Stability and a good base will have a lot of positive influence to allow builders to build and not lose the footing.