The Developer That Brought Back Bitcoin's Forgotten Code | With Ethan Heilman

As interest in Bitcoin Layer 2s skyrockets, the inclusion of OP_CAT — an opcode enabling concatenation of elements in the Bitcoin stack — has become a key technical upgrade to watch for its potential in the development of trustless bridges.

OP_CAT co-author @ethan_Heilman and I sat down to discuss debate around this opcode — including why it’s controversial, the cultural environment shaping its future, and why some worry its broad expressivity could pose “unknown risks” to Bitcoin over time.

More recently, Ethan co-authored BIP 360 with @cryptoquick — another controversial proposal aimed at addressing Bitcoin’s quantum vulnerabilities.

Suffice it to say, there are few people with Ethan's experience in navigating Bitcoin politics and its shifting governance landscape as we move towards ossification over time.

In this episode, we cover:

- The origins of OP_CAT and why it was included and removed from early Bitcoin

- What makes OP_CAT so powerful (and why that worries some developers)

- Cultural shifts in Bitcoin governance as its developer community matures

- The ‘great covenants debate’ + OPCAT vs. CTV- The path to BIP 360 and why Bitcoin should be ‘quantum ready’

This episode is powered by:

- Best In Slot (@bestinslotxyz), the leading API for Ordinals and BRC20 data aggregation and indexing

- Spark (@lightspark), a statechains implementation leading the path towards institutional adoption of Bitcoin-powered payments

- Citrea (@citrea_xyz), the leading Bitcoin Rollup technology and contributor to the BitVM alliance

📍 Timestamps

00:00 – Intro

00:45 – Bitcoin Privacy and the OP_CAT Proposal

03:18 – Technical Challenges of Adding New Opcodes

07:37 – Politics and Culture of Bitcoin Upgrades

28:46 – Quantum Computing Meets Bitcoin

37:48 – How Governments View Quantum Risk

39:06 – Breaking Down BIP 360 for Developers

42:03 – Post-Quantum Signature Schemes Explained

45:18 – Trade-offs in Quantum Security for Bitcoin

53:16 – Community Reactions to BIP 360

01:00:23 – The Future of Bitcoin in a Post Quantum World