{"upgrades":[{"date":"2016-10-28","height":0,"label":"Genesis","kind":"launch","version":"Sprout","summary":"Launch with the Sprout shielded pool and a slow-start subsidy.","changes":["JoinSplit-based shielded transactions","Equihash 200,9 proof of work","20% founders' reward for four years"]},{"date":"2018-06-25","height":347500,"label":"Overwinter","kind":"upgrade","version":"v2","summary":"Groundwork for upgrades: versioned transactions, replay protection, expiry heights.","changes":["Transaction version 3","Transaction expiry","Signature hashing rework"]},{"date":"2018-10-28","height":419200,"label":"Sapling","kind":"upgrade","version":"v4","summary":"Shielded transactions become practical on phones: proofs in seconds, not minutes.","changes":["Sapling pool with Groth16 proofs","Separate viewing and spending keys","Hardware-wallet friendly signing"]},{"date":"2019-12-11","height":653600,"label":"Blossom","kind":"upgrade","version":"v4","summary":"Block time halves to 75 seconds; subsidy halves with it so issuance is unchanged.","changes":["75 s target block time","Subsidy 6.25 ZEC per block"]},{"date":"2020-07-16","height":903000,"label":"Heartwood","kind":"upgrade","version":"v4","summary":"Miners can receive rewards directly to shielded addresses; flyclient-friendly headers.","changes":["Shielded coinbase","Chain history commitments in block headers"]},{"date":"2020-11-18","height":1046400,"label":"Canopy","kind":"halving","version":"v4","summary":"First halving; founders' reward ends and the ZIP-1014 development fund begins.","changes":["Subsidy 3.125 ZEC","Dev fund 20% (ECC / ZF / grants)","Sprout deposits disabled"]},{"date":"2022-05-31","height":1687104,"label":"NU5","kind":"upgrade","version":"v5","summary":"Orchard: a trusted-setup-free pool built on Halo 2, and unified addresses to hide the pool choice.","changes":["Orchard pool (Halo 2)","Unified addresses","Transaction version 5"]},{"date":"2024-11-23","height":2726400,"label":"NU6","kind":"halving","version":"v5","summary":"Second halving; part of the subsidy now accrues to a consensus-enforced lockbox.","changes":["Subsidy 1.5625 ZEC","Lockbox 12% · grants 8%","Deferred dev fund"]},{"date":"2025-11-24","height":3146400,"label":"NU6.1","kind":"upgrade","version":"v5","summary":"First lockbox disbursement under an upgrade-adopted rule.","changes":["78,750 ZEC released to grants","Disbursement mechanism"]},{"date":"2026-06-05","height":3367900,"label":"Orchard emergency fix","kind":"upgrade","version":"v5","summary":"A value-balance flaw in the Orchard proving circuit — present since 2022 and capable of minting counterfeit shielded notes — was disclosed by Shielded Labs and patched under an emergency upgrade. ZEC fell around 38% on the news.","changes":["Circuit soundness fix","Emergency hard fork","Turnstile monitoring"]},{"date":"2026-07-28","height":3428143,"label":"NU6.3 — Ironwood","kind":"upgrade","version":"v5+","summary":"A fresh shielded pool with the fixed circuit baked in, so value can be re-proven as it crosses. Orchard drains through the turnstile into it.","changes":["Ironwood pool","Orchard → Ironwood turnstile migration","zcashd end-of-life; Zebra or Zakura required"]}]}