Lesson 06 · Unit 4 · Solana
Programs and upgrades
Smart contracts on Solana are called programs, and they follow the same rule as everything else: they live in accounts. One more field matters — the upgrade authority. If it is set, its holder can replace the program's code, for everyone, at any time. If it is burned, the code is frozen forever.
Upgradeable program
Authority burned
The code
Can change under you
Frozen forever — what you audited is what runs
Bugs
Can be fixed — and rules rewritten
Permanent, like the features
You trust
Whoever holds the authority
The code itself
The pattern you have now seen three times
Mint authority, freeze authority, upgrade authority — Solana's recurring question is always 'who still holds a pen over this account?' Every authority is a capability someone kept. Scanning is largely the art of finding kept pens.
Upgrade authority
The address allowed to replace a program's code. Burned means the program is immutable — for better and worse.
Where this goes next
A program that can be upgraded can change what a token does after you buy. Two later lessons show that in practice.