Session 15. Defend the capstone — Fri 02 Oct

Conclusion

You opened a store on Solana devnet, wrote a buyer that pins what was asked before any bytes exist, and defended it while the judge tried to make it sign something else.

What you can now do

A short list, because each item is real:

• read a program's accounts through Gecko instead of guessing them
• pin a request before anything can change it
• compare a prepared transaction with the request, field by field, as addresses and whole numbers
• sign only after every check agrees, with a key that never leaves your machine
• prove a purchase landed from two ledger reads, not from a success message
• serve your check as a small MCP server that refuses a private URL
• say what would change your mind

What this course did not make you

Someone who has run a payment system in production for a year. The capstone is a bounded prototype with its controls visible: one unit per purchase, three espressos on mainnet, and a check that trusts your pin. That is a more honest claim than "production ready".

What comes next

Your store stays on devnet, and your repository is yours. The depth track, the cookbook and the optional bonus units are all still here after the cohort ends.