Connecting Pantheon to the systems a business actually runs — webshops, tills, marketplaces and reporting — so there is one set of numbers instead of several.
In the businesses I work with, Pantheon is where stock is counted, prices are set, partners live and the year gets closed. Everything else in the company is downstream of it, whether or not anybody designed it that way. The webshop, the till, the marketplace listing and the spreadsheet the owner actually trusts are all opinions about the same numbers.
The work is making those opinions agree. Items, variants, price lists, stock and partners move out; orders, invoices and receipts move back in. The direction is the whole design: one system has to be allowed to be authoritative, and it is never the storefront. Once that is settled, most of the arguing stops and what is left is plumbing.
The plumbing is where it goes wrong, though, and always in the same few ways. A sync that half-completes and reports success. A price list that applies from a different moment than the shop believes. A stock figure that is technically correct and practically useless because it counts goods already reserved for someone else. So the jobs are built to be idempotent — running one twice must be indistinguishable from running it once — and to be loud when they do not run at all, because the silent failure is the expensive one.
No client is named on this island on purpose. It is the pattern rather than any single engagement, and the pattern is the part that transfers.