What changes
Start with what this is not. Attain OS does not host code, run builds, or review diffs. GitHub, GitLab, your CI and your deploy tooling stay exactly as they are. What it replaces is the pile of separate products you use for everything that surrounds them, and the manual copying between those products that currently happens in someone's head.
One work item carries its whole history. A backlog item holds the spec that defines it, the decision record behind it, the support tickets that motivated it, the sprint it was pulled into, the owner, and what closed it. Nobody has to hold four tabs open to answer why are we building this, or what happened to the thing we said we would build.
The loop closes back to the customer. Support conversations and reported bugs become triaged items rather than a parallel universe of complaints, and what shipped becomes a release write-up drafted from the items that actually closed. Atty does the drafting: the release note, the status summary for sales, the ticket triage first pass. A human decides.
Planning stops starting with archaeology
Because the item, its spec, its tickets and its outcome are the same record, the first half of every planning session stops being reconstruction. The status a stakeholder wants is already assembled, so answering it does not cost an engineer a context switch.
One workspace instead of a tracker, a wiki, a help desk and a CRM
The backlog tool, the docs tool, the support desk, the customer records, the boards and the team chat are built in and already connected. You stop paying separate vendors for pieces of the same workflow, and you stop paying the quieter cost of duplicate work: two engineers fixing the same reported bug because it arrived through two doors.
Owner, blocker and ship date are on the record
Every item shows who has it, what it is waiting on, and when it closed. Commitments to support and sales become linked items rather than promises in a channel, so when a date moves, the people who told a customer about it can see that it moved.
Add scope without adding a coordination layer
Teams usually add a program manager because the information does not flow, not because there is more thinking to do. When the backlog, the docs, the tickets and the customer record live together and Atty writes the summaries, the same team can carry more surface area before it needs a dedicated person to move information between tools.