Look first at relevant experience, not the size of the portfolio. Ask for three or four engagements that resemble your domain and your stack, and then ask whether those engineers are still with the staff augmentation company. A solid partner will introduce you to the tech lead. Evasive answers at this stage usually mean the demo work came from somewhere else.
The paperwork warrants more scrutiny than the proposal. Three sections matter more than the rest: assignment of intellectual property, confidentiality, and notice periods and handover. Every artifact has to transfer to you once invoices are settled, along with documentation, pipelines and deployment scripts. Look closely at wording that keeps so-called reusable libraries in the vendor’s hands, as it is usually the dependency that makes switching painful.
Find out how the estimate was built. An honest estimate arrives with the assumptions behind it, a task-level breakdown and a best case difference between laravel and django a worst case. A fixed-price contract only makes sense when the scope is genuinely frozen; otherwise the provider prices the risk in and you fund the buffer regardless. A time-and-materials model moves the risk back to the client, business process automation company so it requires visible weekly reporting and a spending cap.
Process matters as much as headcount. Establish how a new requirement enters the plan, who writes the acceptance criteria and how testing is organised. A team should be able to demonstrate a working build every one or two weeks. Written acceptance criteria stay your only real protection against an argument at delivery time.
Finally, plan for the end of the engagement before it becomes urgent. Insist that the repository sits under your account from the first commit, and that documentation is written as you go rather than left to the end. A provider confident in its own work says yes immediately; a long negotiation over it says quite a lot.