A number produced without questions should be treated as a red flag rather than good service. Any serious team responds with a list of questions: about integrations. A vendor affiliate software development company that prices before understanding the scope is working from a template, and a guess will be corrected later — and you will pay for it.
Look out for any distance between the people you meet and symfony vs spring boot the developers actually assigned. Insist on named engineers in the contract, with wording that requires notice before anyone is swapped. A provider that talks only about roles and will not commit to individuals is preserving its own flexibility at your cost.
Insist on commit-level visibility from the start. A provider that delivers a build only at the end of each phase is asking you to accept a black box. Daily commits tell you who is really on the project far better than a slide deck. The same holds for the CI pipeline: if there is no pipeline, quality claims are unverifiable.
Loose phrasing around code ownership is rarely an accident. The agreement should state plainly that the code, designs and documentation become the property of your company on payment. Look too at which country’s law applies and how payments are structured: a request for most of the money up front with nothing due in return for weeks takes away the only leverage you have.
Lastly, examine how they communicate. Establish how much working-time overlap the teams will share each day, which named person answers day-to-day questions and on what response times. Four hours of overlap generally works; zero overlap stretches a five-minute question into a twenty-four hour round trip. Unclear written communication in the sales phase does not improve once the work starts.