Quick answer: post-launch guide testing reports that Change Specialization unlocks at Cycle 3. From the Personnel/Focus Tree systems you can change eligible Operators' Specializations and refund Focus Points spent through the class tree. Custom recruits can also be reshaped more extensively, including Talent changes.
Where the respec system fits
The Personnel Facility is the roster-management hub for combat stats, Bonds and the Focus Tree. Official Bit Reactor community material says players can change most Operators' Specializations there to fit their preferred playstyle. That confirms respec is an intended system rather than a glitch or one-time campaign reward.
When does it unlock?
PC Gamer's launch guide places the Change Specialization option at Cycle 3. That is early enough that your opening Hawks choice should be treated as a learning decision, not a permanent commitment.
What happens to Focus Points?
Changing class refunds Focus Points spent in the Specialization tree according to post-launch testing. Story-character Talents have an important caveat: points placed into the fixed Talent at the top of an authored character's tree are not handled like freely changeable custom-recruit Talent investment.
Because exact UI wording can vary with Operator type, review the refund preview before confirming a respec. The system is generous, but authored and custom characters are not identical.
Best reasons to respec
Respec when your squad has role duplication, your weapon/AP pattern feels wrong, a new Operator fills an old niche better, or a mission chain demands a different range/support mix. Do not respec solely because a tier list moved one class from S to A; change when the new role solves a real roster problem.
A low-risk way to test a new build
Before changing several Operators at once, respec one role and run a mission that exercises the intended job: long sight lines for Sharpshooter, close pressure for Assault, sustained fire for Heavy/Gunslinger or support-heavy encounters for Medic. That makes it easier to tell whether the class change solved the problem instead of confusing the result with simultaneous weapon and roster changes.
Respec does not erase squad relationships
Specialization changes are part of roster development rather than a full character reset. Bonds and the broader identity of an authored Operator remain separate systems. This is useful when a favorite relationship pair is working well but one member's combat role overlaps too heavily with a newly recruited specialist.