Construction, energy retrofit, aviation, and clinical research all separate the point at which work becomes usable from the point at which it is finally accepted, and all four hold the builder to something across the gap. Software handover collapses those into a single date, which is the structural difference worth borrowing against.
Two milestones and a list
Practical completion is a contract-dependent milestone at which work is usable while items remain outstanding. Snagging records those items and their disposition.
Public construction guidance seeking zero-defect delivery still provides for an agreed schedule of visible defects with remediation estimates at handover, and leaves possession and handover compliance to the contract. Federal energy contracting goes further and distinguishes a technical representative’s sign-off from official agency acceptance, permitting conditional acceptance where seasonal testing is documented.
That last distinction is the transferable one. Acknowledging receipt, approving technical evidence, and making contractual acceptance are three acts. They need explicit meanings even when one person performs all three, because collapsing them is how a project acquires an acceptance nobody intended to give.
Four item states, not one
Calling everything a snag conceals the differences that matter. Four states, with different evidence and different consequences.
Demonstrated. The version, conditions, result, and witness are recorded, and the demonstration counts within its tested scope.
Failed. The failure, the affected users, the consequence, and the proposed remedy are recorded. It is resolved, or a valid change or exception decision is obtained, before acceptance rests on it.
Deferred. The missing observation, the reason, the future conditions, and a date. What remains unknown is stated, along with who carries the interim responsibility.
Changed. An authorised change with a revised evaluation, with the original history preserved. Relabelling a failure as an original pass is the specific move this prevents.
A reporting service that has passed routine access checks while its year-end workflow has only been simulated has one deferred item, and its record says year-end evidence deferred rather than claiming observed success. A failed access-control check on the same service is a failure requiring action. Filing both as snags loses that.
A decision owner cannot use any of this to waive a duty the governing rules do not permit them to waive.
Liability across the gap
The defects liability period is the mechanism construction uses to keep the builder engaged after handover, and its shape is instructive even though its durations are not portable.
One federal construction warranty runs for a year from final acceptance, or from earlier government possession of a part, with repaired or replaced work receiving a year from the repair. Written notice and scope exceptions both matter.
Two features carry over. The clock can restart on repair, so a remedied defect is not thereby closed for good. And expiry leaves some rights intact: the same clause preserves inspection and acceptance rights concerning latent defects, gross mistakes, or fraud, and allows later enforcement of supplier warranties.
For a software transfer, six things stay separate in the record: what activates the duty, what is covered, how a defect is raised, what happens next, what survives the milestone, and what happens to the warranty clock when a repair changes the asset.
The failure mode is treating hypercare as warranty. A team that ends enhanced support after its exit checks, with a reported defect still open, has made a staffing decision. Whether the defect remains covered and what remedy is due comes from the agreement, and the obligation needs assigning and funding rather than lapsing with the rota.
Readiness ladders stage maturity, not acceptance
Technology readiness scales describe demonstrations in progressively more realistic environments, and prototype and demonstration language appears inside those scales at several levels rather than beneath them.
They answer a different question from acceptance. A system can sit high on a readiness scale and have no receiving organisation, no operating owner, and no accepted responsibility — which is precisely the state a successful prototype reaches by default.
So the two structures compose rather than compete: readiness describes how thoroughly something has been demonstrated, and acceptance describes who has agreed to own it. A programme tracking only the first arrives at handover with a mature system and an unanswered question.
The rule
What stays fixed is that outstanding items each carry a state, an owner, and a verification step, and that acceptance is an act by a named authority rather than the passage of a date. What changes is which items block this particular transfer, which is a judgement about intended use rather than about severity in the abstract.
Not to be confused with
A legal test. Practical completion has no universal definition here, and no holding from any jurisdiction is asserted. The exact contract terms define completion, exceptions, and acceptance authority.
Cosmetic defects. Snagging is a record, not a severity classification. An item on the list can prevent the intended use entirely.