Endpoint errors cannot be fixed after the fact, only by respeaking or a manual end

What it is

Once an endpoint commits, this turn’s “when it ended” is fixed. Too early, and the second half is not in the buffer; too late, and the wait is already spent, with later inserted noise possibly inside the hypothesis. Unlike substituting a word, an endpoint error cannot be corrected on the same hypothesis after the fact. What people can do is say it again, or next time manually confirm the end with a button or gesture, taking the decision back from the detector. That is operational irreversibility, not only the fact that audio was cut.

Why it happens

Commit triggers a final decode, possible execution, and a UI that is already “done.” There is no standard control for “nudge the endpoint 400 ms later and decode again,” because the product has closed the request. A late end could in theory be redecoded from a longer buffer, but the interaction clock has moved and the user may already be listening to a reply. Engineering therefore treats endpointing as a one-shot. Recovery paths are a new turn (respeak), or an explicit end when the detector is untrusted (tap complete, release PTT, say an end-word). An end-word itself must be recognized and stacks another error. Irreversibility is a property of the protocol: the protocol has no primitive for “revise the endpoint.”

Studying it

Inject premature and late ends and measure whether people respeak, try to append orally, or go looking for a done button. Record time from noticing the endpoint error to successful recovery. Compare with and without an explicit end control. Do not only count words lost to truncation—that is the content layer; here the question is whether the protocol has a repair primitive.

Where it stops holding

Streaming stacks that keep a revocable “soft endpoint” before commit can still pull it back inside a short window; that is not yet commit. Meeting-transcription slices can be recut offline with no user in the loop. Hold-to-talk was manually ended from the start, so there is no detector miss to repair after the fact. Reading “cannot be fixed after the fact” as a ban on offering respeak is backwards: respeak is the main path because it cannot be fixed.

Applying it

• Always place an explicit complete/cancel control beside automatic endpointing so people can override the detector.
• If voice resumes immediately after commit, prefer “append to the last sentence” over treating it as an unrelated new command, to reduce full respeaking.
• In acceptance tests, force a premature seal and confirm recovery in two steps by respeak or manual end, rather than leaving people stuck on an already executed wrong command.

Related

• Same group: C7.09.1 Endpointing can use silence duration alone or jointly with semantic completeness · C7.09.2 Falling pitch and slowing rate can help decide that talk has ended · C7.09.3 A fixed silence threshold behaves inconsistently across speaking rates
• Adjacent: C7.02 Endpoint Detection · C7.03 Types of Recognition Errors
• Search: irreversible endpoint · manual endpoint · respeak