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AI 302 · Module 4

Verification, Human-in-the-Loop & Control Gates

Which results may continue automatically, and which must be confirmed first?

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Learning objectives

  • Distinguish verification and validation, and describe quality, safety and policy gates
  • Describe the gate model with its four outcomes: pass, retry, human review and fail
  • Choose a suitable verification source: rule, schema, trusted source, second-model evaluation, policy check or human review
  • Explain the human control patterns: review before action, approval before irreversible action, escalation on uncertainty and override
  • Set evidence requirements, confidence and risk thresholds, and safe stop conditions
  • Decide for each action whether it is auto-continue, auto-verify, human review, human approval or prohibited, and produce a Verification & HITL Gate Map

Problem and need

8 min

The output looks fine. Should the run just continue?

In Module 3 you made a run able to continue after an interruption. A run that continues reliably will also continue reliably with a wrong result. The core question of this module is: which results may continue automatically, and which must be confirmed first?

Work scenario (simulated)

A workflow drafts reply notices and passes each draft straight to the sending step. One draft cites a deadline that the source policy does not contain. The format is perfect, so nothing flags it. The notice goes out, and the department spends a week correcting the mistake with the recipients.

  • Good format does not mean correct content
  • Some checks a program can do; some need a person
  • Not every action needs the same level of checking
  • Where the checks sit is a design decision made in the harness

Warning

Do not design a flow in which high-impact AI output is accepted without review. Human-AI-Human means a person stays responsible for what is sent, changed or decided.

Key takeaway: Reliable continuation is not enough. Decide which results can move on automatically and which must be checked or approved first.

Gates and verification

9 min

The gate model: pass, retry, human, fail

A gate is a check placed between steps. Verification asks whether the output is right. Validation asks whether it meets the need it was made for. A gate applies these checks and decides what happens next. Gates come in kinds: a quality gate checks whether the result is good enough, a safety gate checks whether it could cause harm, and a policy gate checks whether it follows the rules.

The gate model
  1. Agent Output: the result to be checked
  2. Verification Gate: apply the checks
  3. PASS: continue to the next step
  4. RETRY: try the step again (details in Module 5)
  5. HUMAN: send to human review
  6. FAIL: stop, or move to recovery

Text equivalent: the output enters a gate. The gate has four possible outcomes. Pass means the run continues. Retry means the step is attempted again. Human means a person reviews before anything continues. Fail means the run stops or moves to recovery. The gate never leaves the result in an undefined state.

Kinds of gate (simulated)
GateQuestion it asksExample
Quality gateIs the result good enough?Reply is complete and answers the question
Safety gateCould this cause harm?Reply does not expose personal data
Policy gateDoes it follow the rules?Reply does not promise an exception
Check yourself

Why does a gate have four outcomes (pass, retry, human, fail) rather than only pass and fail?

Why does a gate have four outcomes (pass, retry, human, fail) rather than only pass and fail?

Key takeaway: A gate checks the output and decides one of four outcomes: pass, retry, human review or fail.

9 min

Where does verification come from?

A gate is only as good as the check behind it. Different sources of verification suit different questions, and they can be combined. Prefer the most reliable source that fits the question, and do not treat a model checking itself as strong evidence on its own.

Verification sources (simulated)
SourceGood forLimit
Deterministic ruleClear yes or no checks, such as a date range or required fieldCannot judge meaning
Schema validationChecking structure and types of an outputSays nothing about whether the content is true
Trusted source comparisonChecking a claim against an approved documentOnly as good as the source and its currency
Second-model evaluationJudging quality or consistency at scaleCan share the same blind spots; not proof
Policy checkChecking against written rulesRules may not cover every case
Human reviewJudgment, context and accountabilitySlower and costs attention

Cheap and fast checks

  • Rules, schema and policy checks run automatically
  • Good for catching clear errors early
  • Cannot decide what needs judgment

Judgment checks

  • Second-model evaluation and human review
  • Good for meaning, tone and context
  • Use where the impact justifies the cost
Check yourself

A draft cites a deadline. Which verification source best checks that the deadline is correct?

A draft cites a deadline. Which verification source best checks that the deadline is correct?

Key takeaway: Match the verification source to the question, combine sources, and do not rely on a model vouching for itself.

Human control

9 min

Human-in-the-Loop: review, approval, escalation, override

Human-in-the-Loop means designing the points where a person takes part. It is not a vague promise that someone is watching. Each pattern has a clear trigger and a clear action for the person, and the run keeps an approval state so it is known what was decided.

Human control patterns (simulated)
PatternWhen it appliesExample
Review before actionA person looks at the result before the run continuesA staff member reads a draft before it is used
Approval before irreversible actionA person must say yes before something that cannot be undoneApproval before an official notice is sent
Escalation on uncertaintyThe system is not sure, so it hands the decision to a personTwo sources disagree, so a person decides
Override on policy or operational needA person may change or stop what the system would doA manager pauses a batch during a policy change

Approval state: a run waiting for a person should be visibly paused, with a record of who approved or rejected, when, and on what evidence. Combined with Module 3, a paused run is a run that has been checkpointed and can resume once the person decides.

Info

A person who only clicks approve without the evidence is not a real gate. Give the reviewer what they need to decide: the output, the sources, and the reason it was flagged.
Check yourself

Which human control pattern fits an action that sends an official notice and cannot be undone?

Which human control pattern fits an action that sends an official notice and cannot be undone?

Key takeaway: Design human control as clear patterns, with an approval state and the evidence a reviewer needs.

Thresholds and safe stop

9 min

Evidence, thresholds and safe stop

To decide which outcome a gate gives, the design needs rules. Three ideas help: what evidence is required, what confidence is high enough, and what risk is too high to continue without a person.

Rules that drive a gate (simulated)
IdeaWhat it meansExample
Evidence requirementWhat must be shown before the result may passEvery claim cites a source paragraph
Confidence thresholdHow sure the check must be to pass automaticallyBelow the threshold, send to human review
Risk thresholdHow much impact is allowed without a personAnything that changes a record goes to approval
Safe stop conditionWhen the run must stop rather than guessSources conflict and no person is available
A gate with thresholds
  1. Output arrives with its evidence
  2. Evidence missing: FAIL or RETRY
  3. Risk above threshold: HUMAN approval
  4. Confidence below threshold: HUMAN review
  5. Otherwise: PASS and continue

Text equivalent: the gate first checks that evidence is present. High risk sends the result to a person for approval. Low confidence sends it to a person for review. Only a result that clears all of these passes automatically. A confidence score alone is not enough, since it can be wrong.

Info

A safe stop is a valid outcome. Stopping with a clear reason is better than continuing on a guess. This module covers the gate decision. What to do after a stop or a failure, including retry policy and recovery, is Module 5.
Check yourself

A result has high confidence but would change an official record. What should the gate do?

A result has high confidence but would change an official record. What should the gate do?

Key takeaway: Set evidence requirements, confidence and risk thresholds, and safe stop conditions so gate decisions are explicit.

Practice and apply

11 min

Practice: Automatic or Human Gate?

Activity 4 is called Automatic or Human Gate? First work the example, then do it for your own workflow. Please do not enter real company secrets, client personal data or any unauthorized sensitive information in this exercise.

Worked example (simulated). Request reply workflow
ActionDecisionReason
Copy the request text into the working stateAuto-continueLow risk and fully reversible
Check that the reply has all required fieldsAuto-verifyA deterministic rule can decide
Check the deadline in the reply against the policy documentAuto-verify, with human review if they differA trusted source exists, but a mismatch needs judgment
Send the official reply to a recipientRequire human approvalIrreversible and affects a real person
Promise an exception to the deadlineProhibitNot the workflow's decision to make, only a person with authority may do it
  1. List the actions
    Write the actions in your workflow that produce output or change something.
  2. Choose a gate for each
    Choose one: auto-continue, auto-verify, require human review, require human approval, or prohibit. Give a reason.
  3. Name the verification source
    For each auto-verify action, name the source (rule, schema, trusted source, second model or policy check) and the threshold.
  4. Define stop and escalation
    For each human gate, say what the reviewer sees, what the approval state is, and the safe stop condition if nobody responds.

Info

Deliverable: the Verification & HITL Gate Map, showing each action, its gate decision, the verification source, thresholds, the human role and the safe stop condition. It becomes part of your Agent Harness & Reliability Canvas.
Check yourself

In the worked example, why is sending the official reply set to require human approval?

In the worked example, why is sending the official reply set to require human approval?

Key takeaway: Human-AI-Human: a person decides which actions need a gate, automatic checks catch clear errors, and a person approves high-impact actions and stays responsible.

What next?