How to end a conversation with COMPLETE

Back to how-to guides Use this pattern when an agent finishes its work: it closes the session, or it finishes a bounded task and returns control to a supervisor.

Concept

COMPLETE means this agent is finished. What happens next depends on how the agent started.

Agent role	What COMPLETE does
Root agent, or a specialist entered with `RETURN: false`	The session ends. Later messages in the same session get the conversation-complete message. No agent runs.
Child entered with `RETURN: true`	The child returns to the supervisor. The session continues. The supervisor becomes active again.
Any agent, when the completion has `TERMINAL: false`	The response shows and the session stays open. The next message starts a fresh intent.

A specialist entered with RETURN: false cannot return with COMPLETE. To give control back to its supervisor, it needs a HANDOFF to that supervisor. See How to switch the active agent during a conversation.

Ways to complete

Way	Where you write it	When the runtime checks it
`COMPLETE:` conditions	The `COMPLETE:` section with `- WHEN:` items	After each reasoning turn, after a state change from `__set_context__`, after a delegate returns, and at flow checkpoints.
Flow `THEN: COMPLETE`	A flow step, an `ON_INPUT` branch, or `ON_EXHAUSTED: COMPLETE`	When the flow takes that transition.
Terminal flow step	A flow step with no `THEN`	When the step finishes. The runtime checks `COMPLETE:` conditions only. If none match, the step waits.
The model’s finish action	Nothing to write	A `RETURN: true` child that has tools can call it to finish its task.
`ON_ERROR` with `THEN: COMPLETE`	An `ON_ERROR` handler	When retries on a `GATHER` field in a flow step run out, the handler text shows and the agent ends.

Use the COMPLETE: section when the end depends on state. Use THEN: COMPLETE when a flow step knows it is the last step. Use both when the flow ends the agent and a condition ends it earlier.

Completion conditions

The runtime evaluates the WHEN text of each condition in the order you list them. The first match wins.
WHEN must be deterministic. A condition such as the customer is done is a compile error (PLAIN_ENGLISH_COMPLETE_WHEN). Use order_id IS SET or task_done == true.
The condition must read state that something writes: a GATHER field, a tool result mapping, a SET, or a returned field.
In a flow, the runtime checks conditions before an automatic advance only when the next step already ran in this turn. Forward steps run first, so a trivially true condition does not end the flow early.
A matching condition does not complete the agent while a CONSTRAINTS rule fails on the current state. The constraint ON_FAIL runs instead. The runtime withholds a completion three times, then releases it.
At a flow THEN: COMPLETE, the runtime checks HANDOFF conditions first. A matching route takes over instead of completing. A child that returns to a supervisor skips this check.

What the runtime does on COMPLETE

Applies the SET assignments of the matching condition.
Stores a snapshot of the session values when STORE is set.
Builds the message: the RESPOND text, or the default message, or nothing for a returning child.
Marks the agent complete. A root agent ends the session.
For a RETURN: true child, copies the ON_RETURN MAP values to the supervisor and makes the supervisor active.

Message rules:

A COMPLETE condition with no RESPOND shows the default message This conversation has been completed. Set conversation_complete in MESSAGES to change it.
A returning child with no RESPOND returns silently. The supervisor continues the conversation.
In a reasoning agent, a matching completion replaces the model text for that turn. Put the whole closing message in RESPOND.
MODEL_CONTEXT keeps different text for later model calls than the customer saw.

Minimal working example

The agent collects a payment amount and ends the session with a confirmation. payment_amount comes from the GATHER field.

AGENT: Payment_Agent
GOAL: "Take a payment amount and confirm it"

GATHER:
  payment_amount:
    PROMPT: "How much do you want to pay in dollars?"
    TYPE: number
    REQUIRED: true

COMPLETE:
  - WHEN: payment_amount IS SET
    RESPOND: "Your payment of {{payment_amount}} dollars is scheduled."

How it works

The customer answers the prompt. The runtime stores payment_amount.
After the turn, the runtime evaluates payment_amount IS SET. The result is true.
The runtime checks CONSTRAINTS. The agent has none.
The runtime marks the agent complete and shows the RESPOND text with the amount filled in.
This agent is the root agent. The session ends.
A later message in the same session gets This conversation has been completed. The customer must start a new session.

Common variations

End from a flow step

A flow step with THEN: COMPLETE shows its RESPOND text and ends the agent in the same turn. The agent does not wait for the customer.

AGENT: Order_Lookup_Agent
GOAL: "Collect an order ID, confirm it, and end the conversation"

FLOW:
  entry_point: ask_order
  steps:
    - ask_order
    - confirm_order

ask_order:
  REASONING: false
  GATHER:
    order_id:
      PROMPT: "What is your order ID?"
      TYPE: string
      REQUIRED: true
  THEN: confirm_order

confirm_order:
  REASONING: false
  RESPOND: "Order {{order_id}} is confirmed. Goodbye."
  THEN: COMPLETE

Do not end an entry step with RESPOND and THEN: COMPLETE when the customer must answer. The agent completes before the customer replies. Use GATHER so the step waits. If the agent also has a COMPLETE: section, a matching condition runs at THEN: COMPLETE. Keep the closing text in one place.

Return a child to its supervisor

A child entered with RETURN: true completes with a condition. The supervisor keeps the session and routes the next request. Customer_Lookup_Agent has no RESPOND, so it returns silently. customer_id comes from its GATHER field and returns through MAP. Account_Service_Agent is a stand-in for your specialist.

SUPERVISOR: Account_Supervisor
GOAL: "Identify the customer first, then route account requests"

MEMORY:
  session:
    - customer_id
      TYPE: string
      DESCRIPTION: "Customer identifier collected by the lookup agent."

INTENTS:
  account_service: "Profile, address, or password changes."

HANDOFF:
  - TO: Customer_Lookup_Agent
    WHEN: customer_id IS NOT SET
    SUMMARY: "Collect the customer ID before any account work."
    RETURN: true
    ON_RETURN:
      action: continue
      MAP:
        customer_id: customer_id

  - TO: Account_Service_Agent
    WHEN: intent.category == "account_service" AND customer_id IS SET
    PASS: [customer_id]
    SUMMARY: "Account service agent now owns the conversation."
    RETURN: false

AGENT: Customer_Lookup_Agent
GOAL: "Collect the customer ID and return it to the supervisor"

GATHER:
  customer_id:
    PROMPT: "What is your customer ID?"
    TYPE: string
    REQUIRED: true

COMPLETE:
  - WHEN: customer_id IS SET

AGENT: Account_Service_Agent
GOAL: "Record an address change request"

GATHER:
  new_address:
    PROMPT: "What is the new address?"
    TYPE: string
    REQUIRED: true

COMPLETE:
  - WHEN: new_address IS SET
    RESPOND: "I recorded your new address: {{new_address}}."

When Customer_Lookup_Agent completes, the session does not end. The supervisor becomes active and continues. When Account_Service_Agent completes, the session ends, because it was entered with RETURN: false. For the return mechanics, ON_RETURN options, and replay of the original request, see How to switch the active agent during a conversation and How to transfer control to another agent and return later.

Show a closing message without ending the session

Set TERMINAL: false to render a closing message or widget and keep the session open. Clear the condition with SET in the same completion. Otherwise it fires again on the next turn.

AGENT: Order_Status_Agent
GOAL: "Show the order summary once without ending the conversation"

ON_START:
  SET: summary_shown = false

GATHER:
  order_id:
    PROMPT: "What is your order ID?"
    TYPE: string
    REQUIRED: true

MEMORY:
  session:
    - summary_shown
      TYPE: boolean
      DESCRIPTION: "True after the order summary was shown."

COMPLETE:
  - WHEN: order_id IS SET AND summary_shown != true
    RESPOND: "Order {{order_id}} shipped. Is there anything else?"
    SET: summary_shown = true
    TERMINAL: false

Write SET on one line: SET: summary_shown = true. A SET: followed by indented lines is ignored with warning W360. After this completion, the next message reopens the agent as a fresh intent. If the same condition fires again on the first turn after reopening, the runtime ends the session and logs NON_TERMINAL_COMPLETION_NO_PROGRESS.

Hold a completion until a rule passes

A completion does not fire while a blocking CONSTRAINTS rule fails on the current state. The rule ON_FAIL runs instead.

AGENT: Refund_Agent
GOAL: "Record a refund only after the customer gives consent"

GATHER:
  consent_given:
    PROMPT: "Do you agree to the refund terms? Answer yes or no."
    TYPE: boolean
    REQUIRED: true
  refund_amount:
    PROMPT: "How much is the refund in dollars?"
    TYPE: number
    REQUIRED: true

CONSTRAINTS:
  - REQUIRE consent_given != false
    ON_FAIL: "I cannot continue without your consent to the refund terms."

COMPLETE:
  - WHEN: refund_amount IS SET
    RESPOND: "Your refund of {{refund_amount}} dollars is recorded."

If the customer answers no, the completion is withheld and the rule message shows. The runtime releases a withheld completion after three withholds in a row. Give the customer a way to pass the rule.

Store a snapshot, keep model context, and set the default message

STORE saves a snapshot of the session values under a name. MODEL_CONTEXT keeps text for the model that differs from the customer text. A condition with no RESPOND shows the conversation_complete message.

AGENT: Payment_Agent
GOAL: "Take a payment amount and confirm it"

MESSAGES:
  conversation_complete: "This session is closed. Start a new chat for more help."

GATHER:
  payment_amount:
    PROMPT: "How much do you want to pay in dollars?"
    TYPE: number
    REQUIRED: true

COMPLETE:
  - WHEN: payment_amount IS SET AND payment_amount > 1000
    RESPOND: "Your payment of {{payment_amount}} dollars needs review."
    MODEL_CONTEXT: "The customer was told the payment needs review."
    STORE: reviewed_payments
  - WHEN: payment_amount IS SET

An amount of 1500 matches the first condition. An amount of 200 matches the second. The second shows the MESSAGES text. Order the conditions from most specific to least specific. The first match wins.

Verification

Compile the project. Fix every error and warning on the COMPLETE: section.
Test the end. Send a valid answer to the minimal example, for example 120. The trace shows completion_check with the condition and a true result, then a complete decision.
Check the source. completion_check carries source, such as post_turn_eval, flow_transition, or terminal_step. It tells you which checkpoint ended the agent.
Check the session end. Send a second message. The reply is the conversation-complete message and no agent runs.
Test a child. Complete Customer_Lookup_Agent. The trace shows handoff_return_handler with mappedFields. The next reply comes from the supervisor.
Test a withheld completion. Fail the constraint. The trace shows a decision completion_withheld_by_constraint.
Test a non-terminal completion. The reply shows and the next message routes as a new request.
Read traces with How to debug routing decisions in traces.

Production readiness checklist

Every WHEN reads state that something writes. Name the writer for each variable.
Every WHEN is deterministic. The compiler rejects plain-English text.
The closing text lives in one place: the step RESPOND or the completion RESPOND.
Every RETURN: true child has a COMPLETE condition or a flow THEN: COMPLETE. Otherwise the supervisor waits.
Every RETURN: false specialist has a planned end: COMPLETE, a HANDOFF back, or an escalation.
Every TERMINAL: false completion clears its own condition with SET.
The MESSAGES conversation_complete text tells the customer how to start again.
Test a customer who sends a message after the session ends.
Test the first match when two conditions are both true.
Monitor sessions that never complete and children that never return.

Common mistakes

Mistake	Why it happens	How to avoid it
Writing a plain-English `WHEN`	The text reads like a goal.	Write a boolean expression over session state.
Ending an entry step with `RESPOND` and `THEN: COMPLETE`	The step looks like a question.	Use `GATHER` so the step waits for the customer.
Leaving a `COMPLETE` condition with no `RESPOND` on a root agent	The author expects silence.	Write the closing text. Without it, the default message shows.
Expecting `COMPLETE` in a `RETURN: false` specialist to return to the supervisor	The name suggests a return.	Use a `HANDOFF` to the supervisor. `COMPLETE` ends the session.
Putting a closing message in the step and a different one in `COMPLETE`	Both are valid.	Choose one place.
Writing `SET:` as a block under a completion	The block looks like YAML.	Write `SET: name = value` on one line.
Using `TERMINAL: false` without clearing the condition	The condition stays true.	Add `SET` that changes it.
Expecting a trivially true condition to end a flow before the next step runs	The condition looks like a gate.	Know that forward steps run first. End the flow with `THEN: COMPLETE`.
Expecting completion while a constraint fails	The condition is true.	Fix the constraint state. The runtime holds the completion.

Troubleshooting

Symptom	Likely cause	What to check
The agent never completes	The `WHEN` is false, or nothing writes the variable.	`completion_check` results and the source of each variable.
The agent completes on the first turn	The condition is true at start, for example `x IS NOT SET`.	The condition and the starting state.
The customer sees `This conversation has been completed.`	A condition has no `RESPOND`, or the session already ended.	The `RESPOND` line and the session state.
The model text vanished from the reply	A completion matched after the turn and replaced it.	Move the full text into `RESPOND`.
The supervisor never resumes after a child	The child has no completion, or `ON_RETURN` maps a missing field.	The child `COMPLETE` and the `handoff_return_handler` `mappedFields`.
Compile error `PLAIN_ENGLISH_COMPLETE_WHEN`	The `WHEN` is free text.	Replace it with a boolean expression.
Warning W360 on a completion	The `SET:` block or another property is ignored.	Use one-line `SET`, and only `RESPOND`, `SET`, `STORE`, `TERMINAL`, `MODEL_CONTEXT`, and response payload blocks.
A closing widget repeats on every turn	`TERMINAL: false` with a condition that stays true.	Add a `SET` that clears the condition.
The agent does not end although the condition is true	A constraint fails on the same state.	Decision `completion_withheld_by_constraint` and the constraint `ON_FAIL`.
A route takes over at the end of the flow	A `HANDOFF` condition matched at `THEN: COMPLETE`.	`HANDOFF` `WHEN` conditions and the trace source `flow_transition`.

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References

How to end a conversation with COMPLETE

Concept

Ways to complete

Completion conditions

What the runtime does on COMPLETE

Minimal working example

How it works

Common variations

End from a flow step

Return a child to its supervisor

Show a closing message without ending the session

Hold a completion until a rule passes

Store a snapshot, keep model context, and set the default message

Verification

Production readiness checklist

Common mistakes

Troubleshooting

​Concept

​Ways to complete

​Completion conditions

​What the runtime does on COMPLETE

​Minimal working example

​How it works

​Common variations

​End from a flow step

​Return a child to its supervisor

​Show a closing message without ending the session

​Hold a completion until a rule passes

​Store a snapshot, keep model context, and set the default message

​Verification

​Production readiness checklist

​Common mistakes

​Troubleshooting

Concept

Ways to complete

Completion conditions

What the runtime does on COMPLETE

Minimal working example

How it works

Common variations

End from a flow step

Return a child to its supervisor

Show a closing message without ending the session

Hold a completion until a rule passes

Store a snapshot, keep model context, and set the default message

Verification

Production readiness checklist

Common mistakes

Troubleshooting