POST/v2/agents/sessions/{session_id}/checkpoints

CreateCheckpoint captures the session's live sandbox state as a durable checkpoint.

Synchronous: blocks until the capture reaches READY and returns the terminal Checkpoint — clients never see PENDING on this endpoint and need no poll loop. The checkpoint binds the machine-state capture to the event-log cursor at the cut, so it can later seed forks (POST .../fork) and rollback. Checkpoints are taken between turns; a session with an active turn in flight returns 409.

  • IdempotentThe SDK sends Idempotency-Key, so a retried request is only applied once.

1 parameter · 1 body field
session_idstringrequired
The session UUID.

Optional; an empty or omitted body creates an unlabeled checkpoint.

labelstringoptional
Optional human-readable label stored on the checkpoint; "" if omitted.

11 status codes
200Checkpoint captured. The returned checkpoint is terminal (status READY).
checkpointobjectoptional
Checkpoint is a durable capture of a session's live sandbox machine state bound to the event-log cursor at the cut. READY checkpoints seed forks (ForkSession) and rollback. Internal fields (team_id, the substrate checkpoint id, event_seq) are never serialized.
401Authentication failed due to invalid credentials.
idstringrequired
A short identifier corresponding to the HTTP status code returned. For example, the ID for a response returning a 404 status code would be "not_found."
messagestringrequired
A message providing additional information about the error, including details to help resolve it when possible.
request_idstringoptional
Optionally, some endpoints may include a request ID that should be provided when reporting bugs or opening support tickets to help identify the issue.
402The team is blocked by the prepayment gate.
idstringrequired
A short identifier corresponding to the HTTP status code returned. For example, the ID for a response returning a 404 status code would be "not_found."
messagestringrequired
A message providing additional information about the error, including details to help resolve it when possible.
request_idstringoptional
Optionally, some endpoints may include a request ID that should be provided when reporting bugs or opening support tickets to help identify the issue.
403Session belongs to another team.
idstringrequired
A short identifier corresponding to the HTTP status code returned. For example, the ID for a response returning a 404 status code would be "not_found."
messagestringrequired
A message providing additional information about the error, including details to help resolve it when possible.
request_idstringoptional
Optionally, some endpoints may include a request ID that should be provided when reporting bugs or opening support tickets to help identify the issue.
404The resource was not found.
idstringrequired
A short identifier corresponding to the HTTP status code returned. For example, the ID for a response returning a 404 status code would be "not_found."
messagestringrequired
A message providing additional information about the error, including details to help resolve it when possible.
request_idstringoptional
Optionally, some endpoints may include a request ID that should be provided when reporting bugs or opening support tickets to help identify the issue.
409Session busy (an active turn is in flight), session not running, or team checkpoint storage quota exceeded.
idstringrequired
A short identifier corresponding to the HTTP status code returned. For example, the ID for a response returning a 404 status code would be "not_found."
messagestringrequired
A message providing additional information about the error, including details to help resolve it when possible.
request_idstringoptional
Optionally, some endpoints may include a request ID that should be provided when reporting bugs or opening support tickets to help identify the issue.
423This session is unavailable; contact support.
idstringrequired
A short identifier corresponding to the HTTP status code returned. For example, the ID for a response returning a 404 status code would be "not_found."
messagestringrequired
A message providing additional information about the error, including details to help resolve it when possible.
request_idstringoptional
Optionally, some endpoints may include a request ID that should be provided when reporting bugs or opening support tickets to help identify the issue.
429The API rate limit has been exceeded.
idstringrequired
A short identifier corresponding to the HTTP status code returned. For example, the ID for a response returning a 404 status code would be "not_found."
messagestringrequired
A message providing additional information about the error, including details to help resolve it when possible.
request_idstringoptional
Optionally, some endpoints may include a request ID that should be provided when reporting bugs or opening support tickets to help identify the issue.
500There was a server error.
idstringrequired
A short identifier corresponding to the HTTP status code returned. For example, the ID for a response returning a 404 status code would be "not_found."
messagestringrequired
A message providing additional information about the error, including details to help resolve it when possible.
request_idstringoptional
Optionally, some endpoints may include a request ID that should be provided when reporting bugs or opening support tickets to help identify the issue.
501Checkpoints are not supported for this agent/substrate.
idstringrequired
A short identifier corresponding to the HTTP status code returned. For example, the ID for a response returning a 404 status code would be "not_found."
messagestringrequired
A message providing additional information about the error, including details to help resolve it when possible.
request_idstringoptional
Optionally, some endpoints may include a request ID that should be provided when reporting bugs or opening support tickets to help identify the issue.
defaultThere was an unexpected error.
idstringrequired
A short identifier corresponding to the HTTP status code returned. For example, the ID for a response returning a 404 status code would be "not_found."
messagestringrequired
A message providing additional information about the error, including details to help resolve it when possible.
request_idstringoptional
Optionally, some endpoints may include a request ID that should be provided when reporting bugs or opening support tickets to help identify the issue.

Error handling

A 401 is returned: Authentication failed due to invalid credentials. A 402 is returned: The team is blocked by the prepayment gate. A 403 is returned: Session belongs to another team. A 404 is returned: The resource was not found. A 409 is returned: Session busy (an active turn is in flight), session not running, or team checkpoint storage quota exceeded. A 423 is returned: This session is unavailable; contact support. A 429 is returned: The API rate limit has been exceeded. A 500 is returned: There was a server error. A 501 is returned: Checkpoints are not supported for this agent/substrate. Any other status is an error: There was an unexpected error.