Request a SessionThread harness handoff
curl --request POST \
--url https://api.checkfu.com/v1/sessions/{id}/handoffs \
--header 'Authorization: Bearer <token>' \
--header 'Content-Type: application/json' \
--header 'checkfu-version: <checkfu-version>' \
--header 'idempotency-key: <idempotency-key>' \
--data '
{
"session_thread_id": "<string>",
"target_has_handoff_import": true,
"capsule_compatible": true,
"apply": true,
"agent_context_digest": "<string>",
"source_tool_digest": "<string>",
"target_tool_digest": "<string>",
"source_resource_digest": "<string>",
"target_resource_digest": "<string>",
"source_filesystem_digest": "<string>",
"target_filesystem_digest": "<string>",
"target_agent": "<string>",
"target_environment_id": "<string>"
}
'import requests
url = "https://api.checkfu.com/v1/sessions/{id}/handoffs"
payload = {
"session_thread_id": "<string>",
"target_has_handoff_import": True,
"capsule_compatible": True,
"apply": True,
"agent_context_digest": "<string>",
"source_tool_digest": "<string>",
"target_tool_digest": "<string>",
"source_resource_digest": "<string>",
"target_resource_digest": "<string>",
"source_filesystem_digest": "<string>",
"target_filesystem_digest": "<string>",
"target_agent": "<string>",
"target_environment_id": "<string>"
}
headers = {
"checkfu-version": "<checkfu-version>",
"idempotency-key": "<idempotency-key>",
"Authorization": "Bearer <token>",
"Content-Type": "application/json"
}
response = requests.post(url, json=payload, headers=headers)
print(response.text)const options = {
method: 'POST',
headers: {
'checkfu-version': '<checkfu-version>',
'idempotency-key': '<idempotency-key>',
Authorization: 'Bearer <token>',
'Content-Type': 'application/json'
},
body: JSON.stringify({
session_thread_id: '<string>',
target_has_handoff_import: true,
capsule_compatible: true,
apply: true,
agent_context_digest: '<string>',
source_tool_digest: '<string>',
target_tool_digest: '<string>',
source_resource_digest: '<string>',
target_resource_digest: '<string>',
source_filesystem_digest: '<string>',
target_filesystem_digest: '<string>',
target_agent: '<string>',
target_environment_id: '<string>'
})
};
fetch('https://api.checkfu.com/v1/sessions/{id}/handoffs', options)
.then(res => res.json())
.then(res => console.log(res))
.catch(err => console.error(err));<?php
$curl = curl_init();
curl_setopt_array($curl, [
CURLOPT_URL => "https://api.checkfu.com/v1/sessions/{id}/handoffs",
CURLOPT_RETURNTRANSFER => true,
CURLOPT_ENCODING => "",
CURLOPT_MAXREDIRS => 10,
CURLOPT_TIMEOUT => 30,
CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
CURLOPT_CUSTOMREQUEST => "POST",
CURLOPT_POSTFIELDS => json_encode([
'session_thread_id' => '<string>',
'target_has_handoff_import' => true,
'capsule_compatible' => true,
'apply' => true,
'agent_context_digest' => '<string>',
'source_tool_digest' => '<string>',
'target_tool_digest' => '<string>',
'source_resource_digest' => '<string>',
'target_resource_digest' => '<string>',
'source_filesystem_digest' => '<string>',
'target_filesystem_digest' => '<string>',
'target_agent' => '<string>',
'target_environment_id' => '<string>'
]),
CURLOPT_HTTPHEADER => [
"Authorization: Bearer <token>",
"Content-Type: application/json",
"checkfu-version: <checkfu-version>",
"idempotency-key: <idempotency-key>"
],
]);
$response = curl_exec($curl);
$err = curl_error($curl);
curl_close($curl);
if ($err) {
echo "cURL Error #:" . $err;
} else {
echo $response;
}package main
import (
"fmt"
"strings"
"net/http"
"io"
)
func main() {
url := "https://api.checkfu.com/v1/sessions/{id}/handoffs"
payload := strings.NewReader("{\n \"session_thread_id\": \"<string>\",\n \"target_has_handoff_import\": true,\n \"capsule_compatible\": true,\n \"apply\": true,\n \"agent_context_digest\": \"<string>\",\n \"source_tool_digest\": \"<string>\",\n \"target_tool_digest\": \"<string>\",\n \"source_resource_digest\": \"<string>\",\n \"target_resource_digest\": \"<string>\",\n \"source_filesystem_digest\": \"<string>\",\n \"target_filesystem_digest\": \"<string>\",\n \"target_agent\": \"<string>\",\n \"target_environment_id\": \"<string>\"\n}")
req, _ := http.NewRequest("POST", url, payload)
req.Header.Add("checkfu-version", "<checkfu-version>")
req.Header.Add("idempotency-key", "<idempotency-key>")
req.Header.Add("Authorization", "Bearer <token>")
req.Header.Add("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)
defer res.Body.Close()
body, _ := io.ReadAll(res.Body)
fmt.Println(string(body))
}HttpResponse<String> response = Unirest.post("https://api.checkfu.com/v1/sessions/{id}/handoffs")
.header("checkfu-version", "<checkfu-version>")
.header("idempotency-key", "<idempotency-key>")
.header("Authorization", "Bearer <token>")
.header("Content-Type", "application/json")
.body("{\n \"session_thread_id\": \"<string>\",\n \"target_has_handoff_import\": true,\n \"capsule_compatible\": true,\n \"apply\": true,\n \"agent_context_digest\": \"<string>\",\n \"source_tool_digest\": \"<string>\",\n \"target_tool_digest\": \"<string>\",\n \"source_resource_digest\": \"<string>\",\n \"target_resource_digest\": \"<string>\",\n \"source_filesystem_digest\": \"<string>\",\n \"target_filesystem_digest\": \"<string>\",\n \"target_agent\": \"<string>\",\n \"target_environment_id\": \"<string>\"\n}")
.asString();require 'uri'
require 'net/http'
url = URI("https://api.checkfu.com/v1/sessions/{id}/handoffs")
http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true
request = Net::HTTP::Post.new(url)
request["checkfu-version"] = '<checkfu-version>'
request["idempotency-key"] = '<idempotency-key>'
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n \"session_thread_id\": \"<string>\",\n \"target_has_handoff_import\": true,\n \"capsule_compatible\": true,\n \"apply\": true,\n \"agent_context_digest\": \"<string>\",\n \"source_tool_digest\": \"<string>\",\n \"target_tool_digest\": \"<string>\",\n \"source_resource_digest\": \"<string>\",\n \"target_resource_digest\": \"<string>\",\n \"source_filesystem_digest\": \"<string>\",\n \"target_filesystem_digest\": \"<string>\",\n \"target_agent\": \"<string>\",\n \"target_environment_id\": \"<string>\"\n}"
response = http.request(request)
puts response.read_body{
"session_id": "<string>",
"session_thread_id": "<string>",
"frozen_sequence": 4503599627370495,
"preflight": {
"outcome": "refused",
"reason": "thread_not_idle"
},
"mutation": {
"mutation_type": "none",
"context_frontier_sequence": 4503599627370495
},
"snapshot_injection": "native_session_load",
"apply_status": "not_requested"
}{
"error": {
"type": "validation.malformed",
"message": "<string>",
"more": "https://docs.checkfu.com/reference/errors#validation-malformed"
}
}{
"error": {
"type": "auth.invalid_key",
"message": "<string>",
"more": "https://docs.checkfu.com/reference/errors#auth-invalid-key"
}
}{
"error": {
"type": "auth.disabled_tenancy",
"message": "<string>",
"more": "https://docs.checkfu.com/reference/errors#auth-disabled-tenancy"
}
}{
"error": {
"type": "validation.not_found",
"message": "<string>",
"more": "https://docs.checkfu.com/reference/errors#validation-not-found"
}
}{
"error": {
"type": "validation.conflict",
"message": "<string>",
"more": "https://docs.checkfu.com/reference/errors#validation-conflict"
}
}{
"error": {
"type": "budget.exceeded",
"message": "<string>",
"more": "https://docs.checkfu.com/reference/errors#budget-exceeded"
}
}{
"error": {
"type": "runtime.internal",
"message": "<string>",
"more": "https://docs.checkfu.com/reference/errors#runtime-internal"
}
}Request a SessionThread harness handoff
Inspects or requests an idle SessionThread harness handoff at the frozen context frontier. Inspection reports the requested continuity, target posture, and visible loss dimensions without mutation. An applied portable handoff additionally requires an exact target Agent selector, Environment, and currently signed handoff-import target; the server compiles and binds that target admission, advances the thread to one new root actor generation, and queues a context-rebuild Run. Failed or unqualified apply advances no context frontier. Native-exact launch remains unavailable here unless the target path separately supplies compatible capsule custody. Distinct from same-tuple idle continuation.
Checkfu support posture: alpha; hosted. Required evidence journey: session-turn. Deployment-specific readiness and the latest proven release are available from GET /v1/support/capabilities.
POST
/
v1
/
sessions
/
{id}
/
handoffs
Request a SessionThread harness handoff
curl --request POST \
--url https://api.checkfu.com/v1/sessions/{id}/handoffs \
--header 'Authorization: Bearer <token>' \
--header 'Content-Type: application/json' \
--header 'checkfu-version: <checkfu-version>' \
--header 'idempotency-key: <idempotency-key>' \
--data '
{
"session_thread_id": "<string>",
"target_has_handoff_import": true,
"capsule_compatible": true,
"apply": true,
"agent_context_digest": "<string>",
"source_tool_digest": "<string>",
"target_tool_digest": "<string>",
"source_resource_digest": "<string>",
"target_resource_digest": "<string>",
"source_filesystem_digest": "<string>",
"target_filesystem_digest": "<string>",
"target_agent": "<string>",
"target_environment_id": "<string>"
}
'import requests
url = "https://api.checkfu.com/v1/sessions/{id}/handoffs"
payload = {
"session_thread_id": "<string>",
"target_has_handoff_import": True,
"capsule_compatible": True,
"apply": True,
"agent_context_digest": "<string>",
"source_tool_digest": "<string>",
"target_tool_digest": "<string>",
"source_resource_digest": "<string>",
"target_resource_digest": "<string>",
"source_filesystem_digest": "<string>",
"target_filesystem_digest": "<string>",
"target_agent": "<string>",
"target_environment_id": "<string>"
}
headers = {
"checkfu-version": "<checkfu-version>",
"idempotency-key": "<idempotency-key>",
"Authorization": "Bearer <token>",
"Content-Type": "application/json"
}
response = requests.post(url, json=payload, headers=headers)
print(response.text)const options = {
method: 'POST',
headers: {
'checkfu-version': '<checkfu-version>',
'idempotency-key': '<idempotency-key>',
Authorization: 'Bearer <token>',
'Content-Type': 'application/json'
},
body: JSON.stringify({
session_thread_id: '<string>',
target_has_handoff_import: true,
capsule_compatible: true,
apply: true,
agent_context_digest: '<string>',
source_tool_digest: '<string>',
target_tool_digest: '<string>',
source_resource_digest: '<string>',
target_resource_digest: '<string>',
source_filesystem_digest: '<string>',
target_filesystem_digest: '<string>',
target_agent: '<string>',
target_environment_id: '<string>'
})
};
fetch('https://api.checkfu.com/v1/sessions/{id}/handoffs', options)
.then(res => res.json())
.then(res => console.log(res))
.catch(err => console.error(err));<?php
$curl = curl_init();
curl_setopt_array($curl, [
CURLOPT_URL => "https://api.checkfu.com/v1/sessions/{id}/handoffs",
CURLOPT_RETURNTRANSFER => true,
CURLOPT_ENCODING => "",
CURLOPT_MAXREDIRS => 10,
CURLOPT_TIMEOUT => 30,
CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
CURLOPT_CUSTOMREQUEST => "POST",
CURLOPT_POSTFIELDS => json_encode([
'session_thread_id' => '<string>',
'target_has_handoff_import' => true,
'capsule_compatible' => true,
'apply' => true,
'agent_context_digest' => '<string>',
'source_tool_digest' => '<string>',
'target_tool_digest' => '<string>',
'source_resource_digest' => '<string>',
'target_resource_digest' => '<string>',
'source_filesystem_digest' => '<string>',
'target_filesystem_digest' => '<string>',
'target_agent' => '<string>',
'target_environment_id' => '<string>'
]),
CURLOPT_HTTPHEADER => [
"Authorization: Bearer <token>",
"Content-Type: application/json",
"checkfu-version: <checkfu-version>",
"idempotency-key: <idempotency-key>"
],
]);
$response = curl_exec($curl);
$err = curl_error($curl);
curl_close($curl);
if ($err) {
echo "cURL Error #:" . $err;
} else {
echo $response;
}package main
import (
"fmt"
"strings"
"net/http"
"io"
)
func main() {
url := "https://api.checkfu.com/v1/sessions/{id}/handoffs"
payload := strings.NewReader("{\n \"session_thread_id\": \"<string>\",\n \"target_has_handoff_import\": true,\n \"capsule_compatible\": true,\n \"apply\": true,\n \"agent_context_digest\": \"<string>\",\n \"source_tool_digest\": \"<string>\",\n \"target_tool_digest\": \"<string>\",\n \"source_resource_digest\": \"<string>\",\n \"target_resource_digest\": \"<string>\",\n \"source_filesystem_digest\": \"<string>\",\n \"target_filesystem_digest\": \"<string>\",\n \"target_agent\": \"<string>\",\n \"target_environment_id\": \"<string>\"\n}")
req, _ := http.NewRequest("POST", url, payload)
req.Header.Add("checkfu-version", "<checkfu-version>")
req.Header.Add("idempotency-key", "<idempotency-key>")
req.Header.Add("Authorization", "Bearer <token>")
req.Header.Add("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)
defer res.Body.Close()
body, _ := io.ReadAll(res.Body)
fmt.Println(string(body))
}HttpResponse<String> response = Unirest.post("https://api.checkfu.com/v1/sessions/{id}/handoffs")
.header("checkfu-version", "<checkfu-version>")
.header("idempotency-key", "<idempotency-key>")
.header("Authorization", "Bearer <token>")
.header("Content-Type", "application/json")
.body("{\n \"session_thread_id\": \"<string>\",\n \"target_has_handoff_import\": true,\n \"capsule_compatible\": true,\n \"apply\": true,\n \"agent_context_digest\": \"<string>\",\n \"source_tool_digest\": \"<string>\",\n \"target_tool_digest\": \"<string>\",\n \"source_resource_digest\": \"<string>\",\n \"target_resource_digest\": \"<string>\",\n \"source_filesystem_digest\": \"<string>\",\n \"target_filesystem_digest\": \"<string>\",\n \"target_agent\": \"<string>\",\n \"target_environment_id\": \"<string>\"\n}")
.asString();require 'uri'
require 'net/http'
url = URI("https://api.checkfu.com/v1/sessions/{id}/handoffs")
http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true
request = Net::HTTP::Post.new(url)
request["checkfu-version"] = '<checkfu-version>'
request["idempotency-key"] = '<idempotency-key>'
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n \"session_thread_id\": \"<string>\",\n \"target_has_handoff_import\": true,\n \"capsule_compatible\": true,\n \"apply\": true,\n \"agent_context_digest\": \"<string>\",\n \"source_tool_digest\": \"<string>\",\n \"target_tool_digest\": \"<string>\",\n \"source_resource_digest\": \"<string>\",\n \"target_resource_digest\": \"<string>\",\n \"source_filesystem_digest\": \"<string>\",\n \"target_filesystem_digest\": \"<string>\",\n \"target_agent\": \"<string>\",\n \"target_environment_id\": \"<string>\"\n}"
response = http.request(request)
puts response.read_body{
"session_id": "<string>",
"session_thread_id": "<string>",
"frozen_sequence": 4503599627370495,
"preflight": {
"outcome": "refused",
"reason": "thread_not_idle"
},
"mutation": {
"mutation_type": "none",
"context_frontier_sequence": 4503599627370495
},
"snapshot_injection": "native_session_load",
"apply_status": "not_requested"
}{
"error": {
"type": "validation.malformed",
"message": "<string>",
"more": "https://docs.checkfu.com/reference/errors#validation-malformed"
}
}{
"error": {
"type": "auth.invalid_key",
"message": "<string>",
"more": "https://docs.checkfu.com/reference/errors#auth-invalid-key"
}
}{
"error": {
"type": "auth.disabled_tenancy",
"message": "<string>",
"more": "https://docs.checkfu.com/reference/errors#auth-disabled-tenancy"
}
}{
"error": {
"type": "validation.not_found",
"message": "<string>",
"more": "https://docs.checkfu.com/reference/errors#validation-not-found"
}
}{
"error": {
"type": "validation.conflict",
"message": "<string>",
"more": "https://docs.checkfu.com/reference/errors#validation-conflict"
}
}{
"error": {
"type": "budget.exceeded",
"message": "<string>",
"more": "https://docs.checkfu.com/reference/errors#budget-exceeded"
}
}{
"error": {
"type": "runtime.internal",
"message": "<string>",
"more": "https://docs.checkfu.com/reference/errors#runtime-internal"
}
}Authorizations
Bearer authentication header of the form Bearer <token>, where <token> is your auth token.
Headers
Available options:
2026-08-29 Required string length:
1 - 255Path Parameters
Pattern:
^sess_[0-9a-f]{32}$Body
application/json
Pattern:
^sthr_[0-9a-f]{32}$Available options:
native_compatible, portable_rebuild, transcript_only, not_resumable Available options:
semantic, native, filesystem Available options:
same_sandbox, checkpoint_clone, fresh_environment Available options:
acp, managed, connected Pattern:
^sha256:[0-9a-f]{64}$Pattern:
^sha256:[0-9a-f]{64}$Pattern:
^sha256:[0-9a-f]{64}$Pattern:
^sha256:[0-9a-f]{64}$Pattern:
^sha256:[0-9a-f]{64}$Pattern:
^sha256:[0-9a-f]{64}$Pattern:
^sha256:[0-9a-f]{64}$Pattern:
^agent_[0-9a-f]{32}$Pattern:
^env_[0-9a-f]{32}$Show child attributes
Show child attributes
Response
Success
Pattern:
^sess_[0-9a-f]{32}$Pattern:
^sthr_[0-9a-f]{32}$Required range:
0 <= x <= 9007199254740991- Option 1
- Option 2
Show child attributes
Show child attributes
- Option 1
- Option 2
Show child attributes
Show child attributes
Available options:
native_session_load, managed_native_restore, portable_snapshot_import Available options:
not_requested, preflight_refused, writer_unavailable, applied, writer_failed, target_unqualified