API · Create · Sessions
Expire the formation session.
Programmatically retire a formation session before it reaches active. Use it to take back control of a flow that's gone stale — a founder who started a formation, abandoned the tab, and the platform now wants to start fresh.
On expiry: status moves to expired and the session is closed. The underlying entity and any originating Intent survive — they aren't cancelled, just disconnected from this session — so a new session can be started against the same entity if you want to resume. Emits formation_session.expired.
Returns 200 OK. No-op on a session that is already expired — it returns 200 OK unchanged. A session that already reached active (formation completed) returns 409 state_transition_invalid; a completed session is not expirable. Idempotent.
See also: Sessions API overview.
Last updated
Response Body
application/json
application/problem+json
application/problem+json
Request
curl -X POST "https://api.mattermode.com/v1/formation_sessions/{id}/expire"fetch("https://api.mattermode.com/v1/formation_sessions/{id}/expire", { method: "POST"})package mainimport ( "fmt" "net/http" "io/ioutil")func main() { url := "https://api.mattermode.com/v1/formation_sessions/{id}/expire" req, _ := http.NewRequest("POST", url, nil) res, _ := http.DefaultClient.Do(req) defer res.Body.Close() body, _ := ioutil.ReadAll(res.Body) fmt.Println(res) fmt.Println(string(body))}import requestsheaders = { "Authorization": "Bearer sk_test_4eC39HqLyjWDarjtT1zdp7dc", "Matter-Version": "2026-06-10", "Idempotency-Key": "ee7c3a9b-3f1a-4d8e-9b2a-7c5e1f0a2d4b",}resp = requests.post( "https://api.mattermode.com/v1/formation_sessions/id_placeholder/expire", headers=headers,)resp.raise_for_status()print(resp.json())import java.net.URI;import java.net.http.HttpClient;import java.net.http.HttpRequest;import java.net.http.HttpResponse;import java.net.http.HttpResponse.BodyHandlers;import java.time.Duration;HttpClient client = HttpClient.newBuilder() .connectTimeout(Duration.ofSeconds(10)) .build();HttpRequest.Builder requestBuilder = HttpRequest.newBuilder() .uri(URI.create("https://api.mattermode.com/v1/formation_sessions/{id}/expire")) .POST() .build();try { HttpResponse<String> response = client.send(requestBuilder.build(), BodyHandlers.ofString()); System.out.println("Status code: " + response.statusCode()); System.out.println("Response body: " + response.body());} catch (Exception e) { e.printStackTrace();}using System;using System.Net.Http;using System.Text;var client = new HttpClient();var response = await client.PostAsync("https://api.mattermode.com/v1/formation_sessions/{id}/expire");var responseBody = await response.Content.ReadAsStringAsync();curl --request POST 'https://api.mattermode.com/v1/formation_sessions/id_placeholder/expire' \ --header 'Authorization: Bearer sk_test_4eC39HqLyjWDarjtT1zdp7dc' \ --header 'Matter-Version: 2026-06-10' \ --header 'Idempotency-Key: ee7c3a9b-3f1a-4d8e-9b2a-7c5e1f0a2d4b'const response = await fetch("https://api.mattermode.com/v1/formation_sessions/id_placeholder/expire", { method: "POST", headers: { "Authorization": "Bearer sk_test_4eC39HqLyjWDarjtT1zdp7dc", "Matter-Version": "2026-06-10", "Idempotency-Key": "ee7c3a9b-3f1a-4d8e-9b2a-7c5e1f0a2d4b", },});if (!response.ok) { throw new Error(`Matter API ${response.status}: ${await response.text()}`);}const data = await response.json();console.log(data);Response
application/json{
"id": "fss_b3nkpl5x9q2w7r4t",
"object": "formation_session",
"entity_id": "ent_Nq3KcAbc",
"intent_id": "itt_3sR8wPbX",
"mode": "test",
"status": "expired",
"current_step": "intent",
"progress": {},
"started_at": "2026-06-08T12:00:00.000Z",
"completed_at": null,
"version": 1,
"created_at": "2026-06-08T12:00:00.000Z",
"updated_at": "2026-06-08T12:05:00.000Z"
}{
"type": "https://mattermode.com/docs/errors/not_found",
"title": "Not found",
"status": 404,
"code": "not_found",
"detail": "No entity with id `ent_Nq3KcAbc` is visible to this token.",
"doc_url": "https://mattermode.com/docs/guides/errors#not_found",
"request_id": "req_Qw9xYz8A"
}{
"type": "https://mattermode.com/docs/errors/invalid_state_transition",
"title": "Invalid state transition",
"status": 409,
"code": "invalid_state_transition",
"detail": "Entity ent_Nq3KcAbc is in state `dissolved`; `dissolve` is not a valid transition.",
"doc_url": "https://mattermode.com/docs/guides/errors#invalid_state_transition",
"request_id": "req_Qw9xYz8A",
"current_state": "dissolved",
"attempted_transition": "dissolve",
"allowed_transitions": []
}{
"type": "https://mattermode.com/docs/errors/dissolution_prerequisites_missing",
"title": "Dissolution prerequisites missing",
"status": 409,
"code": "dissolution_prerequisites_missing",
"detail": "Voluntary dissolution requires `board_resolution_id` and `stockholder_consent_id`, or `auto_generate_resolutions: true`.",
"doc_url": "https://mattermode.com/docs/guides/errors#dissolution_prerequisites_missing",
"request_id": "req_Qw9xYz8A"
}{
"type": "https://mattermode.com/docs/errors/valuation_stale",
"title": "409A valuation stale",
"status": 409,
"code": "valuation_stale",
"detail": "Active 409A val_AbCd1234 is older than 12 months or superseded by a material event. Issuing ISOs at the prior strike risks IRC §409A violation. Refresh via POST /entities/{id}/valuations/{id}/refresh_request.",
"doc_url": "https://mattermode.com/docs/guides/errors#valuation_stale",
"request_id": "req_Qw9xYz8A"
}