Start a session

⚠️

Preview — this feature is being built; the design below is the spec.

POST https://app.syntic.ai/v1/sessions

Start a conversation with an agent. Pass the first message in input to save a round trip; the agent begins working at once and the session is running. Follow progress with Stream session events.

For how this fits into a full workflow, see Sessions.

Headers

Header	Required	Value
`Authorization`	Yes	`Bearer <key>`: a private inference key (`sk_live_...`). See Authentication.
`syntic-beta`	Yes, while in preview	`agents-2026-11-01`. Without it the call fails with `400 beta_required`. See Versioning.
`Content-Type`	Yes	`application/json`
`Idempotency-Key`	No	Up to 255 characters. Retrying with the same key within 24 hours returns the first result instead of creating a duplicate. See Idempotency.

Body parameters

Parameter	Type	Required	Notes
`agent_id`	string	Yes	An active agent.
`agent_version`	integer	No	Pin a version; default latest.
`input`	array	No	Events to send immediately, in the Send events format.
`title`	string	No	Shown in the Console, up to 200 characters.
`contact`	object	No	`{id, display_name}` for your own tracking.
`environment_id`	string	No	Override the agent’s environment.
`memory_scope`	string	No	Scope this session reads and writes in the agent’s memory stores, such as `customer:4821`. Without it only `global` is readable and nothing is written.
`limits`	object	No	Lower `max_turns`, `session_token_budget` or `session_cost_budget_usd`. Higher values than the agent’s are refused.
`metadata`	object	No	Up to 16 string pairs.

Response

201 Created, Content-Type: application/json

{
  "id": "sesn_01JC7M2K4P6R8T0V2X4Z",
  "type": "session",
  "agent_id": "agt_01JC4R8W6Q2N9X3T5V7Y",
  "agent_version": 4,
  "status": "running",
  "channel": "api",
  "title": "Refund for order 88123",
  "usage": {
    "input_tokens": 0,
    "cached_input_tokens": 0,
    "output_tokens": 0,
    "cost_usd": "0.0000"
  },
  "outcome": null,
  "created_at": "2026-11-05T10:00:00Z",
  "last_event_at": "2026-11-05T10:00:00Z",
  "metadata": {}
}

Field	Type	Description
`id`	string	Starts with `sesn_`.
`agent_id`	string	The agent the session runs.
`agent_version`	integer	The version it is pinned to for its whole life.
`status`	string	`running`, `requires_action` (waiting for your tool result or approval), `idle` or `archived`.
`channel`	string	`api` for sessions started here; channel sessions show `telegram`, `slack` and so on.
`usage`	object	Running token and cost totals.
`outcome`	object or null	Set when a turn ends: `reason` is `end_turn`, `max_turns`, `budget_exhausted`, `interrupted` or `error`.
`last_event_at`	string	Time of the latest event.

Examples

curl -sS https://app.syntic.ai/v1/sessions \
  -H "Authorization: Bearer $SYNTIC_API_KEY" \
  -H "syntic-beta: agents-2026-11-01" \
  -H "Idempotency-Key: 8d6f0c1e-4b2a-4a57-9f0e-2f1d3c4b5a69" \
  -H "Content-Type: application/json" \
  -d '{
      "agent_id": "agt_01JC4R8W6Q2N9X3T5V7Y",
      "title": "Refund for order 88123",
      "memory_scope": "customer:4821",
      "input": [
        {
          "type": "user.message",
          "content": "Please refund order 88123."
        }
      ]
    }'

import os
 
import requests
 
resp = requests.post(
    "https://app.syntic.ai/v1/sessions",
    headers={
        "Authorization": f"Bearer {os.environ['SYNTIC_API_KEY']}",
        "syntic-beta": "agents-2026-11-01",
        "Idempotency-Key": "8d6f0c1e-4b2a-4a57-9f0e-2f1d3c4b5a69",
    },
    json={
        "agent_id": "agt_01JC4R8W6Q2N9X3T5V7Y",
        "title": "Refund for order 88123",
        "memory_scope": "customer:4821",
        "input": [
            {
                "type": "user.message",
                "content": "Please refund order 88123.",
            },
        ],
    },
    timeout=60,
)
data = resp.json()
if not resp.ok:
    raise RuntimeError(f"{resp.status_code} {data['error']['code']}: {data['error']['message']}")
print(data)

const res = await fetch('https://app.syntic.ai/v1/sessions', {
  method: 'POST',
  headers: {
    Authorization: `Bearer ${process.env.SYNTIC_API_KEY}`,
    'syntic-beta': 'agents-2026-11-01',
    'Idempotency-Key': '8d6f0c1e-4b2a-4a57-9f0e-2f1d3c4b5a69',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    "agent_id": "agt_01JC4R8W6Q2N9X3T5V7Y",
    "title": "Refund for order 88123",
    "memory_scope": "customer:4821",
    "input": [
      {
        "type": "user.message",
        "content": "Please refund order 88123."
      }
    ]
  }),
})
const data = await res.json()
if (!res.ok) throw new Error(`${res.status} ${data.error.code}: ${data.error.message}`)
console.log(data)

package main
 
import (
	"fmt"
	"io"
	"net/http"
	"os"
	"strings"
)
 
func main() {
	body := strings.NewReader(`{
  "agent_id": "agt_01JC4R8W6Q2N9X3T5V7Y",
  "title": "Refund for order 88123",
  "memory_scope": "customer:4821",
  "input": [
    {
      "type": "user.message",
      "content": "Please refund order 88123."
    }
  ]
}`)
	req, err := http.NewRequest("POST", "https://app.syntic.ai/v1/sessions", body)
	if err != nil {
		panic(err)
	}
	req.Header.Set("Authorization", "Bearer "+os.Getenv("SYNTIC_API_KEY"))
	req.Header.Set("syntic-beta", "agents-2026-11-01")
	req.Header.Set("Idempotency-Key", "8d6f0c1e-4b2a-4a57-9f0e-2f1d3c4b5a69")
	req.Header.Set("Content-Type", "application/json")
 
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer resp.Body.Close()
 
	out, _ := io.ReadAll(resp.Body)
	if resp.StatusCode >= 300 {
		panic(fmt.Sprintf("%d: %s", resp.StatusCode, out))
	}
	fmt.Println(string(out))
}

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
 
public class Example {
    public static void main(String[] args) throws Exception {
        String body = """
            {
              "agent_id": "agt_01JC4R8W6Q2N9X3T5V7Y",
              "title": "Refund for order 88123",
              "memory_scope": "customer:4821",
              "input": [
                {
                  "type": "user.message",
                  "content": "Please refund order 88123."
                }
              ]
            }
            """;
        HttpRequest request = HttpRequest.newBuilder(URI.create("https://app.syntic.ai/v1/sessions"))
            .header("Authorization", "Bearer " + System.getenv("SYNTIC_API_KEY"))
            .header("syntic-beta", "agents-2026-11-01")
            .header("Idempotency-Key", "8d6f0c1e-4b2a-4a57-9f0e-2f1d3c4b5a69")
            .header("Content-Type", "application/json")
            .method("POST", HttpRequest.BodyPublishers.ofString(body))
            .build();
        HttpResponse<String> response = HttpClient.newHttpClient()
            .send(request, HttpResponse.BodyHandlers.ofString());
        if (response.statusCode() >= 300) {
            throw new RuntimeException(response.statusCode() + ": " + response.body());
        }
        System.out.println(response.body());
    }
}

using System.Net.Http.Headers;
using System.Text;
 
using var http = new HttpClient();
using var request = new HttpRequestMessage(new HttpMethod("POST"), "https://app.syntic.ai/v1/sessions");
request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", Environment.GetEnvironmentVariable("SYNTIC_API_KEY"));
request.Headers.Add("syntic-beta", "agents-2026-11-01");
request.Headers.Add("Idempotency-Key", "8d6f0c1e-4b2a-4a57-9f0e-2f1d3c4b5a69");
request.Content = new StringContent("""
    {
      "agent_id": "agt_01JC4R8W6Q2N9X3T5V7Y",
      "title": "Refund for order 88123",
      "memory_scope": "customer:4821",
      "input": [
        {
          "type": "user.message",
          "content": "Please refund order 88123."
        }
      ]
    }
    """, Encoding.UTF8, "application/json");
 
using var response = await http.SendAsync(request);
var text = await response.Content.ReadAsStringAsync();
if (!response.IsSuccessStatusCode) throw new Exception($"{(int)response.StatusCode}: {text}");
Console.WriteLine(text);

<?php
$body = <<<'JSON'
{
  "agent_id": "agt_01JC4R8W6Q2N9X3T5V7Y",
  "title": "Refund for order 88123",
  "memory_scope": "customer:4821",
  "input": [
    {
      "type": "user.message",
      "content": "Please refund order 88123."
    }
  ]
}
JSON;
 
$ch = curl_init('https://app.syntic.ai/v1/sessions');
curl_setopt_array($ch, [
    CURLOPT_CUSTOMREQUEST => 'POST',
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => [
        'Authorization: Bearer ' . getenv('SYNTIC_API_KEY'),
        'syntic-beta: agents-2026-11-01',
        'Idempotency-Key: 8d6f0c1e-4b2a-4a57-9f0e-2f1d3c4b5a69',
        'Content-Type: application/json',
    ],
    CURLOPT_POSTFIELDS => $body,
]);
$response = curl_exec($ch);
$status = curl_getinfo($ch, CURLINFO_RESPONSE_CODE);
curl_close($ch);
 
if ($status >= 300) {
    throw new RuntimeException("$status: $response");
}
print_r(json_decode($response, true));

require "json"
require "net/http"
require "uri"
 
uri = URI("https://app.syntic.ai/v1/sessions")
req = Net::HTTP::Post.new(uri)
req["Authorization"] = "Bearer #{ENV.fetch('SYNTIC_API_KEY')}"
req["syntic-beta"] = "agents-2026-11-01"
req["Idempotency-Key"] = "8d6f0c1e-4b2a-4a57-9f0e-2f1d3c4b5a69"
req["Content-Type"] = "application/json"
req.body = <<~'JSON'
  {
    "agent_id": "agt_01JC4R8W6Q2N9X3T5V7Y",
    "title": "Refund for order 88123",
    "memory_scope": "customer:4821",
    "input": [
      {
        "type": "user.message",
        "content": "Please refund order 88123."
      }
    ]
  }
JSON
 
res = Net::HTTP.start(uri.host, uri.port, use_ssl: true) { |http| http.request(req) }
raise "#{res.code}: #{res.body}" unless res.is_a?(Net::HTTPSuccess)
puts JSON.pretty_generate(JSON.parse(res.body))

Errors

Errors use the error envelope and carry a request_id. Codes specific to this operation:

Status	`type`	`code`	When
400	`invalid_request_error`	`beta_required`	The `syntic-beta` header is missing.
400	`invalid_request_error`	`limit_above_agent`	A session limit exceeds the agent’s.
402	`quota_exhausted`	`quota_exhausted`	Plan allowance and credits cannot cover the first model call.
404	`not_found_error`	`agent_not_found`	No such agent in this workspace.
409	`conflict_error`	`agent_archived`	The agent is archived.
409	`conflict_error`	`environment_not_ready`	The environment has not finished its first build.
401	`authentication_error`	`invalid_api_key`	The key is missing, unknown, revoked or expired.
429	`rate_limit_error`	`rate_limited`	Too many requests; wait for `Retry-After`. See Rate-limit headers.

Delete an agent List sessions

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