Chat API のはじめに

npm install @xdevplatform/chat-xdk @xdevplatform/xdk
npm install juicebox-sdk   # optional peer dependency — required for setup()/unlock() secure key backup

[dependencies]
# chat-xdk-core is not yet on crates.io — use the git dependency
chat-xdk-core = { git = "https://github.com/xdevplatform/chat-xdk" }  # pin a release tag in production, e.g. tag = "vX.Y.Z"
reqwest = { version = "0.12", features = ["blocking", "json"] }
serde_json = "1"
base64 = "0.22"

# Required until thrift 0.24 is released on crates.io
[patch.crates-io]
thrift = { git = "https://github.com/apache/thrift.git", rev = "deb36fa409849de45973b04ffc3ce49d277ca90a" }

go get github.com/xdevplatform/chat-xdk/go/chatxdk

dotnet add package XDevPlatform.ChatXdk

<dependency>
  <groupId>com.x</groupId>
  <artifactId>chatxdk</artifactId>
  <!-- Use the latest version from https://central.sonatype.com/artifact/com.x/chatxdk -->
  <version>x.y.z</version>
</dependency>

import { Client } from '@xdevplatform/xdk';

const client = new Client({ accessToken: 'YOUR_OAUTH2_USER_TOKEN' });

let access_token = std::env::var("X_ACCESS_TOKEN")?;
let http = reqwest::blocking::Client::new();
let auth = format!("Bearer {access_token}");

accessToken := os.Getenv("X_ACCESS_TOKEN")
httpClient := &http.Client{Timeout: 30 * time.Second}

using var http = new HttpClient();
http.DefaultRequestHeaders.Authorization =
    new System.Net.Http.Headers.AuthenticationHeaderValue(
        "Bearer", Environment.GetEnvironmentVariable("X_ACCESS_TOKEN"));

String accessToken = System.getenv("X_ACCESS_TOKEN");
HttpClient http = HttpClient.newHttpClient();

import { createChat } from '@xdevplatform/chat-xdk';

const resp = await client.chat.getUserPublicKeys('YOUR_USER_ID', {
  publicKeyFields: [
    'public_key_version', 'public_key', 'signing_public_key',
    'identity_public_key_signature', 'juicebox_config',
  ],
});
const record = resp.data[0];
const signingKeyVersion = String(record.public_key_version);

const chat = await createChat({
  juiceboxConfig: JSON.stringify(record.juicebox_config),
  getAuthToken: async (realmId) => getRealmTokenFromYourBackend(realmId),
});
await chat.unlock('YOUR_PASSCODE');
chat.setIdentity('YOUR_USER_ID', signingKeyVersion);

use base64::{engine::general_purpose::STANDARD as B64, Engine};
use chat_xdk_core::ChatCore;

let chat = ChatCore::new();
let blob = B64.decode(std::env::var("PRIVATE_KEYS_B64")?)?;
let signing_key_version = std::env::var("SIGNING_KEY_VERSION").unwrap_or_else(|_| "1".into());
chat.import_keys_with_version(&blob, &signing_key_version)?;
chat.set_identity("YOUR_USER_ID", &signing_key_version);

import "github.com/xdevplatform/chat-xdk/go/chatxdk"

chat := chatxdk.New()
defer chat.Close()

blob, err := chatxdk.Base64ToBytes(os.Getenv("PRIVATE_KEYS_B64"))
if err != nil {
    log.Fatal(err)
}
signingKeyVersion := os.Getenv("SIGNING_KEY_VERSION")
if signingKeyVersion == "" {
    signingKeyVersion = "1"
}
if err := chat.ImportKeysWithVersion(blob, signingKeyVersion); err != nil {
    log.Fatal(err)
}
if err := chat.SetIdentity(myUserID, signingKeyVersion); err != nil {
    log.Fatal(err)
}

using ChatXdk;

using var chat = new Chat();
var signingKeyVersion = Environment.GetEnvironmentVariable("SIGNING_KEY_VERSION") ?? "1";
chat.ImportKeys(Convert.FromBase64String(
    Environment.GetEnvironmentVariable("PRIVATE_KEYS_B64")!), signingKeyVersion);
chat.SetIdentity(myUserId, signingKeyVersion);

import com.x.chatxdk.Chat;

String signingKeyVersion = Optional.ofNullable(System.getenv("SIGNING_KEY_VERSION")).orElse("1");
try (Chat chat = new Chat()) {
    chat.importKeys(Base64.getDecoder().decode(System.getenv("PRIVATE_KEYS_B64")), signingKeyVersion);
    chat.setIdentity(myUserId, signingKeyVersion);
}

const registration = chat.generateKeypairs();
const pk = registration.publicKey;
await client.chat.addUserPublicKey('YOUR_USER_ID', {
  public_key: {
    identity_public_key_signature: pk.identityPublicKeySignature,
    public_key: pk.publicKey,
    public_key_fingerprint: pk.publicKeyFingerprint,
    registration_method: pk.registrationMethod,
    signing_public_key: pk.signingPublicKey,
    signing_public_key_signature: pk.signingPublicKeySignature,
  },
  version: registration.version,
  generate_version: registration.generateVersion,
});
await chat.setup('YOUR_PASSCODE');
chat.setIdentity('YOUR_USER_ID', String(registration.version ?? '1'));

let registration = chat.generate_keypairs()?;
let body = serde_json::to_value(&registration)?;
let resp = http
    .post(format!("https://api.x.com/2/users/{user_id}/public_keys"))
    .header("Authorization", &auth)
    .json(&body)
    .send()?;
if !resp.status().is_success() {
    anyhow::bail!("register keys: {}", resp.text()?);
}
let _blob = chat.export_keys()?; // store securely
let key_version = registration.version.clone().unwrap_or_else(|| "1".into());
chat.set_identity(&user_id, &key_version);

registration, err := chat.GenerateKeypairs()
if err != nil {
    log.Fatal(err)
}
regJSON, _ := json.Marshal(registration)
req, _ := http.NewRequest(http.MethodPost,
    "https://api.x.com/2/users/"+userID+"/public_keys",
    bytes.NewReader(regJSON))
req.Header.Set("Authorization", "Bearer "+accessToken)
req.Header.Set("Content-Type", "application/json")
resp, err := httpClient.Do(req)
if err != nil {
    log.Fatal(err)
}
resp.Body.Close()
privateKeys, _ := chat.ExportKeys() // store securely
_ = privateKeys
keyVersion := "1"
if registration.Version != nil {
    keyVersion = *registration.Version
}
if err := chat.SetIdentity(userID, keyVersion); err != nil {
    log.Fatal(err)
}

var registration = chat.GenerateKeypairs();
var regJson = System.Text.Json.JsonSerializer.Serialize(registration);
using var content = new StringContent(regJson, Encoding.UTF8, "application/json");
using var regResp = await http.PostAsync(
    $"https://api.x.com/2/users/{Uri.EscapeDataString(userId)}/public_keys", content);
regResp.EnsureSuccessStatusCode();
var blob = chat.ExportKeys(); // store securely
chat.SetIdentity(userId, registration.Version ?? "1");

var registration = chat.generateKeypairs();
String regJson = new ObjectMapper().writeValueAsString(registration);
HttpRequest req = HttpRequest.newBuilder()
    .uri(URI.create("https://api.x.com/2/users/" + userId + "/public_keys"))
    .header("Authorization", "Bearer " + accessToken)
    .header("Content-Type", "application/json")
    .POST(HttpRequest.BodyPublishers.ofString(regJson))
    .build();
HttpResponse<String> regResp = http.send(req, HttpResponse.BodyHandlers.ofString());
if (regResp.statusCode() >= 300) {
    throw new RuntimeException("register keys: " + regResp.body());
}
byte[] blob = chat.exportKeys(); // store securely
chat.setIdentity(myUserId, registration.version != null ? registration.version : "1");

async function publicKeyInput(userId: string) {
  const r = (await client.chat.getUserPublicKeys(userId, {
    publicKeyFields: ['public_key_version', 'public_key'],
  })).data[0];
  return { userId, publicKey: r.public_key, keyVersion: r.public_key_version };
}

// Omit conversationId for a new 1:1; pass the id to rotate later
const prepared = chat.prepareConversationKeyChange({
  publicKeys: [
    await publicKeyInput('YOUR_USER_ID'),
    await publicKeyInput('RECIPIENT_USER_ID'),
  ],
});
const resp = await client.chat.addConversationKeys('RECIPIENT_USER_ID', {
  conversation_key_version: prepared.conversationKeyVersion,
  conversation_participant_keys: prepared.participantKeys.map((pk) => ({
    user_id: pk.userId,
    encrypted_conversation_key: pk.encryptedKey,
    public_key_version: pk.publicKeyVersion,
  })),
  action_signatures: prepared.actionSignatures.map((sig) => ({
    message_id: sig.messageId,
    encoded_message_event_detail: sig.encodedMessageEventDetail,
    message_event_signature: {
      signature: sig.signature,
      public_key_version: sig.publicKeyVersion,
      signature_version: sig.signatureVersion,
    },
  })),
});
const conversationId = resp.data.conversation_id; // canonical id for later requests
const sequenceId = resp.data.sequence_id;
const convKey = prepared.conversationKey;
const convKeyVersion = prepared.conversationKeyVersion;

// public_key_inputs: Vec<PublicKeyInput> from GET public keys
// (user_id, public_key, key_version ← public_key_version)
// New 1:1; set params.conversation_id = Some(id) to rotate later
let prepared = chat.prepare_conversation_key_change(
    ConversationKeyChangeParams::new(public_key_inputs),
)?;
let participant_keys: Vec<_> = prepared
    .participant_keys
    .iter()
    .map(|pk| {
        serde_json::json!({
            "user_id": pk.user_id,
            "encrypted_conversation_key": pk.encrypted_key,
            "public_key_version": pk.public_key_version,
        })
    })
    .collect();
let action_signatures: Vec<_> = prepared
    .action_signatures
    .iter()
    .map(|sig| {
        serde_json::json!({
            "message_id": sig.message_id,
            "encoded_message_event_detail": sig.encoded_message_event_detail,
            "message_event_signature": {
                "signature": sig.signature,
                "public_key_version": sig.public_key_version,
                "signature_version": sig.signature_version,
            },
        })
    })
    .collect();
let body = serde_json::json!({
    "conversation_key_version": prepared.conversation_key_version,
    "conversation_participant_keys": participant_keys,
    "action_signatures": action_signatures,
});
let resp: serde_json::Value = http
    .post(format!("https://api.x.com/2/chat/conversations/{recipient_id}/keys"))
    .header("Authorization", &auth)
    .json(&body)
    .send()?
    .json()?;
// Canonical id for later requests
let conversation_id = resp["data"]["conversation_id"].as_str().unwrap().to_string();
// conversation_key is Option<XChatConversationKey>; encrypt_message wants owned bytes
let conv_key = prepared.conversation_key.expect("key present").to_bytes();
let conv_key_version = prepared.conversation_key_version;

// KeyVersion comes from the public_key_version field on each record
prepared, err := chat.PrepareConversationKeyChange(chatxdk.ConversationKeyChangeParams{
    PublicKeys: []chatxdk.PublicKeyInput{
        {UserID: myUserID, PublicKey: myIdentityPubB64, KeyVersion: myKeyVersion},
        {UserID: recipientID, PublicKey: theirIdentityPubB64, KeyVersion: theirKeyVersion},
    },
    // ConversationID empty for a new 1:1; pass the id to rotate later
})
var parts []map[string]string
for _, pk := range prepared.ParticipantKeys {
    parts = append(parts, map[string]string{
        "user_id":                    pk.UserID,
        "encrypted_conversation_key": pk.EncryptedKey,
        "public_key_version":         pk.PublicKeyVersion,
    })
}
var sigs []map[string]any
for _, sig := range prepared.ActionSignatures {
    sigs = append(sigs, map[string]any{
        "message_id":                   sig.MessageID,
        "encoded_message_event_detail": sig.EncodedMessageEventDetail,
        "message_event_signature": map[string]string{
            "signature":          sig.Signature,
            "public_key_version": sig.PublicKeyVersion,
            "signature_version":  sig.SignatureVersion,
        },
    })
}
body, _ := json.Marshal(map[string]any{
    "conversation_key_version":      prepared.ConversationKeyVersion,
    "conversation_participant_keys": parts,
    "action_signatures":             sigs,
})
req, _ := http.NewRequest(http.MethodPost,
    "https://api.x.com/2/chat/conversations/"+recipientID+"/keys",
    bytes.NewReader(body))
req.Header.Set("Authorization", "Bearer "+accessToken)
req.Header.Set("Content-Type", "application/json")
resp, err := httpClient.Do(req)
// Response data.conversation_id is the canonical id for later requests
_ = resp
convKey := prepared.ConversationKey
convKeyVersion := prepared.ConversationKeyVersion

// KeyVersion comes from the public_key_version field on each record
var prepared = chat.PrepareConversationKeyChange(new ConversationKeyChangeParams(new[] {
    new PublicKeyInput { UserId = myUserId, PublicKey = myPk, KeyVersion = myVer },
    new PublicKeyInput { UserId = recipientId, PublicKey = theirPk, KeyVersion = theirVer },
})); // ConversationId null for a new 1:1; set it to rotate later
var keysBody = new {
    conversation_key_version = prepared.ConversationKeyVersion,
    conversation_participant_keys = prepared.ParticipantKeys.Select(pk => new {
        user_id = pk.UserId,
        encrypted_conversation_key = pk.EncryptedKey,
        public_key_version = pk.PublicKeyVersion,
    }),
    action_signatures = prepared.ActionSignatures.Select(sig => new {
        message_id = sig.MessageId,
        encoded_message_event_detail = sig.EncodedMessageEventDetail,
        message_event_signature = new {
            signature = sig.Signature,
            public_key_version = sig.PublicKeyVersion,
            signature_version = sig.SignatureVersion,
        },
    }),
};
var json = System.Text.Json.JsonSerializer.Serialize(keysBody);
using var content = new StringContent(json, Encoding.UTF8, "application/json");
using var resp = await http.PostAsync(
    $"https://api.x.com/2/chat/conversations/{Uri.EscapeDataString(recipientId)}/keys",
    content);
resp.EnsureSuccessStatusCode();
var data = System.Text.Json.JsonDocument.Parse(await resp.Content.ReadAsStringAsync())
    .RootElement.GetProperty("data");
string conversationId = data.GetProperty("conversation_id").GetString()!; // canonical id
byte[] convKey = prepared.ConversationKey!;
string convKeyVersion = prepared.ConversationKeyVersion;

// keyVersion comes from the public_key_version field on each record
PublicKeyInput mine = new PublicKeyInput();
mine.userId = myUserId; mine.publicKey = myIdentityPubB64; mine.keyVersion = myKeyVersion;
PublicKeyInput theirs = new PublicKeyInput();
theirs.userId = recipientId; theirs.publicKey = theirIdentityPubB64; theirs.keyVersion = theirKeyVersion;

// conversationId stays null for a new 1:1; set it to rotate later
PreparedConversationChange prepared =
    chat.prepareConversationKeyChange(new ConversationKeyChangeParams(List.of(mine, theirs)));

List<Map<String, String>> parts = new ArrayList<>();
for (var pk : prepared.participantKeys) {
    parts.add(Map.of(
        "user_id", pk.userId,
        "encrypted_conversation_key", pk.encryptedKey,
        "public_key_version", pk.publicKeyVersion));
}
List<Map<String, Object>> sigs = new ArrayList<>();
for (var sig : prepared.actionSignatures) {
    sigs.add(Map.of(
        "message_id", sig.messageId,
        "encoded_message_event_detail", sig.encodedMessageEventDetail,
        "message_event_signature", Map.of(
            "signature", sig.signature,
            "public_key_version", sig.publicKeyVersion,
            "signature_version", sig.signatureVersion)));
}
ObjectMapper mapper = new ObjectMapper();
String body = mapper.writeValueAsString(Map.of(
    "conversation_key_version", prepared.conversationKeyVersion,
    "conversation_participant_keys", parts,
    "action_signatures", sigs));
HttpRequest req = HttpRequest.newBuilder()
    .uri(URI.create("https://api.x.com/2/chat/conversations/" + recipientId + "/keys"))
    .header("Authorization", "Bearer " + accessToken)
    .header("Content-Type", "application/json")
    .POST(HttpRequest.BodyPublishers.ofString(body))
    .build();
HttpResponse<String> resp = http.send(req, HttpResponse.BodyHandlers.ofString());
JsonNode data = mapper.readTree(resp.body()).path("data");
String conversationId = data.path("conversation_id").asText(); // canonical id
byte[] convKey = prepared.conversationKey;
String convKeyVersion = prepared.conversationKeyVersion;

// Sender identity resolves from setIdentity (step 2)
const payload = chat.encryptMessage({
  conversationId: 'CONVERSATION_ID',
  text: 'Hello!',
  conversationKey: convKey,
  conversationKeyVersion: convKeyVersion,
});
await client.chat.sendMessage('RECIPIENT_USER_ID', {
  message_id: payload.messageId, // SDK-generated, embedded in the signed event
  encoded_message_create_event: payload.encryptedContent,
  encoded_message_event_signature: payload.encodedEventSignature,
});

use chat_xdk_core::EncryptMessageParams;

// Sender identity resolves from set_identity (step 2)
let payload = chat.encrypt_message(
    EncryptMessageParams::new(&conversation_id, "Hello!")
        .with_conversation_key(conv_key, &conv_key_version),
)?;
let body = serde_json::json!({
    // SDK-generated, embedded in the signed event
    "message_id": payload.message_id,
    "encoded_message_create_event": payload.encrypted_content,
    "encoded_message_event_signature": payload.encoded_event_signature,
});
let path_id = conversation_id.replace(':', "-");
http.post(format!("https://api.x.com/2/chat/conversations/{path_id}/messages"))
    .header("Authorization", &auth)
    .json(&body)
    .send()?;

// Sender identity resolves from SetIdentity (step 2)
payload, err := chat.EncryptMessage(chatxdk.EncryptMessageParams{
    ConversationID:         conversationID,
    Text:                   "Hello!",
    ConversationKey:        convKey,
    ConversationKeyVersion: convKeyVersion,
})
if err != nil {
    log.Fatal(err)
}
body, _ := json.Marshal(map[string]string{
    // SDK-generated, embedded in the signed event
    "message_id":                      payload.MessageID,
    "encoded_message_create_event":    payload.EncryptedContent,
    "encoded_message_event_signature": payload.EncodedEventSignature,
})
pathID := strings.ReplaceAll(conversationID, ":", "-")
req, _ := http.NewRequest(http.MethodPost,
    "https://api.x.com/2/chat/conversations/"+pathID+"/messages",
    bytes.NewReader(body))
req.Header.Set("Authorization", "Bearer "+accessToken)
req.Header.Set("Content-Type", "application/json")
resp, err := httpClient.Do(req)
_ = resp

// Sender identity resolves from SetIdentity (step 2)
var payload = chat.EncryptMessage(new EncryptMessageParams(conversationId, "Hello!") {
    ConversationKey = convKey,
    ConversationKeyVersion = convKeyVersion,
});
var sendJson = System.Text.Json.JsonSerializer.Serialize(new Dictionary<string, string> {
    // SDK-generated, embedded in the signed event
    ["message_id"] = payload.MessageId,
    ["encoded_message_create_event"] = payload.EncryptedContent,
    ["encoded_message_event_signature"] = payload.EncodedEventSignature,
});
using var content = new StringContent(sendJson, Encoding.UTF8, "application/json");
var pathId = conversationId.Replace(':', '-');
using var resp = await http.PostAsync(
    $"https://api.x.com/2/chat/conversations/{Uri.EscapeDataString(pathId)}/messages",
    content);
resp.EnsureSuccessStatusCode();

// Sender identity resolves from setIdentity (step 2)
EncryptMessageParams params = new EncryptMessageParams(conversationId, "Hello!");
params.conversationKey = convKey;
params.conversationKeyVersion = convKeyVersion;
SendPayload payload = chat.encryptMessage(params);

String pathId = conversationId.replace(':', '-');
String sendJson = new ObjectMapper().writeValueAsString(Map.of(
    // SDK-generated, embedded in the signed event
    "message_id", payload.messageId,
    "encoded_message_create_event", payload.encryptedContent,
    "encoded_message_event_signature", payload.encodedEventSignature));
HttpRequest req = HttpRequest.newBuilder()
    .uri(URI.create("https://api.x.com/2/chat/conversations/" + pathId + "/messages"))
    .header("Authorization", "Bearer " + accessToken)
    .header("Content-Type", "application/json")
    .POST(HttpRequest.BodyPublishers.ofString(sendJson))
    .build();
http.send(req, HttpResponse.BodyHandlers.ofString());

// Once per process: fill the signing-key store and enable the key cache
async function signingKeysFor(userId: string) {
  const resp = await client.chat.getUserPublicKeys(userId, {
    publicKeyFields: [
      'public_key_version', 'public_key', 'signing_public_key', 'identity_public_key_signature',
    ],
  });
  return resp.data.map((r: {
    public_key_version: string;
    public_key: string;
    signing_public_key: string;
    identity_public_key_signature: string;
  }) => ({
    userId,
    publicKeyVersion: r.public_key_version,
    publicKey: r.signing_public_key,
    identityPublicKey: r.public_key,
    identityPublicKeySignature: r.identity_public_key_signature,
  }));
}

chat.setSigningKeys([
  ...(await signingKeysFor('YOUR_USER_ID')),
  ...(await signingKeysFor('RECIPIENT_USER_ID')),
]);
chat.setCacheKeys(true);

// Initial load or pagination: batch decrypt. Conversation keys are
// extracted from the KeyChange events in the batch; per-event failures
// are collected in result.errors, never thrown.
const result = chat.decryptEvents(allEventsB64);
for (const dm of result.messages) {
  if (dm.event.type === 'message' && dm.event.content?.contentType === 'text') {
    console.log(dm.event.senderId, dm.event.content.text, dm.event.verified);
  }
}

// Live traffic: one event at a time
function handlePayload(payload: {
  encoded_event: string;
  conversation_key_change_event?: string;
}) {
  if (payload.conversation_key_change_event) {
    // A rotation enters the key cache only after its signature
    // verifies, which is what decryptEvents does
    chat.decryptEvents([payload.conversation_key_change_event]);
  }
  const event = chat.decryptEvent(payload.encoded_event); // throws on failure
  if (event.type === 'message' && event.content?.contentType === 'text') {
    console.log(event.senderId, event.content.text, event.verified);
  }
}

// Once per instance: fill the signing-key store (Vec<SigningKeyEntry>
// from GET /2/users/{id}/public_keys) and enable the key cache
chat.set_signing_keys(participant_signing_keys);
chat.set_cache_keys(true);

// Initial load: batch decrypt — per-event failures land in result.errors
let result = chat.decrypt_events(&all_events_b64, &[]);

// Live traffic: a rotation enters the key cache only after its
// signature verifies, which is what decrypt_events does
if let Some(kc) = key_change_b64.as_deref() {
    chat.decrypt_events(&[kc], &[]);
}
let event = chat.decrypt_event(&encoded_event, &Default::default(), &[])?;

// Once per instance: fill the signing-key store ([]SigningKeyEntry
// from GET /2/users/{id}/public_keys) and enable the key cache
if err := chat.SetSigningKeys(participantSigningKeys); err != nil {
    log.Fatal(err)
}
chat.SetCacheKeys(true)

// Initial load: batch decrypt — per-event failures land in result.Errors
result, err := chat.DecryptEvents(allEventsB64, nil)
if err != nil {
    log.Fatal(err)
}
for _, dm := range result.Messages {
    if dm.Event.Type == "Message" {
        fmt.Println(dm.Event.AsMessage().Text())
    }
}

// Live traffic: a rotation enters the key cache only after its
// signature verifies, which is what DecryptEvents does
if keyChange != "" {
    chat.DecryptEvents([]string{keyChange}, nil)
}
event, err := chat.DecryptEvent(encodedEvent, nil, nil)
if err == nil && event.Type == "Message" {
    fmt.Println(event.AsMessage().Text())
}

// Once per instance: fill the signing-key store (SigningKeyEntry list
// from GET /2/users/{id}/public_keys) and enable the key cache
chat.SetSigningKeys(participantSigningKeys);
chat.SetCacheKeys(true);

// Initial load: batch decrypt — per-event failures land in result.Errors
var result = chat.DecryptEvents(allEventsB64);
foreach (var dm in result.Messages)
{
    if (dm.Event.GetProperty("type").GetString() == "Message")
        Console.WriteLine(dm.Event.GetProperty("content").GetProperty("text").GetString());
}

// Live traffic: a rotation enters the key cache only after its
// signature verifies, which is what DecryptEvents does
if (!string.IsNullOrEmpty(keyChangeB64))
    chat.DecryptEvents(new[] { keyChangeB64 });
var evt = chat.DecryptEvent(encodedEvent);  // throws on failure
if (evt.GetProperty("type").GetString() == "Message")
    Console.WriteLine(evt.GetProperty("content").GetProperty("text").GetString());

// Once per instance: fill the signing-key store (SigningKeyEntry list
// from GET /2/users/{id}/public_keys) and enable the key cache
chat.setSigningKeys(participantSigningKeys);
chat.setCacheKeys(true);

// Initial load: batch decrypt — per-event failures land in result.errors
DecryptEventsResult result = chat.decryptEvents(allEventsB64, null);
for (DecryptedMessage dm : result.messages) {
    if ("Message".equals(dm.event.path("type").asText())) {
        System.out.println(dm.event.path("content").path("text").asText());
    }
}

// Live traffic: a rotation enters the key cache only after its
// signature verifies, which is what decryptEvents does
if (keyChangeB64 != null && !keyChangeB64.isEmpty()) {
    chat.decryptEvents(List.of(keyChangeB64), null);
}
JsonNode evt = chat.decryptEvent(encodedEvent, (Map<String, byte[]>) null, null);
if ("Message".equals(evt.path("type").asText())) {
    System.out.println(evt.path("content").path("text").asText());
}