fix: support legacy and current DSH hosts

plugin-src/host/channels/dingtalk/index.mjs

@@ -2,7 +2,7 @@ import { createProductionController } from './production.mjs';
 import { installDingtalkRpc } from './rpc.mjs';
 
 export const name = 'dsh-dingtalk-host';
-export const inject = ['connection', 'credentials', 'apiProxy', 'typertGateway'];
+export const inject = ['connection', 'credentials', 'typertGateway'];
 
 export async function apply(ctx, config = {}) {
   if (config?.controller) {

plugin-src/host/channels/discord/index.mjs

@@ -2,7 +2,7 @@ import { createProductionController } from './production.mjs';
 import { installDiscordRpc } from './rpc.mjs';
 
 export const name = 'dsh-im-discord-host';
-export const inject = ['connection', 'credentials', 'apiProxy', 'typertGateway'];
+export const inject = ['connection', 'credentials', 'typertGateway'];
 
 export async function apply(ctx, config = {}) {
   if (config?.controller) {

plugin-src/host/channels/feishu/index.mjs

@@ -3,7 +3,7 @@ import { createProductionController } from './production.mjs';
 import { installFeishuRpc } from './rpc.mjs';
 
 export const name = 'dsh-feishu-host';
-export const inject = ['connection', 'credentials', 'apiProxy', 'typertGateway'];
+export const inject = ['connection', 'credentials', 'typertGateway'];
 
 function controllerFrom(ctx, config) {
   if (config?.controller) return config.controller;

plugin-src/host/channels/qq/index.mjs

@@ -2,7 +2,7 @@ import { createProductionController } from './production.mjs';
 import { installQqRpc } from './rpc.mjs';
 
 export const name = 'dsh-im-qq-host';
-export const inject = ['connection', 'credentials', 'apiProxy', 'typertGateway'];
+export const inject = ['connection', 'credentials', 'typertGateway'];
 
 export async function apply(ctx, config = {}) {
   if (config?.controller) {

plugin-src/host/channels/slack/index.mjs

@@ -2,7 +2,7 @@ import { createProductionController } from './production.mjs';
 import { installSlackRpc } from './rpc.mjs';
 
 export const name = 'dsh-im-slack-host';
-export const inject = ['connection', 'credentials', 'apiProxy', 'typertGateway'];
+export const inject = ['connection', 'credentials', 'typertGateway'];
 
 export async function apply(ctx, config = {}) {
   if (config?.controller) return installSlackRpc(ctx, config.controller, config.rpcAuthority);

plugin-src/host/channels/telegram/index.mjs

@@ -2,7 +2,7 @@ import { createProductionController } from './production.mjs';
 import { installTelegramRpc } from './rpc.mjs';
 
 export const name = 'dsh-im-telegram-host';
-export const inject = ['connection', 'credentials', 'apiProxy', 'typertGateway'];
+export const inject = ['connection', 'credentials', 'typertGateway'];
 
 export async function apply(ctx, config = {}) {
   if (config?.controller) {

plugin-src/host/channels/wecom/index.mjs

@@ -2,7 +2,7 @@ import { createProductionController } from './production.mjs';
 import { installWecomRpc } from './rpc.mjs';
 
 export const name = 'dsh-im-wecom-host';
-export const inject = ['connection', 'credentials', 'apiProxy', 'typertGateway'];
+export const inject = ['connection', 'credentials', 'typertGateway'];
 
 export async function apply(ctx, config = {}) {
   if (config?.controller) {

plugin-src/host/channels/weixin/index.mjs

@@ -2,7 +2,7 @@ import { createProductionController } from './production.mjs';
 import { installWeixinRpc } from './rpc.mjs';
 
 export const name = 'dsh-weixin-host';
-export const inject = ['connection', 'credentials', 'apiProxy', 'typertGateway'];
+export const inject = ['connection', 'credentials', 'typertGateway'];
 
 export async function apply(ctx, config = {}) {
   if (config?.controller) {

plugin-src/host/channels/whatsapp/index.mjs

@@ -2,7 +2,7 @@ import { createProductionController } from './production.mjs';
 import { installWhatsappRpc } from './rpc.mjs';
 
 export const name = 'dsh-im-whatsapp-host';
-export const inject = ['connection', 'apiProxy', 'typertGateway'];
+export const inject = ['connection', 'typertGateway'];
 
 export async function apply(ctx, config = {}) {
   if (config?.controller) {

plugin-src/host/harness-connection.mjs

@@ -1,13 +1,18 @@
+import { modernHarnessApi } from './modern-harness-api.mjs';
+
+function optionalService(ctx, name) {
+  if (ctx && Object.hasOwn(ctx, name)) return ctx[name];
+  return typeof ctx?.get === 'function' ? ctx.get(name) : undefined;
+}
+
 /** Connect to this Host directly unless an external Harness URL was configured. */
 export function harnessConnection(ctx, config = {}) {
   if (config.harnessBaseUrl !== undefined) {
     return { baseUrl: new URL(config.harnessBaseUrl) };
   }
-  if (!ctx?.apiProxy) {
-    throw new TypeError('dsh-im requires the Host apiProxy service; check that DSH has finished loading its Host services');
-  }
+  const apiProxy = optionalService(ctx, 'apiProxy') ?? modernHarnessApi(ctx);
   return {
-    apiProxy: ctx.apiProxy,
+    apiProxy,
     // Cordis child contexts share one root; different Hosts must not share
     // ownership of pending questions and approvals.
     interactionScope: ctx.root ?? ctx,

plugin-src/host/index.mjs

@@ -16,7 +16,6 @@ export const name = 'dsh-im-host';
 export const inject = [
   'connection',
   'credentials',
-  'apiProxy',
   'typertGateway',
 ];
 
@@ -55,38 +54,53 @@ export function createImHostPlugin(internals = {}) {
     name,
     inject,
     async apply(ctx, config = {}) {
-      setImHostLanguage(config.language ?? process.env.DSH_IM_LANGUAGE);
+      const activate = async (readyCtx) => {
+        await activateChannels(readyCtx, config);
+      };
       if (typeof ctx?.inject === 'function') {
-        ctx.inject(['tools', 'systemPrompt'], (artifactCtx) => {
-          installOutboundArtifactTool(artifactCtx);
-        });
-      } else {
-        installOutboundArtifactTool(ctx);
-      }
-      const logger = typeof ctx?.logger === 'function'
-        ? ctx.logger(name)
-        : (ctx?.logger ?? console);
-      if (ctx?.connection?.rpc) {
-        try {
-          startUpdate(ctx);
-        } catch (error) {
-          logger.error?.('[dsh-im] failed to activate update management; continuing with channels', error);
-        }
-      }
-      const failures = [];
-      for (const [channel, start] of channels) {
-        try {
-          await start(ctx, channelConfig(config, channel));
-        } catch (error) {
-          failures.push(error);
-          logger.error?.(`[dsh-im] failed to activate ${channel}; continuing with the remaining channels`, error);
-        }
-      }
-      if (failures.length === channels.length) {
-        throw new AggregateError(failures, 'dsh-im failed to activate every channel');
+        const modern = typeof ctx?.typertGateway?.stream === 'function';
+        await ctx.inject(
+          modern ? ['sessionController', 'workspaceController'] : ['apiProxy'],
+          activate,
+        );
+        return;
       }
+      await activate(ctx);
     },
   });
+
+  async function activateChannels(ctx, config) {
+    setImHostLanguage(config.language ?? process.env.DSH_IM_LANGUAGE);
+    if (typeof ctx?.inject === 'function') {
+      ctx.inject(['tools', 'systemPrompt'], (artifactCtx) => {
+        installOutboundArtifactTool(artifactCtx);
+      });
+    } else {
+      installOutboundArtifactTool(ctx);
+    }
+    const logger = typeof ctx?.logger === 'function'
+      ? ctx.logger(name)
+      : (ctx?.logger ?? console);
+    if (ctx?.connection?.rpc) {
+      try {
+        startUpdate(ctx);
+      } catch (error) {
+        logger.error?.('[dsh-im] failed to activate update management; continuing with channels', error);
+      }
+    }
+    const failures = [];
+    for (const [channel, start] of channels) {
+      try {
+        await start(ctx, channelConfig(config, channel));
+      } catch (error) {
+        failures.push(error);
+        logger.error?.(`[dsh-im] failed to activate ${channel}; continuing with the remaining channels`, error);
+      }
+    }
+    if (failures.length === channels.length) {
+      throw new AggregateError(failures, 'dsh-im failed to activate every channel');
+    }
+  }
 }
 
 export async function apply(ctx, config = {}) {

plugin-src/host/modern-harness-api.mjs

@@ -0,0 +1,577 @@
+import { randomUUID } from 'node:crypto';
+
+import { hasActiveHarnessInteractionOwner } from '../../src/channels/shared/harness-client.mjs';
+
+const modernApis = new WeakMap();
+
+function failureOf(error) {
+  const failure = error?.failure;
+  if (failure && typeof failure === 'object'
+    && typeof failure.code === 'string'
+    && typeof failure.message === 'string') {
+    return {
+      code: failure.code,
+      message: failure.message,
+      details: failure.details && typeof failure.details === 'object' ? failure.details : {},
+    };
+  }
+  if (error?.name === 'AbortError' || error?.name === 'RemoteInvocationCancelled') {
+    return {
+      code: 'cancelled',
+      message: error instanceof Error ? error.message : 'Harness request was cancelled',
+      details: {},
+    };
+  }
+  return {
+    code: 'internal',
+    message: error instanceof Error ? error.message : String(error),
+    details: {},
+  };
+}
+
+function rpcResult(request, operation) {
+  return Promise.resolve().then(operation).then(
+    (value) => ({ rpcId: request.rpcId, result: { ok: true, value } }),
+    (error) => ({ rpcId: request.rpcId, result: { ok: false, error: failureOf(error) } }),
+  );
+}
+
+function remoteRequest(namespace, method, args, signal) {
+  return {
+    namespace,
+    method,
+    args,
+    ...(signal === undefined ? {} : { signal }),
+  };
+}
+
+function questionError(message, code) {
+  const error = new Error(message);
+  error.name = 'UserQuestionError';
+  error.code = code;
+  return error;
+}
+
+function matchesQuestions(value, pending) {
+  if (!value || typeof value !== 'object'
+    || value.sessionId !== pending.sessionId
+    || !value.answer || typeof value.answer !== 'object'
+    || !Array.isArray(value.answer.answers)
+    || value.answer.answers.length !== pending.questions.length) return false;
+  return value.answer.answers.every((answer, index) => {
+    const question = pending.questions[index];
+    if (!answer || typeof answer !== 'object'
+      || answer.id !== question.id
+      || !Array.isArray(answer.selected)
+      || answer.selected.some((label) => typeof label !== 'string')
+      || new Set(answer.selected).size !== answer.selected.length
+      || (answer.custom !== undefined && typeof answer.custom !== 'string')) return false;
+    const custom = answer.custom?.trim();
+    if (custom !== undefined && !custom) return false;
+    if (question.multiSelect !== true
+      && ((custom !== undefined && answer.selected.length > 0) || answer.selected.length > 1)) return false;
+    const labels = new Set(question.options?.map((option) => option.label) ?? []);
+    return answer.selected.every((label) => labels.has(label));
+  });
+}
+
+function expandChunkRecord(record) {
+  if (record?.type === 'event' && record.event && typeof record.event === 'object') {
+    return [{ event: record.event }];
+  }
+  const packed = record?.type === 'chunks' ? record.event : null;
+  if (!packed || typeof packed !== 'object') {
+    throw new Error('Harness returned an invalid session history record');
+  }
+  const { data } = packed;
+  const kind = packed.type;
+  const members = kind === 'chunkrow/tool-call-chunks' ? data?.args : data?.texts;
+  if (!data || !Array.isArray(members) || members.length === 0
+    || members.some((member) => typeof member !== 'string')
+    || !Array.isArray(data.dt) || data.dt.length !== members.length - 1) {
+    throw new Error('Harness returned an invalid packed session chunk');
+  }
+  let time = packed.time;
+  return members.map((member, index) => {
+    if (index > 0) time += data.dt[index - 1];
+    let chunk;
+    if (kind === 'chunkrow/text-chunks') {
+      chunk = { type: 'text-delta', index: data.index, text: member };
+    } else if (kind === 'chunkrow/reasoning-chunks') {
+      chunk = { type: 'reasoning-delta', index: data.index, text: member };
+    } else if (kind === 'chunkrow/tool-call-chunks') {
+      chunk = {
+        type: 'tool-call-delta',
+        index: data.index,
+        id: data.id,
+        ...(Object.hasOwn(data, 'name') ? { name: data.name } : {}),
+        argumentsDelta: member,
+      };
+    } else {
+      throw new Error(`Harness returned an unsupported packed session chunk: ${String(kind)}`);
+    }
+    return {
+      event: {
+        type: 'assistant/chunk',
+        seq: packed.seq + index,
+        time,
+        data: { turn: data.turn, step: data.step, chunk },
+      },
+    };
+  });
+}
+
+function historyEntries(records) {
+  if (!Array.isArray(records)) throw new Error('Harness returned invalid session history records');
+  return records.flatMap(expandChunkRecord);
+}
+
+class MuxSubscription {
+  #frames = [];
+  #waiting = null;
+  #closed = false;
+  #signal;
+  #onAbort;
+  #dispose;
+
+  constructor(signal, dispose) {
+    this.#signal = signal;
+    this.#dispose = dispose;
+    this.#onAbort = () => this.close();
+    signal?.addEventListener('abort', this.#onAbort, { once: true });
+    if (signal?.aborted) this.close();
+  }
+
+  push(frame) {
+    if (this.#closed) return;
+    if (this.#waiting) {
+      const resolve = this.#waiting;
+      this.#waiting = null;
+      resolve({ value: frame, done: false });
+    } else {
+      this.#frames.push(frame);
+    }
+  }
+
+  next() {
+    if (this.#frames.length > 0) {
+      return Promise.resolve({ value: this.#frames.shift(), done: false });
+    }
+    if (this.#closed) return Promise.resolve({ value: undefined, done: true });
+    return new Promise((resolve) => { this.#waiting = resolve; });
+  }
+
+  return() {
+    this.close();
+    return Promise.resolve({ value: undefined, done: true });
+  }
+
+  close() {
+    if (this.#closed) return;
+    this.#closed = true;
+    this.#signal?.removeEventListener('abort', this.#onAbort);
+    this.#dispose?.();
+    this.#dispose = null;
+    if (this.#waiting) {
+      const resolve = this.#waiting;
+      this.#waiting = null;
+      resolve({ value: undefined, done: true });
+    }
+  }
+
+  [Symbol.asyncIterator]() {
+    return this;
+  }
+}
+
+class ModernHarnessApi {
+  #gateway;
+  #scope;
+  #mux = new Set();
+  #pendingQuestions = new Map();
+  #pendingApprovals = new Map();
+  #sessionCursors = new Map();
+  #disposers = [];
+  #disposed = false;
+
+  constructor(ctx, gateway, scope) {
+    this.#gateway = gateway;
+    this.#scope = scope;
+
+    this.host = Object.freeze({
+      describe: (request) => rpcResult(request, () => ({ ready: true, transport: 'typert' })),
+    });
+    this.workspace = Object.freeze({
+      list: (request, signal) => rpcResult(request, () => this.#workspaceList(signal)),
+      create: (request, signal) => rpcResult(request, () => this.#invoke(
+        'workspace', 'create', { request: request.payload }, signal,
+      )),
+    });
+    this.sessions = Object.freeze({
+      list: (request, signal) => rpcResult(request, () => this.#invoke(
+        'session', 'list', { _request: request.payload }, signal,
+      )),
+      create: (request, signal) => rpcResult(request, () => this.#invoke(
+        'session', 'create', { request: request.payload }, signal,
+      )),
+      history: (request, signal) => rpcResult(request, () => this.#history(request.payload, signal)),
+      prompt: (request, signal) => rpcResult(request, () => this.#invoke(
+        'session',
+        'prompt',
+        { request: { requestId: request.rpcId, ...request.payload } },
+        signal,
+      )),
+      cancel: (request, signal) => rpcResult(request, () => this.#invoke(
+        'session', 'cancel', { request: { sessionId: request.payload.sessionId } }, signal,
+      )),
+      models: (request, signal) => rpcResult(request, () => this.#sessionModels(
+        request.payload.sessionId, signal,
+      )),
+      selectModel: (request, signal) => rpcResult(request, () => this.#invoke(
+        'session', 'selectModel', { request: request.payload }, signal,
+      )),
+    });
+    this.llm = Object.freeze({
+      models: (request, signal) => rpcResult(request, async () => {
+        const catalog = await this.#modelCatalog(signal);
+        return { groups: catalog.groups, failures: catalog.failures };
+      }),
+    });
+    this.events = Object.freeze({
+      mux: (_request, signal) => this.#openMux(signal),
+    });
+    this.respond = (message) => Promise.resolve(this.#respond(message));
+
+    if (typeof ctx?.on === 'function') {
+      this.#disposers.push(ctx.on('session/event', (session, event) => {
+        const sessionId = session?.id;
+        if (typeof sessionId !== 'string' || !event || typeof event !== 'object') return;
+        if (Number.isSafeInteger(event.seq)) this.#rememberCursor(sessionId, event.seq);
+        this.#broadcast({ type: 'session/event', sessionId, event });
+      }, { global: true }));
+      this.#disposers.push(ctx.on(
+        'approval/request',
+        (request, next) => this.#requestApproval(request, next),
+        { global: true, prepend: true },
+      ));
+      this.#disposers.push(ctx.on(
+        'user-questions/request',
+        (request, next) => this.#requestQuestion(request, next),
+        { global: true, prepend: true },
+      ));
+    }
+  }
+
+  async #invoke(namespace, method, args, signal) {
+    return this.#gateway.invoke(remoteRequest(namespace, method, args, signal));
+  }
+
+  async #streamFirst(namespace, method, args, signal) {
+    const controller = new AbortController();
+    const streamSignal = signal
+      ? AbortSignal.any([signal, controller.signal])
+      : controller.signal;
+    let iterator;
+    try {
+      const source = await this.#gateway.stream(remoteRequest(
+        namespace, method, args, streamSignal,
+      ));
+      iterator = source[Symbol.asyncIterator]();
+      const first = await iterator.next();
+      if (first.done) throw new Error(`Harness ${namespace}.${method} stream ended before its baseline`);
+      return first.value;
+    } finally {
+      controller.abort(new DOMException('Baseline received', 'AbortError'));
+      await Promise.resolve(iterator?.return?.()).catch(() => undefined);
+    }
+  }
+
+  async #workspaceList(signal) {
+    const frame = await this.#streamFirst('workspace', 'follow', {}, signal);
+    if (frame?.type !== 'baseline' || !frame.value || typeof frame.value !== 'object') {
+      throw new Error('Harness workspace.follow returned no baseline');
+    }
+    return frame.value;
+  }
+
+  async #sessionSnapshot(sessionId, maxMessages, signal) {
+    const frame = await this.#streamFirst('session', 'follow', {
+      request: {
+        address: { kind: 'session', sessionId },
+        maxMessages,
+      },
+    }, signal);
+    if (frame?.type !== 'snapshot' || !Number.isSafeInteger(frame.cursor)) {
+      throw new Error('Harness session.follow returned no snapshot');
+    }
+    this.#rememberCursor(sessionId, frame.cursor);
+    return frame;
+  }
+
+  async #history(payload, signal) {
+    const { sessionId, maxMessages = 50, beforeSeq } = payload;
+    let cursor = this.#sessionCursors.get(sessionId);
+    if (cursor === undefined) {
+      const snapshot = await this.#sessionSnapshot(sessionId, maxMessages, signal);
+      cursor = this.#sessionCursors.get(sessionId) ?? snapshot.cursor;
+      if (beforeSeq === undefined && cursor === snapshot.cursor) {
+        return {
+          events: historyEntries(snapshot.records),
+          hasMore: snapshot.hasMore === true,
+          ...(snapshot.projections === undefined ? {} : { projections: snapshot.projections }),
+        };
+      }
+    }
+    const page = await this.#invoke('session', 'page', {
+      request: {
+        address: { kind: 'session', sessionId },
+        throughSeq: cursor,
+        maxMessages,
+        ...(beforeSeq === undefined ? {} : { beforeSeq }),
+      },
+    }, signal);
+    return { events: historyEntries(page.records), hasMore: page.hasMore === true };
+  }
+
+  #rememberCursor(sessionId, cursor) {
+    const previous = this.#sessionCursors.get(sessionId);
+    if (previous === undefined || cursor > previous) this.#sessionCursors.set(sessionId, cursor);
+  }
+
+  #modelCatalog(signal) {
+    return this.#invoke('session', 'modelCatalog', {}, signal);
+  }
+
+  async #sessionModels(sessionId, signal) {
+    const [catalog, list] = await Promise.all([
+      this.#modelCatalog(signal),
+      this.#invoke('session', 'list', { _request: {} }, signal),
+    ]);
+    const summary = list?.items?.find((item) => item?.sessionId === sessionId);
+    if (!summary) {
+      const error = new Error(`session "${sessionId}" not found`);
+      error.failure = {
+        code: 'session-not-found',
+        message: error.message,
+        details: { sessionId },
+      };
+      throw error;
+    }
+    const selection = summary.projections?.values?.modelSelection;
+    const current = selection?.next ?? selection?.lastUsed ?? catalog.default;
+    return {
+      current,
+      routable: catalog.routableProviders.includes(current.provider),
+      groups: catalog.groups,
+      failures: catalog.failures,
+    };
+  }
+
+  #openMux(signal) {
+    let subscription;
+    subscription = new MuxSubscription(signal, () => this.#mux.delete(subscription));
+    this.#mux.add(subscription);
+    for (const pending of this.#pendingQuestions.values()) subscription.push(this.#questionFrame(pending));
+    for (const pending of this.#pendingApprovals.values()) subscription.push(this.#approvalFrame(pending));
+    return subscription;
+  }
+
+  #broadcast(payload, rpcId = randomUUID()) {
+    const frame = { rpcId, payload };
+    for (const subscription of this.#mux) subscription.push(frame);
+  }
+
+  #claimableAgent(agent) {
+    const sessionId = agent?.session?.id ?? agent?.id;
+    if (typeof sessionId !== 'string' || !agent?.session || !Array.isArray(agent.session.events)) {
+      return null;
+    }
+    return hasActiveHarnessInteractionOwner(
+      this.#scope,
+      sessionId,
+      agent.session.events,
+    ) ? { sessionId, session: agent.session } : null;
+  }
+
+  #questionFrame(pending) {
+    return {
+      rpcId: pending.rpcId,
+      payload: {
+        type: 'question/requested',
+        sessionId: pending.sessionId,
+        questions: pending.questions,
+      },
+    };
+  }
+
+  #requestQuestion(request, next) {
+    const owner = this.#claimableAgent(request?.agent);
+    if (!owner) return next();
+    if (request.signal?.aborted) {
+      return Promise.reject(questionError(
+        'ask_user_question was aborted before the user answered', 'ASK_ABORTED',
+      ));
+    }
+    return new Promise((resolve, reject) => {
+      const pending = {
+        rpcId: randomUUID(),
+        sessionId: owner.sessionId,
+        questions: request.questions,
+        signal: request.signal,
+        settle: (outcome, value) => {
+          if (!this.#pendingQuestions.delete(pending.rpcId)) return;
+          request.signal?.removeEventListener('abort', onAbort);
+          this.#broadcast({
+            type: 'question/resolved',
+            sessionId: pending.sessionId,
+            questionRpcId: pending.rpcId,
+            outcome,
+          });
+          if (outcome === 'answered') resolve(value);
+          else reject(value);
+        },
+      };
+      const onAbort = () => pending.settle('cancelled', questionError(
+        'ask_user_question was aborted before the user answered', 'ASK_ABORTED',
+      ));
+      this.#pendingQuestions.set(pending.rpcId, pending);
+      request.signal?.addEventListener('abort', onAbort, { once: true });
+      this.#broadcast(this.#questionFrame(pending).payload, pending.rpcId);
+    });
+  }
+
+  #approvalFrame(pending) {
+    return {
+      rpcId: pending.rpcId,
+      payload: {
+        type: 'approval/requested',
+        sessionId: pending.sessionId,
+        approvalId: pending.approvalId,
+        toolName: pending.toolName,
+        ...(pending.callId === undefined ? {} : { callId: pending.callId }),
+        ...(pending.reason === undefined ? {} : { reason: pending.reason }),
+      },
+    };
+  }
+
+  #requestApproval(request, next) {
+    const owner = this.#claimableAgent(request?.agent);
+    if (!owner) return next();
+    if (request.signal?.aborted) return Promise.resolve('cancelled');
+    const claimed = new Set([...this.#pendingApprovals.values()].map((entry) => entry.approvalId));
+    const decided = new Set();
+    let approvalId;
+    for (let index = owner.session.events.length - 1; index >= 0; index -= 1) {
+      const event = owner.session.events[index];
+      if (event.type === 'approval/decided') {
+        decided.add(event.data?.id);
+      } else if (event.type === 'approval/asked') {
+        const id = event.data?.id;
+        if (!id || decided.has(id) || claimed.has(id)) continue;
+        if ((request.callId ?? null) !== (event.data?.callId ?? null)) continue;
+        approvalId = id;
+        break;
+      }
+    }
+    if (approvalId === undefined) return next();
+    return new Promise((resolve) => {
+      const pending = {
+        rpcId: randomUUID(),
+        sessionId: owner.sessionId,
+        approvalId,
+        toolName: request.toolName,
+        callId: request.callId,
+        reason: request.reason,
+        settle: (outcome) => {
+          if (!this.#pendingApprovals.delete(pending.rpcId)) return;
+          request.signal?.removeEventListener('abort', onAbort);
+          this.#broadcast({
+            type: 'approval/resolved',
+            sessionId: pending.sessionId,
+            approvalId: pending.approvalId,
+            outcome,
+          });
+          resolve(outcome);
+        },
+      };
+      const onAbort = () => pending.settle('cancelled');
+      this.#pendingApprovals.set(pending.rpcId, pending);
+      request.signal?.addEventListener('abort', onAbort, { once: true });
+      this.#broadcast(this.#approvalFrame(pending).payload, pending.rpcId);
+    });
+  }
+
+  #respond(message) {
+    const approval = this.#pendingApprovals.get(message?.rpcId);
+    if (approval) {
+      const value = message?.result?.value;
+      if (message?.result?.ok !== true
+        || !value || typeof value !== 'object'
+        || value.sessionId !== approval.sessionId
+        || value.approvalId !== approval.approvalId
+        || (value.outcome !== 'allowed-once' && value.outcome !== 'rejected')) {
+        return { accepted: false, reason: 'bad-response' };
+      }
+      approval.settle(value.outcome);
+      return { accepted: true };
+    }
+    const question = this.#pendingQuestions.get(message?.rpcId);
+    if (!question) return { accepted: false, reason: 'not-pending' };
+    if (message?.result?.ok !== true) {
+      if (message?.result?.error?.code !== 'cancelled') {
+        return { accepted: false, reason: 'bad-response' };
+      }
+      question.settle('cancelled', questionError(
+        'the user cancelled ask_user_question', 'ASK_CANCELLED',
+      ));
+      return { accepted: true };
+    }
+    if (!matchesQuestions(message.result.value, question)) {
+      return { accepted: false, reason: 'bad-response' };
+    }
+    const answer = {
+      answers: message.result.value.answer.answers.map((item) => ({
+        id: item.id,
+        selected: [...item.selected],
+        ...(item.custom === undefined ? {} : { custom: item.custom }),
+      })),
+    };
+    question.settle('answered', answer);
+    return { accepted: true };
+  }
+
+  dispose() {
+    if (this.#disposed) return;
+    this.#disposed = true;
+    for (const subscription of [...this.#mux]) subscription.close();
+    for (const pending of [...this.#pendingApprovals.values()]) pending.settle('cancelled');
+    for (const pending of [...this.#pendingQuestions.values()]) pending.settle(
+      'cancelled',
+      questionError('dsh-im interaction adapter was disposed', 'ASK_ABORTED'),
+    );
+    for (const dispose of this.#disposers.splice(0).reverse()) dispose?.();
+  }
+}
+
+/** Create one modern compatibility API per Cordis Host root. */
+export function modernHarnessApi(ctx) {
+  const scope = ctx?.root ?? ctx;
+  if (!scope || !['object', 'function'].includes(typeof scope)) {
+    throw new TypeError('dsh-im requires a Cordis Host context');
+  }
+  const cached = modernApis.get(scope);
+  if (cached) return cached;
+  const gateway = ctx?.typertGateway;
+  if (!gateway || typeof gateway.invoke !== 'function' || typeof gateway.stream !== 'function') {
+    throw new TypeError('dsh-im requires the modern Host Typert gateway');
+  }
+  const api = new ModernHarnessApi(ctx, gateway, scope);
+  modernApis.set(scope, api);
+  if (typeof ctx.effect === 'function') {
+    ctx.effect(() => () => {
+      if (modernApis.get(scope) === api) modernApis.delete(scope);
+      api.dispose();
+    }, 'dsh-im: modern Harness compatibility API');
+  }
+  return api;
+}