Bare API /new creates an unreachable session binding

From the repository root, save this as repro_api_new_session_header.mts and run:

pnpm install --frozen-lockfile
pnpm exec tsx repro_api_new_session_header.mts

import { Readable } from "node:stream";
import { ApiServerChannel } from "./src/adapters/channel/api-server/ApiServerChannel.js";
import type { Gateway, GatewayEvent, GatewaySubmitTurnInput } from "./src/gateway/index.js";

type Call = Pick<GatewaySubmitTurnInput, "sessionKey" | "channelKey" | "message">;

const calls: Call[] = [];

const gateway = {
  submitTurn(input: GatewaySubmitTurnInput): AsyncIterable<GatewayEvent> {
    calls.push({
      sessionKey: input.sessionKey,
      channelKey: input.channelKey,
      message: input.message,
    });
    return (async function* (): AsyncGenerator<GatewayEvent> {
      yield { type: "assistant_text_delta", text: "fixture reply" };
      yield {
        type: "turn_completed",
        usage: { inputTokens: 0, outputTokens: 0, totalTokens: 0 },
        finishReason: "completed",
      };
    })();
  },
} as unknown as Gateway;

function redact(value: string): string {
  return value
    .replace(/api-[0-9a-f-]{36}/g, "api-<uuid>")
    .replace(/s_[0-9a-f-]{36}/g, "s_<uuid>");
}

class FakeResponse {
  statusCode = 200;
  readonly headers = new Map<string, string>();
  private readonly chunks: string[] = [];

  setHeader(name: string, value: string): void {
    this.headers.set(name.toLowerCase(), String(value));
  }

  write(chunk: string): boolean {
    this.chunks.push(String(chunk));
    return true;
  }

  flushHeaders(): void {}

  end(chunk?: string): void {
    if (chunk !== undefined) this.chunks.push(String(chunk));
  }

  get body(): string {
    return this.chunks.join("");
  }
}

function summarizeJsonCompletion(body: string): Record<string, unknown> {
  const parsed = JSON.parse(body) as {
    object?: unknown;
    model?: unknown;
    choices?: Array<{ message?: { role?: unknown; content?: unknown }; finish_reason?: unknown }>;
  };
  return {
    object: parsed.object,
    model: parsed.model,
    assistantRole: parsed.choices?.[0]?.message?.role,
    assistantContent: parsed.choices?.[0]?.message?.content,
    finishReason: parsed.choices?.[0]?.finish_reason,
  };
}

const channel = new ApiServerChannel({ host: "127.0.0.1", port: 0, modelName: "fixture-model" });
(channel as unknown as { gateway: Gateway }).gateway = gateway;

async function post(content: string, sessionId?: string, streaming = false) {
  const headers: Record<string, string> = {
    host: "fixture.invalid",
    "content-type": "application/json",
  };
  if (sessionId) headers["x-hermes-session-id"] = sessionId;

  // Socket binding is unavailable in the sandbox (listen returns EPERM), so this
  // replays the exact /v1/chat/completions route with stream-compatible fakes.
  const request = Readable.from([Buffer.from(JSON.stringify({
    model: "fixture-model",
    messages: [{ role: "user", content }],
    stream: streaming,
  }))]) as Readable & { method?: string; url?: string; headers: Record<string, string> };
  request.method = "POST";
  request.url = "/v1/chat/completions";
  request.headers = headers;

  const response = new FakeResponse();
  await (channel as unknown as {
    handleRequest(req: unknown, res: FakeResponse): Promise<void>;
  }).handleRequest(request, response);
  return {
    status: response.statusCode,
    sessionHeader: response.headers.get("x-hermes-session-id") ?? null,
    body: response.body,
  };
}

const newAck = await post("/new");
const stateAfterNew = (channel as unknown as {
  mapper: { snapshot(): { activeByChatId: Record<string, string> } };
}).mapper.snapshot();
const continuation = await post("continuation without returned session header");
const stateAfterContinuation = (channel as unknown as {
  mapper: { snapshot(): { activeByChatId: Record<string, string> } };
}).mapper.snapshot();
const streamingNewAck = await post("/new", undefined, true);
const stateAfterStreamingNew = (channel as unknown as {
  mapper: { snapshot(): { activeByChatId: Record<string, string> } };
}).mapper.snapshot();

const mappedEntries = Object.entries(stateAfterNew.activeByChatId);
const continuationCall = calls.find((call) => call.message === "continuation without returned session header");
const mappedSessionKey = mappedEntries[0]?.[1] ?? "";
const continuationSessionKey = continuationCall?.sessionKey ?? "";

console.log(JSON.stringify({
  fixture: "api-server-route-handler-new-session-header",
  transport: "in-memory IncomingMessage/ServerResponse equivalent",
  endpoint: "POST /v1/chat/completions",
  input: {
    firstMessage: "/new",
    secondMessage: "continuation without returned session header",
    firstRequestSessionHeader: null,
    secondRequestSessionHeader: null,
  },
  newAck: {
    status: newAck.status,
    hasSessionHeader: newAck.sessionHeader !== null,
    bodySummary: summarizeJsonCompletion(newAck.body),
  },
  streamingNewAck: {
    status: streamingNewAck.status,
    hasSessionHeader: streamingNewAck.sessionHeader !== null,
    containsAck: streamingNewAck.body.includes("已创建新会话。"),
    containsDone: streamingNewAck.body.includes("data: [DONE]"),
  },
  continuation: {
    status: continuation.status,
    hasSessionHeader: continuation.sessionHeader !== null,
    bodySummary: summarizeJsonCompletion(continuation.body),
  },
  mapper: {
    entriesAfterNew: mappedEntries.length,
    entriesAfterContinuation: Object.keys(stateAfterContinuation.activeByChatId).length,
    entriesAfterStreamingNew: Object.keys(stateAfterStreamingNew.activeByChatId).length,
    newSessionKeyCreated: /^api_server:chat=api-.*:s_/.test(mappedSessionKey),
    continuationUsedMappedSession: continuationSessionKey === mappedSessionKey,
    continuationSessionKey: redact(continuationSessionKey),
    mappedSessionKey: redact(mappedSessionKey),
  },
  gatewayCalls: calls.map((call) => ({
    ...call,
    sessionKey: redact(call.sessionKey),
  })),
}));