@langchain/langgraph-sdk/dist/utils/stream.cjs.map

Client library for interacting with the LangGraph API

{"version":3,"file":"stream.cjs","names":["isNetworkError","reconnectDelayMs"],"sources":["../../src/utils/stream.ts"],"sourcesContent":["import { isNetworkError } from \"./error.js\";\nimport {\n  DEFAULT_MAX_RECONNECT_ATTEMPTS,\n  reconnectDelayMs,\n} from \"./reconnect.js\";\n\n// in this case don't quite match.\ntype IterableReadableStreamInterface<T> = ReadableStream<T> & AsyncIterable<T>;\n\n/**\n * Options for streaming with automatic retry logic.\n */\nexport interface StreamWithRetryOptions {\n  /**\n   * Maximum number of reconnection attempts. Default is\n   * {@link DEFAULT_MAX_RECONNECT_ATTEMPTS}.\n   */\n  maxRetries?: number;\n\n  /**\n   * AbortSignal to cancel the stream.\n   */\n  signal?: AbortSignal;\n\n  /**\n   * Callback invoked when a reconnection attempt is made.\n   */\n  onReconnect?: (options: {\n    attempt: number;\n    lastEventId?: string;\n    cause: unknown;\n  }) => void;\n}\n\n/**\n * Parameters for making a stream request\n */\nexport interface StreamRequestParams {\n  /**\n   * Last event ID to resume from, if available\n   */\n  lastEventId?: string;\n\n  /**\n   * Optional reconnection path from the Location header\n   */\n  reconnectPath?: string;\n}\n\n/**\n * Error thrown when maximum reconnection attempts are exceeded.\n */\nexport class MaxReconnectAttemptsError extends Error {\n  constructor(maxAttempts: number, cause: unknown) {\n    super(`Exceeded maximum SSE reconnection attempts (${maxAttempts})`);\n    this.name = \"MaxReconnectAttemptsError\";\n    this.cause = cause;\n  }\n}\n\n/**\n * Error injected into the stream by {@link idleReconnectStream} when no lines\n * arrive within the active idle window. Surfacing this during the read is what\n * lets the reconnect loops in `streamWithRetry` and the protocol SSE transport\n * recover from a half-open socket — one that was silently dropped (e.g. a hard\n * pod kill on a platform revision rollover) without a TCP FIN/RST, so neither\n * a `done` nor a thrown network error ever arrives.\n */\nexport class StreamIdleTimeoutError extends Error {\n  readonly idleTimeoutMs: number;\n\n  constructor(idleTimeoutMs: number) {\n    super(\n      `No SSE bytes received for ${idleTimeoutMs}ms; assuming the connection is half-open and reconnecting.`\n    );\n    this.name = \"StreamIdleTimeoutError\";\n    this.idleTimeoutMs = idleTimeoutMs;\n  }\n}\n\n/** `\":\"` — first byte of an SSE comment / keep-alive line. */\nconst SSE_COMMENT_BYTE = 0x3a;\n\n/**\n * How {@link idleReconnectStream} decides when the connection is idle.\n *\n * - A `number` is a fixed idle window in milliseconds: the watchdog arms\n *   immediately (even before the first byte) and trips after that long with no\n *   activity. Use when you know your server's behaviour and want guaranteed\n *   coverage from t=0; it does not depend on heartbeats.\n * - `\"auto\"` is heartbeat-adaptive: the watchdog stays dormant until it has\n *   observed the server's SSE keep-alive comments (e.g. LangGraph Platform's\n *   `: heartbeat` every ~5s), then arms with a window derived from the\n *   observed cadence. On a server that never sends heartbeats it never arms,\n *   so it can't false-fire during a legitimately quiet period.\n */\nexport type IdleReconnectMode = number | \"auto\";\n\n/**\n * Default idle-reconnect policy for SSE streams. Heartbeat-adaptive\n * `\"auto\"` stays dormant unless the server emits keep-alive heartbeats.\n * Pass `0` to disable.\n */\nexport const DEFAULT_IDLE_RECONNECT: IdleReconnectMode = \"auto\";\n\nexport interface IdleReconnectStreamOptions {\n  /** Fixed timeout (ms) or `\"auto\"` heartbeat-adaptive. */\n  mode: IdleReconnectMode;\n  /** `\"auto\"`: multiplier applied to the observed heartbeat interval. Default 3. */\n  timeoutFactor?: number;\n  /** `\"auto\"`: lower clamp for the derived timeout (ms). Default 6000. */\n  minTimeoutMs?: number;\n  /** `\"auto\"`: upper clamp for the derived timeout (ms). Default 30000. */\n  maxTimeoutMs?: number;\n  /** Fired immediately before the stream is errored, for logging/metrics. */\n  onIdle?: (info: { timeoutMs: number; source: \"fixed\" | \"heartbeat\" }) => void;\n}\n\n/**\n * A pass-through {@link TransformStream} that errors the stream when it goes\n * idle, so the surrounding reconnect logic can recover a half-open socket.\n *\n * MUST sit on the *line* stream — i.e. after\n * {@link import(\"./sse.js\").BytesLineDecoder} but before\n * {@link import(\"./sse.js\").SSEDecoder} (which discards `:` comment lines).\n * Operating at the line level lets the watchdog both (a) reset on any line\n * (data *or* heartbeat = liveness) and (b) recognise heartbeat comment lines\n * to drive `\"auto\"` mode.\n *\n * In `\"auto\"` mode the watchdog is intentionally dormant until it has seen at\n * least two heartbeats (so it can measure the cadence). This means a socket\n * that dies inside the first heartbeat interval won't be caught until a\n * heartbeat would have been due — an acceptable trade for never false-firing\n * on heartbeat-less servers. Pass a fixed `number` if you need coverage from\n * the very first byte.\n */\nexport function idleReconnectStream(\n  options: IdleReconnectStreamOptions\n): TransformStream<Uint8Array, Uint8Array> {\n  const factor = options.timeoutFactor ?? 3;\n  const minTimeoutMs = options.minTimeoutMs ?? 6_000;\n  const maxTimeoutMs = options.maxTimeoutMs ?? 30_000;\n  const fixedTimeoutMs = typeof options.mode === \"number\" ? options.mode : null;\n\n  let timer: ReturnType<typeof setTimeout> | undefined;\n  let controllerRef: TransformStreamDefaultController<Uint8Array> | undefined;\n\n  // `\"auto\"` cadence inference.\n  let lastHeartbeatAt: number | undefined;\n  // The active idle window: the fixed value, or (auto) the heartbeat-derived\n  // value once known. `null` means \"not armed yet\".\n  let derivedTimeoutMs: number | null = fixedTimeoutMs;\n\n  const clear = () => {\n    if (timer != null) {\n      clearTimeout(timer);\n      timer = undefined;\n    }\n  };\n\n  const arm = () => {\n    clear();\n    const timeoutMs = derivedTimeoutMs;\n    if (timeoutMs == null || timeoutMs <= 0) return;\n    timer = setTimeout(() => {\n      options.onIdle?.({\n        timeoutMs,\n        source: fixedTimeoutMs != null ? \"fixed\" : \"heartbeat\",\n      });\n      try {\n        controllerRef?.error(new StreamIdleTimeoutError(timeoutMs));\n      } catch {\n        // Stream already closed/errored/cancelled — nothing to abort.\n      }\n    }, timeoutMs);\n    // Don't let the watchdog by itself keep a Node process alive.\n    (timer as unknown as { unref?: () => void }).unref?.();\n  };\n\n  const noteHeartbeat = () => {\n    if (fixedTimeoutMs != null) return; // cadence irrelevant in fixed mode\n    const now = Date.now();\n    if (lastHeartbeatAt != null) {\n      const interval = now - lastHeartbeatAt;\n      if (interval > 0) {\n        const candidate = Math.min(\n          Math.max(interval * factor, minTimeoutMs),\n          maxTimeoutMs\n        );\n        // Keep the most conservative (largest) window observed so far.\n        derivedTimeoutMs =\n          derivedTimeoutMs == null\n            ? candidate\n            : Math.max(derivedTimeoutMs, candidate);\n      }\n    }\n    lastHeartbeatAt = now;\n  };\n\n  return new TransformStream<Uint8Array, Uint8Array>({\n    start(controller) {\n      controllerRef = controller;\n      // Fixed mode arms eagerly (also catches pre-first-byte silence). Auto\n      // mode waits until a cadence is established in `transform`.\n      arm();\n    },\n    transform(line, controller) {\n      // A line beginning with \":\" is an SSE comment / keep-alive heartbeat.\n      if (line.length > 0 && line[0] === SSE_COMMENT_BYTE) {\n        noteHeartbeat();\n      }\n      // Any line is liveness — (re)arm the idle timer.\n      arm();\n      controller.enqueue(line);\n    },\n    flush() {\n      clear();\n    },\n  });\n}\n\n/**\n * Stream with automatic retry logic for SSE connections.\n * Implements reconnection behavior similar to the Python SDK.\n *\n * @param makeRequest Function to make requests. When `params` is undefined/empty, it's the initial request.\n *                    When `params.reconnectPath` is provided, it's a reconnection request.\n * @param options Configuration options\n * @returns AsyncGenerator yielding stream events\n */\nexport async function* streamWithRetry<T extends { id?: string }>(\n  makeRequest: (params?: StreamRequestParams) => Promise<{\n    response: Response;\n    stream: ReadableStream<T>;\n  }>,\n  options: StreamWithRetryOptions = {}\n): AsyncGenerator<T> {\n  const maxRetries = options.maxRetries ?? DEFAULT_MAX_RECONNECT_ATTEMPTS;\n  let attempt = 0;\n  let lastEventId: string | undefined;\n  let reconnectPath: string | undefined;\n\n  while (true) {\n    let shouldRetry = false;\n    let lastError: unknown;\n    let reader: ReadableStreamDefaultReader<T> | undefined;\n\n    try {\n      // Check if aborted before making request\n      if (options.signal?.aborted) return;\n\n      // Make request - initial if no reconnect path, reconnect otherwise\n      const { response, stream } = await makeRequest(\n        reconnectPath ? { lastEventId, reconnectPath } : undefined\n      );\n\n      // Check for Location header (server-provided reconnection path)\n      const locationHeader = response.headers.get(\"location\");\n      if (locationHeader) {\n        reconnectPath = locationHeader;\n      }\n\n      // Verify content type\n      const contentType = response.headers.get(\"content-type\")?.split(\";\")[0];\n      if (contentType && !contentType.includes(\"text/event-stream\")) {\n 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} else {\n          throw error;\n        }\n      } finally {\n        if (reader) {\n          try {\n            reader.releaseLock();\n          } catch {\n            // Ignore errors when releasing lock\n          }\n        }\n      }\n    } catch (error) {\n      lastError = error;\n\n      // Only retry if we have reconnection capability and it's a network error\n      if (isNetworkError(error) && reconnectPath && !options.signal?.aborted) {\n        shouldRetry = true;\n      } else {\n        throw error;\n      }\n    }\n\n    if (shouldRetry) {\n      attempt += 1;\n      if (attempt > maxRetries) {\n        throw new MaxReconnectAttemptsError(maxRetries, lastError);\n      }\n\n      // Notify about reconnection attempt\n      options.onReconnect?.({ attempt, lastEventId, cause: lastError });\n\n      // Exponential backoff with jitter (shared with protocol transports).\n      const delay = reconnectDelayMs(attempt);\n\n      await new Promise((resolve) => {\n        setTimeout(resolve, delay);\n      });\n\n      continue;\n    }\n\n    // Successfully completed\n    break;\n  }\n}\n\n/*\n * Support async iterator syntax for ReadableStreams in all environments.\n * Source: https://github.com/MattiasBuelens/web-streams-polyfill/pull/122#issuecomment-1627354490\n */\nexport class IterableReadableStream<T>\n  extends ReadableStream<T>\n  implements IterableReadableStreamInterface<T>\n{\n  public reader: ReadableStreamDefaultReader<T>;\n\n  ensureReader() {\n    if (!this.reader) {\n      this.reader = this.getReader();\n    }\n  }\n\n  async next(): Promise<IteratorResult<T>> {\n    this.ensureReader();\n    try {\n      const result = await this.reader.read();\n      if (result.done) {\n        this.reader.releaseLock(); // release lock when stream becomes closed\n        return {\n          done: true,\n          value: undefined,\n        };\n      } else {\n        return {\n          done: false,\n          value: result.value,\n        };\n      }\n    } catch (e) {\n      this.reader.releaseLock(); // release lock when stream becomes errored\n      throw e;\n    }\n  }\n\n  async return(): Promise<IteratorResult<T>> {\n    this.ensureReader();\n    // If wrapped in a Node stream, cancel is already called.\n    if (this.locked) {\n      const cancelPromise = this.reader.cancel(); // cancel first, but don't await yet\n      this.reader.releaseLock(); // release lock first\n      await cancelPromise; // now await it\n    }\n    return { done: true, value: undefined };\n  }\n\n  // eslint-disable-next-line @typescript-eslint/no-explicit-any\n  async throw(e: any): Promise<IteratorResult<T>> {\n    this.ensureReader();\n    if (this.locked) {\n      const cancelPromise = this.reader.cancel(); // cancel first, but don't await yet\n      this.reader.releaseLock(); // release lock first\n      await cancelPromise; // now await it\n    }\n    throw e;\n  }\n\n  // eslint-disable-next-line @typescript-eslint/ban-ts-comment\n  // @ts-ignore Not present in Node 18 types, required in latest Node 22\n  async [Symbol.asyncDispose]() {\n    await this.return();\n  }\n\n  [Symbol.asyncIterator]() {\n    return this;\n  }\n\n  static fromReadableStream<T>(stream: ReadableStream<T>) {\n    // From https://developer.mozilla.org/en-US/docs/Web/API/Streams_API/Using_readable_streams#reading_the_stream\n    const reader = stream.getReader();\n    return new IterableReadableStream<T>({\n      start(controller) {\n        return pump();\n        function pump(): Promise<T | undefined> {\n          return reader.read().then(({ done, value }) => {\n            // When no more data needs to be consumed, close the stream\n            if (done) {\n              controller.close();\n              return;\n            }\n            // Enqueue the next data chunk into our target stream\n            controller.enqueue(value);\n            return pump();\n          });\n        }\n      },\n      cancel() {\n        reader.releaseLock();\n      },\n    });\n  }\n\n  static fromAsyncGenerator<T>(generator: AsyncGenerator<T>) {\n    return new IterableReadableStream<T>({\n      async pull(controller) {\n        const { value, done } = await generator.next();\n        // When no more data needs to be consumed, close the stream\n        if (done) {\n          controller.close();\n        }\n        // Fix: `else if (value)` will hang the streaming when nullish value (e.g. empty string) is pulled\n        controller.enqueue(value);\n      },\n      async cancel(reason) {\n        await generator.return(reason);\n      },\n    });\n  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