What causes "Cloudflare sandbox bridge streaming command failed." in paperclipai/paperclip?

Treat this as a command failure and inspect bridge Worker logs for the real thrown error.

Cloudflare sandbox bridge streaming command failed.

Error message

Cloudflare sandbox bridge streaming command failed.

What it means

Thrown by `consumeExecuteEventStream` (bridge-client.ts:261) when the SSE stream emits an `error` event whose payload has no usable string `error` field. The bridge's streaming `/exec` endpoint signals command failure by emitting `event: error` with `{ error: "..." }`; if that string is missing/blank, this generic fallback message is used.

Source

Thrown at packages/plugins/sandbox-providers/cloudflare/src/bridge-client.ts:261

        const payload = JSON.parse(event.data) as { data?: unknown };
        const chunk = typeof payload.data === "string" ? payload.data : "";
        if (chunk) {
          await options.onOutput?.(event.event, chunk);
        }
        continue;
      }

      if (event.event === "complete") {
        result = JSON.parse(event.data) as CloudflareBridgeExecuteResponse;
        continue;
      }

      if (event.event === "error") {
        const payload = JSON.parse(event.data) as { error?: unknown };
        const message = typeof payload.error === "string" && payload.error.trim().length > 0
          ? payload.error
          : "Cloudflare sandbox bridge streaming command failed.";
        throw new Error(message);
      }
    }

    if (done) break;
  }

  if (result) return result;
  throw new Error("Cloudflare sandbox bridge streaming response ended without a completion event.");
}

export function createCloudflareBridgeClient(options: BridgeClientOptions) {
  const { config } = options;
  const apiPrefix = "/api/paperclip-sandbox/v1";

  return {
    health(extraHeaders?: BridgeClientHeaders): Promise<CloudflareBridgeHealthResponse> {
      return requestJson<CloudflareBridgeHealthResponse>(config, `${apiPrefix}/health`, { method: "GET" }, extraHeaders);
    },

View on GitHub (pinned to 67001ec6eb)

Solutions

Treat this as a command failure and inspect bridge Worker logs for the real thrown error.
Update the bridge deployment to a version that always emits a non-empty `error` string in SSE error events.
Retry the command non-streaming to get a structured result with stdout/stderr/exitCode for diagnostics.

Defensive patterns

Strategy: try-catch

Type guard

function isStreamingCommandFailure(e: unknown): boolean {
  return e instanceof Error && /streaming command failed/.test(e.message);
}

Try / catch

try {
  await client.execute(body, headers, { onOutput });
} catch (err) {
  if (isStreamingCommandFailure(err)) {
    // re-run non-streaming to capture exitCode/stdout/stderr for diagnosis
    const res = await client.execute(body, headers);
    log.warn("streaming failed; non-stream result", res);
  } else throw err;
}

Prevention

Keep bridge logs accessible — this error means the reason was lost in the SSE event.
Update the bridge so SSE error events always carry a non-empty error string.
Re-run non-streaming when the streaming reason is opaque.

When it happens

Trigger: A streaming exec command fails inside the bridge and the Worker emits an SSE `error` event, but the JSON payload's `error` field is absent, non-string, or whitespace-only — so the client cannot surface the bridge's actual failure reason.

Common situations: An uncaught throw inside the bridge's streaming exec handler whose error message was lost (e.g. `String(error)` produced empty), or a bridge version that emits malformed error events. The underlying command failed, but the reason is opaque.

Related errors

AI-assisted analysis of paperclipai/paperclip@67001ec6eb (2026-08-12). Data as JSON: /api/errors/a67d4ddb19d80c80. Report an issue: GitHub.