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XBSTACK continuously documents practical AI Agent, MCP, LangGraph and Workflow engineering, alongside useful developer tools, long-term research and outdoor field notes.

MCP LangGraph AI Agent Workflow AI Finance

AI Engineering Topics

AI Agent

Architecture, tool use, memory, RAG, evaluation, permissions and runtime governance.

Agent architecture and runtime →Tool authorization →Memory / RAG →

MCP

Servers, transports, OAuth, permissions, security and protocol troubleshooting.

MCP vs Function Calling →Streamable HTTP →JSON-RPC debugging →

LangGraph

State, checkpoints, HITL, failure recovery, concurrency and observability.

State isolation →HITL approval →Failure recovery →

Workflow Automation

n8n, self-hosting, webhooks, queues, retries, idempotency and cost governance.

Self-hosted n8n →Error handling and cost →Queue Mode →

Products & Tools

All products & tools →

AI Finance

Analyze public financial reports and company fundamentals.

Open →

Lunest

Sleep and recovery product for iOS and Android.

Open →

Latest Publications

Archive →Newsletter →

OpenAI Zero Data Retention for AI Agents: Responses API, MCP and Data Boundaries

OpenAI Zero Data Retention does not make an AI agent stack stateless. This guide maps ZDR across Responses API, remote MCP, prompt caching, background mode and Data Residency.

AI Engineering08/20/2026

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n8n 2.35.3 $json Array Methods Return null: Reproduction and Workaround

In n8n 2.35.3 Edit Fields, $json.data.sort(), splice(), fill() and copyWithin() return null. Compare official 2.34.5 vs 2.35.3 Docker runs and tested copy-first workarounds.

AI Engineering08/19/2026

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n8n HTTP Request Returns _readableState Instead of JSON: Raw Body Response Stream Fix

n8n HTTP Request can return _readableState instead of JSON with Raw Body + explicit JSON Response. See the four-case repro, source path and tested workarounds.

AI Engineering08/18/2026

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Guizhou Keeps Getting More Popular: Why First-Time Visitors Should Skip a Few Stops

A personal view of why Guizhou attracts travelers, and why first-time visitors may enjoy it more by choosing fewer stops and leaving room for weather, local life and the mountains.

Lens08/18/2026

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What Is DeepSeek V4-Pro-0813? API Pricing, Setup, and DeepSeek Harness Guide

DeepSeek V4-Pro-0813 explained: API pricing, 1M context, 384K output, concurrency, OpenAI/Anthropic setup, and DeepSeek Harness installation.

AI Engineering08/15/2026

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AI SDK streamObject() Hangs After Errors: Why result.object Can Stay Pending

AI SDK 7.0.66 repro: streamObject can leave result.object and related promises pending after provider errors even when fullStream is consumed. Includes a tested failure fence.