AI Engineering Knowledge Base

From architecture choices to production troubleshooting, this hub organizes real AI Agent, MCP, LangGraph, Workflow and on-device AI problems. Each topic aims to provide reproducible methods, constraints and a concrete next step.

MCP LangGraph AI Agent Agent Security Workflow RAG Evaluation

XBSTACK organizes AI engineering by problem domain: Agents handle dynamic decisions and tool use, MCP standardizes model-to-tool connections, LangGraph manages stateful orchestration and recovery, and Workflow handles deterministic business automation. Complex systems can combine them, but not every problem belongs in one framework.

Topics

AI Agent

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

Agent architecture →Tool authorization →Memory architecture →

Agent Security Infrastructure

Identity, authorization, approvals, sandboxing, MCP security, ZDR, audit and incident response for production agents.

AI Agent Security →Tool Authorization →OpenAI ZDR data boundary →

MCP

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

MCP -32700 / JSON-RPC Parse Error →MCP vs Function Calling →Streamable HTTP →

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 →

AI Tools Lab

Model and AI-tool tests based on real projects and explicit tasks.

ChatGPT Work vs Chat vs Codex →Model Updates →GPT-5.6 real project test →

Local AI

iPhone, Android, Core ML, ONNX, llama.cpp, model size, heat, performance and privacy.

Local AI →On-device integration →Mobile practice →

Guides & Practice

AI Agent Full Guide: From Architecture to Production Governance

Build the system boundary across agents, workflows, memory, RAG, tool use and production governance.

Read →

MCP vs Function Calling: Real Project Selection

Compare protocol boundaries, permissions, tool integration and client reuse.

Read →

LangGraph State Isolation in Practice

Design thread_id, session_id and user_id boundaries and persistence.

Read →

Self-hosted n8n AI Workflows

Docker, VPS, NAS, self-hosting and production operations.

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AI Agent Tool Authorization Policy Gate

Authorization, approval, rejection and auditing before high-risk tool calls.

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GPT-5.6 Real Project Test

Test whether model improvements materially change real development workflows.

Read →

Latest

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.

08/20/2026

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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.

08/19/2026

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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.

08/18/2026

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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.

08/15/2026

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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.

08/15/2026

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n8n 2.33.7 Distroless ARM64 GLIBC_PRIVATE Error: Reproduction and Workaround

n8n 2.33.7 distroless on ARM64 exits 127 with __tunable_is_initialized / GLIBC_PRIVATE. Compare 2.26.9, the Dockerfile ABI boundary, and a verified rollback workaround.

08/11/2026

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Google ADK Resume Bugs: state_delta Loss and the 2.7.0 A2A HITL Regression

Google ADK state_delta not applied: reproduce the 2.6.2 state-only resume loss and compare the 2.6.1 vs 2.7.0 A2A HITL message-conversion regression.

08/09/2026

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n8n 2.33.4 Baserow Workflows Fail to Activate: Fix 'Could not resolve parameter dependencies'

n8n Could not resolve parameter dependencies after 2.33.4? This Baserow repro compares 2.32.7 vs 2.33.4, isolates the timezone regression, and gives safe rollback steps.

08/07/2026

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Zhuzhiliao: What It Is and How I Turned It into a Mobile Web Game

Zhuzhiliao is a traditional Chinese bamboo whirring toy. Play XBSTACK's browser version and see how it was rebuilt with touch controls, motion sensors and Canvas.

08/06/2026

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OpenAI Responses API: Why Stream Abort Causes No tool call found for function call output

A function_call can be visible before it is durable in Conversation state. This guide explains the 400 No tool call found error, reconciliation, idempotency, and safe recovery.

08/05/2026

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