标签：#ha

Most portfolios have a boring "About Me" paragraph. I replaced mine with something you can talk to — an AI terminal that answers questions about me, pulls my live GitHub activity, and remembers the conversation. You can try it right now on my portfolio: rehbarkhan.in . I'm Rehbar Khan , a Full Stack & Gen-AI developer, and in this post I'll break down exactly how it works — the RAG pipeline, the LangGraph agent, the memory layer, and how I wired in real GitHub data with MCP. No fluff, just the architecture. The problem I wanted a portfolio assistant that could: Answer questions about my background accurately — no hallucinated jobs or fake projects. Fetch live data (my latest GitHub activity), not a stale snapshot. Remember the conversation across messages. Stream responses token-by-token like a real terminal. That rules out "just prompt an LLM." You need retrieval for grounding, tools for live data, and state for memory. Here's the stack I landed on. Architecture at a glance Next.js 16 chat UI ──► FastAPI (streaming) ──► LangGraph agent ├── RAG retriever → pgvector (Neon Postgres) ├── GitHub MCP tool → live GitHub data └── Redis checkpointer → conversation memory Frontend: Next.js 16 (App Router, TypeScript) — a streaming terminal UI. Backend: FastAPI with streaming responses. Orchestration: LangGraph ( StateGraph , ToolNode , tools_condition ). LLM: OpenAI gpt-4o-mini . Retrieval: text-embedding-3-small → pgvector on Neon Postgres. Memory: Redis checkpointer for per-session history. Live data: GitHub via the Model Context Protocol (MCP) . 1. The RAG pipeline Everything the bot knows about me lives in a single reference.txt . I chunk it, embed it, and store it in Postgres with pgvector: from langchain_text_splitters import RecursiveCharacterTextSplitter from langchain_openai import OpenAIEmbeddings from langchain_postgres import PGVector splitter = RecursiveCharacterTextSplitter ( chunk_size = 500 , chunk_overlap = 80 ) chunks = splitter . split_text ( open ( " refe

Monitoring is expensive and labor intensive. But it helps public health officials stop outbreaks.

This is a submission for DEV's Summer Bug Smash: Smash Stories powered by Sentry . There is a version of this story where I walk you through the technical challenges in a clean, detached voice. Structured. Professional. Composed. This is not that version. Seven months. A hundred pages of documentation written alongside the code, not after it. A live system serving rural clinics in Delta State, Nigeria. And three bugs so specific and so cruel that each one felt designed to find the exact gap between what I thought I knew and what I actually knew. The Delta Health Information and Appointment Booking System was my final year project at the University of Port Harcourt. That sentence makes it sound smaller than it was. This was a real system for real clinics, serving patients who travel for hours to reach a healthcare facility only to find the clinic is full, the doctor is not in, or nobody told them their appointment was cancelled. These are not hypothetical users. These are people whose access to healthcare depends on whether the software works. That is a different kind of pressure than getting a good grade. And it did not start at deployment. Before a single line of code was written, I had to pitch the entire concept to my university supervisor, the Head of Department, the Faculty Dean, and an external examiner. The system had to be defensible not just technically but practically. It had to demonstrate that it solved a real problem that real people in Delta State were actually facing. I was presenting to people with decades of experience who would ask questions I had not thought of yet. That kind of scrutiny either sharpens you or breaks you. I chose to let it sharpen me. The stack was React.js, Node.js, PHP with Laravel, MySQL, AWS, and Docker. Communication channels included SMS gateways, WhatsApp Business API, and USSD because not every patient in rural Delta State has a smartphone. The system had to run on 2G connections, on entry-level Android phones with 2GB RAM

Written by Marlowe Finch, archival bloodhound at Bitcoin Institute. Bitcoin has been decentralized and trustless since block zero. No CEO, no committee, no kill switch, no single person who can rewrite the rules. That's the pitch. It's why the whitepaper still gets quoted like scripture. Block 74638 does not agree with the pitch. What actually shipped in that block On August 15, 2010, a transaction landed in the Bitcoin blockchain with two outputs. Each one paid out 92,233,720,368.54277039 BTC . Combined: over 184 billion BTC — roughly nine thousand times the 21 million BTC that will ever exist, created in a single transaction. The validation code, CheckTransaction() , checked that each individual output was non-negative. It never checked whether the sum of the outputs overflowed. Two values chosen just under INT64_MAX, added together, wrapped around to a negative number in signed 64-bit arithmetic. A 0.5 BTC input, compared against that negative sum, satisfied the "input covers output" check. The transaction validated. The block got mined. Every rule the network was running said this was fine. That's CVE-2010-5139. It is also, by any dollar value you want to apply, the most expensive missing bounds-check ever shipped to production. So who hand-builds a transaction engineered to overflow a signed 64-bit integer, and what does a currency with a hard 21-million-coin cap do when someone mints nine thousand times that in one block? The archive's full account of the incident lays it out block by block . The receipts 18:08 UTC, August 15 — Jeff Garzik opens a BitcoinTalk thread titled "Strange block 74638", pastes the raw block dump, and closes with one question: "92233720368.54277039 BTC? Is that UINT64_MAX, I wonder?" 20:38 UTC — Satoshi Nakamoto, to the bitcoin-list mailing list, network-wide: "*** WARNING *** We are investigating a problem. DO NOT TRUST ANY TRANSACTIONS THAT HAPPENED AFTER 15.08.2010 17:05 UTC (block 74638) until the issue is resolved." 20:39 UTC — Ga

When you develop a game at the beginning of your journey, you quickly notice that the environment is very static. To change that, let’s create some oscillations and move our platforms. We will use methods like Vector3.Lerp and Mathf.PingPong . using UnityEngine ; public class Oscillate : MonoBehaviour { [ SerializeField ] private Vector3 movementVector ; [ SerializeField ] private float speed ; private Vector3 _startPosition ; private Vector3 _endPosition ; private float _movementFactor ; private void Start () { _startPosition = transform . position ; _endPosition = transform . position + movementVector ; } private void Update () { _movementFactor = Mathf . PingPong ( Time . time * speed , 1f ); transform . position = Vector3 . Lerp ( _startPosition , _endPosition , _movementFactor ); } } First, we add movementVector and speed to inspector. movementVector receives the direction, and we tell it how far object must move. speed defines how fast objects move _ startPosition simply gets the starting coordinates in Start() with transform.position , and _ endPosition is the sum of the _ startPosition and movementVector . Now _ movementFactor is different. It defines the progress of the movement. Imagine it as a loading bar from 1% to 100%. In Update() method, we constantly calculate it every frame using Mathf.PingPong _movementFactor = Mathf.PingPong(Time.time * speed, 1f); So what is going on here, Mathf.PingPong does what you would imagine. Value goes back and forth. 1f is our length, so in Update() every frame _ movementFactor is getting updated from 0.0, 0.1, 0.2… up to 1.0, when the value is 1.0, it goes back to 0.0 in the same way. And since it’s in Update() this is an endless cycle. transform.position = Vector3.Lerp(_startPosition, _endPosition, _movementFactor); Now this is where magic happens. Lerp (Linear Interpolation) takes start position, end position and a “loading” bar. Why we did exactly 1f in PingPong is perfectly described in the official documentation: a