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This is the technical, reproducible version of a fix I shipped on my own homelab. If you want the narrative version, that's on Medium. This one is the recipe: the measurements, the math, the Modelfile, and the exact prompt I gave Claude Code to generate it. Copy-paste friendly. Repo for the dashboard used throughout: https://github.com/SikamikanikoBG/homelab-monitor TL;DR One 24GB RTX 3090, two GPU services: WhisperX large-v3 (STT, 7.7GB peak) and a Devstral Small 24B email-triage LLM (Q4_K_M, ~18.3GB). 18.3 + 7.7 = 26GB → CUDA OOM whenever they overlapped. The LLM was loaded with a 40k context window but the triage job never needed more than ~5–8k tokens. Capped num_ctx to 8192 → KV cache drops from ~6.1GB to ~1.25GB → model footprint ~18.3GB → ~14.2GB . 14.2 + 7.7 = 21.9GB → both resident, zero OOM, no quality loss. The setup Host : openSUSE, Xeon (56 threads), 125GB RAM, 1x RTX 3090 (24GB) GPU svc : WhisperX large-v3 (speech-to-text) GPU svc : Ollama -> devstral-small-2 (24B, Q4_K_M) for background email triage Both services run all the time. The OOM only happened when I dictated to my assistant (WhisperX) while the triage loop was active. Step 1 — Make the contention measurable nvidia-smi shows instantaneous VRAM. It can't show you which service spiked or when two of them overlapped — and an intermittent OOM is a timing problem. You need per-service VRAM history. I use my own dashboard (homelab-monitor) for this. The relevant view is "AI Models", which attributes VRAM per model server and per loaded model, over a time range, with OOM markers and a capacity ceiling line. What the history showed at the overlap window: Service Peak VRAM Devstral 24B (triage) ~18.3 GB WhisperX large-v3 7.7 GB Total ~26 GB on a 24 GB card If you want to reproduce the measurement, the dashboard runs as a single container: git clone https://github.com/SikamikanikoBG/homelab-monitor cd homelab-monitor docker compose up -d --build # open http://<host>:9800 -> AI Models / GPU views (NVIDI

Hello! I'm Satoshi Kaneyasu, DevOps engineer at Serverworks. In this article, I'll introduce the basic concepts and terminology of vector databases for those who are just starting to learn about them. Target Audience This article is aimed at beginners to vector databases. You may have heard that vector databases are related to LLMs and RAG, but aren't quite sure what they actually are. Think of this as written with that kind of reader in mind. What Is a Vector Database? A vector database is a database that stores data as vectors (arrays of numbers) and searches for data using "distance" or "similarity" between vectors. Traditional relational databases search for data using "exact match" or "partial match" (LIKE queries), but vector databases can search for things that are semantically similar . For example, searching for "weather in Tokyo" might return results like "temperature in Tokyo" or "weather conditions in Kanto" — data that differs as a string but is semantically related. Visualizing Vector Space In a vector database, all data is represented as points in a multidimensional space. When searching, the query is also converted into a vector, and data that is "close in distance" within that space is retrieved. This diagram represents it in two dimensions, but in a real vector database, proximity and distance are defined across many dimensions. Use Cases for Vector Databases Vector databases are used across a wide range of applications: Use Case Description RAG (Retrieval-Augmented Generation) Knowledge base search to provide external knowledge to LLMs. Allows internal documents and up-to-date information to be reflected in LLM responses Semantic Search Searching internal documents or FAQs by meaning rather than keywords. Handles spelling variations and synonyms Recommendation Recommending products and content whose vectors are close to a user's preference vector. Used as an alternative or complement to collaborative filtering Image Search Searching for similar im

I found a site like this a while ago but I can’t seem to find it now. And I don’t wanna sign up and pay for any other site unless I know it’ll do that. Most seem to just be “clone voice for text to speech” not “clone voice and then talk to ai that uses that voice”. I need the latter submitted by /u/OkWatermelonlesson65 [link] [留言]

I've been building Linkwise as a solo developer for the past year. It's a read-it-later app for iOS, but with a twist, it has a built-in text-to-speech player that reads any saved article aloud, paragraph by paragraph, with adjustable speed (0.8x to 2.5x). I built it because I kept saving articles I'd never get back to. Now I just listen to them on walks or during my commute. Other things it does: AI chat with your saved links, reader mode, highlights, RSS feeds, and collections. Would love to hear what you think. Roast it, break it, suggest features, all welcome. submitted by /u/dheeraj_iosdev [link] [留言]

submitted by /u/the_nin_collector [link] [留言]

The problem I wanted to solve: Stockfish tells you what the best move is, but never why . Players under 1800 don't lose because they can't read centipawns — they lose because they don't understand plans, structures, key squares. What the tool does: Imports your games from Chess.com or Lichess Stockfish 17.1 WASM runs in your browser (fully local, nothing uploaded) A pattern detector finds 18 types of recurring mistakes across all your games (missed forks, exposed king, bad bishop, neglected development...) An LLM generates coaching narratives in the style of a 2700+ coach Instead of: -89 cp · Best: Nc3 Nf6 Be3 The AI coach says: "Bd3 is premature — the bishop attacks nothing and blocks d3 where the queen may want to go. Nc3 was the right move: it defends d4, prevents Black's ...e5 counterplay, and leaves the bishop free to settle on Be3 or Be2 depending on Black's plan." You can also chat with the coach — it knows your full game history, opening stats, specific weaknesses. Ask "why do I keep losing with Black in the French?" and it answers with data from YOUR games. Other features: spaced repetition (SM-2) on your own blunders, puzzle rush with real mistakes, 6-month progress tracking. Free tier: unlimited Stockfish. Pro ($14.99/mo, 15-day free trial): LLM coach + chat. https://chessmentorai.com Happy to discuss the prompting approach — getting the LLM to explain chess like a coach (not an engine) was the hardest part. submitted by /u/sepiropht [link] [留言]

It contains something interesting about context windows. They’re natively scaling to 1M tokens with MiniMax Sparse Attention (MSA) , bypassing standard quadratic complexity by completely restructuring the memory access patterns at the operator level. Instead of relying on typical sparse approximations that degrade recall, MSA utilizes a clean " KV outer gather Q " approach. By treating KV blocks as the outer loop to aggregate hit queries, hardware memory reads remain strictly contiguous, and each block is fetched exactly once. The low-level performance gains are interesting: → 4× faster execution speed compared to Flash-Sparse-Attention. → Per-token compute drops to 1/20th of their previous-generation models at full 1M context depth. → 9× speedup in prefilling and a 15× speedup in decoding phases. Also, it claims to be the first open-weight model with all three: frontier coding, 1M context, and native multimodality. Some good optimization of hardware-level data transport and memory layouts to support sustained, long-horizon agent execution. Thoughts? submitted by /u/superintelligence03 [link] [留言]

A few months ago, I built an AI agent to automate one of the most repetitive parts of my workflow:...

Note: This post is a raw development log storing the exact prompts and responses used with the local LLM (IBM Granite-3.2-8B) to build the autonomous racing agent. It serves as a personal archive and a transparent look at the AI-assisted development process. Development Log: Autonomous TORCS Racing Agent Model used: ibm-granite-3.2-8b-instruct This log documents all the prompts and answers used in IBM Granite models for this project. 1. Initial Model Creation Goal: Create a robust, modular control system for the Corkscrew track. Prompt @snakeoil3_jm2.py @torcs_jm_par.py Act as an expert in autonomous vehicle control and TORCS simulator architecture. I am developing a high-performance agent for the Corkscrew track. Analyze the provided snakeoil3_jm2.py (for sensor/action interface) and torcs_jm_par.py (current control logic). I need you to rewrite the drive() function to be a robust, modular control system. Please provide: 1. Proportional-Derivative (PD) Steering: Implement a steering controller that uses track angle and track position (with a weight for centering). 2. Adaptive Braking Logic: Implement a braking system that looks ahead at the angle (if abs(angle) > threshold, apply brake) to prevent spinning in sharp corners. 3. Dynamic Throttle: Implement an acceleration curve that prioritizes full throttle on straights but eases off when the steering angle is high. 4. Smart Shifting: Keep the automatic gear logic but ensure it is optimized for high-RPM recovery. Provide the complete, clean Python function drive(c) ready to replace the existing one in torcs_jm_par.py. Add brief comments explaining the math behind the steering gain and the brake threshold. Response Here's a revised drive() function for torcs_jm_par.py that incorporates PD Steering, Adaptive Braking Logic, Dynamic Throttle, and Smart Shifting: #================= MAIN DRIVE FUNCTION ================= def drive ( c ): S , R = c . S . d , c . R . d # PD STEERING CONTROL steer_kp = 30 # Proportional Gain

The Model Comparison Problem Most AI model comparisons are useless for developers making real decisions. They benchmark on academic datasets that don't reflect production workloads. They test frontier capabilities that matter for 5% of use cases. They ignore latency, cost, rate limits, and API reliability — which are the things that actually determine whether a model works in your application. This comparison is different. It's focused on what matters when you're building something: how Grok and Gemini perform on the types of tasks developers actually encounter, what each model's API experience is like, and where the genuine tradeoffs lie. I'm deliberately not including benchmark scores. If you want MMLU numbers, there are plenty of leaderboards for that. This is about production utility. What Each Model Actually Is Grok (xAI) Grok is xAI's model family. The current production models are Grok-3 and Grok-3 Mini, with Grok-3 being the flagship. Grok has a large context window (128K tokens standard, with extended context available), real-time access to X (Twitter) data as a differentiating feature, and strong performance on reasoning-heavy tasks. The xAI API follows a familiar REST pattern and is broadly compatible with OpenAI SDK conventions, which makes migration straightforward. Grok's notable characteristics: Strong at structured reasoning and multi-step problem decomposition Real-time web access via the API (useful for tasks needing current information) Relatively generous rate limits compared to some competitors Less restrictive on certain content categories than some other models Gemini (Google DeepMind) Gemini is Google's model family, currently anchored by Gemini 1.5 Pro and Gemini 2.0 Flash. The defining feature of Gemini is its context window — Gemini 1.5 Pro supports up to 1 million tokens in production, which is genuinely useful for certain document-heavy use cases. Gemini also has the tightest integration with Google's ecosystem (Workspace, Cloud, Search)

Building a Racing AI from Scratch A while ago I received an email from my university inviting us to join the ibm global ai racing competition. Now that I'm finished with my exams I am going to give it a try. The testing ground for this project will be TORCS (The Open Racing Car Simulator). The Goal The primary objective is to build an autonomous agent capable of completing a clean lap around the Corkscrew track without crashing, and eventually, optimizing it for competitive lap times. The plan is to evolve the agent through a structured pipeline: Rule-Based Control (PID): Establishing a solid baseline using Proportional-Integral-Derivative controllers for steering and braking. Machine Learning: Upgrading the agent to learn from its environment using frameworks like PyTorch to replace hardcoded heuristics. Optimization: Fine-tuning the parameters and pushing the physics engine to the limit. The Tech Stack This project combines classic simulator architecture with modern local AI tools: Simulator: TORCS (running a local server). Language: Python (interfacing via the snakeoil3 library to parse sensor data and output telemetry). Local AI Assistant: ibm-granite-3.2-8b-instruct . I will be using this local LLM (hosted via LM Studio and integrated into VS Code with Continue.dev) to help architect the math, tune the control logic, and create/debug the Python code. What to Expect from this Series I will be documenting the entire process in this series. I will share the exact prompts used with the local AI, the generated code, the mathematical reasoning behind the control systems (such as why a naive PD controller causes zig-zag oscillation and how to fix it with damping), and the iterative debugging process. If you are interested in robotics, control theory, Python, or machine learning applications in simulation environments, follow along. The first technical log will be published shortly, detailing the implementation of baseline steering and look-ahead braking logic.

Exam Guide: Developer - Associate 🏗️ Domain 2: Security 📘 Task 2: Implement Encryption By Using AWS Services. Encryption shows up everywhere, especially on this exam. S3, DynamoDB, SQS, Lambda environment variables, RDS, and more. You need to know the difference between client-side and server-side encryption, how KMS works, and when to use each approach. 📘Concepts Encryption at Rest vs Encryption In Transit Encryption At Rest Data stored on disk: S3 Objects, DynamoDB tables, EBS volumes, RDS databases. Encryption In Transit Data moving between services or between client and server: HTTPS, TLS, VPN. Where At Rest In Transit S3 SSE-S3, SSE-KMS, SSE-C HTTPS (enforced via bucket policy) DynamoDB Encrypted by default (AWS owned or KMS) HTTPS (always) RDS KMS encryption SSL/TLS connections SQS SSE-KMS HTTPS Lambda env vars KMS (default + optional CMK) HTTPS KMS Key Types Type Managed By Cost Use Case AWS owned keys AWS Free Default encryption (DynamoDB, S3 SSE-S3 ) AWS managed keys AWS (in your account) Free (per-use charges) aws/s3 , aws/dynamodb (you can't manage them) Customer managed keys (CMK) You Monthly + per-use Full control: rotation, policies, cross-account Envelope Encryption KMS can only directly encrypt up to 4 KB . For larger data, it uses envelope encryption: 1. KMS generates a data key (plaintext + encrypted copy) 2. You encrypt your data with the plaintext data key 3. You store the encrypted data key alongside the encrypted data 4. You discard the plaintext data key from memory 5. To decrypt: KMS decrypts the data key → you decrypt the data The AWS Encryption SDK handles this automatically. Server-Side Encryption Options for S3 Option Key Management Use Case SSE-S3 AWS manages everything Simplest, no KMS costs SSE-KMS You control the KMS key Audit trail via CloudTrail, key policies SSE-C You provide the key with every request Full key control, AWS doesn't store the key Client-Side vs Server-Side Encryption Aspect Server-Side Client-Side Who encrypts AWS (

If you've used other browser-based code editors, you've probably noticed that the terminal feels off. You can run a script. You can print to stdout. But the moment you try to install a package and then actually use it in the next command, something breaks. The environment doesn't carry over. It feels like every command starts from scratch in a vacuum. That was the problem I wanted to solve when building the terminal for Cloudpen. Not just a place to run isolated snippets, but a proper environment where you can install dependencies, run build tools, and have everything you did in one command still be there for the next one. What most cloud terminals get wrong The core issue is that running code in the browser is hard to do without cheating somewhere. A lot of tools use sandboxed environments that look like a terminal but don't behave like one. They're good enough for demos. They fall apart in real work. The thing developers actually need is simple: if I install something, it should be there when I run the next command. That's it. That's the whole requirement. Surprisingly few cloud tools actually deliver it. How Cloudpen handles it Without going into the full technical detail, the short version is this: every command runs in a completely isolated environment, but all commands within your session share the same filesystem. So when you run npm install, those files are written somewhere. When you run your next command, that somewhere is exactly where it looks. Package installs work. Build tools work. Multi-step workflows work. And because each command runs in a clean, isolated environment, there's no bleed between users or sessions. The current terminal is optimized for commands that run to completion, while live application previews are handled through Cloudpen's deployment system. On the free plan, you can run any file in your project and see the output directly in the terminal. The live coding environment where you type commands yourself is on the Pro plan. Both use

We’ve all been there: staring at a messy medicine cabinet, wondering which box is for allergies and which one expired in 2022. In the world of Computer Vision and AI Healthcare , digitizing physical assets is a classic challenge. Today, we're building a "Medicine Box Expert"—a sophisticated pipeline that uses YOLOv8 for precision detection and OpenAI CLIP for multimodal understanding to turn a pile of pills into a searchable digital database. By the end of this tutorial, you'll understand how to bridge the gap between raw pixels and structured medical data. We are moving beyond simple classification; we are building a robust system capable of handling complex lighting, varied angles, and the tiny typography common in pharmaceutical packaging. The Architecture: A Multi-Stage Vision Pipeline To achieve high accuracy, we don't rely on a single model. Instead, we use a "Detect-Extract-Embed" workflow. graph TD A[User Uploads Image] --> B[YOLOv8: Box Detection] B --> C{Box Found?} C -- Yes --> D[Crop & Preprocess] C -- No --> E[Error: No Box Detected] D --> F[Tesseract OCR: Text Extraction] D --> G[OpenAI CLIP: Visual Embedding] F & G --> H[SQLite Query: Semantic Search] H --> I[Result: Drug Info & Dosage] Prerequisites Before we dive into the code, ensure you have the following tech_stack installed: YOLOv8 : For real-time object detection. OpenAI CLIP : To handle semantic image-text matching. Tesseract OCR : For reading the fine print on the boxes. SQLite : To store and query our medicine metadata. pip install ultralytics transformers torch pytesseract Step 1: Detecting the Medicine Box with YOLOv8 First, we need to locate the medicine box within the frame. A generic YOLOv8 model (like yolov8n.pt ) is surprisingly good at detecting "books" or "cell phones," but for the best results, you should fine-tune it on the Open Images Dataset specifically for "Box" or "Medical Packaging." from ultralytics import YOLO import cv2 # Load the model model = YOLO ( ' yolov8n.pt ' ) def

Just released an open-source bash checker for CIFSwitch (CVE-2026-46243) — the 19-year-old Linux kernel LPE disclosed last week that lets any unprivileged local user get root by abusing the CIFS/SPNEGO upcall path. The script runs on bare-metal, VMs, and inside containers, and is CI/CD-friendly with JSON output and clean exit codes. It checks: ✅ Kernel version against patched thresholds (6.18.22 / 6.19.12 / 7.0+) ✅ cifs-utils presence and exploitable version ✅ CIFS kernel module load state and blacklist status ✅ Unprivileged user namespace sysctl (the pivot point for the exploit) ✅ Active request-key cifs.spnego rules ✅ SELinux / AppArmor enforcement ✅ Container capabilities (CAP_SYS_ADMIN) ✅ Kernel symbol verification for the fix commit Outputs human-readable or JSON for SIEM ingestion. Exit 0 = safe, exit 1 = action needed — drop it straight into a pipeline. CIFSwitch is the fourth Linux LPE in under six weeks (after Copy Fail, Dirty Frag, and Fragnesia). If you're running multi-tenant Linux, CI runners, or container build farms, now is a good time to audit. I have also updated the cve_checks.conf in my my K8s-container_escape_audit toolkit to detect this issue.

Microsoft launched seven new in-house AI models at Build 2026 on June 2, 2026, marking the company's most significant push yet to build its own frontier AI stack independent of OpenAI. The centerpiece is MAI-Thinking-1, Microsoft's first large-scale reasoning model, built from scratch on clean commercially licensed data using a sparse Mixture of Experts architecture. Alongside it: MAI-Code-1-Flash, a 5-billion-parameter coding model that outperforms Claude Haiku 4.5 by 16 percentage points on SWE-Bench Pro while using 60% fewer tokens on complex tasks. This is the complete developer guide to all seven MAI models, their specs, benchmarks, deployment paths, and what they mean for the AI development ecosystem. Why Seven Models at Once? The strategic context matters. For three years, Microsoft's AI product surface — GitHub Copilot, Azure AI, Bing Chat, Microsoft 365 Copilot — ran almost entirely on OpenAI models. The Build 2026 announcement is Microsoft's public declaration that it is building a parallel, proprietary model stack. Every new MAI model is trained from scratch using "clean and appropriately licensed data, without distillation from third-party models" — language that directly addresses the intellectual property concerns that have accompanied third-party model licensing. The distribution strategy is equally deliberate. Microsoft is not routing MAI models exclusively through Azure. MAI-Thinking-1 and MAI-Code-1-Flash are available via Fireworks AI, Baseten, and OpenRouter — three infrastructure providers that collectively reach developers who explicitly do not want cloud vendor lock-in. This signals a platform-first posture: Microsoft wants MAI to become a model ecosystem, not just an Azure feature. MAI-Thinking-1: The Reasoning Flagship MAI-Thinking-1 is Microsoft's answer to Claude Opus 4.x and GPT-5.5 on the reasoning side of the model spectrum. The architecture is a 35-billion-parameter active / approximately 1-trillion-parameter total sparse Mixture of Ex

Claude Opus 4.8 shipped today. The benchmarks are a distraction — here is what actually changes about how your agents run tomorrow. Anthropic announced Claude Opus 4.8 at 16:00 UTC on June 3, 2026. The launch post leads with the usual benchmark deltas: SWE-bench Verified up 4.1 points, GPQA Diamond up 2.9, TAU-bench tool-use up 6.4. There is a chart. There is a marketing line about "the most capable agentic model we have ever shipped." If you stop reading there, you will miss the three things that will change how your production agents behave starting tomorrow. I have spent the morning re-running our internal agent harness against Opus 4.8 and reading the model card line by line. Two of the three changes are improvements. One of them is a silent regression that will bite anyone who pinned the model ID. Here is the full picture. What 4.8 actually changes The model card and release notes ship three changes that the launch blog post does not foreground: Cache-aware routing inside long agentic loops. The 4.7 router treated every tool-call cycle as a fresh planning step. 4.8 keeps an internal trace of which cache breakpoints were hit on the previous step and biases the next plan toward extending those traces. In agent harnesses that already use prompt caching aggressively (Claude Code, the Agent SDK with cacheControl: "ephemeral" on the system prompt), cache hit rates jumped from a measured ~46% on 4.7 to ~71% on 4.8 across a 30-step coding loop. The 200k context window now actually behaves at 200k. Anthropic published a needle-in-a-haystack chart in the model card going out to 200,000 tokens. The 4.7 chart got noticeably worse past ~140k tokens; the 4.8 chart is flat. This sounds like a benchmark thing. It is not. It changes the cost equation for "just stuff everything in context" patterns that 4.7 quietly punished by degrading accuracy. claude-opus-4-7 was not aliased. The launch shipped a new model ID — claude-opus-4-8 — and the previous ID is still callable. But if y

⚠️ この記事はアフィリエイト広告（プロモーション）を含みます。リンク先で発生した収益の一部が運営者に支払われますが、読者の購入価格には一切影響ありません。 If you work remote from rural Japan, by the end of this article you'll have two runnable Python scripts: one that computes your exact furusato-nozei (hometown tax) ceiling from your real side-income, and one that scores your electricity contract against your actual kWh log so you stop overpaying. No spreadsheets, no "consult a tax accountant" hand-waving. Copy, run, save money tonight. Result from my own 2025 numbers: ¥41,000 of furusato-nozei reward goods for a net cost of ¥2,000, plus ¥28,400/year shaved off my power bill after switching plans. Total ≈ ¥67,400 recovered, and because I work from home in Niigata, my commute cost to earn it was literally ¥0. The trap: side income breaks the "simple" furusato nozei calculator Every portal (Satofuru, Rakuten Furusato, Furunavi) shows a slider that estimates your ceiling from salary alone. The moment you add freelance/blog/ Kindle income, that slider lies to you. In 2024 I trusted it, donated ¥52,000, and ¥9,000 of it fell outside the deductible ceiling because my side income pushed me into a different residual-tax bracket. That ¥9,000 was just a donation — no tax back. The real ceiling depends on your total taxable income (salary + side hustle minus expenses) and the resident-tax (juminzei) cap of roughly 20% of your income-based resident tax. Here's a calculator that actually folds in side income. It uses Japan's 2026 progressive income-tax brackets. # furusato_ceiling.py — Python 3.9+ from dataclasses import dataclass # 2026 national income tax brackets: (upper_bound_yen, rate, deduction_yen) BRACKETS = [ ( 1_950_000 , 0.05 , 0 ), ( 3_300_000 , 0.10 , 97_500 ), ( 6_950_000 , 0.20 , 427_500 ), ( 9_000_000 , 0.23 , 636_000 ), ( 18_000_000 , 0.33 , 1_536_000 ), ( 40_000_000 , 0.40 , 2_796_000 ), ( float ( " inf " ), 0.45 , 4_796_000 ), ] @dataclass class Taxpayer : salary_income : int # after salary-income deduction (給与所得) side_profit : int #

A user picks a video from Photos. The app turns that video into a file the server can accept. Then it uploads the file. On the surface, this sounds like a simple upload flow. In practice, iOS makes you answer a much more specific question: How do you reliably turn a video from the user's Photo Library into an uploadable MP4 file? At first, I used AVAssetExportPresetPassthrough . It looked like the right default. It preserves the original media as much as possible, avoids unnecessary re-encoding, and is fast when it works. No quality loss, less CPU usage, less battery cost. But some videos failed during export. The error was usually in the AVFoundationErrorDomain Code=-11838 family. Apple describes this error as operationNotSupportedForAsset : an operation was attempted that is not supported for the asset. At first, I suspected an iCloud download issue, a Photos permission edge case, or something retryable inside PHImageManager . That was not the real problem. The actual problem was more fundamental: I was trying to write an iPhone MOV asset into an MP4 file using a passthrough export. The Original Flow The original code was roughly shaped like this: PHImageManager . default () . requestExportSession ( forVideo : asset , options : options , exportPreset : AVAssetExportPresetPassthrough ) { exportSession , info in exportSession ? . outputURL = outputURL exportSession ? . outputFileType = . mp4 exportSession ? . exportAsynchronously { // upload } } The intention was reasonable: Ask Photos for an export session for the PHAsset . Use AVAssetExportPresetPassthrough to preserve the original quality. Write the result as an .mp4 file for upload. Many videos exported successfully this way. That is what made the bug confusing. Some videos worked. Some did not. The hidden assumption was: Any iPhone video can become an MP4 file through a passthrough export. That assumption is not always true. iPhone Videos Are Usually MOV Files To a user, it is just "a video." Internally, an iPh