# Second Brain Joiner — Merge Markdown notes for LLM > AI input optimizer for Markdown notes, enhancing context and accuracy. (iPhone/iPad app by Hirofumi Inoue.) - Source: https://appshunter.io/ios/app/second-brain-joiner/id6760870675 (this page in markdown: same URL + `.md`) - Developer: [Hirofumi Inoue](https://appshunter.io/developer/1886583968) - Category: Productivity, Utilities - Price: $3.99 - Age rating: 4+ - Requires: iOS 18.2 · 11 MB - Languages: American English, Japanese, Chinese (Simplified, China) - Released: 2026-03-24 - Data updated: 2026-09-07 - Monetization: paid - User reviews in markdown: https://appshunter.io/ios/app/second-brain-joiner/id6760870675/reviews.md ## What is Second Brain Joiner? A professional-grade input optimization tool designed to push your AI's potential to the absolute limit. "Second Brain Joiner" is an application that seamlessly formats and merges your vast collection of Markdown files (your "Second Brain") stored on your device into a single context that AI can easily understand. While modern AI possesses incredible reasoning abilities, it doesn't know your "past context." However, blindly feeding it all your files isn't the solution either. If the amount of information exceeds the context window (the AI's memory limit), the AI becomes confused and generates "hallucinations" (plausible lies). This app was designed to solve that exact problem flawlessly. [Core Features & The Value of the PRO Spec] ◆ 1. Advanced Filtering (Enhancing Context Purity) You no longer need to give the AI "all your memories." By specifying tags or modification dates, you can smartly extract only the context relevant to the problem you want to solve right now. Eliminate noise and deliver 100% pure knowledge to your AI. ◆ 2. High-Precision Token Calculation & Smart Chunking Automatically splits (chunks) files into optimal sizes tailored to your AI's limits. Through highly accurate token estimation, even a massive vault with thousands of files can be processed without errors, dramatically improving the accuracy of your AI's responses. ◆ 3. Local-First Absolute Security Your thoughts belong to you alone. This app does not send data to external cloud servers; all merging and splitting processes are completed entirely within your device's local environment. You can securely process highly confidential business documents or personal diaries. ◆ 4. Folder Structure Maintenance & Timestamping It doesn't just connect text. It automatically inserts the original folder path and last modified date at the beginning of each file. This allows the AI to accurately grasp the timeline and hierarchical structure—"what project this is and when it was written"—before making advanced inferences. [Recommended for:] Prompt engineers and researchers who structure their daily knowledge using Markdown. Those who want to feed their past notes to AI to create a dedicated brainstorming and strategic partner. Those who demand the highest possible accuracy and minimal hallucinations from AI responses. Turn your "Second Brain" into the ultimate engine for your AI. Experience the breakthrough in intellectual productivity brought to you by H.I. MET ARCHITECT. ## Key features - Advanced filtering by tags and dates - High-precision token calculation - Smart chunking for AI context limits - Local-first absolute security - Folder structure maintenance - Timestamping for context ## Recent user reviews (1 of 1) All indexed reviews: https://appshunter.io/ios/app/second-brain-joiner/id6760870675/reviews.md ### 5/5 — 良いアプリ *2026-05-11* こういうのを求めてた、製作者に感謝。 ## Frequently asked questions about Second Brain Joiner ### What is Second Brain Joiner used for? Second Brain Joiner is used to format and merge your Markdown notes into a single context that AI can easily understand. It helps prevent AI confusion and 'hallucinations' by optimizing the information fed to it. ### How does Second Brain Joiner improve AI accuracy? It improves AI accuracy through advanced filtering to deliver pure context, high-precision token calculation for smart chunking, and by maintaining original folder structure and timestamps for better AI comprehension. ### Is my data secure with Second Brain Joiner? Yes, Second Brain Joiner is a local-first application, meaning all merging and splitting processes are completed entirely on your device. Your data is not sent to external cloud servers, ensuring absolute security for confidential information. ### What is the price of Second Brain Joiner? Second Brain Joiner is a paid application priced at $3.99. ### On which devices can I use Second Brain Joiner? Second Brain Joiner is available for iPhone and iPad. ### How often is Second Brain Joiner updated? The latest version, 1.1.2, was released on May 10, 2026, indicating a recent update. The app was initially released on March 24, 2026. ### What is the age rating for Second Brain Joiner? Second Brain Joiner has an age rating of 4+, making it suitable for a wide range of users. ### Does Second Brain Joiner have ads? No, Second Brain Joiner does not contain advertisements. ## Version history (last 5 releases) ### 1.1.3 — 2026-09-06 Fixed an issue where the app's supported languages (Japanese and Simplified Chinese) were not properly recognized on the App Store. Thank you for using Second Brain Joiner. Feedback and suggestions are always welcome via review or support contact. ### 1.1.2 — 2026-05-10 Performance and stability improvements ### 1.1.1 — 2026-05-06 Fixed minor bugs and improved app stability. ### 1.1.0 — 2026-05-05 Evolved into "PRO Spec" to push your AI's potential to the limit. Second Brain Joiner has evolved from a simple "file joining tool" into a professional-grade tool optimized for AI interactions. This is a major update designed for you to maximize your use of AI. 【What's New in Version 1.1.0】 ◆ Advanced File Selection (Filtering) You no longer need to feed your AI "everything." You can now smartly extract only the necessary context using specified tags or date ranges. Eliminate the noise and deliver high-purity knowledge to your AI. ◆ High-Precision Token Calculation & Smart Chunking Why do we need to "split" files? Even the most advanced AIs have a limit on how much information they can accurately process at once (Context Window). Forcing an AI beyond this limit causes confusion and leads to "hallucinations." This version introduces a feature that highly accurately estimates the token count in advance and automatically splits files into optimal sizes according to the AI's limits. This ensures that even massive Vaults can be processed without errors, drastically improving the accuracy of your AI's responses. ◆ New Language Support (Chinese) We have added support for the Chinese language to provide a smoother experience. Make your "Second Brain" smarter and sharper. Happy Linking! ### 1.0 — 2026-03-24 No release notes. ## More apps by Hirofumi Inoue - [VaultPress](https://appshunter.io/ios/app/vaultpress/id6760890486) All apps by Hirofumi Inoue: https://appshunter.io/developer/1886583968 --- *Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-09-07.*