# Assistant setup: ChatGPT, Claude and Gemini Version 2026-09-15-v1. Part of the Mortgage AI Starter Kit from Leaf360. These notes describe the consumer and team applications, not the vendors' APIs. Every statement was read from the vendor's official help page on 15 September 2026 and links to it. Plans, limits and settings change; if the page and this note disagree, the page wins. Nothing here names or recommends a specific model. Pick the current default in the app. ## ChatGPT (OpenAI) **Upload the practice file.** File uploads are available on Free and paid ChatGPT plans, subject to plan limits, on the web and in supported mobile apps. Spreadsheets and CSV files are supported; the FAQ gives a limit of roughly 50 MB per spreadsheet and a rolling cap of 80 uploads per 3 hours, with Free limited to 3 uploads a day. The practice file is 1 KB. Source: File Uploads FAQ, https://help.openai.com/en/articles/8555545-file-uploads-faq **Save the instructions.** Projects are available on all free and paid plans and hold files, chats and project instructions in one place. Put `prompt.txt` in the project instructions and `synthetic-contacts.csv` in the project files. Project instructions override your global custom instructions inside that project. The number of files per project depends on the plan (Free 5, Go and Plus 25, Edu, Pro, Business and Enterprise 40 at the time of reading). Source: Projects in ChatGPT, https://help.openai.com/en/articles/10169521-projects-in-chatgpt **Check the data setting before real data.** For individual services such as ChatGPT, OpenAI may use your content to train its models unless you opt out: turn off "Improve the model for everyone" under Settings, then Data Controls, or use the privacy portal. Temporary Chat conversations are not used for training. Business products (ChatGPT Business, ChatGPT Enterprise and the API) are not trained on by default. Source: How your data is used to improve model performance, https://help.openai.com/en/articles/5722486-how-your-data-is-used-to-improve-model-performance ## Claude (Anthropic) **Upload the practice file.** Claude accepts CSV, along with PDF, DOCX, TXT, XLSX and other document types, by attaching files to a chat or dragging them in. Limits at the time of reading: 500 MB per file and 20 files per chat, or 30 MB per file in a project's files. Source: Upload files to Claude, https://support.claude.com/en/articles/8241126-upload-files-to-claude **Save the instructions.** Projects are self-contained workspaces with their own knowledge and instructions and are available to all users, including free accounts (five projects on Free at the time of reading). Put `prompt.txt` in the project instructions and the CSV in the project knowledge. Source: What are projects?, https://support.claude.com/en/articles/9517075-what-are-projects **Check the data setting before real data.** On consumer plans, whether chats may be used to improve Claude is controlled under Settings, then Privacy, "Help improve our AI models." Turning it off stops future chats from being used for training. Commercial products such as Claude for Work are not used for training by default. Team and Enterprise owners can also switch off feedback submission for members. Sources: How do I change my model improvement privacy settings?, https://privacy.claude.com/en/articles/12109829-how-do-i-change-my-model-improvement-privacy-settings and Is my data used for model training?, https://privacy.claude.com/en/articles/7996868-is-my-data-used-for-model-training ## Gemini (Google) **Upload the practice file.** Signed in to Gemini Apps, you can upload documents and spreadsheets to get answers and summaries; most file types up to 100 MB, up to 10 files in one prompt, with higher limits on a Google AI plan. Source: Upload and analyze files in Gemini Apps, https://support.google.com/gemini/answer/14903178 **Save the instructions.** A Gem is a saved set of instructions. Create one under Explore Gems, then New Gem, paste `prompt.txt` as the instructions and add the CSV under Knowledge from your device or Google Drive. Source: Tips for creating custom Gems, https://support.google.com/gemini/answer/15235603 **Check the data setting before real data.** With Keep Activity on, Google uses Gemini Apps activity, including uploaded files, to provide, develop and improve its services, including training generative AI models. Turn Keep Activity off in Gemini Apps Activity and future chats are not used to improve its models unless you send feedback. A subset of chats may be reviewed by human reviewers and retained for up to three years, so do not enter confidential information you would not want a reviewer to see. Source: Gemini Apps Privacy Hub, https://support.google.com/gemini/answer/13594961 ## Which one should I use? The one your company already pays for and has approved. This kit ran the same job on none of them; it was written to be assistant-neutral, and the example output was written by hand. A side-by-side test on the practice file is the right way to compare them for your team, and the answer key in `example-output.md` is the scorecard. ## Not legal advice These notes summarize vendor pages for convenience. Follow your company's data policy and applicable law before any borrower information goes into an assistant. Leaf360 is software sold to mortgage companies; it is not a law firm or a compliance service.