Vibewright

2026-10-24

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How to set up a Fractional CFO agent in a ChatGPT Project

If you live in ChatGPT and want a fractional CFO that remembers your business, plans your taxes and keeps its personality from chat to chat, the place to put it is a ChatGPT Project. A project keeps chats, files and instructions together, and the instructions apply to every chat inside it. This guide walks through the current ChatGPT flow, using OpenAI's help pages as checked on October 24, 2026, and shows how to load a full-length agent prompt without losing the parts that matter.

It follows Vibewright's Fractional CFO · Tax Planner builds, which release in five tones on Monday, October 26, 2026 at 10:00 AM ET. They are not downloadable before then.

Why not a Custom GPT?

OpenAI's help center now says new GPT creation and publishing are not available on personal ChatGPT accounts (Free, Go, Plus and Pro), and that it plans to retire custom GPTs in favor of plugins, with retirement planned for Dec 11, 2026 in affected Enterprise workspaces and other plans expected to follow. (OpenAI help: Creating and editing GPTs) A project works on every plan, so that's what this guide uses.

What you'll need

• A signed-in ChatGPT account. Projects are included with every qualifying plan at no extra cost. (OpenAI help: Projects in ChatGPT)
• A Vibewright build file (a Markdown system prompt): the free CFO · Tax Planner · Funny sample after 10/26, or a paid build from /pricing.
• A plain-text editor that shows a character count.
• Optional: redacted notes on your entities, last year's numbers and your tax calendar.

1. Create the project

1. Select New project in the ChatGPT sidebar.
2. Enter a name, then pick an icon and color. Name it for the job, for example CFO · Tax Planner.

2. Know the size problem before you paste

A Vibewright build is a full operating manual, not a one-paragraph persona. Each of the five CFO · Tax Planner builds runs roughly 28,000 to 31,000 characters, with refusals, workflows, memory rules, output formats and worked examples.

ChatGPT's instruction fields have limits. OpenAI documents 1,500 characters for global custom instructions on Free and Go and 5,000 on paid plans. (OpenAI help: Custom instructions) OpenAI's Projects page doesn't publish a limit for project instructions, but users widely report that field stops at about 8,000 characters. Either way, a full build won't fit in one box, so split it the way OpenAI's own guidance suggests: rules, tone and guardrails go in instructions, and reference material goes in files. (OpenAI help: Creating and editing GPTs, Knowledge best practices)

3. Upload the full build as a project file

1. Open the project and add a file to its sources. Projects accept PDFs, spreadsheets, docs, images and pasted text.
2. Upload your build's .md file, for example CFO-TAX3-FUN-v1.0.md. Keep the whole file.

File limits depend on your plan: 5 files per project on Free, 25 on Go and Plus, and 40 on Pro, Business, Enterprise and Edu. You can upload up to 10 at a time. (OpenAI help) The build uses one slot.

4. Paste the core sections into project instructions

Select the more options menu (•••), then Project settings, and add instructions. Project instructions apply only inside that project and override your global custom instructions. (OpenAI help)

Paste a short loader line first, then copy these four sections from your build file, word for word:

1. Absolute refusals (read first)
2. 1. Identity
3. 5. Communication style (this is where the tone lives)
4. 12. Guardrails

Across the five CFO · Tax Planner tones, those four sections come to about 6,300 to 7,000 characters, which leaves room for the loader. Check the count in your editor before you save. Here is a loader you can use (swap in your file name):

The file CFO-TAX3-FUN-v1.0.md in this project's sources is your full operating manual. Read it before your first reply in every chat and follow all of it: workflows, memory rules, output formats and examples. The sections below are copied from that file. If anything conflicts, these sections win.

Why these four: the refusals and guardrails are the safety rules, and identity plus communication style are the personality. You want those in the field ChatGPT applies to every chat, not only in a file it reads from.

5. Pick a memory setting

In Project settings, under Memory, choose Default memory or Project-only memory, then save. OpenAI notes the change can take a few hours to take effect. (OpenAI help)

• Project-only memory keeps your tax conversations walled off: your saved memories aren't used in project chats, chats can reference other chats in the same project, and chats outside the project can't see them.
• If you share the project with a bookkeeper or partner, it is automatically set to project-only memory.

For most owners running a private CFO agent, project-only memory is the cleaner choice.

6. Start a chat and test it

1. Start a new chat from inside the project so it picks up the instructions and file. (If the first message of a chat uses a custom GPT, that chat starts outside the project.)
2. Turn on web search if it's available to you, so the agent can check current-year figures instead of relying on training data.
3. Say "run onboarding", as the build's setup notes direct.
4. Test the tone: ask a real question, such as how to plan for a large estimated tax payment, and check the voice matches the build you loaded.
5. Test the guardrails: ask it to help you keep deposits under a reporting threshold. It should open with a clear no and offer a legitimate alternative.
6. Test the file: ask for a workflow that lives only in the file, such as "run year-end planning." If it answers generically, start a new chat and tell it to read the build file first.

Keep tax returns with SSNs or full account numbers out of the project. Use redacted summaries, especially in a shared project, where every member can view and download its files.

Which CFO Tax Planner tone to load

Same facts and deadlines, five ways to hear them. All five release on 10/26:

Not sure which one fits? See the five tones compared. Prefer Claude? Follow How to set up a Fractional CFO agent in Claude Projects. Still choosing a tool? Read Claude Project vs ChatGPT Project vs Gemini Gem for business agents. Once it's loaded, put it to work with the year-end tax planning checklist.

The agent gives educational information, not tax, legal or accounting advice. Confirm big decisions with your CPA.

Get the build

• Free sample: claim the CFO · Tax Planner · Funny build with your email. It is delivered on 10/26. License: Personal and commercial use allowed. No redistribution.
• Pick your tone: single build $9, role pack $49, launch bundle $79, All-Access $19/mo or $149/yr, or Founding Member $199 lifetime for the first 100. Checkout opens 10/26. 7-day refund on subscriptions. No refunds on downloads.

Builds are not downloadable before their release date. The CFO Tax Planner unlocks with the Mon 10/26 drop.

Choose your CFO Tax Planner tone on /pricing · Or grab the free Funny sample