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Claude Project vs ChatGPT Project vs Gemini Gem for business agents
You have a system prompt for a business agent, like a fractional CFO that plans your taxes. Now you need a home for it: somewhere the instructions load on every chat, your reference files stay attached, and you don't paste the same prompt again every morning. The three most common homes are a Claude Project, a ChatGPT Project and a Gemini Gem. This guide compares them using each company's current help pages (checked October 22, 2026), so you can pick one and move on.
Short version: pick the tool you already pay for and open every day. All three load standing instructions and reference files. The real differences are memory, sharing, and what is being retired.
First, what about Custom GPTs?
If you were planning to build a Custom GPT, check OpenAI's notice first. Its help center now says new GPT creation and publishing are not available on personal ChatGPT accounts (Free, Go, Plus and Pro), and that OpenAI 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 the same timeline. Existing GPTs stay usable until then. (OpenAI help: Creating and editing GPTs) For a new business agent on ChatGPT, a Project is the safer home today.
Side by side
| Claude Project | ChatGPT Project | Gemini Gem |
|---|
| Who can make one | All plans, including free (free accounts: up to five projects) | Signed-in users, subject to plan and workspace settings; unlimited projects | Signed-in users 13+ on personal accounts (work and school accounts may have different terms) |
| Where the prompt goes | Set project instructions | ••• menu, then Project settings | The Instructions field when you click New Gem |
| Reference files | Project knowledge (docs, text, code); paid plans switch to RAG mode as knowledge nears the context limit | 5 files per project on Free, 25 on Go and Plus, 40 on Pro, Business, Enterprise and Edu; Google Drive and Slack links as sources | "Knowledge" files from your device, Google Drive (always the latest version) or a NotebookLM notebook |
| Memory | Each project has its own memory; turn off Use account memory to keep it fully separate | Default memory or Project-only memory, set per project | Not covered on Google's Gems help page |
| Sharing | Team and Enterprise plans, with Can view or Can edit | Free through Enterprise, with chat or edit access; shared projects always use project-only memory | Gems can be shared; a shared Gem appears in "My Gems" once the person uses it |
| What's changing | Nothing announced on the Projects help page | Custom GPTs being retired in favor of plugins (see above) | Gems on personal accounts move to skills starting November 2026; work accounts follow in 2027 |
Claude Projects: best when you live in long documents
A Claude Project keeps instructions and a knowledge base together, and Anthropic says anything in project knowledge is used across every chat in that project. One detail that trips people up: chats inside a project don't share context with each other unless the material is in the project knowledge base. So put the things a CFO agent always needs (entity list, recurring deadlines, your CPA's contact rules) in knowledge, not in an old chat.
Memory is per project. Claude uses the project's memory alongside your account memory from chats outside projects. If you want your CFO agent walled off from everything else, turn off Use account memory under Memory on the project's page. (Anthropic help: Projects) Full walkthrough: How to set up a Fractional CFO agent in Claude Projects.
ChatGPT Projects: best for teams and connected apps
- Select New project in the sidebar and give it a name.
- Upload the full build
.md file to the project's sources. A full build runs about 28,000 to 31,000 characters, more than ChatGPT's project instructions field holds. OpenAI doesn't publish an exact limit for that field, so don't try to paste the whole build there.
- Open the ••• menu, select Project settings, and paste a short loader line plus the build's core sections (Absolute refusals, Identity, Communication style, Guardrails) into the instructions. See our ChatGPT Projects setup guide for the loader text. Project instructions apply only inside that project and override your global custom instructions.
- Under Memory in the same settings, choose Project-only memory if you don't want your saved memories or other chats mixed in. OpenAI notes the change can take a few hours.
- Add files, or paste Google Drive and Slack links as project sources.
Sharing is where ChatGPT stands out: it is available on every plan from Free to Enterprise, members get chat or edit access, and a shared project automatically uses project-only memory, so it can't see a member's personal memories. Collaborator limits depend on plan (for example, 5 on Free, 10 on Plus and Go, 100 on Pro). (OpenAI help: Projects in ChatGPT)
Gemini Gems: best if your files are already in Google Drive
- Go to gemini.google.com, open the sidebar and click Gems.
- Click New Gem, enter a name, and paste the build into the instructions.
- Optionally, under Knowledge, click Add files to upload files or add them from Drive. Drive files stay current: if you edit the file, the Gem uses the newest version.
- Click Save. A Gem made on the web also shows up in the Gemini mobile app and the Gemini side panel in Google Workspace.
The catch is timing. Google says Gems on personal Google accounts go away starting November 2026 and will be converted to skills automatically, along with supported files. Workspace business, enterprise and nonprofit accounts follow no sooner than March 2027, and education accounts in June 2027. Skills are reusable custom instructions you call by typing / and the skill's name in any chat, and you can stack more than one. On a personal account, skills currently require being 18 or over. (Google help: Gems · Google help: Gems to skills) If you start a Gem today, expect the button names to change soon.
Which one should you pick?
- Solo owner who wants a private CFO: a Claude Project with account memory turned off, or a ChatGPT Project set to project-only memory. Both keep your tax context in one walled-off place.
- Owner plus a bookkeeper or assistant: a ChatGPT Project, since sharing works on every plan. On Claude, sharing needs a Team or Enterprise plan.
- Everything already lives in Drive: a Gemini Gem (or a skill), since Drive files stay current automatically.
- Whatever you pick: keep the instructions in the instructions field, keep reference material in files, and start new chats inside the project or Gem so the rules apply.
Whichever home you choose, the prompt itself does the work. Vibewright builds are written as one system prompt, so the same build works in all three. Claude and Gemini take it pasted whole; in ChatGPT, upload it as a project file and paste the loader plus core sections into instructions. For what belongs inside that prompt, see Best system prompt for a tax-planning AI agent. To choose a voice, see How to give your AI agent a personality (5 tones compared).
A reminder for tax agents on any platform: the agent gives educational information, not tax, legal or accounting advice. Don't upload full returns, SSNs or account numbers to a shared project; use redacted summaries, and bring your CPA in for the big calls.
Get a CFO agent ready to paste
All five Fractional CFO · Tax Planner tones (Aggressive, Affirming, Dry, Funny and Sarcastic) release on Monday, October 26, 2026 at 10:00 AM ET. They are not downloadable before then.
- 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.
Choose your CFO Tax Planner tone on /pricing · Or grab the free Funny sample