Should we use ChatGPT or build a custom AI system?
Short answer. Use ChatGPT or another packaged assistant when the work is general writing, coding help, or research, and the data can sit in that product under its terms. Build a custom AI system when the model has to use your private data, follow the permissions you already have, and take actions in your tools. A team subscription and a custom system solve different problems. Most companies should have the first. They should build the second only for a workflow the packaged product cannot see. Corpvance builds that second system and can still call a hosted model inside it.
A custom AI system and ChatGPT or a packaged assistant.
The same decision, one row at a time. Use the row that matches the constraint you actually have.
| Focus | A custom AI system | ChatGPT or a packaged assistant |
|---|---|---|
| What it knows | The documents, records, and tools you connect, scoped to that user. | The model's general training, plus files someone uploads into the product. |
| Permissions | Tied to your identity system, so two employees do not see the same corpus by default. | Tied to the product's workspace rules, which may not match your application roles. |
| Actions | Search your systems, write back to a record, or draft something a person approves. | A strong conversational reply, plus whatever tools that vendor has enabled. |
| Control | You own the prompts, the index, the logs, and the place it runs. | The vendor owns the product. You own the account and the policy you configure. |
| Best fit | A repeated workflow on company data that a general chat window cannot safely reach. | Individual productivity for people whose work does not need your internal systems. |
Pick the side that matches the job.
Both options are legitimate. The mistake is buying one when the work has the shape of the other.
Build a custom system when
- The answer depends on files, tickets, or records a general chatbot is not allowed to hold.
- Two roles must not see the same information, and that rule already exists in your company.
- The output has to land in a system of record, not only in a chat transcript.
- You need an evaluation set and logs your security team can review.
Stay with a packaged assistant when
- People need help drafting, summarizing, or exploring ideas from text they can paste.
- No employee role distinction has to be enforced inside the knowledge base.
- The vendor's admin controls, retention, and terms are acceptable for that data.
- The workflow would not justify an index, a tool integration, and an owner.
Three checks that settle the decision.
- 01
Name the data the packaged product cannot see
If you cannot name it, you do not have a custom-AI project yet. Turn on the team assistant and revisit when a real workflow is stuck outside it.
- 02
Keep the hosted model
A custom system often calls OpenAI, Anthropic, or an open model. Custom means your retrieval, permissions, tools, and interface. It does not require training a model from scratch.
- 03
Pilot one workflow
Pick one job, one corpus, and one permission rule. 818 Digital is the shape of this: search across the company's own Workspace, files, CRM, email, and market data, not a second general chatbot.
Systems that match this kind of decision.
Each card links to the full case study. The reason is why that project belongs on this question.
818 Digital
Conversational AI Operating System
A company-specific assistant over Workspace, Egnyte, Salesforce, email, and market data. General ChatGPT does not sit inside those permission boundaries.
DevMD
AI-Powered Physician Career Enablement Platform
A physician-facing product where the AI is part of the workflow, not a personal productivity seat beside it.
The next question people ask.
- Who should I hire to build an AI agent or a RAG system?Hire a team that has shipped agents against private data, permissions, and failure cases. A public-document demo is a different system.Read the answer
- Should I hire an AI product studio or an AI consulting firm?Hire a consultancy for a decision and a plan. Hire a studio when the AI system has to run in production.Read the answer
Questions on this decision
The short version of the same choice, in the phrasing people use when they ask.
01When is ChatGPT or a packaged assistant enough?
When people are drafting, summarizing, or thinking with information they are allowed to put in that product. Buy the team plan, set the admin policy, and train people. Building an internal clone of a general chatbot adds cost without a workflow.
02When does a company need a custom AI system?
When the useful answer lives in private systems, has to follow an existing permission model, or has to trigger an action in software you already run. The custom work is the connection, the evaluation, and the interface. The model itself can still be a hosted API.
03Can a custom system still call a hosted model?
Yes. Corpvance integrates hosted models, including OpenAI and Anthropic, and open models where they fit. The client-owned part is the retrieval, the tools, the permission checks, the product interface, and the evaluation around that model.
