Her Prompt Was Perfect. She Still Burned the Whole Day.
The mode you pick matters more than the prompt you write. Three signals tell you which one to choose, and each takes about ten seconds to check.
You Picked The Wrong Mode And The Answer Still Looked Fine
Every time I do a training session, this question always comes up. You’ve shown us that Claude has both “Chat” and “Cowork.” How do I know when to choose each one?
It happened again this past week. I was doing a training session, and someone asked that exact question. “How do I know which one to use?” Why would I choose one or the other? I said, “Let’s talk about a real-world workflow you’re doing these days.” What have you been working on?
She said, let me show you exactly what I was doing yesterday. I’ve been running this same process for a while now. I open up a transcript from a trial we’re working on, copy a section out of it, and then paste it into Claude. I have a detailed prompt that I copy and paste that creates a summary. Once Claude is done summarizing, I copy that text out and put it in a Word file. Then I scroll down into another section of the trial document and repeat the process. Sometimes I’ll do 10, 12, 15 transcripts in a day, and it will actually take me most of the day.
The truth is, nothing she was doing was technically wrong. Her prompt was good (she had even used Claude to make it better), and her summaries were great. She is smart, competent, and an AI leader in the organization, so I want to make sure she keeps having success with Claude. The challenge here wasn’t that she was using the tool badly. It’s that she chose the wrong mode.
TL;DR: Chat is for having a conversation. Cowork is for having Claude take action on documents for you. When you use the chat mode interface, you (the human) are deeply involved in ongoing interactions with chat. With Cowork, you give it a ton of context, the instructions, and say go. You still have to engage at the end, but you aren’t involved in every single step of the way making decisions.
Chat Is “Help Me With This.” Cowork Is “Handle This For Me”
When you are using chat mode, you (the human) are involved in every interaction. You get the results, read them, and decide what to do next. Ask another question, head in a different direction. When you are using Cowork, you give Claude a lot of context and a job to do and then let it run. Cowork will create the steps and then take action on its own.
One of the things I’ve seen attorneys get wrong again and again, though, is the following. They think that “easy” questions go into chat and “harder” questions go into Cowork. I get the instinct, but unfortunately it’s completely wrong. Making that decision is how an attorney ends up with a 20-minute Cowork process to rewrite a single paragraph.
When The Same Task Can Be Run In Either Mode
If you want to summarize a single deposition, put it into a chat. When you want to summarize 20+ depositions and also look for contradictions, use Cowork. The legal thinking involved in the underlying analysis is similar, but the process is different.
Asking Claude whether a contract has a “limitation of liability” problem is an issue for Chat. Checking 50 vendor contracts in a folder for the same problem is Cowork. It’s the same question being asked, just across 50 different documents. What is different here is the volume of documents you want to process and the steps you have to go through to get that work done. When using chat, the most common output most people ask for is just text. When using Cowork, most people typically want Claude to create an output document (say a “document log.”)
How To Choose: Look At These Three Signals
I tell clients there are three easy ideas that help you decide if this is a question for Chat or a task for Cowork:
First, it’s a question of volume. Are there more documents than you can upload into a chat or a project? If you have a small handful of documents, I would consider choosing Chat. If you have a folder with 20+ documents to analyze, that decision is a no-brainer: choose Cowork.
Second, if getting to the analysis or answer you want requires multiple steps (e.g., you’re doing a process), choose Cowork. Cowork is great at following a detailed set of steps (do this first, and then do that).
Third, if the output you want is a document (a Word doc, a text file, a PDF, an Excel spreadsheet, a PowerPoint), then use Cowork. You can even open the output document and view it right there in the Claude desktop app.
One thing to keep in mind (I was a CFO after all so I’m always thinking about cost) is that Cowork definitely takes more tokens (it’s typically running a more complex process), so you’ll burn through more of your subscription more quickly. Or spend more on direct token costs if that is the type of plan you are on.
Finally, don’t think of Chat as beginner mode or something just for simple questions. It’s the right answer for a lot of the things you do. Think about those three signals I mentioned above and know when to choose Cowork instead.
Nobody Gets This Right In The Beginning, Not Even Me.
Remember that when you are using Chat, you (the human) are the intermediary between every step. You read the output and decide what to do next. When you are using Cowork, Claude is taking all of the steps, and you are providing the review only at the end.
If you’ve pasted the same prompt five times in a row into chat, it’s probably a good indication that you should be using Cowork. In the early days of using these tools I can’t tell you how many times I did exactly that. If you get to the bottom of a process and load another file in and say “now do this just like the last one” - that’s another good sign that you should be using Cowork.
But how do you know when you should be using chat instead of Cowork? One quick way that is almost always true is that you need the answer immediately. You don’t need lots of document processing, just an answer. When you only need a single paragraph or a small edit and not a full document, that’s a good sign you should be using Chat.
Putting things into Cowork instead of chat is an easy mistake to make, but it really only wastes a few minutes of your day. Doing a lengthy process in chat and repeating yourself again and again and running out of the context window can cause you to blow an entire afternoon.
Having The Right Prompt Matters
When I run legal training sessions, I typically teach the CORE method of prompting (Context, Objective, Role, Examples). But a prompt doesn’t have to be that complicated. A prompt in Chat can be one good line because you have to be there every step of the way to review the results and steer the conversation.
Cowork, on the other hand, requires adding files or pointing to a folder, providing the full context, detailing the analytic steps (in order), and a description of the desired output. I find that making sure that Cowork delivers what I need requires far more planning than a typical chat does.
Let me make it real for a second. I have to sign a lot of NDA’s with clients. Two years ago I would drop the NDA into Claude and type “analyze this NDA for me.” It would analyze it in a very general way, and it might flag something unusual.
Now I’m much more likely to drop the NDA into Claude and type something like “analyze this NDA for me. Make sure it’s a mutual NDA that protects both of us. Look for intellectual property issues - specifically anything that might put my personal IP at risk in any way. Look for any clauses that are outside the industry norm and flag those for me.”
In Cowork, point Claude at a folder that has a hundred transcripts and tell it to create a summary from every transcript that includes the following:
A list of every witness in the transcript
The dates they were deposed
A reference to every statement they made about a specific issue, including page and line numbers.
Put into an easy to read and analyze excel file. Give Claude Cowork the full assignment with the full instructions.
One last lesson I’ve learned the hard way. When you are using Cowork, don’t forget about the guardrails! Tell it what not to do and what not to focus on - make sure that it only focuses on what matters.
What You Should Do On Monday Morning
If you walk away with nothing else, walk away with this. Teach your team two things. Chat is for “Help me with this.” Cowork is for “Handle this for me.”
If your team has been using Claude for a while now, ask them for examples of what they’ve been pasting into Claude. Find out who on your team has been pasting in the same prompt again and again. That should be your first Cowork example with the group.
Find time to play with Cowork this week. Find out what it can and cannot do. Do something simple like “find all of the image files in my downloads folder, open them up, figure out what they are and then rename the file to a descriptive name.” Show the group a simple but powerful example of how it can work.
In Cowork, You Are The Final Review
Cowork can create an entire folder of content for you. 40-page Word documents, large multi-tab Excel files with complex formulas. Don’t forget that when you use Cowork, the review matters even more since you weren’t involved in every turn of the creation process. You weren’t the human in the loop; you are the final review step. In every presentation I give, I always tell the attorneys the following: “AI doesn’t have a bar number. You do.” It’s your job to verify the output, as it will ultimately have your name on it. This is even more important when Cowork creates an entire folder of content for you.
BONUS: I created an infographic that helps explain this. Please feel free to download and pass around.
If you enjoyed this article, please share it with others! Here’s a cute shot of Magnus about to enjoy some steak (note what the plate says - a little humor for your day!).
