An idea book for building with coding agents.

Build deliberately.

Think an idea all the way through: the problem, the flow, what it’s worth and what you’re not doing. Then hand it to your engineers or your agents.

A sample idea open in Walden: Let customers reschedule their own appointments. Under its title, how deep each part of the idea goes; then the problem, with a count from the phone log, and what it is worth.

Building software has gotten fast.

Your agent will build exactly what you ask for, often in an afternoon. The trouble is everything you didn’t mention. It has to guess, and it doesn’t always guess the way you would have.

Here’s the same feature, started two different ways. On the left, someone typed a one-line prompt. On the right, their team worked the idea through in Walden before anyone started building.

A one-line prompt

> Let customers reschedule their own appointments.

What the agent had to guess

Can two people grab the same slot?
What happens to a deposit they’ve paid?
Does the reminder follow the new time?

The same idea, worked out in Walden

Let customers reschedule their own appointments.

What the team decided first

Can two people grab the same slot? The slot is held while they choose.
What happens to a deposit they’ve paid? It carries over to the new time.
Does the reminder follow the new time? Yes. We cancel the old reminder and send a new one.

Everything you need to work an idea out, before anyone starts building.

You can drag these frames around.

Ada Lovelace

Work your idea out, part by part.

Every idea in Walden has a few parts: the problem, the approach, the unknowns, and what you’re not doing. You can add what it’s worth too, if you need to weigh it against other work. Walden shows you how deep each part goes, from sketched to ready, and the next thing to settle, so you can see whether your team or agent could pick it up without coming back to you with questions.

The idea

ProblemDoes it say who has the problem, and what goes wrong for them?Does it rest on something seen, said or counted?Ready
WorthIs a size set?Does it say why this much, and not more?Ready
ApproachDoes it name the main parts, and say how they fit together?Is every decision a builder would come back to you for made, or plainly left to them?Shaped
UnknownsDoes it name questions whose answer would change the approach?Is each one settled, left to the builder or ruled out?Shaped
Not doingDoes it name something left out on purpose?Does each one say why it’s out?Ready

Each answer comes from reading the page as last saved. Readiness stops nothing, and it stays with you: it isn’t exported.

Get your idea read before it’s built.

Pick a second reader to look at your idea: a builder, a decider, a fair skeptic, or one you write yourself, like the customer you’re building for. They leave questions next to the part they’re about, but they never rewrite your idea. If a question matters, add it as an open question. If it doesn’t, dismiss it, and they won’t ask it again. Go ahead and try it: pick a reader and press Read.

Readers

Problem

Last month the front desk took 212 calls from customers moving an appointment.

Approach2 open

Add a Reschedule link to the reminder email. It opens a page with their current time and the open slots, and they pick a new one.

A builder would ask

What happens if someone else books that time while they’re choosing?

Add as open questionDismiss

A regular customer would ask

Will I still get a reminder for my new time?

Add as open questionDismiss

Start from a sentence.

Tell the chat what you’re thinking in a sentence or two, and it can draft the whole idea for you, or just a flow or a list of unknowns. Drafts show up dashed on the page and don’t count until you keep them. It won’t touch anything you wrote.

Chat

See it before it’s designed.

Map out the screens and how someone moves between them, and Walden sketches each one, starting from the real screen in your app. If you haven’t decided between two ways of doing something, it sketches both and leaves the choice open until you pick one. You can look at it on a phone, a tablet or a desktop, and pin notes for your designer.

Flow and UI sketches

Ask the front desk how many calls are about deposits.

Owen Martin

Plan it with your team.

Invite your designers and engineers while the idea is still taking shape. They see what’s open, follow along as it changes, and leave their questions in the margin, so the edge cases get caught before anyone starts building.

Editors write the idea with you. Viewers read along and ask questions, for free.

Product · Owen

Gets the problem nailed down before anything gets built.

Design · Ada

Gets involved while the idea is still taking shape, instead of being handed a finished ticket.

Engineering · Dale

Gets the edge cases answered before building starts, instead of halfway through.

Walden knows your product.

Connect your project to its repository and Walden reads your codebase: the files, the routes, the schema. The readers, the chat and the sketches all use that context, so the questions you get are about your product, not software in general.

You can also ask the chat what an idea needs to store, and it’ll draw a diagram from the tables you already have.

Bookings, connected to acme/bookings·What gets stored

filesapp/routes/reschedule.$id.tsx, app/lib/slots.server.ts and 184 more

routes/ /book /reschedule/:id /account

schemacustomers, appointments, slots, reminders

We asked a skeptic to read this page.

Is the problem smaller, or the answer bigger, than it looks?

A skeptic would ask
Isn’t this just waterfall?
Open
A skeptic would ask
Why plan when I can prototype twenty versions?
Open
A skeptic would ask
Isn’t this just another spec tool?
Open

Start planning for free.

Walden is free to use. Upgrade when you want more AI credits, or when you want to bring your team into the planning process.

Free

$0forever

Everything you need to start planning.

Ideas, flows, sketches and canvases
Present your idea, and hand it off as a package
20 credits to start, then 5 a day
No credit card, no time limit

Personal

$20a month

For solo founders and product thinkers doing the planning.

Everything in Free
400 credits a month
Unused credits carry over a month
Top up any time: $10 for 150 credits
Use your own model key if you have one

Team

$30per person, a month

Bring design and engineering into the planning process.

A shared workspace for your team’s ideas
Invite your designers and engineers to read along and leave questions
See who’s looking at an idea with you
400 credits per person, shared across the team
Unused credits carry over a month
Top up any time: $10 for 150 credits
Use your own model key