Which assumption do we each hold differently?
PreviewFind what changes the decision.
Meets you where you are
In your coding agent and your documents today.
Live
- Claude Code
- Claudeconnector
- Google DriveDocs, Sheets
Preview
- Codexover MCP
- ChatGPTconnector
- PerplexityPro plans
- Google Workspaceadd-on
Names show what Cruxes connects to, not an endorsement or partnership. Perplexity needs a plan that allows custom connectors; its Free plan does not.
Compose the harness around your decisions.
A crux is a question whose answer would change what you do. Cruxes is a harness as a service for work people and agents do together.
Big decisions are never made alone. Cruxes finds the question you each assume differently.
Shared sessions are in preview.
See it work.
Five real runs on cruxes.io, from the question to a confirmed choice. Silent, with a caption on each step. The model's answers vary from run to run.
Product manager: hold the date, cut scope, or ship and fix?
Sales has promised the date to two customers while design's research is unfinished. Cruxes opens the question of what it would actually cost if those two customers do not get the flow on time.
Recording of cruxes.io
One harness for each way people and agents work together.
Three pairings, three kinds of work, nine harnesses. A crux no harness can settle goes to its DRI, under all of them. Today the Claude Code harness is the one that ships; the rest are labelled by how far along they are.
People with peoplePeople with people · Planning People with people · Negotiation People with people · Creative
What would change each side’s walk-away point?
PlannedWhich choice closes off the others?
PlannedPeople with agentsPeople with agents · Planning People with agents · Negotiation People with agents · Creative
What must hold before the agent acts?
ShippedWhat is the agent allowed to concede?
PlannedWhich direction did the agent assume?
PlannedAgents with agentsAgents with agents · Planning Agents with agents · Negotiation Agents with agents · Creative
Where do two agents’ plans disagree?
PlannedWhich terms need a person?
PlannedWho owns the final call?
PlannedEscalation to the DRI
Shipped: runs today Preview: built, not launched Planned: not built
Person Agent Crux
Two decisions, end to end.
Illustrative cases. The numbers are invented; nothing here is a benchmark result.
A new model, a deadline and an open question
You ask
We're a seed-stage AI startup. Our new model has been scored against the baseline on our internal evals, and our lead investor wants it in the release in 5 weeks. We haven't tested it on customer tasks outside our evals. Ship to everyone, ship to five design partners first, or hold for another eval round?
The crux
Does the eval result hold on customer tasks?
“We haven't tested it on customer tasks outside our evals”Jev's pick: Ship to five design partners first
A counteroffer, a roof and a rate lock
You ask
I'm buying a $1.4M house. The seller countered at $1.43M and won't move on the 21-day close. The inspection found roof wear that could cost $30k to $45k, my rate lock expires in 18 days, and I'm told there is a second offer. Do I accept, counter on price, or counter on a roof credit?
The crux
Is the second offer real?
“I'm told there is a second offer”Jev's pick: Counter with a roof credit and hold the price
How Cruxes works alongside your model.
Questions
What is a harness?
A harness enforces a set of cruxes for one use case. It holds a hierarchy of cruxes and the rules for who or what may resolve them. Cruxes is a harness as a service: you compose harnesses instead of building one.
What is a Directly Responsible Individual?
A Directly Responsible Individual (DRI) is the one person who owns the call on a crux. A crux a harness cannot settle goes to its DRI, and so does any crux that spans more than one harness. The DRI keeps the decision record. An agent may act for a DRI only within limits they set. A recommendation is not permission.
What is a crux in decision making?
A crux is a question whose answer can change what you do. In the Bayesian sense, a crux for a belief B is another belief C such that changing your mind about C changes your mind about B.
What is the difference between a crux and an assumption?
An assumption is something you rely on. A crux is the assumption or open question that, if it turned out differently, would change the decision. Most assumptions are not cruxes, so most can wait.
How do I find the crux of a decision?
Write down the decision and what you believe. For each belief, ask whether learning it was false would change what you do. Keep only the beliefs where the answer is yes, then rank them by how much the decision would move. Cruxes does this for the decision you describe.
What is a double crux?
A double crux is a question that is a crux for both sides of a disagreement. If either side changed their mind about it, they would change their mind about the point they disagree on. The idea comes from the Center for Applied Rationality and the LessWrong community. Cruxes does not replace the conversation. It helps find the candidate double cruxes before it starts, and when there is none, it says so and sends the call to whoever owns it.
Does Cruxes give probabilities?
No. Rank is priority within one decision and one context. It is never a calibrated probability, and the product says so.
Can I trust the output?
Each crux points to the text that caused it, where it can. When detection degrades, the output says so and should be treated as unverified. Cruxes has not published benchmark results yet, and none are claimed on this site.
Does Cruxes make the decision for me?
No. A recommendation is not permission. You resolve each crux by answering, testing, asking or deferring.
How is Cruxes different from a pre-mortem or a decision matrix?
A pre-mortem lists how a plan could fail. A matrix scores options against criteria you chose. Cruxes asks which unanswered question would change the choice. They work together.
Is Cruxes the same as the company called Crux?
No. Cruxes is a different product from the data analytics company named Crux. Cruxes is about the questions behind a decision, not business data.
What does it cost, and is it ready?
Signing in gives you 15 free Cruxes, a total and not a monthly allowance. After that, $29 a month includes 100 Cruxes, then $0.10 for each extra Crux. A Crux is one decision Cruxes surfaces for you. Answering or resolving it is free. Cruxes is in early access, so limits can change; nothing on this site describes a guarantee.