October 13, 2026Main stage4 min read

Balancing Acceleration and Safety for AI Agents

John Feminella uses a catastrophic payment mistake to explain five controls that make agents visible, constrain their access, and reserve human attention for decisions that need it.

John FeminellaTwo SigmaSVP Architecture

From the conference livestream · 0:50:59–1:09:41 on YouTube. The player starts and stops at this session’s boundaries.

0:51:36 ↗

When everyone approves the wrong thing

The payment was supposed to move interest. Instead, it moved the principal too.

John Feminella opens with his account of the 2020 Citibank–Revlon payment error. An internal workflow used a full-loan-payment operation to calculate the interest owed. The principal was supposed to be directed into an internal wash account, where it would be booked without leaving the bank. Missing settings changed the result. About $900 million went out instead of the roughly $8 million interest payment described in the talk.

Feminella’s reconstruction shows how the settings changed where the principal went. Only the principal field pointed to the wash account; two other required fields did not.

Payment-routing diagram with missing wash-account settings in FRONT and FUND, and PRINCIPAL directed to the wash account.

The diagram at 54:30 traces the misdirected funds through the fields the operators needed to configure.

The disturbing part is that an approval process existed. The software warned that money would leave the bank. That was also what the operators expected: the interest really was meant to leave. Three approvers could accept the warning while misunderstanding the transaction it covered.

Feminella is speaking in his personal capacity. His concern is what happens as agents gain access to systems that can make mistakes on this scale. The approval dialog did appear. The people reading it still did not understand what they were approving. Watch the example at 51:52.

0:56:15 ↗

Make agents visible and review their actual risk

An agent’s behavior cannot be known completely in advance. Neither can a human’s. Organizations still give people access and autonomy, together with controls that let them work effectively.

Feminella rejects three inadequate defaults: isolate agents until they cannot do anything useful, let them act without meaningful restrictions, or put policies in prompts and assume they will enforce themselves. He proposes five controls that can work together without making every agent wait for the same review.

The first is an agent registry. When agents appear as notebooks, chatbots, web tools, and assembled tool servers, the organization needs basic answers: who owns this, what is it for, which tools does it use, and which endpoints does it reach? Those answers support reuse as well as governance. A team cannot reuse a useful agent it does not know exists.

Registration should happen automatically through approved building frameworks, with a manual path where necessary. Requiring every small experiment to pass through an onerous registration gate can drive work into less visible channels.

The second control is risk-based review. A ticket summarizer and a production-deployment agent do not deserve the same queue. Most enterprise agents have a specific purpose, unlike an open-ended coding assistant that does not know what the next user request will be. Declared purpose, tools, endpoints, and applied controls provide information for deciding where human review is most valuable. Spending reviewer time on low-risk requests also leaves less attention for consequential ones.

1:02:32 ↗

Turn declarations into runtime restrictions

The third control makes the declared purpose enforceable. An agent may need several capabilities, but it rarely needs every tool available in the organization. Its author is well placed to specify the few tools needed for its job.

A research summarizer might need web access. A release-deployment agent may have no reason to browse. A blanket allowlist applied to both either blocks useful work or grants unnecessary access. Their different purposes should produce different permissions.

In the managed environment Feminella describes, initialization looks up the agent in the registry. Its policy becomes concrete restrictions on endpoints, hosts, and other resources. The team can operate within its declared risk profile without opening an IT ticket for every routine access decision.

The fourth control is shared evaluation infrastructure. Different agents need different tests, but they also need many of the same capabilities for running and comparing evaluations. A firm-wide foundation lets teams supply the assertions specific to their agent instead of building the surrounding machinery repeatedly.

A model is a dependency that affects the running application. Replacing it can change the agent’s behavior even when the application’s own code barely moves. Evaluations provide a way to detect that change. A central committee approving every prompt edit would slow iteration; shared evaluation tooling gives teams a repeatable way to assess it. Watch the runtime and evaluation controls at 1:04:47.

1:07:09 ↗

Protect the human attention budget

The fifth control addresses approval fatigue. A person supervising many agents can receive requests faster than they can inspect them. Repeated confirmation trains the person to click yes, eventually including a request they should have examined.

Route a request according to the decision it needs:

  • An explicit rule covers it: apply the rule directly, so routine permitted calls can proceed and prohibited calls can be denied.
  • The request needs interpretation: use an independent, conservative classifier to assess it.
  • The ambiguity or consequence needs human judgment: ask a person who has time to inspect it.

This reserves attention for the requests where an approval can actually change the outcome.

The classifier is part of runtime governance, separate from the agent’s own desire to finish its task. This makes the decision enforceable at the point of action rather than dependent on what remains in the agent’s context.

The registry, risk review, resource limits, evaluations, and runtime checks work together to keep that attention available. Feminella’s closing analogy is a car’s brakes: being able to stop safely is what lets the driver go fast. The engineering goal is to give agents useful autonomy with the same confidence that their actions can be constrained.

Full transcript 314 timestamped passages

Machine transcription with reviewed terminology and names. Some recognition errors may remain. Timestamps refer to the original livestream.

0:50:59Hey,

0:51:01All right, I precariously balanced my water over there.

0:51:04My name's John Feminella.

0:51:06I work on AI architecture and engineering at Two Sigma,

0:51:09which is a hedge fund here in New York.

0:51:11Before I get too far into things,

0:51:13I have a legal disclaimer slide that I have to show you

0:51:16that says two things.

0:51:18One, I promise not to sell or market or offer you any securities

0:51:21at any point in this talk.

0:51:23and two, everything in this is my own opinion

0:51:25and not the opinion of Two Sigma.

0:51:27Thanks for indulging me.

0:51:28If I don't say those magic words,

0:51:30the 5G microchips implanted in me will explode.

0:51:35So that slide is a good example, actually,

0:51:37of how our industry is regulated.

0:51:40And as a regulated company with lots of controls,

0:51:43I think one thing that's always interesting

0:51:45is to explore what happens when controls fail

0:51:47because that gives you a good idea

0:51:49about why the controls were there in the first place.

0:51:51And so I'd like to tell you a story about that by showing you another legal slide.

0:51:56After August 2020, a very interesting contract clause suddenly started showing up in a bunch

0:52:02of commercial loan agreements.

0:52:03And this clause essentially tries to prevent a certain scenario from happening.

0:52:07And it's complicated, but I'll explain it like this.

0:52:10Let's say that you're a lemonade stand business, and you borrow money from a lender to capitalize

0:52:15your lemonade stand.

0:52:16and the bank that's overseeing that transaction,

0:52:19that's in the middle between the borrower and the lender,

0:52:23sends the lender all of the money that you owe in a catastrophic mistake.

0:52:29You'd probably be mad and want the money back,

0:52:31but the lender might also say,

0:52:33no thanks, you paid us back and we're all good,

0:52:35so we'd rather keep the money.

0:52:37Something like this happened in August 2020.

0:52:40Revlon, the cosmetics company, had borrowed money under a big 2016 term loan.

0:52:45And that loan was split up into a bunch of pieces across 300-plus lenders, hedge funds, credit funds, CLOs, other banks.

0:52:53And in the middle is Citibank, the administrative agent.

0:52:56Being the agent in this kind of transaction means that you're performing the plumbing that connects the borrowers with the lenders and managing the lifecycle of the loan.

0:53:05So in this transaction, Revlon pays Citi, and then Citi pays the lenders.

0:53:09And Citi's not lending its own money.

0:53:10It's just in the middle, moving people's money around.

0:53:13So here's the plan for August 11th, 2020.

0:53:17Revlon would pay about $8 million of accrued interest to both groups,

0:53:21and the lender's principal would roll into this new facility.

0:53:24That's an exchange of paper, not cash.

0:53:27So the remaining lender's principal would stay put,

0:53:29and the idea here is that only interest should be going out.

0:53:33Principals should not be moving at all.

0:53:35And the bank had a piece of internal processing software called FlexCube.

0:53:40Isn't that a fun enterprise software name?

0:53:42in FlexCube, the easiest way to do this kind of transaction

0:53:46is to pretend to record it like Revlon were paying off the entire loan.

0:53:51And that triggers the correct interest payment calculations to everyone.

0:53:55You can probably guess what's about to happen next.

0:53:57So you're supposed to send the principal portion

0:54:00to an internal WASH account that you own as the bank

0:54:03so that it's booked and recorded correctly,

0:54:06but it never leaves the bank's perimeter.

0:54:08So keep your eye on that WASH account.

0:54:10What was supposed to happen is that the boxes labeled front and fund and principal should

0:54:16all include the WASH account number and should all have a check box checked next to them.

0:54:21So unfortunately it turned out that was what needed to happen, but for various arcane reasons

0:54:27the boxes were not checked.

0:54:28And although FlexCube pops up a warning notification that says, uh-oh, money is about to leave the

0:54:33bank, are you sure you want to do this?

0:54:35That was correct.

0:54:36Money was supposed to leave the bank because they were making the interest payments.

0:54:39So the three approvers who were supposed to approve that looked at it and said, yep, that's

0:54:44the right thing that's supposed to happen.

0:54:45And although that warning notification popped up, the human operators carrying out the transaction

0:54:50overwrote that.

0:54:52Remember, Revlon was making that interest payment.

0:54:54So the principal never went to the wash account.

0:54:56And instead, Flexcube sent the entire outstanding principal of the loan to all of the 300 lenders,

0:55:02about $900 million instead of $8 million.

0:55:06So every lender got the amount that they would have been owed

0:55:09if Revlon had paid the loan in full,

0:55:11but Revlon didn't want to pay off the loan.

0:55:13It wanted to hold on to its money.

0:55:14That was a great deal for the lenders,

0:55:15because remember, Revlon was in trouble at the time,

0:55:17so its loans weren't trading at face value,

0:55:19and getting all your money back on a deal

0:55:21that you thought was only worth 60 cents on the dollar

0:55:24is a great deal for you.

0:55:26So they didn't want to give the money back,

0:55:28even after Citi called them and said,

0:55:30please, that was a mistake, give us the money back,

0:55:32and their argument was,

0:55:32we shouldn't have to give the money back

0:55:34because you paid us in full, and that's how loans work.

0:55:37You eventually pay them back,

0:55:38and just because you paid it back at a different time

0:55:40than you were supposed to doesn't mean

0:55:41that we should have to give it back now.

0:55:43And so to prevent that from happening,

0:55:46commercial loan agreements everywhere started

0:55:47including a clause like that one.

0:55:49So what does a payment error at a bank

0:55:51have to do with AI agents?

0:55:53Well, the bank had this procedure, it had these controls,

0:55:56and everybody did what they thought the right thing to do was.

0:55:59That's the problem I want to talk about for the rest of this talk.

0:56:01Every day we're giving real agents real autonomy over systems like FlexCube.

0:56:06And how do we prevent accidents like that one from either from happening without locking everything down or just hoping we'll get lucky that they won't happen?

0:56:14So here's the crux of the issue.

0:56:16You can't really know in advance what an agent will do, right?

0:56:19There are these non-deterministic systems.

0:56:21And that sounds scary until you remember that humans are also non-deterministic systems and they're going to make mistakes too.

0:56:27And so most firms don't choose to say, well, in order to reduce the risk of humans making a mistake,

0:56:32we're going to lock them in rooms and prevent them from talking to each other,

0:56:34and they're all going to double-check everybody else's work.

0:56:36We allow them a certain amount of autonomy along with a certain amount of controls.

0:56:41So we give them boundaries, visibility, and we equip them with systems and controls

0:56:46that let them do their jobs effectively.

0:56:48So in this sort of model, safety and innovation are not opposite ends of a spectrum

0:56:52that you must trade off on.

0:56:53They're things that you can have at the same time.

0:56:56So I think you can have your cake and eat it too.

0:56:58And when we were thinking about what controls we wanted to apply to agents,

0:57:01we also looked at some approaches that didn't work for us.

0:57:04We don't want to sandbox or lock down everything,

0:57:06because a sandbox with no real access to systems is safe,

0:57:10but it's not very interesting or useful.

0:57:12If you let agents go wild and do whatever they want,

0:57:14that's maybe powerful and freeing from a cognitive perspective,

0:57:18but the isolation is very weak there,

0:57:21and that approach is generally not suitable for highly regulated enterprises.

0:57:25And then if you just have policy documents that agents look at or that are part of your

0:57:31specification for the prompt, that's also not very enforceable at runtime.

0:57:35You can't guarantee that that will be part of the enforcement controls.

0:57:38So what did work for us was thinking about what mix of controls would get us both safety

0:57:43and innovation at the same time.

0:57:45So how do we provide boundaries and stop problems but don't hinder folks from operating correctly?

0:57:51So we have a number of these controls, but today I'll talk about five of them.

0:57:55When I say controls here, what I mean are the guardrails and shared capabilities that let teams move in ways that don't hinder what they're trying to do.

0:58:04And we don't want to reach some chasm that we need to cross to let people get their work done and then make everyone wait while we build a bridge to get there.

0:58:15So these controls are composable.

0:58:17Each one does one job.

0:58:19And then together, they let us run agents with real autonomy at an appropriate level of safety.

0:58:26So the first problem is that agents were showing up everywhere.

0:58:29We have big teams with lots of agents running.

0:58:32We have small teams with a few.

0:58:33We have individual people running stuff in an uncontrolled way.

0:58:37And these come in every shape.

0:58:38Could be random chatbots.

0:58:39It could be MCP servers glued together in this Frankenstein hot

0:58:43podge.

0:58:44It could be cool notebook experiments.

0:58:46It could be really useful web tools for folks.

0:58:48But it's hard to answer when you look at that a few simple

0:58:52questions, like who owns this?

0:58:54what tools does it have access to, what should it be doing, what should it not be doing.

0:58:58And if you can't answer those kinds of questions, if you can't govern them,

0:59:01then you can't really also reuse that.

0:59:03So you're tempted to build multiple solutions to the same problem

0:59:08if you don't know about what exists already.

0:59:10And then the firm can't also govern those in any kind of legible way.

0:59:14So one thing the firms sometimes do here is add some kind of gate.

0:59:18Like don't let anything run until everything is registered and approved

0:59:21and has gone through this very onerous process.

0:59:24And that sounds safe, but if you look at what it does to the work,

0:59:27every idea, even some simple no-pick experiment,

0:59:30is going to wait in line behind something that's really risky.

0:59:34And we don't want to subject everybody who's given the diversity of agents

0:59:39to exactly the same process.

0:59:41So most people are going to give up,

0:59:42or they'll just get pushed to some shadow IT,

0:59:44less governed path that is less visible,

0:59:48and then we don't get to see anything at all.

0:59:50So that's what motivated the first control is an agent registry.

0:59:53You can't govern it, you can't see, so the agent registry makes agents legible, and it

0:59:57registers, retrieves, and discovers the key

1:00:00facts about agents that we want to know for any agent.

1:00:04So those are things like which tools it declares, what endpoints it's going to talk to, which product does it belong to, who owns it.

1:00:10And humans, other programs, other agents can then use the agent registry to decide what's available at the firm, whether that's useful for them, and to go use that as a source of truth for other questions.

1:00:23So this doesn't require extra effort on your part.

1:00:25It just happens when you use one of the firm's approved agent building frameworks.

1:00:29It's automatically registered.

1:00:30All that information is recorded there for you.

1:00:32And if you want to do a manual registration, you can certainly do that.

1:00:37So the second problem we have is that now that we've got all these agents doing all

1:00:42these things, we quickly notice that what they're doing is really different.

1:00:45And that means our agents carry really different risks, right?

1:00:49So a thing that summarizes Jira or linear tickets is really different than a production

1:00:55deployment agent that can touch a running system.

1:00:57And if we try to use the same review process to cover all of these agents, then every agent

1:01:03is waiting in the same queue for weeks for human review.

1:01:06And if people are going to route around slow processes, then we wind up in the same situation

1:01:11that we had before.

1:01:12So again, you might be tempted to say the answer is something like really detailed,

1:01:16heavy manual review by all of these different constituencies. Again, that feels safe, but now

1:01:21we've got a trivial summarizer waiting two months for the same sign-offs as an agent that is touching

1:01:27production systems. And most of the good agent ideas, most of the ones that have value right away,

1:01:33start out as small experiments, and you don't want those people to wait in the same line as the stuff

1:01:38that's touching production right away. So the reviewers are drowning in these low-risk requests,

1:01:43and the high-risk ones have to share that attention pool.

1:01:46So we don't want to trade away that speed if we can help it.

1:01:49So again, because not every agent needs the same review,

1:01:52and because most agents are purpose-built rather than open-ended,

1:01:56and when I say open-ended here,

1:01:57you can imagine coding agents like Pi or Claude Code.

1:02:00When you open them and you start typing,

1:02:03Claude Code or Pi doesn't know what you're about to ask.

1:02:06It doesn't circumscribe its purpose in any particular way.

1:02:09But most of the agents that are deployed in enterprises

1:02:12do have very specific purposes. When you're engaging with that agent, it's to do something

1:02:17specific that's well known and well understood. So they have a very specific reason for existing

1:02:21and a very circumscribed purpose. And you can tell these agents apart from each other by looking at

1:02:26what they declare up front, their tools, the endpoints they access, the controls that are

1:02:31applied to them, etc. So the third problem is that if you know about your agents and what they're

1:02:39doing, you'll quickly notice that many agents don't talk to each other.

1:02:43Sorry, they don't talk to just one thing or in just one capacity.

1:02:46The more open-ended the agent is, the more it looks like a Claude Code or Pi, the more

1:02:51it can do a variety and a diversity of different things.

1:02:55Call an internal API, run a tool like a web search, that sort of thing.

1:02:59And each one of those is a different opening, a different door to a different kind of risk.

1:03:03And if you give an agent an entitlement for a role account, then it can do a lot more

1:03:08damaged than something that's just going to read a public web page, for example.

1:03:12So the question is not, can this agent do X, but what's the granularity that we need

1:03:17to solve for for the agent to act successfully?

1:03:21And again, one tempting answer is to kind of be heavy-handed here, or to give every

1:03:25agent the same short allow list of stuff that's safe to do, and then block everything else.

1:03:31That's safe, but it's also useless.

1:03:33An agent that can't search, or can't call an API, or can't do any of those things without

1:03:38asking somebody first can't really do the work that it was intended for. And then

1:03:42teams either give up on those agents or they find a way around the wall and

1:03:46both outcomes are costly. So a wide kind of blanket block on everything trades

1:03:51away the innovation that we want to preserve and avoids making a real

1:03:55decision about risk. And as author John Shedd wrote, a ship and harbor is safe,

1:04:00but that is not what ships are for. So the fix here is to let agents declare

1:04:06their purpose upfront and say what tools they're going to use or what tools they

1:04:11need access to. So in the second column here we might say that a research

1:04:17summarizer is going to be allowed to use a web tool to access research, but for a

1:04:24release deployer agent we're not going to allow them to do that because they

1:04:28have no reason to use that tool. And so if they try to ask for it they won't get

1:04:32it by default. So we don't need to make this kind of decision for every tool.

1:04:35the agents just have to say which tools they want.

1:04:38And you're, as the agent author, you're in the best position to say,

1:04:42I need these four things out of the 500 that are available.

1:04:47So the way we need to enforce that is that when agents run in our managed environments,

1:04:52they look at the registry that we talked about before

1:04:55to look up what policies apply to it at initialization time.

1:04:59And that policy gets translated into enforceable statements,

1:05:02like which endpoints are you allowed to access, which hosts are you allowed to access,

1:05:07what other types of resources are available or not available to you.

1:05:10And in this way, nobody's writing a ticket every time they need to change the access.

1:05:15Nobody's going to talk to IT or some other group outside of your team.

1:05:20As long as you conform to the risk score that we talked about before

1:05:24and you're in the agent registry, you're governed, you're approved.

1:05:27So this is how we keep the cost to teams really low for deploying, building, running agents.

1:05:34And the same control architecture works in a variety of settings.

1:05:37The next thing we noticed was that teams were building a ton of different ways to evaluate agents,

1:05:42and every stack looks different, and some teams don't build anything at all.

1:05:45Sometimes you build this really detailed stack for how your models work.

1:05:49Sometimes there's nothing.

1:05:52And I think in general we'd be upset if teams were not writing unit tests, right?

1:05:58And we consider evals to be kind of the same thing.

1:06:00If models are changing, that's like a runtime dependency that your application has.

1:06:04And if your agent is going to change models, it doesn't know without the evals what's going to happen to its outputs and to the quality of those outputs.

1:06:14So, again, one tempting answer here is let's have some kind of central evaluation methodology

1:06:20that waits for a full eval suite and a committee sign-off.

1:06:24But now every prompt tweak, every one-line change is going to sit in that same queue.

1:06:29So we don't want to put more decisions on more reviewers for things like that.

1:06:34We don't want to trade away that iteration.

1:06:36So again, you wouldn't ship software without unit tests, so agents need evaluations for

1:06:40the same reason, and we want to provide the stuff at the level of the firm that's going

1:06:46to be the same for everybody.

1:06:47So Team A writing evals, Team B writing evals.

1:06:50They're both going to have many of the same features.

1:06:52So we want to have one shared approach to how we do evals, and have the shared approach

1:06:57be something that's run by the firm and available to everybody for doing their evals.

1:07:01So that covers all the common parts of evals, and all you've got to do is just write what's

1:07:06true about your agent.

1:07:09And finally, maybe you've had the experience of being asked to approve lots and lots of

1:07:13individual agent actions when there's a human in the loop.

1:07:16So that's fine on a small scale, but once you're operating agents in parallel or in

1:07:20production, this becomes completely onerous and review requests come in faster than anybody

1:07:26can be expected to approve them.

1:07:28After the first few times this is happening, you succumb to review fatigue where you just

1:07:32see yes, yes, yes, yes, yes.

1:07:33and eventually you click yes on something that's activating a nuclear bomb.

1:07:38So you don't want to click yes by reflex, but that's going to happen inevitably.

1:07:43One recent example of this is earlier this year, a director at an AI research lab

1:07:47told her open claw agent to suggest emails to delete from her inbox and wait for her approval.

1:07:52But her inbox was so large that eventually the agent compacted its context

1:07:56and lost the part that said, wait for my approval.

1:07:59And then it deleted hundreds of emails and didn't stop when she told it to stop on her phone.

1:08:04So again, you might be tempted here to make a human approve every action, but that's not

1:08:07the right way to do it.

1:08:09A better approach is to let these independent, conservative classifiers make decisions about

1:08:15routine calls, and then send a person only the requests that are most important, the

1:08:20ones that are most likely to make a difference.

1:08:22If you're saying yes, 99.99999% of the time, then that's probably just a rule that the

1:08:28agent should follow, not a request you need to ask the human for permission for.

1:08:31and the stuff that's unclear or ambiguous or potentially dangerous, yes, surface that to a human,

1:08:36or if it's definitely just dangerous, deny it outright. So this is a way to not have to do all

1:08:43the review work all the time. So we want to take the same approach for both explicit,

1:08:48when explicit rules apply, we want deterministic fast paths. When explicit rules don't apply and

1:08:54there's some ambiguity, we want a classifier to do that work instead. So putting those five pieces

1:08:59back together. You create a registry so that every agent is visible from the day it's created.

1:09:04You score each agent so human review goes in the right spot. You run agents on guardrails so that

1:09:09they only touch what they need. You share evals and metrics so everybody is reaching the same bar

1:09:14without having to reinvent the wheel. And then finally you govern your runtime to make sure that

1:09:18classification happens there and not somewhere else. So each of these controls works together.

1:09:24So I'll leave you with one question.

1:09:26Why do cars have brakes?

1:09:28It's not just so that you can stop, it's so that you can go fast and stop safely.

1:09:33So controls for our agents work the same way.

1:09:35Thank you very much.

1:09:37I'm John Feminella, and I hope you had a good time.