Shadowing Practice: Rethinking Claude Code Best Practices — Lydia Hallie, Anthropic - Learn English Speaking with Video

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I had some technical difficulties during my talk this morning.

So I ran back home and I'm just going to record it from my computer instead.

So hi everyone.

I'm Lydia.

I work on the clock code team at Anthropic and the models have gotten really good lately.

So we have Opus 5 .5, which is my favorite daily driver.

And earlier this week, we also launched Fable 5 .2.

And these models are extremely good at long running tasks and understanding your code base.

And especially Fable was also really good at verifying its own output.

But as these models get better, the way that we work with them in Cloud Code also changes.

So earlier this year, I don't know if you remember, but sessions kind of used to look like this.

So we'd use a model like Opus 4 .5, which honestly for its time was really good.

I really enjoyed working with Opus 4 .5.

But compared to today, it would just stop a lot earlier.

So it would just run for shorter amounts of time.

And we'd also keep correcting it.

We'd keep reminding it to do things, add things like importance, exclamation mark, all these things to our CloudMD file.

And also features like auto mode didn't exist yet.

So we were either approving everything manually or taking the riskier approach with dangerously skip remission.

So we were still very much in the loop as humans.

But as these models got better at taking on bigger tasks, our sessions also changed.

So nowadays, at least at Anthropic, our sessions look more like this.

So we're running dozens of sessions at the same time, running for hours, verifying their own results along the way,

and we even have sessions orchestrate other sessions.

So whereas we used to be in the loop for almost every step

and running one or just a couple sessions at a time, we've now essentially become managers for dozens of sessions.

We also get a lot more done, though.

Now, you may have seen our blog post in October about

how Enthropic went from about 2 ,500 changes a day in May to more than 30 ,000 a day in September.

But this also means that we as developers just have to rethink on what we're focused on instead.

So if you think about our best practices from earlier this year, it was mainly about steering sessions,

approving commands, saying no to certain things or restricting what

Cloud could do, checking the output and also starting the sessions.

So everywhere that we now step out of that loop, something else has to take over.

And this is either the model, the harness, or the environment that it's running in.

So if we are not in a loop to approve every command and we're running so many sessions at the same time,

how can we make sure that the code it's writing is still high quality?

And most importantly, if these sessions are running for hours without our supervision, how can we make sure that they're running safely?

So let's go through that by taking this old session

and seeing what we have to change to get to that end result that I showed earlier.

Well, first of all, let's use the actual defaults we start sessions in nowadays.

So that's not really something you should think about.

So let's update the model here from Opus 4 .5 to Opus 5 .5 and change the manual permission to auto mode.

And Opus 5 .5 is a lot better at understanding your intent and understanding your code base.

So we really don't have to steer it as much anymore mid -session.

And you also no longer have to approve every command

because we started making auto mode the default permission mode back in August.

Now being better at understanding your intent and your code base also means

that we have to rethink the instructions we have in our code base.

So if you followed our best practices from earlier this year you may still have things like important

or never do this exclamation mark all these things in your cloud MD file

but with today's models you really don't need that

and it can actually make the model go off track

so you end up with more tool calls and overall a worse results

so nowadays your cloud md file should only include the things

that cloud cannot see from your code

so for example maybe you have a service that's still using some legacy source somewhere

but it's not directly referenced in the code that's still good to keep in there

but everything else like what stack you're on

or where to look you really don't need that anymore

and we actually have a command for this called dr prompt audit

which makes it really easy to optimize your environment for a specific model.

So if you're on Opus 5 .5 here and you run this command,

it will automatically check your CloudMD and your skills to see what the new model no longer needs.

Now auto mode is a permission mode

that runs a separate classifier on pretty much everything that isn't just reading or editing files in your project.

So it automatically allows commands that it knows are safe, like running tests or installing dependencies, but still blocks commands where it's unsure whether they're safe

and normally that's pretty good normally that's kind of you know what we want

but for example here

if we ask it to ship something to staging

we would have just you know approved the push to our deploy repo

but by default auto mode only trusts this folder and this repo

so it would block that command

so we're back in the loop now the defaults should be good in most cases

but if you still notice that you have to approve a lot of commands, even in auto mode.

The first thing to look at is settings here because you can configure auto mode in your own settings, just in plain English.

And this is what gets sent to the classifier, which then decides whether to reject or allow certain commands.

So here we can just write which repos, buckets, domains we trust and what it should always allow or never do.

Okay, so honestly, this was pretty easy by just using today's defaults, we've already gotten rid of most of our in the loop stuff

because the model took over the steering

and auto mode took over all the approving so getting out of the loop is easy.

But the harder question now is how do we make sure it's okay that we're not there anymore?

So first is keeping it safe, and then also verification.

So let's start with keeping it safe, because everything so far, so upgrading the model and using auto mode, it's just working with a model.

And in most cases, it does what you tell it to do, but that's not a guarantee.

So in a study we published back in August, we tested auto mode versus real people in the loop,

and only about 14 % of people caught a clearly dangerous command.

AutoMode blocked 89 % of them, so it is a lot better at it than we were.

But about 1 in 10 of those commands still went through.

So if you do want the guarantee, you can only enforce that in the harness.

And this is where some of our older best practices still matters, and that's permission.

So, for example, if you have a deny rule for a specific tool call in your project,

clot code looks at this rule before the automo classifier even looks at it in fact

if a tool call matches a deny rule the classifier never even sees it

so having deny rules is still the best way to make sure clot actually never does something

but then how do you know what needs to be a

rule in your project versus what the model can just know

because they've gotten so good at it i think it kind of just comes down to

if clot gets this wrong once can i take it back so if it writes the wrong code, you can still revert that.

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So you can still leave that to the model.

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But if it throws away our uncommitted changes

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or it reads a key that's now in your transcript and you don't want that, that should still be a rule.

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So for example, let's say that we just never want Claude reading our .end file.

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Now by default, Automode is fine with this.

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So it would have just approved it.

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So if you want to make sure that Claude can never read this file, you should just add a deny rule

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and then commands like cat cannot open this file either

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but it's not always that straightforward because sometimes certain commands can have side effects

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so for example let's say

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that npm test here a very normal command it's just a test

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so automote runs it that's fine but

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when the script is running it runs code

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that you didn't write like your dependencies

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or maybe clod runs a script real quick

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that it wrote just to quickly check something so

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if one of those scripts is compromised it could just open

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that same end file or your ssh keys

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and send those to a server you've never heard of right

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and even if we were still there as humans approving everything honestly we would have just clicked allow

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because there's nothing to say no to it's just part of the script

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that in this example case npm test runs and permissions only decide

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if a tool call runs but they cannot limit what it can reach once it's running

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so we want to make sure that these kinds of scripts can still run

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because this is just part of you know how cloud can check its own work running tests

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so we cannot just block npm tests

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but we want to limit its side effects

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so really we just want to limit the environment

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that it's running in so if you're running it locally

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or on your own machine you can run commands like

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that in a sandbox so then you have control over

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which files in a command it can read

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which folders it can write to which hosts it can reach

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and the operating system enforces that also this also applies to everything that command then starts so any child processes

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so on its own that deny rule got checked by claude before the command runs

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but all it sees there is npm test so it doesn't see

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which files that scripts ends up opening but with the sandbox on

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that same rule gets passed on to the operating system

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so now when when

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that dependency tries to open our end file the operating system just doesn't let it

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and by default it can still read most of your machine

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so you'd want to add another rule for your ssh keys

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if you care about that um and it also cannot reach a host

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that wasn't approved but the sandbox only covers the shell commands

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that cloud runs and whatever those start but claude's own files your mcp servers

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and all of your hooks still run outside of it

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so the rest of your session still runs on your own machine

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and everything that's on there

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so ideally you want this whole thing to run somewhere where none of

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that is even there in the first place and

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that is a cloud session

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because there it gets its own machine with a fresh copy of a repo

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and this runs even when we close our laptop

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which is definitely something you want for these longer running sessions

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that run for hours so in this case this automatically gets rid of the end file issue

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because it's not in git and neither are my ssh keys

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or our github token and if it still needs an api key uh you can add

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that as a network secret where it will it will tell you like hey

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i'm missing an api key mid -session um

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so it can use it without actually ever sending it to the model

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and by default also in a cloud session network access is limited to things like package registries and github

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so you have to explicitly add those domains to your environment for claw to to reach other hosts okay

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so with a cloud session we can run these long running sessions even with our laptop closed

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and it keeps us safe

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because it runs in its own environment now it's still good to remember

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that this machine is disposable but the things that leave it aren't

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so a commit that pushed or a message it sent through a connector

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so we still run it in auto mode with our deny rules just commit it into the repo

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so they come along so it could still catch things like a force push

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or a secret and a commit all that kind of stuff

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and beyond just safety we also need to make sure

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that Claude is actually working on the right thing

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so next is verification

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and the nice thing about being in a loop uh like we kind of knew the work was good

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because we'd already kind of seen every change we'd proved everything

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but now if claude works for hours in the background we don't have

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that anymore and we're not really going to read every file at the end either

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so you know say

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that we ask it to move our auth to a new

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api well claude is very good at understanding what we want

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but there are still a lot of small decisions

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that it has to make along the way

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so with the exact same problems you know one run might move it over

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but leave the old api in there or one might move it

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but only for new logins and another one might move it

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but log everyone out and these all look pretty reasonable

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but it really helps to set up these verification points along the way

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so claude keeps verifying its own results and those can be anything

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that comes back as a pass or fail

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so tests a build a screenshot whatever you have

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so now we just want to make sure that we review these verification points.

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They're a lot shorter to review than if we just had to, you know, review the whole change at the end.

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So that's pretty reasonable.

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So if one of these runs would still log everyone out, it doesn't get past that first check,

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and then it just has to find another way.

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And there's a couple ways to set this up.

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The easiest one is, of course, just in your prompt.

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So, you know, you say what done looks like

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and ask it to split that into tasks so they have their own tests.

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And I also like to ask it to show the actual output

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because you weren't there to see it but again prompting is not a guarantee

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that a model will do it so for the ones

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that have to run guaranteed run i would use hooks

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which are just you know scripts that cloud code runs at a specific point

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and those give you a lot of control because you decide

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when they run and what they run and what they check

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so for example every time it edits a file

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we can run our linter every time

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it wants to mark a task as complete we can run the tests for what it changed um

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so you know if it touch our off code or something.

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It has to pass the off tests.

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And when it wants to finish the whole session, we can just run the entire test suite.

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And if one of those fails, it goes, oh, that's still broken.

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It goes back until it passes.

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So it fixes it.

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Now, just one thing, when a test fails, by default, most tools that exit with a one exit code.

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But with a one, that task by Cloud Code just gets marked as completed anyway.

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So make sure that your scripts exit with a two exit code

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because that's what actually sends cloud back to fix it

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so okay now we have one session that i'm pretty comfortable with leaving alone

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so now we can start with a few more of those

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because they've all got their own machine

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so they're you know not all working in the same folder

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and we don't really have to think about work trees too much ourselves anymore

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but then we still start every session ourselves

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and we review every one of them

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and honestly this is already a pretty good place to be

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we are still fully in control over what gets started and

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when we call a task done

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but even there um you know we're still the ones kicking off every session

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and we're still in the loop for all of them

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so i think the most important thing to have in place here now is your ci

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because all of these sessions eventually open a pr

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and your ci runs the same checks on every one of them no matter how

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that session was set up or you know what claude decided to do along the way.

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And if you turn on autofix, we have like CI autofix,

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Cloud can also see when one of those checks fails and then go back to fix it.

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So you're not the one spending your review on things that, you know, a check could have already caught.

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And for some of them, you can even turn on merge when ready.

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So then GitHub merges the PR once all of the checks have passed.

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So you're not in the loop to review.

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But again, that's not the default.

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And that really depends on how risky the changes

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so for example on our team every pr gets reviewed by cloud first

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so not by the session that wrote it

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so it comes with a fresh context

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and also a separate group of agents to just double check every bug it finds

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and then how much we review ourselves just depends on the risk

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so smaller changes like docs or copy they don't need a person so once the automated checks are green

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we're pretty good to go.

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Maybe ordinary product changes just need one reviewer, and then risky changes might need two.

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Now, ultimately, kind of where we see things going, and we're already kind of doing more of that adnthropic,

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is that you're not really starting all of those sessions yourself either.

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Because if you're anything like me, I'm terrible at context switching, so having to manage so many sessions at the same time doesn't always go well.

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So instead, you just have one main session that's your orchestrator

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and you can already see this in things like cloud code projects

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which is still in beta but you just tell it what it needs to be done

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and the orchestrator splits it up and then starts other sessions for each task

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and it keeps track of what comes back so it automatically starts

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and verifies these threads which are just new sessions

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so instead of talking to eight sessions you're just talking to one

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and the main session doesn't write the code itself

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so there you want a model that's really good at deciding what to do

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and judging what comes back a model like fable and

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if something comes back that isn't actually done it just you know sends it back

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so until it's actually done and passes everything

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and the threads need a model that's good at actually doing the work like opus 55

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and you can set those separately so you know one model for the main session

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and then another one for the threads and another benefit is

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that with this setup with cloud code projects specifically we don't manage context anymore that's all done automatically for us

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so we no longer have to think about you know

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when to compact or clear all of that stuff okay so

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if you look back at those old best practices they're all still there but they've just moved

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so the model sears it now um auto mode approves your deny rules

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and the environment restrict what's possible your test your hooks

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and your ci check set and then ultimately cloud can just start them as well

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so almost everything we used to do ourselves is now either the model the harness

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or the environments and we're really just here to start

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that first one and to just review what comes out so

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if you want to try this in your own setup

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i would say just take one thing

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that's way bigger than you normally give claude make sure your ci actually catches the things you care about

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and then spend a bit of time just configuring your environment like it's network access it's secret

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and it's you know setup script and then start in the cloud

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and see where your sessions get stuck and where you're still in the loop

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because that's the next thing to hand over to claude

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i also highly recommend checking out our best practices in the docs as well thank you so much

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37 sentences

Vocabulary and speaking notes for this lesson

This speaking lesson is built on the video “Rethinking Claude Code Best Practices — Lydia Hallie, Anthropic”. The speaker keeps coming back to these words: session, model, command, code, cloud. This video has 286 sentences and 3581 words to shadow. The speech runs for 17:31. The speaker talks fast, about 204 words per minute, so expect linked and reduced sounds. 86% of the words are among the 3,000 most common in English; the rest is worth studying before you start.

Key vocabulary in this video

15 words from the video worth learning, with pronunciation and meaning:

Word	Pronunciation	Meaning
cloud noun	/ˈklaʊ̯d/	A visible mass of water droplets suspended in the air.
auto noun	/ˈɔːtəʊ/	A setting for automatic operation.
loop noun	/luːp/	A length of thread, line or rope that is doubled over to make an opening.
approve verb	/əˈpɹuːv/	To officially sanction; to ratify; to confirm; to set as satisfactory.
default noun	/dɪˈfɔlt/	The condition of failing to meet an obligation.
script noun	/skɹɪpt/	A writing; a written document.
deny verb	/dəˈnaɪ/	To disallow or reject.
guarantee noun	/ˌɡæɹ.ənˈtiː/	Anything that assures a certain outcome.
exit noun	/ˈɛɡzət/	An act of going out or going away, or leaving; a departure.
verify verb	/ˈvɛɹɪfaɪ/	To substantiate or prove the truth of something.
verification noun	/ˌvɛ.ɹə.fɪˈkeɪ.ʃən/	The act or process of verifying.
thread noun	/ˈθɹɛd/	A cord formed by spinning or twisting together textile fibers or filaments into one or more continuous strands, typically used in needlework.
output noun	/ˈaʊtpʊt/	Production; quantity produced, created, or completed.
hook noun	/hʊk/	A rod bent into a curved shape, typically with one end free and the other end secured to a rope or other attachment.
commit verb	/kəˈmɪt/	To give in trust; to put into charge or keeping; to entrust; to consign; used with to or formerly unto.

Phrasal verbs you will hear

Word	Pronunciation	Meaning
come back verb		To return to a place.
take over verb		To assume control of something, such as a business or enterprise, and sometimes by force.
go through verb		To travel from one end of something to the other.
set up verb	/ˌsɛt ˈʌp/	To make ready for use.
check out verb		To record the departure or withdrawal of someone or something (such as guests, employees, books, etc.).
come along verb		To accompany.
come down to verb		To reach by moving down or reducing.
come out verb	/ˌkʌm ˈaʊt/	To be discovered; to be revealed.

Grammar in this video

The structures the speaker uses most, with the exact words from the video:

Structure	In the video
“Used to” used to + verb — a past habit or state that is no longer true	used to look · used to be · used to do
Present perfect have/has + past participle — a past action that still matters now	have gotten · we've now essentially become · we've already gotten
Passive voice be + past participle — the focus is on what happens, not who does it	is compromised · wasn't approved · was set

Pronunciation to watch

The speaker uses 63 contractions and reduced forms, such as we're, don't, you're. Say them the short way, as you hear them.

The “th” sounds: thread /ˈθɹɛd/, rethink /ɹiːˈθɪŋk/, auth /ɔːθ/
The “sh” and “zh” sounds: verification /ˌvɛ.ɹə.fɪˈkeɪ.ʃən/, essentially /ɪˈsɛnʃəli/, shell /ʃɛl/, instruction /ɪnˈstɹʌkʃən/, supervision /ˌs(j)uːpəˈvɪʒən/
Long words — get the stress right: verification /ˌvɛ.ɹə.fɪˈkeɪ.ʃən/, dependency /dɪˈpɛndənsi/, essentially /ɪˈsɛnʃəli/, ordinary /ˈɔɹdɪnɛɹi/, difficulty /ˈdɪfɪkəlti/

How to practise with this video

Listen to the whole video once without speaking and note the words you do not know.
Start at 0.75× speed, shadow it sentence by sentence, then go back to normal speed once it feels easy.
Record yourself and compare with the original, paying attention to words like cloud, auto, loop.

What is the Shadowing Technique?

Shadowing is a science-backed language learning technique originally developed for professional interpreter training and popularized by polyglot Dr. Alexander Arguelles. The method is simple but powerful: you listen to native English audio and immediately repeat it out loud — like a shadow following the speaker with just a 1–2 second delay. Unlike passive listening or grammar drills, shadowing forces your brain and mouth muscles to simultaneously process and reproduce real speech patterns. Research shows it significantly improves pronunciation accuracy, intonation, rhythm, connected speech, listening comprehension, and speaking fluency — making it one of the most effective methods for IELTS Speaking preparation and real-world English communication.

Shadowing technique: read the full step-by-step guide →

Shadowing Practice: Rethinking Claude Code Best Practices — Lydia Hallie, Anthropic - Learn English Speaking with Video

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Vocabulary and speaking notes for this lesson

Key vocabulary in this video

Phrasal verbs you will hear

Grammar in this video

Pronunciation to watch

How to practise with this video

What is the Shadowing Technique?