Is there anywhere I can find a matrix of what services are emulated and how complete that emulation is? I tried the docs but just ended up going round in circles.
Pass rates from the release's scores.json (commit 7753983), joined with the eval suite's manifest.jsonl. Tests = behavioral checks touching the service. All = overall pass rate. Happy/Reject = valid requests vs. requests AWS should refuse. Ctrl/Data = control plane vs. data plane. Solo/Integ = single-service vs. multi-service checks. Wire# / Wire% = count and pass rate of recorded request/response replay tests (a test passes only if every call matches).
I believe AWS already autogenerates their API clients (e.g. boto3) based on some authoritative internal service api spec so I imagine that spec could be used upstream of this tool as well.
Except, this is not defined in schemas, this is merely defined in prose around the documentation.
So your Rust API is full of Option, and it gets really annoying when you're testing things like say Bedrock, which takes 10 minutes, and then fails because what you submitted 10 minutes before doesn't match their schema.
I understand this can be fixed by reading the documentation in more detail, but it has gotten so verbose, and sometimes you just want to start something.
Yeah whatever they did internally to get service teams to actually adopt AWS Config ~5 years ago needs to happen here or it’s going to get stuck with marquee services and that’s it. Especially given this is a much much larger ask of each service.
I mock (ask Claude Code to make something run in a container) my own AWS services today for CI and development. I'm excited to learn more about how AWS uses it and hopefully use this for CI and development.
Until the plan changes, which at some point, it will. Comment is still appreciated for what it is.
Edit: Comment is in the spirit of "it gets tiring to build on sand which is at the whims of corporate management folks far disconnected from the actual work." If someone is asserting "this will stick around," words are insufficient, words are free. Show me the contract, show me the penalties for failure to abide by the assertion.
Amazon team killed the Copilot CLI[0] which I thought was the single best thing they ever did for AWS infra. Made it tolerable to deploy on AWS; still salty about this one.
Google builds up a product over time and abandons it. This is annoying for long term adopters.
AWS has a habit of throwing a bunch of products at the wall, but only bothering to maintain & build up a few of them. This is annoying for early adopters.
Azure on the other hand. Will throw products out, ensure they are never consistent with other offerings on their platform, and then deprecate it from under you while promoting the same thing with a new name.
I think there was some truth in this in the early days of Azure (and all clouds) as the companies were looking to work out what cloud services were really needed. I don't see this as much any more though esp when a services makes it to GA they have published commitments for service availability and API compatibility. (I was in Azure for 10+ years so definitely let me know if you disagree)
Yeah I disagree. First of all, Azure is mostly garbage so avoid it if you can. Second of all, Azure deprecation follows Microsoft's general policy of deprecation which is The Fadeaway Policy. Don't publish anything publicly about it, gut the team to go work on something else, transfer the service to be one of 6 dozen other services some random offshore team is "maintaining", experience enough outages and trouble and during every support call they nudge you to move to something else, but the service is "totally not deprecated" because we haven't gotten a memo that says that, but we're only doing "security" fixes now. wink wink, nudge nudge.
Fine to disagree - but it would be better to share real insights rather than just blanket statements. Sounds like you have had some bad experiences - maybe you could share more?
Let me quickly compile a list of the last 700 failing bicep deployments with an “Internal Service Error” or No capacity errors along the all the no-op idempotent puts that take 30+ minutes for some reason, the broken networking system all up, the constant support advise to move to different regions, except half the things you use are not in that region, or the constant advice to just delete everything and start again or the half docs half marketing fluff docs. Azure only exists because large enterprise looks at a list of checkboxes before signing a contract. No reasonable person should ever use that garbage unless you’re offered deep discounts to do so, and even then, limit your usage to things you can migrate easily whenever the discount expires.
And Azure will send you an email every day about how you need to migrate X to Y without any way for you to know where those instances are or how to find them.
You're certainly not wrong. But in the wake of Localstack's changes, the landscape has been full of slopware and low trust anyway. I don't think this is worse, for now at least.
Nothing personal, but unless you can link us to a public announcement made by Amazon, your statement is worth less than nothing.
Official statements made by a company are still poor representations of their current business plans, and don't mean anything 3 months later (no matter how much they pinky promise). But a HN post isn't even that.
Additionally Swami, our SVP of AI blogged about it separately and our CTO is tweeting about it - which is more than a number of products get in terms of coverage.
I didn't mean announcing the tool, I meant an announcement committing to the maintenance/support that users like the GP poster were looking for. My bad on describing that clearly, I'm gonna get clowned on in the comments and I'm not turning this around.
I understood what you meant. I was just trying to add evidence to support my claim that it was a real product and would be maintained. And yeah, votes on comments can be fickle.
I think one thing that concerns many people is that this looks like AI slop, which it clearly is according to the blog post.
I think this is a super interesting direction, but how can we trust the accuracy of this simulator? Agentic loops are great and all, but they can still miss plenty of things.
Or maybe a better question: where is the accuracy of this simulator going to be guaranteed enough that we should trust it?
To me, something like this is actually what vibe coding thrives the best at; tight, looped, easily verifiable, test-driven dev work. In fact, this is probably the field it can do with little or no intervention, if you're willing to waste tokens.
Is it? How is it verified that this catches all the potential edge cases of interacting with AWS? Or is handling all the edge cases of AWS not in scope?
Like, what am I actually getting here? Is it just happy path operations being correct here?
In the near future, every case will be a real edge case and every one will be a guinea pig.
The border between AWS and AWS emulator becomes fuzzy. And the users of AWS will be agents as well. A completely offline emulator will save a lot of resources and could be a great training ground for more focused (offline) models.
Back in the day, we assumed that when a major company open sourced code, that code would have problems. We invented all these things like ‘issues’ to deal with this.
GP statement still stands, actually being strengthened. This blog post doesn't even mention nor seems to care about maintainability or long-term support or anything that users will care about. Only talks about how cool the team is and how amazing they're at using AI, multi-agent workflows, and this kind of bs. It's funny how author talks so much about testing when they themselves also boast how they haven't written or reviewed any of the code.
In my experience Floci has been the epitome of vibe coded - huge amount of changes, with things breaking randomly between releases. Moved away from it as soon as I could. Still better than Localstack :)
I didn't have a good experience with test containers, but perhaps it'd work better with fast starting containers. We run our test fixture with compose, and have the tests manage their data in isolation - so we don't pay the startup penalty in our test suites.
I think I'd trust this project at least as much as Floci. Embedded Rust mode also looks very interesting for us.
I only use Testcontainers with "explicit" tests (do not run by default in CI; must be run explicitly). This lets agents exercise the integration with a realistic fake locally, but does not incur the cost in CI nor for any dev unless they run it explicitly (usually also with a category so it's explicit + category filter)
Not really. I was trying to use their own Q AI to help me get something set up and it was constantly wrong about what screens to go to, what was on the screens etc... If their own AI doesn't understand AWS, I don't have confident this will either.
No docs site linked on the GH. 3 weeks old. Blog post talks more about the process than the tool and opens with:
> How we built the agents that built AWS Emulator
> Thousands of autonomous AI agents wrote every line of code in AWS Emulator, a new local emulator for AWS now available for download.
Feels more like a science experiment than a product from that announcement.
Doesn't feel like a real product. But I also didn't look very hard for docs; I kind of expect it to be linked on the GH in the site and have a nice `llms.txt` for me to give to my agents.
Sure they are, but they could have polished their product and showed some love by configuring the repo details and put the website there. Did you look at the blog post as well? Does it look like a product that some team there loved and will care for? Or the output of some exercise for some enterprise content?
This post https://www.aboutamazon.com/news/aws/how-autonomous-ai-agent... doesn't set the right tone for me at all and it has nothing to do with agents and everything to do with the lens of looking at this as a science experiment instead of a real enterprise tool.
> they could have polished their product and showed some love by configuring the repo details and put the website there
This feels like such a weird nit-pick when AWS is criticized for not moving quickly enough. Why should I care if there's a link in the side bar, when there's plenty of links in the `README`? If anything, I'm happy that there's alternatives to Localstack that are supported by AWS themselves that I can begin incorporating. They have a well written `README` that I can start working with and a User Guide to get me started. What else could I want?
> Did you look at the blog post as well?
I did.
> Does it look like a product that some team there loved and will care for? Or the output of some exercise for some enterprise content?
Do you even have the grounds to cast judgement like this when you admittedly didn't even look hard enough?
I looked, but you're mistaking my critique here: I value polish.
This lacks polish.
Small details like getting your GH repo set up for a public audience. Lacking. Compatibility and support matrix clearly advertised? None.
If this public facing artifact exhibits a lack of care and love, what does it say about the code? I am all for vibe coding and agent software factories, but then the humans should show some love with all of that extra time saved.
You might want to reconsider how you present the critique then, because that's not how your root comment came across or any of your subsequent messages, especially when engaging with (presumably) actual AWS employees in this thread replying to you.
Do you agree that there's a polish here that shows a team's pride in that work that is clearly missing in this work?
> ...especially when engaging with (presumably) actual AWS employees in this thread replying to you
??? You and I are the customers. What even is this statement? Are AWS employees our benefactors? Wow. I do not care if their feelings are hurt because this "product" clearly shows a lack of polish and love.
> Do you agree that there's a polish here that shows a team's pride in that work that is clearly missing in this work?
No and I think the inverse is also possible and if anything more likely. You can make a website look really pretty, really easily and have the product still suck. This is "product as a slide" in a new age where making visual eye candy with AI has never been easier.
> I do not care if their feelings are hurt because this "product" clearly shows a lack of polish and love.
The point isn't about hurting feelings. The point is about providing critque and feedback based in reality, not based on "vibes." You're trying to gatekeep people releasing software because you dont like the way they're launching it lol.
If your complaint is about polish, you’re a very poor writer. It should not have taken this many replies to get that point out. But regardless of your communications skills, I disagree - this product looks fine for something released at this stage.
There's a right way and a wrong way to assign a website URL in GH.
The team didn't even take the time to review these small details of the repo, you know, by editing the repository details to place the docs URL there.
I mean, I don't know about you, but I feel like I still like to see people care about the stuff they produce and missing something as basic as the repo website URL in GH settings shows a lack of polish and love.
> - Resource-based policies, such as bucket policies
> - AWS KMS key policies
> - Access across AWS accounts or across AWS Regions
> - Any other security control
> Some services in the emulator evaluate IAM policies for IAM users and roles that you create in the emulator, but not the same way as AWS. The emulator never denies a request signed with its own key. It doesn’t check AWS KMS key policies or Amazon S3 bucket policies. It also doesn’t support calls across accounts or Regions. So a request that AWS denies might succeed in the emulator. A request that AWS allows might fail.
This is a shame because I'd love for the official AWS product to be better than e.g. ministack and localstack on this, which will go some of the distance. I think because the agents were only building on the public API surface, it's hard to build this part. But they should've tried and let the agents read whatever policy engines AWS has. Or maybe it's a way to prevent someone from trivially running aws-emulator as AWSaaS?
Say whatever but without AI and agents, no one in AWS would have thought of building this given the huge amount of services they have. Humanly, possible but very very costly. Not saying has not happened before but fakecloud and localstack etc? That moat is gone.
I am shocked TBH that this is the new normal. Agents writing code in one of the most difficult to use languages. And ugly as well TBH, it pokes into your eyes. Subjective I know but it is a horrible language for humans.
> Agents writing code in one of the most difficult to use languages
Arguably, languages with strong static guarantees are exceptionally effective for LLMs since they're much quicker to provide feedback to the LLM than a dynamically typed language (which only fails once you actually run it - often several times to find the actual problem). You also get very well-designed build error messages rather than having to parse unstructured stderr output, etc etc.
If I understand this correctly, it means I can point my entire CDK project to the emulator and test a `cdk deploy`?
I'm curious just how realistic the "internal" behaviour is emulated. It's been a while (since I got my stack working and I just don't like touching it now...), but I recall it being a real pain that sometimes odd, sometimes inconsistent things happened with setup and teardown (even through Terraform), which led to long timeouts if you did things in the wrong (but seemingly valid) order.
> I'm curious just how realistic the "internal" behaviour is emulated.
It seems like some reasonable shortcuts are taken, like services reading from each other's states directly instead of using APIs [0]. But then it will go so far as to run an in-process NodeJS emulator for lambda functions, and give it a shim so the code it runs can call other emulated AWS services using the main router [1].
Fellow Amazonian here. Want to say that I’m grateful you built this and it has tremendous value if pulled off well and properly maintained.
Agentic development is all about closing off a system as much possible, then mocking up or simulating any inputs or dependencies that cannot be closed off. At that point, you let Claude crawl over the system and do its thing.
This inevitably runs into problems with infrastructure and any tools that help mock up those interfaces will be tremendously valuable. Thank you!
> We’ve had our agents build many versions of this emulator as we’ve refined the building machine.
I'm curious how many versions they made and the token spend on each one. There are a lot of failure modes to projects like these (e.g. gas town endlessly developing itself). Is this more of a sly marketing stunt or a real indication that this methodology is practical and economical?
FYI I checked out the repo. `du --apparent-size -h` output for some dirs:
I had a good time using its SDK inside my integration tests. I'll give a couple months before even moving to this because it's weird how similar both projects look like.
EDIT: After checking AWS's project I'd say stay away from it, looks heavily vibe slopped.
claude is the second-most frequent author in that fakecloud repo, what makes you say that's not vibeslopped either? This is 100% the perfect usecase of using a swarm of agents. It's a bounded, and easily-verifiable with property testing/mitm proxying, task. If you think in November 2026, agentic engineering is equivalent to vibe coding, you need to update your priors
I remember asking this to one of the evangelists when AWS first came out, how do I run this locally. This was during the times where we actually tried to get all the .NET and C/C++ docs locally.
AFAICT there isn't a quick way to reset state other than restarting the process - in other words it probably isn't a drop in replacement for https://github.com/getmoto/moto for running tons of tests where the state of the mocked AWS system needs to be reset after each test. Hopefully they will implement a quick reset functionality; multiple accounts and full org APIs emulation would be nice too.
AWS already models all their services with Smithy, the specification language they created. Their API clients are all generated from Smithy, and the emulator seems to have been built using the Smithy specs and comprehensive integration testing against the real APIs. Using the spec ensures they hit every variant and optional field of every endpoint, unlike Floci and Ministack that only implement the more commonly used ones.
Thank the maker!! I was not having a good time with LocalStack, only an average time. Definitely have to try this out. I need the environment to survive a reboot.
Localstack is no longer free and if you’re using it commercially you need to pay for a license. The free plan explicitly states that it is non commercial.
Looks like this was ~100% generated with Claude within the past month. Interestingly it still has a lot of occurrences of words that Opus used way too much pre 5.5, so maybe they're not using the latest models.
I mean, if they're using it internally then there's probably a TON of context you can feed these things to converge on approximately-correct solutions. Certainly it sounds like it can be a much better alternative to Localstack/Floci and friends.
This is no doubt made possible by an agentic coding loop. If you have the right checks in place, it can be easy to emulate existing software.
I was able to create a TV emulator at my work with a mostly independent agentic loop, because we have a lot of tests to examine a smart TVs APIs. The agents mostly just need to make the tests pass.
"expressing a personal opinion, bias, or subjective viewpoint in a context—such as a news report—that is supposed to be strictly factual and objective."
How does the title do any of the above that makes it editorializing?
They wouldn't include it otherwise the binary would be comically large since (as one might guess) there are a lot of knobs involved in pricing AWS things. Just downloading it takes several minutes, served from S3
https://github.com/opencost/opencost/blob/v2.5.3/pkg/cloud/a... is the source URL, and while I haven't been in the opencost ecosystem for a while, I'd guess there's a non-zero chance you could legitimately just ask it to price your aws-emulator resources. I am pretty sure there is a terraform/opentofu integration, too, although I don't this second know if it is within opencost or is a separate project
~30K commits in 3w; quality software for sure. Is someone trying to get promotion by tokenmaxxing? Ironic or unlucky coincidence or competitor(s) misdirection, that, only 2w ago, Amazon published memo discouraging AI abuse?
It's funny to read AI-generated documentation that is the result of a prompt instructing the LLM to be as terse and straightforward as reasonably possible. The agent was probably told to conform to ASD-STE100.
It's better than a lot of AI-generated documentation, but it also comes across as a gruff LLM that it is annoyed that it has to write the documentation at all.
I was reminded of https://github.com/localstack/local-surf but two things materialized out of trying it out against my local aws-emulator build: AWS Console uses a proxy endpoint just for their console, and is not implemented 100% in terms of "public" AWS api endpoints; and the other is that aws-emulator (as of v1.0.322 anyway) does not expose CORS headers which is fatal to trying to have the extension contact localhost
So, it's possible that some things would work after patching aws-emulator to cough up CORS headers, but I don't know what the state of affairs is for any reverse engineering of their console proxy endpoint. Likely it's available in localstack somewhere, given who made the extension, but I didn't go digging
After waiting for years for this kind of thing I ended up working around the issue by: using the real service. With Claude's help I have many projects now that test against live hosting providers using accounts maintained exclusively for testing. It ends up costing $50 or so a month in fees but well worthwhile for the assurance things really work.
I guess they didn't decide this was worth it till they needed it to train an LLM, huh? Not like everyone (inside and outside of AWS) has needed such a test harness for years...
Which is why they used AI to mock these APIs for you... too? I'd expect Amazon to feed it a lot of internal information so it has more to work with than anything someone else can cook up.
I think having an interface with your AWS implementation and one for test mocks has always been great advice. With this though, it helps enable better integration testing too. I consider this a testing compliment, but if I had to choose one these days, integration tests are cheaper and better hang for your buck than ever.
I'll continue to choose both though, depending on the thing being tested.
No idea why there's so much of this lately, but there are way too many editorialized submission titles hitting the front page recently. Please stop doing this.
We've banned this account - not particularly because of this post, but because you've been breaking the site guidelines repeatedly and aggressively in other places. Not allowed here.
Just a little bit more to keep you hooked. You should do your best to stay away from these parasites. Especially if they don't respect your country and your people by not paying the right amount of tax.
Skeptical of using because it's not clear whether this was just an exercise or a real product they are going to ship and maintain.
Floci[0] has been great for me. Use the Testcontainers[1], too.
Bonus: works for GCP and Azure, too (so far have only used in limited capacity, though).
[0] https://floci.io/
[1] https://testcontainers.com/modules/floci/
It’s a real product that we plan to maintain.
Is there anywhere I can find a matrix of what services are emulated and how complete that emulation is? I tried the docs but just ended up going round in circles.
Sort of. The releases page leads you to a massive blob of json with all the compatibility tests and scores.
Edit: The current one: https://github.com/aws/aws-emulator/releases/download/v1.0.3...
You can get some idea if the product name is unique enough with <ctrl-f> and looking at each of the related test scores.
Asked a clanker to correlate the test data (link in parent) with: https://raw.githubusercontent.com/aws/aws-emulator-evaluatio...
And output something meaningful for some of the more popular services:
Pass rates from the release's scores.json (commit 7753983), joined with the eval suite's manifest.jsonl. Tests = behavioral checks touching the service. All = overall pass rate. Happy/Reject = valid requests vs. requests AWS should refuse. Ctrl/Data = control plane vs. data plane. Solo/Integ = single-service vs. multi-service checks. Wire# / Wire% = count and pass rate of recorded request/response replay tests (a test passes only if every call matches).Edit: Also worth a look: https://ministack.org/blog/aws-emulator
If its up to this emulator to keep track of changes in Services APIs this is doomed to fail.
I believe AWS already autogenerates their API clients (e.g. boto3) based on some authoritative internal service api spec so I imagine that spec could be used upstream of this tool as well.
But their auto generated API clients don't have the invariant baked into them, which makes them very rough to use in say Rust.
They'll have something like this:
Except, this is not defined in schemas, this is merely defined in prose around the documentation.So your Rust API is full of Option, and it gets really annoying when you're testing things like say Bedrock, which takes 10 minutes, and then fails because what you submitted 10 minutes before doesn't match their schema.
I understand this can be fixed by reading the documentation in more detail, but it has gotten so verbose, and sometimes you just want to start something.
Not internal. Open sourced: https://github.com/aws/api-models-aws
Yeah whatever they did internally to get service teams to actually adopt AWS Config ~5 years ago needs to happen here or it’s going to get stuck with marquee services and that’s it. Especially given this is a much much larger ask of each service.
AWS Config already doesn’t support some pretty important things
Agreed but it used to be way way worse.
This wasn't clear to me, either.
Not to be rude, but your profile doesn't list who you are in relation to AWS.
I mock (ask Claude Code to make something run in a container) my own AWS services today for CI and development. I'm excited to learn more about how AWS uses it and hopefully use this for CI and development.
Any chance it will be able to spawn actual containers in the future?
Until the plan changes, which at some point, it will. Comment is still appreciated for what it is.
Edit: Comment is in the spirit of "it gets tiring to build on sand which is at the whims of corporate management folks far disconnected from the actual work." If someone is asserting "this will stick around," words are insufficient, words are free. Show me the contract, show me the penalties for failure to abide by the assertion.
This is an Amazon product, not a Google product.
Amazon team killed the Copilot CLI[0] which I thought was the single best thing they ever did for AWS infra. Made it tolerable to deploy on AWS; still salty about this one.
[0] https://aws.github.io/copilot-cli/
The two have different failure modes.
Google builds up a product over time and abandons it. This is annoying for long term adopters.
AWS has a habit of throwing a bunch of products at the wall, but only bothering to maintain & build up a few of them. This is annoying for early adopters.
Azure on the other hand. Will throw products out, ensure they are never consistent with other offerings on their platform, and then deprecate it from under you while promoting the same thing with a new name.
I think there was some truth in this in the early days of Azure (and all clouds) as the companies were looking to work out what cloud services were really needed. I don't see this as much any more though esp when a services makes it to GA they have published commitments for service availability and API compatibility. (I was in Azure for 10+ years so definitely let me know if you disagree)
Yeah I disagree. First of all, Azure is mostly garbage so avoid it if you can. Second of all, Azure deprecation follows Microsoft's general policy of deprecation which is The Fadeaway Policy. Don't publish anything publicly about it, gut the team to go work on something else, transfer the service to be one of 6 dozen other services some random offshore team is "maintaining", experience enough outages and trouble and during every support call they nudge you to move to something else, but the service is "totally not deprecated" because we haven't gotten a memo that says that, but we're only doing "security" fixes now. wink wink, nudge nudge.
Fine to disagree - but it would be better to share real insights rather than just blanket statements. Sounds like you have had some bad experiences - maybe you could share more?
Let me quickly compile a list of the last 700 failing bicep deployments with an “Internal Service Error” or No capacity errors along the all the no-op idempotent puts that take 30+ minutes for some reason, the broken networking system all up, the constant support advise to move to different regions, except half the things you use are not in that region, or the constant advice to just delete everything and start again or the half docs half marketing fluff docs. Azure only exists because large enterprise looks at a list of checkboxes before signing a contract. No reasonable person should ever use that garbage unless you’re offered deep discounts to do so, and even then, limit your usage to things you can migrate easily whenever the discount expires.
This is annoying for everyone.
And Azure will send you an email every day about how you need to migrate X to Y without any way for you to know where those instances are or how to find them.
You're certainly not wrong. But in the wake of Localstack's changes, the landscape has been full of slopware and low trust anyway. I don't think this is worse, for now at least.
Why would you say this? AWS are notorious for maintaining things.
"Things change over time" that is how the linear passage of time tends to work, yes.
I mean isn't that true for every single thing made by anyone? In that case what more do you want from them?
As someone who used QLDB as a WORM audited log for a financial system, and ran AWS classes that used Cloud9, they do depricate.
Not many, and not often but it is annoying.
A bit more polish for a public facing artifact from a multi-billion dollar org with armies of engineers and big token budgets.
The Copilot CLI https://aws.github.io/copilot-cli/ you can feel polish and pride of the team that built this, as an example.
Except for things they make: forever maintained forever.
Nothing personal, but unless you can link us to a public announcement made by Amazon, your statement is worth less than nothing.
Official statements made by a company are still poor representations of their current business plans, and don't mean anything 3 months later (no matter how much they pinky promise). But a HN post isn't even that.
I don’t take it personally; I realize you don’t know me, and a sentence on HN isn’t much of a guarantee.
That said, it’s been announced publicly here: https://www.aboutamazon.com/news/aws/how-autonomous-ai-agent...
Additionally Swami, our SVP of AI blogged about it separately and our CTO is tweeting about it - which is more than a number of products get in terms of coverage.
I didn't mean announcing the tool, I meant an announcement committing to the maintenance/support that users like the GP poster were looking for. My bad on describing that clearly, I'm gonna get clowned on in the comments and I'm not turning this around.
It has its official document page: https://docs.aws.amazon.com/emulator/latest/userguide/gettin... and it lives in https://github.com/aws/ org. I think AWS is pretty committed.
I understood what you meant. I was just trying to add evidence to support my claim that it was a real product and would be maintained. And yeah, votes on comments can be fickle.
I think one thing that concerns many people is that this looks like AI slop, which it clearly is according to the blog post.
I think this is a super interesting direction, but how can we trust the accuracy of this simulator? Agentic loops are great and all, but they can still miss plenty of things.
Or maybe a better question: where is the accuracy of this simulator going to be guaranteed enough that we should trust it?
To me, something like this is actually what vibe coding thrives the best at; tight, looped, easily verifiable, test-driven dev work. In fact, this is probably the field it can do with little or no intervention, if you're willing to waste tokens.
Is it? How is it verified that this catches all the potential edge cases of interacting with AWS? Or is handling all the edge cases of AWS not in scope?
Like, what am I actually getting here? Is it just happy path operations being correct here?
For real edge cases, it will be like any other software. Users get to be the guinea pigs and report bugs as they find them.
Hopefully AWS has had enough internal guinea pigs before they published this!
In the near future, every case will be a real edge case and every one will be a guinea pig.
The border between AWS and AWS emulator becomes fuzzy. And the users of AWS will be agents as well. A completely offline emulator will save a lot of resources and could be a great training ground for more focused (offline) models.
Back in the day, we assumed that when a major company open sourced code, that code would have problems. We invented all these things like ‘issues’ to deal with this.
https://www.aboutamazon.com/news/aws/how-autonomous-ai-agent... ?
GP statement still stands, actually being strengthened. This blog post doesn't even mention nor seems to care about maintainability or long-term support or anything that users will care about. Only talks about how cool the team is and how amazing they're at using AI, multi-agent workflows, and this kind of bs. It's funny how author talks so much about testing when they themselves also boast how they haven't written or reviewed any of the code.
Also doesn't mention any benchmarks or compatibility matrix.
This feels like table stakes for an emulator.
In my experience Floci has been the epitome of vibe coded - huge amount of changes, with things breaking randomly between releases. Moved away from it as soon as I could. Still better than Localstack :)
I didn't have a good experience with test containers, but perhaps it'd work better with fast starting containers. We run our test fixture with compose, and have the tests manage their data in isolation - so we don't pay the startup penalty in our test suites.
I think I'd trust this project at least as much as Floci. Embedded Rust mode also looks very interesting for us.
I only use Testcontainers with "explicit" tests (do not run by default in CI; must be run explicitly). This lets agents exercise the integration with a realistic fake locally, but does not incur the cost in CI nor for any dev unless they run it explicitly (usually also with a category so it's explicit + category filter)
It's on their official docs, so probably not just someone's side project: https://docs.aws.amazon.com/emulator/
AWS isn’t Google. They tend to maintain everything they put out and they don’t put out things randomly as a result.
Not really. I was trying to use their own Q AI to help me get something set up and it was constantly wrong about what screens to go to, what was on the screens etc... If their own AI doesn't understand AWS, I don't have confident this will either.
It has an official documentation on the AWS website, why would you assume it's not a real product? Because it was launched recently?
No docs site linked on the GH. 3 weeks old. Blog post talks more about the process than the tool and opens with:
Feels more like a science experiment than a product from that announcement.Doesn't feel like a real product. But I also didn't look very hard for docs; I kind of expect it to be linked on the GH in the site and have a nice `llms.txt` for me to give to my agents.
Disclosure: I work for Amazon. I'm not directly involved in building this product, but I'm familiar with the product and its development.
The product documentation is here: https://docs.aws.amazon.com/emulator/latest/userguide/what-i...
While the GitHub project is young, the internal effort to build this has been going for quite some time now.
Your comment comes off very dismissive and in poor taste.
> Doesn't feel like a real product. But I also didn't look very hard for docs
You should try, they're there.
> I kind of expect it to be linked on the GH in the site and have a nice `llms.txt` for me to give to my agents.
There's an official Amazon Documentation site that's linked. There's also an `AGENTS.md` file in the repository.
Sure they are, but they could have polished their product and showed some love by configuring the repo details and put the website there. Did you look at the blog post as well? Does it look like a product that some team there loved and will care for? Or the output of some exercise for some enterprise content?
This post https://www.aboutamazon.com/news/aws/how-autonomous-ai-agent... doesn't set the right tone for me at all and it has nothing to do with agents and everything to do with the lens of looking at this as a science experiment instead of a real enterprise tool.
> they could have polished their product and showed some love by configuring the repo details and put the website there
This feels like such a weird nit-pick when AWS is criticized for not moving quickly enough. Why should I care if there's a link in the side bar, when there's plenty of links in the `README`? If anything, I'm happy that there's alternatives to Localstack that are supported by AWS themselves that I can begin incorporating. They have a well written `README` that I can start working with and a User Guide to get me started. What else could I want?
> Did you look at the blog post as well?
I did.
> Does it look like a product that some team there loved and will care for? Or the output of some exercise for some enterprise content?
Do you even have the grounds to cast judgement like this when you admittedly didn't even look hard enough?
I looked, but you're mistaking my critique here: I value polish.
This lacks polish.
Small details like getting your GH repo set up for a public audience. Lacking. Compatibility and support matrix clearly advertised? None.
If this public facing artifact exhibits a lack of care and love, what does it say about the code? I am all for vibe coding and agent software factories, but then the humans should show some love with all of that extra time saved.
You might want to reconsider how you present the critique then, because that's not how your root comment came across or any of your subsequent messages, especially when engaging with (presumably) actual AWS employees in this thread replying to you.
Look at AWS Copilot CLI https://aws.github.io/copilot-cli/docs/concepts/environments... and the repo https://github.com/aws/copilot-cli/.
Look at Floci (I have no affiliation) https://floci.io/ the blog https://floci.io/chronicle/ and the labs https://floci.io/labs/
Do you agree that there's a polish here that shows a team's pride in that work that is clearly missing in this work?
??? You and I are the customers. What even is this statement? Are AWS employees our benefactors? Wow. I do not care if their feelings are hurt because this "product" clearly shows a lack of polish and love.> Do you agree that there's a polish here that shows a team's pride in that work that is clearly missing in this work?
No and I think the inverse is also possible and if anything more likely. You can make a website look really pretty, really easily and have the product still suck. This is "product as a slide" in a new age where making visual eye candy with AI has never been easier.
> I do not care if their feelings are hurt because this "product" clearly shows a lack of polish and love.
The point isn't about hurting feelings. The point is about providing critque and feedback based in reality, not based on "vibes." You're trying to gatekeep people releasing software because you dont like the way they're launching it lol.
Clearly according to whom? You?
If your complaint is about polish, you’re a very poor writer. It should not have taken this many replies to get that point out. But regardless of your communications skills, I disagree - this product looks fine for something released at this stage.
> No docs site linked on the GH.
??? It's in bold just before the "Quick start" section
There's a right way and a wrong way to assign a website URL in GH.
The team didn't even take the time to review these small details of the repo, you know, by editing the repository details to place the docs URL there.
I mean, I don't know about you, but I feel like I still like to see people care about the stuff they produce and missing something as basic as the repo website URL in GH settings shows a lack of polish and love.
From the security page [0]
> Don’t use the emulator to test the following:
> - IAM policies and permissions boundaries
> - Resource-based policies, such as bucket policies
> - AWS KMS key policies
> - Access across AWS accounts or across AWS Regions
> - Any other security control
> Some services in the emulator evaluate IAM policies for IAM users and roles that you create in the emulator, but not the same way as AWS. The emulator never denies a request signed with its own key. It doesn’t check AWS KMS key policies or Amazon S3 bucket policies. It also doesn’t support calls across accounts or Regions. So a request that AWS denies might succeed in the emulator. A request that AWS allows might fail.
This is a shame because I'd love for the official AWS product to be better than e.g. ministack and localstack on this, which will go some of the distance. I think because the agents were only building on the public API surface, it's hard to build this part. But they should've tried and let the agents read whatever policy engines AWS has. Or maybe it's a way to prevent someone from trivially running aws-emulator as AWSaaS?
[0] https://docs.aws.amazon.com/emulator/latest/userguide/securi...
Say whatever but without AI and agents, no one in AWS would have thought of building this given the huge amount of services they have. Humanly, possible but very very costly. Not saying has not happened before but fakecloud and localstack etc? That moat is gone.
I am shocked TBH that this is the new normal. Agents writing code in one of the most difficult to use languages. And ugly as well TBH, it pokes into your eyes. Subjective I know but it is a horrible language for humans.
> Agents writing code in one of the most difficult to use languages
Arguably, languages with strong static guarantees are exceptionally effective for LLMs since they're much quicker to provide feedback to the LLM than a dynamically typed language (which only fails once you actually run it - often several times to find the actual problem). You also get very well-designed build error messages rather than having to parse unstructured stderr output, etc etc.
Rust is beautiful! The way all the stdlib traits slot into each other satisfies a very particular itch
Like I said - subjective. Crates, modularity, tooling? Nothing comes close to Rust. Period.
yeah for all the faults with 'a.i' certain things have just become possible because of it.
We are talking about a company with ~3T market cap, right?
Exactly. Amazon is worth 3T because they're really good at cutting cost.
As a human, beep boop, I find Rust a beautiful language.
If I understand this correctly, it means I can point my entire CDK project to the emulator and test a `cdk deploy`?
I'm curious just how realistic the "internal" behaviour is emulated. It's been a while (since I got my stack working and I just don't like touching it now...), but I recall it being a real pain that sometimes odd, sometimes inconsistent things happened with setup and teardown (even through Terraform), which led to long timeouts if you did things in the wrong (but seemingly valid) order.
> I'm curious just how realistic the "internal" behaviour is emulated.
It seems like some reasonable shortcuts are taken, like services reading from each other's states directly instead of using APIs [0]. But then it will go so far as to run an in-process NodeJS emulator for lambda functions, and give it a shim so the code it runs can call other emulated AWS services using the main router [1].
[0] https://app.ilograph.com/demo.ilograph.AWS%2520Emulator/Serv... [1] https://app.ilograph.com/demo.ilograph.AWS%2520Emulator/Invo...
Fellow Amazonian here. Want to say that I’m grateful you built this and it has tremendous value if pulled off well and properly maintained.
Agentic development is all about closing off a system as much possible, then mocking up or simulating any inputs or dependencies that cannot be closed off. At that point, you let Claude crawl over the system and do its thing.
This inevitably runs into problems with infrastructure and any tools that help mock up those interfaces will be tremendously valuable. Thank you!
Personally, i've done away with all of these managed services and just run everything on NixOS.
Cloud provider neutral. Tear it up and tear it down with 100% reproducibility.
Related to this post: https://www.aboutamazon.com/news/aws/how-autonomous-ai-agent...
> We’ve had our agents build many versions of this emulator as we’ve refined the building machine.
I'm curious how many versions they made and the token spend on each one. There are a lot of failure modes to projects like these (e.g. gas town endlessly developing itself). Is this more of a sly marketing stunt or a real indication that this methodology is practical and economical?
FYI I checked out the repo. `du --apparent-size -h` output for some dirs:
311 MiB of rust code in /tests/ directories. 357 MiB of rust code outside of /tests/ directories. 117 MiB of json. 1 MiB of toml.What makes this any different than fakecloud?
https://github.com/faiscadev/fakecloud
I had a good time using its SDK inside my integration tests. I'll give a couple months before even moving to this because it's weird how similar both projects look like.
EDIT: After checking AWS's project I'd say stay away from it, looks heavily vibe slopped.
claude is the second-most frequent author in that fakecloud repo, what makes you say that's not vibeslopped either? This is 100% the perfect usecase of using a swarm of agents. It's a bounded, and easily-verifiable with property testing/mitm proxying, task. If you think in November 2026, agentic engineering is equivalent to vibe coding, you need to update your priors
at least in fakecloud's case, there's still humans being assisted by LLMs.
one can also argue that offering SKDs for python / typescript / golang makes the project superior still. So you are not stuck with Rust-only projects.
I remember asking this to one of the evangelists when AWS first came out, how do I run this locally. This was during the times where we actually tried to get all the .NET and C/C++ docs locally.
Now doing the math I feel old.
AFAICT there isn't a quick way to reset state other than restarting the process - in other words it probably isn't a drop in replacement for https://github.com/getmoto/moto for running tons of tests where the state of the mocked AWS system needs to be reset after each test. Hopefully they will implement a quick reset functionality; multiple accounts and full org APIs emulation would be nice too.
AWS already models all their services with Smithy, the specification language they created. Their API clients are all generated from Smithy, and the emulator seems to have been built using the Smithy specs and comprehensive integration testing against the real APIs. Using the spec ensures they hit every variant and optional field of every endpoint, unlike Floci and Ministack that only implement the more commonly used ones.
https://github.com/aws/api-models-aws
https://github.com/smithy-lang/smithy
Thanks to Fable, I’d imagine :)
I’ve been having it build local mock APIs for any service that exposes its OpenAPI spec. Works like a charm.
Thank the maker!! I was not having a good time with LocalStack, only an average time. Definitely have to try this out. I need the environment to survive a reboot.
> How AWS Emulator keeps improving
> AI agents keep the emulator up to date with AWS.
Is pretty interesting! No more detail than that tease though.
https://docs.aws.amazon.com/emulator/latest/userguide/what-i...
Excited to see this develop and be a free replacement to localstack / similar providers.
Except that https://github.com/faiscadev/fakecloud has been a thing for a long time and it's AGPLv3.
Localstack is almost entirely free. I’ve used it at our company for years without paying.
Localstack is no longer free and if you’re using it commercially you need to pay for a license. The free plan explicitly states that it is non commercial.
https://blog.localstack.cloud/2026-upcoming-pricing-changes/
The README.md states you need 100GB free disk space to build, and they do not provide binary releases. I hope that changes soon!
Do I need to get certified to use it?
Looks like this was ~100% generated with Claude within the past month. Interestingly it still has a lot of occurrences of words that Opus used way too much pre 5.5, so maybe they're not using the latest models.
https://github.com/search?q=repo%3Aaws%2Faws-emulator+load-b...
https://github.com/search?q=repo%3Aaws%2Faws-emulator+%2Fno+...
https://github.com/search?q=repo%3Aaws%2Faws-emulator+golden...
Seems like a great fit for LLM - extensive documentation, plus a live system it can probe against freely to match the behavior.
I mean, if they're using it internally then there's probably a TON of context you can feed these things to converge on approximately-correct solutions. Certainly it sounds like it can be a much better alternative to Localstack/Floci and friends.
29,000 commits in a month is crazy
Wonder if this could be considered a replacement for Ministack which itself was a vibe-code replacement of Localstack?
looks like ministack made an announcment
https://ministack.org/blog/aws-emulator
Oh fuck yeah. I was really annoyed by companies wanting you to pay just to use a simple offline emulator which doesn’t cost them anything.
Wouldn't be better using agents for simplifying the mess some services like iam or cognito are?
This is no doubt made possible by an agentic coding loop. If you have the right checks in place, it can be easy to emulate existing software.
I was able to create a TV emulator at my work with a mostly independent agentic loop, because we have a lot of tests to examine a smart TVs APIs. The agents mostly just need to make the tests pass.
The title for this story should be "aws-emulator, from AWS".
Why?
Because the rules say not to editorialize post titles
The post title is the name of the tool. It's not like a blog post where we can stick to the same copy, one-for-one.
Yes, even "from AWS" is editorializing, and as you can see, even that got cut.
I guess I'll go literal:
"expressing a personal opinion, bias, or subjective viewpoint in a context—such as a news report—that is supposed to be strictly factual and objective."
How does the title do any of the above that makes it editorializing?
The original title included “finally”, which adds a bunch of connotation from the submitter.
Does this have pricing data? So you can see how much deployed resources cost?
They wouldn't include it otherwise the binary would be comically large since (as one might guess) there are a lot of knobs involved in pricing AWS things. Just downloading it takes several minutes, served from S3
https://github.com/opencost/opencost/blob/v2.5.3/pkg/cloud/a... is the source URL, and while I haven't been in the opencost ecosystem for a while, I'd guess there's a non-zero chance you could legitimately just ask it to price your aws-emulator resources. I am pretty sure there is a terraform/opentofu integration, too, although I don't this second know if it is within opencost or is a separate project
For me, what is interesting in this project is it's git history.
Repo has 29,684 Commits!
Code frequency pages shows:
"There are too many commits to generate this graph."
https://github.com/aws/aws-emulator/graphs/code-frequency
First commit two weeks ago. Insane number of commits, even for AI agents. They must be using large fleet of agents.
Will it be maintained? Or was it more of a toy-project for its large scale agentic blogpost? [0]
[0] https://www.aboutamazon.com/news/aws/how-autonomous-ai-agent...
it's going to be maintained, official product
~30K commits in 3w; quality software for sure. Is someone trying to get promotion by tokenmaxxing? Ironic or unlucky coincidence or competitor(s) misdirection, that, only 2w ago, Amazon published memo discouraging AI abuse?
It's funny to read AI-generated documentation that is the result of a prompt instructing the LLM to be as terse and straightforward as reasonably possible. The agent was probably told to conform to ASD-STE100.
It's better than a lot of AI-generated documentation, but it also comes across as a gruff LLM that it is annoyed that it has to write the documentation at all.
RIP LocalStack… can’t say I’d be unhappy to see it go though.
> AWS Emulator is configured to collect and report usage data to AWS, to gain insight into how AWS Emulator is used. Telemetry is on by default.
They can't help themselves, can they?
I'll stick with Floci and Testcontainers.
29000 commits and no contributors
Seems like the bunch of AI induced failures they had "paid off" in getting this done
Mh, no transfer family service... I wonder what else is missing..
If this does not kill you ec2 instances randomly its not emulating shit lol
Official post https://www.aboutamazon.com/news/aws/how-autonomous-ai-agent... (https://news.ycombinator.com/item?id=50456319)
Can it emulate billing too, i.e. "rand().powf(rand()) % downtime"?
ok who's gonna build the GUI / web console on top of it?
I was reminded of https://github.com/localstack/local-surf but two things materialized out of trying it out against my local aws-emulator build: AWS Console uses a proxy endpoint just for their console, and is not implemented 100% in terms of "public" AWS api endpoints; and the other is that aws-emulator (as of v1.0.322 anyway) does not expose CORS headers which is fatal to trying to have the extension contact localhost
So, it's possible that some things would work after patching aws-emulator to cough up CORS headers, but I don't know what the state of affairs is for any reverse engineering of their console proxy endpoint. Likely it's available in localstack somewhere, given who made the extension, but I didn't go digging
For what? Use the APIs.
I could see this being useful. Just let Console pick the localhost:xxxx endpoints for everything, boom, my "own" fake AWS.
annoying that it took AI happening for AWS to finally deliver on this though I'm glad they did
ironically localstack is solid enough to probably not need this for most things
After waiting for years for this kind of thing I ended up working around the issue by: using the real service. With Claude's help I have many projects now that test against live hosting providers using accounts maintained exclusively for testing. It ends up costing $50 or so a month in fees but well worthwhile for the assurance things really work.
I guess they didn't decide this was worth it till they needed it to train an LLM, huh? Not like everyone (inside and outside of AWS) has needed such a test harness for years...
A mere 20 years too late. Now it’s faster to have AI mock your APIs for you. AI has been a boon for test coverage.
Which is why they used AI to mock these APIs for you... too? I'd expect Amazon to feed it a lot of internal information so it has more to work with than anything someone else can cook up.
https://www.aboutamazon.com/news/aws/how-autonomous-ai-agent...
it takes more time for my AI to learn their "emulator" . And I end up with far fewer dependencies on my own.
I've been prompting the agents to build everything using stdlib
I think having an interface with your AWS implementation and one for test mocks has always been great advice. With this though, it helps enable better integration testing too. I consider this a testing compliment, but if I had to choose one these days, integration tests are cheaper and better hang for your buck than ever.
I'll continue to choose both though, depending on the thing being tested.
Finally!
No idea why there's so much of this lately, but there are way too many editorialized submission titles hitting the front page recently. Please stop doing this.
<https://news.ycombinator.com/newsguidelines.html>
Almost every large thread has upvoted comments that violate the comment guidelines, now, too. In both cases, not enough people flagging them, I guess.
[flagged]
We've banned this account - not particularly because of this post, but because you've been breaking the site guidelines repeatedly and aggressively in other places. Not allowed here.
https://news.ycombinator.com/newsguidelines.html
Just a little bit more to keep you hooked. You should do your best to stay away from these parasites. Especially if they don't respect your country and your people by not paying the right amount of tax.