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shad42

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Automating the engineering work that isn't your product

mendral.com
2 points·by shad42·지난달·0 comments

How we know if our agent is right

mendral.com
3 points·by shad42·지난달·0 comments

Not update your dependencies in 2026

mendral.com
1 points·by shad42·2개월 전·0 comments

Supply chain attacks don't wait for CVEs

mendral.com
3 points·by shad42·2개월 전·0 comments

We built an agent for CI despite using Claude Code for everything else

mendral.com
2 points·by shad42·2개월 전·0 comments

We built an agent specialized for CI (using the 3 Claude models)

mendral.com
2 points·by shad42·2개월 전·0 comments

How we know if our agent is right

mendral.com
2 points·by shad42·2개월 전·0 comments

How we know if our agent is right

mendral.com
5 points·by shad42·2개월 전·0 comments

The agent harness belongs outside the sandbox

mendral.com
182 points·by shad42·2개월 전·121 comments

We decreased our LLM costs with Opus

mendral.com
106 points·by shad42·3개월 전·31 comments

Multi-player agents don't fit in the sandbox

mendral.com
2 points·by shad42·3개월 전·0 comments

We built our AI agent, for analyzing CI logs

mendral.com
1 points·by shad42·3개월 전·0 comments

Same LLM, different agent: a CI debugger built on Claude

mendral.com
2 points·by shad42·3개월 전·0 comments

Agent Harness: Inside vs. Outside the Sandbox

mendral.com
3 points·by shad42·3개월 전·0 comments

Same LLM but different output: we built a CI specialist

mendral.com
1 points·by shad42·3개월 전·0 comments

We upgraded our agent to Opus and our costs went down

mendral.com
2 points·by shad42·3개월 전·0 comments

Same LLM, Different Agent: What Changes When You Specialize for CI

mendral.com
3 points·by shad42·4개월 전·0 comments

We decreased our LLM costs by switching to Opus

mendral.com
2 points·by shad42·4개월 전·0 comments

What CI looks like at a 100-person team (PostHog)

mendral.com
56 points·by shad42·4개월 전·30 comments

We upgraded to a frontier model and our costs went down

mendral.com
1 points·by shad42·4개월 전·0 comments

comments

shad42
·2개월 전·discuss
Dependabot is focused on upgrading dependencies, and nothing else. One of your dep is outdated, here is an update.

Mendral is smarter when updating deps, it looks at newer version, scans for vulnerabilities or upgrade patterns that can put you at risk (eg. the update was published few hours ago, you should update it now).
shad42
·2개월 전·discuss
In this post, we built the harness, it’s not 3rd party (like Claude code in a sandbox). So we trust it as much as the rest of our backend code.
shad42
·2개월 전·discuss
No, for example a tool call calling an API. So the llm does not have access to the API keys, the tool does. For example an API call that fetches some data remotely and return it to the llm. You don’t need a sandbox for it. It’s faster and more efficient to keep this out of the sandbox.
shad42
·2개월 전·discuss
We don't host 3rd party agents (I don't know if this what you implied). We built an agent that monitors CI pipelines, tests failures, performance and auto opens PR to address issues we find. We host our agent loop on a backend (it's in go), and we call to the sandbox when we run operations involving the user code.
shad42
·2개월 전·discuss
Yes, it's also because the agent described in the post is doing some operations on the user code (fix CI pipelines, rerun tests, fix them, etc...). So another big reason to use the sandbox is to run things like bash on a user code. you don't want credentials or anything trusted inside that sandbox, including the LLM api key.
shad42
·2개월 전·discuss
[dead]
shad42
·3개월 전·discuss
We considered wrapping Claude Code when we started building Mendral (this agent in the article). We ended up building our own agent, it's lot more work because we followed all the right patterns as the models evolved (sub-agents, proper token caching, redo basic tools like read,write,edit,bash, etc...). But it paid off over time when you build an agent that is focused on a specific task (not a general coding agent).

The main driver for writing our own agent was to leave it out of the sandbox (the agent loop runs on our backend, we call the sandbox only when needed). We wrote another post about that (it's the latest post on the blog).

However, I am curious how would you implement the triager pattern by only using Claude Code as harness.
shad42
·3개월 전·discuss
Nice, it's on our todo list to use oss models too. What are you building?
shad42
·3개월 전·discuss
Curious, what steps did you follow to end up with this design (what did you try before)? And what's your use case for this agent?
shad42
·3개월 전·discuss
IMO RAG is mostly dead. The game changer with newer models like Opus is the reasoning. So instead of pushing all the context up front (RAG style), it's better to give strong primitives (eg. bash, SQL) and let the agent figure it out.

It's what Claude Code is doing now and the principles we applied for Mendral as well.

That said, you're right that some smaller models can outperform Haiku and we're thinking supporting oss models at some point. But it does not change the core design principles IMO.
shad42
·3개월 전·discuss
We're dealing with CI logs, produced by a variety of frameworks, languages, etc... And the tough ones to look into are e2e tests, with outputs from infrastructure. I wish a re.match() would be enough, but we often don't even know what to match in the first place.

We started to add deterministic matching on the patterns that the agent sees the most so we don't have to go through the whole thing (for example a flake on PostHog can occurs 100+ times during a day, you don't need to reinvestigate every time). But for new errors, it's tricky.
shad42
·3개월 전·discuss
It's the same as an escalation. Something we omitted from the post is that we often use Sonnet to write SQL queries.

We wrote another post that was on HN some time ago that goes into the details of SQL queries (linked at the top of this article). Sonnet is perfect for this.
shad42
·3개월 전·discuss
I am one of Mendral co-founder (my co-founder wrote the article), I am the one to blame for changing the title when posting. I thought our original one was too clickbait and I wanted to better summarize with this title.

Despite the original title, a lot of what we learned comes to how Opus evolved and the ability to reason. And also the fact that Haiku is quite capable if scoped properly, that's the whole purpose of the article.
shad42
·4개월 전·discuss
Mendral co-founder here. What happens at PostHog is not uncommon. While building Mendral, we talked to hundreds of team and they all have a similar situation. Initially they come to us to make their CI pipelines faster. But as the agent dives in, the urgency becomes keeping all pipelines reliable. It comes from growing a code base with a test suite. Of course it has to change eventually: splitting the test suite, running specific part of the CI depending on the code, etc... But the situation described in the article is widespread with a product that grows quickly.
shad42
·5개월 전·discuss
In some ways: we use their product and they use Mendral
shad42
·5개월 전·discuss
100% and LLMs have tons of related training data
shad42
·5개월 전·discuss
very interesting, curious if there is any downside to running this at scale (compute?)
shad42
·5개월 전·discuss
We did not want to make the post engineering-focused, but we have 18 companies in production today (we wrote about PostHog in the blog). At some point we should post some case studies. The metric we track for usefulness is our monthly revenue :)
shad42
·5개월 전·discuss
Mendral is replacing a human Platform Engineer. It debugs the CI logs, look at the commit associated, look at the implementation of the tests, etc... It then proposes fixes and takes care of opening a PR.

We wrote about how this works for PostHog: https://www.mendral.com/blog/ci-at-scale
shad42
·5개월 전·discuss
There is a cost associated with each investigation (that the Mendral agent is doing). And we spend time tuning the orchestration between agents. Yes expensive but we're making money on top of what it costs us. So far we were able to take the cost down while increasing the relevance of each root cause analysis.

We're writing another post about that specifically, we'll publish it sometimes next week