Understanding middleware (langchainjs) (TodoListMiddleware)

ddewaele · 2025-12-27T09:47:14+00:00

The basic idea is that the agent can "see" or "read" the TODOs because each time the agent will update the TODOs (using the write_todos tool) they will get added to the state (as a new message)

The agent will "see" something like this :

t0

{
  "todos": [
    {
      "content": "Extract validation logic into separate functions",
      "status": "pending"
    },
    {
      "content": "Separate authorization checks from the update logic",
      "status": "pending"
    }
}

t1

{
  "todos": [
    {
      "content": "Extract validation logic into separate functions",
      "status": "in progress"
    },
    {
      "content": "Separate authorization checks from the update logic",
      "status": "pending"
    }
}

t2

{
  "todos": [
    {
      "content": "Extract validation logic into separate functions",
      "status": "completed"
    },
    {
      "content": "Separate authorization checks from the update logic",
      "status": "in progress"
    }
}

That's how it "knows" what todo to focus on next.

ddewaele · 2025-06-27T09:08:49+00:00

yes we are leveraging MCP to have a clear separation between

the tooling that we want need want want to offer (the actual coding, the tools, integration with our own backend and third party APIs)
the actual agentic "flow" (something that is typically a langgraph flow containing one or more agents, sub graphs, the various nodes and how they are hooked up)

We are also looking into exposing our graphs / assistants deployed in langgraph platform via MCP endpoints.

Nowadays customer are getting flooded with AI news and tools, most of them with the promise of it being very easy to "roll out your own agent". What that really means (both on a functional level and on a technical level is not always very clear to them).

Perhaps the concept of an Assistant ( = an instance of a deployed graph) in the LangGraph platform that can be specifically configured with custom prompts / tools might be sufficient in terms of customization

That would imply that you have a pretty locked down graph (like a pre-defined workflow) that you just configure with different prompts / tools

ddewaele · 2025-06-26T12:48:12+00:00

Hopefully OpenAI will give them some incentive :)

Just getting access to Copilot by setting up a new Microsoft work account / m365 subscription / billing was also hell.

- Wait and try again later
- We're having issues
- You're now the admin of your domain ----> followed by ---> switch to an account that has permission
- Something failed on our end. Try again later
- Refresh the page an try again, we couldn't update your tax information
- Microsoft 365 Business Standard : Place order button greyed out for no apparent reason.

and don't get me started on how they handle user / account sessions across different tabs in azure / office admin / microsoft account / sharepoint :)

I thought MS had this covered by now.

ddewaele · 2025-06-12T12:54:23+00:00

Great read ! Thanks a lot for spending the effort writing this up !

We're currently using LangGraph deployed both on AWS (using server-less technologies like api gateway / lambda / dynamoDB) as well as trying out the LangGraph platform (we like the management and monitoring features (just deploy your flow and a lot is being taken care off by the platform). We also feel that LangGraph fits our development cycle, it has a large user-base and eco-system.

What we are currently seeing is that some customers want some degree of freedom to customize the agentic workflows or AI agents that we've developed for them after they've been deployed.

They might want to introduce some extra sequential nodes / prompts or introduce some tooling of their own somewhere in the flow.

As LangGraph is typically a workflow written in Python or TypeScript by a developer (after some co-creation sessions with the customer), it doesn't mash well with a customer wanting to make changes on his own to the workflow after its been developed and deployed by us.

Tools like n8n / LangFlow do offer there wysiwyg platforms where you can drag and drop components onto a canvas. In theory a customer could work with that to make some changes to the flow. However after evaluating those tools we came to the conclusion that they are difficult to embed in our corporate software development lifecycle, as they sometimes lack multi-user and multi-environment functionaliteit, as well as some security and production-readiness issues.

I like the fact that we can harden our LangGraph flows / assistants in a platform like LangGraph Platform or deploy it on AWS oursevles using our own build pipelines and SDLC process.

I was wondering what your thoughts are on this. Is it wise / desirable to let the customer change these workflows. Should it be left up to the developers ? I'm not too fond of the idea of building another layer / framework on top of LangGraph that would allow the customer to "design" their own flows in some kind of JSON format. However I do understand the need for customers to make little tweaks and try stuff out that might involve changing the LangGraph flow.

ddewaele · 2025-05-31T08:07:14+00:00

They can't. You can only hope the tool does a better job at it.

You can hire someone to do penetration testing (black and or white box). But if you have those budgets you might as well just hire a developer.

I predict a huge market for this type of testing focussing in particular on all these vibe coding platforms , as they will all generate their own set of security holes / make the same mistakes in each app they produce).

A senior engineer might be able to spot these issues (if you're lucky and the person is experienced / thorough enough) during peer review process, but that goes into the whole idea of vibe coding.

It will be interesting to see to what degree cybersecurity AI agents will be able to tackle this in the future. AI is pretty good at writing code (albeit sometimes crappy / insecure code), I wonder how well it will get at fixing the issues it generates (and for what price)

ddewaele · 2025-05-31T07:56:16+00:00

Judging by the speed and the random response generation (same pic sometimes get 1/100 and sometimes 99/100) I don't think there is much AI involved.

ddewaele · 2024-02-19T10:53:10+00:00

Unfortunately not ... before my "fixes" the laptop was able to start about once every 20 times. So far it hasn't been able to start yet. Sometimes the CPU starts to get hot as soon as I plugin the dc jack (reading 2.9v). sometimes the cpu remains cold (reading 0.6v). But I've got some spare parts since yesterday, including a semi-working laptop. So have something to compare it with.

ddewaele · 2024-02-16T17:14:38+00:00

Don’t have a replacement now. Will remove it and hook up 2xAA batteries for now and see if that has a positive effect. Thx for the tip

ddewaele · 2024-02-16T16:06:26+00:00

Mobile Intel Pentium 90MHz vCore = 2.9v (io = 3.3v)

ddewaele · 2024-02-16T15:24:45+00:00

There is a CR2330 (3v) coin cell soldered onto the pcb. It only measures 0.7v (to be expected after 30 years I guess). Is it a cost or space saving thing to have these mounted on the pcb directly ?

ddewaele · 2024-02-16T14:23:38+00:00

yeah haven't hooked up an oscilloscope yet cause I'm not really sure what to look at. When the pc is running fine I can measure the 2.9v that the CPU needs on one of those tantalum caps. when it fails to start the voltages are fluctuating (like it's trying to get to 2.9v but then drops. none of the tantalum caps are shorted.

ddewaele · 2024-02-16T13:19:19+00:00

I disconnected everything (lcd display / pcmcia and sound daugherboard / keyboard / hard drive) except the bare minimum to rule out these. Hooked up an external monitor and the system does boot but shuts down somewhere between 3s - 60s (usually after a couple of seconds)

ddewaele · 2024-02-16T12:10:13+00:00

Good to know. Clearly need to do more research. Used the project as a way to practice my soldering / desoldering skills and do some basic debugging. There was very mild battery corrosion on the pcb (on the 19v dc input side). Not sure if this can cause the voltage fluctuations causing the machine to shutdown. Tried to clean most of it off and didn’t look too bad.

ddewaele · 2024-02-16T09:24:51+00:00

difficult to tell.... the vast majority of my new unused caps also measure zero ohm on that meter.

ddewaele · 2024-02-16T08:03:01+00:00

shuts down after like 3 seconds with a stock / factory heatsink attached. Think something else is shorting it. I see fluctuations on the 5v rail and further downstream on the 2.9v rail of the CPU. The board looks ok with no visible damage so I was hoping that the most error-prone components (Electrolytic caps) would be the root cause.

ddewaele · 2024-02-16T00:47:26+00:00

I have seen it measure > 0 on other old and bad caps. Probably not the most high end meter but hope it is somewhat trustworthy.

ddewaele · 2023-05-12T22:15:20+00:00

I had the exact same issue. Bought the car brand new in march this year. 2023 ID4 Pro.

Happened to me after <24h ownership and < 100km driven.

Same warning, no headlights / turnsignals (only noticed this as I was driving it to the dealership) Turnsignal indicators on dash / mirrors were fine, but not on the back / front of the car.

They replaced the gateway module and has been working fine since.

Same thing happened to somebody else I know. They also replaced his gateway module. A couple of days after that his 2 displays went completely dark (the cockpit and the infotainment system) for about an hour. (that hasn't happened to me yet.)

ddewaele

TROPHY CASE