The Agent SDK

52 pointsposted 4 hours ago
by torutofu
(cursor.com)

60 Comments

h0rv

4 hours ago

Why would you not use an open-source harness in October 2026? I am generally curious - what is the alpha?

chrisvalleybay

4 hours ago

Well, I'd love to use an open-source harness! My issue is that Opus 5.5 / Fable 5.1 has been the best model for me to work with, and it's way cheaper to use it with the subscription to Claude Code Max. I won't pay more just to use an open-source harness. I'd rather just wait it out and stay on Claude Code not having to constantly jump around / switch tools as the industry matures.

julesrms

4 hours ago

You can use your claude subscription just fine in open harnesses!

I make one (https://github.com/juggler-ai/juggler) and it'll auto-detect and use your claude CLI. I use that claude plan for 90% of my work, plus a bit of GPT, I just prefer to do it inside a nicer, less locked-in environment than claude.

There's really no moat around proprietary closed harnesses, it's trivial to jump between them, but people need to be aware that it's possible!

aenis

3 hours ago

Locked in? I routinely switch between claude and codex, same codebases, same skills, and even shared "memories" with maybe 5 minute effort to set it up. There is no lock in whatsoever.

behnamoh

3 hours ago

it goes against anthropic‘s terms of service, and people have had their Claude accounts banned for doing exactly this.

julesrms

3 hours ago

The big hoo-har about it earlier this year was because something (opencode?) was pretending to be the claude CLI and using the API that way. Anthropic made a fuss, then GPT said "we don't mind people using their own harnesses" and everyone relaxed about it, as long as the harness goes via the claude CLI and doesn't try to cheat.

Qworg

4 hours ago

You don't have to pay more - I wouldn't switch to an open source harness on a whim, but your harness/cheaper agents can always call Claude Code headlessly.

chrisvalleybay

3 hours ago

As context: I work as a consultant and produce code on behalf of my customers. What's most important to me is that the quality of the code is as high as it can be, without me having to rerun it with multiple different models to see which agents produces the best. If Opus 5.5/Fable 5.1 (or a different model for that sake) consistently produces the best code, I will use that for all my tasks, since that lowers the cognitive burden.

The cheaper agents never really matter, because the Max subscription costs me $100 and that is less than an hour of pay. In some cases the customer even pays for the subscription.

But I do love the idea of being able to use Pi or OpenCode. I am a heavy terminal user, and used Vim/Tmux/Lazygit-types of workflows before coding agents were in the terminal, so I do love customizability and portability. Right now there is just too much ground-shift to take part in it. Better to wait it out.

javier123454321

an hour ago

But but you can get incremental benefit, possibly even higher than the switching cost!

Benjammer

an hour ago

Why would you not just build your own harness in October 2026? Gateway, memory, tool calls, LLM api - the basics are pretty simple to get started and get to a point where your harness can be self-improving to add any new features that you need.

giancarlostoro

3 hours ago

Claude Code wont let me use their sub with one as far as I remember. So I'm stuck with their convoluted TUI. It does what I need, and when it doesn't I just build tools that Claude consumes. The new "Artifacts" feature has helped a bit though.

NezArk

an hour ago

You can. Anthropic documents it: the Agent SDK and claude -p work signed in with your Claude plan and draw from your normal subscription limits. https://support.claude.com/en/articles/15036540-use-the-clau...

We build a desktop app on top of the SDK, so I've spent a lot of time on that page.

hedgehog

37 minutes ago

Not true any more, read the note at the top of that page. They give you API credits but it's limited.

lxembourg

31 minutes ago

…have you read that note? Specifically the last half?

yako21000

3 hours ago

It's the one features that keeps me using claude, it's simply convenient.

giancarlostoro

3 hours ago

I was both excited and disappointed to learn that Claude Code has plugins, but they're not like actual plugins to let you customize CC, which would be nice.

sodacanner

3 hours ago

There's just not really any features in an open-source harness that blow my mind enough to move off the highly-subsidized claude code subscription. I type in instructions and it spits out code. I'm increasingly of the opinion that the more complex features being floated are productivity theater.

verdverm

31 minutes ago

A main criteria in 2026 should be whether the harness gives you access to all model families for just the harness author's models.

More and more harnesses are headed this way, there are two notable holdouts.

ramoz

4 hours ago

If you tell me I should OpenCode over Claude Code in October 2026 - then you have no idea what you are talking about.

mkw5053

3 hours ago

OpenCode + DeepSeek V4.1 Flash Uncensored on Venice AI is truly incredible. Granted, I have it also drive an interactive claude code session in tmux and just do everything Claude Code refuses to. But, it just gets shit done. Kind of what makes Instinct so powerful, don't tell me you won't do something, just get it done.

ramoz

3 hours ago

Interesting on Instinct, I have to often tell it "just do it"

jatins

4 hours ago

say more, what do you think CC does better?

lifeisloving

3 hours ago

Im not sure how they would know, they're clearly using a singular harness.

ramoz

3 hours ago

I actively use all harnesses and maintain popular plugins across them

joshheitzman

12 minutes ago

> I actively use all harnesses

Several perhaps, but you definitely aren't using all coding harnesses actively.

fallks

an hour ago

What about an AgentFactoryFactory? That would increase Cursor's valuation from $60 to $120 billion.

username_my1

4 hours ago

I'm starting to think that the LLMs ecosystem is going in the JS ecosystem direction, endless technologies with little to no adaption.

Literally everyday there is a new tool and the tools released last week are deprecated.

fg137

4 hours ago

I see people spending so much time creating "workflow" skills that have no benchmark whatsoever to prove they are any more effective than plain one sentence prompts.

tikotus

4 hours ago

This takes me back to the era of object oriented programming and UML diagrams. More time was spent framing the solution than implementing it. Is there maybe one more design pattern that could be applied? And when the time to implement came, all those diagrams were mostly in the way. But doing it was fun, since it allowed you to focus on the fun, big picture and skip the nitty gritty details that were actually hard to solve.

I feel like people are going down that slippery slope with harnesses and skills and what not. With the right prompt, and with the right model, and with a sprinkle of magic, the solution will emerge. Oh, it didn't? Let's see if there's a new model available, or if someone has come up with a new clever skill or something. Maybe then... Because actually solving annoying problems is not fun, even less so now that the code is a black box only the LLM can understand.

dutchbart

an hour ago

Diagrams and really, just designing the software you are trying to build is mostly about finding out painpoints before you start the programming (at least at point the time-consuming part). The diagramming allowed you to, without programming, show interactions between modules and check on a high level if you are missing edgecases that can’t be solved because of the design. If you were just using it just to apply design patterns then you were doing it for the wrong purposes.

lifeisloving

4 hours ago

It reminds me of people customizing their nvim configs all day, thinking they're being productive but not getting all that much done.

andy55a

an hour ago

I spent a solid week on mine and haven’t had to tweak it in three years. We’re not all inefficient ;)

banorton

3 hours ago

Hey I never deluded myself into thinking I was being productive :)

simianwords

4 hours ago

This is so frustrating to me. Ever heard of the planner agent reviewer agent and the tester agent framework?

I'm not sure if that's what you mean but I know many that are making their own flow like this and think that this brings in a higher level of performance..

andyfilms1

3 hours ago

I would imagine that performance is coming from essentially dedicating 3x context windows to one task, rather than any particular inter-agent magic.

jst1fthsdys

an hour ago

I mean... isn't that the point of having multiple agents? You can more easily manipulate context to get more consistent results.

QuantumNomad_

4 hours ago

Gotta justify that $160k/yr salary somehow I guess, and if the AI is writing all the code you used to write and your job is now to manage the AI, what better way to spend the days than making new AI tools and workflows and markdown files all day

gonzalohm

4 hours ago

That's the whole point with AI. It's consumerism applied to software... And it sucks

maxdo

3 hours ago

why do we even care, this is a clear, lets move away from `people pushing software to git` to `agent is pushing software, agentic or not , to somehwere, db, git, or something else` human does involved in this unless there is a problem. JS or Python, is really not essential in this case, maybe it's WASM built from rust. it's not for human.

Cursor moving this direction, is a prep work where human no longer command that much , hence the usage will drop. e.g. their core product is vulnerable. Software factories, is the ultimate game over for our industry.

dangoodmanUT

3 hours ago

I attribute this to "it's so new and we don't know what the right answer is yet", but you may very well be right

wslh

3 hours ago

> endless technologies with little to no adaption.

I think the difference is that those endless technologies will probably be used by other agents without people's explicit knowledge.

virgil_disgr4ce

4 hours ago

I don't think I'll ever understand this argument. Especially from purported "hackers."

Why is a large number of ideas, technologies, frameworks, etc. bad?

panzagl

3 hours ago

Hackers hate frameworks because they hide the underlying truth of a system.

esafak

3 hours ago

'coz it's pointless if you can get the same results without them.

lifeisloving

4 hours ago

Its not bad, just most of them are created by corpos to sell slop to the masses. AI companies suck and you know it. Its not about good software, its about making as much money as possible before the hype train dies.

thedangler

4 hours ago

If you are on onstagram 99% of posts are people shilling skills where you need to subscribe to some service. To which they are an affiliate.

And a lot of the apps are the same thing.

It's going to be a race to the bottom.

pscanf

4 hours ago

I have so many use cases for this. I just hope that we'll get a standard like https://www.openresponses.org/, because the idea of coupling an app to a particular vendor doesn't seem appealing at all, especially since it seems that the functionalities they offer are more or less the same. (I'm thinking about the OpenAI's Agent API and Anthropic's Agent SDK as "alternatives.)

scosman

4 hours ago

Open AI and Anthropic already have "Agent SDK" brands. Vercel is "AI SDK". I wish folks would come up with some good names for new projects.

Raed667

4 hours ago

And Google has ADK (Agent Development Kit)

verdverm

27 minutes ago

This is my goto SDK, it comes in multiple languages too. I'm going to be wrapping the Go ADK in CUE Nov/Dec, along with Dagger, and rebuild my personal harness from scratch which I worked on last Nov/Dec.

ADK has a graph/workflow concept too: https://adk.dev/graphs/

NorthSouthNorth

38 minutes ago

Not to be confused with ACP (Agent Client Protocol).

_andrei_

25 minutes ago

...why? params: [ { id: "effort", value: "high" }, { id: "fast", value: "true" }, ],

holistio

4 hours ago

The video is still showing @grok/agent-sdk.

Meanwhile, we know Grok Bot was really Cursor beforehand... it must be wild in there.

mikert89

4 hours ago

Why would anyone use this over the Anthropic sdk

athorax

3 hours ago

You mean except for all the obvious reasons?

simianwords

4 hours ago

Honest question, why shouldn't any agent SDK's API simply be a PROMPT.md with a runtime that runs the LLM with tools; why do you need excessive abstractions over that like langchain offers?

Is it to have boundaries of some determinism?

zomtorg

3 hours ago

My 2c is that agents are not at the level where companies can easily just have unconstrained LLM with tools and let it be. Different parts of the workflow can have different models, different tools, different constraints, guardrails, etc.

The entrypoint still has to come from somewhere, and it's much more convenient to be able to explain the security and legal teams how data is handled, what is logged, how you can have control over a scenario where the agent does something unexpected.

Sure, for a personal project that could be enough, but we all know those companies target enterprise customers, and you would be surprised how little adoption there is when it comes to workflow automation due to the lack of controls.

ashishmax31

4 hours ago

>runtime that runs the LLM with tools

This "runtime" is what you are building with LangChain.. A harness like claude code/codex etc is general purpose and its env is a shell + tools. But with a custom runtime (basically a loop where we ask llm what to do next), we can give it specific tools which we define in code. This can help with things like authorization since, well its custom code you own.. so the runtime gets the tools scoped to the users permissions etc.