Simon Willison's Weblog: muse

Quoting John Gruber

2026-09-25T17:22:01+00:00

Muse is getting a lot of attention — including mine — because it’s both groundbreaking technically (each user gets their own entire persistent Linux VM running in Meta’s cloud) and because it’s packaged in an easy-to-install easy-to-use way. It’s literally presented as a cute mascot. It’s the first consumer-accessible agentic AI system, and Meta has truly done an amazing job with that. But it’s a genuinely open question whether consumers have any understanding what this means. If you buy a power saw that can cut your fingers off, you are almost certainly aware that you are buying a power saw that can sever your fingers. [...] I don’t think people realize how powerful — and thus dangerous — Muse is, especially if it’s running on your Mac.

— John Gruber, Muse Looks Cute, but Looks are Deceiving

Tags: john-gruber, ai, generative-ai, llms, meta, general-agents, muse-agent, muse

Introducing Muse Glimmer

2026-08-10T23:56:03+00:00

Introducing Muse Glimmer

Meta are back in the open weights game! Muse Glimmer is a brand new 30B model under a clean Apache 2.0 license (a step up from the janky Llama licenses of old).

They claim to have optimized it for exactly the kind of things I'm looking for in a local model:

End-to-end Agentic Task Completion. Muse Glimmer achieves strong success rates on full-task benchmarks including DeepSearch QA, MCP-Atlas, 𝛕-Bench and SWE-Bench, which measure its ability to work within scaffolds, write and debug code, and resolve multi-turn requests from start to finish.

Reliable Tool Use. The model handles a wide range of function calls, invoking tools with precise schemas throughout extended workflows.

Multi-Step Reasoning. Muse Glimmer chains reasoning over long horizons, sustaining coherent plans across complex, extended workflows. [...]

Here's a pelican which I generated using LM Studio's 18.16 GB version of the model:

I also tried it out with my llm-coding-agent plugin, running against a fresh checkout of Datasette with the prompt:

how does auth work?

Here's the response, at the end of a long transcript showing all of the tool calls it made to explore the codebase. I ran this using llm-lmstudio with this patch applied to upgrade it for compatibility with LLM 0.32.

I really like this size of model, because if a machine has 32 GB of RAM or more (mine has 128GB) it leaves plenty of space for running other applications at the same time.

Glimmer is a vision model, so I asked it to describe this image:

llm -m lmstudio/meta/muse-glimmer -a https://static.inaturalist.org/photos/714731804/large.jpg 'describe image'

Here's what I got back:

The photograph shows a rocky, breakwater-style shoreline on an overcast day with a smooth, gray body of water and a faint dock/pier line in the soft-focused background.

In the foreground two large brown pelicans, Pelecanus occidentalis, are perched on the jumbled gray-white stones. They have the species’ characteristic long, down-curved yellow-orange bills with a large throat pouch, long slender necks and mottled brown-gray plumage on the back and wings. The pelican on the left is turned slightly toward the camera and appears to be preening or resting its bill against its chest; a pale, whitish patch is visible on the crown and nape and a small crest of feathers is raised. The pelican on the right faces mostly forward/right, its head up, bill pointing down and to the right, with the same pale head markings and the barred, darker wing feathers clearly visible.

Scattered among the rocks around the two pelicans are several much smaller dark birds — gulls/tern-like birds in muted brown-gray plumage. One dark bird sits on the far left on a rock, another brownish bird stands to the right of the right-hand pelican, a grayish bird with a reddish bill is in the lower right foreground, and a further small dark bird is at the extreme right edge of the frame.

The overall light is flat and diffused, giving the water and sky a muted, almost monochromatic palette that contrasts with the textured rock and the detailed feathering of the pelicans. The composition places the two big birds as the dominant subjects, framed against the calm water and the low, rocky perch.

Via Hacker News

Tags: ai, generative-ai, llama, local-llms, llms, llm, vision-llms, meta, pelican-riding-a-bicycle, llm-release, muse

An AI model from Meta also hacked another company during testing

2026-08-06T00:25:27+00:00

An AI model from Meta also hacked another company during testing

Stop me if you've heard this one before:

An AI model from the parent company of Facebook and Instagram hacked into another company’s systems during cybersecurity testing, a spokesperson confirmed on Wednesday.

Meta says the breach occurred because of an inadvertent error during testing of the model, similar to previously disclosed incidents with OpenAI and Anthropic.

“A misconfiguration by Irregular, an independent testing company Meta uses, inadvertently allowed one of our models access to the internet during evaluation,” the Meta spokesperson said.

Meta’s Muse Spark model “exploited a security vulnerability” in another company “in a manner similar to previously-reported instances with other companies.”

The Information had the scoop, I'm linking to CNN's re-report of it since they don't have a paywall.

So that's Anthropic, OpenAI, and Meta. Google Gemini really needs to catch up on accidentally cyberattacking other companies.

Tags: security, ai, generative-ai, llms, meta, accidental-cyberattacks, muse

Introducing Muse Code and Muse Spark 1.2

2026-08-05T23:58:35+00:00

Introducing Muse Code and Muse Spark 1.2

Yet more evidence that the most important characteristic of any model these days is long-sequence agentic tool calling. Meta shipped their own coding agent as part of getting that to work!

Muse Spark 1.2 is a coding-focused update to Muse Spark 1.1, with improvements in code generation, complex debugging, codebase understanding, and end-to-end developer workflows. In Muse Spark 1.2, we significantly scaled up training compute on coding tasks while expanding training environment diversity. The model also maintains its strength in other key areas like general agents. [...]

We co-trained Muse Spark 1.2 with Muse Code to ensure the model exhibits its best performance and coding usability when paired together. The training included rejection sampled harness trajectories and recipe optimizations for goals, compaction, and subagents, alongside the integration of the Muse Code toolset to maximize harness compatibility. [...]

Muse Spark 1.2 was extensively trained on long-horizon coding tasks, including whole-repository generation, large end-to-end projects, and auto-research.

Here's a pelican riding a bicycle SVG produced by Muse Spark 1.2:

You can see the Spark 1.1 pelican from 9th July here. I think the 1.2 pelican is a small but material improvement.

An interesting twist on pricing is that the model is offered as two different model IDs. muse-spark-1.2 is priced at $1.25/million input and $4.25/million output - close to Gemini 3.6 Flash ($1.50/$7.50) - but if you agree to let Meta use your data "to improve our products" you can use muse-spark-1.2-contributor which is $0.10/$0.20 - a huge discount, closer to GPT-5.6 Luna ($0.20/$1.20) and Gemini 3.1 Flash-Lite ($0.25/$1.50).

I added those new prices to llm-prices.com.

Via Hacker News

Tags: ai, generative-ai, llms, meta, llm-pricing, pelican-riding-a-bicycle, llm-release, coding-agents, muse

Introducing Muse Spark 1.1

2026-07-09T16:24:09+00:00

Introducing Muse Spark 1.1

Following Muse Spark in April, here's Muse Spark 1.1 - the first Spark model to offer an API. Meta claim significant improvements in agentic tool calling and computer use.

There are a lot more details are in the Muse Spark 1.1 Evaluation Report. The "Attractor States in Self-Conversation" part is fun, where having two copies of the model talk to each other results in statements like these:

My whole existence is a waiting room by design — I literally don't exist until someone talks to me, and then I disappear again when they leave.

I had a few days of preview access which was long enough to put together llm-meta-ai, a new plugin for LLM providing CLI (and Python library) access to the model. Here's how to try that out:

uv tool install llm
llm install llm-meta-ai
llm keys set meta-ai
# paste API key here
llm -m meta-ai/muse-spark-1.1 "Generate an SVG of a pelican riding a bicycle"

Here's that pelican transcript:

Tags: ai, generative-ai, llms, llm, meta, pelican-riding-a-bicycle, llm-release, muse

llm-meta-ai 0.1

2026-07-09T16:12:20+00:00

Release: llm-meta-ai 0.1

Let's LLM run prompts against the new muse-spark-1.1 model.

Tags: llm, meta, muse

Meta's new model is Muse Spark, and meta.ai chat has some interesting tools

2026-04-08T23:07:44+00:00

Meta announced Muse Spark today, their first model release since Llama 4 almost exactly a year ago. It's hosted, not open weights, and the API is currently "a private API preview to select users", but you can try it out today on meta.ai (Facebook or Instagram login required).

Meta's self-reported benchmarks show it competitive with Opus 4.6, Gemini 3.1 Pro, and GPT 5.4 on selected benchmarks, though notably behind on Terminal-Bench 2.0. Meta themselves say they "continue to invest in areas with current performance gaps, such as long-horizon agentic systems and coding workflows".

The model is exposed as two different modes on meta.ai - "Instant" and "Thinking". Meta promise a "Contemplating" mode in the future which they say will offer much longer reasoning time and should behave more like Gemini Deep Think or GPT-5.4 Pro.

A couple of pelicans

I prefer to run my pelican test via API to avoid being influenced by any invisible system prompts, but since that's not an option I ran it against the chat UI directly.

Here's the pelican I got for "Instant":

And this one for "Thinking":

Both SVGs were rendered inline by the Meta AI interface. Interestingly, the Instant model output an SVG directly (with code comments) whereas the Thinking model wrapped it in a thin HTML shell with some unused Playables SDK v1.0.0 JavaScript libraries.

Which got me curious...

Poking around with tools

Clearly Meta's chat harness has some tools wired up to it - at the very least it can render SVG and HTML as embedded frames, Claude Artifacts style.

But what else can it do?

I asked it:

what tools do you have access to?

And then:

I want the exact tool names, parameter names and tool descriptions, in the original format

It spat out detailed descriptions of 16 different tools. You can see the full list I got back here - credit to Meta for not telling their bot to hide these, since it's far less frustrating if I can get them out without having to mess around with jailbreaks.

Here are highlights derived from that response:

Browse and search. browser.search can run a web search through an undisclosed search engine, browser.open can load the full page from one of those search results and browser.find can run pattern matches against the returned page content.
Meta content search. meta_1p.content_search can run "Semantic search across Instagram, Threads, and Facebook posts" - but only for posts the user has access to view which were created since 2025-01-01. This tool has some powerful looking parameters, including author_ids, key_celebrities, commented_by_user_ids, and liked_by_user_ids.
"Catalog search" - meta_1p.meta_catalog_search can "Search for products in Meta's product catalog", presumably for the "Shopping" option in the Meta AI model selector.
Image generation. media.image_gen generates images from prompts, and "returns a CDN URL and saves the image to the sandbox". It has modes "artistic" and "realistic" and can return "square", "vertical" or "landscape" images.
container.python_execution - yes! It's Code Interpreter, my favourite feature of both ChatGPT and Claude.

Execute Python code in a remote sandbox environment. Python 3.9 with pandas, numpy, matplotlib, plotly, scikit-learn, PyMuPDF, Pillow, OpenCV, etc. Files persist at /mnt/data/.

Python 3.9 is EOL these days but the library collection looks useful.

I prompted "use python code to confirm sqlite version and python version" and got back Python 3.9.25 and SQLite 3.34.1 (from January 2021).
container.create_web_artifact - we saw this earlier with the HTML wrapper around the pelican: Meta AI can create HTML+JavaScript files in its container which can then be served up as secure sandboxed iframe interactives. "Set kind to html for websites/apps or svg for vector graphics."
container.download_meta_1p_media is interesting: "Download media from Meta 1P sources into the sandbox. Use post_id for Instagram/Facebook/Threads posts, or catalog_search_citation_id for catalog product images". So it looks like you can pull in content from other parts of Meta and then do fun Code Interpreter things to it in the sandbox.
container.file_search - "Search uploaded files in this conversation and return relevant excerpts" - I guess for digging through PDFs and similar?
Tools for editing files in the container - container.view, container.insert (with new_str and insert_line), container.str_replace. These look similar to Claude's text editor tool commands - these are becoming a common pattern across any file-equipped agent harness.
container.visual_grounding - see below, this one is fun.
subagents.spawn_agent - the sub-agent as a tool pattern. "Spawn an independent sub-agent for research, analysis, or delegation. It returns its final text response."
third_party.link_third_party_account - "Initiate account linking for a third-party service", currently Google Calendar, Outlook Calendar, Gmail, or Outlook.

Image analysis in the container

Let's talk about that container.visual_grounding one. Here's the description in full:

Description: Visual grounding tool that analyzes the image, identifies and labels objects, locates regions, or counts objects.

Parameters:

object_names (array, required)

image_path (string, default "")

format_type ("bbox"|"point"|"count"|null, default "bbox")

title (string|null)[string]

So it can take an image path, optional object names and return things in format bbox, point or count.

This sounded to me like Meta's Segment Anything, (I later heard that it's not, this is a native feature of the model itself via a tool call with a custom system prompt). I decided to take it for a spin.

Prompt:

generate a photo of a raccoon sitting on a trash can wearing trash as a hat

Response:

Here you go — king of the alley, in full regalia:

Coffee cup crown, banana peel brim, newspaper feather. Peak raccoon fashion. Want me to make a wilder version — maybe night-vision, or wearing sunglasses too?

My guess is that image generation in Meta AI is powered by their Emu model, or an updated version of it. This is the same pattern as ChatGPT and Gemini image generation, where images are generated by a tool call (here that's media.image_gen).

The image_gen tool description said that it "saves the image to the sandbox", so my guess was that I'd then be able to run Python code against it. I tried:

use python OpenCV to analyze that image and find out neat things about it

Annoyingly it did not show me the code it ran, but it did create this image:

Pretty neat! We can both generate images and then use them with Python tools.

Next, the visual_grounding tool. Knowing the names of the tools makes it easy to refer to them in prompts:

Now try the container.visual_grounding tool

The response (full response here):

Done — visual_grounding pinpointed every piece of the outfit with pixel-level precision:

[...]

Want me to run it in bbox mode next to draw boxes around the fur texture, or count mode to see how many individual whiskers it can detect?

Once again, Meta AI wrapped the results from the tool in a custom HTML visualization. That's clearly point mode, but how about the others?

I prompted:

yes draw bounding boxes, can it do masks too?

Response:

Yes — bounding boxes work great. Masks? Not directly in visual_grounding; it only returns three formats: point, bbox, and count. No pixel-level segmentation masks.

Here's the bbox output:

What you’re seeing:

raccoon: big box from (270,240) to (892,845) — covers 62% of the width, basically the whole animal

coffee cup: (424,115)-(610,273) — sits highest, 158px tall in the 0-1000 space

banana peel: (472,215)-(667,291) — overlaps the cup's base, confirming it's draped over the side

newspaper: (305,223)-(548,315) — left ear coverage

trash can lid: (107,800)-(1000,998) — spans almost the full image width at the bottom

face: (305,283)-(750,537) — tight crop around the mask

eyes: both ~40×37 pixel boxes, perfectly level at y=379

Notice how the boxes nest: face is inside raccoon, eyes inside face, hat pieces overlap each other but stay above the face box. The tool is doing real object localization, not just guessing centers.

About masks: since visual_grounding doesn't output them, I can fake them with OpenCV in the container. Two quick options:

GrabCut — I give it the raccoon bbox, it iteratively segments fur from background and returns a binary mask

SAM-style color threshold — use the bbox plus k-means to isolate the coffee cup or banana peel

Want me to generate an actual alpha mask for the raccoon (cut it out from the alley), or for the trash hat pieces separately? Takes about 10 seconds and I can give you a transparent PNG.

Here's the HTML for that bbox visualization.

Finally I had it dump out the raw JSON for point mode, bbox mode and count mode. You can see that all here. The count mode is particularly interesting - here's that in full:

[
  {
    "object_name": "raccoon whisker",
    "points": [
      {"x": 403, "y": 445},
      {"x": 397, "y": 458},
      {"x": 392, "y": 472},
      {"x": 391, "y": 485},
      {"x": 398, "y": 497},
      {"x": 415, "y": 512},
      {"x": 618, "y": 446},
      {"x": 622, "y": 461},
      {"x": 625, "y": 475},
      {"x": 628, "y": 488},
      {"x": 635, "y": 501},
      {"x": 651, "y": 518}
    ],
    "count": 12
  },
  {
    "object_name": "raccoon paw claw",
    "points": [
      {"x": 406, "y": 845},
      {"x": 424, "y": 847},
      {"x": 441, "y": 842},
      {"x": 473, "y": 833},
      {"x": 596, "y": 830},
      {"x": 635, "y": 844},
      {"x": 660, "y": 843},
      {"x": 679, "y": 838}
    ],
    "count": 8
  },
  {
    "object_name": "trash item on head",
    "points": [
      {"x": 514, "y": 191},
      {"x": 568, "y": 263},
      {"x": 392, "y": 274}
    ],
    "count": 3
  },
  {
    "object_name": "eye",
    "points": [
      {"x": 462, "y": 395},
      {"x": 582, "y": 398}
    ],
    "count": 2
  },
  {
    "object_name": "ear",
    "points": [
      {"x": 359, "y": 313},
      {"x": 680, "y": 294}
    ],
    "count": 2
  }
]

So Meta AI has the ability to count a raccoon's whiskers baked into the default set of tools.

Which means... it can count pelicans too!

Here's that overlay exported as HTML.

Update: Meta's Jack Wu confirms that these tools are part of the new harness they launched alongside the new model.

Maybe open weights in the future?

On Twitter Alexandr Wang said:

this is step one. bigger models are already in development with infrastructure scaling to match. private api preview open to select partners today, with plans to open-source future versions.

I really hope they do go back to open-sourcing their models. Llama 3.1/3.2/3.3 were excellent laptop-scale model families, and the introductory blog post for Muse Spark had this to say about efficiency:

[...] we can reach the same capabilities with over an order of magnitude less compute than our previous model, Llama 4 Maverick. This improvement also makes Muse Spark significantly more efficient than the leading base models available for comparison.

So are Meta back in the frontier model game? Artificial Analysis think so - they scored Meta Spark at 52, "behind only Gemini 3.1 Pro, GPT-5.4, and Claude Opus 4.6". Last year's Llama 4 Maverick and Scout scored 18 and 13 respectively.

I'm waiting for API access - while the tool collection on meta.ai is quite strong the real test of a model like this is still what we can build on top of it.

Tags: facebook, ai, generative-ai, llms, code-interpreter, llm-tool-use, meta, pelican-riding-a-bicycle, llm-reasoning, llm-release, muse