Simon Willison’s Weblog

Nomic Embed Code: A State-of-the-Art Code Retriever. Nomic have released a new embedding model that specializes in code, based on their CoRNStack "large-scale high-quality training dataset specifically curated for code retrieval".

The nomic-embed-code model is pretty large - 26.35GB - but the announcement also mentioned a much smaller model (released 5 months ago) called CodeRankEmbed which is just 521.60MB.

I missed that when it first came out, so I decided to give it a try using my llm-sentence-transformers plugin for LLM.

llm install llm-sentence-transformers
llm sentence-transformers register nomic-ai/CodeRankEmbed --trust-remote-code

Now I can run the model like this:

llm embed -m sentence-transformers/nomic-ai/CodeRankEmbed -c 'hello'

This outputs an array of 768 numbers, starting [1.4794224500656128, -0.474479079246521, ....

Where this gets fun is combining it with my Symbex tool to create and then search embeddings for functions in a codebase.

I created an index for my LLM codebase like this:

cd llm
symbex '*' '*.*' --nl > code.txt

This creates a newline-separated JSON file of all of the functions (from '*') and methods (from '*.*') in the current directory - you can see that here.

Then I fed that into the llm embed-multi command like this:

llm embed-multi \
  -d code.db \
  -m sentence-transformers/nomic-ai/CodeRankEmbed \
  code code.txt \
  --format nl \
  --store \
  --batch-size 10

I found the --batch-size was needed to prevent it from crashing with an error.

The above command creates a collection called code in a SQLite database called code.db.

Having run this command I can search for functions that match a specific search term in that code collection like this:

llm similar code -d code.db \
  -c 'Represent this query for searching relevant code: install a plugin' | jq

That "Represent this query for searching relevant code: " prefix is required by the model. I pipe it through jq to make it a little more readable, which gives me these results.

This jq recipe makes for a better output:

llm similar code -d code.db \
  -c 'Represent this query for searching relevant code: install a plugin' | \
  jq -r '.id + "\n\n" + .content + "\n--------\n"'

The output from that starts like so:

llm/cli.py:1776

@cli.command(name="plugins")
@click.option("--all", help="Include built-in default plugins", is_flag=True)
def plugins_list(all):
    "List installed plugins"
    click.echo(json.dumps(get_plugins(all), indent=2))
--------

llm/cli.py:1791

@cli.command()
@click.argument("packages", nargs=-1, required=False)
@click.option(
    "-U", "--upgrade", is_flag=True, help="Upgrade packages to latest version"
)
...
def install(packages, upgrade, editable, force_reinstall, no_cache_dir):
    """Install packages from PyPI into the same environment as LLM"""

Getting this output was quite inconvenient, so I've opened an issue.

# 27th March 2025, 8:03 pm / nomic, llm, ai, embeddings, jq

Nomic Embed Text V2: An Open Source, Multilingual, Mixture-of-Experts Embedding Model (via) Nomic continue to release the most interesting and powerful embedding models. Their latest is Embed Text V2, an Apache 2.0 licensed multi-lingual 1.9GB model (here it is on Hugging Face) trained on "1.6 billion high-quality data pairs", which is the first embedding model I've seen to use a Mixture of Experts architecture:

In our experiments, we found that alternating MoE layers with 8 experts and top-2 routing provides the optimal balance between performance and efficiency. This results in 475M total parameters in the model, but only 305M active during training and inference.

I first tried it out using uv run like this:

uv run \
  --with einops \
  --with sentence-transformers \
  --python 3.13 python

Then:

from sentence_transformers import SentenceTransformer
model = SentenceTransformer("nomic-ai/nomic-embed-text-v2-moe", trust_remote_code=True)
sentences = ["Hello!", "¡Hola!"]
embeddings = model.encode(sentences, prompt_name="passage")
print(embeddings)

Then I got it working on my laptop using the llm-sentence-tranformers plugin like this:

llm install llm-sentence-transformers
llm install einops # additional necessary package
llm sentence-transformers register nomic-ai/nomic-embed-text-v2-moe --trust-remote-code

llm embed -m sentence-transformers/nomic-ai/nomic-embed-text-v2-moe -c 'string to embed'

This outputs a 768 item JSON array of floating point numbers to the terminal. These are Matryoshka embeddings which means you can truncate that down to just the first 256 items and get similarity calculations that still work albeit slightly less well.

To use this for RAG you'll need to conform to Nomic's custom prompt format. For documents to be searched:

search_document: text of document goes here

And for search queries:

search_query: term to search for

I landed a new --prepend option for the llm embed-multi command to help with that, but it's not out in a full release just yet. (Update: it's now out in LLM 0.22.)

I also released llm-sentence-transformers 0.3 with some minor improvements to make running this model more smooth.

# 12th February 2025, 10:24 pm / embeddings, llm, nomic, ai, rag, uv, python

llm-gpt4all. New release of my LLM plugin which builds on Nomic's excellent gpt4all Python library. I've upgraded to their latest version which adds support for Llama 3 8B Instruct, so after a 4.4GB model download this works:

llm -m Meta-Llama-3-8B-Instruct "say hi in Spanish"

# 20th April 2024, 5:58 pm / nomic, llm, plugins, projects, generative-ai, ai, llms, llama, local-llms

llm-nomic-api-embed. My new plugin for LLM which adds API access to the Nomic series of embedding models. Nomic models can be run locally too, which makes them a great long-term commitment as there’s no risk of the models being retired in a way that damages the value of your previously calculated embedding vectors.

# 31st March 2024, 3:17 pm / llm, plugins, projects, nomic, ai, embeddings

Adaptive Retrieval with Matryoshka Embeddings (via) Nomic Embed v1 only came out two weeks ago, but the same team just released Nomic Embed v1.5 trained using a new technique called Matryoshka Representation.

This means that unlike v1 the v1.5 embeddings are resizable—instead of a fixed 768 dimension embedding vector you can trade size for quality and drop that size all the way down to 64, while still maintaining strong semantically relevant results.

Joshua Lochner build this interactive demo on top of Transformers.js which illustrates quite how well this works: it lets you embed a query, embed a series of potentially matching text sentences and then adjust the number of dimensions and see what impact it has on the results.

# 15th February 2024, 4:19 am / transformers-js, nomic, ai, embeddings, llms

llm-sentence-transformers 0.2. I added a new --trust-remote-code option when registering an embedding model, which means LLM can now run embeddings through the new Nomic AI nomic-embed-text-v1 model.

# 4th February 2024, 7:39 pm / llm, embeddings, plugins, projects, ai, transformers, nomic

Introducing Nomic Embed: A Truly Open Embedding Model. A new text embedding model from Nomic AI which supports 8192 length sequences, claims better scores than many other models (including OpenAI’s new text-embedding-3-small) and is available as both a hosted API and a run-yourself model. The model is Apache 2 licensed and Nomic have released the full set of training data and code.

From the accompanying paper: “Full training of nomic-embed-text-v1 can be conducted in a single week on one 8xH100 node.”

# 3rd February 2024, 11:13 pm / ai, embeddings, nomic