Show HN: Semble – Code search for agents that uses 98% fewer tokens than grep
60 points by Bibabomas 7 hours ago | 18 comments
Hey HN! We (Stephan and Thomas) recently open-sourced Semble. We kept running into the same problem while using Claude Code on large codebases: when the agent can't find something directly, it falls back to grep, reading full files or launching subagents. This uses a lot of tokens, and often still misses the relevant code. There are existing tools for this, but they were either too slow to index on demand, needed API keys, or had poor retrieval quality.

Semble is our solution for this. It combines static Model2Vec embeddings (using our latest static model: potion-code-16M) with BM25, fused via RRF and reranked with code-aware signals. Everything runs on CPU since there's no transformers involved. On our benchmark of ~1250 query/document pairs across 63 repos and 19 languages, it uses 98% fewer tokens than grep+read and reaches 99% of the retrieval quality of a 137M-parameter code-trained transformer, while being ~200x faster.

Main features:

- Token-efficient: 98% fewer tokens than grep+read

- Fast: ~250ms to index a typical repo on our benchmark, ~1.5ms per query on CPU (very large repos may take longer)

- Accurate: 0.854 NDCG@10, 99% of the best transformer setup we tested

- MCP server: drop-in for Claude Code, Cursor, Codex, OpenCode

- Zero config: no API keys, no GPU, no external services

Install in Claude Code with: claude mcp add semble -s user -- uvx --from "semble[mcp]" semble

Or check our README for other installation instructions, benchmarks, and methodology:

Semble: https://github.com/MinishLab/semble

Benchmarks: https://github.com/MinishLab/semble/tree/main/benchmarks

Model: https://huggingface.co/minishlab/potion-code-16M

Let us know if you have any feedback or questions!


jerezzprime 2 hours ago
I'd be interested in seeing actual agent benchmarks (eg CC or Copilot CLI with grep removed and this tool instead).

For example, I have explored RTK and various LSP implementations and find that the models are so heavily RL'd with grep that they do not trust results in other forms and will continually retry or reread, and all token savings are lost because the model does not trust the results of the other tools.

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giancarlostoro 52 minutes ago
I forced Claude to have a global memory for RTK and my own AI memory system (GuardRails) which it happily uses both, the only times it doesnt use GuardRails is if I dont mention it at all, otherwise it always uses RTK unless RTK falls apart running a tool it does not support.
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stephantul 2 hours ago
Yeah we're also interested in doing this, it's on the roadmap together with optimization of the prompt and descriptions so that models have an easier time using it.

Perhaps anecdotally: we do use this tool ourselves of course, and it's been working pretty well so far. Anthropic models call it and seem to trust the results.

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singpolyma3 43 minutes ago
Semantic code search seems like a useful tool for a human too. Not just for agents.
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smcleod 29 minutes ago
How does it compare to context-mode or serina that are both well established now?
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esafranchik 5 hours ago
Is the benchmark measuring one-shot retrieval accuracy, or Coding agent response accuracy?
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stephantul 5 hours ago
Hey! Co-author here. The benchmark currently only measures retrieval accuracy.

We’re interested in measuring it end to end and also optimizing, e.g. the prompt and tools, for this, but we just haven’t gotten around to it.

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esafranchik 4 hours ago
Two follow-ups:

1) How do you compare accuracy? by checking if the answer is in any of the returned grep/bm25/semble snippets?

2) How do you measure token use without the agent, prompt, and tools?

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stephantul 4 hours ago
1) yes! It’s not accuracy, but ndcg 2) we assume that if the agent gets the correct answer in the returned snippets it does not need to read further
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esafranchik 4 hours ago
Wouldn't NDCG/token results vary wildly depending on the agent's query and the number of returned items?

e.g. agents often run `grep -m 5 "QUERY"` with different queries, instead of one big grep for all items.

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stephantul 4 hours ago
The same holds for semble: the agent can fire off many different semble queries with different k/parameters.

I guess the point we’re trying to make is that you need fewer semble queries to achieve the same outcome, compared to grep+readfile calls.

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mrpf1ster 4 hours ago
Does this work well for non-coding documents as well? Say api docs or AI memory files?
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stephantul 4 hours ago
Hey, this is something we're actively investigating. We recently added a flag, `--include-text-files`, which, when set, also makes Semble index regular documents (i.e., markdown, text, json). This should also work relatively well.
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ludicrousdispla 4 hours ago
grep doesn't need tokens, so what is 98% fewer than zero?
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stephantul 4 hours ago
You need readfile to do something with those tokens. Grep only gives you the matching lines, not the context.
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djaboss 3 hours ago
`grep -C $NUM` ? ;)
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stephantul 3 hours ago
Even so. Take a look at the NDCG numbers for grep. It's not pretty
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vikeri 34 minutes ago
very curious to give it a spin but why write a cli in python? would surely be faster and more portable with go or rust?
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