Introducing Kanon 2 Reranker
Umar Butler
Founder, CEO
tl;dr
We’re releasing Kanon 2 Reranker, the most powerful reranking model for legal RAG to date.
Kanon 2 Reranker ranks first on Legal RAG Bench, outperforming Qwen 3 Reranker 8B by 9% and Voyage Rerank 2.5 by 7%.
Uniquely, Kanon 2 Reranker supports an infinite context window thanks to our semchunk semantic chunking library.
Kanon 2 Reranker is available for use today via the Isaacus API, priced the same as Kanon 2 Embedder at US$0.35 per million tokens.
16 March 2026**:** Kanon 2 Reranker can now be self-hosted via the AWS Marketplace.
Isaacus Voyage Qwen
Kanon 2
Reranker Reranker 
Voyage Rerank
2.5 Reranker 
Qwen Reranker
8B Reranker Kanon 2
Embedder Embedder Voyage 4
Large Embedder
A comparison of reranker and embedding models on Legal RAG Bench. Scores are NDCG@10. Rerankers were evaluated alongside Kanon 2 Embedder as a first-stage retriever, sampling the top 100 passages for each query.
Kanon 2 Reranker is the most powerful reranker for legal RAG
As the first reranker optimized specifically for legal RAG, Kanon 2 Reranker excels at scoring the relevance of laws, decisions, contracts, evidence, and other legal documents to queries in legal RAG applications.
When paired with our state-of-the-art legal embedding model, Kanon 2 Embedder, as a fast, affordable, and accurate first-stage retriever, Kanon 2 Reranker delivers 18% better legal information retrieval performance on Legal RAG Bench and 6% better performance on Massive Legal Embedding Benchmark (MLEB).
On Legal RAG Bench, Kanon 2 Reranker is also 7% more accurate than Voyage Rerank 2.5, 9% more accurate than Qwen 3 Reranker 8B, and 24% more accurate than Voyage 4 Large.
For a practical example of how better retrieval translates into real-world improvements in legal RAG quality, consider the below example, where Kanon 2 Reranker enables GPT-5.2 to correctly answer a question that it fails to answer when paired with Voyage Rerank 2.5.
Question
Chris is on trial for intentionally or recklessly causing a bushfire. His counsel says he was carrying out a “cool burn.” Talia, a First Nations woman, is called to explain First Nations practices. Is Talia’s evidence admissible?
Kanon 2 Reranker Isaacus Yes. Expert opinion evidence is admissible if “wholly or substantially based on specialised knowledge” from training, study or experience (Evidence Act 2008 s 79), and the bench book also recognises an exception for “evidence about the existence or content of Aboriginal and Torres Strait Islander traditional laws and customs (s 78A)” (DOC: 4.13.1-c2-s1).
Retrieved evidence
#1 4.13.1 Admissibility of Opinion Evidence Answer 4.13.1-c2-s1 #2 4.13.1 General Principles of Opinion Evidence 4.13.1-c1-s2 #3 4.17 Admissibility of Evidence Capable of Proving a Tendency 4.17-c3-s1 #4 4.19 Determining the Relevance of Evidence 4.19-c3-s1 #5 4.13.1 General Principles of Opinion Evidence 4.13.1-c1-s3
Rerank 2.5 Voyage No. The provided charge book material for intentionally or recklessly causing a bushfire only sets out the three elements and the relevant states of mind (“aware that … would probably cause a fire/spread”) and contains no rule making cultural practice evidence admissible (DOC: 7.5.21.1-c1-s1; DOC: 7.5.21.1-c2-s1; DOC: 7.5.21.2-c1-s1).
Retrieved evidence
#1 7.5.21.1 Charge: Intentionally or Recklessly Causing a Bushfire 7.5.21.1-c1-s1 #2 7.5.21.2 Checklist: Intentionally or Recklessly Causing a Bushfire 7.5.21.2-c1-s1 #3 7.5.21 Elements 7.5.21-c2-s1 #4 7.5.21.1 Intentionally or recklessly causing a fire 7.5.21.1-c2-s1 #5 7.5.20.1 Intention to Damage or Destroy Property by Fire 7.5.20.1-c3-s1
A side-by-side comparison of how Kanon 2 Reranker performs on Legal RAG Bench relative to Voyage Rerank 2.5 in an end-to-end legal RAG pipeline, with GPT-5.2 used to generate answers.
Uniquely, unlike its closest competitors, Kanon 2 Reranker boasts first-class support for documents of any length powered by our semchunk semantic chunking library.
We have made Kanon 2 Reranker publicly available through the Isaacus API at the same price as Kanon 2 Embedder: US$0.35 per million tokens.
To get started building your own awesome legal AI applications with Kanon 2 Reranker, check out our usage guide.
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