Show HN: Ktx – Open-source executable context layer for data agents
We built it after going through the experience of building production-grade data agents for dozens of companies. If you’ve also tried building them, or simply tried using Claude Code or Codex on your data warehouse, you’ll know that accuracy is the #1 issue. Agents are great at generating valid SQL, but it’s not always correct SQL.
To cite a few examples of “agents gone wrong”: - Stale column + hidden business rule: when preparing a board report, a finance analyst asks Claude Code for “ARR by customer segment”, it derives ARR from multiple tables (subscriptions, plans, accounts), then groups by accounts.industry. But CC doesn’t know that this industry column was deprecated a few months prior, or that past board reports excluded paused subscriptions from the ARR calculation - Join fanout: a data analyst at a retailer uses their company’s internal agent to prep a product revenue deck for a QBR. The agent joins orders to order_items, then sums orders.total_amount_cents grouped by order_items.product_id. The SQL runs fine, but each order’s revenue is repeated once per line item, which most people will miss if most orders only have 1 item - Missing attribution logic: a marketing analyst asks Codex “Which campaigns drove the most revenue?” Codex joins marketing_touches to users to orders and groups by utm_campaign. But since each order can have multiple touches before purchase, the same order can be credited to first touch, last touch, every touch, or every campaign the user clicked before buying. If the agent chooses the method that doesn’t match the team’s attribution logic, they’ll make suboptimal decisions
To solve this at first we gave the agent more context through skills + a wiki-style knowledge base. That gives it some useful extra context but still relies on it writing the SQL without incorrect assumptions.
The next solution we explored was implementing a classic semantic layer. That solves the executable part, but they’re such a pain to build and maintain since they were made for legacy BI tools. Plus as a standalone tool, they lack all the useful context from unstructured data sources like internal docs.
So we built ktx and split it into 2 parts: 1. Business context goes in Markdown wiki pages that are auto-ingested and auto-populated 2. Queryable definitions go into YAML files that define tables, row grain, joins, measures, dimensions, filters, and filter groups
That way, when an agent needs a metric, it asks ktx for a measure, dimensions, filters, and filter groups instead of writing the whole query itself. ktx’s planner chooses the join path, uses grain and relationship metadata, catches issues like join fanout and chasm joins, and compiles the warehouse SQL, while utilizing the extra unstructured knowledge it has access to.
ktx is Apache 2.0. It can ingest from most warehouses (BigQuery, Snowflake, Postgres & others), modeling tools (dbt, MetricFlow, LookML), BI tools (Looker, Metabase), doc tools like Notion, and corrections from user interactions.
Install manually: npm install -g @kaelio/ktx ktx setup
Or give this prompt to your agent: Run npx skills add Kaelio/ktx --skill ktx and use ktx skill to install and configure ktx
We’d especially like feedback from people who’ve tried using Claude Code, Codex, or building custom agents on analytics warehouses. Where did they fail? And what did you try to make the answers more reliable?
The way we think about the space: there's a "semantic layer" side (Cube, dbt MetricFlow, Wren's engine) that compiles correct SQL but is hand-authored. And a "company brain" side (OpenViking, Glean, wikis) that indexes prose but can't query data warehouses safely. ktx is built to be both halves at once - a YAML semantic layer and a searchable wiki of business definitions, cross-linked (each wiki page references the metrics it explains) and auto-maintained
As for the business context evolution - that's exactly the reason we have ingestion reconciliation and git versioning. The idea is to give ingestion agent a way to deduplicate/consolidate knowledge during the ingestion and leave complex conflicts to humans to resolve
It’s just that making such docs had next to no ROI 10 years ago. But today they are the difference between success and failure.
It’s fascinating - thank you
(and who writes the wiki / business rules ? Can they be reverse engineered from existing query stack? )
Sounds great - all the best
Edit: don’t take the above as criticism - just trying to fit new ideas into an old dog.
The second (equally important) part of ktx is similarly self-organizing executable semantic layer.
It allows agents to send simple declarative "I want X sliced by Y" requests instead of imperative "X sliced by Y that has to be queried this way and joined the other way ..."
To answer your questions:
> who writes the wiki / business rules most is create after `ktx ingest` pulls raw data from your data stack, it can be edited/created manually, but it's rarely necessary. Also if you plug ktx to your agent it allows that agent to send extra memories for ingestion to keep the context up to date
> Can they be reverse engineered from existing query stack Yes, that's the case when we analyze historic SQL queries or scan Looker or Metabase dashboards for example
So you define the definitions of metrics like "monthly revenue" once, and that definition is runnable. If an agent asks for "monthly revenue by region", the semantic layer will compile that request into SQL and run it (the same way everytime so that calculation method is consistent)
On nao: it's solving an adjacent but different problem, it's a full analytics app, whereas we believe that the general purpose agents (e.g. Claude Desktop) are getting better at the representation layer generating widgets and that's where people work anyway. What these agents need is a solid foundation - this is what we're focusing on. ktx isn't an agent or UI, it's an executable institutional knowledge that keeps any analyst (nao, Claude, Codex, your own agent) from guessing which table is canonical or which join is safe.
And better comparisons from the semantic layer space are tools like Wren, Cube, dbt MetricFlow
Does `ktx setup` need Claude specifically?
> LLM - picks a Claude backend. The default uses your local Claude Code session, so no API key is required. You can also use an Anthropic API key or Vertex AI.
I'm currently on Copilot at work
I'm skim reading the docs but I just want to know a bit more about the architecture
Does it produce artefacts that I can commit to version control and share with my team? Is it a tool that everyone runs locally in the project? Or there's a component (the wiki?) that I should deploy as an internal service?
ktx project directory is self-contained. The main 2 parts inside are :
- wiki: a collection of .md files
- semantic-layer: a collection of .yaml files
typically all these files are created/edited automatically during the ingestion, but you can also edit them by hand or even sync with a remote git.
ktx treats these files as sources and builds internal indexes in a sqlite db, located in projectDir/.ktx
The main way to use ktx is to start an mcp server by calling `ktx mcp start` it'll start an http server and multiple people will be able to connect it to their agents.
Hope this helps, happy to answer any other questions!
We don't have a manual compression yet, it's part of our other product that ktx used to be a part of before it became open-source. But we decided to move that feature to OSS too, so expect it to come out in the next releases !
some observations: setup (without openai embeddings) was pretty easy. Nice! Not sure why it took ~19 minutes for a postgres database with 20sh tables. Also the data from pg_desc did not get into the wiki
I am going to try to embed it in our agentic flow and see how it fits. Very cool project though.
As for the descriptions: `pg_description` should be used already, we store raw pg descriptions in the semantic-layer/<connection>/_schema/*.yaml files under descriptions.db. there's also an AI generated description next to it. AI is the combination of the raw DB description + bunch of metadata we manage to collect about a table/column.
could you run `ktx sl` and see if the descriptions appear in the CLI ?
also feel free to join our community Slack - ktx.sh/slack We'll be happy to help with other questions
we always like chatting with folks that have tried building similar projects in the past