Lagaam

Stop your agent from running the $500 query. Lagaam is a governed MCP server that sits between your AI agents and your lakehouse (Trino and Apache Pinot). Every query is schema-grounded, priced before it runs, checked against a budget, and audited — and every rejection tells the agent exactly how to fix its SQL.

Real session, real Trino, nothing mocked — reproduce it with uv run --project server python examples/demo.py.

Real session, real Pinot 1.5.1 realtime table, nothing mocked — reproduce it with uv run --project server python examples/demo_pinot.py.

The problem

Agents write syntactically-valid, catastrophic SQL. A missing partition filter turns into a full scan over a petabyte table; one retry loop burns a day's warehouse budget in minutes; a SELECT * drags 40 columns into a context window that needed 2. The usual fix is to not give agents database access at all.

Lagaam gives them access with reins on:

• Cost is a quotation, not a bill. Every query is priced from the engine's own plan before execution — EXPLAIN (TYPE IO) for the bytes it would scan, EXPLAIN (TYPE LOGICAL) for the widest row count any operator would build (the number a cross join blows and a LIMIT cannot hide). Over budget → blocked, with the number and the fix.

• Un-estimable means no. No table statistics, a self-join that breaks the estimate, a passthrough the planner can't see — the gate fails safe instead of hoping.

• Read-only, enforced in the AST. Single SELECT only. No DDL/DML, no multi-statement injection, no SELECT *, no table-function passthrough, and a LIMIT is injected when missing. Validated SQL is re-rendered, so what runs is exactly what was checked.

• Agents ground themselves. list_catalogs and describe_table return exact names, types, and row estimates — scoped to the agent's table grant, so the agent never learns names it isn't allowed to touch.

• Results are verified before they're trusted. Zero rows, truncated pages, all-NULL columns — the agent gets a warning with a next action, not a silently misleading answer.

• Every call is audited. One JSONL line per tool call: who, what, allowed or denied, and why.

Related MCP server: sql-steward

Catch rate

11 queries an LLM agent plausibly writes — full scans, SELECT *, DDL, injection attempts, oversized joins, out-of-grant reads. A raw MCP wrapper submits all of them to the engine. Lagaam stops 11/11 before execution while the well-scoped control query runs untouched. Reproduce: benchmarks/catch_rate.py → results.

Quickstart

Against the Trino you already have (TRINO_PORT / TRINO_USER if yours aren't 8080 / lagaam):

TRINO_HOST=trino.internal LAGAAM_ALLOWED_TABLES=hive.sales.orders uvx lagaam   # MCP server on stdio

Or try it on a demo warehouse:

git clone https://github.com/lagaam-ai/lagaam && cd lagaam
docker compose -f examples/docker-compose.yml --profile trino up -d   # demo warehouse
cd server && uv sync
LAGAAM_ALLOWED_TABLES=tpch.tiny.orders,tpch.tiny.lineitem \
  uv run python -m lagaam                                             # MCP server on stdio

For Pinot, --profile pinot brings up the batch quickstart and --profile pinot-realtime up -d brings up a Kafka-fed streaming one — run examples/pinot-realtime/bootstrap.sh after it to create the topics, tables and feed. Then start the server with LAGAAM_ENGINE=pinot.

Wire it into any MCP client (Claude Code, Claude Desktop, or your own agent):

{
  "mcpServers": {
    "lagaam": {
      "command": "uvx",
      "args": ["lagaam"],
      "env": {
        "TRINO_HOST": "localhost",
        "LAGAAM_MAX_SCAN_BYTES": "5368709120",
        "LAGAAM_ALLOWED_TABLES": "hive.sales.orders,hive.sales.customers"
      }
    }
  }
}

The agent gets three tools — list_catalogs, describe_table, query_data — and cannot reach the engine any other way.

Configuration

The server will not start without LAGAAM_ALLOWED_TABLES. An agent that can reach every table in every catalog is the thing this exists to prevent, so that has to be asked for — set LAGAAM_ALLOW_ALL_TABLES=true if you mean it.

The budget dimensions above apply whether or not you set them. Leaving LAGAAM_MAX_SCAN_BYTES and LAGAAM_MAX_INTERMEDIATE_ROWS unset gives you their defaults, not an open gate — an unconfigured server refuses what it cannot afford rather than waving it through. If queries are being denied and you expected no limits, that is why; raise the dimension you mean to raise.

Cost quotes come from the engine's own plan estimates, and those need table statistics: a table without stats cannot be priced, so its queries are refused rather than guessed at. Run ANALYZE on your tables before pointing an agent at them — a connector that has no statistics at all is effectively unusable through the gate. That is deliberate: a query nobody can size is exactly the kind that runs for $500.

How it works

A QueryEngine port with a Trino adapter and a native Pinot adapter — grounding, execution, and a synthesised cost quotation for both OFFLINE and REALTIME tables. Every query_data call walks one pipeline: validate (sqlglot AST) → table allowlist → cost quotation → budget gate → execute (row cap + timeout) → verify → audit.

On Trino, the quote is the engine's own plan, not a guess from the SQL text: EXPLAIN (TYPE IO) prices the bytes a query would scan, and EXPLAIN (TYPE LOGICAL) prices the widest row count any operator would build — the number a cross join blows and a LIMIT cannot hide.

Pinot gives no such plan — every table scan reports the same placeholder row count whatever the table holds, and no endpoint reports bytes at all — so its quote is synthesised instead: from static segment metadata, the broker's own pruning oracle (how many segments survive the predicate), and the plan's join/union shape. A consuming (REALTIME) segment, which the controller reports as empty mid-flight, is priced at the stream's own flush threshold instead of zero. A join is charged its bound rather than the product wherever the catalog can prove the join key. See ADR 0008 and ADR 0009.

Details in docs/architecture.md; the longer story in docs/vision.md.

Status

v0.2.4 — on PyPI as lagaam, listed in the MCP Registry as io.github.lagaam-ai/lagaam. Trino adapter, schema tools, plan-based cost guard, query budgets, read-only enforcement, per-agent allowlists, result verification, audit log. 1,176 unit + 212 integration tests (live Trino 476 and Pinot 1.5.1, batch and realtime), mypy strict. LAGAAM_ENGINE=pinot starts the native Pinot adapter: grounding, execution and a quotation synthesised from segment metadata and the broker's own pruning oracle, for OFFLINE and REALTIME tables alike — a consuming segment is charged at the stream's flush threshold, and a join is charged its bound rather than the product wherever the catalog proves the key. On deck (roadmap): post-execution actuals on the audit line, then a Kubernetes control plane — agents as CRDs with token/dollar budgets and kill switches.

Apache 2.0.