[brandon-pereira]

Summary

MCP query tools (clickstack_sql, clickstack_timeseries, clickstack_table, clickstack_search, clickstack_query_tile) now enforce ClickHouse safety limits that were previously missing. A runaway agent-supplied query could hold a connection for up to 1 hour (the default requestTimeout) with no row cap and no protection against DDL/DML injection.

Closes HDX-4476

What changed

A single constant governs all MCP query execution in runConfigTile():

Setting	Value	Purpose
max_execution_time	30s	Kills long-running queries — matches eventDeltas, eventPatterns, Prometheus
max_result_rows	100,000	Prevents serialization OOM on the Node process — matches Prometheus
readonly	1	Blocks CREATE, INSERT, ALTER, DROP — matches trace tools
requestTimeout	32s	HTTP timeout = 30s + 2s buffer for clean ClickHouse error — matches external API pattern

Applied to both the builder config path and the raw SQL path. The settings constant is shared so they can't drift.

Tests

Integration tests against real ClickHouse verify actual enforcement:

• readonly — CREATE TABLE, INSERT, and DROP TABLE via clickstack_sql are rejected with a readonly error; SELECT still works
• max_execution_time — sleep(3) with max_execution_time: 1 throws TIMEOUT_EXCEEDED

[changeset-bot]

🦋 Changeset detected

Latest commit: 02c4fc6

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 3 packages

Name	Type
@hyperdx/api	Patch
@hyperdx/app	Patch
@hyperdx/otel-collector	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

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Project	Deployment	Actions	Updated (UTC)
hyperdx-oss	Ready	Preview, Comment	Jun 8, 2026 11:36pm
hyperdx-storybook	Ready	Preview, Comment	Jun 8, 2026 11:36pm

[github-actions]

🔵 Tier 2 — Low Risk

Small, isolated change with no API route or data model modifications.

Why this tier:

• Standard feature/fix — introduces new logic or modifies core functionality

Review process: AI review + quick human skim (target: 5–15 min). Reviewer validates AI assessment and checks for domain-specific concerns.
SLA: Resolve within 4 business hours.

Stats

• Production files changed: 1
• Production lines changed: 26 (+ 120 in test files, excluded from tier calculation)
• Branch: brandon/brandon-mcp-sql-tweaks
• Author: brandon-pereira

To override this classification, remove the review/tier-2 label and apply a different review/tier-* label. Manual overrides are preserved on subsequent pushes.

[github-actions]

E2E Test Results

✅ All tests passed • 197 passed • 3 skipped • 1289s

Status	Count
✅ Passed	197
❌ Failed	0
⚠️ Flaky	5
⏭️ Skipped	3

Tests ran across 4 shards in parallel.

View full report →

[greptile-apps]

Greptile Summary

This PR adds ClickHouse safety guardrails (max_execution_time: 30, max_result_rows: 100000, readonly: 1) and a matching requestTimeout to all MCP query-tool executions, preventing runaway queries, serialization OOM, and DDL/DML injection from agent-supplied SQL.

• helpers.ts: A single MCP_CLICKHOUSE_SETTINGS constant is applied to both the builder-config and raw-SQL code paths inside runConfigTile, plus a requestTimeout (32 s) on each ClickhouseClient construction; new errorHint branches cover RESULT_IS_TOO_LARGE and TOO_MANY_ROWS_OR_BYTES.
• queryTool.test.ts: End-to-end integration tests verify readonly rejection for CREATE/INSERT/DROP and that getSetting() queries confirm all three safety settings are propagated through the full clickstack_sql MCP path.
• query.test.ts: Unit tests cover the two new errorHint patterns.

Confidence Score: 5/5

Safe to merge — the safety settings are correctly applied to both execution paths and verified by end-to-end integration tests.

The change is well-scoped: a single constant governs both code paths, processClickhouseSettings confirms the external settings take precedence over defaults, and the new propagation tests cover the full MCP round-trip. The only nit is max_result_rows being typed as a string literal rather than a number, which has no runtime impact.

No files require special attention.

Important Files Changed

Filename	Overview
packages/api/src/mcp/tools/query/helpers.ts	Adds MCP_CLICKHOUSE_SETTINGS constant and MCP_REQUEST_TIMEOUT, applies them to both builder-config and raw-SQL code paths, and adds RESULT_IS_TOO_LARGE / TOO_MANY_ROWS_OR_BYTES error hints. Minor: max_result_rows is typed as a string literal while the other two settings are numbers.
packages/api/src/mcp/tests/queryTool.test.ts	Adds end-to-end integration tests for readonly enforcement (CREATE/INSERT/DROP rejected, SELECT passes) and settings-propagation tests for all three MCP_CLICKHOUSE_SETTINGS values via getSetting() queries through the full clickstack_sql path.
packages/api/src/mcp/tests/query.test.ts	Adds unit tests for the two new errorHint patterns (RESULT_IS_TOO_LARGE and TOO_MANY_ROWS_OR_BYTES); straightforward additions.
.changeset/nasty-crews-shop.md	Patch-level changeset entry for the MCP safety-settings fix; description is accurate.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[MCP Tool Call\nclickstack_sql / clickstack_timeseries / etc.] --> B[runConfigTile]
    B --> C{Builder or Raw SQL?}

    C -- Builder --> D[new ClickhouseClient\nrequestTimeout: 32s]
    C -- Raw SQL --> E[new ClickhouseClient\nrequestTimeout: 32s]

    D --> F[queryChartConfig\nopts: clickhouse_settings]
    E --> G[queryChartConfig\nopts: clickhouse_settings]

    F --> H[MCP_CLICKHOUSE_SETTINGS\nmax_execution_time: 30\nmax_result_rows: 100000\nreadonly: 1]
    G --> H

    H --> I[processClickhouseSettings\nmerge with defaults]
    I --> J[ClickHouse HTTP query]

    J -- success --> K[formatQueryResult]
    J -- error --> L[clickHouseErrorResult]
    L --> M{errorHint match?}
    M -- DateTime64 / AS syntax\nV8 string / RESULT_IS_TOO_LARGE --> N[Append actionable HINT]
    M -- no match --> O[raw error message]

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_{Reviews (2): Last reviewed commit: "fix(mcp): add RESULT_IS_TOO_LARGE errorH..." | Re-trigger Greptile}

[brandon-pereira]

Addressed both Greptile findings:

Issue 1 (max_execution_time test bypasses MCP path): Added getSetting() integration tests that go through the full clickstack_sql → runConfigTile → queryChartConfig → ClickHouse path and verify the actual setting values (max_execution_time=30, max_result_rows=100000, readonly=1) are applied to the running query. The direct ClickhouseClient test is kept alongside as a behavioral test (proves ClickHouse actually kills slow queries).

Issue 2 (Missing errorHint for RESULT_IS_TOO_LARGE): Added hint matching both RESULT_IS_TOO_LARGE and TOO_MANY_ROWS_OR_BYTES with actionable guidance to add LIMIT / narrow time range / add filters.