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hook-local-sts-into-mssql

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Wire a locally-published SQL Tools Service (STS) build into the vscode-mssql by setting MSSQL_SQLTOOLSSERVICE in launch.json. Use when: testing local STS changes in vscode-mssql, hooking up locally-built STS to MSSQL, debugging STS from VS Code, "use my local STS in MSSQL", "point MSSQL at local STS", "hook up STS to MSSQL", "set MSSQL_SQLTOOLSSERVICE". Assumes STS has already been local-published (see the `local-publish-sts` skill).

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Source SKILL.md: https://github.com/microsoft/sqltoolsservice/blob/HEAD/.github/skills/hook-local-sts-into-mssql/SKILL.md

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Hook local STS into vscode-mssql

Update vscode-mssql's launch.json to point its Extension Development Host at a locally-published STS via the MSSQL_SQLTOOLSSERVICE environment variable. After this, launching a debug session of the MSSQL extension uses your local STS instead of the bundled one.

When to use

  • The user just built STS (or asks you to) and wants to test it in the MSSQL extension.
  • The user says "use my local STS in MSSQL", "point MSSQL at local STS", "hook up local STS", "set MSSQL_SQLTOOLSSERVICE", or "set the STS env var".
  • The MSSQL repo may or may not be in the same workspace as STS; this skill handles both cases.

Prerequisite

The STS publish folder must exist. If it doesn't, run the local-publish-sts skill first (or instruct the user to). The path you will need is:

<sts-repo-root>/artifacts/publish/Microsoft.SqlTools.ServiceLayer/default/net10.0

or similar (e.g. if .NET has been updated)

Procedure

Step 1 — Locate the STS publish folder

If the current working directory is an STS clone, derive the path from there. Otherwise ask the user for the STS repo root via ask_user.

Confirm the folder exists and contains MicrosoftSqlToolsServiceLayer.exe (Windows) or MicrosoftSqlToolsServiceLayer (Linux/macOS). If missing, stop and tell the user they need to local-publish first (and offer to run it for them).

Step 2 — Locate the vscode-mssql repo

The agent may not have direct access to the MSSQL repo. Check, in this order:

  1. Sibling directory of the STS repo (<sts-repo-parent>/vscode-mssql/). This is the most common layout.
  2. Open editor workspace folders — check any .code-workspace file or ${workspaceFolder} references that point at a vscode-mssql clone.
  3. Common defaults: ~/Source/vscode-mssql/, ~/source/repos/vscode-mssql/, ~/code/vscode-mssql/, ~/repos/vscode-mssql/.

The folder name mssql may also be used for vscode-mssql.

If none match, use ask_user to prompt for the absolute path to their vscode-mssql repo root. Do not guess silently.

Validate it's a real vscode-mssql clone before continuing; the repo should contain both extensions/mssql/package.json and .vscode/launch.json.

Step 3 — Update both launch.json files

vscode-mssql has two relevant launch.json files. Update both so the environment variable is set whether the user opens the repo root or the extensions/mssql folder as their workspace:

Path (relative to vscode-mssql root)Active when…Configurations
.vscode/launch.jsonRepo root is the workspace folder"Run All Extensions"
extensions/mssql/.vscode/launch.jsonextensions/mssql is the workspace folder"Launch Extension", "Launch Extension (With Other Extensions Disabled)"

For every launch configuration in both files, set MSSQL_SQLTOOLSSERVICE inside the env block. The shipped template typically has a commented-out placeholder:

// "MSSQL_SQLTOOLSSERVICE": "<Path to STS>"

Replace that line (uncommented) with the absolute STS publish path. If no placeholder exists, add the entry to the existing env object.

"env": {
    "MSSQL_SQLTOOLSSERVICE": "c:\\path\\to\\sqltoolsservice\\artifacts\\publish\\Microsoft.SqlTools.ServiceLayer\\default\\net10.0"
    // Other env entries (e.g. MSSQL_SQLTOOLS_MCP); preserve any that are present
}

Path formatting rules:

  • Use an absolute path. ${workspaceFolder}-relative paths break whenever the STS repo lives outside the launched workspace (which is always when the two repos are sibling directories).
  • On Windows, JSON requires either \\ or / as the path separator (single \ is an invalid escape). Either works for VS Code.
  • Preserve any other entries already in the env object (e.g. MSSQL_SQLTOOLS_MCP, telemetry flags); only touch MSSQL_SQLTOOLSSERVICE.

Reference for the env var: https://github.com/microsoft/vscode-mssql/blob/main/DEVELOPMENT.md#using-mssql_sqltoolsservice-environment-variable

Step 4 — Verify and report

  1. Resolve the exact path you wrote and confirm it exists: 
    Test-Path "<the configured absolute path>/MicrosoftSqlToolsServiceLayer[.exe for Windows]"
  2. Re-read both launch.json files and confirm MSSQL_SQLTOOLSSERVICE shows up with the right value in every config's env block.
  3. Tell the user:
    • ✅ Both launch.json files updated with MSSQL_SQLTOOLSSERVICE.
    • Which configurations now use the local STS.
    • That they need to re-run the local-publish-sts skill after each STS code change and stop any running EDH first to release file locks before re-publishing.

Common pitfalls

  • Only updating one launch.json. The repo-root file and the extensions/mssql/.vscode/ file each ship with different launch configurations. If you only update one, F5 will silently fall back to the bundled STS when the user opens the "wrong" workspace folder.
  • Forgetting to escape backslashes in the JSON string. "c:\Users\..." is invalid JSON.
  • Pointing at …/Debug/net10.0/ instead of …/publish/…/default/net10.0/. The bin/Debug output isn't a published runnable; only the artifacts/publish/Microsoft.SqlTools.ServiceLayer/default/net10.0 folder is.
  • Pointing at the wrong STS clone's artifact output stale path if the user has multiple STS clones. The user means to use the clone that this skill resides in.