`tsp install` ignores user `.npmrc`

[mikeharder]

Repro Steps

1. create a user .npmrc pointing to an alternative package registry
2. run "tsp install"

Expected: Respects user .npmrc
Actual: Ignores user .npmrc, tries to fetch from npmjs.org

Also appears to ignore NPM_CONFIG_REGISTRY env var:

% export NPM_CONFIG_REGISTRY=...     

% npx tsp install --debug                                              
trace cli.args: CLI args: { _: [ 'install' ], debug: true, pretty: true, '$0': 'tsp' }
Internal compiler error!
File issue at https://github.com/microsoft/typespec

[TypeError: fetch failed] {
  [cause]: Error: read ENOTCONN
      at TLSWrap.onStreamRead (node:internal/stream_base_commons:216:20) {
    errno: -57,
    code: 'ENOTCONN',
    syscall: 'read'
  }
}

[github-actions]

🎯 Issue Triage

tsp install does not respect the user-level .npmrc file, causing it to always fetch packages from the default npmjs.org registry instead of any configured alternative registry.

Category: Bug
Area: compiler:core

⚠️ No reproduction provided. A minimal repro would help diagnose this issue.

🔍 Analysis

• tsp install invokes npm under the hood to install TypeSpec dependencies. The issue is that the npm invocation may be ignoring the user-level ~/.npmrc or project-level .npmrc that specifies an alternative registry.
• This affects users in corporate/private environments who must route npm traffic through an internal registry (e.g., Azure Artifacts, Verdaccio, Nexus).
• Root cause is likely that tsp install either uses a hardcoded registry URL, passes --registry explicitly, or spawns npm in a way that bypasses the standard .npmrc lookup.
• Affected component: packages/compiler — the tsp install CLI command implementation.

📝 Suggested next steps

• Locate the tsp install implementation in packages/compiler and check how npm is invoked
• Verify whether a --registry flag or environment variable is being hardcoded
• Ensure npm is invoked in a way that respects the user's .npmrc (e.g., do not override registry)
• Add a test or note that validates .npmrc registry configuration is honored

Generated by Agentic Triage