`tsp install` doesn't respect `TYPESPEC_NPM_REGISTRY` variable

[catalinaperalta]

The following PR attempted to set the TYPESPEC_NPM_REGISTRY env var and it was not respected: #11674

Likewise offline attempts were unsuccessful.

[github-actions]

🎯 Issue Triage

tsp install does not respect the TYPESPEC_NPM_REGISTRY environment variable when resolving packages, as confirmed by a failed PR attempt (#11674) and offline testing.

Category: Bug
Area: compiler:core

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

🔍 Analysis

• The TYPESPEC_NPM_REGISTRY env var is expected to redirect npm registry lookups (e.g., for air-gapped/offline environments or private registries).
• tsp install appears to ignore this variable and always use the default npm registry.
• PR Set TYPESPEC_NPM_REGISTRY to devOps feed #11674 attempted to use this env var in CI but it had no effect.
• The root cause is likely in the tsp install command implementation in packages/compiler, where the registry env var is either not read or not passed to the underlying npm/install invocation.

📝 Suggested next steps

• Locate where tsp install invokes npm/package installation in packages/compiler
• Check whether TYPESPEC_NPM_REGISTRY is read and forwarded to the npm subprocess
• Add or fix the env var handling so the registry is respected
• Add a test or CI verification for this behavior

Generated by Agentic Triage