Short recommendation
Fix the monorepo’s TypeScript/package metadata and narrow what the editor/Copilot can see. Most hallucinated imports happen because the model (or your language server) can’t reliably resolve package names, so Copilot invents likely-but-nonexistent module paths. The reliable fix is to make resolution unambiguous; as a quick mitigation, reduce Copilot’s workspace scope or turn off inline suggestions.

Why this works (decision criteria)
- If you can invest developer time (medium/large teams, long-lived repo): fix tsconfig, package.json exports, and workspace references. This removes ambiguity at the source and stops most bad suggestions.
- If you need a short-term or low-effort fix (small team, tight deadline): limit Copilot’s visibility (per-workspace disable / turn off inline suggestions) or rely on TypeScript’s built-in auto-imports instead.
- If output quality matters (production code): prefer fixing project layout over heuristics or prompt hacks — it’s more robust.

Practical checklist (do these in order)
1) Make packages resolvable
- Ensure every package in packages/* has a package.json with a unique name, and correct "main"/"types"/"exports" fields. This lets tooling prefer real packages.
- Add a root tsconfig.json that uses "references" and set "composite": true for package tsconfigs so tsc/tsserver can resolve cross-package imports.
- Use tsconfig "baseUrl" and "paths" (or proper package names) so imports map to actual folders (example: "@org/pkg/*": ["packages/pkg/src/*"]).
2) Build/type-check the workspace
- Run tsc --build (or your monorepo build command) so .d.ts and dist files exist. The language server will then prefer real exports.
3) Reduce noise in editor/Copilot context
- Exclude artifacts and irrelevant folders from the editor (VS Code: files.exclude and search.exclude for dist, build, node_modules across packages).
- Add those to .gitignore so they aren’t used as context by tooling that reads the repo.
- If hallucinations persist, disable Copilot inline suggestions in the workspace or disable the Copilot extension per workspace and use it only from the Copilot pane/chat. (This forces you to use TypeScript auto-imports or manual imports.)
4) Prefer TypeScript auto-imports for correctness
- Use the editor’s Quick Fix (e.g., Ctrl+. in VS Code) to import a symbol — the TypeScript language service will suggest only resolvable imports.
5) Small prompt/usage tips (if you keep Copilot enabled)
- Seed the file with an import you want or a clear comment: e.g., /* prefer imports from @org/* */ — not guaranteed but can bias completions.
- If Copilot suggests an import, hover it (or attempt to resolve) before accepting; if it fails quick-fix will show no resolution.

Best-for / Avoid-if
- Best-for: teams that can adjust package.json/tsconfig and add proper exports — this yields the best long-term result.
- Avoid if: you need a very fast temporary workaround — instead disable Copilot inline and rely on the language server.

If you want, I can give a minimal example root tsconfig.json and a package.json exports snippet tailored to your monorepo layout.

Compare GitHub Copilot and Cursor