Clarification on tsc --build's Incremental Caching in CI

[WillowRyu]

Summary

Hello Turborepo team,

We'd love a clarification on how Turborepo's remote cache interacts with incremental build artifacts like .tsbuildinfo during a cache miss in CI.

Our Setup:

• A pnpm monorepo with TypeScript Project References (tsc -b).
• Remote Caching is enabled.
• tsc tasks are configured with dependsOn: ["^build"] and "outputs": ["*.tsbuildinfo"].

Our Question:

Consider a CI run on a clean environment with the following conditions:
A shared library (@repo/utils) has changed.
An application (@repo/app) that depends on @repo/utils has not changed.

This scenario correctly results in a cache miss for the @repo/app tsc task.

Our key question is about what happens next. Our expectation is that before running the task, Turborepo restores the previous .tsbuildinfo file for @repo/app from the remote cache (e.g., from the last successful main branch build).
This would allow tsc -b to then perform a very fast, incremental check instead of a full one.

Can you confirm if this is the intended behavior? Or does a cache miss for a task always mean it must run from scratch, without any of its previous artifacts being restored?

Additionally, if the current behavior is that .tsbuildinfo is not restored on a cache miss, we would like to suggest a feature.
It would be incredibly powerful to have an option to flag certain outputs to always be restored from a relevant cache (like main's) before task execution, even on a cache miss.
We believe this would be a game-changer for fully leveraging incremental tools like tsc -b in CI.

Thanks for the great work and for any clarification you can provide!

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