feat: Add deferred hashing for task inputs

[anthonyshew]

Why

Some task inputs are not reliable when turbo starts. Generated code, generated CSS, API types, and other materialized files may be missing or stale until an upstream task runs, which can produce a cache key that does not represent the files the task actually consumes.

Deferred hashing gives power users a way to finalize a task hash after its dependencies complete.

Simple examples:

Hashes normal package inputs at startup, using defaults while excluding dist:

{
  "inputs": [
    { "mode": "startup", "withDefaults": true, "globs": ["!dist/**"] }
  ]
}

Waits for codegen, then hashes generated files before checking cache:

{
  "dependsOn": ["codegen"],
  "inputs": [
    { "mode": "startup", "withDefaults": true, "globs": ["!src/generated/**"] },
    { "mode": "jit", "globs": ["src/generated/**"] }
  ]
}

Hashes declared outputs from the selected codegen task after it runs, without also hashing generated files at startup:

{
  "dependsOn": ["codegen"],
  "inputs": [
    { "mode": "startup", "withDefaults": true, "globs": ["!src/generated/**"] },
    { "mode": "dependencyOutputs", "from": ["codegen"], "globs": ["src/generated/**"] }
  ]
}

What

Adds deferred hashing support through startup, jit, and dependencyOutputs input modes, including validation, hashing, dry-run summaries, schema/bindings, architecture docs, user-facing docs, and regression coverage.

How

Ton of test coverage added, and did a lot of manual testing.

[vercel]

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Project	Deployment	Actions	Updated (UTC)
examples-basic-web	Ready	Preview, Comment, Open in v0	Jun 23, 2026 5:32pm
examples-designsystem-docs	Ready	Preview, Comment, Open in v0	Jun 23, 2026 5:32pm
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examples-kitchensink-blog	Ready	Preview, Comment, Open in v0	Jun 23, 2026 5:32pm
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examples-svelte-web	Ready	Preview, Comment, Open in v0	Jun 23, 2026 5:32pm
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examples-vite-web	Ready	Preview, Comment, Open in v0	Jun 23, 2026 5:32pm
turbo-site	Ready	Preview, Comment, Open in v0	Jun 23, 2026 5:32pm