fix: add turbo start task with passThroughEnv for deployment env injection

[jingerpie]

Summary

• Adds a start task to the generated turbo.json with passThroughEnv: ["*"]
• Adds passThroughEnv to the TurboTask interface

Problem

Turborepo filters environment variables by default. When deploying with turbo run start --filter=server on Docker-based platforms (Dokploy, Railway, etc.), all server env vars are undefined at runtime because Turborepo doesn't forward them to the child process.

This causes immediate crashes with @t3-oss/env-core validation:

❌ Invalid environment variables: [
  { path: ["DATABASE_URL"], message: "Invalid input: expected string, received undefined" },
  { path: ["BETTER_AUTH_SECRET"], message: "Invalid input: expected string, received undefined" },
  ...
]

Fix

The start task with passThroughEnv: ["*"] tells Turborepo to forward all environment variables to the server process, which is the expected behavior for production deployments.

Test plan

• Verify generated turbo.json includes the start task with passThroughEnv
• Deploy a scaffolded project using turbo run start --filter=server and confirm env vars are available

Fixes #992

Summary by CodeRabbit

Release Notes

• Chores
  • Enhanced build task configuration to support environment variable forwarding.
  • Added a new start task to the build pipeline with proper dependency management, disabled caching, and persistent execution mode for reliable builds.

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 9124820a-7fdd-471b-be94-403b0866398f

📥 Commits

Reviewing files that changed from the base of the PR and between 4c715bb and 7aee94f.

📒 Files selected for processing (1)

• packages/template-generator/src/processors/turbo-generator.ts

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Walkthrough

Added an optional passThroughEnv property to the TurboTask interface and introduced a new start task in the base Turbo configuration. The start task depends on build, disables caching, marks as persistent, and forwards all environment variables to the subprocess.

Changes

Cohort / File(s)	Summary
Turbo Task Configuration packages/template-generator/src/processors/turbo-generator.ts	Extended TurboTask interface with optional passThroughEnv?: string[] field. Added new start task definition in getBaseTasks() with dependsOn: ["build"], cache: false, persistent: true, and passThroughEnv: ["*"] to forward environment variables.

Possibly related PRs

• feat(cli): programmatically generate turbo.json #798: Introduced the foundational TurboTask type definition and getBaseTasks() function that this PR now extends with the passThroughEnv property and start task.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: adding a turbo start task with passThroughEnv for deployment environment injection, which is the primary objective.
Linked Issues check	✅ Passed	The PR implements all coding requirements from issue #992: adds passThroughEnv to TurboTask interface, creates start task with dependsOn, cache, persistent, and passThroughEnv settings.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to the objectives: interface extension and start task addition. No extraneous modifications to unrelated code.

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