fix: drop unneeded turbopack env

[benedikt-bartscher]

No description provided.

[codspeed-hq]

Merging this PR will not alter performance

✅ 26 untouched benchmarks
⏩ 8 skipped benchmarks¹

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_{Comparing benedikt-bartscher:drop-unused-turbopack (2158b88) with main (8ea5bdc)}

Footnotes

1. 8 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[greptile-apps]

Greptile Summary

This PR removes the REFLEX_USE_TURBOPACK environment variable, which has been a no-op since Reflex migrated from Next.js to React Router and Vite in 0.8. A grep across the repository confirms no other file references this variable, so the removal is safe.

• environment.py: Drops the REFLEX_USE_TURBOPACK: EnvVar[bool] field from EnvironmentVariables; the three-line deletion is the only code change.
• news/6803.misc.md: Adds a changelog entry documenting the removal and the rationale.

Confidence Score: 5/5

This is a safe cleanup — removing a dead env var with no callers anywhere in the repo.

The removed field has zero references in the codebase outside the deletion itself, and the changelog correctly documents the context. There is no risk of breakage.

Files Needing Attention: No files require special attention.

Important Files Changed

Filename	Overview
packages/reflex-base/src/reflex_base/environment.py	Removes the unused REFLEX_USE_TURBOPACK env var; no other file in the repo references it.
packages/reflex-base/news/6803.misc.md	Changelog entry explaining why the env var is removed.

_{Reviews (2): Last reviewed commit: "chore: add news fragment for turbopack e..." | Re-trigger Greptile}