perf: cut dev-mode memory in the frontend and telemetry paths

[FarhanAliRaza]

Summary

Two dev-mode memory reductions, measured on a blank app.

• Frontend toolchain: set MIMALLOC_ARENA_EAGER_COMMIT=0 for the vite dev server and the reflex export build (exec.frontend_env()). Rolldown allocates through mimalloc, and with eager commit the arena it touches during dependency pre-bundling stays resident for the life of the dev server. A value already present in the environment wins.
• Telemetry: _send_event posts through urllib.request instead of httpx, so backend workers never import httpx on their first error. The packaging imports in telemetry.py are lazy.

Measurements

PSS over the whole reflex run tree, page loaded once in headless Chrome, 15 s settle, cold = no .web/node_modules/.vite.

	main	this PR
node, cold	~780 MB	~460 MB
node, warm	~415 MB	~340 MB
total, cold	~1118 MB	~788 MB
total, warm	~752 MB	~668 MB
worker, first error	+9 MB, 0.07 s (httpx import)	+1 MB, 0.01 s

Python-side worker layout is unchanged here; #7079 covers forking.

Test plan

• uv run pytest tests/units (8482 passed, 76.6% coverage)
• ruff, pyright, pre-commit clean
• reflex export --frontend-only builds with the new env
• dev server starts and serves with the env var set

https://claude.ai/code/session_015Gi5wTWZNBA61pVDdPLu8u

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-11T14:37:13.721950Z	616ff22	PR opened

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[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge, with no concrete correctness, security, or repository-rule violations identified.

Summary

• Applies a user-overridable mimalloc setting to development servers and production frontend builds.
• Replaces httpx telemetry delivery with the standard-library urllib client.
• Defers package-metadata imports until telemetry defaults are collected.
• Adds focused tests for environment precedence, request serialization, transport errors, and avoiding the httpx import.

_{Reviews (1) · Last reviewed commit: "perf: cut dev-mode memory in the fronten..."}

[cubic-dev-ai]

No issues found across 6 files

_{Re-trigger cubic}

[codspeed-hq]

Merging this PR will not alter performance

✅ 40 untouched benchmarks
⏩ 8 skipped benchmarks¹

---

_{Comparing FarhanAliRaza:farhan/dev-mode-memory (616ff22) with main (8b393b5)}

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. ↩