Reduce MutableProxy per-element overhead and cache per-field proxies

[Alek99]

Linear: ENG-10094

Description

• MutableProxy._wrap_recursive walked 5 stack frames (_is_called_from_dataclasses_internal) for every element retrieved through a proxy, before the cheap is_mutable_type check that usually decides nothing needs wrapping. The checks are reordered so immutable elements (the common case: ints, strings in a proxied list) skip the frame walk entirely. The dataclasses-internal check still runs for mutable values, preserving dataclasses.asdict/astuple behavior.
• BaseState._get_attribute constructed a fresh MutableProxy on every read of a mutable state var. The proxy is now cached per instance and field name, invalidated by identity when the underlying value is reassigned. The cache is excluded from pickling (__getstate__), and copy/deepcopy already round-trip through __getstate__, so copies never share or carry proxies.

One deliberate nuance: when _wrap_recursive receives an already-proxied value and is called from dataclasses internals, it now returns the unwrapped value (previously the still-wrapped proxy), matching the documented intent of that path.

Benchmarks (GitHub Actions runner, run, 2 passes each)

Case	main	this PR	speedup
iterate 1000-int list via proxy	0.977 / 0.973 ms	0.219 / 0.214 ms	~4.5x
index 1000 elements via proxy	1.204 / 1.171 ms	0.396 / 0.381 ms	~3.0x
read mutable var attribute	2.82 / 2.87 us	1.17 / 1.15 us	~2.4x

cProfile (20 iterations + 2000 attr reads): _is_called_from_dataclasses_internal (20,000 calls, 0.028s cumulative) disappears from the profile; total function calls drop from 168k to 72k.

Type of change

• Bug fix (non-breaking change which fixes an issue)

Changes To Core Features:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your core changes, as applicable?
  • tests/units/istate/test_proxy.py: proxy reused across reads and invalidated on reassignment; cache never serialized (pickle round-trip rebinds proxies to the restored state); iteration yields plain immutables while mutable elements stay wrapped.
• Have you successfully ran tests with your changes locally?

🤖 Generated with Claude Code

https://claude.ai/code/session_01G8cXh3TUbNtbjm2ERqE62X

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Generated by Claude Code

[linear-code]

ENG-10094

[greptile-apps]

Greptile Summary

This PR reduces overhead in mutable state proxy handling. The main changes are:

• Skips dataclasses frame checks for immutable proxied values.
• Caches mutable state proxies per instance and field.
• Clears cached proxies when state fields are reassigned.
• Excludes proxy caches from serialized state.
• Reserves the internal proxy cache field name.

Confidence Score: 5/5

This looks safe to merge.

• No blocking issues found in the changed code.

Important Files Changed

Filename	Overview
reflex/istate/proxy.py	Reorders recursive proxy wrapping so immutable values return before the dataclasses frame check.
reflex/state.py	Adds a per-field mutable proxy cache with reassignment invalidation and serialization cleanup.
packages/reflex-base/src/reflex_base/utils/types.py	Adds _mutable_proxy_cache to the reserved backend variable names.
tests/units/istate/test_proxy.py	Adds tests for proxy cache reuse, cache serialization, and immutable iteration.
tests/units/test_state.py	Updates the state proxy identity expectation for cached mutable proxies.

_{Reviews (4): Last reviewed commit: "Declare _mutable_proxy_cache as a reserv..." | Re-trigger Greptile}

[codspeed-hq]

Merging this PR will improve performance by ×3.2

⚡ 2 improved benchmarks
✅ 24 untouched benchmarks
⏩ 8 skipped benchmarks¹

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
⚡	test_var_access[mutable_list]	71.6 ms	19.1 ms	×3.8
⚡	test_var_access[mutable_dict]	88.6 ms	32.5 ms	×2.7

Tip

Curious why this is faster? Comment @codspeedbot explain why this is faster on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing claude/reflex-perf-optimizations-01l7a3-eng-10094 (d6ab47c) with main (48f9e6c)}

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. ↩

[chatgpt-codex-connector]

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[masenf]

similar to the last PR, unclear on why these cache flags are being directly added into the __dict__ and using object.__setattr__ and the like instead of just defining them as reserved fields on the state.

if we define them as real fields on the state, then users will get an exception if they try to reuse the name, instead of internal tracking machinery just getting broken or corrupting user data.

[Alek99]

Good call — converted in d6ab47c: _mutable_proxy_cache is now a declared field(default_factory=dict, is_var=False) like _backend_vars/_was_touched, added to RESERVED_BACKEND_VAR_NAMES so a user var with that name can't silently collide. It stays out of pickles (__getstate__ pop) and is recreated empty in __setstate__. I'll apply the same treatment to the propagation-frontier fields in #6743.

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