New visualizations, accuracy improvements, and bug fixes

What's Changed

Headlines

• Adds call graphs ("flame graphs") spanning from Python to native code, organized by % of time
• Timeline view of call graphs ("flame chart"), including GIL, I/O, and GC activity
• Flame graph for memory allocations, attributing memory to call stacks
• Improved memory attribution (now tracked per-thread)
• Adds proper support for free-threaded Python

New feature work

• True free-threaded Python support: full memory + CPU profiling by @emeryberger in #1026
• Bucket native-thread allocations under (#857) by @emeryberger in #1031
• Native (C/C++) stack collection via signal-handler unwinding by @emeryberger in #1034
• Stitched Python+native stacks (combined_stacks) by @emeryberger in #1035
• GUI: combined_stacks viewer (top-N stitched Python+native stacks) by @emeryberger in #1037
• Timeline view for stitched Python+native stacks by @emeryberger in #1040
• Memory flame chart + sync per-sample stack capture by @emeryberger in #1042
• Shrink stack+timeline RAM, harden profiler self-exclusion by @emeryberger in #1043
• Shrink combined_stacks JSON and enforce schema validation by @emeryberger in #1044
• Timeline + memory-stacks polish: axes, gridlines, source-line tooltips by @emeryberger in #1045
• Minify the GUI bundle (-56% on disk) by @emeryberger in #1046
• GUI improvements: resizable charts, C++ demangling, stack filtering by @emeryberger in #1047
• Add per-thread native stack sampling for worker threads by @emeryberger in #1048
• Make --stacks the default; add --no-stacks opt-out by @emeryberger in #1050
• Drop C-side smear from per-line memory attribution and the flame view by @emeryberger in #1051

Bug fixes

• Fix root cause of resource tracker death in child processes (#1017) by @emeryberger in #1024
• Fix SIGSEGV on free-threaded Python with memory profiling by @emeryberger in #1025
• Fix memory profiling regressions by @emeryberger in #1027
• Fix CLI line number truncation for lines > 999 by @emeryberger in #1028
• Fix issue #1022: pytest-xdist + --profile-all on Linux dropped user samples by @emeryberger in #1055
• Clamp core_utilization to [0, 1] (fixes #1032) by @emeryberger in #1033

Full Changelog: v2.2.1...v2.3.0

Scalene v2.2.1

Scalene v2.2.1

Bug Fixes

• sys.monitoring tool ID conflict with PyTorch (#1015, #1019): Fixed SIGSEGV crash when using Scalene with PyTorch Lightning on Python 3.12+. When PROFILER_ID is already claimed by another tool, Scalene now falls back to alternative tool IDs (3 or 4), or gracefully uses the legacy PyEval_SetTrace tracer.

• TensorFlow 2.21+ compatibility (#1018): Fixed compatibility with TensorFlow 2.21+ where trace.enabled changed from a callable to a bool. Scalene now applies a compatibility fix at profiler start time.

• Multiprocessing resource tracker (#1017): Fixed BrokenPipeError on NixOS with Python 3.13/3.14 when the resource tracker subprocess dies during semaphore creation. Scalene now falls back from spawn/forkserver to fork context.

• Subprocess profiling (#1013): Fixed profiling failing when Python interpreter flags (like -B or -u) precede -c or -m in subprocess invocations.

• Windows timer thread shutdown (#1012): Fixed fatal gilstate_tss_set error on Windows when the timer thread shuts down.

• Windows --on/--off support (#1010): Added support for --on and --off flags on Windows using Named Events.

• __future__ flags in exec/eval (#1008): Fixed __future__ compiler flags not being propagated in exec/eval/compile replacements.

• Windows multiprocessing (#1005, #998): Fixed spawn-mode multiprocessing Pool support on Windows, including pickle corruption and memoryview cleanup issues.

New Features

• Async-aware profiling (#1006): Added async-aware profiling support using sys.monitoring on Python 3.12+.

• C23 allocator support (#1011): Added support for C23 free_sized and free_aligned_sized functions in SampleHeap.

Other Changes

• Improved shell script portability for NixOS/Guix using #!/usr/bin/env bash
• Code formatting updates via Black

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Full Changelog: v2.1.4...v2.2.1

Maintenance release with bugfixes and performance improvements

What's Changed

• Refined attribution approach for C vs. Python by @emeryberger in #1001
• Fix Python 3.14 compatibility for eval()/exec() keyword arguments by @emeryberger in #1002
• Fix memory explosion and extreme slowness during profiling by @emeryberger in #1004

Full Changelog: v2.1.3...v2.1.4

Improved attribution, off-line mode, and fix for Jupyter

What's Changed

• Fix loop backward-jump sampling bias with even redistribution by @emeryberger in #995
• Fix Google Analytics loading delay in offline/standalone mode by @Copilot in #996
• Fixed Jupyter magics. by @emeryberger in #997

Full Changelog: v2.1.2...v2.1.3

v2.1.2

What's Changed

Bug Fixes

• Fix Windows CPU profiling extreme slowness and memory explosion (#992): The v2.1 Windows timer loop hardcoded a 1ms sampling interval regardless of the configured rate (default 10ms), generating ~10x more samples than intended and reducing sys.setswitchinterval to 1ms causing excessive GIL contention. Now uses the actual configured sampling rate.

Improvements

• Bound memory footprint samples with reservoir sampling (#993): Replace unbounded list accumulation of memory footprint samples with sorted_reservoir (Vitter reservoir sampling), capping memory at O(k) instead of O(n) where n is the number of malloc/free events. Eliminates unbounded memory growth during long profiling runs.

Full Changelog: v2.1.1...v2.1.2

Improves JAX and TensorFlow support; fixes Windows issue

What's Changed

• Add library profiler infrastructure for JAX and TensorFlow by @emeryberger in #990
• Removes stray debug statements on Windows.

Full Changelog: v2.1.0...v2.1.1

Numerous updates and bug fixes

UI, Frontend & Visualization

• Convert scalene-gui JavaScript to TypeScript by @emeryberger in #970
• Add Google Gemini provider, environment variable support, and UI modernization by @emeryberger in #973
• Vendor assets locally for offline HTML viewer support by @emeryberger in #983
• Add per-file display mode dropdown for profile filtering (fixes #813) by @emeryberger in #989

LLM / API Provider Support

• Add support for OpenAI-compatible API servers and Anthropic (fixes #918) by @emeryberger in #971
• Add Google Gemini provider, environment variable support, and UI modernization by @emeryberger in #973

CPU & Core Profiling Engine

• Optimize CPU profiling instrumentation by @emeryberger in #988
• Fix crash when frame.f_lineno is None in Python 3.11+ by @emeryberger in #976

Multiprocessing, Exec, and Runtime Compatibility

• Fix multiprocessing spawn mode support (#873) by @emeryberger in #984
• Fix multiprocessing spawn mode sys.argv handling (#846) by @emeryberger in #986
• Add profiling support for exec'd code (fixes #824) by @emeryberger in #987
• Fix signal conflict crash with PyTorch Lightning and similar libraries by @emeryberger in #977

PyTorch & JIT Integration

• Add PyTorch JIT profiling support (fixes #908) by @emeryberger in #972

GPU & Apple Silicon

• Add per-process MPS GPU profiling for Apple Silicon by @emeryberger in #974

Windows Support & Reliability

• Improve Windows memory profiling error messages and documentation by @emeryberger in #978
• Fix Windows CPU profiling not collecting samples by @emeryberger in #980

Notebook & Editor Integration

• Fix Jupyter notebook display in VSCode (fixes #951) by @emeryberger in #969

v2.0.1

Trigger re-build to produce libscalene.dll.

Major new release: Windows memory profiling support, improved CLI, and performance optimizations

What's Changed

• Fix for pickling support (multiprocessing issue on Windows) by @emeryberger in #954
• CI update to 3.14 by @emeryberger in #955
• Restore 3.8 support by @emeryberger in #958
• Fixed formatting of CLI help. by @emeryberger in #962
• Overhauled CLI. by @emeryberger in #963
• Windows memory profiling by @emeryberger in #965
• Initial sys.monitoring approach for memory profiling. by @emeryberger in #966
• Refactor scalene_profiler.py into modular components by @emeryberger in #967

Full Changelog: v1.5.55...v2.0.0

Maintenance release for Windows

What's Changed

• Fix signal timer resetting by @sternj in #946
• Cleanup; fixes #947. by @emeryberger in #948
• Removed unused methods and variables. by @emeryberger in #949
• Removed cruft, privatized more methods. by @emeryberger in #950

Full Changelog: v1.5.54...v1.5.55