perf: switch YAML loading to CSafeLoader (11.1x speedup)#2150
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Trecek merged 4 commits intoMay 7, 2026
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Replace yaml.safe_load() with yaml.load(Loader=_Loader) where _Loader is CSafeLoader (LibYAML C backend) with automatic fallback to SafeLoader when LibYAML is not compiled in. All YAML loading flows through load_yaml() in core/io.py, so the change propagates to all consumers. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
… import The CSafeLoader import block added 5 lines to core/io.py, shifting write_versioned_json's atomic_write call from line 118 to line 123. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
The except ImportError branch was using bare `pass`, leaving _Loader unbound and causing NameError on systems without LibYAML. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
…rized test Merge test_load_yaml_uses_c_loader_when_available and test_load_yaml_path_uses_c_loader into a single parametrized test (str-input vs path-input). Add assert for unexpected kwargs in the spy function. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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## Summary
Replace `yaml.safe_load()` calls in
`src/autoskillit/core/io.py:load_yaml()` with `yaml.load(source,
Loader=CSafeLoader)`, using LibYAML's C backend for an 11.1x speedup.
All YAML loading in the codebase flows through this single function —
recipe validation, config loading, experiment type registries, migration
loading, and CLI validation all benefit from the improvement.
## Requirements
### Problem
`load_yaml()` in `src/autoskillit/core/io.py:181` uses
`yaml.safe_load()`, which defaults to the pure-Python `SafeLoader` even
when LibYAML's C backend is available. LibYAML IS compiled in (PyYAML
6.0.3, `__with_libyaml__ = True`), but `yaml.safe_load()` does not use
it automatically.
### Measured Impact
Benchmark on 5 real recipe files, 100 iterations:
```
SafeLoader: 8.557s
CSafeLoader: 0.770s
Speedup: 11.1x
```
All YAML loading in the codebase flows through this single function.
Recipe validation, config loading, experiment type/methodology tradition
loading, migration loading — all benefit.
### Fix
In `src/autoskillit/core/io.py`, change `load_yaml()` to use
`CSafeLoader` with fallback:
```python
try:
from yaml import CSafeLoader as _Loader
except ImportError:
from yaml import SafeLoader as _Loader
# Then in load_yaml():
data = yaml.load(text, Loader=_Loader)
```
### Risk
Low. CSafeLoader has minor behavioral differences from SafeLoader
(stricter timestamp handling, different inf/nan behavior), but these are
unlikely to affect recipe/config YAML. Run the full test suite to
confirm.
### Files
- `src/autoskillit/core/io.py` — single fix point
## Conflict Resolution Decisions
The following files had merge conflicts that were automatically
resolved.
## Changed Files
### Modified (●):
- `src/autoskillit/core/io.py`
- `tests/core/test_io.py`
- `tests/infra/test_schema_version_convention.py`
Closes #2133
## Implementation Plan
Plan file:
`/home/talon/projects/autoskillit-runs/impl-20260507-000427-400052/.autoskillit/temp/make-plan/perf_switch_yaml_loading_to_csafeloader_plan_2026-05-07_000427.md`
🤖 Generated with [Claude Code](https://claude.com/claude-code) via
AutoSkillit
<!-- autoskillit:pipeline-signature
steps=prepare_pr,run_arch_lenses,compose_pr,annotate_pr_diff,review_pr
-->
## Token Usage Summary
| Step | Model | count | uncached | output | cache_read | peak_ctx |
turns | cache_write | time |
|------|-------|-------|----------|--------|------------|----------|-------|-------------|------|
| plan | claude-opus-4-6 | 1 | 69 | 5.8k | 506.1k | 45.1k | 40 | 35.1k |
4m 4s |
| verify | claude-sonnet-4-6 | 1 | 35 | 6.3k | 276.6k | 49.7k | 53 |
36.6k | 3m 43s |
| implement* | MiniMax-M2.7-highspeed | 1 | 173.7k | 3.6k | 450.1k |
42.9k | 35 | 53.7k | 2m 4s |
| fix | claude-opus-4-6 | 1 | 47 | 4.2k | 714.1k | 47.1k | 33 | 34.2k |
10m 5s |
| prepare_pr* | MiniMax-M2.7-highspeed | 1 | 48.4k | 2.9k | 175.7k |
29.8k | 19 | 15.1k | 1m 11s |
| compose_pr* | MiniMax-M2.7-highspeed | 1 | 47.2k | 1.5k | 205.5k |
29.8k | 15 | 15.0k | 42s |
| **Total** | | | 269.5k | 24.3k | 2.3M | 49.7k | | 189.8k | 21m 51s |
\* *Step used a non-Anthropic provider; caching behavior may differ.*
## Token Efficiency
| Step | LoC Changed | cache_read/LoC | cache_write/LoC | output/LoC |
|------|-------------|----------------|-----------------|------------|
| plan | 0 | — | — | — |
| verify | 0 | — | — | — |
| implement | 58 | 7759.8 | 925.6 | 62.6 |
| fix | 2 | 357047.5 | 17119.5 | 2124.5 |
| prepare_pr | 0 | — | — | — |
| compose_pr | 0 | — | — | — |
| **Total** | **60** | 38801.3 | 3162.7 | 404.8 |
## Model Usage Breakdown
| Model | steps | uncached | output | cache_read | cache_write | time |
|-------|-------|----------|--------|------------|-------------|------|
| claude-opus-4-6 | 2 | 116 | 10.0k | 1.2M | 69.3k | 14m 9s |
| claude-sonnet-4-6 | 1 | 35 | 6.3k | 276.6k | 36.6k | 3m 43s |
| MiniMax-M2.7-highspeed | 3 | 269.3k | 8.0k | 831.3k | 83.8k | 3m 58s |
---------
Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>
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Summary
Replace
yaml.safe_load()calls insrc/autoskillit/core/io.py:load_yaml()withyaml.load(source, Loader=CSafeLoader), using LibYAML's C backend for an 11.1x speedup. All YAML loading in the codebase flows through this single function — recipe validation, config loading, experiment type registries, migration loading, and CLI validation all benefit from the improvement.Requirements
Problem
load_yaml()insrc/autoskillit/core/io.py:181usesyaml.safe_load(), which defaults to the pure-PythonSafeLoadereven when LibYAML's C backend is available. LibYAML IS compiled in (PyYAML 6.0.3,__with_libyaml__ = True), butyaml.safe_load()does not use it automatically.Measured Impact
Benchmark on 5 real recipe files, 100 iterations:
All YAML loading in the codebase flows through this single function. Recipe validation, config loading, experiment type/methodology tradition loading, migration loading — all benefit.
Fix
In
src/autoskillit/core/io.py, changeload_yaml()to useCSafeLoaderwith fallback:Risk
Low. CSafeLoader has minor behavioral differences from SafeLoader (stricter timestamp handling, different inf/nan behavior), but these are unlikely to affect recipe/config YAML. Run the full test suite to confirm.
Files
src/autoskillit/core/io.py— single fix pointConflict Resolution Decisions
The following files had merge conflicts that were automatically resolved.
Changed Files
Modified (●):
src/autoskillit/core/io.pytests/core/test_io.pytests/infra/test_schema_version_convention.pyCloses #2133
Implementation Plan
Plan file:
/home/talon/projects/autoskillit-runs/impl-20260507-000427-400052/.autoskillit/temp/make-plan/perf_switch_yaml_loading_to_csafeloader_plan_2026-05-07_000427.md🤖 Generated with Claude Code via AutoSkillit
Token Usage Summary
* Step used a non-Anthropic provider; caching behavior may differ.
Token Efficiency
Model Usage Breakdown