Support Pixi for Conda environments

[j178]

Closes #2204

[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 2026-09-01T03:25:37.234232Z	5da50e2	PR opened

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[codecov]

Codecov Report

❌ Patch coverage is 98.02956% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.10%. Comparing base (72f3e9a) to head (5da50e2).

Files with missing lines	Patch %	Lines
crates/prek/src/languages/conda.rs	98.02%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2667      +/-   ##
==========================================
+ Coverage   94.05%   94.10%   +0.04%     
==========================================
  Files         141      141              
  Lines       29866    30069     +203     
==========================================
+ Hits        28091    28296     +205     
+ Misses       1775     1773       -2     

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[Copilot]

🟡 Changes recommended

The documentation currently omits legacy PRE_COMMIT_USE_{MICROMAMBA,MAMBA} behavior that is still implemented as a compatibility fallback when PREK_CONDA_INSTALLER is unset.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Adds Pixi as a supported installer for language: conda hooks, with a new PREK_CONDA_INSTALLER selector and updated CI/tests to exercise Pixi-backed environments.

Changes:

• Introduces PREK_CONDA_INSTALLER with auto resolution order (pixi, micromamba, mamba, conda) and Pixi-based environment creation for conda hooks.
• Updates Conda execution/health logic to account for Pixi’s nested prefix location and adds regression tests for Pixi installs and reuse across installer changes.
• Updates documentation and CI workflow to reflect the new installer selection behavior and to install Pixi in relevant CI runs.

File summaries

File	Description
docs/reference/environment-variables.md	Documents the new PREK_CONDA_INSTALLER environment variable and updates related env-var listings.
docs/languages.md	Updates Conda language docs to describe auto-selection and Pixi behavior.
crates/prek/tests/languages/conda.rs	Adds integration tests covering Pixi installs and reuse behavior.
crates/prek/src/languages/conda.rs	Implements installer resolution and Pixi-based environment creation; updates health checks and execution env pathing.
crates/prek-consts/src/env_vars.rs	Adds the PREK_CONDA_INSTALLER constant.
.github/workflows/ci.yml	Installs Pixi in CI for conda jobs and switches CI env selection to PREK_CONDA_INSTALLER.

Review details

• Files reviewed: 6/6 changed files
• Comments generated: 1
• Review effort level: Lite

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[prek-ci-bot]

📦 Cargo Bloat Comparison

.text size change: +0.00% (12.8 MiB → 12.8 MiB)

Expand for cargo-bloat output

Head Branch Results

File  .text     Size             Crate Name
0.1%   2.5% 332.0KiB        aws_lc_sys aws_lc_0_44_0_aes_gcm_encrypt_avx512
0.1%   2.5% 332.0KiB        aws_lc_sys aws_lc_0_44_0_aes_gcm_decrypt_avx512
0.0%   0.7%  96.5KiB              prek <prek::cli::Command as clap_builder::derive::Subcommand>::augment_subcommands
0.0%   0.4%  50.1KiB              prek <<prek::config::hook::HookWire as serde_core::de::Deserialize>::deserialize::__Visitor as serde_core::de::Visitor>::visit_map::<&mut <serde_saphyr::de::deserializer::YamlDeserializer as serde_core::de::Deserializer>::deserialize_map::MA>
0.0%   0.4%  49.7KiB              prek prek::run::{closure#0}
0.0%   0.4%  48.7KiB annotate_snippets annotate_snippets::renderer::render::render
0.0%   0.3%  43.9KiB              prek <<prek::config::Config as serde_core::de::Deserialize>::deserialize::__Visitor as serde_core::de::Visitor>::visit_map::<&mut <serde_saphyr::de::deserializer::YamlDeserializer as serde_core::de::Deserializer>::deserialize_map::MA>
0.0%   0.3%  40.2KiB              prek <prek::cli::RunOptions as clap_builder::derive::Args>::augment_args
0.0%   0.3%  37.0KiB              prek prek::cli::run::run::run::{closure#0}
0.0%   0.2%  28.7KiB      serde_saphyr <granit_parser::scanner::Scanner<granit_parser::input::str::StrInput>>::fetch_more_tokens
0.0%   0.2%  28.2KiB      serde_saphyr <granit_parser::scanner::Scanner<granit_parser::input::str::StrInput>>::fetch_more_tokens
0.0%   0.2%  28.1KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  28.0KiB        aws_lc_sys aws_lc_0_44_0_edwards25519_scalarmuldouble_alt
0.0%   0.2%  27.5KiB        aws_lc_sys aws_lc_0_44_0_edwards25519_scalarmuldouble
0.0%   0.2%  27.3KiB              toml <toml::de::deserializer::value::ValueDeserializer as serde_core::de::Deserializer>::deserialize_any::<<prek::config::hook::HookWire as serde_core::de::Deserialize>::deserialize::__Visitor>
0.0%   0.2%  27.1KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  27.0KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  26.9KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  26.9KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  26.9KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
4.2%  87.0%  11.1MiB                   And 20379 smaller methods. Use -n N to show more.
4.8% 100.0%  12.8MiB                   .text section size, the file size is 263.5MiB

Base Branch Results

File  .text     Size             Crate Name
0.1%   2.5% 332.0KiB        aws_lc_sys aws_lc_0_44_0_aes_gcm_encrypt_avx512
0.1%   2.5% 332.0KiB        aws_lc_sys aws_lc_0_44_0_aes_gcm_decrypt_avx512
0.0%   0.7%  96.5KiB              prek <prek::cli::Command as clap_builder::derive::Subcommand>::augment_subcommands
0.0%   0.4%  50.1KiB              prek <<prek::config::hook::HookWire as serde_core::de::Deserialize>::deserialize::__Visitor as serde_core::de::Visitor>::visit_map::<&mut <serde_saphyr::de::deserializer::YamlDeserializer as serde_core::de::Deserializer>::deserialize_map::MA>
0.0%   0.4%  49.7KiB              prek prek::run::{closure#0}
0.0%   0.4%  48.7KiB annotate_snippets annotate_snippets::renderer::render::render
0.0%   0.3%  43.9KiB              prek <<prek::config::Config as serde_core::de::Deserialize>::deserialize::__Visitor as serde_core::de::Visitor>::visit_map::<&mut <serde_saphyr::de::deserializer::YamlDeserializer as serde_core::de::Deserializer>::deserialize_map::MA>
0.0%   0.3%  41.1KiB              prek prek::cli::run::run::run::{closure#0}
0.0%   0.3%  39.7KiB              prek <prek::cli::RunOptions as clap_builder::derive::Args>::augment_args
0.0%   0.3%  32.7KiB              prek <prek::languages::rust::rust::Rust as prek::languages::LanguageBackend>::install::{closure#0}
0.0%   0.2%  28.8KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  28.7KiB      serde_saphyr <granit_parser::scanner::Scanner<granit_parser::input::str::StrInput>>::fetch_more_tokens
0.0%   0.2%  28.2KiB      serde_saphyr <granit_parser::scanner::Scanner<granit_parser::input::str::StrInput>>::fetch_more_tokens
0.0%   0.2%  28.0KiB        aws_lc_sys aws_lc_0_44_0_edwards25519_scalarmuldouble_alt
0.0%   0.2%  27.5KiB        aws_lc_sys aws_lc_0_44_0_edwards25519_scalarmuldouble
0.0%   0.2%  27.3KiB              toml <toml::de::deserializer::value::ValueDeserializer as serde_core::de::Deserializer>::deserialize_any::<<prek::config::hook::HookWire as serde_core::de::Deserialize>::deserialize::__Visitor>
0.0%   0.2%  27.0KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  27.0KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  27.0KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  26.9KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
4.2%  86.9%  11.1MiB                   And 20377 smaller methods. Use -n N to show more.
4.8% 100.0%  12.8MiB                   .text section size, the file size is 263.4MiB

[prek-ci-bot]

⚡️ Hyperfine Benchmarks

Summary: 1 regressions, 0 improvements above the 10% threshold.

Environment

• OS: Linux 6.17.0-1022-azure
• CPU: 4 cores
• prek version: prek 0.5.0+29 (a063885 2026-09-01)
• Rust version: rustc 1.98.0 (88d9e12ae 2026-08-18)
• Hyperfine version: hyperfine 1.20.0

CLI Commands

Benchmarking basic commands in the main repo:

prek --version

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base --version	2.4 ± 0.1	2.3	2.7	1.03 ± 0.05
prek-head --version	2.3 ± 0.1	2.2	2.7	1.00

prek list

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base list	9.6 ± 0.3	9.1	10.6	1.00
prek-head list	12.1 ± 14.1	9.4	136.6	1.27 ± 1.47

⚠️ Warning: Performance regression for prek list: 26.7500% slower

prek validate-config .pre-commit-config.yaml

⏭️ Skipped: .pre-commit-config.yaml not found

prek sample-config

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base sample-config	2.7 ± 0.1	2.6	2.9	1.01 ± 0.03
prek-head sample-config	2.7 ± 0.1	2.6	2.8	1.00

Cold vs Warm Runs

Comparing first run (cold) vs subsequent runs (warm cache):

prek run --all-files (cold - no cache)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run --all-files	39.3 ± 1.2	37.4	41.8	1.00
prek-head run --all-files	39.4 ± 0.6	38.0	40.1	1.00 ± 0.04

prek run --all-files (warm - with cache)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run --all-files	39.4 ± 1.0	37.7	42.0	1.00
prek-head run --all-files	39.5 ± 1.3	37.6	42.2	1.00 ± 0.04

Full Hook Suite

Running the builtin hook suite on the benchmark workspace:

prek run --all-files (full builtin hook suite)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run --all-files	39.0 ± 1.0	36.4	41.0	1.00
prek-head run --all-files	39.3 ± 1.4	37.2	45.2	1.01 ± 0.04

Individual Hook Performance

Benchmarking each hook individually on the test repo:

prek run trailing-whitespace --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run trailing-whitespace --all-files	14.0 ± 0.6	12.9	15.3	1.01 ± 0.05
prek-head run trailing-whitespace --all-files	13.9 ± 0.5	13.0	15.1	1.00

prek run end-of-file-fixer --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run end-of-file-fixer --all-files	12.1 ± 0.5	11.2	13.3	1.03 ± 0.06
prek-head run end-of-file-fixer --all-files	11.7 ± 0.5	10.8	12.9	1.00

prek run check-json --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-json --all-files	8.6 ± 0.4	8.0	9.5	1.00
prek-head run check-json --all-files	8.8 ± 0.3	8.3	9.3	1.02 ± 0.05

prek run check-yaml --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-yaml --all-files	8.4 ± 0.4	7.7	9.3	1.00
prek-head run check-yaml --all-files	8.6 ± 0.3	8.1	9.4	1.03 ± 0.06

prek run check-toml --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-toml --all-files	8.9 ± 0.3	8.6	9.5	1.03 ± 0.05
prek-head run check-toml --all-files	8.6 ± 0.3	8.0	9.2	1.00

prek run check-xml --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-xml --all-files	8.2 ± 0.4	7.7	9.1	1.00
prek-head run check-xml --all-files	8.4 ± 0.4	7.4	9.6	1.02 ± 0.07

prek run detect-private-key --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run detect-private-key --all-files	11.9 ± 0.7	10.8	13.5	1.06 ± 0.08
prek-head run detect-private-key --all-files	11.3 ± 0.5	10.7	12.7	1.00

prek run fix-byte-order-marker --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run fix-byte-order-marker --all-files	13.2 ± 0.8	12.0	14.7	1.00
prek-head run fix-byte-order-marker --all-files	13.4 ± 0.6	12.0	14.6	1.02 ± 0.08

Installation Performance

Benchmarking hook installation (fast path hooks skip Python setup):

prek install-hooks (cold - no cache)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base install-hooks	4.9 ± 0.1	4.8	5.1	1.00
prek-head install-hooks	5.1 ± 0.0	5.1	5.2	1.05 ± 0.03

prek install-hooks (warm - with cache)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base install-hooks	5.1 ± 0.1	5.0	5.2	1.00
prek-head install-hooks	5.1 ± 0.1	5.0	5.2	1.00 ± 0.03

File Filtering/Scoping Performance

Testing different file selection modes:

prek run (staged files only)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run	26.0 ± 0.5	25.2	26.9	1.01 ± 0.03
prek-head run	25.9 ± 0.7	25.1	27.2	1.00

prek run --files '*.json' (specific file type)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run --files '*.json'	5.5 ± 0.2	5.3	5.8	1.02 ± 0.03
prek-head run --files '*.json'	5.4 ± 0.1	5.3	5.5	1.00

Workspace Discovery & Initialization

Benchmarking hook discovery and initialization overhead:

prek run --dry-run --all-files (measures init overhead)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run --dry-run --all-files	7.4 ± 0.2	7.1	8.0	1.02 ± 0.04
prek-head run --dry-run --all-files	7.2 ± 0.1	7.1	7.5	1.00

Meta Hooks Performance

Benchmarking meta hooks separately:

prek run check-hooks-apply --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-hooks-apply --all-files	8.6 ± 0.1	8.4	8.9	1.00
prek-head run check-hooks-apply --all-files	8.6 ± 0.1	8.5	8.9	1.01 ± 0.02

prek run check-useless-excludes --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-useless-excludes --all-files	8.5 ± 0.1	8.4	8.6	1.01 ± 0.02
prek-head run check-useless-excludes --all-files	8.5 ± 0.2	8.3	8.9	1.00

prek run identity --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run identity --all-files	7.6 ± 0.2	7.4	7.8	1.00
prek-head run identity --all-files	8.0 ± 0.1	7.7	8.2	1.05 ± 0.03