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• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pixi, using pixi --version.

Reproducible example

Commands I ran and their output:

# Create a simple test
JSON='{"a": "b\"c"}'

# Direct execution - works correctly
python3 -c "import sys, json; print(repr(sys.argv[1])); json.loads(sys.argv[1])" "$JSON"
# Output: '{"a": "b\\"c"}'
# ✓ Valid JSON

# Via pixi run - fails
pixi run python -c "import sys, json; print(repr(sys.argv[1])); json.loads(sys.argv[1])" "$JSON"
# Output: '{"a": "b\\\\"c"}'
# ✗ json.decoder.JSONDecodeError: Expecting ',' delimiter

pixi.toml/pyproject.toml file that reproduces my issue:

[workspace]
authors = ["'Harry Brady' <x>"]
channels = ["condaforge"]
name = "pixi-escape-repro"
platforms = ["linux-64"]
version = "0.1.0"

[dependencies]
python = ">=3.14.0,<3.15"

pixi info output:

System
------------
       Pixi version: 0.59.0
           Platform: linux-64
   Virtual packages: __unix=0=0
                   : __linux=4.18.0=0
                   : __glibc=2.28=0
                   : __archspec=1=skylake_avx512
          Cache dir: /home/hbrady/.cache/rattler/cache
       Auth storage: /home/hbrady/.config/pixi/credentials.json
   Config locations: /home/hbrady/.config/pixi/config.toml

Other files (e.g. script files, source files, etc.):

Issue description

When passing command-line arguments containing backslash escape sequences (like \" or \n) through pixi run, the backslashes are incorrectly double-escaped before being passed to the subprocess. This breaks JSON parsing and other use cases that rely on properly escaped strings.

When I tested downgrading versions, the version at which this begins to occur is 0.53.0

Expected behavior

JSON='{"a": "b\"c"}'

pixi run python -c "import sys, json; print(repr(sys.argv[1])); json.loads(sys.argv[1])" "$JSON"
# Output: '{"a": "b\\"c"}'
# ✓ Valid JSON