fix(tests): isolate inherited skill configuration in CLI subprocesses #20

Summary

CLI tests can write state outside their per-test home because runSkills copies the parent process environment. A user-scope test that overrides only HOME still inherits XDG_STATE_HOME. Several agent/config/cache overrides can also remain inherited, making tests depend on or modify the caller's configuration.

Code evidence at 5d4987b:

• Tests/CoreTests/CLISurfaceTests.swift:981 starts from the full parent environment and overlays supplied values.
• Tests/CoreTests/CLISurfaceTests.swift:560 runs a user-scope add with only a HOME override at :572.
• Tests/CoreTests/CLISurfaceTests.swift:1017 clears CODEX_HOME and CLAUDE_CONFIG_DIR and sets XDG_CONFIG_HOME for some tests, but omits XDG_STATE_HOME and XDG_CACHE_HOME; other call sites use only HOME.
• Sources/Core/InstallLock.swift:110 prioritizes inherited XDG_STATE_HOME; Sources/Core/AgentRegistry.swift:88, :167, :173, and :184 consult cache/agent/config overrides.

Reproduction

Executed at 5d4987b. The executed case demonstrates XDG state leakage. Agent-specific override inheritance is established by the helper and registry code, not by a claimed run against real agent directories. The wrapper removes newly created OS fixture roots; run without concurrent test processes.

Run in Bash after cd "<checkout>" && swift build, replacing <checkout> with the absolute path of the checkout at this revision. Use a fresh reproduction directory. The commands isolate HOME, agent configuration, and XDG_*, and remove their fixture root on exit.

set -eu
checkout="<checkout>"
skill_bin="$checkout/.build/debug/skill"
repro_root="$checkout/.build/issue-repro-cli-environment"
mkdir -p "$repro_root/home" "$repro_root/tmp" "$repro_root/project"
trap 'rm -rf "$repro_root"' EXIT
isolated() {
  env -i PATH="$PATH" HOME="$repro_root/home" \
    CODEX_HOME="$repro_root/home/.codex" \
    CLAUDE_CONFIG_DIR="$repro_root/home/.claude" \
    XDG_CONFIG_HOME="$repro_root/home/.config" \
    XDG_STATE_HOME="$repro_root/home/.local/state" \
    XDG_CACHE_HOME="$repro_root/home/.cache" TMPDIR="$repro_root/tmp" \
    GIT_CONFIG_NOSYSTEM=1 GIT_CONFIG_GLOBAL=/dev/null \
    GIT_AUTHOR_NAME=Fixture [email protected] \
    GIT_COMMITTER_NAME=Fixture [email protected] \
    "$@"
}
skill() { isolated "$skill_bin" "$@"; }
cd "$repro_root/project"


cd "$checkout"
# Foundation may choose the OS temporary directory independently of TMPDIR.
fixture_base="$(isolated swift -module-cache-path "$repro_root/module-cache" -e 'import Foundation; print(FileManager.default.temporaryDirectory.path)')"
# Run without other test processes; track only the fixture roots created here.
isolated python3 - "$fixture_base" "$repro_root" <<'CODE'
import json, os, shutil, subprocess, sys
from pathlib import Path
base=Path(sys.argv[1])
root=Path(sys.argv[2])
prefixes=['skill-cli-tests','skill-cli-cli-tests']
before={p for name in prefixes for p in (base/name).glob('*')}
try:

    result=subprocess.run(['swift','test','--filter','installsUserScopedGeminiSkillInUniversalHome'])
    print('test exit:', result.returncode)
    p=root/'home/.local/state/skills/skills.resolved'
    print('resolved file written to inherited XDG_STATE_HOME:', p.exists())
    for pin in json.loads(p.read_text())['pins']:
        for skill in pin['skills']:
            for install in skill['installations']:
                print('skill:', skill['name'], 'installation in separate fixture root:', str(base/'skill-cli-cli-tests') in install['path'])

finally:
    after={p for name in prefixes for p in (base/name).glob('*')}
    for p in after-before:
        shutil.rmtree(p)
CODE

Observed output (relevant lines; temporary paths shortened to <temp>):

test exit: 0
resolved file written to inherited XDG_STATE_HOME: True
skill: gemini-demo installation in separate fixture root: True

Expected Behavior

Have the CLI subprocess helper construct a controlled environment by default, routing every state/cache/config location into the test's owned root. Tests that exercise override behavior should opt into explicit fixture paths.

Completion checks:

• Set parent CODEX_HOME, CLAUDE_CONFIG_DIR, and all relevant XDG_* variables to separate sentinel directories; CLI tests leave them unchanged.
• User-scope installs write their resolved state under the fixture's own root.
• Coverage includes callers currently passing only HOME and callers using isolatedCLIEnvironment.
• Required toolchain/PATH values remain available; run swift test.

Actual Behavior

The user-scope Gemini test passes while placing skills.resolved in the inherited state directory, outside the home created for that test. Its installation path points to a separate fixture root. All paths used by this reproduction are disposable; the demonstrated escape is from the per-test root, not from the outer reproduction environment.

Related: #10 concerns product watch scope, not test subprocess environments. PR #12 uses the partial isolation helper in newer tests; it does not close this gap. No duplicate found.

Environment

• Source revision: 5d4987b (5d4987b9e1f94e8b9f85124299f05d5aa4f45f07).
• CLI version: 0.2.1; built successfully with swift build.
• Swift: Apple Swift 6.4 (swiftlang-6.4.0.34.1, clang-2100.3.34.1).
• OS: macOS 27.0.1 (26A434).
• Architecture: arm64.
• Git: 2.42.0. Validation date: 2026-10-17.