fix(env): prevent PATH corruption when paths are interleaved with original PATH

[jdx]

Problem

Users reported that Homebrew tool paths disappeared from PATH after upgrading from v2025.10.19 to v2025.10.20 (#6820).

The issue manifested when paths from the user's original PATH were interleaved with user-added paths (e.g., Homebrew paths).

Example scenario that triggered the bug:

• Original PATH (when mise was activated): /usr/local/bin:/usr/bin:/bin
• Current PATH (after shell config ran): /opt/homebrew/opt/curl/bin:/usr/local/bin:/opt/homebrew/opt/findutils/libexec/gnubin:/usr/bin:/bin

The PATH reconstruction logic would break when it encountered the first path from the original PATH (/usr/local/bin), causing any subsequent non-original paths (/opt/homebrew/opt/findutils/libexec/gnubin) to be lost.

Root Cause

Commit 8855cba (#6800) introduced a PATH reconstruction algorithm in build_path_operations() that collected "pre" paths (user additions) by iterating through current PATH and breaking as soon as it found a path that existed in the original PATH.

This assumed PATH would always look like: [new paths] [original PATH]

However, when paths are interleaved (common when shell configurations add paths at different points during initialization), paths appearing after the first original PATH match would be lost.

Solution

Modified build_path_operations() in src/cli/hook_env.rs:

1. Remove early break

Collect ALL paths that aren't in the original PATH, regardless of their position in the current PATH. This correctly handles interleaved paths:

// OLD (buggy):
for path in &current_paths {
    if !orig_set.contains(path) {
        pre.push(path.clone());
    } else {
        break;  // ❌ Stops too early!
    }
}

// NEW (fixed):
for path in &current_paths {
    if !orig_set.contains(path) {
        pre.push(path.clone());
        // ✅ Continues collecting ALL non-original paths
    }
}

2. Enhanced duplicate filtering

Filter installs against both post (original PATH) AND pre (user additions) to prevent duplicates when mise paths from previous activations exist in current PATH.

3. Preserve original behavior

The fix maintains compatibility with existing PATH reconstruction logic while fixing the interleaving bug.

Testing

Added e2e/env/test_path_interleaved_regression to verify the fix works correctly when paths are interleaved with original PATH entries.

Impact

This fix ensures that:

• ✅ Homebrew tool paths are preserved across mise activations
• ✅ User-added paths are correctly maintained regardless of their position relative to original PATH
• ✅ No duplicate paths are introduced
• ✅ Original PATH is preserved exactly

Fixes #6820

🤖 Generated with Claude Code

---

Note

Fixes PATH reconstruction to preserve interleaved user paths and avoid duplicates; adds an e2e regression test.

• Env PATH handling (src/cli/hook_env.rs):
  • Collects all non-original paths into pre (removes early break), supporting interleaved PATH entries.
  • De-duplicates installs against both post (original PATH) and pre (user additions), including canonical path checks.
  • Rebuilds PATH as pre + installs_filtered + post.
• Tests:
  • Adds e2e regression test e2e/env/test_path_interleaved_regression to verify Homebrew/system paths are preserved when interleaved.

^{Written by Cursor Bugbot for commit 1c18408. This will update automatically on new commits. Configure here.}

[Copilot]

Pull Request Overview

Fixes a PATH corruption bug introduced in v2025.10.20 where user-added paths (like Homebrew tools) were lost when interleaved with original PATH entries. The issue occurred when the PATH reconstruction algorithm would stop collecting "pre" paths after encountering the first original PATH entry, losing any subsequent user additions.

• Removed early break condition in PATH reconstruction to collect ALL non-original paths
• Enhanced duplicate filtering to check against both original PATH and user additions
• Added comprehensive test case for the interleaved PATH scenario

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/cli/hook_env.rs	Fixed PATH reconstruction logic to handle interleaved paths and improved duplicate filtering
e2e/env/test_path_interleaved_regression	Added test case verifying fix for interleaved PATH scenarios

---

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[github-actions]

Hyperfine Performance

mise x -- echo

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2025.10.20 x -- echo	20.1 ± 0.6	18.8	25.2	1.00 ± 0.05
mise x -- echo	20.1 ± 0.8	18.7	25.2	1.00

mise env

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2025.10.20 env	19.1 ± 0.6	17.9	23.9	1.00
mise env	19.3 ± 0.7	17.8	21.2	1.01 ± 0.05

mise hook-env

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2025.10.20 hook-env	19.4 ± 0.5	17.9	23.8	1.00
mise hook-env	19.8 ± 0.7	18.3	22.0	1.02 ± 0.05

mise ls

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2025.10.20 ls	16.7 ± 0.6	15.4	19.7	1.00
mise ls	17.9 ± 0.6	16.6	20.0	1.07 ± 0.05

xtasks/test/perf

Command	mise-2025.10.20	mise	Variance
install (cached)	112ms	110ms	+1%
ls (cached)	66ms	67ms	-1%
bin-paths (cached)	72ms	72ms	+0%
task-ls (cached)	497ms	483ms	+2%