[Gerrrt]

Problem

Opening a pwsh tab auto-attaches psmux, and the pane shells inside it came up with the stock PS> prompt instead of starship. exit back to the outer Windows Terminal shell showed starship again.

Root cause

• starship lost its scoop shim. In starship 1.27.0, the main bucket manifest switched from bin to env_add_path: ".". scoop no longer writes scoop\shims\starship.exe; it adds scoop\apps\starship\current to the User PATH in the registry.
• psmux panes run on a stale environment. With warm on, each __warm__ server spawns the next one from its own environment (the --spawner lineage). So panes inherit the PATH of whichever shell first started the pool. psmux show-environment -g showed a PATH from before the upgrade: no starship dir, plus the deleted pwsh 7.6.5/7.6.6 dirs.
• The profile skipped starship without a warning. In a pane, Test-Cmd starship is false, so 10-tools.ps1 skips the init. zoxide still loads because it has a shim, so prompt ended up as zoxide's wrapper around the default prompt.

Fix

• Merge-DotPathList (new, core/05-lib.ps1, exported by the Dotfiles module): appends the entries from -Add that the PATH string doesn't already have. Matching ignores case and a trailing \, and %VAR% entries are expanded before comparing. It never reorders or removes anything, so process-local prepends like mise shims keep their priority and a second run is a no-op.
• profile.ps1 calls it with the registry's Machine + User PATH right after the module import and before the layers load. That ordering matters because 00-aliases fingerprints PATH for the command cache. The cost is two registry reads and no spawn. A degraded load (module import failed) skips it.
• psmux.conf: added a note under warm on that the pool also freezes the environment, and that only PATH is now healed by the profile.

Verification

• Loaded the profile in a child pwsh using the exact stale PATH from psmux show-environment -g, with the mux markers set. The parent shell couldn't resolve starship; the child resolved scoop\apps\starship\current\starship.exe, DotfilesInit.Starship was True, and zoxide's prompt wraps starship's again.
• Pester: Lib, Module and LoadContract suites pass (268), including six new Merge-DotPathList cases.
• task.ps1 lint passes. A live pane still needs reload or a pool recycle (psmux kill-server -t __warm__) to pick up the new profile.

🤖 Generated with Claude Code

[Copilot]

🟢 Approval recommended

No active review issues remain for the PATH recovery changes.

No open issues 🎉

What changed in this PR

This PR restores tool discovery in PowerShell shells that inherit a stale PATH from psmux’s warm pool, addressing missing starship initialization while preserving process-local PATH precedence.

Changes:

• Adds and exports Merge-DotPathList to append missing PATH entries with normalized duplicate detection.
• Merges registry Machine and User PATH entries before profile layers initialize.
• Adds six helper tests and documents the warm pool’s environment behavior.

File	Description
tests/​Lib.Tests.ps1	Tests PATH merging, normalization, ordering, idempotence, and null handling.
psmux/​psmux.conf	Documents stale environments and the profile’s PATH recovery.
powershell/​profile.ps1	Appends missing registry PATH entries before loading layers.
powershell/​Dotfiles/​Dotfiles.psd1	Exports Merge-DotPathList.
powershell/​core/​05-lib.ps1	Implements the PATH merge helper and declares it in the load contract.

_{Review effort: Balanced}