[BUG]: Project-level skills not discovered when .claude/skills is a symlink in git worktree sandbox #18848

Description

Project-level skills in .claude/skills/ are not discovered when the directory is a symlink and the session runs in a git worktree sandbox (not the main repo).

Reproduction

Setup

• Main repo at /Users/me/code/my-project with .claude/skills/ as a symlink (e.g., to a git submodule)
• OpenCode worktree sandbox at ~/.local/share/opencode/worktree/<id>/my-sandbox
• The symlink resolves correctly — ls .claude/skills/ shows all skill directories
• opencode.json includes "skills": { "paths": [".claude/skills"] }

Symlink structure

.claude/skills -> ../.pal-skills/.claude/skills   (symlink to submodule)
.agents/skills -> ../.claude/skills               (symlink chain)

Both resolve correctly on the filesystem. Python glob.glob() and Bun Glob.scan({ followSymlinks: true }) both find 23 SKILL.md files through the symlinks.

Expected

skill("my-project-skill") returns the skill content. Project skills appear in <available_skills>.

Actual

skill("my-project-skill") returns "not found". Only user-level skills (~/.claude/skills/, ~/.agents/skills/) and opencode-config skills (~/.config/opencode/skills/) are available.

Root Cause Analysis

I decompiled the binary and traced the issue through src/skill/index.ts and src/skill/discovery.ts:

1. Glob doesn't follow directory symlinks

Glob.scan is called with symlink: true, which toGlobOptions() maps to follow: true:

function toGlobOptions(options) {
    return {
        cwd: options.cwd,
        absolute: options.absolute,
        dot: options.dot,
        follow: options.symlink ?? false,  // symlink: true → follow: true
        nodir: options.include !== "all"
    };
}

However, empirical testing with Bun shows:

// followSymlinks: true → 23 skills found
// Without followSymlinks → 0 skills found

The npm glob package (bundled as Ze) uses follow, but the actual traversal may not follow directory symlinks — only file symlinks. When .claude/skills is a symlink to a directory, the glob pattern skills/**/SKILL.md finds nothing because it doesn't descend into the symlinked directory.

2. Per-sandbox skill isolation

The skill system creates per-session state via create(discovery, directory, worktree). The directory for a worktree sandbox is the sandbox path, not the main repo. Desktop app logs confirm:

• Skills scanned from the main repo path show up in WARN logs (duplicate skill names)
• But those skills are NOT available to the sandbox session
• The sandbox session's own scan finds 0 skills due to the symlink issue above

Evidence from logs

Desktop app log (~/Library/Logs/ai.opencode.desktop/):

WARN service=skill name=fastapi existing=.../pal-mono/.claude/skills/fastapi/SKILL.md 
     duplicate=.../pal-mono/.agents/skills/fastapi/SKILL.md

Skills ARE found when scanning from the main repo. But skill("fastapi") returns "not found" in the sandbox session.

Environment

• OpenCode Desktop v1.3.0 (macOS arm64)
• macOS Sequoia
• Git worktrees (not bare clones)
• .claude/skills is a git-tracked symlink (mode 120000) pointing to a submodule directory

Workaround

Replace symlinks with real directories (copy files instead of symlinking to submodule). This defeats the purpose of using a shared skills submodule.

Suggested Fix

1. Ensure Glob.scan follows directory symlinks when traversing — either use Bun's native followSymlinks: true or fs.realpathSync on the cwd before scanning
2. Consider sharing skill state across sandboxes within the same project, since they share the same .claude/skills/ content