CLAUDE_PLUGIN_ROOT inconsistent between hooks/skills and agent environment for local marketplace plugins

This issue is still reproducible in version 2.1.85

Root Cause Analysis

The regression was introduced in v2.1.83. The corresponding v2.1.83 changelog entry is:

Improved plugin startup — commands, skills, and agents now load from disk cache without re-fetching

This added a new "cache-only" session-start loader function (minified as Sc_ in v2.1.83) that doesn't exist in v2.1.81. The new function has a bug in its string-source branch.

Code comparison (from strings on the compiled binaries)

v2.1.81 — only has the full loader. For string-source plugins, it resolves from the marketplace source directory, then copies to the versioned cache and uses the cache path:

// v2.1.81 full loader (minified as $l_)
if (typeof A.source === "string") {
  let X = path.join(M, A.source);         // resolve from marketplace
  O = await copyToCache(X, K, W, A, M);   // copy to versioned cache, return cache path
  // plugin.path = cache directory ✓
}

v2.1.83 — added a separate Sc_ function for session-start that skips the copy. For string-source plugins, it resolves from the marketplace directory and uses it directly, ignoring the installPath parameter entirely:

// v2.1.83 cache-only loader (minified as Sc_)
async function Sc_(A, q, K, _, z, Y) {   // Y = installPath from installed_plugins.json
  let w;
  if (typeof A.source === "string") {
    let $ = (await stat(q)).isDirectory() ? q : path.join(q, "..");
    w = path.join($, A.source);            // resolve from marketplace dir, use directly
    // installPath parameter Y is IGNORED
    // plugin.path = source directory ✗
  } else {
    if (!Y || !await exists(Y)) { /* error */ return null; }
    w = Y;                                 // correctly uses installPath
    // plugin.path = cache directory ✓
  }
  return loadPlugin(A, K, _, z, w);
}

The installPath parameter is available but only used in the else branch (object-source plugins like github/git/npm). String-source plugins ("source": "./plugin") take the wrong branch.

Impact

The source directory path flows into:

1. hooks.json command string substitution (${CLAUDE_PLUGIN_ROOT} → source dir)
2. Hook process environment (CLAUDE_PLUGIN_ROOT env var → source dir)
3. Skill preprocessor directives (${CLAUDE_PLUGIN_ROOT} in SKILL.md → source dir)
4. MCP server config (CLAUDE_PLUGIN_ROOT in stdio env → source dir)

The agent's own Bash environment is the only context that correctly uses installPath.

See also #39156 which reports the same underlying bug from the skill loader perspective.

Workaround: set it yourself at the top of each hook:

CLAUDE_PLUGIN_ROOT="${CLAUDE_PLUGIN_ROOT:-$HOME/.claude/plugins}"
exit 0

Workaround: set it yourself at the top of each hook: CLAUDE_PLUGIN_ROOT="${CLAUDE_PLUGIN_ROOT:-$HOME/.claude/plugins}" exit 0

The plugin root should point to the root of the actual plugin (e.g. /home/somebody/.claude/plugins/cache/some-marketplace/some-plugin/1.0.0/ . You can obviously still hack this but it's a bit more complicated than what you suggest.

This issue seems to be fixed in 2.1.94:

Fixed ${CLAUDE_PLUGIN_ROOT} resolving to the marketplace source directory instead of the installed cache for local-marketplace plugins on startup

It works locally for me.

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