Regression in 2.1.87+: project-local .claude/commands/ not discovered after subprocess isolation change

[nigel-upstart]

Summary

Starting with the bump to Claude Code 2.1.87 (action commit 32156b12, "Add subprocess isolation setup and git credential helper", 2026-03-31), project-local .claude/commands/ files are no longer loaded. Any /skill-name prompt returns "Unknown skill: <name>" immediately with num_turns: 2, duration_ms: ~25, and zero tokens consumed.

Steps to reproduce

1. Place a custom command at .claude/commands/my-command.md in $GITHUB_WORKSPACE (either checked-in or copied there before the action runs)
2. Invoke via prompt: /my-command
3. On 2.1.86 and earlier: command is found and executed
4. On 2.1.87+: "result": "Unknown skill: my-command"

Session config comparison

slash_commands on 2.1.84 (working):

"my-command", "other-project-command", ... <-- project commands present

slash_commands on 2.1.89 (broken):

"update-config", "debug", "simplify", ... <-- only built-ins, project commands absent

Result JSON on 2.1.87+

{
  "result": "Unknown skill: my-command",
  "num_turns": 2,
  "duration_ms": 23,
  "total_cost_usd": 0,
  "permission_denials": []
}

Environment

• Runner: ubuntu-latest (GitHub-hosted)
• USE_AGENT_SDK: "false" (CLI mode)
• AWS Bedrock
• .claude/commands/ populated via rsync before action runs (confirmed files exist on disk)
• Confirmed working: e7b588b6eaa5263c2e7c6c7b34a29e190d32ee68 (2.1.86)
• Confirmed broken: 2.1.87, 2.1.88, 2.1.89

Root cause hypothesis

Commit 32156b12 adds subprocess isolation. The subprocess likely runs with a fresh/isolated working directory or HOME, so $GITHUB_WORKSPACE/.claude/commands/ is no longer visible to the Claude process at startup. The 6 default skills bundled with the action (update-config, debug, etc.) still load, suggesting those come from a fixed path inside the action itself.

Workaround

Pin to the full SHA of 2.1.86:

uses: anthropics/claude-code-action@e7b588b6eaa5263c2e7c6c7b34a29e190d32ee68

Request

Please ensure the subprocess isolation setup preserves discovery of project-local .claude/commands/ from $GITHUB_WORKSPACE, consistent with the behaviour prior to 2.1.87.