WordPress plugin agent tasks fail when bundled CLI wrapper is not executable

[chubes4]

Problem

An installed WP Codebox WordPress plugin can contain vendor/wp-codebox-cli/bin/wp-codebox without its executable mode. WP_Codebox_Agent_Sandbox_Runner::default_bin() selects that file whenever it exists, and command_prefix() resolves a Node runtime for the bundled wrapper but then discards it and executes the wrapper path directly.

The public wp codebox run-agent-task path then fails before sandbox creation:

sh: .../vendor/wp-codebox-cli/bin/wp-codebox: Permission denied
exit_code: 126

This is reproducible on a WordPress Studio plugin installation. Zip extraction does not reliably preserve executable mode, so package-time chmod(0755) is not a sufficient runtime contract.

Expected behavior

The WordPress plugin runner should invoke the bundled JavaScript CLI through the Node runtime already resolved by command_prefix(). Execution must not depend on the extracted shell wrapper retaining executable mode.

Acceptance criteria

• A packaged plugin whose bundled shell wrapper is non-executable can run agent tasks.
• The bundled JavaScript entrypoint is invoked through a validated bundled or host Node runtime.
• Explicit standalone CLI commands and configured JavaScript paths retain their current behavior.
• Deterministic coverage reproduces the non-executable-wrapper installation shape.

Evidence

Observed through wp-codebox/run-agent-task:

• status: failed
• failure classification: invalid_json
• process exit: 126
• underlying output: Permission denied

The invalid-JSON classification is secondary; the process never starts.

AI assistance

OpenCode using openai/gpt-5.6-sol diagnosed the public Codebox task failure, traced it to the bundled wrapper invocation in WP_Codebox_Agent_Sandbox_Runner::command_prefix(), and drafted this report. Chris Huber reviewed the reported behavior.