Function apply_with_target 

pub fn apply_with_target(
    surface: &AgentSurface,
    value: Value,
    target: Option<Map<String, Value>>,
) -> Result<Value, AppError>

The body of apply, with the resolved target supplied rather than read.

The target lives in a process-wide OnceLock, which is correct for a one-shot binary and wrong for a test binary: paths and agent_surface unit tests share one process, so whether a target exists would depend on which test ran first. Taking it as an argument makes every test state its own premise, and keeps the production call site the only place that reads global state.

Errors

Returns AppError::Usage when the request cannot be honoured as asked.