Function build_tool_args 

pub async fn build_tool_args(
    args: &[Arg],
    ctx: &ExecContext,
    schema: Option<&ToolSchema>,
) -> Result<ToolArgs, String>

Build ToolArgs from AST Args, evaluating expressions — the reduced sync wrapper around the shared crate::kernel::bind_tool_args core. Used by scatter/gather’s own option parsing (run_scatter_gather, below — before any worker forks, so it can’t recurse back into PipelineRunner::run for command substitution) and the #[cfg(test)] BackendDispatcher (dispatch.rs).

GH #188: this used to be a hand-rolled twin of Kernel::build_args_async’s flag/positional-binding logic that could — and did — drift from it (no undeclared-space-flag guard, no glued-short-flag handling, no consumes/repeatable accumulation). Now it’s a thin wrapper: the binding logic itself is shared via SyncEvalSource, and only expression evaluation differs (this context can’t run $(...)).