pcall versus xpcall for deployment error visibility

When a Lua module fails during repeated deployment attempts, the choice between pcall and xpcall determines the amount of diagnostic information available to the caller. pcall protects against errors but returns the error as a second argument that must be manually inspected, and it does not provide stack trace context beyond what the error object contains. xpcall permits a custom error handler that can augment the default behavior, yet the handler executes within the same thread and may itself raise an error, potentially obscuring the original failure. Lua 5.4 introduces debug.getupvalue and debug.setupvalue, enabling inspection of local variables in error contexts, but Lua 5.3 and earlier lack this capability. Additionally, the require function caches modules, so a failed first load may silently reuse a partially loaded module on retries, and tail call optimization removes intermediate stack frames, affecting the granularity of error location data.

Given these documented behaviors, which approach provides sufficient stack trace fidelity for deployment diagnostics across Lua 5.1 through 5.5? Under what conditions does an xpcall handler preserve the original error context without introducing secondary failures? How does module caching interact with error-handling strategy to limit repeat-deployment reliability?