A computing system may include a computing device configured to build modules of script code into bundles, and a bundler application executable to perform operations comprising: obtaining one or more of the modules of script code that are designated for bundling with one another; organizing the modules of script code into one or more chunks; for each respective chunk of the one or more chunks: (i) determining whether the respective chunk is to be assigned a deterministic chunk identifier or a non-deterministic chunk identifier, and (ii) assigning the respective chunk a chunk identifier as determined, where deterministic chunk identifiers are usable for referencing by additional modules of script code both within and not within in the respective chunk, and where the deterministic chunk identifiers are independent of characteristics of the computing device; and writing the one or more chunks to a bundle.