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This section details on the original issue you should resolve

<issue_title>Error or warn when the hash length is below the minimum hash length</issue_title>
<issue_description>> Hmm but I just did that repro above 15 minutes ago, and I just verified I have the latest published version of rolldown-vite (6.3.0-beta.5). But if it's fixed for next release I have no trouble waiting! 🙏🏼

(BTW when I was trying to repro earlier, another problem I saw was that [hash:2] becomes 6 characters, same for [hash:3], [hash:4], [hash:5]... seems there's a minimum of 6?)

Originally posted by @blixt in #4017</issue_description>

<agent_instructions>entryFileNames and chunkFileNames limits the minimum length to 6 because of the way Rollup / Rolldown handles the hash in the filename. Rollup / Rolldown uses a hash placeholder until the hash is determined (as the hash is determined by the file content, the filename has to be replaced with a placeholder to be contained in the file itself). This hash placeholder looks like !{1} and that requires the minimum length of 6.

Because of the technical limitation above, I think it's not possible to reduce the hash length for entryFileNames and chunkFileNames. The minimum hash length is inconsistent between entryFileNames/chunkFileNames and assetFileNames, but I think that's fine because there's no reason to limit that. But I think we need to error when the length is shorter than the minimum length, or emit a warning if we still want to increase the length automatically. While warning might be slightly better as the user can still build, I think an error is also fine as it aligns the behavior with Rollup. I think we can choose the one easier to implement.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@shulaoda > So the current logic is not internally consistent, and probably asset naming should have a minimum of 6 as well until a decision is made whether or not to support shorter hashes overall.

Yes, but I guess this behavior aligns with rollup.</comment_new>
<comment_new>@sapphi-red
Rollup throws an error when using [hash:2] in entryFileNames or chunkFileNames (stackblitz).
Currently, Rolldown converts [hash:2] to [hash:6] automatically (stackblitz).

Related: rollup/rollup#6098

@sapphi-red `entryFileNames` and `chunkFileNames` limits the minimum length to 6 because of the way Rollup / Rolldown handles the hash in the filename. Rollup / Rolldown uses a hash placeholder until the hash is determined (as the hash is determined by the file content, the filename has to be replaced with a placeholder to be contained in the file itself). This hash placeholder looks like `!~{1}~` and that requires the minimum length of 6.

Because of the technical limitation above, I think it's not possible to reduce the hash length for entryFileNames and chunkFileNames. The minimum hash length is inconsistent between entryFileNames/chunkFileNames and assetFileNames, but I think that's fine because there's no reason to limit that. But I think we need to error when the length is shorter than the minimum length, or emit a warning if we still want to increase the length automatically. While warning might be slightly better as the user can still build, I think an error is also fine as it aligns the behavior with Rollup. I think we can choose the one easier to implement.