• tsup 6.2.2
• using esbuild 0.21.5
• running on Node 18.20.1

Problem

When running tsup or tsup-node with a config file (either the standard file name scheme or by setting --config with a file name), esbuild throws an error:

Invalid option in build() call: "watch"
// from node_modules\esbuild\lib\main.js:253:12

❌ The error is thrown:

• when using a tsup.config.* config file
• when using --config some_config.ts
• when using --watch with a custom config (--config or config file)

All of these even with watch omitted, watch: false or watch: undefined inside the config file.

✔️ The error is not thrown:

• when using --no-config
• when using --watch without a custom config (--config or config file)

Possible cause

So it seems the parsing of the options from a config file handles the watch option different from the CLI --watch argument. Resulting in a --watch argument added to the esbuild command, which is not allowed anymore (see release notes from esbuild).