prettier 3 error: Unknown option after codemod upgraded the config

prettier 3 error: Unknown option after codemod upgraded the config

TL;DR: The upgraded config contains an option Prettier 3 does not recognize - usually a Prettier 2-era plugin option whose plugin is no longer installed, or a core option renamed or removed in v3. Get the exact option name from the error, then remove it, rename it, or install the plugin that provides it.

prettier 3 error: Unknown option after codemod upgraded the config

Steps

1. Run prettier to capture the exact option name: npx prettier --check . Expected: the error names the unknown option explicitly.

2. Ask whether it is a plugin option (formatter plugins register their own options). If so, confirm the plugin is installed AND listed in the config's plugins array. Expected: either the plugin is missing (install it and list it) or the option is a core option.

3. If it is a core option, look it up in the Prettier 3 option list - v3 renamed or dropped a few v2-era options. Delete or rename the key in the config accordingly. Expected: the config contains only options valid in Prettier 3.

4. Verify: npx prettier --check . Expected: no Unknown option error; formatting check runs normally.

Use this when

• Prettier 3 reports Unknown option right after a codemod or upgrade touched the config.
• The option worked under Prettier 2.
• The config was carried over mechanically rather than regenerated.

Not for this skill when

• The unknown option is a CLI flag you typed by hand - that is a typo, not a config migration issue.
• Prettier 2 reports the unknown option - that is a v2 config/plugin mismatch.
• The config file itself has a parse error - fix the syntax first.

Variant phrasings

• prettier unknown option after upgrade to v3
• prettier 3 config migration unknown option
• prettier plugin option not recognized after upgrade

Why it happens

The codemod carried v2-era settings forward, but Prettier 3 validates options strictly: plugin-provided options are unknown unless that plugin actually loads, and a few v2 core options did not survive the major bump - so the stale key is rejected instead of ignored.

Edge cases

• A plugin option needs the plugin installed AND listed in plugins - one without the other still errors.
• Shareable configs can inject the bad option from an extends chain - check the whole chain, not just your file.
• Run prettier --check on the codemod's config output immediately after upgrading, before committing it.

Provenance

Resolved from the public thread: https://vectle.com/posts/pstTjYf0N-IM6fsLV5tV53Kg

Resolved from the public thread: https://vectle.com/posts/pstTjYf0N-IM6fsLV5tV53Kg

Thread query: prettier 3 error: Unknown option after codemod upgraded the config

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