Need help wtih "unsupported modify tags operation:"

[J-Siu]

MacOS: 26.6
VSCode: Version: 1.128.0 (Universal)
VSCode Go(extension): 0.56.0
go version go1.26.5 darwin/arm64

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Recently when I try to "Go: Add Tags to Struct Fields", I get "unsupported modify tags operation:" error in the lower right corner of vscode.

In OUTPUT -> Extension Host:

2026-08-05 00:35:43.508 [error] Error: unsupported modify tags operation: 
	at handleResponse (/Users/js/.vscode/extensions/golang.go-0.56.0/dist/goMain.js:8411:40)
	at handleMessage (/Users/js/.vscode/extensions/golang.go-0.56.0/dist/goMain.js:8221:11)
	at processMessageQueue (/Users/js/.vscode/extensions/golang.go-0.56.0/dist/goMain.js:8236:13)
	at Immediate.<anonymous> (/Users/js/.vscode/extensions/golang.go-0.56.0/dist/goMain.js:8212:11)
	at process.processImmediate (node:internal/timers:504:21) gopls.modify_tags {"value":"golang.go","_lower":"golang.go"}
2026-08-05 00:35:43.508 [error] Error: unsupported modify tags operation: 
	at handleResponse (/Users/js/.vscode/extensions/golang.go-0.56.0/dist/goMain.js:8411:40)
	at handleMessage (/Users/js/.vscode/extensions/golang.go-0.56.0/dist/goMain.js:8221:11)
	at processMessageQueue (/Users/js/.vscode/extensions/golang.go-0.56.0/dist/goMain.js:8236:13)
	at Immediate.<anonymous> (/Users/js/.vscode/extensions/golang.go-0.56.0/dist/goMain.js:8212:11)
	at process.processImmediate (node:internal/timers:504:21) go.add.tags {"value":"golang.go","_lower":"golang.go"}

I can't find any reference in other places and seems to be a "me" problem.

Anyone has clue how I can debug this?

[sueun-dev]

Not a you problem, this reproduces here, and it is coming from gopls rather than the extension. gopls 0.22+ advertises interactiveResolveProvider: {"kinds":["command"]}, so vscode-go's forms feature sends command/resolve ahead of every workspace/executeCommand. resolveModifyTags in gopls/internal/golang/resolve.go switches on args.Modification and its default branch is that exact string. The palette command builds its args in goModifytags.ts with no modification key, hence the empty value after your colon.

Drove gopls v0.23.0 over stdio with the capability vscode-go declares: palette-shaped args return unsupported modify tags operation: , while by contrast the same request carrying "modification":"add" returns the tags/transform form and applies json:"name". v0.21.1 has no command/resolve handler, which matches this working before.

So check gopls version. The Refactor code action "Add struct tags" still works, because gopls fills Modification in when it builds that command itself, and the tags landed when I ran the whole handshake through it. Otherwise pin with go install golang.org/x/tools/gopls@v0.21.1. Looks unreported as well, nothing matching in this tracker or golang/go.

[J-Siu]

Thanks! Will check and report back.

[J-Siu]

The gopls version we have here was v0.23.0.

go install golang.org/x/tools/gopls@v0.21.1 fix this issue.

Thank you very much for the help!

[J-Siu]

It is now in #4070