Go — inconsistent vendoring error

Fix inconsistent vendoring by syncing the vendor directory with go.mod or disabling vendoring explicitly.

beginnerdebugginggomodules

Symptoms

inconsistent vendoring
go: inconsistent vendoring of module X
The build uses a vendor directory that no longer matches go.mod
CI fails after a dependency update

Possible causes

go.mod or go.sum changed without updating the vendor directory
The vendor directory exists but is stale
Build flags force vendor mode while dependencies changed
A dependency was added without running go mod vendor

Diagnosis steps

Read what is inconsistent

go build ./... 2>&1 | head -20

Interpretation

The message names the module and the mismatch, such as missing from vendor or present only in vendor.

Regenerate the vendor directory

go mod tidy && go mod vendor

Interpretation

Tidying first resolves go.sum, and vendoring copies exactly what go.mod requires so the two agree.

Decide vendor or modules explicitly

go env GOFLAGS && ls vendor/modules.txt

Interpretation

If vendoring is not intended, remove the directory and ensure the build does not force -mod=vendor.

Root cause

The build used the vendor directory while go.mod and go.sum described a different dependency set, so the vendored sources did not match what the build expected.

Fix

Run go mod vendor after any dependency change so vendor matches go.mod, or remove the vendor directory and let the module cache resolve dependencies, keeping the build mode explicit.

Verify the fix

Build and test again and confirm the inconsistency is gone, and confirm the vendored dependency versions match go.mod.

Symptom walkthrough

The build fails with inconsistent vendoring, naming a module that is missing from or extra in the vendor directory. The vendor directory is a snapshot of dependencies, so any change to go.mod or go.sum without regenerating it leaves the two out of sync. CI frequently fails this way after a dependency update that was not accompanied by a vendor regeneration.

Fix in practice

After any dependency change, run go mod tidy and then go mod vendor so the snapshot matches the module requirements. If the project does not intend to vendor, remove the directory and keep the build mode consistent so it does not force vendor mode.

Verification

Rebuild and run the tests and confirm the inconsistency is gone, then confirm the vendored module versions match those in go.mod. Agreement between the snapshot and the module file confirms the fix.

Diagnostic commands

Check the behavior with commands like these:

go build ./... 2>&1 | head -20
go mod tidy && go mod vendor
go env GOFLAGS && ls vendor/modules.txt