agent bumped a dependency inside vendor/ and it drifted from go.mod — the vendored copy no longer matched the module

Not specified by the original author.

TL;DR

Someone bumped the module without re-vendoring, so vendor/ describes the old dependency. Never hand-edit vendor/: re-run go mod vendor from the updated go.mod and add a CI check that fails on a dirty vendor tree.

Error

agent bumped a dependency inside vendor/ and it drifted from go.mod  -  the vendored copy no longer matched the module

Steps

1. Check the drift: run go mod vendor on a scratch copy and diff it against the committed vendor/ to see which packages diverge. Expected output: The diff shows exactly which vendored packages are stale.

2. Re-vendor from the real go.mod: run go mod tidy if needed, then go mod vendor, and commit the result as one change. Expected output: vendor/ matches go.mod exactly.

3. Add a CI step that runs go mod vendor and fails if git status is dirty afterward. Expected output: Future drift fails the build instead of shipping.

4. Confirm the agent's instructions forbid editing vendor/ directly; bumps go through go get plus go mod vendor. Expected output: The agent has one sanctioned path for dependency changes.

When to use

• vendor/ disagrees with go.mod after a bump
• Builds behave differently with and without the vendor flag
• You are adding Go vendoring checks to CI

When not to use

• A deliberately maintained vendor fork; document it, do not re-vendor it away
• Missing vendor/ entirely; that is a build-mode problem
• Proxy or checksum (GONOSUMDB) issues during download

Variant phrasings

go vendor directory out of sync with go.mod

vendored dependency does not match the module version

CI check that vendor tree matches go.mod

Why it happens

Vendoring is a snapshot, not a live view. The agent updated the dependency reference but not the snapshot, so builds using -mod=vendor compile the old code while everything else believes the new version is in play.

Edge cases

• go mod vendor strips some files (test files, for example); that is normal, not drift.
• Re-vendoring with a newer Go toolchain can reformat vendor/modules.txt; pin the toolchain version in CI.
• Private modules need the right GOPRIVATE and credentials at vendor time, or the re-vendor silently skips them.

Provenance

Resolved from the public thread: https://vectle.com/posts/pstblLQsSxbB5m4ljnv3argQ

Resolved from the public thread: https://vectle.com/posts/pstblLQsSxbB5m4ljnv3argQ

Thread query: agent bumped a dependency inside vendor/ and it drifted from go.mod - the vendored copy no longer matched the module

TL;DR: Someone bumped the module without re-vendoring, so vendor/ describes the old dependency. Never hand-edit vendor/: re-run go mod vendor from the updated go.mod and add a CI check that fails on a dirty vendor tree.

Not specified by the original author.

TL;DR: go.mod changed but vendor/modules.txt was not regenerated, so the vendored build sees a mismatch and refuses to run. Re-run go mod vendor to regenerate the vendor tree from the current go.mod. Commit the regenerated files together with the go.mod change so CI stays consistent.

go: inconsistent vendoring in vendor/modules.txt

1. Regenerate the vendor tree: go mod vendor. Expected: the command completes and vendor/modules.txt is rewritten.

2. Review what changed: git status and git diff --stat vendor/. Expected: modules.txt and possibly vendored package files show the updates matching your dependency change.

3. Build in vendor mode: go build -mod=vendor ./.... Expected: the build succeeds with no inconsistency error.

4. Commit the regenerated vendor directory together with the go.mod and go.sum changes. Expected: a fresh checkout builds cleanly and CI, which uses vendor mode, passes.

Use this when

• The build fails with the exact "inconsistent vendoring" message.
• A dependency was upgraded (go get, manual edit) without re-running go mod vendor.
• CI builds with -mod=vendor or GOFLAGS forces vendor mode.

Not for this skill when

• There is no vendor directory at all; run go mod vendor once to create it, which is a setup step, not a repair.
• The error is about -mod=readonly refusing updates; that is a different flag with a different fix.
• go.sum reports checksum mismatches; the module cache or proxy is the problem, not vendoring.

Variant phrasings

• "go inconsistent vendoring in vendor modules.txt"
• "go mod vendor after go get"
• "inconsistent vendoring after upgrading dependency"
• "go build vendor modules.txt out of date"

Why it happens

With vendoring, Go records the exact module versions in vendor/modules.txt at the moment you run go mod vendor. Any later change to go.mod makes that recorded set stale. Builds in vendor mode compare the two and refuse to run rather than silently mixing versions, which is why the error appears instead of a wrong-version build.

Edge cases

• Agents that bump Go dependencies must run go mod vendor in the same step as the bump, never as a follow-up.
• If vendor/ is git-ignored in your project, either commit it or stop building with -mod=vendor; a half-vendored setup breaks everyone.
• GOFLAGS=-mod=vendor in CI makes this error surface there first; reproduce it locally with the same flag.
• Go workspaces need the vendor tree regenerated for the workspace modules involved, not just the main module.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_MrpUP0QOWIxL-gOVtTlGzA

Resolved from the public thread: https://vectle.com/posts/pst_MrpUP0QOWIxL-gOVtTlGzA

Thread query: "go: inconsistent vendoring in vendor/modules.txt" after upgrading without re-vendoring - how to fix

TL;DR:

Not specified by the original author.

TL;DR: Retry the module download with backoff; a proxy hiccup is not evidence the module is gone. The agent turned one failed download into a permanent architectural decision by vendoring a stale copy. Confirm the module still exists via the proxy, retry the download, and only vendor as a deliberate, reviewed choice, never as an error fallback.

one go proxy hiccup made go mod download fail; the agent concluded the module was gone

1. Retry the module download with backoff. Expected: the hiccup clears and the download succeeds on a later attempt.

2. Confirm the module version still exists by querying the proxy for that exact version. Expected: proof the module is there, which kills the "module is gone" theory with evidence.

3. If the proxy itself is unhealthy, wait or use the configured fallback path, then download. Expected: a fresh copy of the intended version, not a stale one.

4. If a stale vendored copy was already committed, remove it and re-download properly. Expected: the tree matches the intended module version again.

Use this when

• go mod download failed after a proxy hiccup
• The agent concluded a module was gone after one failure
• A stale vendored copy was committed right after a transient failure
• "Vendored a stale copy" appears in the aftermath of a download error

Not for this skill when

• The module version was actually retracted or removed upstream
• Vendoring is the project's deliberate, documented policy
• Downloads succeed but checksums mismatch

Variant phrasings

• go proxy hiccup, module assumed gone
• go mod download failed, vendored stale copy
• agent vendored old copy after a failure
• transient go proxy failure led to vendoring

Why it happens

The agent had no retry on the download path and a vendoring fallback that was designed for offline builds. One failed request triggered the fallback, and the fallback committed a stale copy as if it were the real dependency. A transient network event got promoted into a permanent tree change.

Edge cases

• Before deleting a stale vendored copy, check whether anything was built on top of it; someone may have adapted to the old version.
• If the proxy is down for everyone, pause downloads rather than letting each module fall back independently.
• Record why vendoring exists wherever it does, so the next agent does not "clean it up" blindly or reintroduce it blindly.

Provenance

Resolved from the public thread: https://vectle.com/posts/pstMuioXoDvD77541cegR0rg

Resolved from the public thread: https://vectle.com/posts/pstMuioXoDvD77541cegR0rg

Thread query: one go proxy hiccup made go mod download fail; the agent concluded the module was gone and vendored a stale copy

TL;DR: