fix(ci): align ECR mock_balances build-arg name with Dockerfile

[bdchatham]

Summary

The ECR workflow passed SEI_CHAIN_BUILD_TAGS=mock_balances as a Docker build-arg, but the Dockerfile declares ARG GO_BUILD_TAGS="". Docker silently ignores build-args that don't match a declared ARG, so the resulting sei/sei-chain:mock-<sha> image was being built without the mock_balances tag — a regular build just labeled as mock.

Change

One-line rename in .github/workflows/ecr.yml:

-            SEI_CHAIN_BUILD_TAGS=mock_balances
+            GO_BUILD_TAGS=mock_balances

No Dockerfile change; GO_BUILD_TAGS is the name the builder has always read. Confirmed via git log -S SEI_CHAIN_BUILD_TAGS: this workflow was introduced (Jan 8 2026) already broken — the Dockerfile has used GO_BUILD_TAGS since Dec 12 2025; the names never aligned in any commit.

How this was discovered

During the v6-5-run-3 soak on our k8s cluster, nodes pulling the ECR mock-<sha> image didn't exhibit the expected mock-balances behavior. I worked around it at the time by building a mock image locally and pushing it to my personal registry; this PR is the proper fix so the CI-produced image is actually a mock build.

Behavior change after merge (heads-up for downstream consumers)

Several platform-side consumers pull sei/sei-chain:mock-<sha> by tag name:

• autobake/README.md / .github/workflows/k8s_autobake.yml
• gprusak/README.md
• clusters/dev/release-6-4/kustomization.yaml
• clusters/dev/release-6-3/kustomization.yaml

After this merge, new mock-<sha> tags will actually carry mock_balances behavior for the first time since the workflow was introduced. Existing images already pulled into clusters are unchanged; this only affects future ECR builds. The release-6-3 / release-6-4 dev clusters and autobake runs will start exhibiting real mock semantics on their next image roll — that's the intended behavior, calling it out so no one is surprised.

Companion PR: sei-protocol/platform#141 fixes the same bug in ecr-seid-musl.yml.

Test plan

• Dockerfile ARG audit: GO_BUILD_TAGS is the only build-tags ARG; no other workflow or script references SEI_CHAIN_BUILD_TAGS.
• Git history confirms names never matched historically — safe rename, no legitimate consumer of the old name.
• Post-merge: verify seid version on the next CI-produced mock-<sha> image reports netgo ledger mock_balances in BuildTags (not just netgo ledger).

🤖 Generated with Claude Code

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Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Apr 22, 2026, 9:11 PM