diff --git a/.github/workflows/rainix-copy-artifacts.yaml b/.github/workflows/rainix-copy-artifacts.yaml
index 1157a67..0f8c1d6 100644
--- a/.github/workflows/rainix-copy-artifacts.yaml
+++ b/.github/workflows/rainix-copy-artifacts.yaml
@@ -22,8 +22,9 @@ jobs:
         if: hashFiles('soldeer.lock') != ''
         run: nix develop github:rainlanguage/rainix/${{ env.RAINIX_SHA }}#sol-shell -c forge soldeer install
       # Currency-check every committed generated artifact by re-running each
-      # consumer-provided codegen step. The final git diff fails if any
-      # committed file has drifted from its source. The build-meta.sh hook is
+      # consumer-provided codegen step. The final currency check fails if any
+      # committed file has drifted from its source, or if regeneration wrote a
+      # file the repo does not track. The build-meta.sh hook is
       # consumer-supplied because rain meta build's invocation (input/output
       # filenames, meta type) varies per repo.
       - name: Regenerate meta artifacts
@@ -55,9 +56,17 @@ jobs:
         run: ./script/build.sh
       - name: Format (so generated artifacts match committed style)
         run: nix develop github:rainlanguage/rainix/${{ env.RAINIX_SHA }}#sol-shell -c forge fmt
+      # Staging first is what makes this a whole-tree comparison. `git diff`
+      # alone reads tracked content only, so a regeneration that writes to a
+      # path nothing has committed yet — a renamed contract, an added artifact —
+      # is invisible to it, while the artifact it supersedes stays committed and
+      # frozen at whatever the consumer's `src/**` still imports. `git add --all`
+      # respects .gitignore, so out/, cache/ and dependencies/ contribute
+      # nothing, and every addition, deletion and edit reaches the diff.
       - name: Assert committed artifacts match freshly built
         run: |
-          if ! git diff --exit-code; then
-            echo "::error::Committed artifacts are stale. Regenerate (script/build-meta.sh, script/Build.sol, script/CopyArtifacts.sol, script/build.sh, forge fmt) and commit."
+          git add --all
+          if ! git diff --cached --exit-code; then
+            echo "::error::Committed artifacts are stale, or regeneration wrote a file that is not committed. Regenerate (script/build-meta.sh, script/Build.sol, script/CopyArtifacts.sol, script/build.sh, forge fmt) and commit."
             exit 1
           fi
diff --git a/flake.nix b/flake.nix
index c390c0b..c89f1c3 100644
--- a/flake.nix
+++ b/flake.nix
@@ -448,6 +448,7 @@
             bats test/bats/devshell/default/prettier-bundle.test.bats
             bats test/bats/action/rpc-preflight.test.bats
             bats test/bats/action/prompt-cap.test.bats
+            bats test/bats/workflow/copy-artifacts-currency.test.bats
             bats test/bats/task/skip-simulation.test.bats
             bats test/bats/task/subgraph-build.test.bats
             bats test/bats/task/subgraph-deploy-version.test.bats
diff --git a/test/bats/workflow/copy-artifacts-currency.test.bats b/test/bats/workflow/copy-artifacts-currency.test.bats
new file mode 100644
index 0000000..4f76dae
--- /dev/null
+++ b/test/bats/workflow/copy-artifacts-currency.test.bats
@@ -0,0 +1,76 @@
+setup() {
+  repo_root="$BATS_TEST_DIRNAME/../../.."
+  workflow="$repo_root/.github/workflows/rainix-copy-artifacts.yaml"
+  assert_script="$(yq -r '.jobs["copy-artifacts"].steps[] | select(.name == "Assert committed artifacts match freshly built") | .run' "$workflow")"
+
+  consumer="$(mktemp -d)"
+  # A consumer checkout is the only git state the step reads, so the fixture
+  # owns its whole git environment: no ambient config, no ambient excludes.
+  export GIT_CONFIG_NOSYSTEM=1
+  export HOME="$consumer"
+  cd "$consumer" || return 1
+  git init -q -b main .
+  git config user.email rainix@example.com
+  git config user.name rainix
+  printf 'out/\ncache/\ndependencies/\n' >.gitignore
+  mkdir -p src/generated
+  printf 'library CodeGennable {}\n' >src/generated/CodeGennable.sol
+  git add --all
+  git commit -qm 'committed artifacts'
+}
+
+teardown() {
+  cd / || return 0
+  rm -rf "$consumer"
+}
+
+run_assert() {
+  bash -c "$assert_script"
+}
+
+@test "a checkout whose regeneration changed nothing passes" {
+  run run_assert
+
+  [ "$status" -eq 0 ]
+}
+
+@test "a committed artifact whose content drifted fails" {
+  printf 'library CodeGennable { uint256 constant X = 1; }\n' >src/generated/CodeGennable.sol
+
+  run run_assert
+
+  [ "$status" -eq 1 ]
+  [[ "$output" == *"CodeGennable.sol"* ]]
+  [[ "$output" == *"::error::"* ]]
+}
+
+@test "an artifact regenerated under a new name, leaving the old one committed, fails" {
+  printf 'library CodeGennableRenamed {}\n' >src/generated/CodeGennableRenamed.sol
+
+  run run_assert
+
+  [ "$status" -eq 1 ]
+  [[ "$output" == *"CodeGennableRenamed.sol"* ]]
+  [[ "$output" == *"::error::"* ]]
+}
+
+@test "a committed artifact that regeneration no longer emits fails" {
+  rm src/generated/CodeGennable.sol
+
+  run run_assert
+
+  [ "$status" -eq 1 ]
+  [[ "$output" == *"CodeGennable.sol"* ]]
+  [[ "$output" == *"::error::"* ]]
+}
+
+@test "build output the consumer gitignores passes" {
+  mkdir -p out cache dependencies
+  printf '{}\n' >out/CodeGennable.json
+  printf '{}\n' >cache/solidity-files-cache.json
+  printf 'library Dep {}\n' >dependencies/Dep.sol
+
+  run run_assert
+
+  [ "$status" -eq 0 ]
+}