diff --git a/.github/workflows/package.yml b/.github/workflows/package.yml
index d47ddb7..475ec9d 100644
--- a/.github/workflows/package.yml
+++ b/.github/workflows/package.yml
@@ -73,6 +73,7 @@ jobs:
       version: ${{ steps.metadata.outputs.version }}
       source_commit: ${{ steps.metadata.outputs.source_commit }}
       release_tag: ${{ steps.metadata.outputs.release_tag }}
+      source_ref: ${{ steps.metadata.outputs.source_ref }}
       source_ref_type: ${{ steps.metadata.outputs.source_ref_type }}
     steps:
       - name: Check out source
@@ -93,19 +94,23 @@ jobs:
         run: |
           version="$(tr -d '\\r\\n' < VERSION)"
           release_tag="$REQUESTED_RELEASE_TAG"
+          source_ref="$GITHUB_REF"
           if [[ -n "$release_tag" ]]; then
             source_ref_type=tag
             source_commit="$(git rev-parse --verify "refs/tags/$release_tag^{}")"
+            source_ref="refs/tags/$release_tag"
           else
             source_ref_type="$GITHUB_REF_TYPE"
             source_commit="$GITHUB_SHA"
             if [[ "$source_ref_type" == tag ]]; then
               release_tag="$GITHUB_REF_NAME"
+              source_ref="refs/tags/$release_tag"
             fi
           fi
           echo "version=$version" >> "$GITHUB_OUTPUT"
           echo "source_commit=$source_commit" >> "$GITHUB_OUTPUT"
           echo "release_tag=$release_tag" >> "$GITHUB_OUTPUT"
+          echo "source_ref=$source_ref" >> "$GITHUB_OUTPUT"
           echo "source_ref_type=$source_ref_type" >> "$GITHUB_OUTPUT"
 
       - name: Validate release ref
@@ -317,7 +322,7 @@ jobs:
 
   publish:
     name: Publish reviewed distribution
-    needs: [build, smoke, provenance]
+    needs: [build, smoke, provenance, attest, verify_attestations]
     if: ${{ (github.event_name == 'push' && github.ref_type == 'tag') || github.event_name == 'workflow_dispatch' }}
     runs-on: ubuntu-latest
     timeout-minutes: 10
@@ -381,9 +386,46 @@ jobs:
           subject-checksums: dist/SHA256SUMS
           sbom-path: dist/SBOM.spdx.json
 
+  verify_attestations:
+    name: Verify reviewed release attestations
+    needs: [build, smoke, provenance, attest]
+    if: ${{ (github.event_name == 'push' && github.ref_type == 'tag') || github.event_name == 'workflow_dispatch' }}
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    permissions:
+      contents: read
+      attestations: read
+    steps:
+      - name: Download reviewed distributions
+        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
+        with:
+          name: base-cli-dist-${{ github.run_id }}
+          path: dist
+
+      - name: Verify artifact provenance and SBOM attestations
+        env:
+          SOURCE_COMMIT: ${{ needs.build.outputs.source_commit }}
+          SOURCE_REF: ${{ needs.build.outputs.source_ref }}
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          set -euo pipefail
+          for asset in dist/*.whl dist/*.tar.gz; do
+            gh attestation verify "$asset" \
+              --repo "$GITHUB_REPOSITORY" \
+              --signer-workflow "github.com/$GITHUB_REPOSITORY/.github/workflows/package.yml" \
+              --source-digest "$SOURCE_COMMIT" \
+              --source-ref "$SOURCE_REF"
+            gh attestation verify "$asset" \
+              --repo "$GITHUB_REPOSITORY" \
+              --signer-workflow "github.com/$GITHUB_REPOSITORY/.github/workflows/package.yml" \
+              --source-digest "$SOURCE_COMMIT" \
+              --source-ref "$SOURCE_REF" \
+              --predicate-type "https://spdx.dev/Document"
+          done
+
   verify_pypi:
     name: Verify published PyPI metadata
-    needs: [build, publish, attest]
+    needs: [build, publish, verify_attestations]
     if: ${{ (github.event_name == 'push' && github.ref_type == 'tag') || (github.event_name == 'workflow_dispatch' && inputs.publish_target == 'pypi' && inputs.release_tag != '') }}
     runs-on: ubuntu-latest
     timeout-minutes: 5
@@ -405,7 +447,7 @@ jobs:
 
   release:
     name: Create GitHub Release
-    needs: [build, smoke, provenance, publish, attest, verify_pypi]
+    needs: [build, smoke, provenance, attest, verify_attestations, publish, verify_pypi]
     if: ${{ (github.event_name == 'push' && github.ref_type == 'tag') || (github.event_name == 'workflow_dispatch' && inputs.publish_target == 'pypi' && inputs.release_tag != '') }}
     runs-on: ubuntu-latest
     timeout-minutes: 10
@@ -442,6 +484,7 @@ jobs:
           SOURCE_REVISION: ${{ needs.build.outputs.source_commit }}
           RELEASE_TAG: ${{ needs.build.outputs.release_tag }}
           SOURCE_COMMIT: ${{ needs.build.outputs.source_commit }}
+          SOURCE_REF: ${{ needs.build.outputs.source_ref }}
         run: |
           set -euo pipefail
           tag="$RELEASE_TAG"
@@ -458,13 +501,13 @@ jobs:
             gh attestation verify "$asset" \
               --repo "$GITHUB_REPOSITORY" \
               --signer-workflow "github.com/$GITHUB_REPOSITORY/.github/workflows/package.yml" \
-              --source-digest "$GITHUB_SHA" \
-              --source-ref "$GITHUB_REF"
+              --source-digest "$SOURCE_COMMIT" \
+              --source-ref "$SOURCE_REF"
             gh attestation verify "$asset" \
               --repo "$GITHUB_REPOSITORY" \
               --signer-workflow "github.com/$GITHUB_REPOSITORY/.github/workflows/package.yml" \
-              --source-digest "$GITHUB_SHA" \
-              --source-ref "$GITHUB_REF" \
+              --source-digest "$SOURCE_COMMIT" \
+              --source-ref "$SOURCE_REF" \
               --predicate-type "https://spdx.dev/Document"
           done
 
diff --git a/tests/test_package_workflow.py b/tests/test_package_workflow.py
index 38dd089..ead90c1 100644
--- a/tests/test_package_workflow.py
+++ b/tests/test_package_workflow.py
@@ -1,5 +1,8 @@
 from __future__ import annotations
 
+import os
+import subprocess
+import tempfile
 from pathlib import Path
 
 import yaml
@@ -18,12 +21,45 @@ def test_package_workflow_can_recover_an_immutable_tag_from_default_branch() ->
     assert "release_tag:" in workflow
     assert "ref: ${{ inputs.release_tag || github.ref }}" in workflow
     assert "source_commit: ${{ steps.metadata.outputs.source_commit }}" in workflow
+    assert "source_ref: ${{ steps.metadata.outputs.source_ref }}" in workflow
     assert "SOURCE_COMMIT: ${{ steps.metadata.outputs.source_commit }}" in workflow
     assert 'git archive "$SOURCE_COMMIT"' in workflow
     assert "Manual PyPI publication requires the release_tag input." in workflow
     assert '--source-commit "$SOURCE_COMMIT"' in workflow
 
 
+def test_package_workflow_resolves_branch_source_ref_for_testpypi_dispatch() -> None:
+    root = Path(__file__).resolve().parents[1]
+    workflow = yaml.safe_load((root / ".github/workflows/package.yml").read_text(encoding="utf-8"))
+    metadata_step = next(step for step in workflow["jobs"]["build"]["steps"] if step.get("id") == "metadata")
+
+    with tempfile.TemporaryDirectory() as directory:
+        output_path = Path(directory) / "github-output"
+        environment = os.environ.copy()
+        environment.update(
+            {
+                "GITHUB_REF": "refs/heads/testpypi-rehearsal",
+                "GITHUB_REF_TYPE": "branch",
+                "GITHUB_SHA": "a" * 40,
+                "GITHUB_OUTPUT": str(output_path),
+                "REQUESTED_RELEASE_TAG": "",
+            }
+        )
+        subprocess.run(
+            ["bash", "-euo", "pipefail", "-c", metadata_step["run"]],
+            cwd=root,
+            env=environment,
+            check=True,
+            capture_output=True,
+            text=True,
+        )
+        outputs = dict(line.split("=", 1) for line in output_path.read_text(encoding="utf-8").splitlines())
+
+    assert outputs["source_ref"] == "refs/heads/testpypi-rehearsal"
+    assert outputs["source_ref_type"] == "branch"
+    assert outputs["release_tag"] == ""
+
+
 def test_package_workflow_uses_a_published_pypi_publisher_image_tag() -> None:
     workflow = (Path(__file__).resolve().parents[1] / ".github/workflows/package.yml").read_text(encoding="utf-8")
 
@@ -40,8 +76,8 @@ def test_package_workflow_does_not_replace_published_release_assets() -> None:
     assert "refusing to replace immutable release assets" in verifier
     assert "gh release download" in workflow
     assert "gh attestation verify" in workflow
-    assert '--source-digest "$GITHUB_SHA"' in workflow
-    assert '--source-ref "$GITHUB_REF"' in workflow
+    assert '--source-digest "$SOURCE_COMMIT"' in workflow
+    assert '--source-ref "$SOURCE_REF"' in workflow
     assert '--source-commit "$source_commit"' in workflow
     assert "--clobber" not in workflow
 
@@ -63,7 +99,7 @@ def test_package_workflow_gates_tag_publication_on_release_documentation() -> No
     assert "python scripts/validate_release_docs.py" in workflow
     assert "scripts/verify_pypi_metadata.py" in workflow
     assert "name: Verify published PyPI metadata" in workflow
-    assert "needs: [build, smoke, provenance, publish, attest, verify_pypi]" in workflow
+    assert "needs: [build, smoke, provenance, attest, verify_attestations, publish, verify_pypi]" in workflow
 
 
 def test_package_workflow_gates_writes_on_release_provenance() -> None:
@@ -73,6 +109,26 @@ def test_package_workflow_gates_writes_on_release_provenance() -> None:
     assert "name: Verify reviewed release provenance" in workflow
     assert 'git fetch --no-tags --prune origin "refs/heads/main:refs/remotes/origin/main"' in workflow
     assert "python scripts/validate_release_provenance.py" in workflow
-    assert jobs["publish"]["needs"] == ["build", "smoke", "provenance"]
+    assert jobs["publish"]["needs"] == ["build", "smoke", "provenance", "attest", "verify_attestations"]
     assert jobs["attest"]["needs"] == ["build", "smoke", "provenance"]
-    assert jobs["release"]["needs"] == ["build", "smoke", "provenance", "publish", "attest", "verify_pypi"]
+    assert jobs["release"]["needs"] == [
+        "build",
+        "smoke",
+        "provenance",
+        "attest",
+        "verify_attestations",
+        "publish",
+        "verify_pypi",
+    ]
+
+
+def test_package_workflow_verifies_attestations_before_publication() -> None:
+    workflow = (Path(__file__).resolve().parents[1] / ".github/workflows/package.yml").read_text(encoding="utf-8")
+    jobs = yaml.safe_load(workflow)["jobs"]
+
+    assert jobs["publish"]["needs"] == ["build", "smoke", "provenance", "attest", "verify_attestations"]
+    assert jobs["verify_attestations"]["needs"] == ["build", "smoke", "provenance", "attest"]
+    assert '--source-digest "$SOURCE_COMMIT"' in workflow
+    assert "SOURCE_REF: ${{ needs.build.outputs.source_ref }}" in workflow
+    assert '--source-ref "$SOURCE_REF"' in workflow
+    assert '--source-ref "refs/tags/$RELEASE_TAG"' not in workflow