diff --git a/.github/scripts/tests/test_release_workflows.py b/.github/scripts/tests/test_release_workflows.py
index b80a2b248..96be8e255 100644
--- a/.github/scripts/tests/test_release_workflows.py
+++ b/.github/scripts/tests/test_release_workflows.py
@@ -154,3 +154,25 @@ def test_reusable_release_executors_have_no_implicit_inputs() -> None:
 def test_registry_publish_authenticates_iii_installer() -> None:
     body = (WORKFLOWS / "_publish-registry.yml").read_text()
     assert "GITHUB_TOKEN: ${{ github.token }}" in body
+
+
+def test_rust_binary_cache_is_keyed_by_frontend_bundle_digest() -> None:
+    jobs = workflow(WORKFLOWS / "_rust-binary.yml")["jobs"]
+    web_build = jobs["web-build"]
+    assert web_build["outputs"]["frontend_digest"] == "${{ steps.stage.outputs.frontend_digest }}"
+    assert web_build["outputs"]["frontends"] == "${{ steps.dirs.outputs.frontends }}"
+
+    stage = next(step for step in web_build["steps"] if step.get("name") == "Stage frontend bundles")
+    assert stage["id"] == "stage"
+    assert "frontend_digest=$digest" in stage["run"]
+    assert "git hash-object" in stage["run"]
+
+    build_steps = jobs["build"]["steps"]
+    cache = next(step for step in build_steps if step.get("uses") == "Swatinem/rust-cache@v2")
+    assert "needs.web-build.outputs.frontend_digest" in cache["with"]["key"]
+
+    verify = next(step for step in build_steps if step.get("name") == "Verify frontend bundle digest")
+    assert verify["if"] == "inputs.web_bundle"
+    assert verify["env"]["EXPECTED_DIGEST"] == "${{ needs.web-build.outputs.frontend_digest }}"
+    assert "git hash-object" in verify["run"]
+    assert '[[ "$actual" == "$EXPECTED_DIGEST" ]]' in verify["run"]
diff --git a/.github/workflows/_rust-binary.yml b/.github/workflows/_rust-binary.yml
index 511a66a53..4d1d4f127 100644
--- a/.github/workflows/_rust-binary.yml
+++ b/.github/workflows/_rust-binary.yml
@@ -88,6 +88,9 @@ jobs:
     needs: [matrix]
     if: inputs.web_bundle
     runs-on: ubuntu-latest
+    outputs:
+      frontend_digest: ${{ steps.stage.outputs.frontend_digest }}
+      frontends: ${{ steps.dirs.outputs.frontends }}
     steps:
       - uses: actions/checkout@v5
         with:
@@ -163,6 +166,7 @@ jobs:
           done
 
       - name: Stage frontend bundles
+        id: stage
         env:
           FRONTENDS: ${{ steps.dirs.outputs.frontends }}
         run: |
@@ -177,6 +181,19 @@ jobs:
             mkdir -p "$stage/$bundle"
             cp -a "$bundle/dist" "$stage/$bundle/"
           done
+          digest=$(
+            for bundle in "${bundles[@]}"; do
+              find "$bundle/dist" -type f -print
+            done \
+              | LC_ALL=C sort \
+              | while IFS= read -r file; do
+                  printf '%s  %s\n' "$(git hash-object "$file")" "$file"
+                done \
+              | git hash-object --stdin
+          )
+          [[ "$digest" =~ ^[0-9a-f]{40}$ ]]
+          echo "frontend_digest=$digest" >> "$GITHUB_OUTPUT"
+          echo "::notice::frontend bundle digest: $digest"
 
       - name: Upload frontend bundles
         uses: actions/upload-artifact@v6
@@ -245,7 +262,10 @@ jobs:
       - name: Cache cargo registry & build
         uses: Swatinem/rust-cache@v2
         with:
-          key: ${{ inputs.bin_name }}-${{ matrix.target }}
+          # Cargo caches compiled include_str!/rust-embed output. Key UI
+          # releases by the generated bytes so a new dist/ can never restore
+          # a worker artifact that still embeds the previous bundle.
+          key: ${{ inputs.bin_name }}-${{ matrix.target }}${{ inputs.web_bundle && format('-frontend-{0}', needs.web-build.outputs.frontend_digest) || '' }}
           # Without this, rust-cache defaults to the repo root, where there is no
           # Cargo.toml — its `cargo metadata` exits 101 and the cache is never
           # found or saved, so every build of every target ships cold.
@@ -274,6 +294,28 @@ jobs:
           # any path-dependency crates with their own ui/dist).
           path: ./
 
+      - name: Verify frontend bundle digest
+        if: inputs.web_bundle
+        shell: bash
+        env:
+          EXPECTED_DIGEST: ${{ needs.web-build.outputs.frontend_digest }}
+          FRONTENDS: ${{ needs.web-build.outputs.frontends }}
+        run: |
+          set -euo pipefail
+          IFS=, read -ra bundles <<< "$FRONTENDS"
+          actual=$(
+            for bundle in "${bundles[@]}"; do
+              test -d "$bundle/dist"
+              find "$bundle/dist" -type f -print
+            done \
+              | LC_ALL=C sort \
+              | while IFS= read -r file; do
+                  printf '%s  %s\n' "$(git hash-object "$file")" "$file"
+                done \
+              | git hash-object --stdin
+          )
+          [[ "$actual" == "$EXPECTED_DIGEST" ]]
+
       - name: Build and upload binary
         uses: taiki-e/upload-rust-binary-action@v1
         env: