diff --git a/action.yml b/action.yml
index f72e9877..436efbd6 100644
--- a/action.yml
+++ b/action.yml
@@ -193,6 +193,14 @@ runs:
       with:
         bun-version: 1.3.14
         token: ${{ inputs.github_token || github.token }}
+        # Disable setup-bun's cache. The upstream save step uses a deterministic
+        # key (Bun version) and isn't ref-aware: on every second-and-subsequent
+        # run against the same PR ref the GitHub cache API rejects the duplicate
+        # key+ref with a 409 (HTML body), and @actions/cache treats the unparsable
+        # response as transient and burns ~20-30s on 5 retries before warning.
+        # The 35 MB Bun binary downloads in 2-3s, so disabling the cache is a net
+        # wallclock win and removes the noisy warning. See issue #1252.
+        no-cache: true
 
     - name: Setup Custom Bun Path
       if: inputs.path_to_bun_executable != ''
diff --git a/base-action/action.yml b/base-action/action.yml
index 9b867bb7..47407017 100644
--- a/base-action/action.yml
+++ b/base-action/action.yml
@@ -121,6 +121,8 @@ runs:
       uses: oven-sh/setup-bun@0c5077e51419868618aeaa5fe8019c62421857d6 # https://github.com/oven-sh/setup-bun/releases/tag/v2.2.0
       with:
         bun-version: 1.3.14
+        # Disable setup-bun's cache. See action.yml for details and issue #1252.
+        no-cache: true
 
     - name: Setup Custom Bun Path
       if: inputs.path_to_bun_executable != ''