diff --git a/pkg/cli/update_container_pins.go b/pkg/cli/update_container_pins.go
index 7fc35c29fe6..1662c20c2ec 100644
--- a/pkg/cli/update_container_pins.go
+++ b/pkg/cli/update_container_pins.go
@@ -91,12 +91,17 @@ func UpdateContainerPins(ctx context.Context, workflowDir string, verbose bool)
 		}
 	}
 
-	// Build a set of images currently referenced in the compiled lock files so
-	// that stale entries (e.g. superseded AWF versions) can be pruned.
+	// Build a set of base image tags (without @sha256: digest suffix) currently
+	// referenced in the compiled lock files so that stale entries (e.g. superseded
+	// AWF versions) can be pruned. Lock files that were previously compiled may
+	// already embed pinned references (image:tag@sha256:...), so we strip the
+	// digest before comparing against container pin keys, which always use the
+	// base tag as the key.
 	imageSet := make(map[string]struct {
 	}, len(images))
 	for _, img := range images {
-		imageSet[img] = struct {
+		base, _, _ := strings.Cut(img, "@sha256:")
+		imageSet[base] = struct {
 		}{}
 	}
 
diff --git a/pkg/cli/update_container_pins_test.go b/pkg/cli/update_container_pins_test.go
index 45a809e87d5..96f94d14e5d 100644
--- a/pkg/cli/update_container_pins_test.go
+++ b/pkg/cli/update_container_pins_test.go
@@ -3,6 +3,7 @@
 package cli
 
 import (
+	"context"
 	"os"
 	"path/filepath"
 	"testing"
@@ -170,6 +171,76 @@ Manifests:
 	}
 }
 
+// TestUpdateContainerPins_PinnedLockFilesPreserveContainerPins verifies that when
+// lock files already contain digest-pinned image references (image:tag@sha256:...),
+// the existing container pins in actions-lock.json are NOT pruned.  This is the
+// regression test for the bug where gh aw update wiped out all container pins
+// because collectImagesFromLockFiles returned digest-suffixed keys that did not
+// match the base-tag keys used in the container pins map.
+//
+// The test calls UpdateContainerPins end-to-end: because all images in the lock
+// file are already digest-pinned, Docker is never invoked.
+func TestUpdateContainerPins_PinnedLockFilesPreserveContainerPins(t *testing.T) {
+	tmpDir := t.TempDir()
+
+	// actions-lock.json has an existing container pin using the base image tag as key.
+	actionsLockDir := filepath.Join(tmpDir, ".github", "aw")
+	require.NoError(t, os.MkdirAll(actionsLockDir, 0755))
+	actionsLockContent := `{
+  "entries": {},
+  "containers": {
+    "ghcr.io/github/gh-aw-firewall/agent:0.27.9": {
+      "image": "ghcr.io/github/gh-aw-firewall/agent:0.27.9",
+      "digest": "sha256:13f522853a688bfe24b04adbbe40b68101e8ef4b6fe0b636068527141bf1c269",
+      "pinned_image": "ghcr.io/github/gh-aw-firewall/agent:0.27.9@sha256:13f522853a688bfe24b04adbbe40b68101e8ef4b6fe0b636068527141bf1c269"
+    }
+  }
+}
+`
+	actionsLockPath := filepath.Join(actionsLockDir, "actions-lock.json")
+	require.NoError(t, os.WriteFile(actionsLockPath, []byte(actionsLockContent), 0644))
+
+	// The compiled lock file already embeds the digest-pinned reference (image:tag@sha256:...).
+	// This is the real-world case after a prior successful gh aw update run.
+	workflowsDir := filepath.Join(tmpDir, ".github", "workflows")
+	require.NoError(t, os.MkdirAll(workflowsDir, 0755))
+	lockFileContent := `name: test
+jobs:
+  setup:
+    steps:
+      - name: Download container images
+        run: bash "${RUNNER_TEMP}/gh-aw/actions/download_docker_images.sh" ghcr.io/github/gh-aw-firewall/agent:0.27.9@sha256:13f522853a688bfe24b04adbbe40b68101e8ef4b6fe0b636068527141bf1c269
+`
+	require.NoError(t, os.WriteFile(filepath.Join(workflowsDir, "my-workflow.lock.yml"), []byte(lockFileContent), 0644))
+
+	// UpdateContainerPins uses "." as the repo root for the action cache, so we
+	// chdir into tmpDir before calling it and restore the original directory after.
+	originalDir, _ := os.Getwd()
+	defer os.Chdir(originalDir) //nolint:errcheck
+	require.NoError(t, os.Chdir(tmpDir))
+
+	// Call UpdateContainerPins end-to-end. Because the lock file image is already
+	// digest-pinned (@sha256:...), Docker is never invoked. The function should
+	// prune zero pins (the bug caused it to prune all of them) and return false
+	// (no new pins were added).
+	added, err := UpdateContainerPins(context.Background(), workflowsDir, false)
+	require.NoError(t, err)
+	assert.False(t, added, "no new pins should be added when all images are already pinned")
+
+	// Reload the cache from disk and confirm the original pin is still present.
+	cache := workflow.NewActionCache(tmpDir)
+	require.NoError(t, cache.Load())
+
+	pin, ok := cache.GetContainerPin("ghcr.io/github/gh-aw-firewall/agent:0.27.9")
+	require.True(t, ok, "container pin should still be present after UpdateContainerPins")
+	assert.Equal(t, "sha256:13f522853a688bfe24b04adbbe40b68101e8ef4b6fe0b636068527141bf1c269", pin.Digest)
+
+	// Verify the on-disk lock file is unchanged.
+	data, err := os.ReadFile(actionsLockPath)
+	require.NoError(t, err)
+	assert.Contains(t, string(data), "ghcr.io/github/gh-aw-firewall/agent:0.27.9", "container pin should still be in actions-lock.json")
+}
+
 // TestUpdateContainerPins_PrunesStaleEntries verifies that UpdateContainerPins
 // removes container pin entries from actions-lock.json that are no longer
 // referenced in the compiled lock files (e.g. superseded AWF versions).