fix(sandbox): don't misreport attestation images as missing in local preflight

src/sandbox/local-sandbox.ts

@@ -112,21 +112,28 @@ export function createLocalSandbox(workspace: WorkspaceStore, opts: LocalSandbox
         preflightDone = undefined;
         throw new Error("SANDBOX_BACKEND=local requires a running Docker daemon (is Docker Desktop running?)");
       }
-      const img = await dexec([
+      // Existence and label are separate probes: images built by buildx with
+      // attestations (the Docker 29 default, and what `qm sandbox publish`
+      // emits) inspect as an OCI index whose Config has no Labels key, which
+      // fails the fingerprint template even though the image is present and
+      // usable. A template failure must not be reported as a missing image.
+      const img = await dexec(["image", "inspect", "-f", "{{.Id}}", image]);
+      if (img.code !== 0) {
+        preflightDone = undefined;
+        throw new Error(`local sandbox image ${image} not found — ${BUILD_HINT}`);
+      }
+      const labeled = await dexec([
         "image",
         "inspect",
         "-f",
-        `{{.Id}} {{if .Config.Labels}}{{index .Config.Labels "${FINGERPRINT_LABEL}"}}{{end}}`,
+        `{{if .Config.Labels}}{{index .Config.Labels "${FINGERPRINT_LABEL}"}}{{end}}`,
         image,
       ]);
-      if (img.code !== 0) {
-        preflightDone = undefined;
-        throw new Error(`local sandbox image ${image} not found — ${BUILD_HINT}`);
-      }
-      const [imageId = "", labeled = ""] = img.stdout.trim().split(/\s+/);
+      const fingerprint = labeled.code === 0 ? labeled.stdout.trim() : "";
+      const [imageId = ""] = img.stdout.trim().split(/\s+/);
       if (!staleWarned) {
         const want = await computeSandboxImageFingerprint(opts.repoRoot ?? process.cwd());
-        if (want && labeled && labeled !== want) {
+        if (want && fingerprint && fingerprint !== want) {
           staleWarned = true;
           console.warn(`[local-sandbox] sandbox image ${image} is stale — ${BUILD_HINT}`);
         }

test/local-sandbox.test.ts

@@ -90,6 +90,28 @@ test("a missing sandbox image fails provision with the build hint", async () =>
   await assert.rejects(sb.provision(rw(scopeId("personal", "U0"))), /not found — run `npm run sandbox:local:build`/);
 });
 
+test("attestation (OCI index) image whose label template fails is usable, not reported missing (#577)", async () => {
+  const fake = installFakeDocker(daemonPort);
+  fake.imageLabelsTemplateError = true;
+  const sb = makeSandbox(fake);
+  const scope = scopeId("personal", "U0");
+  // The regression's signature was a preflight rejection claiming the image is
+  // missing. The preflight must accept the image; environments where the later
+  // daemon-exec prep fails for unrelated reasons (local Windows runs) still
+  // prove the image was found — only the not-found rejection is a failure.
+  try {
+    const h = await sb.provision(rw(scope));
+    assert.equal(h.id, localContainerName(scope));
+    assert.equal(fake.runCount, 1);
+  } catch (error) {
+    assert.doesNotMatch(
+      String(error),
+      /not found — run `npm run sandbox:local:build`/,
+      "image was misreported as missing",
+    );
+  }
+});
+
 test("cold provision creates volume + container, run() execs over the daemon, bytes round-trip", async () => {
   const fake = installFakeDocker(daemonPort);
   const sb = makeSandbox(fake);

test/support/fake-docker.ts

@@ -18,6 +18,9 @@ export interface FakeDocker {
   imageMissing: boolean;
   imageId: string;
   imageFingerprint: string;
+  /** Mimics a buildx attestation image: `{{.Id}}` inspects fine, but the
+   * fingerprint template fails because the OCI index's Config has no Labels key. */
+  imageLabelsTemplateError: boolean;
 }
 
 export function installFakeDocker(daemonPort: number): FakeDocker {
@@ -31,6 +34,7 @@ export function installFakeDocker(daemonPort: number): FakeDocker {
     runCount: 0,
     daemonDown: false,
     imageMissing: false,
+    imageLabelsTemplateError: false,
     imageId: "sha256:image-v1",
     imageFingerprint: "",
     dockerExec: async (args) => exec(args),
@@ -61,7 +65,17 @@ export function installFakeDocker(daemonPort: number): FakeDocker {
         return ok("Docker version fake");
       case "image": {
         if (self.imageMissing) return fail("Error: No such image");
-        return ok(`${self.imageId} ${self.imageFingerprint}`);
+        if (rest[0] === "inspect") {
+          const format = rest[rest.indexOf("-f") + 1] ?? "";
+          if (format === "{{.Id}}") return ok(self.imageId);
+          if (self.imageLabelsTemplateError) {
+            return fail(
+              'template parsing error: template: :1:20: executing "" at <.Config.Labels>: map has no entry for key "Labels"',
+            );
+          }
+          return ok(self.imageFingerprint);
+        }
+        return fail(`unknown image subcommand ${rest.join(" ")}`);
       }
       case "inspect": {
         const name = rest[rest.length - 1]!;