app/src-tauri/src/commands/migration_commands.rs

@@ -73,6 +73,25 @@ use crate::AppState;
 /// Report how far behind the current base image a project's container is, and
 /// what migrating it would actually carry across.
 ///
+/// Choose the recorded lineage from the two places it can be written, most
+/// authoritative first: the live container's label, then the snapshot image's.
+///
+/// **An empty label is absence, not an answer.** `create_container` always
+/// writes `triple-c.base-image-id`, even when the value is unknown — that is
+/// deliberate, because Docker merges an image's labels into a container's and
+/// an inherited value would otherwise ride a snapshot forever. The consequence
+/// is that `Some("")` is the *common* reading from a container whose lineage
+/// was never established, so treating it as an answer silently skips the
+/// snapshot, which may well have recorded a real one.
+fn pick_recorded_lineage(
+    from_container: Option<String>,
+    from_snapshot: Option<String>,
+) -> Option<String> {
+    from_container
+        .filter(|v| !v.is_empty())
+        .or_else(|| from_snapshot.filter(|v| !v.is_empty()))
+}
+
 /// Read-only. Runs two filesystem probes (~3 s each) and is therefore meant to
 /// be called on demand, not polled.
 #[tauri::command]
@@ -98,20 +117,24 @@ pub async fn get_container_staleness(
     // Lineage, most authoritative source first: the live container's label,
     // then the snapshot image's. Both are written by `create_container` and
     // propagated onto the snapshot by `docker commit`.
+    // Each source is filtered for emptiness *before* it is allowed to satisfy
+    // the lookup. `create_container` always writes this label, even when the
+    // value is unknown — deliberately, so an inherited image label cannot ride
+    // a snapshot forever — which means the container's copy is very often
+    // `Some("")`. Filtering only the final result let that empty string count
+    // as an answer and skip the snapshot entirely, so a snapshot that *did*
+    // record a lineage was never consulted and the project reported "unknown"
+    // with the information sitting one lookup away.
     let container_id = docker::find_existing_container(&project).await.unwrap_or(None);
-    let recorded = match &container_id {
+    let from_container = match &container_id {
         Some(id) => container_label(id, mig::LABEL_BASE_IMAGE_ID).await,
         None => None,
-    }
-    .or_else(|| None);
-    let recorded = match recorded {
-        Some(v) => Some(v),
-        None => mig::image_labels(&snapshot_image)
-            .await
-            .get(mig::LABEL_BASE_IMAGE_ID)
-            .cloned(),
-    }
-    .filter(|v| !v.is_empty());
+    };
+    let from_snapshot = mig::image_labels(&snapshot_image)
+        .await
+        .get(mig::LABEL_BASE_IMAGE_ID)
+        .cloned();
+    let recorded = pick_recorded_lineage(from_container, from_snapshot);
 
     out.base_image_id = recorded.clone();
     out.known = recorded.is_some();
@@ -1671,6 +1694,32 @@ fn summarize(
 mod tests {
     use super::*;
 
+    #[test]
+    fn an_empty_lineage_label_is_absence_and_falls_through_to_the_snapshot() {
+        let some = |s: &str| Some(s.to_string());
+
+        // The regression: the container always carries the label, so an
+        // unknown lineage reads as `Some("")`. Letting that satisfy the lookup
+        // skipped a snapshot that had recorded the real thing.
+        assert_eq!(
+            pick_recorded_lineage(some(""), some("sha256:base")),
+            some("sha256:base")
+        );
+
+        // Ordinary precedence still holds: the container wins when it has one.
+        assert_eq!(
+            pick_recorded_lineage(some("sha256:container"), some("sha256:snapshot")),
+            some("sha256:container")
+        );
+        assert_eq!(pick_recorded_lineage(None, some("sha256:snap")), some("sha256:snap"));
+
+        // Genuinely unknown stays unknown — "probe instead", never a lineage
+        // invented to make the comparison succeed.
+        assert_eq!(pick_recorded_lineage(None, None), None);
+        assert_eq!(pick_recorded_lineage(some(""), some("")), None);
+        assert_eq!(pick_recorded_lineage(some(""), None), None);
+    }
+
     #[test]
     fn byte_sizes_read_the_way_a_disk_warning_should() {
         assert_eq!(human_bytes(512), "512 B");

app/src/components/projects/home/ContainerMigrationBanner.test.tsx

@@ -127,6 +127,46 @@ describe("ContainerMigrationBanner", () => {
     expect(container).toBeEmptyDOMElement();
   });
 
+  it("speaks up when an unlabelled container could not be probed at all", () => {
+    // The probe is the only signal a container with no lineage label has. If
+    // it fails and the banner stays silent, that is indistinguishable from
+    // "up to date" — the exact reading that let an out-of-date project go
+    // unnoticed indefinitely.
+    renderBanner(
+      migration({
+        staleness: {
+          ...FRESH,
+          known: false,
+          stale: false,
+          probe_error: "output exceeded the inspection limit",
+        },
+        probeSettled: false,
+      }),
+    );
+    expect(
+      screen.getByText(/Container base could not be checked/i),
+    ).toBeInTheDocument();
+    expect(
+      screen.getByText(/output exceeded the inspection limit/i),
+    ).toBeInTheDocument();
+    // And it must not pose as a finding about the container itself.
+    expect(
+      screen.queryByText(/Container is missing things/i),
+    ).not.toBeInTheDocument();
+  });
+
+  it("stays quiet when a labelled container's probe fails but its lineage is current", () => {
+    // `known` means the version comparison already answered the question, so
+    // a failed probe is not grounds to raise anything.
+    const { container } = renderBanner(
+      migration({
+        staleness: { ...FRESH, probe_error: "could not exec in the container" },
+        probeSettled: false,
+      }),
+    );
+    expect(container).toBeEmptyDOMElement();
+  });
+
   it("disables the action and explains why while the container is running", () => {
     renderBanner(migration({ staleness: STALE }), false);
     expect(

app/src/components/projects/home/ContainerMigrationBanner.tsx

@@ -131,7 +131,15 @@ export default function ContainerMigrationBanner({
   const probeFoundGaps =
     !staleness.known &&
     (staleness.missing_features.length > 0 || staleness.missing_paths.length > 0);
-  if (!staleness.stale && !probeFoundGaps) return null;
+
+  // The probe is the *only* signal a container with no lineage label has, so
+  // when it fails there is nothing left to be quiet about. Staying silent here
+  // is indistinguishable from "everything is fine" — and it is the likeliest
+  // outcome for the oldest, largest projects, whose manifests are the ones apt
+  // to exceed the inspection limit. Say that the check did not run instead.
+  const probeUnavailable = !staleness.known && !!staleness.probe_error;
+
+  if (!staleness.stale && !probeFoundGaps && !probeUnavailable) return null;
 
   const snapshot = formatSnapshotDate(staleness.snapshot_created_at);
   const features = joinFeatures(staleness.missing_features);
@@ -139,16 +147,25 @@ export default function ContainerMigrationBanner({
   return (
     <section
       className={`${SHELL} border-[var(--warning)]/40 bg-[var(--warning-muted)]`}
-      aria-label="Container base is out of date"
+      aria-label={
+        probeUnavailable
+          ? "Container base could not be checked"
+          : "Container base is out of date"
+      }
     >
       <div className="flex items-start justify-between gap-3">
         <div className="min-w-0 space-y-1">
           <StatusIndicator
-            tone="error"
+            // A check that could not run is not a finding: it gets the
+            // "unresolved" tone rather than the one that says something is
+            // wrong with the container.
+            tone={probeUnavailable ? "unknown" : "error"}
             label={
               staleness.known
                 ? "Container base is out of date"
-                : "Container is missing things the current base ships"
+                : probeUnavailable
+                  ? "Container base could not be checked"
+                  : "Container is missing things the current base ships"
             }
             className="text-[13px] font-semibold"
           />
@@ -158,7 +175,9 @@ export default function ContainerMigrationBanner({
               ? snapshot
                 ? `Running on a saved image from ${snapshot}.`
                 : "Running on a saved image older than the current base."
-              : "This container predates base-image tracking, so it was probed directly."}
+              : probeUnavailable
+                ? "This container predates base-image tracking, so probing it is the only way to tell whether it is behind — and that did not complete."
+                : "This container predates base-image tracking, so it was probed directly."}
           </p>
 
           {staleness.missing_features.length > 0 && (