Stop an empty base-image label from silencing the migration notice

A project can be out of date and say nothing about it, in two ways that
compound: the lineage lookup treats "unknown" as an answer, and the
fallback that exists for unknown lineage disappears when its probe fails.

`create_container` always writes triple-c.base-image-id, even when the
value is unknown — deliberately, so an inherited image label cannot ride
a snapshot forever. That makes Some("") the ordinary reading from a
container whose lineage was never established. The lookup filtered for
emptiness only on the final result, so that empty string satisfied the
container branch and skipped the snapshot entirely: a snapshot that had
recorded a real lineage was never consulted, and the project reported
"unknown" with the answer one lookup away. Each source is now filtered
before it can answer, in pick_recorded_lineage, which is a plain function
so the case has a test that fails against the old logic.

A genuinely pre-label project stays unknown, and should: its ancestor is
not knowable, and inventing one would make it look permanently current.
The probe is the intended signal for those — but if the probe failed,
get_container_staleness returned early with nothing populated, the banner
found no gaps and rendered null, and the probe_error it already knew how
to display sat behind a gate that returned before reaching it. Silence
there is indistinguishable from "up to date", and it is likeliest for the
oldest and largest projects, whose manifests are the ones apt to exceed
the inspection limit — one real project measured 6.93 MB against an 8 MB
cap. An unknown-lineage container whose probe failed now says the check
could not be completed, with the reason, under the tone that means
unresolved rather than the one that means something is wrong.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

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 && (