diff --git a/projects/pathway-browser/src/app/analysis-summary/summary-stream.spec.ts b/projects/pathway-browser/src/app/analysis-summary/summary-stream.spec.ts
index af59ae53..9d38ec9e 100644
--- a/projects/pathway-browser/src/app/analysis-summary/summary-stream.spec.ts
+++ b/projects/pathway-browser/src/app/analysis-summary/summary-stream.spec.ts
@@ -43,7 +43,16 @@ describe('the start event', () => {
     expect(event).toMatchObject({ start: { analysisType: null } });
   });
 
-  it('takes the release as the string the wire sends', () => {
+  it('takes the release as an int, which is what the field is becoming', () => {
+    // The service is changing this from a string to an int to match
+    // `/api/answer`, which always sent one. Both spellings are accepted so that
+    // neither side of that change breaks the panel.
+    expect(parseFrame(frame('start', { release: 97 }))).toMatchObject({
+      start: { release: 97 },
+    });
+  });
+
+  it('still takes the string form the field had before that', () => {
     // `"97"`, not `97`. Requiring a number here silently nulled every release,
     // and the field is what tells one release's cached summary from another's.
     expect(parseFrame(frame('start', { release: '97' }))).toMatchObject({
@@ -57,6 +66,16 @@ describe('the start event', () => {
     });
   });
 
+  it('never turns an absent release into release 0', () => {
+    // `Number(null)`, `Number('')` and `Number(false)` are all 0, and 0 is a
+    // number that caches and compares perfectly happily while naming no release
+    // that has ever existed.
+    for (const release of [null, '', '   ', false, []]) {
+      expect(parseFrame(frame('start', { release }))).toMatchObject({ start: { release: null } });
+    }
+    expect(parseFrame(frame('start', {}))).toMatchObject({ start: { release: null } });
+  });
+
   it('treats a missing cached flag as not cached', () => {
     expect(parseFrame(frame('start', {}))).toMatchObject({ start: { cached: false } });
   });
diff --git a/projects/pathway-browser/src/app/analysis-summary/summary-stream.ts b/projects/pathway-browser/src/app/analysis-summary/summary-stream.ts
index ce463a7a..354f0b92 100644
--- a/projects/pathway-browser/src/app/analysis-summary/summary-stream.ts
+++ b/projects/pathway-browser/src/app/analysis-summary/summary-stream.ts
@@ -125,6 +125,19 @@ function asReason(value: unknown): RefusalReason | null {
 }
 
 /** Turns one complete SSE frame into an event, or null if it is not one we act on. */
+/**
+ * The release number, from either spelling, or null.
+ *
+ * Only a number or a non-empty string can be one, and it must be positive: the
+ * field's whole job is telling one release's cached summary from another's, and
+ * a 0 conjured out of `null` would do that job wrongly rather than not at all.
+ */
+function releaseOf(value: unknown): number | null {
+  if (typeof value !== 'number' && (typeof value !== 'string' || value.trim() === '')) return null;
+  const release = Number(value);
+  return Number.isFinite(release) && release > 0 ? release : null;
+}
+
 export function parseFrame(frame: string): SummaryEvent | null {
   let name = '';
   const dataLines: string[] = [];
@@ -151,10 +164,16 @@ export function parseFrame(frame: string): SummaryEvent | null {
       return {
         kind: 'start',
         start: {
-          // A string on the wire ("97"), not a number. Coerced rather than
-          // required, because what this is for is telling one release's cache
-          // from another's, not arithmetic.
-          release: Number.isFinite(Number(data['release'])) ? Number(data['release']) : null,
+          // Accepts both spellings on purpose. It arrived as the string "97"
+          // while `/api/answer` sent an int for the same field; the service is
+          // making it an int here too, and a parser that accepted only one of
+          // them would have broken on one side of that change or the other.
+          //
+          // Not a bare `Number()`: `Number(null)`, `Number('')` and
+          // `Number(false)` are all 0, so an absent or empty release would
+          // become release 0 -- a number that compares, sorts and caches
+          // perfectly well while naming no release that exists.
+          release: releaseOf(data['release']),
           analysisType:
             typeof data['analysis_type'] === 'string' && TYPES.includes(data['analysis_type'])
               ? (data['analysis_type'] as AnalysisType)
diff --git a/projects/pathway-browser/src/app/analysis-summary/summary.service.ts b/projects/pathway-browser/src/app/analysis-summary/summary.service.ts
index 367497ff..8f3db883 100644
--- a/projects/pathway-browser/src/app/analysis-summary/summary.service.ts
+++ b/projects/pathway-browser/src/app/analysis-summary/summary.service.ts
@@ -106,7 +106,6 @@ export class SummaryService {
    */
   readonly expired = computed(() => this._state() === 'gone');
 
-  private release: number | null = null;
   private readonly cache = new Map<string, Cached>();
   private inFlight: AbortController | null = null;
   /** What to ask again for once a challenge is solved. */
@@ -302,7 +301,12 @@ export class SummaryService {
         switch (event.kind) {
           case 'start':
             this._started.set(true);
-            this.release = event.start.release;
+            // `start.release` is deliberately not kept. It was held in a field
+            // nothing ever read, which the dead-code gate cannot see because a
+            // private field is not an export. The cache key does not use it --
+            // this cache lives in one page's memory, and a release during a
+            // session would replace the process holding it -- so storing it
+            // only invited a later reader to trust a value nobody maintains.
             this._analysisType.set(event.start.analysisType);
             this._applied.set(event.start.disclosure);
             break;