fix(observation): admit bounded LAB chunk coverage

apps/control-station/src/components/RerunViewport.tsx

@@ -46,6 +46,8 @@ export interface RerunPlaybackState {
   playing: boolean;
   /** Latest session-time value currently available to the browser receiver. */
   bufferedEndNs: number | null;
+  /** Declared first session-time value, when the archive descriptor provides it. */
+  expectedStartNs: number | null;
   /** Declared final session-time value, when the archive descriptor provides it. */
   expectedEndNs: number | null;
   /** Download progress in the closed interval 0..1, or null without a valid expectation. */
@@ -182,6 +184,7 @@ export function createRecordedOpenWatchdog<T>({
 
 export interface RecordedPlaybackBufferState {
   bufferedEndNs: number | null;
+  expectedStartNs: number | null;
   expectedEndNs: number | null;
   bufferProgress: number | null;
   fullyBuffered: boolean;
@@ -214,6 +217,7 @@ export function recordedPlaybackBufferState(
   if (expectedTimelineEndSeconds === undefined) {
     return {
       bufferedEndNs,
+      expectedStartNs: null,
       expectedEndNs: null,
       bufferProgress: null,
       fullyBuffered: usableRange !== null,
@@ -222,6 +226,7 @@ export function recordedPlaybackBufferState(
   if (!Number.isFinite(expectedTimelineEndSeconds) || expectedTimelineEndSeconds < 0) {
     return {
       bufferedEndNs,
+      expectedStartNs: null,
       expectedEndNs: null,
       bufferProgress: null,
       fullyBuffered: false,
@@ -240,21 +245,32 @@ export function recordedPlaybackBufferState(
   ) {
     return {
       bufferedEndNs,
+      expectedStartNs: null,
       expectedEndNs: null,
       bufferProgress: null,
       fullyBuffered: false,
     };
   }
+  // Rerun split preserves whole boundary chunks so that all generated splits
+  // still sum exactly to the source recording. A verified bounded artifact can
+  // therefore begin slightly before its declared operator window. Admission
+  // requires coverage of the declared window, not byte-chunk boundary equality.
   const fullyBuffered = usableRange !== null &&
-    Math.abs(usableRange.min - expectedStartNs) <= BUFFER_END_TOLERANCE_NS &&
-    Math.abs(usableRange.max - expectedEndNs) <= BUFFER_END_TOLERANCE_NS;
+    usableRange.min <= expectedStartNs + BUFFER_END_TOLERANCE_NS &&
+    usableRange.max >= expectedEndNs - BUFFER_END_TOLERANCE_NS;
   const expectedDurationNs = expectedEndNs - expectedStartNs;
   const bufferProgress = bufferedEndNs === null
     ? 0
     : expectedDurationNs <= 0
       ? (fullyBuffered ? 1 : 0)
       : Math.min(1, Math.max(0, (bufferedEndNs - expectedStartNs) / expectedDurationNs));
-  return { bufferedEndNs, expectedEndNs, bufferProgress, fullyBuffered };
+  return {
+    bufferedEndNs,
+    expectedStartNs,
+    expectedEndNs,
+    bufferProgress,
+    fullyBuffered,
+  };
 }
 
 /** A recorded viewport is publishable only after its declared range is complete. */
@@ -272,9 +288,19 @@ export function recordedPlaybackRangeWhenReady(
   buffer: RecordedPlaybackBufferState,
   artifactVerified: boolean,
 ): { min: number; max: number } | null {
-  return artifactVerified && buffer.fullyBuffered && isUsableRecordedPlaybackRange(rangeNs)
-    ? rangeNs
-    : null;
+  if (
+    !artifactVerified ||
+    !buffer.fullyBuffered ||
+    !isUsableRecordedPlaybackRange(rangeNs)
+  ) return null;
+  return {
+    min: buffer.expectedStartNs === null
+      ? rangeNs.min
+      : Math.max(rangeNs.min, buffer.expectedStartNs),
+    max: buffer.expectedEndNs === null
+      ? rangeNs.max
+      : Math.min(rangeNs.max, buffer.expectedEndNs),
+  };
 }
 
 /** Do not mount host timeline controls while a recorded generation is partial. */
@@ -1076,6 +1102,7 @@ export function RerunViewport({
               ...(followLive
                 ? {
                     bufferedEndNs: rangeNs?.max ?? null,
+                    expectedStartNs: null,
                     expectedEndNs: null,
                     bufferProgress: null,
                     fullyBuffered: true,
@@ -1096,7 +1123,7 @@ export function RerunViewport({
                 emitPlayback({ playing });
               },
               jumpToEnd: () => {
-                const range = viewer.get_time_range(event.recording_id, timeline);
+                const range = playbackState?.rangeNs;
                 if (!range) return;
                 viewer.set_current_time(event.recording_id, timeline, range.max);
                 emitPlayback({ rangeNs: range, currentNs: range.max, playing: false });
@@ -1151,7 +1178,9 @@ export function RerunViewport({
                     viewer.set_playing(event.recording_id, true);
                   },
                   initialPlaybackStartSeconds === undefined
-                    ? undefined
+                    ? expectedTimelineStartSeconds === undefined
+                      ? undefined
+                      : expectedTimelineStartSeconds * 1_000_000_000
                     : initialPlaybackStartSeconds * 1_000_000_000,
                 );
                 if (autoplayStarted) {
@@ -1167,6 +1196,7 @@ export function RerunViewport({
                 ...(followLive
                   ? {
                       bufferedEndNs: rangeNs?.max ?? null,
+                      expectedStartNs: null,
                       expectedEndNs: null,
                       bufferProgress: null,
                       fullyBuffered: true,

apps/control-station/test/observationSessions.test.mjs

@@ -133,6 +133,7 @@ test("session catalog decodes canonical snake_case into a path-free camelCase mo
     durationSeconds: 1_450.744,
     replayable: true,
     preparation: null,
+    lab: null,
   }]);
   assert.equal("raw_capture" in catalog.items[0], false);
   assert.equal("path" in catalog.items[0], false);

apps/control-station/test/rerunViewportProgressivePlayback.test.mjs

@@ -42,6 +42,7 @@ test("a first frame reports buffer telemetry but is not ready for presentation",
   const firstFrame = recordedPlaybackBufferState({ min: 0, max: 0 }, 20);
   assert.deepEqual(firstFrame, {
     bufferedEndNs: 0,
+    expectedStartNs: 0,
     expectedEndNs: 20_000_000_000,
     bufferProgress: 0,
     fullyBuffered: false,
@@ -58,6 +59,7 @@ test("host timeline remains unmounted until the verified recording is fully read
     currentNs: 0,
     playing: false,
     bufferedEndNs: 5,
+    expectedStartNs: 0,
     expectedEndNs: 10,
     bufferProgress: 0.5,
     fullyBuffered: false,
@@ -77,6 +79,7 @@ test("host timeline remains unmounted until the verified recording is fully read
 test("buffer progress grows independently and preserves the full-buffer tolerance", () => {
   assert.deepEqual(recordedPlaybackBufferState({ min: 0, max: 5_000_000_000 }, 20), {
     bufferedEndNs: 5_000_000_000,
+    expectedStartNs: 0,
     expectedEndNs: 20_000_000_000,
     bufferProgress: 0.25,
     fullyBuffered: false,
@@ -97,14 +100,37 @@ test("buffer progress grows independently and preserves the full-buffer toleranc
     { min: 0, max: 19_999_500_000 },
   );
 
-  const wrongDeclaredStart = recordedPlaybackBufferState(
+  const missingDeclaredStart = recordedPlaybackBufferState(
     { min: 5_000_000_000, max: 20_000_000_000 },
     20,
     0,
   );
-  assert.equal(wrongDeclaredStart.bufferProgress, 1);
-  assert.equal(wrongDeclaredStart.fullyBuffered, false);
-  assert.equal(isRecordedPlaybackReady(true, true, wrongDeclaredStart), false);
+  assert.equal(missingDeclaredStart.bufferProgress, 1);
+  assert.equal(missingDeclaredStart.fullyBuffered, false);
+  assert.equal(isRecordedPlaybackReady(true, true, missingDeclaredStart), false);
+});
+
+test("a verified split boundary spill covers and clamps the declared LAB window", () => {
+  const actualRange = {
+    min: 34_756_228_209,
+    max: 95_383_857_292,
+  };
+  const buffer = recordedPlaybackBufferState(
+    actualRange,
+    95.383857292,
+    35.421857292,
+  );
+
+  assert.equal(buffer.bufferProgress, 1);
+  assert.equal(buffer.fullyBuffered, true);
+  assert.equal(isRecordedPlaybackReady(true, true, buffer), true);
+  assert.deepEqual(
+    recordedPlaybackRangeWhenReady(actualRange, buffer, true),
+    {
+      min: 35_421_857_292,
+      max: 95_383_857_292,
+    },
+  );
 });
 
 test("recorded autoplay waits for the full range and then runs exactly once", () => {