refactor(runtime): derive Session transcripts from RuntimeEvents

apps/desktop/e2e/transcript-scroll-cost.spec.ts

@@ -252,10 +252,14 @@ test('paging back through the whole history keeps the mounted range bounded', as
     const firstBefore = await turns.first().getAttribute('data-turn-id');
     if (firstBefore === 'turn-prompt-rail-1') break;
     // The product asks for history on an upward wheel near the start, so the
-    // gesture that pages is the gesture a reader makes.
-    await wheel(page, cdp, { ticks: 12, deltaY: -120 });
+    // gesture that pages is the gesture a reader makes. How many gestures it
+    // takes is how tall the resident range happens to be, which is not what
+    // this test is about — keep scrolling until the range moves.
     await expect
-      .poll(async () => turns.first().getAttribute('data-turn-id'))
+      .poll(async () => {
+        await wheel(page, cdp, { ticks: 12, deltaY: -120 });
+        return turns.first().getAttribute('data-turn-id');
+      })
       .not.toBe(firstBefore);
     pages += 1;
     mountedMax = Math.max(mountedMax, await turns.count());

apps/desktop/src/main/__tests__/desktop-session-projection.test.ts

@@ -142,7 +142,6 @@ test('projects typed linked Session ids without rewriting opaque tool data', ()
       turnId: 'turn-1',
       status: 'completed',
       parentSessionId: 'child-session',
-      partialOutputRetained: false,
     }).parentSessionId,
     linkedSessionId,
   );

apps/desktop/src/main/__tests__/desktop-transcript-range-store.test.ts

@@ -263,7 +263,6 @@ test('bounds the default active transcript range by Turn identities', async () =
     events: { async *[Symbol.asyncIterator]() {} },
     transcriptBootstrap: {
       throughSequence: messages.length - 1,
-      durableCoverage: 'complete',
       overlayMessageCount: 0,
       durable: bootstrapPage,
       overlay: { ...transcriptPage('older', null, messages.length - 1), source: 'overlay' },
@@ -298,7 +297,6 @@ test('bounds the default active transcript range by presentation bytes', async (
     events: { async *[Symbol.asyncIterator]() {} },
     transcriptBootstrap: {
       throughSequence: messages.length - 1,
-      durableCoverage: 'complete',
       overlayMessageCount: 0,
       durable: bootstrapPage,
       overlay: { ...transcriptPage('older', null, messages.length - 1), source: 'overlay' },
@@ -337,7 +335,6 @@ test('keeps an oversized latest Turn visible after bootstrap eviction', async ()
     events: { async *[Symbol.asyncIterator]() {} },
     transcriptBootstrap: {
       throughSequence: latest.identity,
-      durableCoverage: 'complete',
       overlayMessageCount: 0,
       durable: bootstrapPage,
       overlay: { ...transcriptPage('older', null, latest.identity), source: 'overlay' },
@@ -378,7 +375,6 @@ test('keeps an oversized latest Turn visible before a trailing session note', as
     events: { async *[Symbol.asyncIterator]() {} },
     transcriptBootstrap: {
       throughSequence: trailingNote.identity,
-      durableCoverage: 'complete',
       overlayMessageCount: 0,
       durable: bootstrapPage,
       overlay: {
@@ -440,7 +436,6 @@ test('keeps an oversized latest Turn when returning from history to a trailing s
     events: { async *[Symbol.asyncIterator]() {} },
     transcriptBootstrap: {
       throughSequence: trailingNote.identity,
-      durableCoverage: 'complete',
       overlayMessageCount: 0,
       durable: bootstrapPage,
       overlay: {
@@ -500,7 +495,6 @@ test('keeps a bounded contiguous window while moving between history and the tai
     events: { async *[Symbol.asyncIterator]() {} },
     transcriptBootstrap: {
       throughSequence: 4,
-      durableCoverage: 'complete',
       overlayMessageCount: 0,
       durable: bootstrapPage,
       overlay: { ...page(null), source: 'overlay' },
@@ -550,7 +544,6 @@ test('retains the reading anchor while an older page replaces the far edges', as
     events: { async *[Symbol.asyncIterator]() {} },
     transcriptBootstrap: {
       throughSequence: 7,
-      durableCoverage: 'complete',
       overlayMessageCount: 0,
       durable: bootstrapPage,
       overlay: { ...transcriptPage('older', null, 7), source: 'overlay' },
@@ -576,11 +569,10 @@ test('retains the reading anchor while an older page replaces the far edges', as
   assert.equal(snapshot.hasNewer, true);
 });
 
-for (const { coverage, textBytes } of (['complete', 'projected'] as const).flatMap((coverage) =>
-  [0, 300 * 1024, 600 * 1024].map((textBytes) => ({ coverage, textBytes })),
+for (const { stride, textBytes } of [1, 3].flatMap((stride) =>
+  [0, 300 * 1024, 600 * 1024].map((textBytes) => ({ stride, textBytes })),
 )) {
-  test(`scrolls both ways through bounded ${coverage} history with ${textBytes}-byte Turns`, async () => {
-    const stride = coverage === 'projected' ? 3 : 1;
+  test(`scrolls both ways through bounded stride-${stride} history with ${textBytes}-byte Turns`, async () => {
     const messages = Array.from({ length: 40 }, (_, index) => ({
       identity: index * stride,
       message: { ...assistantMessage('x'.repeat(textBytes), `assistant-${index}`), turnId: `turn-${index}` },
@@ -610,7 +602,6 @@ for (const { coverage, textBytes } of (['complete', 'projected'] as const).flatM
       async close() {},
       transcriptBootstrap: {
         throughSequence: through,
-        durableCoverage: coverage,
         overlayMessageCount: 0,
         durable: makePage('older', null),
         overlay: { ...transcriptPage('older', null, through), source: 'overlay' },
@@ -708,7 +699,6 @@ test('delivers a mid-session tail append even while a history window is resident
     events: { async *[Symbol.asyncIterator]() {} },
     transcriptBootstrap: {
       throughSequence: 4,
-      durableCoverage: 'complete',
       overlayMessageCount: 0,
       durable: bootstrapPage,
       overlay: { ...page(null), source: 'overlay' },
@@ -759,7 +749,6 @@ test('advances a projected transcript across hidden durable records', async () =
     events: { async *[Symbol.asyncIterator]() {} },
     transcriptBootstrap: {
       throughSequence: 1,
-      durableCoverage: 'projected',
       overlayMessageCount: 0,
       durable: bootstrapPage,
       overlay: { ...transcriptPage('older', null, 1), source: 'overlay' },
@@ -816,7 +805,6 @@ test('keeps an oversized streaming Turn visible when its overlay settles', async
     events: { async *[Symbol.asyncIterator]() {} },
     transcriptBootstrap: {
       throughSequence: older.identity,
-      durableCoverage: 'complete',
       overlayMessageCount: 1,
       durable: bootstrapPage,
       overlay: { ...transcriptPage('older', null, older.identity), source: 'overlay' },
@@ -868,7 +856,6 @@ test('keeps an oversized settled Turn visible before a trailing session note', a
     events: { async *[Symbol.asyncIterator]() {} },
     transcriptBootstrap: {
       throughSequence: older.identity,
-      durableCoverage: 'complete',
       overlayMessageCount: 1,
       durable: bootstrapPage,
       overlay: { ...bootstrapPage, source: 'overlay' },
@@ -933,7 +920,6 @@ test('does not resurrect a discarded replica when a tail re-anchor is in flight'
     events: { async *[Symbol.asyncIterator]() {} },
     transcriptBootstrap: {
       throughSequence: 4,
-      durableCoverage: 'complete',
       overlayMessageCount: 0,
       durable: bootstrapPage,
       overlay: { ...page(null), source: 'overlay' },
@@ -1021,7 +1007,6 @@ for (const direction of ['older', 'newer'] as const) {
       events: { async *[Symbol.asyncIterator]() {} },
       transcriptBootstrap: {
         throughSequence: 4,
-        durableCoverage: 'complete',
         overlayMessageCount: 0,
         durable: bootstrapPage,
         overlay: { ...page(null), source: 'overlay' },
@@ -1099,7 +1084,6 @@ test('does not drive a discarded replica terminal when a contiguous catch-up is
     events: { async *[Symbol.asyncIterator]() {} },
     transcriptBootstrap: {
       throughSequence: 4,
-      durableCoverage: 'complete',
       overlayMessageCount: 0,
       durable: bootstrapPage,
       overlay: { ...page(null, 4), source: 'overlay' },
@@ -1147,14 +1131,13 @@ test('loads a history target with newer messages available below it', async () =
   }));
   const bootstrapPage = transcriptPage('older', null, 4);
   const aroundPage = transcriptPage('newer', 'newer', 4);
-  let aroundInput: { direction: string; anchorSequence: number | null } | undefined;
+  const inputs: Array<{ direction: string; anchorSequence: number | null }> = [];
   const handle = runtimeHostSessionFixture({
     snapshot: continuitySnapshot(),
     transcript: Promise.resolve([]),
     events: { async *[Symbol.asyncIterator]() {} },
     transcriptBootstrap: {
       throughSequence: 4,
-      durableCoverage: 'complete',
       overlayMessageCount: 0,
       durable: bootstrapPage,
       overlay: { ...transcriptPage('older', null, 4), source: 'overlay' },
@@ -1164,8 +1147,8 @@ test('loads a history target with newer messages available below it', async () =
       ? { messages: messages.slice(4), nextCursor: null }
       : { messages: messages.slice(0, 3), nextCursor: 'newer' },
     loadTranscriptPage: async (input) => {
-      aroundInput = input;
-      return aroundPage;
+      inputs.push(input);
+      return input.direction === 'older' ? olderProbePage(0, false) : aroundPage;
     },
     async close() {},
   });
@@ -1175,8 +1158,14 @@ test('loads a history target with newer messages available below it', async () =
 
   await replica.loadAround(0, 128 * 1024);
 
-  assert.equal(aroundInput?.direction, 'newer');
-  assert.equal(aroundInput?.anchorSequence, null);
+  assert.deepEqual(
+    inputs.map(({ direction, anchorSequence }) => ({ direction, anchorSequence })),
+    [
+      { direction: 'newer', anchorSequence: null },
+      // Nothing older than the anchor exists, and only this read can say so.
+      { direction: 'older', anchorSequence: 0 },
+    ],
+  );
   assert.deepEqual(replica.snapshot().durable.map(({ sequence }) => sequence), [0, 1, 2]);
   assert.equal(replica.snapshot().hasOlder, false);
   assert.equal(replica.snapshot().hasNewer, true);
@@ -1207,7 +1196,6 @@ test('keeps an oversized transcript sparse while moving between indexed prompts'
     events: { async *[Symbol.asyncIterator]() {} },
     transcriptBootstrap: {
       throughSequence: 15,
-      durableCoverage: 'complete',
       overlayMessageCount: 0,
       durable: bootstrapPage,
       overlay: { ...transcriptPage('older', null, 15), source: 'overlay' },
@@ -1224,7 +1212,10 @@ test('keeps an oversized transcript sparse while moving between indexed prompts'
         anchorSequence: input.anchorSequence,
         maxBytes: input.maxBytes,
       });
-      if (input.direction === 'older') return latestPage;
+      if (input.direction === 'older') {
+        if (input.maxBytes > 1) return latestPage;
+        return olderProbePage(input.anchorSequence!, input.anchorSequence !== 0);
+      }
       return input.anchorSequence === null ? historicalPage : intermediatePage;
     },
     async close() {},
@@ -1269,9 +1260,13 @@ test('keeps an oversized transcript sparse while moving between indexed prompts'
   assert.equal(rendererStore.range().hasNewer, false);
   assertRangeFitsBudget(rendererStore);
 
+  // Every jump that is not to the tail pays one extra single-byte read, the
+  // only thing that can say whether the anchor has anything older than it.
   assert.deepEqual(requests, [
     { direction: 'newer', anchorSequence: null, maxBytes: DESKTOP_TRANSCRIPT_RANGE_MAX_BYTES },
+    { direction: 'older', anchorSequence: 0, maxBytes: 1 },
     { direction: 'newer', anchorSequence: 5, maxBytes: DESKTOP_TRANSCRIPT_RANGE_MAX_BYTES },
+    { direction: 'older', anchorSequence: 6, maxBytes: 1 },
     { direction: 'older', anchorSequence: 16, maxBytes: DESKTOP_TRANSCRIPT_RANGE_MAX_BYTES },
   ]);
   replica.close();
@@ -1311,7 +1306,6 @@ test('keeps history resident when an active overlay uses its own cache budget',
     events: { async *[Symbol.asyncIterator]() {} },
     transcriptBootstrap: {
       throughSequence: 1,
-      durableCoverage: 'complete',
       overlayMessageCount: 1,
       durable: bootstrapPage,
       overlay: { ...transcriptPage('older', null, 1), source: 'overlay' },
@@ -1602,6 +1596,26 @@ function transcriptPage(
   };
 }
 
+/** The one-byte read `loadAround` uses to ask whether `sequence` has anything
+ *  older than it: only the presence of a fragment answers, not its content. */
+function olderProbePage(sequence: number, exists: boolean) {
+  return {
+    ...transcriptPage('older', null, sequence),
+    fragments: exists
+      ? [
+          {
+            kind: 'durable' as const,
+            sequence,
+            byteOffset: 0,
+            totalBytes: 1,
+            payloadDigest: null,
+            data: '',
+          },
+        ]
+      : [],
+  };
+}
+
 function syntheticLargeTranscript(): Array<{ identity: number; message: StoredMessage }> {
   return Array.from({ length: 8 }, (_, index) => {
     const number = index + 1;

apps/desktop/src/main/__tests__/interrupted-resume.test.ts

@@ -83,7 +83,6 @@ describe('latest interrupted resume candidate', () => {
         ts: 2,
         status: 'failed',
         errorClass: 'timeout',
-        partialOutputRetained: false,
       },
       { type: 'tool_call', id: 'call-1', turnId: 'turn-1', ts: 3, toolName: 'Read', args: {} },
       {

apps/desktop/src/main/__tests__/quote-companion-disposal.test.ts

@@ -50,7 +50,7 @@ function session(id: string): SessionSummary {
 }
 
 function settledTurn(turnId: string): TurnRecord {
-  return { turnId, status: 'completed', partialOutputRetained: false };
+  return { turnId, status: 'completed' };
 }
 
 const sourceSession = session('side-chat-disposal-source');

apps/desktop/src/main/__tests__/quote-companion-retry.test.ts

@@ -2088,11 +2088,11 @@ function choiceFor(
 }
 
 function settledTurn(turnId: string): TurnRecord {
-  return { turnId, status: 'completed', partialOutputRetained: false };
+  return { turnId, status: 'completed' };
 }
 
 function runningTurn(turnId: string): TurnRecord {
-  return { turnId, status: 'running', partialOutputRetained: false };
+  return { turnId, status: 'running' };
 }
 
 async function waitUntil(predicate: () => boolean, diagnostics?: () => string): Promise<void> {

apps/desktop/src/main/__tests__/runtime-host-client.test.ts

@@ -78,11 +78,6 @@ test('derives turn records from bounded contribution pages', async () => {
             firstSequence: 0,
             latestState: null,
             userPromptPreview: 'hello',
-            hasAssistantMessage: true,
-            hasAssistantOutput: true,
-            hasToolResult: false,
-            hasFailedToolResult: false,
-            hasAbortNote: false,
           }],
           nextPosition: 2,
         };
@@ -101,15 +96,9 @@ test('derives turn records from bounded contribution pages', async () => {
               turnId: 'turn-1',
               ts: 3,
               status: 'completed',
-              partialOutputRetained: false,
             },
           },
           userPromptPreview: null,
-          hasAssistantMessage: false,
-          hasAssistantOutput: false,
-          hasToolResult: true,
-          hasFailedToolResult: false,
-          hasAbortNote: false,
         }],
         nextPosition: null,
       };
@@ -124,7 +113,6 @@ test('derives turn records from bounded contribution pages', async () => {
     userPromptPreview: 'hello',
     status: 'completed',
     statusSource: 'recorded',
-    partialOutputRetained: true,
   }]);
   assert.deepEqual(positions, [0, 2]);
   await client.close();
@@ -164,7 +152,6 @@ function subscription(
     activeAssistantStreams: [],
     transcriptBootstrap: {
       throughSequence: null,
-      durableCoverage: 'complete',
       overlayMessageCount: 0,
       durable: emptyTranscriptPage(sessionId, 'durable'),
       overlay: emptyTranscriptPage(sessionId, 'overlay'),

apps/desktop/src/main/__tests__/runtime-host-session-observer.test.ts

@@ -694,7 +694,6 @@ test('fences transcript range failures across same-source replica recovery', asy
           events,
           transcriptBootstrap: {
             throughSequence: 1,
-            durableCoverage: 'complete',
             overlayMessageCount: 0,
             durable: bootstrap,
             overlay: { ...bootstrap, source: 'overlay', nextCursor: null },
@@ -990,7 +989,6 @@ test('finishes transcript open and replays a stale range request after replaceme
           events,
           transcriptBootstrap: {
             throughSequence: 0,
-            durableCoverage: 'complete',
             overlayMessageCount: 0,
             durable: {
               kind: 'page',
@@ -2166,7 +2164,6 @@ test("finishes a watched predecessor after initial catch-up recovery", async ()
               turnId: "turn-1",
               ts: 20,
               status: "completed" as const,
-              partialOutputRetained: true,
             },
           ]),
           events: secondEvents,
@@ -2322,7 +2319,6 @@ test("reconciles terminal, Goal, interaction, and sidecar state after subscripti
         turnId: 'turn-1',
         status: 'completed' as const,
         statusSource: 'recorded' as const,
-        partialOutputRetained: true,
       }],
       openSession: async () => {
         openCount += 1;

apps/desktop/src/main/__tests__/runtime-host-session-test-fixture.ts

@@ -46,7 +46,6 @@ export function runtimeHostSessionFixture(input: {
     activeAssistantStreams: input.activeAssistantStreams ?? [],
     transcriptBootstrap: input.transcriptBootstrap ?? {
       throughSequence: null,
-      durableCoverage: 'complete',
       overlayMessageCount: 0,
       durable: emptyPage(sessionId, 'durable'),
       overlay: emptyPage(sessionId, 'overlay'),