fix(sync): persist visual studio archive fingerprints

Author: wesm

internal/sync/engine.go

@@ -6116,10 +6116,6 @@ func applyVisualStudioCopilotArchiveSessionFields(
 	}
 	s.StartedAt = earlierSessionTime(archived.StartedAt, s.StartedAt)
 	s.EndedAt = laterSessionTime(archived.EndedAt, s.EndedAt)
-	if storedSize, currentSize := derefInt64(archived.FileSize),
-		derefInt64(s.FileSize); storedSize > currentSize {
-		s.FileSize = int64Ptr(storedSize)
-	}
 }
 
 func visualStudioCopilotMergedFirstMessageFromParsed(
@@ -6251,7 +6247,7 @@ func (e *Engine) reconcileVisualStudioCopilotArchive(
 			agent, sessionID, len(storedMsgs), len(currentMsgs),
 			storedSize, currentSize,
 		)
-		return nil, true, nil
+		return storedMsgs, false, stored
 	}
 	if decision.merged != nil {
 		log.Printf(
@@ -6315,7 +6311,8 @@ func visualStudioCopilotArchiveDecision(
 			updates[storedIndex] = parsedMsg
 		}
 	}
-	additions = visualStudioCopilotResolveArchiveAdditions(
+	fallbackMatched := false
+	additions, fallbackMatched = visualStudioCopilotResolveArchiveAdditions(
 		stored, matchedStored, updates, additions, &hasIncomplete,
 	)
 	hasArchiveOnly := false
@@ -6325,8 +6322,9 @@ func visualStudioCopilotArchiveDecision(
 			break
 		}
 	}
-	if hasIncomplete || hasArchiveOnly {
-		if len(updates) > 0 || len(additions) > 0 {
+	if hasIncomplete || hasArchiveOnly || fallbackMatched {
+		if len(updates) > 0 || len(additions) > 0 ||
+			(fallbackMatched && !hasIncomplete) {
 			return visualStudioCopilotArchiveReconcile{
 				merged: visualStudioCopilotMergeArchiveMessages(
 					stored, updates, additions,
@@ -6344,7 +6342,8 @@ func visualStudioCopilotResolveArchiveAdditions(
 	updates map[int]db.Message,
 	additions []db.Message,
 	hasIncomplete *bool,
-) []db.Message {
+) ([]db.Message, bool) {
+	matched := false
 	unresolved := additions[:0]
 	for _, parsedMsg := range additions {
 		storedIndex, ok := visualStudioCopilotArchiveFallbackMatch(
@@ -6354,6 +6353,7 @@ func visualStudioCopilotResolveArchiveAdditions(
 			unresolved = append(unresolved, parsedMsg)
 			continue
 		}
+		matched = true
 		matchedStored[storedIndex] = true
 		storedMsg := stored[storedIndex]
 		incomplete := visualStudioCopilotMessageLooksIncomplete(
@@ -6370,7 +6370,7 @@ func visualStudioCopilotResolveArchiveAdditions(
 			updates[storedIndex] = update
 		}
 	}
-	return unresolved
+	return unresolved, matched
 }
 
 func visualStudioCopilotArchiveFallbackMatch(
@@ -6448,7 +6448,9 @@ func visualStudioCopilotMessagesShareContentIdentity(
 	if len(parsed.ToolCalls) > 0 || len(stored.ToolCalls) > 0 {
 		return false
 	}
-	if parsed.Role != string(parser.RoleAssistant) {
+	switch parsed.Role {
+	case string(parser.RoleAssistant), string(parser.RoleUser):
+	default:
 		return false
 	}
 	return parsed.Content != "" && parsed.Content == stored.Content

internal/sync/engine_test.go

@@ -1547,6 +1547,71 @@ func TestVisualStudioCopilotArchiveDecisionMatchesTimestampShiftedToolCall(t *te
 	assert.Equal(t, "Archived prompt.", decision.merged[1].Content)
 }
 
+func TestVisualStudioCopilotArchiveDecisionMergesOnlyTimestampShiftedToolCall(t *testing.T) {
+	stored := []db.Message{{
+		Ordinal:       0,
+		Role:          "assistant",
+		Content:       "Run command: dotnet build",
+		ContentLength: len("Run command: dotnet build"),
+		Timestamp:     "2026-06-12T19:46:40Z",
+		ToolCalls: []db.ToolCall{{
+			ToolName:  "run_command_in_terminal",
+			ToolUseID: "call_build",
+		}},
+	}}
+	parsed := []db.Message{{
+		Ordinal:       0,
+		Role:          "assistant",
+		Content:       "Run command: dotnet build",
+		ContentLength: len("Run command: dotnet build"),
+		Timestamp:     "2026-06-12T19:47:40Z",
+		ToolCalls: []db.ToolCall{{
+			ToolName:  "run_command_in_terminal",
+			ToolUseID: "call_build",
+		}},
+	}}
+
+	decision := visualStudioCopilotArchiveDecision(parsed, stored)
+
+	require.False(t, decision.preserve)
+	require.Len(t, decision.merged, 1)
+	assert.Equal(t, "2026-06-12T19:46:40Z", decision.merged[0].Timestamp)
+}
+
+func TestVisualStudioCopilotArchiveDecisionMatchesTimestampShiftedUserPrompt(t *testing.T) {
+	stored := []db.Message{
+		{
+			Ordinal:       0,
+			Role:          "user",
+			Content:       "Archived prompt.",
+			ContentLength: len("Archived prompt."),
+			Timestamp:     "2026-06-12T19:46:40Z",
+		},
+		{
+			Ordinal:       1,
+			Role:          "assistant",
+			Content:       "Archived answer.",
+			ContentLength: len("Archived answer."),
+			Timestamp:     "2026-06-12T19:47:00Z",
+		},
+	}
+	parsed := []db.Message{{
+		Ordinal:       0,
+		Role:          "user",
+		Content:       "Archived prompt.",
+		ContentLength: len("Archived prompt."),
+		Timestamp:     "2026-06-12T19:47:40Z",
+	}}
+
+	decision := visualStudioCopilotArchiveDecision(parsed, stored)
+
+	require.False(t, decision.preserve)
+	require.Len(t, decision.merged, 2)
+	assert.Equal(t, "Archived prompt.", decision.merged[0].Content)
+	assert.Equal(t, "2026-06-12T19:46:40Z", decision.merged[0].Timestamp)
+	assert.Equal(t, "Archived answer.", decision.merged[1].Content)
+}
+
 // fakeEmitter records scopes passed to Emit. Thread-safe so it
 // can be called from engine goroutines under test.
 type fakeEmitter struct {

internal/sync/visualstudio_copilot_integration_test.go

@@ -548,16 +548,30 @@ func TestSyncEngineVisualStudioCopilotPreservesSessionWhenSiblingDeleted(t *test
 	})
 	require.NotZero(t, engine.SyncAll(context.Background(), nil).Synced)
 	assertSessionMessageCount(t, database, sessionID, 2)
+	require.NoError(t, database.SetSessionDataVersion(
+		sessionID, db.CurrentDataVersion()-1,
+	))
 
 	// The sibling that contributed the second turn is rotated away. A reparse now
 	// sees only the first turn; the archived two-turn transcript must be
 	// preserved rather than force-replaced with the partial one.
 	require.NoError(t, os.Remove(sibling))
+	currentSize, currentMtime := parser.VisualStudioCopilotTraceFingerprint(
+		primary,
+	)
 
 	require.NoError(t, engine.SyncSingleSessionContext(
 		context.Background(), sessionID,
 	))
 	assertSessionMessageCount(t, database, sessionID, 2)
+	sess, err := database.GetSessionFull(context.Background(), sessionID)
+	require.NoError(t, err, "GetSessionFull")
+	require.NotNil(t, sess)
+	require.NotNil(t, sess.FileSize)
+	assert.Equal(t, currentSize, *sess.FileSize)
+	require.NotNil(t, sess.FileMtime)
+	assert.Equal(t, currentMtime, *sess.FileMtime)
+	assert.Equal(t, db.CurrentDataVersion(), sess.DataVersion)
 }
 
 // TestSyncEngineVisualStudioCopilotPreservesToolResultsWhenTraceShrinks verifies
@@ -687,6 +701,9 @@ func TestSyncEngineVisualStudioCopilotMergesRicherMatchedMessageWhenTraceShrinks
 	), 0o644))
 	later := time.Unix(1781293800, 0)
 	require.NoError(t, os.Chtimes(primary, later, later))
+	currentSize, currentMtime := parser.VisualStudioCopilotTraceFingerprint(
+		primary,
+	)
 
 	require.NoError(t, engine.SyncSingleSessionContext(
 		context.Background(), sessionID,
@@ -712,6 +729,13 @@ func TestSyncEngineVisualStudioCopilotMergesRicherMatchedMessageWhenTraceShrinks
 		assert.Equal(t, time.Unix(0, 1781293630000000000).UTC().
 			Format(time.RFC3339Nano), *sess.EndedAt)
 	})
+	sess, err := database.GetSessionFull(context.Background(), sessionID)
+	require.NoError(t, err, "GetSessionFull")
+	require.NotNil(t, sess)
+	require.NotNil(t, sess.FileSize)
+	assert.Equal(t, currentSize, *sess.FileSize)
+	require.NotNil(t, sess.FileMtime)
+	assert.Equal(t, currentMtime, *sess.FileMtime)
 }
 
 func TestSyncEngineVisualStudioCopilotMergesUpdateAndPreservesIncompleteSameCount(t *testing.T) {