coder · ibetitsmike · Jul 10, 2026
diff --git a/coderd/apidoc/docs.go b/coderd/apidoc/docs.go
diff --git a/coderd/apidoc/swagger.json b/coderd/apidoc/swagger.json
diff --git a/coderd/database/db2sdk/db2sdk.go b/coderd/database/db2sdk/db2sdk.go
@@ -1700,6 +1700,8 @@ func Chat(c database.Chat, diffStatus *database.ChatDiffStatus, files []database
 		LastModelConfigID: c.LastModelConfigID,
 		Title:             c.Title,
 		Status:            codersdk.ChatStatus(c.Status),
+		HistoryVersion:    c.HistoryVersion,
+		GenerationAttempt: c.GenerationAttempt,
 		Archived:          c.Archived,
 		Shared:            len(c.UserACL) > 0 || len(c.GroupACL) > 0,
 		PinOrder:          c.PinOrder,

diff --git a/coderd/database/db2sdk/db2sdk_test.go b/coderd/database/db2sdk/db2sdk_test.go
@@ -710,6 +710,8 @@ func TestChat_AllFieldsPopulated(t *testing.T) {
 		LastReasoningEffort: database.NullChatReasoningEffort{ChatReasoningEffort: database.ChatReasoningEffortHigh, Valid: true},
 		Title:               "all-fields-test",
 		Status:              database.ChatStatusRunning,
+		HistoryVersion:      7,
+		GenerationAttempt:   2,
 		ClientType:          database.ChatClientTypeUi,
 		LastError:           pqtype.NullRawMessage{RawMessage: lastErrorRaw, Valid: true},
 		LastTurnSummary:     sql.NullString{String: "turn completed", Valid: true},

diff --git a/coderd/x/chatd/ARCHITECTURE.md b/coderd/x/chatd/ARCHITECTURE.md
@@ -869,17 +869,20 @@ The stream loop powers the `GET /api/experimental/chats/{chat}/stream` endpoint.
 
 The following chat stream events, delivered to the client over WebSocket, are supported:
 
-- `message_part`: a streaming message part emitted by the chat worker.
-    - compared to the current implementation, these should additionally include the `history_version` and `generation_attempt` fields, so a client knows which episode a message part comes from
+- `message_part`: a streaming message part emitted by the chat worker. Its payload includes `history_version`, `generation_attempt`, and `seq`, which identify the part's episode and position.
 - `message`: a committed chat message present in the database.
-- `status`: the chat's status.
+- `status`: the chat's status plus the current `history_version` and `generation_attempt`. Clients can use this tuple as a lower bound when rejecting stale parts.
 - `error`: the chat's persisted error payload.
 - `queue_update`: the full current queued-message list.
 - `action_required`: a dynamic tool call was issued by the chat worker, the client must execute it and submit the result.
 - `retry`: emitted when the chat worker is waiting before retrying a failed generation attempt.
 - `preview_reset`: a reset of the stream's preview state (message parts), emitted when the worker's LLM call fails mid-way for whatever reason.
 - `history_reset`: a reset of the stream's history state (committed messages), emitted when the message history is edited and some messages are removed from the history.
 
+Database-derived events from one `Sync` are emitted in the application order described below, including `message` before `queue_update` before `status`. Relayed `message_part` events are multiplexed independently, so there is no total ordering between parts and database-derived events.
+
+The single-chat REST response exposes the same `history_version` and `generation_attempt` tuple as status events. A pure status transition advances `snapshot_version` but keeps this tuple stable, so it must not fence out parts from the active episode. A history change advances `history_version` and resets `generation_attempt` to `0`; the next generation starts at the same history version with a higher attempt.
+
 ## Endpoint lifecycle
 
 When a client connects, the endpoint:
@@ -1079,7 +1082,7 @@ Status sync happens inside `Sync`.
 Flow:
 
 1. Compare database status to local status.
-2. If they differ, emit `status`.
+2. If they differ, emit `status` with `db.status`, `db.history_version`, and `db.generation_attempt`.
 
 ### Error synchronization
 

diff --git a/coderd/x/chatd/stream_loop.go b/coderd/x/chatd/stream_loop.go
@@ -252,7 +252,11 @@ func (l *streamLoop) applyDBSnapshot(snapshot streamDBSnapshot) []codersdk.ChatS
 		events = append(events, codersdk.ChatStreamEvent{
 			Type:   codersdk.ChatStreamEventTypeStatus,
 			ChatID: l.chatID,
-			Status: &codersdk.ChatStreamStatus{Status: codersdk.ChatStatus(chat.Status)},
+			Status: &codersdk.ChatStreamStatus{
+				Status:            codersdk.ChatStatus(chat.Status),
+				HistoryVersion:    chat.HistoryVersion,
+				GenerationAttempt: chat.GenerationAttempt,
+			},
 		})
 	}
 

diff --git a/coderd/x/chatd/stream_loop_internal_test.go b/coderd/x/chatd/stream_loop_internal_test.go
@@ -213,6 +213,8 @@ func TestStreamLoopQueueStatusRetryErrorActionRequiredAndPreviewReset(t *testing
 		codersdk.ChatStreamEventTypeRetry,
 		codersdk.ChatStreamEventTypePreviewReset,
 	)
+	require.Equal(t, int64(2), events[1].Status.HistoryVersion)
+	require.Equal(t, int64(2), events[1].Status.GenerationAttempt)
 	require.Equal(t, chatError.Message, events[2].Error.Message)
 	require.Equal(t, retry.Attempt, events[3].Retry.Attempt)
 
@@ -231,9 +233,100 @@ func TestStreamLoopQueueStatusRetryErrorActionRequiredAndPreviewReset(t *testing
 		codersdk.ChatStreamEventTypeActionRequired,
 		codersdk.ChatStreamEventTypePreviewReset,
 	)
+	require.Equal(t, int64(1), actionEvents[0].Status.HistoryVersion)
+	require.Zero(t, actionEvents[0].Status.GenerationAttempt)
 	require.Equal(t, "call-1", actionEvents[1].ActionRequired.ToolCalls[0].ToolCallID)
 }
 
+func TestStreamLoopStatusCarriesPartConsistentEpisode(t *testing.T) {
+	t.Parallel()
+
+	chatID := uuid.New()
+	loop := newStreamLoop(database.Chat{ID: chatID}, nil, slogtest.Make(t, nil), 0)
+	loop.state.snapshotVersion = 10
+	loop.state.historyVersion = 7
+	loop.state.generationAttempt = 1
+	loop.state.status = database.ChatStatusRunning
+
+	// A pure status transition must keep the active part episode even though
+	// snapshot_version advances.
+	events := loop.applyDBSnapshot(streamDBSnapshot{chat: database.Chat{
+		ID:                chatID,
+		Status:            database.ChatStatusInterrupting,
+		SnapshotVersion:   11,
+		HistoryVersion:    7,
+		GenerationAttempt: 1,
+	}})
+	requireEventTypes(t, events, codersdk.ChatStreamEventTypeStatus)
+	require.Equal(t, int64(7), events[0].Status.HistoryVersion)
+	require.Equal(t, int64(1), events[0].Status.GenerationAttempt)
+	_, accepted, err := loop.part(StreamPart{
+		HistoryVersion:    7,
+		GenerationAttempt: 1,
+		Seq:               1,
+		Part:              codersdk.ChatMessageText("draining"),
+	})
+	require.NoError(t, err)
+	require.True(t, accepted)
+
+	// History changes reset the attempt; retries advance it within that history.
+	events = loop.applyDBSnapshot(streamDBSnapshot{chat: database.Chat{
+		ID:                chatID,
+		Status:            database.ChatStatusRunning,
+		SnapshotVersion:   12,
+		HistoryVersion:    12,
+		GenerationAttempt: 0,
+	}})
+	requireEventTypes(t, events,
+		codersdk.ChatStreamEventTypeStatus,
+		codersdk.ChatStreamEventTypePreviewReset,
+	)
+	require.Equal(t, int64(12), events[0].Status.HistoryVersion)
+	require.Zero(t, events[0].Status.GenerationAttempt)
+
+	events = loop.applyDBSnapshot(streamDBSnapshot{chat: database.Chat{
+		ID:                chatID,
+		Status:            database.ChatStatusRunning,
+		SnapshotVersion:   13,
+		HistoryVersion:    12,
+		GenerationAttempt: 1,
+	}})
+	requireEventTypes(t, events, codersdk.ChatStreamEventTypePreviewReset)
+	_, accepted, err = loop.part(StreamPart{
+		HistoryVersion:    12,
+		GenerationAttempt: 1,
+		Seq:               1,
+		Part:              codersdk.ChatMessageText("new turn"),
+	})
+	require.NoError(t, err)
+	require.True(t, accepted)
+
+	events = loop.applyDBSnapshot(streamDBSnapshot{chat: database.Chat{
+		ID:                chatID,
+		Status:            database.ChatStatusRunning,
+		SnapshotVersion:   14,
+		HistoryVersion:    12,
+		GenerationAttempt: 2,
+	}})
+	requireEventTypes(t, events, codersdk.ChatStreamEventTypePreviewReset)
+	_, accepted, err = loop.part(StreamPart{
+		HistoryVersion:    12,
+		GenerationAttempt: 1,
+		Seq:               2,
+		Part:              codersdk.ChatMessageText("stale retry"),
+	})
+	require.NoError(t, err)
+	require.False(t, accepted)
+	_, accepted, err = loop.part(StreamPart{
+		HistoryVersion:    12,
+		GenerationAttempt: 2,
+		Seq:               1,
+		Part:              codersdk.ChatMessageText("retry"),
+	})
+	require.NoError(t, err)
+	require.True(t, accepted)
+}
+
 func TestStreamLoopActionRequiredFromHistory(t *testing.T) {
 	t.Parallel()
 

diff --git a/codersdk/chats.go b/codersdk/chats.go
@@ -119,6 +119,8 @@ type Chat struct {
 	LastReasoningEffort *string         `json:"last_reasoning_effort,omitempty"`
 	Title               string          `json:"title"`
 	Status              ChatStatus      `json:"status"`
+	HistoryVersion      int64           `json:"history_version,omitempty"`
+	GenerationAttempt   int64           `json:"generation_attempt,omitempty"`
 	PlanMode            ChatPlanMode    `json:"plan_mode,omitempty"`
 	LastError           *ChatError      `json:"last_error,omitempty"`
 	LastTurnSummary     *string         `json:"last_turn_summary"`
@@ -1649,7 +1651,9 @@ type ChatStreamMessagePart struct {
 
 // ChatStreamStatus represents an updated chat status.
 type ChatStreamStatus struct {
-	Status ChatStatus `json:"status"`
+	Status            ChatStatus `json:"status"`
+	HistoryVersion    int64      `json:"history_version,omitempty"`
+	GenerationAttempt int64      `json:"generation_attempt,omitempty"`
 }
 
 // ChatErrorKind classifies chat errors for consistent client rendering.