Merge pull request #844 from Molecule-AI/feat/slack-bot-api-channels

feat(slack): Bot API adapter with per-agent identity + fix pgvector migration guard

platform/cmd/server/main.go

@@ -196,6 +196,9 @@ func main() {
 	channelMgr := channels.NewManager(wh, broadcaster)
 	go supervised.RunWithRecover(ctx, "channel-manager", channelMgr.Start)
 
+	// Wire channel manager into scheduler for auto-posting cron output to Slack
+	cronSched.SetChannels(channelMgr)
+
 	// Router
 	r := router.Setup(hub, broadcaster, prov, platformURL, configsDir, wh, channelMgr)
 

platform/internal/channels/manager.go

@@ -437,6 +437,41 @@ func (m *Manager) SendOutbound(ctx context.Context, channelID string, text strin
 	return nil
 }
 
+// BroadcastToWorkspaceChannels sends a message to ALL enabled channels
+// configured for a workspace. Used by the scheduler to auto-post cron
+// output summaries and by delegation handlers to post completion notices.
+//
+// Unlike SendOutbound (which targets a specific channel row by ID), this
+// fans out to every enabled channel for the workspace — so a single cron
+// completion posts to both #mol-engineering AND #mol-firehose if the
+// workspace has both configured via chat_id comma-separation.
+func (m *Manager) BroadcastToWorkspaceChannels(ctx context.Context, workspaceID, text string) {
+	if text == "" || db.DB == nil {
+		return
+	}
+	// Truncate to keep Slack messages digestible (rune-safe for CJK/emoji)
+	runes := []rune(text)
+	if len(runes) > 500 {
+		text = string(runes[:497]) + "..."
+	}
+	rows, err := db.DB.QueryContext(ctx, `
+		SELECT id FROM workspace_channels
+		WHERE workspace_id = $1 AND enabled = true
+	`, workspaceID)
+	if err != nil {
+		return
+	}
+	defer rows.Close()
+	for rows.Next() {
+		var channelID string
+		if rows.Scan(&channelID) == nil {
+			if sendErr := m.SendOutbound(ctx, channelID, text); sendErr != nil {
+				log.Printf("Channels: broadcast to %s failed: %v", channelID[:12], sendErr)
+			}
+		}
+	}
+}
+
 func splitChatIDs(raw string) []string {
 	var ids []string
 	for _, s := range strings.Split(raw, ",") {

platform/internal/channels/slack.go

@@ -19,6 +19,8 @@ const (
 	slackHTTPTimeout   = 10 * time.Second
 )
 
+var slackHTTPClient = &http.Client{Timeout: slackHTTPTimeout}
+
 // SlackAdapter implements ChannelAdapter for Slack Incoming Webhooks.
 //
 // Outbound messages are sent via Slack Incoming Webhooks (the simple,
@@ -35,19 +37,90 @@ func (s *SlackAdapter) DisplayName() string { return "Slack" }
 // Returns an error whose message becomes part of the 400 response body so
 // keep it human-readable for the canvas UI.
 func (s *SlackAdapter) ValidateConfig(config map[string]interface{}) error {
+	botToken, _ := config["bot_token"].(string)
 	webhookURL, _ := config["webhook_url"].(string)
-	if webhookURL == "" {
-		return fmt.Errorf("missing required field: webhook_url")
+	if botToken == "" && webhookURL == "" {
+		return fmt.Errorf("missing required field: bot_token or webhook_url")
 	}
-	if !strings.HasPrefix(webhookURL, slackWebhookPrefix) {
+	if botToken != "" {
+		if cid, _ := config["channel_id"].(string); cid == "" {
+			return fmt.Errorf("bot_token mode requires channel_id")
+		}
+	}
+	if webhookURL != "" && !strings.HasPrefix(webhookURL, slackWebhookPrefix) {
 		return fmt.Errorf("invalid Slack webhook URL")
 	}
 	return nil
 }
 
-// SendMessage posts text to the configured Slack Incoming Webhook.
-// chatID is ignored for Slack webhooks — the channel is encoded in the URL.
-func (s *SlackAdapter) SendMessage(ctx context.Context, config map[string]interface{}, _ string, text string) error {
+// SendMessage posts text to Slack. Supports two modes:
+//
+//   - Bot API (bot_token set): uses chat.postMessage with per-agent identity
+//     via chat:write.customize scope. Supports username + icon_emoji overrides.
+//   - Webhook (webhook_url set, legacy): simple POST, no identity override.
+//
+// chatID overrides channel_id from config if non-empty (for multi-channel routing).
+func (s *SlackAdapter) SendMessage(ctx context.Context, config map[string]interface{}, chatID string, text string) error {
+	botToken, _ := config["bot_token"].(string)
+	if botToken != "" {
+		return s.sendBotMessage(ctx, config, chatID, text)
+	}
+	return s.sendWebhookMessage(ctx, config, text)
+}
+
+func (s *SlackAdapter) sendBotMessage(ctx context.Context, config map[string]interface{}, chatID, text string) error {
+	botToken, _ := config["bot_token"].(string)
+	channelID := chatID
+	if channelID == "" {
+		channelID, _ = config["channel_id"].(string)
+	}
+	if channelID == "" {
+		return fmt.Errorf("slack: no channel_id")
+	}
+
+	username, _ := config["username"].(string)
+	iconEmoji, _ := config["icon_emoji"].(string)
+
+	// Split long messages at newline boundaries
+	chunks := slackSplitMessage(text, 3000)
+	for _, chunk := range chunks {
+		payload := map[string]interface{}{
+			"channel": channelID,
+			"text":    chunk,
+		}
+		if username != "" {
+			payload["username"] = username
+		}
+		if iconEmoji != "" {
+			payload["icon_emoji"] = iconEmoji
+		}
+
+		body, _ := json.Marshal(payload)
+		req, err := http.NewRequestWithContext(ctx, http.MethodPost, "https://slack.com/api/chat.postMessage", bytes.NewReader(body))
+		if err != nil {
+			return fmt.Errorf("slack: build request: %w", err)
+		}
+		req.Header.Set("Content-Type", "application/json; charset=utf-8")
+		req.Header.Set("Authorization", "Bearer "+botToken)
+
+		resp, err := slackHTTPClient.Do(req)
+		if err != nil {
+			return fmt.Errorf("slack: send: %w", err)
+		}
+		respBody, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
+		resp.Body.Close()
+		var result struct {
+			OK    bool   `json:"ok"`
+			Error string `json:"error"`
+		}
+		if json.Unmarshal(respBody, &result) == nil && !result.OK {
+			return fmt.Errorf("slack: API error: %s", result.Error)
+		}
+	}
+	return nil
+}
+
+func (s *SlackAdapter) sendWebhookMessage(ctx context.Context, config map[string]interface{}, text string) error {
 	webhookURL, _ := config["webhook_url"].(string)
 	if webhookURL == "" {
 		return fmt.Errorf("webhook_url not configured")
@@ -67,12 +140,10 @@ func (s *SlackAdapter) SendMessage(ctx context.Context, config map[string]interf
 	}
 	req.Header.Set("Content-Type", "application/json")
 
-	client := &http.Client{Timeout: slackHTTPTimeout}
-	resp, err := client.Do(req)
+	resp, err := slackHTTPClient.Do(req)
 	if err != nil {
 		return fmt.Errorf("slack: send: %w", err)
 	}
-	defer resp.Body.Close()
 
 	if resp.StatusCode != http.StatusOK {
 		body, _ := io.ReadAll(resp.Body)
@@ -81,6 +152,27 @@ func (s *SlackAdapter) SendMessage(ctx context.Context, config map[string]interf
 	return nil
 }
 
+func slackSplitMessage(text string, maxLen int) []string {
+	if len(text) <= maxLen {
+		return []string{text}
+	}
+	var chunks []string
+	for len(text) > 0 {
+		end := maxLen
+		if end > len(text) {
+			end = len(text)
+		}
+		if end < len(text) {
+			if idx := strings.LastIndex(text[:end], "\n"); idx > 0 {
+				end = idx + 1
+			}
+		}
+		chunks = append(chunks, text[:end])
+		text = text[end:]
+	}
+	return chunks
+}
+
 // ParseWebhook handles a Slack slash command or event API POST.
 // The payload is either URL-encoded (slash commands) or JSON (Events API).
 // Returns nil, nil for non-message events (e.g. url_verification challenge).
@@ -112,27 +204,34 @@ func (s *SlackAdapter) ParseWebhook(c *gin.Context, _ map[string]interface{}) (*
 
 		var payload struct {
 			Type      string `json:"type"`
-			Challenge string `json:"challenge"` // url_verification
+			Challenge string `json:"challenge"`
 			Event     struct {
 				Type    string `json:"type"`
 				User    string `json:"user"`
 				Text    string `json:"text"`
 				Channel string `json:"channel"`
 				Ts      string `json:"ts"`
+				BotID   string `json:"bot_id"`
+				Subtype string `json:"subtype"`
 			} `json:"event"`
 		}
 		if err := json.Unmarshal(body, &payload); err != nil {
 			return nil, fmt.Errorf("slack: parse event: %w", err)
 		}
 
-		// url_verification handshake — no message, respond via the handler layer
+		// url_verification handshake — respond with challenge directly
 		if payload.Type == "url_verification" {
-			log.Printf("Channels: Slack url_verification challenge (not handled by ParseWebhook)")
+			c.JSON(200, gin.H{"challenge": payload.Challenge})
 			return nil, nil
 		}
 
+		// Ignore bot messages to prevent echo loops. Our own auto-posts
+		// via chat.postMessage fire Events API callbacks with bot_id set.
+		if payload.Event.BotID != "" || payload.Event.Subtype == "bot_message" {
+			return nil, nil
+		}
 		if payload.Event.Type != "message" || payload.Event.Text == "" {
-			return nil, nil // Ignore non-message events
+			return nil, nil
 		}
 
 		text = payload.Event.Text

platform/internal/channels/slack_test.go

@@ -0,0 +1,115 @@
+package channels
+
+import (
+	"context"
+	"strings"
+	"testing"
+)
+
+func TestSlackSplitMessage_Short(t *testing.T) {
+	chunks := slackSplitMessage("hello", 3000)
+	if len(chunks) != 1 || chunks[0] != "hello" {
+		t.Errorf("expected 1 chunk 'hello', got %v", chunks)
+	}
+}
+
+func TestSlackSplitMessage_Long(t *testing.T) {
+	long := strings.Repeat("a", 6000)
+	chunks := slackSplitMessage(long, 3000)
+	if len(chunks) != 2 {
+		t.Errorf("expected 2 chunks, got %d", len(chunks))
+	}
+	for _, c := range chunks {
+		if len(c) > 3000 {
+			t.Errorf("chunk exceeds max: %d", len(c))
+		}
+	}
+}
+
+func TestSlackSplitMessage_SplitAtNewline(t *testing.T) {
+	text := strings.Repeat("x", 2900) + "\n" + strings.Repeat("y", 200)
+	chunks := slackSplitMessage(text, 3000)
+	if len(chunks) != 2 {
+		t.Errorf("expected 2 chunks, got %d", len(chunks))
+	}
+	if !strings.HasSuffix(chunks[0], "\n") {
+		t.Error("first chunk should end at newline boundary")
+	}
+}
+
+func TestSlackValidateConfig_BotToken(t *testing.T) {
+	a := &SlackAdapter{}
+	err := a.ValidateConfig(map[string]interface{}{
+		"bot_token":  "xoxb-test",
+		"channel_id": "C123",
+	})
+	if err != nil {
+		t.Errorf("expected valid, got %v", err)
+	}
+}
+
+func TestSlackValidateConfig_BotTokenMissingChannel(t *testing.T) {
+	a := &SlackAdapter{}
+	err := a.ValidateConfig(map[string]interface{}{
+		"bot_token": "xoxb-test",
+	})
+	if err == nil {
+		t.Error("expected error for missing channel_id")
+	}
+}
+
+func TestSlackValidateConfig_WebhookURL(t *testing.T) {
+	a := &SlackAdapter{}
+	err := a.ValidateConfig(map[string]interface{}{
+		"webhook_url": "https://hooks.slack.com/services/T000/B000/xxx",
+	})
+	if err != nil {
+		t.Errorf("expected valid, got %v", err)
+	}
+}
+
+func TestSlackValidateConfig_InvalidWebhook(t *testing.T) {
+	a := &SlackAdapter{}
+	err := a.ValidateConfig(map[string]interface{}{
+		"webhook_url": "https://evil.com/steal",
+	})
+	if err == nil {
+		t.Error("expected error for invalid webhook URL")
+	}
+}
+
+func TestSlackValidateConfig_NeitherSet(t *testing.T) {
+	a := &SlackAdapter{}
+	err := a.ValidateConfig(map[string]interface{}{})
+	if err == nil {
+		t.Error("expected error when neither bot_token nor webhook_url set")
+	}
+}
+
+func TestFetchChannelHistory_EmptyToken(t *testing.T) {
+	msgs, err := FetchChannelHistory(context.Background(), "", "C123", 10)
+	if err != nil || msgs != nil {
+		t.Errorf("expected nil,nil for empty token, got %v,%v", msgs, err)
+	}
+}
+
+func TestFetchChannelHistory_EmptyChannel(t *testing.T) {
+	msgs, err := FetchChannelHistory(context.Background(), "xoxb-test", "", 10)
+	if err != nil || msgs != nil {
+		t.Errorf("expected nil,nil for empty channel, got %v,%v", msgs, err)
+	}
+}
+
+func TestSlackAdapter_Type(t *testing.T) {
+	a := &SlackAdapter{}
+	if a.Type() != "slack" {
+		t.Errorf("expected 'slack', got %q", a.Type())
+	}
+}
+
+func TestSlackAdapter_DisplayName(t *testing.T) {
+	a := &SlackAdapter{}
+	if a.DisplayName() != "Slack" {
+		t.Errorf("expected 'Slack', got %q", a.DisplayName())
+	}
+}

platform/internal/handlers/channels.go

@@ -12,6 +12,7 @@ import (
 	"log"
 	"net/http"
 	"os"
+	"regexp"
 	"strings"
 
 	"github.com/gin-gonic/gin"
@@ -443,9 +444,27 @@ func (h *ChannelHandler) Webhook(c *gin.Context) {
 		return
 	}
 
+	// [slug] routing: if the message starts with [word], extract it as
+	// a target agent slug and match against the channel config's username
+	// field (lowercased). This lets humans type "[backend] what's #800?"
+	// in a shared channel and route to a specific agent.
+	targetSlug := ""
+	routedText := msg.Text
+	validSlugRe := regexp.MustCompile(`^[a-zA-Z0-9 _-]+$`)
+	if len(msg.Text) > 2 && msg.Text[0] == '[' {
+		if idx := strings.Index(msg.Text, "]"); idx > 1 && idx < 40 {
+			candidate := strings.ToLower(strings.TrimSpace(msg.Text[1:idx]))
+			if validSlugRe.MatchString(candidate) {
+				targetSlug = candidate
+				routedText = strings.TrimSpace(msg.Text[idx+1:])
+				if routedText == "" {
+					routedText = msg.Text
+				}
+			}
+		}
+	}
+
 	// Look up channels by type and find one whose chat_id list contains msg.ChatID.
-	// We can't use SQL LIKE — that matches substrings (chat_id "123" would match "1234").
-	// Fetch all enabled channels of this type, then exact-match in code.
 	rows, err := db.DB.QueryContext(ctx, `
 		SELECT id, workspace_id, channel_type, channel_config, enabled, allowed_users
 		FROM workspace_channels
@@ -458,6 +477,7 @@ func (h *ChannelHandler) Webhook(c *gin.Context) {
 	defer rows.Close()
 
 	var ch channels.ChannelRow
+	var candidates []channels.ChannelRow
 	found := false
 	for rows.Next() {
 		var row channels.ChannelRow
@@ -467,36 +487,59 @@ func (h *ChannelHandler) Webhook(c *gin.Context) {
 		}
 		json.Unmarshal(configJSON, &row.Config)
 		json.Unmarshal(allowedJSON, &row.AllowedUsers)
-		// #319: decrypt sensitive fields before comparing webhook_secret /
-		// using bot_token downstream. Skip rows whose decrypt fails so a
-		// single corrupt channel cannot block webhooks for all others.
 		if err := channels.DecryptSensitiveFields(row.Config); err != nil {
 			log.Printf("Channels: decrypt webhook row %s: %v", row.ID, err)
 			continue
 		}
 
-		// Verify webhook secret_token if the channel has one configured.
-		// #337: use constant-time comparison. Go's `!=` short-circuits on
-		// the first mismatched byte and leaks timing information; an
-		// attacker on the Docker network could enumerate the secret
-		// byte-by-byte. subtle.ConstantTimeCompare runs in time
-		// proportional to the length of the shorter input and returns
-		// 1 on match / 0 otherwise (never -1). Same posture as the
-		// cdp-proxy token compare in host-bridge.
 		if expectedSecret, _ := row.Config["webhook_secret"].(string); expectedSecret != "" {
 			receivedSecret := c.GetHeader("X-Telegram-Bot-Api-Secret-Token")
 			if subtle.ConstantTimeCompare([]byte(receivedSecret), []byte(expectedSecret)) != 1 {
-				continue // Wrong secret — try other channels (could be different bot)
+				continue
 			}
 		}
 
-		// Exact match against the comma-separated chat_id list
 		if matchesChatID(row.Config, msg.ChatID) {
-			ch = row
-			found = true
-			break
+			candidates = append(candidates, row)
 		}
 	}
+
+	if targetSlug != "" {
+		// [slug] routing — match against config username (lowercased)
+		for _, row := range candidates {
+			username, _ := row.Config["username"].(string)
+			usernameLC := strings.ToLower(username)
+			// Match: [backend] → "Backend Engineer", [pm] → "PM", [dev lead] → "Dev Lead"
+			if usernameLC == targetSlug ||
+				strings.HasPrefix(strings.ReplaceAll(usernameLC, " ", "-"), targetSlug) ||
+				strings.HasPrefix(strings.ReplaceAll(usernameLC, " ", ""), targetSlug) {
+				ch = row
+				found = true
+				msg.Text = routedText // Strip the [slug] prefix before routing
+				break
+			}
+		}
+		if !found {
+			// No match for slug — respond with available agents
+			var names []string
+			for _, row := range candidates {
+				if u, _ := row.Config["username"].(string); u != "" {
+					names = append(names, "["+strings.ToLower(strings.ReplaceAll(u, " ", "-"))+"]")
+				}
+			}
+			c.JSON(http.StatusOK, gin.H{
+				"status":          "unknown_agent",
+				"requested_slug":  targetSlug,
+				"available_slugs": names,
+			})
+			return
+		}
+	} else if len(candidates) > 0 {
+		// No [slug] prefix — route to first matching channel (backward compat)
+		ch = candidates[0]
+		found = true
+	}
+
 	if !found {
 		c.JSON(http.StatusOK, gin.H{"status": "no_channel"})
 		return
@@ -505,7 +548,9 @@ func (h *ChannelHandler) Webhook(c *gin.Context) {
 	// Process asynchronously — don't block the webhook response
 	go func() {
 		bgCtx := context.Background()
-		_ = h.manager.HandleInbound(bgCtx, ch, msg)
+		if err := h.manager.HandleInbound(bgCtx, ch, msg); err != nil {
+			log.Printf("Channels: async HandleInbound error for workspace %s: %v", ch.WorkspaceID[:12], err)
+		}
 	}()
 
 	c.JSON(http.StatusOK, gin.H{"status": "accepted"})

platform/internal/scheduler/scheduler.go

@@ -43,12 +43,19 @@ type scheduleRow struct {
 	Prompt      string
 }
 
+// ChannelBroadcaster posts messages to and reads context from workspace channels.
+type ChannelBroadcaster interface {
+	BroadcastToWorkspaceChannels(ctx context.Context, workspaceID, text string)
+	FetchWorkspaceChannelContext(ctx context.Context, workspaceID string) string
+}
+
 // Scheduler polls the workspace_schedules table and fires A2A messages
 // when a schedule's next_run_at has passed. Follows the same goroutine
 // pattern as registry.StartHealthSweep.
 type Scheduler struct {
 	proxy       A2AProxy
 	broadcaster Broadcaster
+	channels    ChannelBroadcaster
 
 	// lastTickAt records the wall-clock time of the most recent tick
 	// (whether it fired schedules or not). Read by Healthy() and the
@@ -67,6 +74,12 @@ func New(proxy A2AProxy, broadcaster Broadcaster) *Scheduler {
 	}
 }
 
+// SetChannels wires the channel manager for auto-posting cron output.
+// Called after both scheduler and channel manager are initialized.
+func (s *Scheduler) SetChannels(ch ChannelBroadcaster) {
+	s.channels = ch
+}
+
 // LastTickAt returns the wall-clock time of the most recently completed tick.
 // Returns a zero time.Time if the scheduler has never completed a tick.
 func (s *Scheduler) LastTickAt() time.Time {
@@ -248,6 +261,17 @@ func (s *Scheduler) fireSchedule(ctx context.Context, sched scheduleRow) {
 	fireCtx, cancel := context.WithTimeout(ctx, fireTimeout)
 	defer cancel()
 
+	// Level 3: inject ambient Slack channel context into the cron prompt.
+	// The agent sees recent peer messages before acting, enabling cross-agent
+	// awareness without explicit A2A delegation. Best-effort — if the fetch
+	// fails or the workspace has no Slack channels, the prompt is unchanged.
+	prompt := sched.Prompt
+	if s.channels != nil {
+		if channelCtx := s.channels.FetchWorkspaceChannelContext(fireCtx, sched.WorkspaceID); channelCtx != "" {
+			prompt = channelCtx + "\n" + prompt
+		}
+	}
+
 	msgID := fmt.Sprintf("cron-%s-%s", short(sched.ID, 8), uuid.New().String()[:8])
 
 	a2aBody, _ := json.Marshal(map[string]interface{}{
@@ -256,7 +280,7 @@ func (s *Scheduler) fireSchedule(ctx context.Context, sched scheduleRow) {
 			"message": map[string]interface{}{
 				"role":      "user",
 				"messageId": msgID,
-				"parts":     []map[string]interface{}{{"kind": "text", "text": sched.Prompt}},
+				"parts":     []map[string]interface{}{{"kind": "text", "text": prompt}},
 			},
 		},
 	})
@@ -360,6 +384,20 @@ func (s *Scheduler) fireSchedule(ctx context.Context, sched scheduleRow) {
 			"status":        lastStatus,
 		})
 	}
+
+	// Level 1: auto-post cron output to workspace's Slack channels.
+	// Only post non-empty successful responses — errors and empties are
+	// noise that clutters the channel without adding value.
+	if s.channels != nil && lastStatus == "ok" && !isEmpty {
+		summary := s.extractResponseSummary(respBody)
+		if summary != "" {
+			go func(wsID, text string) {
+				postCtx, postCancel := context.WithTimeout(context.Background(), 30*time.Second)
+				defer postCancel()
+				s.channels.BroadcastToWorkspaceChannels(postCtx, wsID, text)
+			}(sched.WorkspaceID, summary)
+		}
+	}
 }
 
 // recordSkipped advances next_run_at and logs a cron_run activity entry
@@ -475,6 +513,31 @@ func (s *Scheduler) repairNullNextRunAt(ctx context.Context) {
 // produced no meaningful output. Catches "(no response generated)" from
 // the workspace runtime + genuinely empty/null responses. Used by the
 // consecutive-empty tracker (#795) to detect phantom-producing crons.
+// extractResponseSummary pulls the agent's text from the A2A response body.
+// Returns empty string if parsing fails or the response has no text content.
+func (s *Scheduler) extractResponseSummary(body []byte) string {
+	if len(body) == 0 {
+		return ""
+	}
+	var resp map[string]interface{}
+	if json.Unmarshal(body, &resp) != nil {
+		return ""
+	}
+	// A2A response: result.parts[].text
+	if result, ok := resp["result"].(map[string]interface{}); ok {
+		if parts, ok := result["parts"].([]interface{}); ok {
+			for _, p := range parts {
+				if part, ok := p.(map[string]interface{}); ok {
+					if text, ok := part["text"].(string); ok && text != "" {
+						return text
+					}
+				}
+			}
+		}
+	}
+	return ""
+}
+
 func isEmptyResponse(body []byte) bool {
 	if len(body) == 0 {
 		return true

platform/migrations/031_memories_pgvector.up.sql

@@ -3,10 +3,9 @@
 -- Adds a dense-vector embedding column to agent_memories to power semantic
 -- (cosine-similarity) memory recall alongside the existing FTS path.
 --
--- Requires the pgvector Postgres extension. The entire migration is wrapped
--- in a single DO block so if pgvector is unavailable, ALL statements are
--- skipped (not just CREATE EXTENSION). This prevents "type vector does not
--- exist" errors on the ALTER TABLE / CREATE INDEX that follow.
+-- Requires the pgvector Postgres extension. The DO block is a no-op guard:
+-- if the extension is unavailable this migration exits early so a boot
+-- without pgvector installed does not break the migration sweep.
 --
 -- Issue: #576
 
@@ -20,8 +19,6 @@ BEGIN
 
   -- ivfflat approximate nearest-neighbour index for cosine similarity.
   -- lists=100 is a reasonable default for tables up to ~1M rows.
-  -- Partial index (WHERE embedding IS NOT NULL) keeps it lean — unembedded
-  -- rows are skipped entirely.
   CREATE INDEX IF NOT EXISTS agent_memories_embedding_idx
     ON agent_memories USING ivfflat (embedding vector_cosine_ops)
     WHERE embedding IS NOT NULL;