diff --git a/workspace-server/internal/handlers/a2a_queue.go b/workspace-server/internal/handlers/a2a_queue.go
index 2792f13ca..5be56dfe6 100644
--- a/workspace-server/internal/handlers/a2a_queue.go
+++ b/workspace-server/internal/handlers/a2a_queue.go
@@ -160,10 +160,12 @@ func EnqueueA2A(
 	}
 
 	// Return current queue depth for the caller's visibility.
-	_ = db.DB.QueryRowContext(ctx, `
+	if err := db.DB.QueryRowContext(ctx, `
 		SELECT COUNT(*) FROM a2a_queue
 		WHERE workspace_id = $1 AND status = 'queued'
-	`, workspaceID).Scan(&depth)
+	`, workspaceID).Scan(&depth); err != nil {
+		log.Printf("A2AQueue: depth query failed for workspace %s: %v", workspaceID, err)
+	}
 
 	log.Printf("A2AQueue: enqueued %s for workspace %s (priority=%d, depth=%d)", id, workspaceID, priority, depth)
 	return id, depth, nil
@@ -249,10 +251,12 @@ func MarkQueueItemFailed(ctx context.Context, id, errMsg string) {
 // can see how many ahead of them.
 func QueueDepth(ctx context.Context, workspaceID string) int {
 	var n int
-	_ = db.DB.QueryRowContext(ctx,
+	if err := db.DB.QueryRowContext(ctx,
 		`SELECT COUNT(*) FROM a2a_queue WHERE workspace_id = $1 AND status = 'queued'`,
 		workspaceID,
-	).Scan(&n)
+	).Scan(&n); err != nil {
+		log.Printf("A2AQueue: QueueDepth query failed for workspace %s: %v", workspaceID, err)
+	}
 	return n
 }
 
diff --git a/workspace-server/internal/handlers/registry.go b/workspace-server/internal/handlers/registry.go
index 73e278b39..1b632d6aa 100644
--- a/workspace-server/internal/handlers/registry.go
+++ b/workspace-server/internal/handlers/registry.go
@@ -530,7 +530,9 @@ func (h *RegistryHandler) Heartbeat(c *gin.Context) {
 
 	// Read previous current_task to detect changes (before the UPDATE)
 	var prevTask string
-	_ = db.DB.QueryRowContext(ctx, `SELECT COALESCE(current_task, '') FROM workspaces WHERE id = $1`, payload.WorkspaceID).Scan(&prevTask)
+	if err := db.DB.QueryRowContext(ctx, `SELECT COALESCE(current_task, '') FROM workspaces WHERE id = $1`, payload.WorkspaceID).Scan(&prevTask); err != nil {
+		log.Printf("registry heartbeat: prev_task query failed for workspace %s: %v", payload.WorkspaceID, err)
+	}
 
 	// #615: Clamp monthly_spend to a safe range before any DB write.
 	// A malicious or buggy agent could report math.MaxInt64, causing
@@ -812,10 +814,12 @@ func (h *RegistryHandler) evaluateStatus(c *gin.Context, payload models.Heartbea
 	// timeouts, retry logic, and activity_logs wiring.
 	if h.drainQueue != nil {
 		var maxConcurrent int
-		_ = db.DB.QueryRowContext(ctx,
+		if err := db.DB.QueryRowContext(ctx,
 			`SELECT COALESCE(max_concurrent_tasks, 1) FROM workspaces WHERE id = $1`,
 			payload.WorkspaceID,
-		).Scan(&maxConcurrent)
+		).Scan(&maxConcurrent); err != nil {
+			log.Printf("registry heartbeat: max_concurrent query failed for workspace %s: %v", payload.WorkspaceID, err)
+		}
 		if payload.ActiveTasks < maxConcurrent {
 			// context.WithoutCancel: heartbeat handler's ctx is about to
 			// expire as soon as we return. The drain needs to outlive it.
diff --git a/workspace-server/internal/handlers/terminal_diagnose.go b/workspace-server/internal/handlers/terminal_diagnose.go
index f337ce3db..8528afa0a 100644
--- a/workspace-server/internal/handlers/terminal_diagnose.go
+++ b/workspace-server/internal/handlers/terminal_diagnose.go
@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"context"
 	"fmt"
+	"log"
 	"net/http"
 	"os"
 	"os/exec"
@@ -119,9 +120,11 @@ func (h *TerminalHandler) HandleDiagnose(c *gin.Context) {
 	}
 
 	var instanceID string
-	_ = db.DB.QueryRowContext(ctx,
+	if err := db.DB.QueryRowContext(ctx,
 		`SELECT COALESCE(instance_id, '') FROM workspaces WHERE id = $1`,
-		workspaceID).Scan(&instanceID)
+		workspaceID).Scan(&instanceID); err != nil {
+		log.Printf("terminal diagnose: instance_id query failed for workspace %s: %v", workspaceID, err)
+	}
 
 	var res diagnoseResult
 	if instanceID != "" {
diff --git a/workspace-server/internal/handlers/workspace.go b/workspace-server/internal/handlers/workspace.go
index f6164e646..d466a331a 100644
--- a/workspace-server/internal/handlers/workspace.go
+++ b/workspace-server/internal/handlers/workspace.go
@@ -996,9 +996,11 @@ func (h *WorkspaceHandler) Get(c *gin.Context) {
 			// the client would otherwise see — the actionable signal
 			// is the 410 + hint, not the timestamp.
 			var removedAt time.Time
-			_ = db.DB.QueryRowContext(c.Request.Context(),
+			if err := db.DB.QueryRowContext(c.Request.Context(),
 				`SELECT updated_at FROM workspaces WHERE id = $1`, id,
-			).Scan(&removedAt)
+			).Scan(&removedAt); err != nil {
+				log.Printf("workspace GET: removed_at query failed for %s: %v", id, err)
+			}
 			body := gin.H{
 				"error": "workspace removed",
 				"id":    id,