feat(scheduling): node tags + service placement_tags affinity (#58)

Operator-set node labels (node_agents.tags) gate which nodes a service
may schedule onto: services.placement_tags requires every listed tag.
auto and spread filter eligible agents by tags; tags are re-evaluated
each reconcile so retagging a node re-spreads replicas. Pin + tags and
local + tags rejected; empty array clears the requirement.

Surfaces: --placement-tags on services create/update, nodes update
--tags, MCP args, OpenAPI, node-detail tag editor, service-detail
placement-tags input.

Generated with [Devin](https://devin.ai)

Co-authored-by: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/backend/internal/api/agents.go

@@ -42,6 +42,9 @@ type NodeAgent struct {
 	LastHeartbeat time.Time              `json:"last_heartbeat"`
 	AutoPrune     bool                   `json:"auto_prune"`
 	Schedulable   bool                   `json:"schedulable"`
+	// Tags are operator-set placement labels; services with placement_tags
+	// only schedule onto agents carrying every required tag.
+	Tags          []string               `json:"tags"`
 	CreatedAt     time.Time              `json:"created_at"`
 	UpdatedAt     time.Time              `json:"updated_at"`
 	Metadata      map[string]interface{} `json:"metadata"`
@@ -242,10 +245,15 @@ func (h *NodeAgentHandler) ListNodeOptions(c *gin.Context) {
 	}
 	options := make([]gin.H, 0, len(rows))
 	for _, row := range rows {
+		var tags []string
+		if len(row.Tags) > 0 {
+			_ = json.Unmarshal(row.Tags, &tags)
+		}
 		options = append(options, gin.H{
 			"id":     row.ID,
 			"name":   row.Name,
 			"status": row.Status.String,
+			"tags":   tags,
 		})
 	}
 	c.JSON(http.StatusOK, gin.H{"nodes": options})
@@ -262,6 +270,7 @@ func agentFromRow(row sqlcdb.NodeAgent) NodeAgent {
 		Version:     row.Version.String,
 		AutoPrune:   row.AutoPrune,
 		Schedulable: row.Schedulable,
+		Tags:        []string{},
 		Metadata:    map[string]interface{}{},
 	}
 	if row.LastHeartbeat.Valid {
@@ -276,6 +285,9 @@ func agentFromRow(row sqlcdb.NodeAgent) NodeAgent {
 	unmarshalRaw(row.Capabilities, &agent.Capabilities)
 	unmarshalRaw(row.Resources, &agent.Resources)
 	unmarshalRaw(row.Metadata, &agent.Metadata)
+	if len(row.Tags) > 0 {
+		_ = json.Unmarshal(row.Tags, &agent.Tags)
+	}
 	return agent
 }
 
@@ -546,7 +558,26 @@ func (h *NodeAgentHandler) UpdateAgent(c *gin.Context) {
 		return
 	}
 
-	c.JSON(http.StatusOK, gin.H{"agent": agentFromRow(updated)})
+	// Tags persist through their own column write — UpdateAgent keeps the
+	// register-path signature untouched.
+	resp := agentFromRow(updated)
+	if raw, ok := updates["tags"]; ok {
+		var tags []string
+		if b, mErr := json.Marshal(raw); mErr == nil {
+			_ = json.Unmarshal(b, &tags)
+		}
+		tags = normalizePlacementTags(tags)
+		if err := h.q.SetAgentTags(ctx, sqlcdb.SetAgentTagsParams{
+			ID:      id,
+			Column2: json.RawMessage(tagsJSON(tags)),
+		}); err != nil {
+			c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to update agent tags"})
+			return
+		}
+		resp.Tags = tags
+	}
+
+	c.JSON(http.StatusOK, gin.H{"agent": resp})
 }
 
 // applyAgentUpdates merges whitelisted keys from an arbitrary update map.

app/backend/internal/api/noderunner.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"crypto/sha256"
 	"database/sql"
+	"encoding/json"
 	"fmt"
 	"strconv"
 	"strings"
@@ -56,11 +57,18 @@ func (r *agentNodeRunner) ReconcileOnNode(ctx context.Context, spec deployment.R
 // sorted by id. Replicas wrap when they outnumber nodes. The local host is
 // not a spread target — pin "local" or leave unset for local execution.
 func (r *agentNodeRunner) ReconcileSpread(ctx context.Context, spec deployment.RuntimeSpec) (*deployment.RuntimeState, error) {
-	agents, err := r.q.ListSchedulableAgents(ctx)
+	tagsRaw, _ := json.Marshal(spec.PlacementTags)
+	if len(spec.PlacementTags) == 0 {
+		tagsRaw = []byte("[]")
+	}
+	agents, err := r.q.ListSchedulableAgentsMatching(ctx, json.RawMessage(tagsRaw))
 	if err != nil {
 		return nil, fmt.Errorf("list schedulable nodes: %w", err)
 	}
 	if len(agents) == 0 {
+		if len(spec.PlacementTags) > 0 {
+			return nil, fmt.Errorf("no online schedulable nodes carry placement tags %v — tag a node or relax the requirement", spec.PlacementTags)
+		}
 		return nil, fmt.Errorf("no online schedulable nodes — connect an agent or unset spread")
 	}
 	return r.reconcileOnAgents(ctx, spec, func(i int) string {
@@ -68,6 +76,22 @@ func (r *agentNodeRunner) ReconcileSpread(ctx context.Context, spec deployment.R
 	})
 }
 
+// ReconcileAuto resolves the least-loaded online agent matching the
+// service's placement tags and reconciles every replica onto it. Stale
+// replicas on other agents retire through reconcileOnAgents — a service
+// follows its tags when the matching set changes.
+func (r *agentNodeRunner) ReconcileAuto(ctx context.Context, spec deployment.RuntimeSpec) (*deployment.RuntimeState, error) {
+	tagsRaw, _ := json.Marshal(spec.PlacementTags)
+	if len(spec.PlacementTags) == 0 {
+		tagsRaw = []byte("[]")
+	}
+	agentID, err := r.q.PickLeastLoadedAgentMatching(ctx, json.RawMessage(tagsRaw))
+	if err != nil {
+		return nil, fmt.Errorf("no online nodes carry placement tags %v", spec.PlacementTags)
+	}
+	return r.reconcileOnAgents(ctx, spec, func(int) string { return agentID })
+}
+
 // RemoteRuntimeState reads the service's remote replicas from inventory.
 // Rows only carry the last dispatched state — the agent doesn't stream
 // container events — so "running" means "last create succeeded".
@@ -344,16 +368,25 @@ func (r *agentNodeRunner) enqueueAndWait(ctx context.Context, agentID, container
 }
 
 // resolveNodePin validates or resolves a node_id request value. "auto" picks
-// the least-loaded online agent; "" / "local" clears the pin.
-func resolveNodePin(ctx context.Context, db *database.DB, requested string) (string, error) {
+// the least-loaded online agent that carries every required placement tag;
+// "" / "local" clears the pin. An explicit pin bypasses tag filtering —
+// the operator is overriding placement on purpose.
+func resolveNodePin(ctx context.Context, db *database.DB, requested string, requiredTags []string) (string, error) {
 	requested = strings.TrimSpace(requested)
 	if requested == "" || requested == "local" {
 		return "", nil
 	}
 	q := sqlcdb.New(db.DB)
 	if requested == "auto" {
-		id, err := q.PickLeastLoadedAgent(ctx)
+		tagsRaw, _ := json.Marshal(requiredTags)
+		if len(requiredTags) == 0 {
+			tagsRaw = []byte("[]")
+		}
+		id, err := q.PickLeastLoadedAgentMatching(ctx, json.RawMessage(tagsRaw))
 		if err != nil {
+			if len(requiredTags) > 0 {
+				return "", fmt.Errorf("no online nodes carry placement tags %v", requiredTags)
+			}
 			return "", fmt.Errorf("no online nodes available")
 		}
 		return id, nil

app/backend/internal/api/runtime.go

@@ -94,6 +94,7 @@ func serviceRuntimeSpec(db *database.DB, service Service) (deployment.RuntimeSpe
 		RestartPolicy: service.RestartPolicy,
 		NodeID:        serviceNodeID(db, service.ID),
 		Spread:        serviceSpread(db, service.ID),
+		PlacementTags: servicePlacementTags(db, service.ID),
 	}
 	// Best effort: reuse the host port from the last live deployment so the
 	// public URL survives restarts. Column exists post-migration; older DBs

app/backend/internal/api/services.go

@@ -55,9 +55,12 @@ type Service struct {
 	NodeName string `json:"node_name,omitempty" db:"-"`
 	// Spread distributes replicas across every online, schedulable agent.
 	// Mutually exclusive with an explicit NodeID pin.
-	Spread    bool      `json:"spread" db:"-"`
-	CreatedAt time.Time `json:"created_at" db:"created_at"`
-	UpdatedAt time.Time `json:"updated_at" db:"updated_at"`
+	Spread bool `json:"spread" db:"-"`
+	// PlacementTags restrict auto/spread candidates to agents carrying all
+	// listed tags. An explicit pin overrides them — pin + tags is rejected.
+	PlacementTags []string  `json:"placement_tags,omitempty" db:"-"`
+	CreatedAt     time.Time `json:"created_at" db:"created_at"`
+	UpdatedAt     time.Time `json:"updated_at" db:"updated_at"`
 }
 
 // loadServiceSleep fills the sleep-mode columns, which live outside the
@@ -91,12 +94,51 @@ func serviceSpread(db *database.DB, serviceID uuid.UUID) bool {
 	return false
 }
 
-// loadServiceNode fills the pin + spread + the agent's display name for
-// responses.
+// servicePlacementTags reads the placement_tags column with the lazy pattern.
+func servicePlacementTags(db *database.DB, serviceID uuid.UUID) []string {
+	var raw []byte
+	if err := db.QueryRow(`SELECT placement_tags FROM services WHERE id = $1`, serviceID).Scan(&raw); err != nil {
+		return nil
+	}
+	var tags []string
+	if err := json.Unmarshal(raw, &tags); err != nil {
+		return nil
+	}
+	return tags
+}
+
+// normalizePlacementTags trims, lowercases, and dedupes tag input. Tags are
+// matched verbatim against node_agents.tags.
+func normalizePlacementTags(tags []string) []string {
+	seen := map[string]bool{}
+	out := make([]string, 0, len(tags))
+	for _, t := range tags {
+		t = strings.ToLower(strings.TrimSpace(t))
+		if t == "" || seen[t] {
+			continue
+		}
+		seen[t] = true
+		out = append(out, t)
+	}
+	return out
+}
+
+// tagsJSON marshals a tag list for a jsonb column; empty stays an array, not null.
+func tagsJSON(tags []string) []byte {
+	if len(tags) == 0 {
+		return []byte("[]")
+	}
+	raw, _ := json.Marshal(tags)
+	return raw
+}
+
+// loadServiceNode fills the pin + spread + placement tags + the agent's
+// display name for responses.
 func loadServiceNode(db *database.DB, s *Service) {
 	var name sql.NullString
 	s.NodeID = serviceNodeID(db, s.ID)
 	s.Spread = serviceSpread(db, s.ID)
+	s.PlacementTags = servicePlacementTags(db, s.ID)
 	if s.NodeID == "" {
 		return
 	}
@@ -188,6 +230,9 @@ type CreateServiceRequest struct {
 	// Spread distributes replicas across every online, schedulable agent.
 	// Mutually exclusive with an explicit node pin.
 	Spread *bool `json:"spread"`
+	// PlacementTags restrict auto/spread candidates to agents carrying all
+	// listed tags. Mutually exclusive with an explicit node pin.
+	PlacementTags []string `json:"placement_tags"`
 }
 
 // UpdateServiceRequest represents a request to update a service
@@ -222,6 +267,10 @@ type UpdateServiceRequest struct {
 	// Spread toggles multi-node replica distribution; pointer so false is
 	// a real update, not a missing field.
 	Spread *bool `json:"spread"`
+	// PlacementTags restrict auto/spread candidates to agents carrying all
+	// listed tags; pointer so [] clears the requirement. Mutually exclusive
+	// with an explicit node pin.
+	PlacementTags *[]string `json:"placement_tags"`
 }
 
 // handleGetServices retrieves all services for a project
@@ -465,12 +514,17 @@ func handleCreateService(c *gin.Context) {
 	if req.Spread != nil {
 		service.Spread = *req.Spread
 	}
+	service.PlacementTags = normalizePlacementTags(req.PlacementTags)
 	if req.NodeID != "" {
-		if service.Spread && req.NodeID != "auto" {
+		if service.Spread && req.NodeID != "auto" && req.NodeID != "local" {
 			c.JSON(http.StatusBadRequest, gin.H{"error": "spread and an explicit node pin are mutually exclusive", "code": "VALIDATION"})
 			return
 		}
-		nodeID, nodeErr := resolveNodePin(c.Request.Context(), db.(*database.DB), req.NodeID)
+		if len(service.PlacementTags) > 0 && req.NodeID != "auto" {
+			c.JSON(http.StatusBadRequest, gin.H{"error": "placement tags only apply to remote placement — set node_id=\"auto\" or omit it", "code": "VALIDATION"})
+			return
+		}
+		nodeID, nodeErr := resolveNodePin(c.Request.Context(), db.(*database.DB), req.NodeID, service.PlacementTags)
 		if nodeErr != nil {
 			c.JSON(http.StatusBadRequest, gin.H{"error": nodeErr.Error(), "code": "VALIDATION"})
 			return
@@ -488,9 +542,9 @@ func handleCreateService(c *gin.Context) {
 				 git_repo, git_branch, build_path, cpu, memory, replicas, port, domain,
 				 healthcheck_path, restart_policy, volumes,
 				 builder, cpu_reserve, memory_reserve, static_build_cmd, static_dir,
-				 node_id, spread, created_at, updated_at)
+				 node_id, spread, placement_tags, created_at, updated_at)
 			VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16, $17, $18, $19, $20, $21, $22, $23, $24, $25, $26,
-					$27, $28, $29, $30, $31, $32, $33, $34, $35)`,
+					$27, $28, $29, $30, $31, $32, $33, $34, $35, $36)`,
 		service.ID, service.ProjectID, service.Name, environmentID, service.Type,
 		sourceType, firstNonEmpty(service.GitRepo, service.Image), service.Image,
 		"", service.Command, service.Type, service.Status, service.Image, service.Command,
@@ -500,6 +554,7 @@ func handleCreateService(c *gin.Context) {
 		service.StaticBuildCmd, service.StaticDir,
 		sql.NullString{String: service.NodeID, Valid: service.NodeID != ""},
 		service.Spread,
+		tagsJSON(service.PlacementTags),
 		service.CreatedAt, service.UpdatedAt,
 	)
 
@@ -807,13 +862,22 @@ func handleUpdateService(c *gin.Context) {
 	} else {
 		existingService.Spread = serviceSpread(db.(*database.DB), serviceID)
 	}
+	if req.PlacementTags != nil {
+		existingService.PlacementTags = normalizePlacementTags(*req.PlacementTags)
+	} else {
+		existingService.PlacementTags = servicePlacementTags(db.(*database.DB), serviceID)
+	}
 	if req.NodeID != nil {
 		nodeValue := strings.TrimSpace(*req.NodeID)
 		if existingService.Spread && nodeValue != "" && nodeValue != "auto" && nodeValue != "local" {
 			c.JSON(http.StatusBadRequest, gin.H{"error": "spread and an explicit node pin are mutually exclusive — set spread=false first", "code": "VALIDATION"})
 			return
 		}
-		nodeID, nodeErr := resolveNodePin(c.Request.Context(), db.(*database.DB), nodeValue)
+		if len(existingService.PlacementTags) > 0 && nodeValue != "" && nodeValue != "auto" {
+			c.JSON(http.StatusBadRequest, gin.H{"error": "service has placement tags — clear them (placement_tags=[]) before pinning or going local", "code": "VALIDATION"})
+			return
+		}
+		nodeID, nodeErr := resolveNodePin(c.Request.Context(), db.(*database.DB), nodeValue, existingService.PlacementTags)
 		if nodeErr != nil {
 			c.JSON(http.StatusBadRequest, gin.H{"error": nodeErr.Error(), "code": "VALIDATION"})
 			return
@@ -826,6 +890,10 @@ func handleUpdateService(c *gin.Context) {
 		c.JSON(http.StatusBadRequest, gin.H{"error": "service already has an explicit node pin — clear it (node_id=\"local\") before enabling spread", "code": "VALIDATION"})
 		return
 	}
+	if len(existingService.PlacementTags) > 0 && existingService.NodeID != "" {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "service already has an explicit node pin — clear it (node_id=\"local\") before setting placement tags", "code": "VALIDATION"})
+		return
+	}
 
 	existingService.UpdatedAt = time.Now()
 
@@ -838,7 +906,8 @@ func handleUpdateService(c *gin.Context) {
 				restart_policy = $15, volumes = COALESCE($17::jsonb, volumes), updated_at = $16,
 				builder = $19, cpu_reserve = $20, memory_reserve = $21,
 				static_build_cmd = $22, static_dir = $23,
-				sleep_enabled = $24, sleep_idle_minutes = $25, node_id = $26, spread = $27
+				sleep_enabled = $24, sleep_idle_minutes = $25, node_id = $26, spread = $27,
+				placement_tags = $28::jsonb
 			WHERE id = $18`,
 		existingService.Name, existingService.Type, existingService.Image, existingService.Command,
 		existingService.Environment, existingService.GitRepo, existingService.GitBranch,
@@ -851,6 +920,7 @@ func handleUpdateService(c *gin.Context) {
 		existingService.SleepEnabled, existingService.SleepIdleMinutes,
 		sql.NullString{String: existingService.NodeID, Valid: existingService.NodeID != ""},
 		existingService.Spread,
+		tagsJSON(existingService.PlacementTags),
 	)
 
 	if err != nil {