feat(config): deliver to always-mTLS Maestro peer edge (CN=maestro gate)

- /config delivery now targets the service's dedicated Maestro peer listener:
  https + authmgmt.MaestroTransport() (Maestro's own mTLS identity, never
  downgraded in dev), port from org.dcntrlized.peer_port label (default 9443)
- extract peerPort() label resolver + unit test
- expose MaestroTransport() on authmgmt for orchestrator-only edges
- spec + comments updated to describe the gated peer edge

src/handlers/config/config.go

@@ -131,6 +131,12 @@ func (h *Handler) Value(w http.ResponseWriter, r *http.Request) {
 		}
 		writeJSON(w, http.StatusOK, map[string]string{"status": "cleared"})
 
+		// Runtime write-back (D6): best-effort "clear" to the running service's
+		// POST /config endpoint. The goroutine is fire-and-forget; the value is
+		// gone from the store either way, and the compose default reapplies at
+		// the next start (or immediately, if the service honors the clear).
+		go libcontainers.DeliverConfigClear(r.Context(), container.ServiceName, field)
+
 	case http.MethodPut:
 		var action valueAction
 		if err := json.NewDecoder(r.Body).Decode(&action); err != nil {

src/lib/authmgmt/client.go

@@ -173,6 +173,15 @@ func PeerTransport() (*http.Transport, error) {
 	return maestroTransport()
 }
 
+// MaestroTransport returns Maestro's own mutual-TLS transport (CN=maestro)
+// unconditionally — dev mode does NOT downgrade it. Orchestrator-only edges
+// that must prove the caller is the orchestrator (e.g. /config delivery, which
+// the service gates to CN=maestro) use this regardless of FORCE_JSON/DEV,
+// since those services keep an always-mTLS peer listener.
+func MaestroTransport() (*http.Transport, error) {
+	return maestroTransport()
+}
+
 // TrustState returns the pending authorizations and the approved trust store.
 func (c *Client) TrustState(ctx context.Context) (*TrustState, error) {
 	var state TrustState

src/lib/containers/configdeliver.go

@@ -1,8 +1,12 @@
 // Package containers implements Maestro's runtime write-back delivery for the
 // Service Config & Secrets theme (D6). When the operator sets or clears a
 // config value via the Settings panel, Maestro delivers it to the running
-// service's POST /config endpoint over the existing mTLS peer edge (same
-// transport as /action/* and manifest fetch).
+// service's POST /config endpoint over an ALWAYS-mTLS edge: Maestro's own
+// identity (CN=maestro) and plain "https" regardless of dev mode, targeted at
+// the service's dedicated peer listener port (label org.dcntrlized.peer_port,
+// default 9443), which the service gates to CN=maestro. A set carries
+// {field, value, type}; a clear carries {field, action:"clear"} — the service
+// owns the schema and branches on what it receives.
 //
 // Delivery is best-effort: failures are logged (with the field name, never
 // the value) and do not prevent the panel write from succeeding. Values always
@@ -23,6 +27,26 @@ import (
 	"git.dcntrlized.org/Dcntrlized/Maestro/lib/logger"
 )
 
+// peerPortLabel is the compose label a service declares to advertise the
+// internal port of its always-mTLS Maestro peer listener.
+const peerPortLabel = "org.dcntrlized.peer_port"
+
+// defaultPeerPort is the fleet-wide default for that listener. Services keep/ve
+// to it unless the label overrides it.
+const defaultPeerPort = "9443"
+
+// peerPort resolves the configured {peer listener port} from a container's
+// compose labels, falling back to the fleet default.
+func peerPort(labels map[string]string) string {
+	if labels == nil {
+		return defaultPeerPort
+	}
+	if p := labels[peerPortLabel]; p != "" {
+		return p
+	}
+	return defaultPeerPort
+}
+
 // ConfigDelivery is one key-value pair to deliver to a running service.
 type ConfigDelivery struct {
 	Field string // manifest config field name
@@ -32,10 +56,12 @@ type ConfigDelivery struct {
 }
 
 // configRequest is the JSON body POSTed to the service's /config endpoint.
+// Action is empty for a set (the existing contract) and "clear" for a clear.
 type configRequest struct {
-	Field string `json:"field"`
-	Value string `json:"value"`
-	Type  string `json:"type"`
+	Field  string `json:"field"`
+	Value  string `json:"value,omitempty"`
+	Type   string `json:"type,omitempty"`
+	Action string `json:"action,omitempty"`
 }
 
 // DeliverConfigValues delivers the given config pairs to the running service
@@ -46,47 +72,6 @@ func DeliverConfigValues(ctx context.Context, serviceName string, items []Config
 	if len(items) == 0 {
 		return
 	}
-
-	dc, err := docker.NewDockerClient()
-	if err != nil {
-		logger.Warn("Config delivery to %s: cannot open docker client: %v", serviceName, err)
-		return
-	}
-	defer dc.Close()
-
-	inspectData, err := docker.ResolveContainer(ctx, dc, serviceName)
-	if err != nil {
-		logger.Debug("Config delivery to %s: service not running or not found (%v); values will apply at next start", serviceName, err)
-		return
-	}
-
-	shouldCache := false
-	network, _, err := docker.ExtractNetworkInfo(ctx, dc, inspectData)
-	if err != nil || !shouldCache {
-		logger.Debug("Config delivery to %s: cannot extract network info; values will apply at next start", serviceName)
-		return
-	}
-
-	port := inspectData.Config.Labels["org.dcntrlized.port"]
-	if port == "" && len(network.Ports) > 0 {
-		port = fmt.Sprintf("%d", network.Ports[0].Guest)
-	}
-	if port == "" {
-		logger.Debug("Config delivery to %s: no service port; values will apply at next start", serviceName)
-		return
-	}
-
-	transport, err := authmgmt.PeerTransport()
-	if err != nil {
-		logger.Warn("Config delivery to %s: cannot build peer transport: %v", serviceName, err)
-		return
-	}
-
-	client := &http.Client{
-		Transport: transport,
-		Timeout:   5 * time.Second,
-	}
-
 	for _, item := range items {
 		body, err := json.Marshal(configRequest{
 			Field: item.Field,
@@ -97,26 +82,81 @@ func DeliverConfigValues(ctx context.Context, serviceName string, items []Config
 			logger.Warn("Config delivery to %s/%s: marshal failed: %v", serviceName, item.Field, err)
 			continue
 		}
-
-		url := fmt.Sprintf("%s://%s:%s/config", authmgmt.Scheme(), network.IPAddress.Address, port)
-		req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(body))
-		if err != nil {
-			logger.Warn("Config delivery to %s/%s: request build failed: %v", serviceName, item.Field, err)
-			continue
-		}
-		req.Header.Set("Content-Type", "application/json")
-
-		resp, err := client.Do(req)
-		if err != nil {
-			logger.Debug("Config delivery to %s/%s: service unreachable (%v); value will apply at next start", serviceName, item.Field, err)
-			continue
-		}
-		resp.Body.Close()
-
-		if resp.StatusCode >= 200 && resp.StatusCode < 300 {
-			logger.Info("Delivered operator config %s/%s to running service %s", serviceName, item.Field, serviceName)
-		} else {
-			logger.Debug("Config delivery to %s/%s: service responded %d; value will apply at next start", serviceName, item.Field, resp.StatusCode)
-		}
+		postConfig(ctx, serviceName, item.Field, "value", body)
 	}
 }
+
+// DeliverConfigClear tells the running service to clear a config field. The
+// service decides what "clear" means (drop the value, fall back to defaults);
+// like sets, it is best-effort and covered by the next start.
+func DeliverConfigClear(ctx context.Context, serviceName, field string) {
+	body, err := json.Marshal(configRequest{Field: field, Action: "clear"})
+	if err != nil {
+		logger.Warn("Config clear delivery to %s/%s: marshal failed: %v", serviceName, field, err)
+		return
+	}
+	postConfig(ctx, serviceName, field, "clear", body)
+}
+
+// postConfig performs one best-effort POST of body to the running service's
+// /config endpoint. NotFound/unreachable cases are logged at debug (the write
+// still applies at next start); transport errors carry the field name only,
+// never a value.
+func postConfig(ctx context.Context, serviceName, field, verb string, body []byte) {
+	dc, err := docker.NewDockerClient()
+	if err != nil {
+		logger.Warn("Config delivery to %s/%s: cannot open docker client: %v", serviceName, field, err)
+		return
+	}
+	defer dc.Close()
+
+	inspectData, err := docker.ResolveContainer(ctx, dc, serviceName)
+	if err != nil {
+		logger.Debug("Config delivery to %s/%s: service not running or not found (%v); will apply at next start", serviceName, field, err)
+		return
+	}
+
+	network, _, err := docker.ExtractNetworkInfo(ctx, dc, inspectData)
+	if err != nil {
+		logger.Debug("Config delivery to %s/%s: cannot extract network info; will apply at next start", serviceName, field)
+		return
+	}
+
+	// /config is served on the service's dedicated Maestro peer listener
+	// (always mTLS, gated to CN=maestro), NOT the RN-facing flat edge. Maestro
+	// presents its own identity and targets the peer port; dev mode does not
+	// downgrade this edge.
+	port := peerPort(inspectData.Config.Labels)
+
+	transport, err := authmgmt.MaestroTransport()
+	if err != nil {
+		logger.Warn("Config delivery to %s/%s: cannot build Maestro peer transport: %v", serviceName, field, err)
+		return
+	}
+
+	client := &http.Client{
+		Transport: transport,
+		Timeout:   5 * time.Second,
+	}
+
+	url := fmt.Sprintf("https://%s:%s/config", network.IPAddress.Address, port)
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(body))
+	if err != nil {
+		logger.Warn("Config delivery to %s/%s: request build failed: %v", serviceName, field, err)
+		return
+	}
+	req.Header.Set("Content-Type", "application/json")
+
+	resp, err := client.Do(req)
+	if err != nil {
+		logger.Debug("Config delivery to %s/%s: service unreachable (%v); will apply at next start", serviceName, field, err)
+		return
+	}
+	resp.Body.Close()
+
+	if resp.StatusCode >= 200 && resp.StatusCode < 300 {
+		logger.Info("Delivered operator config %s/%s (%s) to running service", serviceName, field, verb)
+	} else {
+		logger.Debug("Config delivery to %s/%s: service responded %d; will apply at next start", serviceName, field, resp.StatusCode)
+	}
+}

src/lib/containers/configdeliver_test.go

@@ -0,0 +1,39 @@
+// Copyright (C) 2026 Dcntrlized
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published
+// by the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package containers
+
+import "testing"
+
+func TestPeerPort(t *testing.T) {
+	tests := []struct {
+		name   string
+		labels map[string]string
+		want   string
+	}{
+		{"nil labels fall back to default", nil, defaultPeerPort},
+		{"empty labels fall back to default", map[string]string{}, defaultPeerPort},
+		{"label present wins", map[string]string{"org.dcntrlized.peer_port": "9000"}, "9000"},
+		{"empty label value falls back to default", map[string]string{"org.dcntrlized.peer_port": ""}, defaultPeerPort},
+		{"unrelated labels fall back to default", map[string]string{"org.dcntrlized.port": "8080"}, defaultPeerPort},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := peerPort(tt.labels); got != tt.want {
+				t.Fatalf("peerPort(%v) = %q, want %q", tt.labels, got, tt.want)
+			}
+		})
+	}
+}