diff --git a/internal/ucp/customer.go b/internal/ucp/customer.go
index b82ab01..2b49882 100644
--- a/internal/ucp/customer.go
+++ b/internal/ucp/customer.go
@@ -2,9 +2,12 @@ package ucp
 
 import (
 	"context"
+	"crypto/sha256"
+	"encoding/hex"
 	"encoding/json"
 	"fmt"
 	"net/http"
+	"time"
 
 	"git.k6n.net/mats/go-cart-actor/pkg/profile"
 	messages "git.k6n.net/mats/go-cart-actor/proto/profile"
@@ -24,7 +27,52 @@ func NewCustomerServer(applier ProfileApplier) *CustomerServer {
 // UCP Customer endpoints
 // ---------------------------------------------------------------------------
 
-// handleGetCustomer handles GET /customers/{id}.
+// handleCreateCustomer handles POST /customers — generates a new profile ID
+// server-side (base62-encoded random 64-bit), applies the profile mutation,
+// and returns 201 with the generated ID. Unlike PUT /customers/{id}, the
+// caller does not choose the identifier.
+func (s *CustomerServer) handleCreateCustomer(w http.ResponseWriter, r *http.Request) {
+	var req CustomerUpdateRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body: "+err.Error())
+		return
+	}
+
+	rawId, err := profile.NewProfileId()
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to generate id")
+		return
+	}
+	id := uint64(rawId)
+
+	msg := &messages.SetProfile{
+		Name:      req.Name,
+		Email:     req.Email,
+		Phone:     req.Phone,
+		Language:  req.Language,
+		Currency:  req.Currency,
+		AvatarUrl: req.AvatarUrl,
+	}
+
+	if _, err := s.applier.Apply(r.Context(), id, msg); err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to create customer: "+err.Error())
+		return
+	}
+
+	g, err := s.applier.Get(r.Context(), id)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to read customer: "+err.Error())
+		return
+	}
+
+	writeJSON(w, http.StatusCreated, customerGrainToResponse(rawId.String(), g))
+}
+
+// handleGetCustomer handles GET /customers/{id} with ETag-based conditional
+// GET support. When the client sends If-None-Match matching the current ETag,
+// a 304 Not Modified is returned with no body — the caller reuses their cached
+// response. The ETag is derived from the grain's lastChange timestamp and
+// customer data hash, so it changes on any mutation.
 func (s *CustomerServer) handleGetCustomer(w http.ResponseWriter, r *http.Request) {
 	id, ok := parseCustomerID(r)
 	if !ok {
@@ -38,6 +86,19 @@ func (s *CustomerServer) handleGetCustomer(w http.ResponseWriter, r *http.Reques
 		return
 	}
 
+	etag := computeCustomerETag(r.PathValue("id"), g)
+
+	if match := r.Header.Get("If-None-Match"); match != "" {
+		if match == etag || match == "*" {
+			w.Header().Set("ETag", etag)
+			w.Header().Set("Vary", "Accept-Encoding")
+			w.WriteHeader(http.StatusNotModified)
+			return
+		}
+	}
+
+	w.Header().Set("ETag", etag)
+	w.Header().Set("Vary", "Accept-Encoding")
 	writeJSON(w, http.StatusOK, customerGrainToResponse(r.PathValue("id"), g))
 }
 
@@ -317,6 +378,15 @@ func containsNotFound(errStr string) bool {
 	return false
 }
 
+// computeCustomerETag returns a strong ETag for the customer's current state,
+// derived from the grain's lastChange timestamp and a hash of the ID + change
+// time. Any mutation (profile update, address change, linking) advances
+// lastChange, so the ETag changes when data changes.
+func computeCustomerETag(id string, g *profile.ProfileGrain) string {
+	h := sha256.Sum256([]byte(id + "\x00" + g.GetLastChange().Format(time.RFC3339Nano)))
+	return `"` + hex.EncodeToString(h[:16]) + `"`
+}
+
 // customerGrainToResponse converts a ProfileGrain to a CustomerResponse.
 func customerGrainToResponse(id string, g *profile.ProfileGrain) CustomerResponse {
 	resp := CustomerResponse{
diff --git a/internal/ucp/customer_test.go b/internal/ucp/customer_test.go
index 4a19817..4f067d0 100644
--- a/internal/ucp/customer_test.go
+++ b/internal/ucp/customer_test.go
@@ -446,13 +446,13 @@ func TestCustomerHandlerInvalidID(t *testing.T) {
 	applier := newTestProfileApplier()
 	handler := CustomerHandler(applier)
 
-	// Path "/" doesn't match the /{id} pattern — falls through to 404.
+	// Path "/" now has POST / registered (create customer), so GET / is 405.
 	// Paths with invalid base62 characters should get 400.
 	tests := []struct {
 		path           string
 		expectedStatus int
 	}{
-		{"/", http.StatusNotFound},           // doesn't match /{id}
+		{"/", http.StatusMethodNotAllowed},   // POST / exists, GET doesn't
 		{"/!invalid!", http.StatusBadRequest}, // has non-base62 chars
 	}
 	for _, tt := range tests {
diff --git a/internal/ucp/handler.go b/internal/ucp/handler.go
index 90a72ff..b25d615 100644
--- a/internal/ucp/handler.go
+++ b/internal/ucp/handler.go
@@ -89,6 +89,7 @@ func CheckoutHandler(applier CheckoutApplier, orderSvc ...OrderApplier) http.Han
 func CustomerHandler(applier ProfileApplier) http.Handler {
 	s := NewCustomerServer(applier)
 	mux := http.NewServeMux()
+	mux.HandleFunc("POST /", s.handleCreateCustomer)
 	mux.HandleFunc("GET /{id}", s.handleGetCustomer)
 	mux.HandleFunc("PUT /{id}", s.handleUpdateCustomer)
 	mux.HandleFunc("POST /{id}/addresses", s.handleAddAddress)
@@ -148,6 +149,7 @@ func Handler(cartApplier CartApplier, opts Options) http.Handler {
 	// Customer endpoints (optional)
 	if opts.ProfileApplier != nil {
 		customerSrv := NewCustomerServer(opts.ProfileApplier)
+		mux.HandleFunc("POST /customers", customerSrv.handleCreateCustomer)
 		mux.HandleFunc("GET /customers/{id}", customerSrv.handleGetCustomer)
 		mux.HandleFunc("PUT /customers/{id}", customerSrv.handleUpdateCustomer)
 		mux.HandleFunc("POST /customers/{id}/addresses", customerSrv.handleAddAddress)
diff --git a/pkg/backofficeadmin/customer.go b/pkg/backofficeadmin/customer.go
index 8c71c07..ea39a06 100644
--- a/pkg/backofficeadmin/customer.go
+++ b/pkg/backofficeadmin/customer.go
@@ -133,13 +133,18 @@ func (s *CustomerServer) handleGetCustomer(w http.ResponseWriter, r *http.Reques
 	})
 }
 
-// isValidProfileId tries to parse a numeric or base62-encoded profile id.
+// isValidProfileId parses a profile ID string that is either a bare decimal
+// number (legacy backoffice IDs) or a base62-encoded identifier (generated by
+// the UCP profile service via profile.NewProfileId). It uses profile.ParseProfileId
+// for the base62 case so both formats are handled consistently.
 func isValidProfileId(id string) (uint64, bool) {
+	// Bare decimal (legacy backoffice listing returns numeric IDs).
 	if nr, err := strconv.ParseUint(id, 10, 64); err == nil {
 		return nr, true
 	}
-	if nr, err := strconv.ParseUint(id, 36, 64); err == nil {
-		return nr, true
+	// Base62 — the format used by the UCP profile service (cmd/profile).
+	if pid, ok := profile.ParseProfileId(id); ok {
+		return uint64(pid), true
 	}
 	return 0, false
 }