diff --git a/internal/remote/client.go b/internal/remote/client.go
new file mode 100644
index 0000000..46b044c
--- /dev/null
+++ b/internal/remote/client.go
@@ -0,0 +1,55 @@
+package remote
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strings"
+	"time"
+)
+
+type ClientConfig struct {
+	URL     string
+	Token   string
+	Timeout time.Duration
+}
+
+type Client struct {
+	cfg ClientConfig
+}
+
+func NewClient(cfg ClientConfig) Client {
+	if cfg.Timeout <= 0 {
+		cfg.Timeout = 5 * time.Second
+	}
+	return Client{cfg: cfg}
+}
+
+func (c Client) Report(ctx context.Context, report StatusReport) error {
+	body, err := json.Marshal(report)
+	if err != nil {
+		return err
+	}
+	url := strings.TrimRight(c.cfg.URL, "/") + "/api/v1/status"
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(body))
+	if err != nil {
+		return err
+	}
+	req.Header.Set("Content-Type", "application/json")
+	if c.cfg.Token != "" {
+		req.Header.Set("Authorization", "Bearer "+c.cfg.Token)
+	}
+
+	client := &http.Client{Timeout: c.cfg.Timeout}
+	resp, err := client.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode < 200 || resp.StatusCode > 299 {
+		return fmt.Errorf("remote report failed: %s", resp.Status)
+	}
+	return nil
+}
diff --git a/internal/remote/report.go b/internal/remote/report.go
new file mode 100644
index 0000000..9ba809a
--- /dev/null
+++ b/internal/remote/report.go
@@ -0,0 +1,36 @@
+package remote
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"net"
+	"time"
+)
+
+type StatusReport struct {
+	Hostname       string    `json:"hostname"`
+	IPs            []string  `json:"ips,omitempty"`
+	Agent          string    `json:"agent"`
+	CWD            string    `json:"cwd"`
+	Status         string    `json:"status"`
+	Event          string    `json:"event,omitempty"`
+	ConversationID string    `json:"conversation_id,omitempty"`
+	LastUser       string    `json:"last_user,omitempty"`
+	LastAgent      string    `json:"last_agent,omitempty"`
+	UpdatedAt      time.Time `json:"updated_at"`
+}
+
+func SessionKey(hostname, primaryIP, cwd, agent string) string {
+	sum := sha256.Sum256([]byte(hostname + "\x00" + primaryIP + "\x00" + cwd + "\x00" + agent))
+	return hex.EncodeToString(sum[:])[:32]
+}
+
+func PrimaryIP(ips []string) string {
+	for _, s := range ips {
+		ip := net.ParseIP(s)
+		if ip != nil && ip.To4() != nil {
+			return ip.To4().String()
+		}
+	}
+	return ""
+}
diff --git a/internal/remote/report_test.go b/internal/remote/report_test.go
new file mode 100644
index 0000000..46a107c
--- /dev/null
+++ b/internal/remote/report_test.go
@@ -0,0 +1,49 @@
+package remote
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+)
+
+func TestSessionKeyStable(t *testing.T) {
+	k1 := SessionKey("host", "10.0.0.1", "/proj", "Cursor")
+	k2 := SessionKey("host", "10.0.0.1", "/proj", "Cursor")
+	if k1 != k2 || len(k1) != 32 {
+		t.Fatalf("key=%q len=%d", k1, len(k1))
+	}
+}
+
+func TestClientPostStatus(t *testing.T) {
+	var got StatusReport
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodPost {
+			http.Error(w, "method", http.StatusMethodNotAllowed)
+			return
+		}
+		if r.URL.Path != "/api/v1/status" {
+			http.Error(w, "path", http.StatusNotFound)
+			return
+		}
+		if r.Header.Get("Authorization") != "Bearer secret" {
+			http.Error(w, "auth", http.StatusUnauthorized)
+			return
+		}
+		if err := json.NewDecoder(r.Body).Decode(&got); err != nil {
+			http.Error(w, "decode", http.StatusBadRequest)
+			return
+		}
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte(`{"ok":true}`))
+	}))
+	defer srv.Close()
+
+	c := NewClient(ClientConfig{URL: srv.URL, Token: "secret", Timeout: time.Second})
+	err := c.Report(context.Background(), StatusReport{Hostname: "h", Agent: "Cursor", CWD: "/p", Status: "waiting"})
+	if err != nil || got.Hostname != "h" {
+		t.Fatalf("err=%v got=%+v", err, got)
+	}
+}