diff --git a/workspace.go b/workspace.go
index 0d8598f..19adca9 100644
--- a/workspace.go
+++ b/workspace.go
@@ -1,9 +1,18 @@
 package main
 
 import (
+	"bufio"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+
 	i3 "go.i3wm.org/i3/v4"
 )
 
+const maxPPIDDepth = 20
+
 // X11PIDResolver abstrait la lecture de _NET_WM_PID pour testabilite.
 type X11PIDResolver interface {
 	GetPID(windowID int64) (int, error)
@@ -16,17 +25,77 @@ type I3TreeProvider interface {
 
 // ReadPPID lit le PPid depuis /proc/PID/status. procDir injectable pour les tests.
 func ReadPPID(procDir string, pid int) (int, error) {
-	return 0, nil
+	statusPath := filepath.Join(procDir, strconv.Itoa(pid), "status")
+	f, err := os.Open(statusPath)
+	if err != nil {
+		return 0, err
+	}
+	defer f.Close()
+
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if strings.HasPrefix(line, "PPid:") {
+			fields := strings.Fields(line)
+			if len(fields) < 2 {
+				return 0, fmt.Errorf("malformed PPid line: %q", line)
+			}
+			return strconv.Atoi(fields[1])
+		}
+	}
+	return 0, fmt.Errorf("PPid not found in %s", statusPath)
 }
 
 // ResolveWorkspace remonte la chaine PPID depuis claudePID jusqu'a trouver
-// un PID connu dans terminalWorkspaces. Max 20 niveaux.
+// un PID connu dans terminalWorkspaces. Max 20 niveaux pour eviter les boucles.
 func ResolveWorkspace(procDir string, claudePID int, terminalWorkspaces map[int]string) string {
+	current := claudePID
+	for depth := 0; depth < maxPPIDDepth; depth++ {
+		ppid, err := ReadPPID(procDir, current)
+		if err != nil || ppid <= 0 {
+			return ""
+		}
+		if ws, ok := terminalWorkspaces[ppid]; ok {
+			return ws
+		}
+		current = ppid
+	}
 	return ""
 }
 
-// BuildTerminalWorkspaceMap construit la map terminalPID -> workspaceName.
-// Utilise i3 GetTree + X11 _NET_WM_PID.
+// BuildTerminalWorkspaceMap construit la map terminalPID -> workspaceName
+// en parcourant l'arbre i3 et en resolvant le PID via X11 _NET_WM_PID.
 func BuildTerminalWorkspaceMap(tree I3TreeProvider, x11 X11PIDResolver) (map[int]string, error) {
-	return nil, nil
+	t, err := tree.GetTree()
+	if err != nil {
+		return nil, err
+	}
+
+	result := make(map[int]string)
+	walkI3Tree(t.Root, "", x11, result)
+	return result, nil
+}
+
+func walkI3Tree(node *i3.Node, currentWorkspace string, x11 X11PIDResolver, result map[int]string) {
+	if node == nil {
+		return
+	}
+
+	if node.Type == i3.WorkspaceNode {
+		currentWorkspace = node.Name
+	}
+
+	if node.Window > 0 && currentWorkspace != "" {
+		pid, err := x11.GetPID(node.Window)
+		if err == nil && pid > 0 {
+			result[pid] = currentWorkspace
+		}
+	}
+
+	for _, child := range node.Nodes {
+		walkI3Tree(child, currentWorkspace, x11, result)
+	}
+	for _, child := range node.FloatingNodes {
+		walkI3Tree(child, currentWorkspace, x11, result)
+	}
 }
diff --git a/x11_resolver.go b/x11_resolver.go
new file mode 100644
index 0000000..a5d7f00
--- /dev/null
+++ b/x11_resolver.go
@@ -0,0 +1,42 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/BurntSushi/xgb/xproto"
+	"github.com/BurntSushi/xgbutil"
+	"github.com/BurntSushi/xgbutil/ewmh"
+)
+
+// RealX11Resolver lit _NET_WM_PID via la connexion X11.
+type RealX11Resolver struct {
+	xu *xgbutil.XUtil
+}
+
+// NewRealX11Resolver ouvre une connexion X11. Retourne une erreur si $DISPLAY est absent.
+func NewRealX11Resolver() (*RealX11Resolver, error) {
+	if os.Getenv("DISPLAY") == "" {
+		return nil, fmt.Errorf("DISPLAY not set, cannot resolve X11 PIDs")
+	}
+	xu, err := xgbutil.NewConn()
+	if err != nil {
+		return nil, fmt.Errorf("X11 connection failed: %w", err)
+	}
+	return &RealX11Resolver{xu: xu}, nil
+}
+
+func (r *RealX11Resolver) GetPID(windowID int64) (int, error) {
+	pid, err := ewmh.WmPidGet(r.xu, xproto.Window(windowID))
+	if err != nil {
+		return 0, err
+	}
+	return int(pid), nil
+}
+
+// Close ferme la connexion X11.
+func (r *RealX11Resolver) Close() {
+	if r.xu != nil {
+		r.xu.Conn().Close()
+	}
+}