diff --git a/internal/acp/handlers/handlers.go b/internal/acp/handlers/handlers.go
index 3851160..6ee012f 100644
--- a/internal/acp/handlers/handlers.go
+++ b/internal/acp/handlers/handlers.go
@@ -49,6 +49,3 @@ func NewFsHandler() *FsHandler {
 	return &FsHandler{Read: NewFsReadHandler(), Write: NewFsWriteHandler()}
 }
 
-// PermissionHandler is the placeholder for session/request_permission.
-// Fields and methods are added in Task D5.
-type PermissionHandler struct{}
diff --git a/internal/acp/handlers/server_permission.go b/internal/acp/handlers/server_permission.go
new file mode 100644
index 0000000..7fc100c
--- /dev/null
+++ b/internal/acp/handlers/server_permission.go
@@ -0,0 +1,67 @@
+package handlers
+
+import (
+	"context"
+	"encoding/json"
+	"strings"
+)
+
+// PermissionHandler handles session/request_permission (spec §5.1).
+//
+// MVP behaviour (decision §1 #8 + §10 misc #1): fs.* tool calls are answered
+// directly by the server (so they never reach this handler). Other tool calls
+// default to "reject_once" — fully automated, no human-in-the-loop.
+type PermissionHandler struct{}
+
+// NewPermissionHandler constructs a PermissionHandler.
+func NewPermissionHandler() *PermissionHandler { return &PermissionHandler{} }
+
+type permissionParams struct {
+	SessionID string          `json:"sessionId"`
+	ToolCall  json.RawMessage `json:"toolCall"`
+	Options   []permOption    `json:"options"`
+}
+
+type permOption struct {
+	ID   string `json:"id"`
+	Name string `json:"name,omitempty"`
+}
+
+type permOutcomeSelected struct {
+	ID string `json:"id"`
+}
+
+type permOutcome struct {
+	Selected *permOutcomeSelected `json:"selected,omitempty"`
+}
+
+type permResult struct {
+	Outcome permOutcome `json:"outcome"`
+}
+
+// Handle picks the first option whose ID looks like a "reject" choice; if none
+// matches, falls back to the first option. Aligns with spec §10 misc #4
+// ("default reject").
+func (h *PermissionHandler) Handle(_ context.Context, _ SessionContext, paramsJSON json.RawMessage) FsResult {
+	var p permissionParams
+	if err := json.Unmarshal(paramsJSON, &p); err != nil {
+		return FsResult{Err: &FsError{Code: -32602, Message: "invalid params: " + err.Error()}}
+	}
+	chosen := ""
+	for _, opt := range p.Options {
+		lc := strings.ToLower(opt.ID)
+		if strings.Contains(lc, "reject") || strings.Contains(lc, "deny") || strings.Contains(lc, "no") {
+			chosen = opt.ID
+			break
+		}
+	}
+	if chosen == "" && len(p.Options) > 0 {
+		chosen = p.Options[0].ID
+	}
+	if chosen == "" {
+		out, _ := json.Marshal(permResult{Outcome: permOutcome{}})
+		return FsResult{OK: out}
+	}
+	out, _ := json.Marshal(permResult{Outcome: permOutcome{Selected: &permOutcomeSelected{ID: chosen}}})
+	return FsResult{OK: out}
+}
diff --git a/internal/acp/handlers/server_permission_test.go b/internal/acp/handlers/server_permission_test.go
new file mode 100644
index 0000000..70289a8
--- /dev/null
+++ b/internal/acp/handlers/server_permission_test.go
@@ -0,0 +1,68 @@
+package handlers_test
+
+import (
+	"context"
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/yan1h/agent-coding-workflow/internal/acp/handlers"
+)
+
+func TestPermission_AutoReject(t *testing.T) {
+	t.Parallel()
+	h := handlers.NewPermissionHandler()
+	params := mustJSON(t, map[string]any{
+		"sessionId": "x",
+		"toolCall":  map[string]any{"name": "shell.exec"},
+		"options": []any{
+			map[string]any{"id": "allow_once"},
+			map[string]any{"id": "reject_once"},
+		},
+	})
+	res := h.Handle(context.Background(), handlers.SessionContext{}, params)
+	require.Nil(t, res.Err)
+
+	var out struct {
+		Outcome struct {
+			Selected struct {
+				ID string `json:"id"`
+			} `json:"selected"`
+		} `json:"outcome"`
+	}
+	require.NoError(t, json.Unmarshal(res.OK, &out))
+	assert.Equal(t, "reject_once", out.Outcome.Selected.ID)
+}
+
+func TestPermission_NoRejectOption_FallbackFirst(t *testing.T) {
+	t.Parallel()
+	h := handlers.NewPermissionHandler()
+	params := mustJSON(t, map[string]any{
+		"sessionId": "x",
+		"options": []any{
+			map[string]any{"id": "allow_once"},
+			map[string]any{"id": "allow_session"},
+		},
+	})
+	res := h.Handle(context.Background(), handlers.SessionContext{}, params)
+	var out struct {
+		Outcome struct {
+			Selected struct {
+				ID string `json:"id"`
+			} `json:"selected"`
+		} `json:"outcome"`
+	}
+	require.NoError(t, json.Unmarshal(res.OK, &out))
+	assert.Equal(t, "allow_once", out.Outcome.Selected.ID)
+}
+
+func TestPermission_NoOptions_EmptyOutcome(t *testing.T) {
+	t.Parallel()
+	h := handlers.NewPermissionHandler()
+	params := mustJSON(t, map[string]any{"sessionId": "x"})
+	res := h.Handle(context.Background(), handlers.SessionContext{}, params)
+	require.Nil(t, res.Err)
+	assert.JSONEq(t, `{"outcome":{}}`, string(res.OK))
+}