diff --git a/cmd/gortex/daemon_mcp.go b/cmd/gortex/daemon_mcp.go
index cfaa12f8..78a43b97 100644
--- a/cmd/gortex/daemon_mcp.go
+++ b/cmd/gortex/daemon_mcp.go
@@ -156,6 +156,12 @@ func (d *mcpDispatcher) Dispatch(ctx context.Context, sess *daemon.Session, fram
 			// Record only permitted calls to deferred/learned tools so a rejected
 			// hidden call cannot refresh learned-surface state.
 			d.srv.NoteToolUse(name, sess.CWD, newly)
+			// Promotion alone is not enough: mcp-go re-applies the tools/list
+			// filter to the requested tool at call time and reports a filtered
+			// tool as "not found". Mark the call as authorized so the surface
+			// filter recognises that probe (see WithAuthorizedToolCall); the
+			// per-call gate inside the handler still decides the outcome.
+			ctx = gortexmcp.WithAuthorizedToolCall(ctx, name)
 		}
 	}
 
diff --git a/internal/mcp/promote_call_gate_test.go b/internal/mcp/promote_call_gate_test.go
new file mode 100644
index 00000000..212c8337
--- /dev/null
+++ b/internal/mcp/promote_call_gate_test.go
@@ -0,0 +1,123 @@
+package mcp
+
+import (
+	"context"
+	"encoding/json"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+// callToolFrame dispatches one tools/call frame through the real MCP server
+// entry point the daemon dispatcher uses and returns the marshalled reply.
+func callToolFrame(t *testing.T, srv *Server, ctx context.Context, tool string, args map[string]any) string {
+	t.Helper()
+	if args == nil {
+		args = map[string]any{}
+	}
+	frame, err := json.Marshal(map[string]any{
+		"jsonrpc": "2.0", "id": 1, "method": "tools/call",
+		"params": map[string]any{"name": tool, "arguments": args},
+	})
+	require.NoError(t, err)
+	reply := srv.MCPServer().HandleMessage(ctx, json.RawMessage(frame))
+	require.NotNil(t, reply)
+	out, err := json.Marshal(reply)
+	require.NoError(t, err)
+	return string(out)
+}
+
+// TestPromotedToolCallableUnderCorePreset covers the by-name reachability
+// contract: a tool held out of a session's tools/list (the `core` defer preset)
+// stays callable by name after the dispatcher promotes it.
+//
+// Regression: mcp-go v0.55.1 started re-running registered tool filters at call
+// time (server.passesToolFilters). toolSurfaceFilter shapes tools/list
+// visibility, so every non-preset tool — 141 of 178 under `core` — began
+// answering "tool '<name>' not found: tool not found" for CLI (`gortex call`)
+// and for any agent session that forwarded a preset, including calls to tools
+// tools_search had just promoted.
+func TestPromotedToolCallableUnderCorePreset(t *testing.T) {
+	srv, _ := setupTestServer(t)
+
+	const sessionID = "cli_core_defer"
+	const toolName = "export_context"
+	srv.NoteSessionToolPolicy(sessionID, "core", "defer")
+	ctx := WithSessionID(context.Background(), sessionID)
+
+	require.Equal(t, "deferred", srv.sessionToolStatus(ctx, toolName),
+		"precondition: export_context is deferred under core/defer")
+	require.True(t, srv.IsToolEnabledForSession(ctx, toolName),
+		"precondition: the dispatcher's promote gate permits this call")
+
+	// What the daemon dispatcher does before HandleMessage.
+	srv.EnsureToolPromotedForSession(ctx, toolName)
+	ctx = WithAuthorizedToolCall(ctx, toolName)
+
+	out := callToolFrame(t, srv, ctx, toolName, map[string]any{"task": "cli flags"})
+	require.NotContains(t, out, "tool not found",
+		"a promoted tool must be callable by name under core/defer:\n%s", clip(out))
+}
+
+// TestAuthorizedCallMarkerKeepsHideModeEnforced proves the carve-out cannot be
+// used to widen a session's surface: a hide-mode preset still refuses a tool
+// outside its allow-set even when the marker is present, and the refusal is the
+// structured blocked-by-mode error rather than a misleading "not found".
+func TestAuthorizedCallMarkerKeepsHideModeEnforced(t *testing.T) {
+	srv, _ := setupTestServer(t)
+
+	const sessionID = "hide_mode_client"
+	const toolName = "export_context"
+	srv.NoteSessionToolPolicy(sessionID, "nav", "hide")
+	ctx := WithSessionID(context.Background(), sessionID)
+
+	require.False(t, srv.IsToolEnabledForSession(ctx, toolName),
+		"precondition: a hide-mode session must not be allowed to call a non-preset tool")
+
+	// The dispatcher would never mark this call; set it anyway so the test
+	// covers the gate rather than the dispatcher's restraint.
+	out := callToolFrame(t, srv, WithAuthorizedToolCall(ctx, toolName), toolName, nil)
+	require.Contains(t, out, string(ErrCodeToolBlockedByMode),
+		"hide mode must still refuse the call:\n%s", clip(out))
+}
+
+// TestAuthorizedCallMarkerDoesNotWidenToolsList pins the marker to the
+// call-time single-tool probe: a tools/list rendered on the same context still
+// shows only the session's preset surface.
+func TestAuthorizedCallMarkerDoesNotWidenToolsList(t *testing.T) {
+	srv, _ := setupTestServer(t)
+
+	const sessionID = "list_under_marker"
+	const toolName = "export_context"
+	srv.NoteSessionToolPolicy(sessionID, "core", "defer")
+	ctx := WithSessionID(context.Background(), sessionID)
+	srv.EnsureToolPromotedForSession(ctx, toolName)
+	ctx = WithAuthorizedToolCall(ctx, toolName)
+
+	reply := srv.MCPServer().HandleMessage(ctx,
+		json.RawMessage(`{"jsonrpc":"2.0","id":1,"method":"tools/list","params":{}}`))
+	out, err := json.Marshal(reply)
+	require.NoError(t, err)
+
+	var parsed struct {
+		Result struct {
+			Tools []struct {
+				Name string `json:"name"`
+			} `json:"tools"`
+		} `json:"result"`
+	}
+	require.NoError(t, json.Unmarshal(out, &parsed))
+	for _, tool := range parsed.Result.Tools {
+		require.NotEqual(t, toolName, tool.Name,
+			"the authorized-call marker must not leak a non-preset tool into tools/list")
+	}
+	require.NotEmpty(t, parsed.Result.Tools, "the preset surface should still render")
+}
+
+func clip(s string) string {
+	if len(s) <= 400 {
+		return s
+	}
+	return strings.TrimSpace(s[:400]) + "…"
+}
diff --git a/internal/mcp/session_ctx.go b/internal/mcp/session_ctx.go
index 5e088fda..dc71dd22 100644
--- a/internal/mcp/session_ctx.go
+++ b/internal/mcp/session_ctx.go
@@ -78,6 +78,44 @@ func SessionCWDFromContext(ctx context.Context) string {
 	return ""
 }
 
+// authorizedCallCtxKey carries the tool name of an inbound tools/call that
+// the session's own authorization already permitted (see
+// Server.IsToolEnabledForSession). It exists because mcp-go re-runs every
+// registered tool filter at CALL time (server.passesToolFilters, added in
+// mcp-go v0.55.1) with the single requested tool: a filter that only shapes
+// tools/list VISIBILITY would otherwise turn a legitimate by-name call into
+// "tool '<name>' not found". Unexported key: set it via
+// WithAuthorizedToolCall.
+type authorizedCallCtxKey struct{}
+
+// WithAuthorizedToolCall returns a context marking name as an authorized
+// by-name tools/call for this session. The daemon's MCP dispatcher sets it
+// after IsToolEnabledForSession accepts the call and before HandleMessage, so
+// toolSurfaceFilter knows the follow-up single-tool filter invocation is
+// mcp-go's call-time access check and not a tools/list render.
+//
+// This never widens what a session may call: the marker is only set for names
+// the session's effective surface already permits, and checkToolGate still
+// runs the authoritative per-call gate inside the handler wrapper.
+func WithAuthorizedToolCall(ctx context.Context, name string) context.Context {
+	if name == "" {
+		return ctx
+	}
+	return context.WithValue(ctx, authorizedCallCtxKey{}, name)
+}
+
+// authorizedToolCallFromContext returns the tool name attached via
+// WithAuthorizedToolCall, or "" when none is present.
+func authorizedToolCallFromContext(ctx context.Context) string {
+	if ctx == nil {
+		return ""
+	}
+	if name, ok := ctx.Value(authorizedCallCtxKey{}).(string); ok {
+		return name
+	}
+	return ""
+}
+
 // repoAllowCtxKey carries the per-request repo allow-set resolved by
 // handleAnalyze (resolveScope → ResolvedScope.RepoAllow). The scoped-
 // node accessors (scopedNodes / scopedNodesByKinds / scopedNodeSlice)
diff --git a/internal/mcp/tools_mode.go b/internal/mcp/tools_mode.go
index 5cabe7f2..a3177b87 100644
--- a/internal/mcp/tools_mode.go
+++ b/internal/mcp/tools_mode.go
@@ -39,6 +39,18 @@ func (s *Server) editingToolsHidden(ctx context.Context) bool {
 }
 
 func (s *Server) toolSurfaceFilter(ctx context.Context, tools []mcp.Tool) []mcp.Tool {
+	// mcp-go v0.55.1+ re-runs every registered tool filter at CALL time
+	// (server.passesToolFilters) with just the requested tool, and answers
+	// "tool '<name>' not found" when the filter drops it. This filter shapes
+	// tools/list VISIBILITY — a deferred tool promoted on demand, or any tool
+	// outside a narrow preset, is still callable by name (checkToolGate is the
+	// authoritative call gate). Let that single-tool probe through when the
+	// dispatcher already authorized this exact call, or the visibility rule
+	// silently becomes a call gate that reports the tool as missing.
+	if name := authorizedToolCallFromContext(ctx); name != "" &&
+		len(tools) == 1 && tools[0].Name == name {
+		return tools
+	}
 	if s.editingToolsHidden(ctx) {
 		tools = withoutMutatingTools(tools)
 	}