antigravity: stop exposing harness state_dir in ax.yaml

cmd/ax/harness.go

@@ -160,13 +160,11 @@ func runAntigravityInteractionsHarness(ctx context.Context) error {
 	if agent == "" {
 		agent = antigravityinteractions.DefaultAgent
 	}
-	stateDir := hc.StateDir
-	if stateDir == "" {
-		var err error
-		stateDir, err = antigravityinteractions.DefaultStateDir()
-		if err != nil {
-			return err
-		}
+	// AX owns the resume-cursor path (a harness implementation detail), so it's
+	// derived internally rather than read from ax.yaml.
+	stateDir, err := antigravityinteractions.DefaultStateDir()
+	if err != nil {
+		return err
 	}
 
 	cfg := antigravityinteractions.AntigravityInteractionsConfig{

cmd/ax/internal/cliutil/cliutil.go

@@ -71,9 +71,14 @@ func NewControllerFromConfig(ctx context.Context, cfg *Config) (*controller.Cont
 		if address == "" {
 			address = "127.0.0.1:50053"
 		}
-		// Local mode: the harness owns the Python sidecar. Empty StateDir
-		// means the sidecar applies its own default
-		antigravityHarness, err = antigravity.New(ctx, address, cfg.Harnesses.Antigravity.StateDir, true)
+		// Local mode: the harness owns the Python sidecar. AX owns the
+		// trajectory storage path (a harness implementation detail), so it's
+		// derived internally rather than exposed in ax.yaml.
+		stateDir, sErr := antigravity.DefaultStateDir()
+		if sErr != nil {
+			return nil, fmt.Errorf("antigravity harness: %w", sErr)
+		}
+		antigravityHarness, err = antigravity.New(ctx, address, stateDir, true)
 		if err != nil {
 			return nil, fmt.Errorf("antigravity harness: %w", err)
 		}
@@ -97,12 +102,11 @@ func NewControllerFromConfig(ctx context.Context, cfg *Config) (*controller.Cont
 		if agent == "" {
 			agent = antigravityinteractions.DefaultAgent
 		}
-		stateDir := cfg.Harnesses.AntigravityInteractions.StateDir
-		if stateDir == "" {
-			stateDir, err = antigravityinteractions.DefaultStateDir()
-			if err != nil {
-				return nil, fmt.Errorf("antigravity-interactions harness: %w", err)
-			}
+		// AX owns the resume-cursor path (a harness implementation detail), so
+		// it's derived internally rather than exposed in ax.yaml.
+		stateDir, sErr := antigravityinteractions.DefaultStateDir()
+		if sErr != nil {
+			return nil, fmt.Errorf("antigravity-interactions harness: %w", sErr)
 		}
 		antigravityInteractionsHarness, err = antigravityinteractions.New(antigravityinteractions.AntigravityInteractionsConfig{
 			Agent:    agent,

internal/config/config.go

@@ -97,16 +97,14 @@ type HarnessesConfig struct {
 // AntigravityHarnessConfig registers the built-in Antigravity harness.
 type AntigravityHarnessConfig struct {
 	Default  bool   `yaml:"default,omitempty"`
-	Endpoint string `yaml:"endpoint,omitempty"`  // HarnessService address
-	StateDir string `yaml:"state_dir,omitempty"` // Trajectory storage dir (optional; sidecar defaults to ~/.ax/antigravity/conversations)
+	Endpoint string `yaml:"endpoint,omitempty"` // HarnessService address
 }
 
 // AntigravityInteractionsHarnessConfig registers the built-in Antigravity
 // Interactions harness (over the Vertex GenAI Interactions API).
 type AntigravityInteractionsHarnessConfig struct {
-	Default  bool   `yaml:"default,omitempty"`   // Default harness or not
-	Agent    string `yaml:"agent,omitempty"`     // Interactions API agent (default: antigravityinteractions.DefaultAgent)
-	StateDir string `yaml:"state_dir,omitempty"` // Resume-cursor directory (optional; defaults to ~/.ax/antigravityinteractions/cursors)
+	Default bool   `yaml:"default,omitempty"` // Default harness or not
+	Agent   string `yaml:"agent,omitempty"`   // Interactions API agent (default: antigravityinteractions.DefaultAgent)
 }
 
 // SubstrateHarnessConfig registers a custom harness deployed on substrate

internal/config/config_test.go

@@ -115,8 +115,7 @@ func TestValidate_InteractionsIDReserved(t *testing.T) {
 func TestValidate_InteractionsValid(t *testing.T) {
 	c := validConfig()
 	c.Harnesses.AntigravityInteractions = AntigravityInteractionsHarnessConfig{
-		Agent:    "projects/p/locations/global/agents/a",
-		StateDir: "interactions-state",
+		Agent: "projects/p/locations/global/agents/a",
 	}
 	if err := c.Validate(); err != nil {
 		t.Fatalf("Validate() = %v, want nil", err)
@@ -141,22 +140,6 @@ eventlog:
 	}
 }
 
-// TestLoadFromFile_AntigravityStateDir: yaml -> AntigravityHarnessConfig.StateDir.
-func TestLoadFromFile_AntigravityStateDir(t *testing.T) {
-	data := `
-harnesses:
-  antigravity:
-    state_dir: /custom/path
-`
-	var cfg Config
-	if err := yaml.Unmarshal([]byte(data), &cfg); err != nil {
-		t.Fatalf("Unmarshal failed: %v", err)
-	}
-	if got, want := cfg.Harnesses.Antigravity.StateDir, "/custom/path"; got != want {
-		t.Errorf("StateDir = %q, want %q", got, want)
-	}
-}
-
 func TestLoadFromBytes(t *testing.T) {
 	cfg, err := LoadFromBytes([]byte(`
 version: v1alpha

internal/harness/antigravity/antigravity.go

@@ -21,6 +21,7 @@ import (
 	"net"
 	"os"
 	"os/signal"
+	"path/filepath"
 	"sync"
 	"syscall"
 
@@ -29,6 +30,7 @@ import (
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/credentials/insecure"
 
+	"github.com/google/ax/internal/config"
 	"github.com/google/ax/internal/harness"
 	"github.com/google/ax/internal/pythonsidecar"
 	"github.com/google/ax/proto"
@@ -40,6 +42,20 @@ import (
 var _ harness.Harness = (*AntigravityHarness)(nil)
 var _ harness.Execution = (*antigravityExecution)(nil)
 
+// DefaultStateDir returns the default trajectory storage directory,
+// ~/.ax/antigravity/conversations. AX owns this path so it stays a harness
+// implementation detail rather than a user-facing ax.yaml knob. It lives
+// outside the agent's working directory on purpose: the working directory is
+// the agent's operating surface (it reads and edits files there), so AX's
+// internal state is kept separate to avoid the agent seeing or clobbering it.
+func DefaultStateDir() (string, error) {
+	axDir, err := config.AXAssetsDir()
+	if err != nil {
+		return "", err
+	}
+	return filepath.Join(axDir, "antigravity", "conversations"), nil
+}
+
 // AntigravityHarness implements the Harness interface by connecting to the
 // Antigravity Python agent server over gRPC.
 type AntigravityHarness struct {

internal/harness/antigravity/antigravity_test.go

@@ -17,6 +17,7 @@ package antigravity
 import (
 	"bytes"
 	"context"
+	"path/filepath"
 	"strings"
 	"testing"
 
@@ -106,3 +107,18 @@ func TestNew_AutoStartFalse_NilSidecar(t *testing.T) {
 		t.Errorf("expected sidecar to be nil, got %v", h.sidecar)
 	}
 }
+
+// TestDefaultStateDir returns ~/.ax/antigravity/conversations under the user's
+// home directory.
+func TestDefaultStateDir(t *testing.T) {
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+
+	got, err := DefaultStateDir()
+	if err != nil {
+		t.Fatalf("DefaultStateDir: %v", err)
+	}
+	if want := filepath.Join(home, ".ax", "antigravity", "conversations"); got != want {
+		t.Errorf("DefaultStateDir() = %q, want %q", got, want)
+	}
+}