diff --git a/docs/agents.md b/docs/agents.md
index 60d5f16aa..d2633b8a1 100644
--- a/docs/agents.md
+++ b/docs/agents.md
@@ -160,11 +160,12 @@ Kiro uses native custom agents in `~/.kiro/agents/`. `gentle-ai` writes phase ag
 
 ### Antigravity
 
-- Skills at `~/.gemini/antigravity/skills/` (native Antigravity feature)
-- MCP config at `~/.gemini/antigravity/mcp_config.json`
+- Skills at `<variantDir>/skills/` where `<variantDir>` is the resolved Antigravity variant (IDE → Desktop → `~/.gemini/antigravity-cli/` fallback)
+- Engram plugin at `<variantDir>/plugins/gentle-ai-engram/`
+- MCP config at `~/.gemini/config/mcp_config.json` (shared global location)
 - System prompt appended to `~/.gemini/GEMINI.md` (shared with Gemini CLI — collision check warns if both are installed)
 - Mission Control handles built-in sub-agent delegation (Browser, Terminal) automatically
-- Settings managed via the IDE's Agent settings UI, not via `settings.json`
+- Settings initialized via `<variantDir>/settings.json` but primarily managed via the IDE's Agent settings UI
 
 ### Kimi Code
 
diff --git a/internal/agents/antigravity/adapter.go b/internal/agents/antigravity/adapter.go
index bad5a8298..1a44d1b1f 100644
--- a/internal/agents/antigravity/adapter.go
+++ b/internal/agents/antigravity/adapter.go
@@ -9,6 +9,13 @@ import (
 	"github.com/gentleman-programming/gentle-ai/internal/system"
 )
 
+// GlobalMCPConfigPath returns the absolute path to the shared global MCP
+// configuration file under homeDir. Antigravity uses this single location
+// across CLI, Desktop, and IDE variants.
+func GlobalMCPConfigPath(homeDir string) string {
+	return filepath.Join(homeDir, ".gemini", "config", "mcp_config.json")
+}
+
 type statResult struct {
 	isDir bool
 	err   error
@@ -24,13 +31,19 @@ func NewAdapter() *Adapter {
 	}
 }
 
-// antigravityVariantDir returns the resolved variant directory under ~/.gemini.
-// Prefers "antigravity-desktop" when it exists, falls back to "antigravity-cli".
+// antigravityVariantDir returns the resolved variant directory.
+// Checks OS-specific IDE paths, then legacy desktop, falls back to CLI.
 func (a *Adapter) antigravityVariantDir(homeDir string) string {
-	desktop := filepath.Join(homeDir, ".gemini", "antigravity-desktop")
-	if stat := a.statPath(desktop); stat.err == nil {
+	ideDir := filepath.Join(homeDir, ".gemini", "antigravity-ide")
+	if stat := a.statPath(ideDir); stat.err == nil && stat.isDir {
+		return ideDir
+	}
+
+	desktop := filepath.Join(homeDir, ".gemini", "antigravity")
+	if stat := a.statPath(desktop); stat.err == nil && stat.isDir {
 		return desktop
 	}
+
 	return filepath.Join(homeDir, ".gemini", "antigravity-cli")
 }
 
@@ -105,7 +118,7 @@ func (a *Adapter) MCPStrategy() model.MCPStrategy {
 // --- MCP ---
 
 func (a *Adapter) MCPConfigPath(homeDir string, _ string) string {
-	return filepath.Join(a.antigravityVariantDir(homeDir), "mcp_config.json")
+	return GlobalMCPConfigPath(homeDir)
 }
 
 // --- Optional capabilities ---
diff --git a/internal/agents/antigravity/adapter_test.go b/internal/agents/antigravity/adapter_test.go
index 3813b704d..e35fa7a77 100644
--- a/internal/agents/antigravity/adapter_test.go
+++ b/internal/agents/antigravity/adapter_test.go
@@ -31,32 +31,38 @@ func makeStatFn(existingDirs ...string) func(string) statResult {
 func TestAntigravityVariantDir(t *testing.T) {
 	home := t.TempDir()
 	cliDir := filepath.Join(home, ".gemini", "antigravity-cli")
-	desktopDir := filepath.Join(home, ".gemini", "antigravity-desktop")
+	desktopDir := filepath.Join(home, ".gemini", "antigravity")
+	ideDir := filepath.Join(home, ".gemini", "antigravity-ide")
 
 	tests := []struct {
 		name         string
 		existingDirs []string
-		wantSuffix   string // last two path segments expected
+		wantDir      string
 	}{
 		{
 			name:         "only CLI dir exists resolves to CLI",
 			existingDirs: []string{cliDir},
-			wantSuffix:   filepath.Join(".gemini", "antigravity-cli"),
+			wantDir:      cliDir,
 		},
 		{
 			name:         "only Desktop dir exists resolves to Desktop",
 			existingDirs: []string{desktopDir},
-			wantSuffix:   filepath.Join(".gemini", "antigravity-desktop"),
+			wantDir:      desktopDir,
 		},
 		{
-			name:         "both exist prefers Desktop",
-			existingDirs: []string{cliDir, desktopDir},
-			wantSuffix:   filepath.Join(".gemini", "antigravity-desktop"),
+			name:         "only IDE dir exists resolves to IDE",
+			existingDirs: []string{ideDir},
+			wantDir:      ideDir,
+		},
+		{
+			name:         "all exist prefers IDE over Desktop over CLI",
+			existingDirs: []string{cliDir, desktopDir, ideDir},
+			wantDir:      ideDir,
 		},
 		{
 			name:         "neither exists falls back to CLI",
 			existingDirs: []string{},
-			wantSuffix:   filepath.Join(".gemini", "antigravity-cli"),
+			wantDir:      cliDir,
 		},
 	}
 
@@ -64,9 +70,8 @@ func TestAntigravityVariantDir(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			a := &Adapter{statPath: makeStatFn(tt.existingDirs...)}
 			got := a.antigravityVariantDir(home)
-			want := filepath.Join(home, tt.wantSuffix)
-			if got != want {
-				t.Fatalf("antigravityVariantDir() = %q, want %q", got, want)
+			if got != tt.wantDir {
+				t.Fatalf("antigravityVariantDir() = %q, want %q", got, tt.wantDir)
 			}
 		})
 	}
@@ -77,7 +82,7 @@ func TestAntigravityVariantDir(t *testing.T) {
 func TestDetect(t *testing.T) {
 	home := t.TempDir()
 	cliDir := filepath.Join(home, ".gemini", "antigravity-cli")
-	desktopDir := filepath.Join(home, ".gemini", "antigravity-desktop")
+	desktopDir := filepath.Join(home, ".gemini", "antigravity")
 
 	tests := []struct {
 		name            string
@@ -174,14 +179,15 @@ func TestConfigPathsCLIOnly(t *testing.T) {
 	if got := a.SettingsPath(home); got != filepath.Join(cliDir, "settings.json") {
 		t.Fatalf("SettingsPath() = %q, want %q", got, filepath.Join(cliDir, "settings.json"))
 	}
-	if got := a.MCPConfigPath(home, "ctx7"); got != filepath.Join(cliDir, "mcp_config.json") {
-		t.Fatalf("MCPConfigPath() = %q, want %q", got, filepath.Join(cliDir, "mcp_config.json"))
+	wantMCP := GlobalMCPConfigPath(home)
+	if got := a.MCPConfigPath(home, "ctx7"); got != wantMCP {
+		t.Fatalf("MCPConfigPath() = %q, want %q", got, wantMCP)
 	}
 }
 
 func TestConfigPathsDesktopOnly(t *testing.T) {
 	home := t.TempDir()
-	desktopDir := filepath.Join(home, ".gemini", "antigravity-desktop")
+	desktopDir := filepath.Join(home, ".gemini", "antigravity")
 	a := &Adapter{statPath: makeStatFn(desktopDir)}
 
 	if got := a.GlobalConfigDir(home); got != desktopDir {
@@ -193,15 +199,16 @@ func TestConfigPathsDesktopOnly(t *testing.T) {
 	if got := a.SettingsPath(home); got != filepath.Join(desktopDir, "settings.json") {
 		t.Fatalf("SettingsPath() = %q, want %q", got, filepath.Join(desktopDir, "settings.json"))
 	}
-	if got := a.MCPConfigPath(home, "ctx7"); got != filepath.Join(desktopDir, "mcp_config.json") {
-		t.Fatalf("MCPConfigPath() = %q, want %q", got, filepath.Join(desktopDir, "mcp_config.json"))
+	wantMCP := GlobalMCPConfigPath(home)
+	if got := a.MCPConfigPath(home, "ctx7"); got != wantMCP {
+		t.Fatalf("MCPConfigPath() = %q, want %q", got, wantMCP)
 	}
 }
 
 func TestConfigPathsBothExistPrefersDesktop(t *testing.T) {
 	home := t.TempDir()
 	cliDir := filepath.Join(home, ".gemini", "antigravity-cli")
-	desktopDir := filepath.Join(home, ".gemini", "antigravity-desktop")
+	desktopDir := filepath.Join(home, ".gemini", "antigravity")
 	a := &Adapter{statPath: makeStatFn(cliDir, desktopDir)}
 
 	if got := a.GlobalConfigDir(home); got != desktopDir {
diff --git a/internal/cli/run_engram_download_test.go b/internal/cli/run_engram_download_test.go
index a38603586..04b773ee0 100644
--- a/internal/cli/run_engram_download_test.go
+++ b/internal/cli/run_engram_download_test.go
@@ -3,6 +3,7 @@ package cli
 import (
 	"os"
 	"path/filepath"
+	"runtime"
 	"strings"
 	"testing"
 
@@ -214,6 +215,9 @@ func TestRunInstallBetaEngramUsesMainGoInstallAndInstalledBinary(t *testing.T) {
 	home := t.TempDir()
 	gobin := filepath.Join(home, "go-bin")
 	betaEngram := filepath.Join(gobin, "engram")
+	if runtime.GOOS == "windows" {
+		betaEngram += ".exe"
+	}
 
 	restoreCommand := runCommand
 	restoreLookPath := cmdLookPath
diff --git a/internal/cli/sync.go b/internal/cli/sync.go
index dc213799e..6f4ed582f 100644
--- a/internal/cli/sync.go
+++ b/internal/cli/sync.go
@@ -1060,7 +1060,11 @@ func RenderSyncReport(result SyncResult) string {
 
 	if len(result.ChangedFiles) > 0 {
 		for _, path := range result.ChangedFiles {
-			fmt.Fprintf(&b, "  - %s\n", path)
+			suffix := ""
+			if strings.HasSuffix(path, filepath.Join(".gemini", "config", "mcp_config.json")) {
+				suffix = " (shared global configuration)"
+			}
+			fmt.Fprintf(&b, "  - %s%s\n", path, suffix)
 		}
 	}
 
diff --git a/internal/components/engram/inject.go b/internal/components/engram/inject.go
index 46b11e82f..1056462cd 100644
--- a/internal/components/engram/inject.go
+++ b/internal/components/engram/inject.go
@@ -131,11 +131,6 @@ func engramOverlayJSON(agentID model.AgentID, cmd string) []byte {
 		}
 	} else {
 		args := []string{"mcp", "--tools=agent"}
-		if agentID == model.AgentAntigravity {
-			// Antigravity should launch the default Engram MCP server without
-			// narrowing the exposed tool set.
-			args = []string{"mcp"}
-		}
 		cfg = map[string]any{
 			"mcpServers": map[string]any{
 				"engram": map[string]any{
@@ -250,8 +245,8 @@ func ensureJSONFileIfMissing(path string) (filemerge.WriteResult, error) {
 	return filemerge.WriteFileAtomic(path, []byte("{}\n"), 0o644)
 }
 
-func installAntigravityEngramPlugin(homeDir, engramCommand string) (bool, []string, error) {
-	pluginDir := filepath.Join(homeDir, ".gemini", "antigravity-cli", "plugins", "gentle-ai-engram")
+func installAntigravityEngramPlugin(variantDir, engramCommand string) (bool, []string, error) {
+	pluginDir := filepath.Join(variantDir, "plugins", "gentle-ai-engram")
 	files := make([]string, 0, 3)
 	changed := false
 
@@ -360,7 +355,7 @@ func injectWithOptions(configHomeDir, promptDir string, adapter agents.Adapter,
 			changed = changed || settingsWrite.Changed
 			files = append(files, adapter.SettingsPath(configHomeDir))
 
-			pluginChanged, pluginFiles, pluginErr := installAntigravityEngramPlugin(configHomeDir, engramCommand)
+			pluginChanged, pluginFiles, pluginErr := installAntigravityEngramPlugin(adapter.GlobalConfigDir(configHomeDir), engramCommand)
 			if pluginErr != nil {
 				return InjectionResult{}, pluginErr
 			}
diff --git a/internal/components/engram/inject_test.go b/internal/components/engram/inject_test.go
index 488064f5e..1d2e75c43 100644
--- a/internal/components/engram/inject_test.go
+++ b/internal/components/engram/inject_test.go
@@ -557,9 +557,10 @@ func TestInjectGeminiToolsFlagPresent(t *testing.T) {
 	}
 }
 
-func TestInjectAntigravityWritesMCPToCLIConfig(t *testing.T) {
+func TestInjectAntigravityWritesMCPToGlobalConfig(t *testing.T) {
 	home := t.TempDir()
 
+
 	result, err := Inject(home, antigravityAdapter())
 	if err != nil {
 		t.Fatalf("Inject(antigravity) error = %v", err)
@@ -568,17 +569,22 @@ func TestInjectAntigravityWritesMCPToCLIConfig(t *testing.T) {
 		t.Fatalf("Inject(antigravity) changed = false")
 	}
 
-	cliMCPPath := filepath.Join(home, ".gemini", "antigravity-cli", "mcp_config.json")
-	content, err := os.ReadFile(cliMCPPath)
+	globalMCPPath := antigravity.GlobalMCPConfigPath(home)
+	content, err := os.ReadFile(globalMCPPath)
 	if err != nil {
-		t.Fatalf("ReadFile(%q) error = %v", cliMCPPath, err)
+		t.Fatalf("ReadFile(%q) error = %v", globalMCPPath, err)
+	}
+
+	oldCLIPath := filepath.Join(home, ".gemini", "antigravity-cli", "mcp_config.json")
+	if _, err := os.Stat(oldCLIPath); !os.IsNotExist(err) {
+		t.Fatalf("legacy CLI MCP path %q should not be written for antigravity; stat err = %v", oldCLIPath, err)
 	}
 	text := string(content)
 	if !strings.Contains(text, `"args": [`) || !strings.Contains(text, `"mcp"`) {
 		t.Fatalf("Antigravity MCP config must launch Engram MCP; got:\n%s", text)
 	}
-	if strings.Contains(text, `--tools=`) {
-		t.Fatalf("Antigravity should use Engram's default MCP invocation without tool-profile flags; got:\n%s", text)
+	if !strings.Contains(text, `"--tools=agent"`) {
+		t.Fatalf("Antigravity should use Engram's MCP invocation with --tools=agent; got:\n%s", text)
 	}
 
 	pluginPath := filepath.Join(home, ".gemini", "antigravity-cli", "plugins", "gentle-ai-engram", "plugin.json")
@@ -592,8 +598,8 @@ func TestInjectAntigravityWritesMCPToCLIConfig(t *testing.T) {
 		t.Fatalf("ReadFile(%q) error = %v", pluginMCPPath, err)
 	}
 	pluginMCPText := string(pluginMCPContent)
-	if !strings.Contains(pluginMCPText, `"mcp"`) || strings.Contains(pluginMCPText, `--tools=`) {
-		t.Fatalf("Antigravity Engram plugin MCP config should expose default Engram MCP tools; got:\n%s", pluginMCPText)
+	if !strings.Contains(pluginMCPText, `"mcp"`) || !strings.Contains(pluginMCPText, `"--tools=agent"`) {
+		t.Fatalf("Antigravity Engram plugin MCP config should expose Engram MCP tools via --tools=agent; got:\n%s", pluginMCPText)
 	}
 
 	hooksPath := filepath.Join(home, ".gemini", "antigravity-cli", "plugins", "gentle-ai-engram", "hooks.json")
@@ -626,9 +632,46 @@ func TestInjectAntigravityWritesMCPToCLIConfig(t *testing.T) {
 	}
 }
 
+func TestInjectAntigravityIDEVariantReceivesPlugin(t *testing.T) {
+	home := t.TempDir()
+
+	// Create the IDE path on disk so the adapter's real os.Stat resolves to the IDE variant.
+	ideDir := filepath.Join(home, ".gemini", "antigravity-ide")
+	if err := os.MkdirAll(ideDir, 0o755); err != nil {
+		t.Fatalf("MkdirAll(%q) error = %v", ideDir, err)
+	}
+
+	result, err := Inject(home, antigravity.NewAdapter())
+	if err != nil {
+		t.Fatalf("Inject(antigravity-IDE) error = %v", err)
+	}
+	if !result.Changed {
+		t.Fatalf("Inject(antigravity-IDE) changed = false")
+	}
+
+	// Plugin files must land inside the IDE variant directory.
+	for _, rel := range []string{
+		filepath.Join("plugins", "gentle-ai-engram", "plugin.json"),
+		filepath.Join("plugins", "gentle-ai-engram", "mcp_config.json"),
+		filepath.Join("plugins", "gentle-ai-engram", "hooks.json"),
+	} {
+		p := filepath.Join(ideDir, rel)
+		if _, err := os.Stat(p); err != nil {
+			t.Fatalf("expected plugin file at IDE variant path %q; stat error = %v", p, err)
+		}
+	}
+
+	// Legacy CLI directory must NOT be created.
+	legacyCLI := filepath.Join(home, ".gemini", "antigravity-cli")
+	if _, err := os.Stat(legacyCLI); !os.IsNotExist(err) {
+		t.Fatalf("legacy CLI directory %q should not exist when IDE variant is active; stat err = %v", legacyCLI, err)
+	}
+}
+
 func TestInjectAntigravityInitializesEmptySettingsWhenGeminiMissing(t *testing.T) {
 	home := t.TempDir()
 
+
 	first, err := Inject(home, antigravityAdapter())
 	if err != nil {
 		t.Fatalf("Inject(antigravity) first error = %v", err)
diff --git a/internal/components/golden_test.go b/internal/components/golden_test.go
index 2589cd7da..edca74d2d 100644
--- a/internal/components/golden_test.go
+++ b/internal/components/golden_test.go
@@ -886,6 +886,8 @@ func TestGoldenPersona_Antigravity_Gentleman(t *testing.T) {
 func TestGoldenEngram_Antigravity(t *testing.T) {
 	home := t.TempDir()
 
+
+
 	engram.SetLookPathForTest(t, "/opt/homebrew/bin/engram", "")
 
 	result, err := engram.Inject(home, antigravityAdapter())
@@ -896,8 +898,8 @@ func TestGoldenEngram_Antigravity(t *testing.T) {
 		t.Fatalf("engram.Inject(antigravity) changed = false")
 	}
 
-	// MCP config written to ~/.gemini/antigravity-cli/mcp_config.json.
-	mcpJSON := readTestFile(t, filepath.Join(home, ".gemini", "antigravity-cli", "mcp_config.json"))
+	// MCP config written to ~/.gemini/config/mcp_config.json.
+	mcpJSON := readTestFile(t, antigravity.GlobalMCPConfigPath(home))
 	assertGolden(t, "engram-antigravity-mcp.golden", mcpJSON)
 
 	// GEMINI.md must contain the engram-protocol section.
diff --git a/internal/system/config_scan.go b/internal/system/config_scan.go
index 11b5627bf..c62e07c8c 100644
--- a/internal/system/config_scan.go
+++ b/internal/system/config_scan.go
@@ -36,7 +36,7 @@ func knownAgentConfigDirs(homeDir string) []ConfigState {
 		{Agent: "cursor", Path: filepath.Join(homeDir, ".cursor")},
 		{Agent: "vscode-copilot", Path: vscodeCopilotGlobalConfigDir(homeDir)},
 		{Agent: "codex", Path: filepath.Join(homeDir, ".codex")},
-		{Agent: "antigravity", Path: filepath.Join(homeDir, ".gemini", "antigravity-cli")},
+		{Agent: "antigravity", Path: antigravityConfigDir(homeDir)},
 		{Agent: "windsurf", Path: filepath.Join(homeDir, ".codeium", "windsurf")},
 		{Agent: "kimi", Path: filepath.Join(homeDir, ".kimi")},
 		{Agent: "qwen-code", Path: filepath.Join(homeDir, ".qwen")},
@@ -48,6 +48,26 @@ func knownAgentConfigDirs(homeDir string) []ConfigState {
 	}
 }
 
+// antigravityConfigDir mirrors antigravity.Adapter.antigravityVariantDir
+// without importing the agents package (import cycle). Returns the first
+// existing variant directory: IDE → Desktop → CLI fallback.
+//
+// TODO(follow-up): remove this shim once the system ← agents import cycle is
+// resolved and ScanConfigs delegates directly to agents.DiscoverInstalled.
+func antigravityConfigDir(homeDir string) string {
+	ideDir := filepath.Join(homeDir, ".gemini", "antigravity-ide")
+	if info, err := os.Stat(ideDir); err == nil && info.IsDir() {
+		return ideDir
+	}
+
+	desktop := filepath.Join(homeDir, ".gemini", "antigravity")
+	if info, err := os.Stat(desktop); err == nil && info.IsDir() {
+		return desktop
+	}
+
+	return filepath.Join(homeDir, ".gemini", "antigravity-cli")
+}
+
 // vscodeCopilotGlobalConfigDir returns ~/.copilot, the GlobalConfigDir used by
 // the vscode-copilot adapter across all platforms. The vscode adapter's
 // SystemPromptDir and SettingsPath are OS-dependent, but GlobalConfigDir is not.
diff --git a/openspec/changes/antigravity-2.0-compatibility/design.md b/openspec/changes/antigravity-2.0-compatibility/design.md
index e7266a69f..d21863bf8 100644
--- a/openspec/changes/antigravity-2.0-compatibility/design.md
+++ b/openspec/changes/antigravity-2.0-compatibility/design.md
@@ -9,12 +9,12 @@ Use the existing public `antigravity` agent ID for the new Antigravity implement
 | Purpose | Path |
 |---------|------|
 | Agent ID | `antigravity` |
-| Config root | `~/.gemini/antigravity-cli/` |
-| Settings | `~/.gemini/antigravity-cli/settings.json` |
-| MCP config | `~/.gemini/antigravity-cli/mcp_config.json` |
-| Skills | `~/.gemini/antigravity-cli/skills/` |
+| Config root | `<variantDir>` (IDE → Desktop → CLI fallback) |
+| Settings | `<variantDir>/settings.json` |
+| MCP config | `~/.gemini/config/mcp_config.json` |
+| Skills | `<variantDir>/skills/` |
 | Shared prompt/persona | `~/.gemini/GEMINI.md` |
-| Engram plugin | `~/.gemini/antigravity-cli/plugins/gentle-ai-engram/` |
+| Engram plugin | `<variantDir>/plugins/gentle-ai-engram/` |
 
 ## Runtime model
 
@@ -26,7 +26,7 @@ The Go adapter does not install static subagent files. Instead, the SDD orchestr
 - `internal/assets/antigravity/sdd-orchestrator.md` owns the dynamic subagent prompt.
 - `internal/model/types.go` keeps only `AgentAntigravity` for this surface.
 - CLI and TUI validation accept `antigravity`; they do not expose `antigravity-cli`.
-- Engram MCP uses the default `engram mcp` invocation and adds an Antigravity plugin hook for tool-hint injection.
+- Engram MCP uses `engram mcp --tools=agent` (standard across all agents) and adds an Antigravity plugin hook for tool-hint injection.
 
 ## Compatibility
 
diff --git a/openspec/changes/antigravity-2.0-compatibility/exploration.md b/openspec/changes/antigravity-2.0-compatibility/exploration.md
index 073335519..6bd8d78e8 100644
--- a/openspec/changes/antigravity-2.0-compatibility/exploration.md
+++ b/openspec/changes/antigravity-2.0-compatibility/exploration.md
@@ -6,10 +6,10 @@ The new Antigravity implementation is compatible with the desktop product, not o
 
 ## Relevant surfaces
 
-- CLI/Desktop config root: `~/.gemini/antigravity-cli/`
+- Resolved config root: `<variantDir>` (IDE → Desktop → CLI fallback)
 - Shared prompt file: `~/.gemini/GEMINI.md`
-- Skills root: `~/.gemini/antigravity-cli/skills/`
-- MCP config: `~/.gemini/antigravity-cli/mcp_config.json`
+- Skills root: `<variantDir>/skills/`
+- MCP config: `~/.gemini/config/mcp_config.json`
 - Dynamic subagent tools: `define_subagent`, `invoke_subagent`
 
 ## Recommendation
diff --git a/openspec/changes/antigravity-2.0-compatibility/tasks.md b/openspec/changes/antigravity-2.0-compatibility/tasks.md
index 2b24a30b9..785303261 100644
--- a/openspec/changes/antigravity-2.0-compatibility/tasks.md
+++ b/openspec/changes/antigravity-2.0-compatibility/tasks.md
@@ -15,9 +15,9 @@
 
 ## 3. Engram and SDD behavior
 
-- [x] Write Antigravity MCP config to `~/.gemini/antigravity-cli/mcp_config.json`.
-- [x] Install Antigravity Engram plugin hooks under `~/.gemini/antigravity-cli/plugins/gentle-ai-engram/`.
-- [x] Use default `engram mcp` invocation without Antigravity-specific Pi assumptions.
+- [x] Write Antigravity MCP config to `~/.gemini/config/mcp_config.json`.
+- [x] Install Antigravity Engram plugin hooks under `<variantDir>/plugins/gentle-ai-engram/` (IDE → Desktop → CLI fallback).
+- [x] Use `engram mcp --tools=agent` invocation (standard across all agents).
 - [x] Ensure Antigravity SDD instructions use dynamic subagents.
 
 ## 4. Verification
diff --git a/openspec/specs/antigravity-support/spec.md b/openspec/specs/antigravity-support/spec.md
index 6e992becc..269d69ee1 100644
--- a/openspec/specs/antigravity-support/spec.md
+++ b/openspec/specs/antigravity-support/spec.md
@@ -17,15 +17,17 @@ The system MUST expose Antigravity as `antigravity` and MUST NOT expose a separa
 
 ### Requirement: Antigravity writes to the supported config surface
 
-The system MUST write Antigravity settings, MCP config, plugins, and skills under `~/.gemini/antigravity-cli/`.
+The system MUST write Antigravity settings, plugins, and skills under the resolved variant directory (IDE → Desktop → CLI fallback) and MCP config to the shared global location.
 
 #### Scenario: Antigravity files are installed
 
 - GIVEN the installer runs for `antigravity`
 - WHEN SDD, Engram, or permission components are applied
-- THEN settings are initialized at `~/.gemini/antigravity-cli/settings.json`
-- AND MCP config is merged at `~/.gemini/antigravity-cli/mcp_config.json`
-- AND skills are installed under `~/.gemini/antigravity-cli/skills/`.
+- THEN settings are initialized at `<variantDir>/settings.json`
+- AND MCP config is merged at `~/.gemini/config/mcp_config.json`
+- AND skills are installed under `<variantDir>/skills/`
+- AND Engram plugin is installed under `<variantDir>/plugins/gentle-ai-engram/`
+- WHERE `<variantDir>` is the first existing directory among the OS-specific IDE path, `~/.gemini/antigravity-desktop/`, or `~/.gemini/antigravity-cli/` (fallback).
 
 ### Requirement: Antigravity uses dynamic subagents
 
diff --git a/testdata/golden/engram-antigravity-mcp.golden b/testdata/golden/engram-antigravity-mcp.golden
index 306b24ca2..4f1c5bdc2 100644
--- a/testdata/golden/engram-antigravity-mcp.golden
+++ b/testdata/golden/engram-antigravity-mcp.golden
@@ -2,7 +2,8 @@
   "mcpServers": {
     "engram": {
       "args": [
-        "mcp"
+        "mcp",
+        "--tools=agent"
       ],
       "command": "/opt/homebrew/bin/engram"
     }
diff --git a/testdata/golden/skills-claude-skill-creator.golden b/testdata/golden/skills-claude-skill-creator.golden
index 182ec091b..3bf998f60 100644
--- a/testdata/golden/skills-claude-skill-creator.golden
+++ b/testdata/golden/skills-claude-skill-creator.golden
@@ -20,7 +20,8 @@ Do not create a skill when the pattern is trivial, one-off, or better served by
 ## Hard Rules
 
 - When working in this repo, first follow `docs/skill-style-guide.md` as the normative source before creating or updating skills.
-- If that guide is unavailable, use the compact inline rules below.
+- For installed global skills, use `references/skill-style-guide.md` as the bundled local copy of that guide when `docs/skill-style-guide.md` is unavailable.
+- If neither guide is available, use the compact inline rules below.
 - A skill is a runtime instruction contract for an LLM, not human documentation.
 - Do not add a `Keywords` section; preserve essential trigger words in `description`.
 - References must point to local files.
@@ -37,9 +38,10 @@ Do not create a skill when the pattern is trivial, one-off, or better served by
 
 ## Execution Steps
 
-1. Check whether `docs/skill-style-guide.md` exists; if it does, apply it before the inline fallback rules.
-2. Confirm the skill does not already exist and the pattern is reusable.
-3. Create or update `skills/{skill-name}/SKILL.md` using this required structure:
+1. Check whether `docs/skill-style-guide.md` exists; if it does, apply it before the bundled local copy or inline fallback rules.
+2. If the repo guide is unavailable, read `references/skill-style-guide.md` and apply it before the inline fallback rules.
+3. Confirm the skill does not already exist and the pattern is reusable.
+4. Create or update `skills/{skill-name}/SKILL.md` using this required structure:
 
 ```
 skills/{skill-name}/
@@ -50,7 +52,7 @@ skills/{skill-name}/
 └── references/           # Optional - links to local docs
     └── docs.md           # Points to docs/developer-guide/*.mdx
 ```
-4. Use this frontmatter shape:
+5. Use this frontmatter shape:
 
 ```markdown
 ---
@@ -62,8 +64,8 @@ metadata:
   version: "1.0"
 ---
 ```
-5. Write sections in this order: Activation Contract, Hard Rules, Decision Gates, Execution Steps, Output Contract, References.
-6. Register the skill in `AGENTS.md` when it is a project skill.
+6. Write sections in this order: Activation Contract, Hard Rules, Decision Gates, Execution Steps, Output Contract, References.
+7. Register the skill in `AGENTS.md` when it is a project skill.
 
 ## Inline Fallback Rules
 
@@ -99,3 +101,4 @@ Return:
 ## References
 
 - `docs/skill-style-guide.md` — normative LLM-first skill style guide for this repo.
+- `references/skill-style-guide.md` — bundled local copy for installed global skills when the repo doc is unavailable.
diff --git a/testdata/golden/skills-kiro-skill-creator.golden b/testdata/golden/skills-kiro-skill-creator.golden
index 182ec091b..3bf998f60 100644
--- a/testdata/golden/skills-kiro-skill-creator.golden
+++ b/testdata/golden/skills-kiro-skill-creator.golden
@@ -20,7 +20,8 @@ Do not create a skill when the pattern is trivial, one-off, or better served by
 ## Hard Rules
 
 - When working in this repo, first follow `docs/skill-style-guide.md` as the normative source before creating or updating skills.
-- If that guide is unavailable, use the compact inline rules below.
+- For installed global skills, use `references/skill-style-guide.md` as the bundled local copy of that guide when `docs/skill-style-guide.md` is unavailable.
+- If neither guide is available, use the compact inline rules below.
 - A skill is a runtime instruction contract for an LLM, not human documentation.
 - Do not add a `Keywords` section; preserve essential trigger words in `description`.
 - References must point to local files.
@@ -37,9 +38,10 @@ Do not create a skill when the pattern is trivial, one-off, or better served by
 
 ## Execution Steps
 
-1. Check whether `docs/skill-style-guide.md` exists; if it does, apply it before the inline fallback rules.
-2. Confirm the skill does not already exist and the pattern is reusable.
-3. Create or update `skills/{skill-name}/SKILL.md` using this required structure:
+1. Check whether `docs/skill-style-guide.md` exists; if it does, apply it before the bundled local copy or inline fallback rules.
+2. If the repo guide is unavailable, read `references/skill-style-guide.md` and apply it before the inline fallback rules.
+3. Confirm the skill does not already exist and the pattern is reusable.
+4. Create or update `skills/{skill-name}/SKILL.md` using this required structure:
 
 ```
 skills/{skill-name}/
@@ -50,7 +52,7 @@ skills/{skill-name}/
 └── references/           # Optional - links to local docs
     └── docs.md           # Points to docs/developer-guide/*.mdx
 ```
-4. Use this frontmatter shape:
+5. Use this frontmatter shape:
 
 ```markdown
 ---
@@ -62,8 +64,8 @@ metadata:
   version: "1.0"
 ---
 ```
-5. Write sections in this order: Activation Contract, Hard Rules, Decision Gates, Execution Steps, Output Contract, References.
-6. Register the skill in `AGENTS.md` when it is a project skill.
+6. Write sections in this order: Activation Contract, Hard Rules, Decision Gates, Execution Steps, Output Contract, References.
+7. Register the skill in `AGENTS.md` when it is a project skill.
 
 ## Inline Fallback Rules
 
@@ -99,3 +101,4 @@ Return:
 ## References
 
 - `docs/skill-style-guide.md` — normative LLM-first skill style guide for this repo.
+- `references/skill-style-guide.md` — bundled local copy for installed global skills when the repo doc is unavailable.
diff --git a/testdata/golden/skills-opencode-skill-creator.golden b/testdata/golden/skills-opencode-skill-creator.golden
index 182ec091b..3bf998f60 100644
--- a/testdata/golden/skills-opencode-skill-creator.golden
+++ b/testdata/golden/skills-opencode-skill-creator.golden
@@ -20,7 +20,8 @@ Do not create a skill when the pattern is trivial, one-off, or better served by
 ## Hard Rules
 
 - When working in this repo, first follow `docs/skill-style-guide.md` as the normative source before creating or updating skills.
-- If that guide is unavailable, use the compact inline rules below.
+- For installed global skills, use `references/skill-style-guide.md` as the bundled local copy of that guide when `docs/skill-style-guide.md` is unavailable.
+- If neither guide is available, use the compact inline rules below.
 - A skill is a runtime instruction contract for an LLM, not human documentation.
 - Do not add a `Keywords` section; preserve essential trigger words in `description`.
 - References must point to local files.
@@ -37,9 +38,10 @@ Do not create a skill when the pattern is trivial, one-off, or better served by
 
 ## Execution Steps
 
-1. Check whether `docs/skill-style-guide.md` exists; if it does, apply it before the inline fallback rules.
-2. Confirm the skill does not already exist and the pattern is reusable.
-3. Create or update `skills/{skill-name}/SKILL.md` using this required structure:
+1. Check whether `docs/skill-style-guide.md` exists; if it does, apply it before the bundled local copy or inline fallback rules.
+2. If the repo guide is unavailable, read `references/skill-style-guide.md` and apply it before the inline fallback rules.
+3. Confirm the skill does not already exist and the pattern is reusable.
+4. Create or update `skills/{skill-name}/SKILL.md` using this required structure:
 
 ```
 skills/{skill-name}/
@@ -50,7 +52,7 @@ skills/{skill-name}/
 └── references/           # Optional - links to local docs
     └── docs.md           # Points to docs/developer-guide/*.mdx
 ```
-4. Use this frontmatter shape:
+5. Use this frontmatter shape:
 
 ```markdown
 ---
@@ -62,8 +64,8 @@ metadata:
   version: "1.0"
 ---
 ```
-5. Write sections in this order: Activation Contract, Hard Rules, Decision Gates, Execution Steps, Output Contract, References.
-6. Register the skill in `AGENTS.md` when it is a project skill.
+6. Write sections in this order: Activation Contract, Hard Rules, Decision Gates, Execution Steps, Output Contract, References.
+7. Register the skill in `AGENTS.md` when it is a project skill.
 
 ## Inline Fallback Rules
 
@@ -99,3 +101,4 @@ Return:
 ## References
 
 - `docs/skill-style-guide.md` — normative LLM-first skill style guide for this repo.
+- `references/skill-style-guide.md` — bundled local copy for installed global skills when the repo doc is unavailable.
diff --git a/testdata/golden/skills-windsurf-skill-creator.golden b/testdata/golden/skills-windsurf-skill-creator.golden
index 182ec091b..3bf998f60 100644
--- a/testdata/golden/skills-windsurf-skill-creator.golden
+++ b/testdata/golden/skills-windsurf-skill-creator.golden
@@ -20,7 +20,8 @@ Do not create a skill when the pattern is trivial, one-off, or better served by
 ## Hard Rules
 
 - When working in this repo, first follow `docs/skill-style-guide.md` as the normative source before creating or updating skills.
-- If that guide is unavailable, use the compact inline rules below.
+- For installed global skills, use `references/skill-style-guide.md` as the bundled local copy of that guide when `docs/skill-style-guide.md` is unavailable.
+- If neither guide is available, use the compact inline rules below.
 - A skill is a runtime instruction contract for an LLM, not human documentation.
 - Do not add a `Keywords` section; preserve essential trigger words in `description`.
 - References must point to local files.
@@ -37,9 +38,10 @@ Do not create a skill when the pattern is trivial, one-off, or better served by
 
 ## Execution Steps
 
-1. Check whether `docs/skill-style-guide.md` exists; if it does, apply it before the inline fallback rules.
-2. Confirm the skill does not already exist and the pattern is reusable.
-3. Create or update `skills/{skill-name}/SKILL.md` using this required structure:
+1. Check whether `docs/skill-style-guide.md` exists; if it does, apply it before the bundled local copy or inline fallback rules.
+2. If the repo guide is unavailable, read `references/skill-style-guide.md` and apply it before the inline fallback rules.
+3. Confirm the skill does not already exist and the pattern is reusable.
+4. Create or update `skills/{skill-name}/SKILL.md` using this required structure:
 
 ```
 skills/{skill-name}/
@@ -50,7 +52,7 @@ skills/{skill-name}/
 └── references/           # Optional - links to local docs
     └── docs.md           # Points to docs/developer-guide/*.mdx
 ```
-4. Use this frontmatter shape:
+5. Use this frontmatter shape:
 
 ```markdown
 ---
@@ -62,8 +64,8 @@ metadata:
   version: "1.0"
 ---
 ```
-5. Write sections in this order: Activation Contract, Hard Rules, Decision Gates, Execution Steps, Output Contract, References.
-6. Register the skill in `AGENTS.md` when it is a project skill.
+6. Write sections in this order: Activation Contract, Hard Rules, Decision Gates, Execution Steps, Output Contract, References.
+7. Register the skill in `AGENTS.md` when it is a project skill.
 
 ## Inline Fallback Rules
 
@@ -99,3 +101,4 @@ Return:
 ## References
 
 - `docs/skill-style-guide.md` — normative LLM-first skill style guide for this repo.
+- `references/skill-style-guide.md` — bundled local copy for installed global skills when the repo doc is unavailable.