diff --git a/internal/config/config.go b/internal/config/config.go
index deea2049..303f6ea3 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -71,7 +71,7 @@ type Config struct {
 	// WebsocketAuth enables or disables authentication for the WebSocket API.
 	WebsocketAuth bool `yaml:"ws-auth" json:"ws-auth"`
 
-	// CodexInstructionsEnabled controls whether custom Codex instructions are injected.
+	// CodexInstructionsEnabled controls whether official Codex instructions are injected.
 	// When false (default), CodexInstructionsForModel returns immediately without modification.
 	// When true, the original instruction injection logic is used.
 	CodexInstructionsEnabled bool `yaml:"codex-instructions-enabled" json:"codex-instructions-enabled"`
diff --git a/internal/config/oauth_model_alias_migration.go b/internal/config/oauth_model_alias_migration.go
index 0e3b2156..5cc8053a 100644
--- a/internal/config/oauth_model_alias_migration.go
+++ b/internal/config/oauth_model_alias_migration.go
@@ -122,6 +122,23 @@ func migrateFromOldField(configFile string, root *yaml.Node, rootMap *yaml.Node,
 		newAliases[channel] = converted
 	}
 
+	// For antigravity channel, supplement missing default aliases
+	if antigravityEntries, exists := newAliases["antigravity"]; exists {
+		// Build a set of already configured model names (upstream names)
+		configuredModels := make(map[string]bool, len(antigravityEntries))
+		for _, entry := range antigravityEntries {
+			configuredModels[entry.Name] = true
+		}
+
+		// Add missing default aliases
+		for _, defaultAlias := range defaultAntigravityAliases() {
+			if !configuredModels[defaultAlias.Name] {
+				antigravityEntries = append(antigravityEntries, defaultAlias)
+			}
+		}
+		newAliases["antigravity"] = antigravityEntries
+	}
+
 	// Build new node
 	newNode := buildOAuthModelAliasNode(newAliases)
 
diff --git a/internal/config/oauth_model_alias_migration_test.go b/internal/config/oauth_model_alias_migration_test.go
index ab5a1f49..db9c0a11 100644
--- a/internal/config/oauth_model_alias_migration_test.go
+++ b/internal/config/oauth_model_alias_migration_test.go
@@ -114,6 +114,23 @@ func TestMigrateOAuthModelAlias_ConvertsAntigravityModels(t *testing.T) {
 	if !strings.Contains(content, "gemini-3-pro-high") {
 		t.Fatal("expected gemini-3-pro-preview to be converted to gemini-3-pro-high")
 	}
+
+	// Verify missing default aliases were supplemented
+	if !strings.Contains(content, "gemini-3-pro-image") {
+		t.Fatal("expected missing default alias gemini-3-pro-image to be added")
+	}
+	if !strings.Contains(content, "gemini-3-flash") {
+		t.Fatal("expected missing default alias gemini-3-flash to be added")
+	}
+	if !strings.Contains(content, "claude-sonnet-4-5") {
+		t.Fatal("expected missing default alias claude-sonnet-4-5 to be added")
+	}
+	if !strings.Contains(content, "claude-sonnet-4-5-thinking") {
+		t.Fatal("expected missing default alias claude-sonnet-4-5-thinking to be added")
+	}
+	if !strings.Contains(content, "claude-opus-4-5-thinking") {
+		t.Fatal("expected missing default alias claude-opus-4-5-thinking to be added")
+	}
 }
 
 func TestMigrateOAuthModelAlias_AddsDefaultIfNeitherExists(t *testing.T) {
diff --git a/internal/runtime/executor/antigravity_executor.go b/internal/runtime/executor/antigravity_executor.go
index d2001a71..7ae50e39 100644
--- a/internal/runtime/executor/antigravity_executor.go
+++ b/internal/runtime/executor/antigravity_executor.go
@@ -1221,7 +1221,7 @@ func (e *AntigravityExecutor) buildRequest(ctx context.Context, auth *cliproxyau
 		payload = []byte(strJSON)
 	}
 
-	if strings.Contains(modelName, "claude") || strings.Contains(modelName, "gemini-3-pro-preview") {
+	if strings.Contains(modelName, "claude") || strings.Contains(modelName, "gemini-3-pro-high") {
 		systemInstructionPartsResult := gjson.GetBytes(payload, "request.systemInstruction.parts")
 		payload, _ = sjson.SetBytes(payload, "request.systemInstruction.role", "user")
 		payload, _ = sjson.SetBytes(payload, "request.systemInstruction.parts.0.text", systemInstruction)
diff --git a/internal/runtime/executor/codex_executor.go b/internal/runtime/executor/codex_executor.go
index 273987ea..0abec8af 100644
--- a/internal/runtime/executor/codex_executor.go
+++ b/internal/runtime/executor/codex_executor.go
@@ -106,6 +106,9 @@ func (e *CodexExecutor) Execute(ctx context.Context, auth *cliproxyauth.Auth, re
 	body, _ = sjson.SetBytes(body, "stream", true)
 	body, _ = sjson.DeleteBytes(body, "previous_response_id")
 	body, _ = sjson.DeleteBytes(body, "prompt_cache_retention")
+	if !gjson.GetBytes(body, "instructions").Exists() {
+		body, _ = sjson.SetBytes(body, "instructions", "")
+	}
 
 	url := strings.TrimSuffix(baseURL, "/") + "/responses"
 	httpReq, err := e.cacheHelper(ctx, from, url, req, body)
@@ -213,6 +216,9 @@ func (e *CodexExecutor) ExecuteStream(ctx context.Context, auth *cliproxyauth.Au
 	body, _ = sjson.DeleteBytes(body, "previous_response_id")
 	body, _ = sjson.DeleteBytes(body, "prompt_cache_retention")
 	body, _ = sjson.SetBytes(body, "model", baseModel)
+	if !gjson.GetBytes(body, "instructions").Exists() {
+		body, _ = sjson.SetBytes(body, "instructions", "")
+	}
 
 	url := strings.TrimSuffix(baseURL, "/") + "/responses"
 	httpReq, err := e.cacheHelper(ctx, from, url, req, body)
@@ -317,6 +323,9 @@ func (e *CodexExecutor) CountTokens(ctx context.Context, auth *cliproxyauth.Auth
 	body, _ = sjson.DeleteBytes(body, "previous_response_id")
 	body, _ = sjson.DeleteBytes(body, "prompt_cache_retention")
 	body, _ = sjson.SetBytes(body, "stream", false)
+	if !gjson.GetBytes(body, "instructions").Exists() {
+		body, _ = sjson.SetBytes(body, "instructions", "")
+	}
 
 	enc, err := tokenizerForCodexModel(baseModel)
 	if err != nil {