diff --git a/internal/api/handlers/management/config_lists.go b/internal/api/handlers/management/config_lists.go
index 5cca03ba..0153a381 100644
--- a/internal/api/handlers/management/config_lists.go
+++ b/internal/api/handlers/management/config_lists.go
@@ -796,10 +796,10 @@ func (h *Handler) DeleteOAuthModelAlias(c *gin.Context) {
 		c.JSON(404, gin.H{"error": "channel not found"})
 		return
 	}
-	delete(h.cfg.OAuthModelAlias, channel)
-	if len(h.cfg.OAuthModelAlias) == 0 {
-		h.cfg.OAuthModelAlias = nil
-	}
+	// Set to nil instead of deleting the key so that the "explicitly disabled"
+	// marker survives config reload and prevents SanitizeOAuthModelAlias from
+	// re-injecting default aliases (fixes #222).
+	h.cfg.OAuthModelAlias[channel] = nil
 	h.persist(c)
 }
 
diff --git a/internal/config/config.go b/internal/config/config.go
index 50b3cbd5..88e1c605 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -767,7 +767,13 @@ func (cfg *Config) SanitizeOAuthModelAlias() {
 	out := make(map[string][]OAuthModelAlias, len(cfg.OAuthModelAlias))
 	for rawChannel, aliases := range cfg.OAuthModelAlias {
 		channel := strings.ToLower(strings.TrimSpace(rawChannel))
-		if channel == "" || len(aliases) == 0 {
+		if channel == "" {
+			continue
+		}
+		// Preserve channels that were explicitly set to empty/nil – they act
+		// as "disabled" markers so default injection won't re-add them (#222).
+		if len(aliases) == 0 {
+			out[channel] = nil
 			continue
 		}
 		seenAlias := make(map[string]struct{}, len(aliases))
diff --git a/internal/config/oauth_model_alias_test.go b/internal/config/oauth_model_alias_test.go
index 7497eec8..5cf05502 100644
--- a/internal/config/oauth_model_alias_test.go
+++ b/internal/config/oauth_model_alias_test.go
@@ -128,6 +128,50 @@ func TestSanitizeOAuthModelAlias_DoesNotOverrideUserKiroAliases(t *testing.T) {
 	}
 }
 
+func TestSanitizeOAuthModelAlias_DoesNotReinjectAfterExplicitDeletion(t *testing.T) {
+	// When user explicitly deletes kiro aliases (key exists with nil value),
+	// defaults should NOT be re-injected on subsequent sanitize calls (#222).
+	cfg := &Config{
+		OAuthModelAlias: map[string][]OAuthModelAlias{
+			"kiro":  nil, // explicitly deleted
+			"codex": {{Name: "gpt-5", Alias: "g5"}},
+		},
+	}
+
+	cfg.SanitizeOAuthModelAlias()
+
+	kiroAliases := cfg.OAuthModelAlias["kiro"]
+	if len(kiroAliases) != 0 {
+		t.Fatalf("expected kiro aliases to remain empty after explicit deletion, got %d aliases", len(kiroAliases))
+	}
+	// The key itself must still be present to prevent re-injection on next reload
+	if _, exists := cfg.OAuthModelAlias["kiro"]; !exists {
+		t.Fatal("expected kiro key to be preserved as nil marker after sanitization")
+	}
+	// Other channels should be unaffected
+	if len(cfg.OAuthModelAlias["codex"]) != 1 {
+		t.Fatal("expected codex aliases to be preserved")
+	}
+}
+
+func TestSanitizeOAuthModelAlias_DoesNotReinjectAfterExplicitDeletionEmpty(t *testing.T) {
+	// Same as above but with empty slice instead of nil (PUT with empty body).
+	cfg := &Config{
+		OAuthModelAlias: map[string][]OAuthModelAlias{
+			"kiro": {}, // explicitly set to empty
+		},
+	}
+
+	cfg.SanitizeOAuthModelAlias()
+
+	if len(cfg.OAuthModelAlias["kiro"]) != 0 {
+		t.Fatalf("expected kiro aliases to remain empty, got %d aliases", len(cfg.OAuthModelAlias["kiro"]))
+	}
+	if _, exists := cfg.OAuthModelAlias["kiro"]; !exists {
+		t.Fatal("expected kiro key to be preserved")
+	}
+}
+
 func TestSanitizeOAuthModelAlias_InjectsDefaultKiroWhenEmpty(t *testing.T) {
 	// When OAuthModelAlias is nil, kiro defaults should still be injected
 	cfg := &Config{}