diff --git a/README.md b/README.md
index 3b016088..92a32f40 100644
--- a/README.md
+++ b/README.md
@@ -31,12 +31,21 @@
 
 The connector is configured using a YAML file that defines:
 
-- **Database Connection**: Connection details via DSN (Data Source Name)
+- **Database Connection**: Connection details via DSN (Data Source Name) and optional `connect.params`
 - **Resource Types**: Map database tables/queries to resources (users, roles, etc.)
 - **Account Provisioning**: Define schemas and credential options for user creation
 - **Entitlements**: Permissions and roles that can be granted to resources
 - **Provisioning Actions**: SQL queries for granting/revoking entitlements
 
+For Postgres behind a transaction-mode pooler (PgBouncer, Supabase pooler on port 6543, etc.), set `default_query_exec_mode` to `simple_protocol` via the DSN query string or `connect.params` to avoid prepared-statement conflicts (SQLSTATE 42P05). When unset, baton-sql leaves the URL unchanged and pgx uses its default (`cache_statement`).
+
+```yaml
+connect:
+  dsn: "postgres://${HOST}:6543/${DB}"
+  params:
+    default_query_exec_mode: simple_protocol
+```
+
 See examples in the [examples](https://github.com/ConductorOne/baton-sql/tree/main/examples) directory.
 
 ### Query placeholders
diff --git a/examples/redshift-test.yml b/examples/redshift-test.yml
index f8c1a422..7a7b9718 100644
--- a/examples/redshift-test.yml
+++ b/examples/redshift-test.yml
@@ -38,7 +38,7 @@
 #
 # Driver caveat: baton-sql uses jackc/pgx/v5 for the postgres scheme. If prepared-
 # statement quirks surface, pin to simple-query protocol via the DSN parameter
-# default_query_exec_mode=simple_protocol.
+# default_query_exec_mode=simple_protocol (or connect.params).
 app_name: Amazon Redshift
 app_description: Sync Redshift cluster identities, roles, groups, schemas, and tables.
 
diff --git a/pkg/database/database_test.go b/pkg/database/database_test.go
index 2e2fab9b..6ee8b3ee 100644
--- a/pkg/database/database_test.go
+++ b/pkg/database/database_test.go
@@ -804,3 +804,115 @@ func Test_buildConnectionURL(t *testing.T) {
 		})
 	}
 }
+
+func Test_buildConnectionURL_PostgresQueryExecMode(t *testing.T) {
+	const modeKey = "default_query_exec_mode"
+
+	tests := []struct {
+		name      string
+		opts      ConnectOptions
+		wantMode  string // empty means key must be absent
+		wantOther map[string]string
+	}{
+		{
+			name: "unset postgres DSN does not inject default_query_exec_mode",
+			opts: ConnectOptions{
+				DSN: "postgres://user:pass@localhost:5432/db",
+			},
+			wantMode: "",
+		},
+		{
+			name: "structured postgres with sslmode only has no mode key",
+			opts: ConnectOptions{
+				Scheme:   "postgres",
+				Host:     "db.example",
+				Port:     "5432",
+				Database: "app",
+				User:     "u",
+				Password: "p",
+				Params: map[string]string{
+					"sslmode": "require",
+				},
+			},
+			wantMode: "",
+			wantOther: map[string]string{
+				"sslmode": "require",
+			},
+		},
+		{
+			name: "DSN already sets cache_statement is preserved",
+			opts: ConnectOptions{
+				DSN: "postgres://user:pass@localhost:5432/db?default_query_exec_mode=cache_statement",
+			},
+			wantMode: "cache_statement",
+		},
+		{
+			name: "Params set exec is preserved",
+			opts: ConnectOptions{
+				Scheme:   "postgres",
+				Host:     "db.example",
+				Database: "app",
+				Params: map[string]string{
+					"default_query_exec_mode": "exec",
+				},
+			},
+			wantMode: "exec",
+		},
+		{
+			name: "Params set simple_protocol is preserved",
+			opts: ConnectOptions{
+				Scheme:   "postgres",
+				Host:     "db.example",
+				Database: "app",
+				Params: map[string]string{
+					"default_query_exec_mode": "simple_protocol",
+				},
+			},
+			wantMode: "simple_protocol",
+		},
+		{
+			name: "mysql scheme does not inject mode",
+			opts: ConnectOptions{
+				Scheme:   "mysql",
+				Host:     "db.example",
+				Port:     "3306",
+				Database: "app",
+				User:     "u",
+				Password: "p",
+			},
+			wantMode: "",
+		},
+		{
+			name: "mysql DSN does not inject mode",
+			opts: ConnectOptions{
+				DSN: "mysql://user:pass@localhost:3306/db",
+			},
+			wantMode: "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := buildConnectionURL(tt.opts)
+			if err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+
+			q := got.Query()
+			gotMode := q.Get(modeKey)
+			if gotMode != tt.wantMode {
+				t.Fatalf("%s = %q, want %q (url=%s)", modeKey, gotMode, tt.wantMode, got.String())
+			}
+			if tt.wantMode == "" {
+				if _, ok := q[modeKey]; ok {
+					t.Fatalf("%s present when unset: %s", modeKey, got.String())
+				}
+			}
+			for k, want := range tt.wantOther {
+				if got := q.Get(k); got != want {
+					t.Fatalf("query %s = %q, want %q", k, got, want)
+				}
+			}
+		})
+	}
+}