diff --git a/packages/database-postgres/src/runner.ts b/packages/database-postgres/src/runner.ts
index 8d65f0a..f2f36c5 100644
--- a/packages/database-postgres/src/runner.ts
+++ b/packages/database-postgres/src/runner.ts
@@ -33,7 +33,7 @@
  */
 
 import type { Pool } from 'pg';
-import { MigrationLedger } from './ledger.js';
+import type { MigrationLedger } from './ledger.js';
 
 /**
  * A single migration step: an identifier (recorded in the ledger once the
@@ -136,14 +136,17 @@ export class MigrationRunner {
   private readonly migrations: readonly Migration[];
 
   /**
-   * @param pool The package-owned PostgreSQL pool (`pg.Pool`).
+   * @param pool The package-owned PostgreSQL pool (`pg.Pool`), handed to each
+   *   migration's `up`.
    * @param migrations The migrations to run, in apply order (oldest first).
-   * @param ledger The migration ledger; defaults to one sharing `pool`.
+   * @param ledger The migration ledger (E00-S03-T03) the runner reads applied
+   *   versions from and records applied migrations into; constructed by the
+   *   caller from the same pool (`new MigrationLedger(pool)`).
    */
-  constructor(pool: Pool, migrations: readonly Migration[], ledger?: MigrationLedger) {
+  constructor(pool: Pool, migrations: readonly Migration[], ledger: MigrationLedger) {
     this.pool = pool;
     this.migrations = migrations;
-    this.ledger = ledger ?? new MigrationLedger(pool);
+    this.ledger = ledger;
   }
 
   /**