diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f43e7f3..a931756 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -145,6 +145,15 @@ jobs:
           ccache -s
           make GEN=Ninja nodejs && ccache -s
 
+      - name: Install OpenSSL 3 (macOS)
+        if: ${{ matrix.mac_env }}
+        run: |
+          # Pin to OpenSSL 3: Homebrew now also ships openssl@4, which CMake
+          # would otherwise prefer. The top-level CMakeLists enforces OpenSSL 3
+          # via a version guard, so point CMake at openssl@3 explicitly.
+          brew list openssl@3 >/dev/null 2>&1 || brew install openssl@3
+          echo "OPENSSL_ROOT_DIR=$(brew --prefix openssl@3)" >> "$GITHUB_ENV"
+
       - name: Build Node.js native module (non-Windows)
         if: ${{ matrix.platform != 'win32' }}
         run: make GEN=Ninja nodejs
diff --git a/src_cpp/include/node_database.h b/src_cpp/include/node_database.h
index e171961..85b67bc 100644
--- a/src_cpp/include/node_database.h
+++ b/src_cpp/include/node_database.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <memory>
+#include <optional>
 
 #include "main/lbug.h"
 #include <napi.h>
@@ -26,15 +27,15 @@ class NodeDatabase : public Napi::ObjectWrap<NodeDatabase> {
 
 private:
     std::string databasePath;
-    size_t bufferPoolSize;
-    bool enableCompression;
-    bool readOnly;
-    uint64_t maxDBSize;
-    bool autoCheckpoint;
-    int64_t checkpointThreshold;
-    bool throwOnWalReplayFailure;
-    bool enableChecksums;
-    bool enableDefaultHashIndex;
+    std::optional<int64_t> bufferPoolSize;
+    std::optional<bool> enableCompression;
+    std::optional<bool> readOnly;
+    std::optional<int64_t> maxDBSize;
+    std::optional<bool> autoCheckpoint;
+    std::optional<int64_t> checkpointThreshold;
+    std::optional<bool> throwOnWalReplayFailure;
+    std::optional<bool> enableChecksums;
+    std::optional<bool> enableDefaultHashIndex;
     std::shared_ptr<Database> database;
 };
 
diff --git a/src_cpp/node_database.cpp b/src_cpp/node_database.cpp
index 1cb92b3..57cab92 100644
--- a/src_cpp/node_database.cpp
+++ b/src_cpp/node_database.cpp
@@ -16,19 +16,60 @@ Napi::Object NodeDatabase::Init(Napi::Env env, Napi::Object exports) {
     return exports;
 }
 
+namespace {
+
+// Null/undefined means "use the engine default"; the setting is left unset.
+bool getOptionalInt64(const Napi::CallbackInfo& info, size_t index, int64_t& out) {
+    if (index >= info.Length() || info[index].IsNull() || info[index].IsUndefined()) {
+        return false;
+    }
+    out = info[index].As<Napi::Number>().Int64Value();
+    return true;
+}
+
+bool getOptionalBool(const Napi::CallbackInfo& info, size_t index, bool& out) {
+    if (index >= info.Length() || info[index].IsNull() || info[index].IsUndefined()) {
+        return false;
+    }
+    out = info[index].As<Napi::Boolean>().Value();
+    return true;
+}
+
+} // namespace
+
 NodeDatabase::NodeDatabase(const Napi::CallbackInfo& info) : Napi::ObjectWrap<NodeDatabase>(info) {
     Napi::Env env = info.Env();
     Napi::HandleScope scope(env);
     databasePath = info[0].ToString();
-    bufferPoolSize = info[1].As<Napi::Number>().Int64Value();
-    enableCompression = info[2].As<Napi::Boolean>().Value();
-    readOnly = info[3].As<Napi::Boolean>().Value();
-    maxDBSize = info[4].As<Napi::Number>().Int64Value();
-    autoCheckpoint = info[5].As<Napi::Boolean>().Value();
-    checkpointThreshold = info[6].As<Napi::Number>().Int64Value();
-    throwOnWalReplayFailure = info[7].As<Napi::Boolean>().Value();
-    enableChecksums = info[8].As<Napi::Boolean>().Value();
-    enableDefaultHashIndex = info[9].As<Napi::Boolean>().Value();
+    int64_t intValue = 0;
+    bool boolValue = false;
+    if (getOptionalInt64(info, 1, intValue)) {
+        bufferPoolSize = intValue;
+    }
+    if (getOptionalBool(info, 2, boolValue)) {
+        enableCompression = boolValue;
+    }
+    if (getOptionalBool(info, 3, boolValue)) {
+        readOnly = boolValue;
+    }
+    if (getOptionalInt64(info, 4, intValue)) {
+        maxDBSize = intValue;
+    }
+    if (getOptionalBool(info, 5, boolValue)) {
+        autoCheckpoint = boolValue;
+    }
+    if (getOptionalInt64(info, 6, intValue)) {
+        checkpointThreshold = intValue;
+    }
+    if (getOptionalBool(info, 7, boolValue)) {
+        throwOnWalReplayFailure = boolValue;
+    }
+    if (getOptionalBool(info, 8, boolValue)) {
+        enableChecksums = boolValue;
+    }
+    if (getOptionalBool(info, 9, boolValue)) {
+        enableDefaultHashIndex = boolValue;
+    }
 }
 
 Napi::Value NodeDatabase::InitSync(const Napi::CallbackInfo& info) {
@@ -54,23 +95,35 @@ Napi::Value NodeDatabase::InitAsync(const Napi::CallbackInfo& info) {
 }
 
 void NodeDatabase::InitCppDatabase() {
+    // Start from the engine defaults and only apply explicitly set settings,
+    // so engine-side default changes propagate automatically.
     auto systemConfig = SystemConfig();
-    if (bufferPoolSize > 0) {
-        systemConfig.bufferPoolSize = bufferPoolSize;
-    }
-    if (!enableCompression) {
-        systemConfig.enableCompression = enableCompression;
-    }
-    systemConfig.readOnly = readOnly;
-    if (maxDBSize > 0) {
-        systemConfig.maxDBSize = maxDBSize;
-    }
-    systemConfig.autoCheckpoint = autoCheckpoint;
-    systemConfig.throwOnWalReplayFailure = throwOnWalReplayFailure;
-    systemConfig.enableChecksums = enableChecksums;
-    systemConfig.enableDefaultHashIndex = enableDefaultHashIndex;
-    if (checkpointThreshold >= 0) {
-        systemConfig.checkpointThreshold = checkpointThreshold;
+    if (bufferPoolSize && *bufferPoolSize > 0) {
+        systemConfig.bufferPoolSize = static_cast<uint64_t>(*bufferPoolSize);
+    }
+    if (enableCompression) {
+        systemConfig.enableCompression = *enableCompression;
+    }
+    if (readOnly) {
+        systemConfig.readOnly = *readOnly;
+    }
+    if (maxDBSize && *maxDBSize > 0) {
+        systemConfig.maxDBSize = static_cast<uint64_t>(*maxDBSize);
+    }
+    if (autoCheckpoint) {
+        systemConfig.autoCheckpoint = *autoCheckpoint;
+    }
+    if (throwOnWalReplayFailure) {
+        systemConfig.throwOnWalReplayFailure = *throwOnWalReplayFailure;
+    }
+    if (enableChecksums) {
+        systemConfig.enableChecksums = *enableChecksums;
+    }
+    if (enableDefaultHashIndex) {
+        systemConfig.enableDefaultHashIndex = *enableDefaultHashIndex;
+    }
+    if (checkpointThreshold && *checkpointThreshold >= 0) {
+        systemConfig.checkpointThreshold = static_cast<uint64_t>(*checkpointThreshold);
     }
     this->database = std::make_shared<Database>(databasePath, systemConfig);
 }
diff --git a/src_js/database.js b/src_js/database.js
index efee804..ab79624 100644
--- a/src_js/database.js
+++ b/src_js/database.js
@@ -11,34 +11,39 @@ class Database {
    *
    * @param {String} databasePath path to the database file. If the path is not specified, or empty, or equal to
    `:memory:`, the database will be created in memory.
-   * @param {Number} bufferManagerSize size of the buffer manager in bytes.
-   * @param {Boolean} enableCompression whether to enable compression.
-   * @param {Boolean} readOnly if true, database will be opened in read-only mode.
-   * @param {Number} maxDBSize maximum size of the database file in bytes. Note that
+   * @param {Number|null} bufferManagerSize size of the buffer manager in bytes. Null (default) uses the engine default.
+   * @param {Boolean|null} enableCompression whether to enable compression. Null (default) uses the engine default.
+   * @param {Boolean|null} readOnly if true, database will be opened in read-only mode. Null (default) uses the engine default.
+   * @param {Number|null} maxDBSize maximum size of the database file in bytes. Note that
    * this is introduced temporarily for now to get around with the default 8TB mmap
-   * address space limit some environment.
-   * @param {Boolean} autoCheckpoint If true, the database will automatically checkpoint when the size of
-   * the WAL file exceeds the checkpoint threshold.
-   * @param {Number} checkpointThreshold The threshold of the WAL file size in bytes. When the size of the
+   * address space limit some environment. Null (default) uses the engine default.
+   * @param {Boolean|null} autoCheckpoint If true, the database will automatically checkpoint when the size of
+   * the WAL file exceeds the checkpoint threshold. Null (default) uses the engine default.
+   * @param {Number|null} checkpointThreshold The threshold of the WAL file size in bytes. When the size of the
    * WAL file exceeds this threshold, the database will checkpoint if autoCheckpoint is true.
-   * @param {Boolean} throwOnWalReplayFailure If true, any WAL replaying failure when loading the database
+   * Null (default) uses the engine default.
+   * @param {Boolean|null} throwOnWalReplayFailure If true, any WAL replaying failure when loading the database
    * will throw an error. Otherwise, Lbug will silently ignore the failure and replay up to where
-   * the error occured.
-   * @param {Boolean} enableChecksums If true, the database will use checksums to detect corruption in the
-   * WAL file.
-   * @param {Boolean} enableDefaultHashIndex If true, node tables create the default primary-key hash index.
+   * the error occured. Null (default) uses the engine default.
+   * @param {Boolean|null} enableChecksums If true, the database will use checksums to detect corruption in the
+   * WAL file. Null (default) uses the engine default.
+   * @param {Boolean|null} enableDefaultHashIndex If true, node tables create the default primary-key hash index.
+   * Null (default) uses the engine default.
+   *
+   * Any setting left as null/undefined is not forwarded, so the engine default applies and
+   * engine-side default changes propagate automatically.
    */
   constructor(
     databasePath,
-    bufferManagerSize = 0,
-    enableCompression = true,
-    readOnly = false,
-    maxDBSize = 0,
-    autoCheckpoint = true,
-    checkpointThreshold = -1,
-    throwOnWalReplayFailure = true,
-    enableChecksums = true,
-    enableDefaultHashIndex = true,
+    bufferManagerSize = null,
+    enableCompression = null,
+    readOnly = null,
+    maxDBSize = null,
+    autoCheckpoint = null,
+    checkpointThreshold = null,
+    throwOnWalReplayFailure = null,
+    enableChecksums = null,
+    enableDefaultHashIndex = null,
   ) {
     if (!databasePath) {
       databasePath = ":memory:";
@@ -46,18 +51,26 @@ class Database {
     else if (typeof databasePath !== "string") {
       throw new Error("Database path must be a string.");
     }
-    if (typeof bufferManagerSize !== "number" || bufferManagerSize < 0) {
+    if (bufferManagerSize != null && (typeof bufferManagerSize !== "number" || bufferManagerSize < 0)) {
       throw new Error("Buffer manager size must be a positive integer.");
     }
-    if (typeof maxDBSize !== "number" || maxDBSize < 0) {
+    if (maxDBSize != null && (typeof maxDBSize !== "number" || maxDBSize < 0)) {
       throw new Error("Max DB size must be a positive integer.");
     }
-    if (typeof checkpointThreshold !== "number" || maxDBSize < -1) {
+    // Note: negative explicit values (e.g. the historical -1 default) are accepted here and
+    // ignored by the native layer, which keeps the engine default for them.
+    if (checkpointThreshold != null && typeof checkpointThreshold !== "number") {
       throw new Error("Checkpoint threshold must be a positive integer.");
     }
-    bufferManagerSize = Math.floor(bufferManagerSize);
-    maxDBSize = Math.floor(maxDBSize);
-    checkpointThreshold = Math.floor(checkpointThreshold);
+    if (bufferManagerSize != null) {
+      bufferManagerSize = Math.floor(bufferManagerSize);
+    }
+    if (maxDBSize != null) {
+      maxDBSize = Math.floor(maxDBSize);
+    }
+    if (checkpointThreshold != null) {
+      checkpointThreshold = Math.floor(checkpointThreshold);
+    }
     this._database = new LbugNative.NodeDatabase(
       databasePath,
       bufferManagerSize,
diff --git a/src_js/lbug.d.ts b/src_js/lbug.d.ts
index 9a2217b..8ab7e7f 100644
--- a/src_js/lbug.d.ts
+++ b/src_js/lbug.d.ts
@@ -104,21 +104,24 @@ export type LbugValue =
 
 /**
  * Configuration options for the database system.
+ *
+ * Any option left undefined uses the engine default; explicitly set options
+ * override the engine configuration.
  */
 export interface SystemConfig {
-    /** Size of the buffer pool in bytes */
+    /** Size of the buffer pool in bytes (engine default if omitted) */
     bufferPoolSize?: number;
-    /** Whether to enable compression */
+    /** Whether to enable compression (engine default if omitted) */
     enableCompression?: boolean;
-    /** Whether to open the database in read-only mode */
+    /** Whether to open the database in read-only mode (engine default if omitted) */
     readOnly?: boolean;
-    /** Maximum size of the database in bytes */
+    /** Maximum size of the database in bytes (engine default if omitted) */
     maxDBSize?: number;
-    /** Whether to enable automatic checkpoints */
+    /** Whether to enable automatic checkpoints (engine default if omitted) */
     autoCheckpoint?: boolean;
-    /** Threshold for automatic checkpoints */
+    /** Threshold for automatic checkpoints (engine default if omitted) */
     checkpointThreshold?: number;
-    /** Whether node tables create the default primary-key hash index */
+    /** Whether node tables create the default primary-key hash index (engine default if omitted) */
     enableDefaultHashIndex?: boolean;
 }
 
@@ -132,17 +135,18 @@ export function json(value: string | LbugValue): LbugValue;
  */
 export class Database {
     /**
-     * Constructs a new Database instance.
+     * Constructs a new Database instance. Any setting left undefined/null uses
+     * the engine default; explicitly set settings override it.
      * @param databasePath Path to the database directory (defaults to ":memory:")
-     * @param bufferManagerSize Size of the buffer manager in bytes
-     * @param enableCompression Whether to enable compression
-     * @param readOnly Whether to open in read-only mode
-     * @param maxDBSize Maximum size of the database in bytes
-     * @param autoCheckpoint Whether to enable automatic checkpoints
-     * @param checkpointThreshold Threshold for automatic checkpoints
-     * @param throwOnWalReplayFailure Whether WAL replay failures should throw
-     * @param enableChecksums Whether checksum validation is enabled
-     * @param enableDefaultHashIndex Whether node tables create the default primary-key hash index
+     * @param bufferManagerSize Size of the buffer manager in bytes (engine default if omitted)
+     * @param enableCompression Whether to enable compression (engine default if omitted)
+     * @param readOnly Whether to open in read-only mode (engine default if omitted)
+     * @param maxDBSize Maximum size of the database in bytes (engine default if omitted)
+     * @param autoCheckpoint Whether to enable automatic checkpoints (engine default if omitted)
+     * @param checkpointThreshold Threshold for automatic checkpoints (engine default if omitted)
+     * @param throwOnWalReplayFailure Whether WAL replay failures should throw (engine default if omitted)
+     * @param enableChecksums Whether checksum validation is enabled (engine default if omitted)
+     * @param enableDefaultHashIndex Whether node tables create the default primary-key hash index (engine default if omitted)
      */
     constructor(
         databasePath?: string,