diff --git a/DESIGN.md b/DESIGN.md
index fce648d95..01ce6b2a0 100644
--- a/DESIGN.md
+++ b/DESIGN.md
@@ -77,6 +77,8 @@ When `migrateOnStart` opens a source LMDB primary store to read records out for
 
 Harper's normal `databases.ts` path already does this (search for `dbiInit.compression = primaryKeyAttribute.compression`); the migration path in `bin/copyDb.ts` has to match.
 
+The persisted `compression` value itself is LMDB-era and loosely shaped: `getDefaultCompression()` historically stored whatever falsy value the config resolved to (`''`, `false`, `null`) when `storage.compression` was disabled, and `{ startingOffset, threshold, dictionary? }` when enabled. lmdb-js interprets falsy as "no compression", but rocksdb-js >= 2.6 validates the option strictly (`''`/booleans throw `Unsupported compression algorithm`) and treats UNSET as "use the build default (lz4)" — the inverse default of lmdb. Every RocksDB open must therefore route through `toRocksCompression()` in `resources/databases.ts` (applied inside `openRocksDatabase`, the single chokepoint), which maps defined-falsy → `'none'` and `true` → unset. Don't pass persisted attribute compression to a RocksDB open directly.
+
 The same source-dbi open has a second non-obvious requirement: assign `sourceDbi.encoder.rootStore = sourceRootStore` for the primary store. The primary dbi decodes through a `RecordEncoder`, and decoding a record that holds a file-backed blob reference resolves that reference against `rootStore` (it locates the blob file). With `rootStore` unset, the `Blob` msgpackr extension throws `No store specified, cannot load blob from storage`; `RecordEncoder.decode` swallows the error and yields `null`, and `copyDbToRocks` then skips the `null` value — so every record with a file-backed blob is silently dropped from the migration. The runtime path gets `rootStore` from `handleLocalTimeForGets`; the migration path opens the source dbi raw and must set it explicitly (issue #857).
 
 ## Schema migration and `runIndexing` internals (`databases.ts`)
diff --git a/resources/databases.ts b/resources/databases.ts
index 027e6d14f..4cd676e82 100644
--- a/resources/databases.ts
+++ b/resources/databases.ts
@@ -176,8 +176,23 @@ export const databaseEventsEmitter = new EventEmitter<DatabaseWatcherEventMap>()
 export const tables: Tables = Object.create(null);
 export const databases: Databases = Object.create(null);
 
+/**
+ * Map a persisted (LMDB-era) compression value to what rocksdb-js accepts. Table metadata
+ * carries values where a defined falsy value (false, '') means compression was explicitly
+ * disabled and true/{ threshold, ... } mean enabled with defaults. rocksdb-js >= 2.6
+ * validates `compression` strictly and treats UNSET as "use the build default (lz4)", so
+ * disabled must be mapped to 'none' explicitly, and true to unset.
+ */
+export function toRocksCompression(compression: unknown): unknown {
+	if (compression === true) return undefined;
+	if (compression !== undefined && !compression) return 'none';
+	return compression;
+}
+
 function openRocksDatabase(path: string, options: RocksDatabaseOptions & { dupSort?: boolean }) {
 	options.disableWAL ??= true;
+	const legacyOptions = options as { compression?: unknown };
+	legacyOptions.compression = toRocksCompression(legacyOptions.compression);
 	// Apply read-only mode if enabled
 	if (isReadOnlyMode()) {
 		options.readOnly = true;
@@ -2265,7 +2280,9 @@ export function getDefaultCompression() {
 	if (STORAGE_COMPRESSION_DICTIONARY)
 		LMDB_COMPRESSION_OPTS['dictionary'] = readFileSync(STORAGE_COMPRESSION_DICTIONARY);
 	if (STORAGE_COMPRESSION_THRESHOLD) LMDB_COMPRESSION_OPTS['threshold'] = STORAGE_COMPRESSION_THRESHOLD;
-	return LMDB_COMPRESSION && LMDB_COMPRESSION_OPTS;
+	// normalize disabled to false so a falsy config value ('' or null) is never persisted
+	// into table metadata as-is (openRocksDatabase maps defined-falsy to 'none')
+	return LMDB_COMPRESSION ? LMDB_COMPRESSION_OPTS : false;
 }
 
 /**
diff --git a/unitTests/components/componentLoader.test.js b/unitTests/components/componentLoader.test.js
index 0c653cdc7..0b958c013 100644
--- a/unitTests/components/componentLoader.test.js
+++ b/unitTests/components/componentLoader.test.js
@@ -28,7 +28,9 @@ describe('ComponentLoader Status Integration', function () {
 			if (key === 'MAX_HEADER_SIZE') return 8192;
 			if (key === 'HTTP_PORT') return 9925;
 			if (key === 'CUSTOM_FUNCTIONS') return false;
-			return '';
+			// Unknown keys must read as unset — '' is a real (and sometimes invalid)
+			// config value, e.g. storage.compression rejects '' as an algorithm name
+			return undefined;
 		});
 
 		// Get both the lifecycle and internal objects
diff --git a/unitTests/components/startOnMainThreadOnce.test.js b/unitTests/components/startOnMainThreadOnce.test.js
index 4b63bbc1c..6c68cf071 100644
--- a/unitTests/components/startOnMainThreadOnce.test.js
+++ b/unitTests/components/startOnMainThreadOnce.test.js
@@ -32,7 +32,9 @@ describe('startOnMainThread once-per-component (#460)', function () {
 			if (key === 'MAX_HEADER_SIZE') return 8192;
 			if (key === 'HTTP_PORT') return 9925;
 			if (key === 'CUSTOM_FUNCTIONS') return false;
-			return '';
+			// Unknown keys must read as unset — '' is a real (and sometimes invalid)
+			// config value, e.g. storage.compression rejects '' as an algorithm name
+			return undefined;
 		});
 
 		const configUtils = require('#src/config/configUtils');
diff --git a/unitTests/resources/rocksCompression.test.js b/unitTests/resources/rocksCompression.test.js
new file mode 100644
index 000000000..9dd0de51d
--- /dev/null
+++ b/unitTests/resources/rocksCompression.test.js
@@ -0,0 +1,34 @@
+// Regression guard for the rocksdb-js 2.6 upgrade (HarperFast/harper#2036): persisted table
+// metadata carries LMDB-era compression values (false/'' = explicitly disabled, true/object =
+// enabled with defaults). rocksdb-js >= 2.6 validates the `compression` option strictly — a
+// bare '' or boolean throws ("Unsupported compression algorithm") — and treats UNSET as "use
+// the build default (lz4)", so disabled values must be mapped to 'none' before they reach a
+// RocksDB open.
+const assert = require('node:assert');
+const { toRocksCompression } = require('#src/resources/databases');
+
+describe('toRocksCompression', function () {
+	it('maps explicitly disabled values to none', function () {
+		assert.strictEqual(toRocksCompression(false), 'none');
+		assert.strictEqual(toRocksCompression(''), 'none');
+		assert.strictEqual(toRocksCompression(null), 'none');
+		assert.strictEqual(toRocksCompression(0), 'none');
+	});
+
+	it('maps true to unset so the build default applies', function () {
+		assert.strictEqual(toRocksCompression(true), undefined);
+	});
+
+	it('leaves unset unset (internal DBIs keep the build default)', function () {
+		assert.strictEqual(toRocksCompression(undefined), undefined);
+	});
+
+	it('passes through LMDB-era option objects (rocksdb-js treats a missing algorithm as unset)', function () {
+		const legacyOptions = { startingOffset: 32, threshold: 4036 };
+		assert.strictEqual(toRocksCompression(legacyOptions), legacyOptions);
+	});
+
+	it('passes through explicit algorithm names', function () {
+		assert.strictEqual(toRocksCompression('zstd'), 'zstd');
+	});
+});