diff --git a/lib/server/db/index.test.ts b/lib/server/db/index.test.ts
index 32fd6ea..a8156ae 100644
--- a/lib/server/db/index.test.ts
+++ b/lib/server/db/index.test.ts
@@ -199,4 +199,35 @@ describe('sqlite schema compatibility bootstrap', () => {
 
     client.close();
   });
+
+  it('throws on missing parser_engine column when verifyCriticalSchema is called', () => {
+    const client = new Database(':memory:');
+    client.exec('PRAGMA foreign_keys = ON;');
+
+    applyMigration(client, '0000_cold_silver_centurion.sql');
+    applyMigration(client, '0005_financial_taxonomy_v3.sql');
+
+    expect(__dbInternals.hasTable(client, 'filing_taxonomy_snapshot')).toBe(true);
+    expect(__dbInternals.hasColumn(client, 'filing_taxonomy_snapshot', 'parser_engine')).toBe(false);
+
+    expect(() => __dbInternals.verifyCriticalSchema(client)).toThrow(
+      /filing_taxonomy_snapshot is missing columns: parser_engine/
+    );
+
+    client.close();
+  });
+
+  it('verifyCriticalSchema passes when all required columns exist', () => {
+    const client = new Database(':memory:');
+    client.exec('PRAGMA foreign_keys = ON;');
+
+    applyMigration(client, '0000_cold_silver_centurion.sql');
+    applyMigration(client, '0005_financial_taxonomy_v3.sql');
+
+    __dbInternals.ensureLocalSqliteSchema(client);
+
+    expect(() => __dbInternals.verifyCriticalSchema(client)).not.toThrow();
+
+    client.close();
+  });
 });
diff --git a/lib/server/db/index.ts b/lib/server/db/index.ts
index f88ab89..6459da5 100644
--- a/lib/server/db/index.ts
+++ b/lib/server/db/index.ts
@@ -11,7 +11,8 @@ import { schema } from './schema';
 import {
   ensureLocalSqliteSchema,
   hasColumn,
-  hasTable
+  hasTable,
+  TAXONOMY_SNAPSHOT_REQUIRED_COLUMNS
 } from './sqlite-schema-compat';
 
 type AppDrizzleDb = ReturnType<typeof createDb>;
@@ -132,6 +133,27 @@ function ensureSearchVirtualTables(client: Database) {
   client.exec('CREATE INDEX IF NOT EXISTS `search_chunk_vec_lookup_idx` ON `search_chunk_vec` (`scope`, `user_id`, `source_kind`, `ticker`);');
 }
 
+function verifyCriticalSchema(client: Database) {
+  if (!hasTable(client, 'filing_taxonomy_snapshot')) {
+    return;
+  }
+
+  const missingColumns: string[] = [];
+  for (const columnName of TAXONOMY_SNAPSHOT_REQUIRED_COLUMNS) {
+    if (!hasColumn(client, 'filing_taxonomy_snapshot', columnName)) {
+      missingColumns.push(columnName);
+    }
+  }
+
+  if (missingColumns.length > 0) {
+    throw new Error(
+      `[db] CRITICAL: Database schema is incompatible. ` +
+        `filing_taxonomy_snapshot is missing columns: ${missingColumns.join(', ')}. ` +
+        `Delete the database file and restart to rebuild schema.`
+    );
+  }
+}
+
 export function getSqliteClient() {
   if (!globalThis.__fiscalSqliteClient) {
     configureCustomSqliteRuntime();
@@ -147,6 +169,7 @@ export function getSqliteClient() {
     client.exec('PRAGMA busy_timeout = 5000;');
     loadSqliteExtensions(client);
     ensureLocalSqliteSchema(client);
+    verifyCriticalSchema(client);
     ensureFinancialIngestionSchemaHealthy(client, {
       mode: resolveFinancialSchemaRepairMode(process.env.FINANCIAL_SCHEMA_REPAIR_MODE)
     });
@@ -176,5 +199,6 @@ export const __dbInternals = {
   hasColumn,
   hasTable,
   isVectorExtensionLoaded,
-  loadSqliteExtensions
+  loadSqliteExtensions,
+  verifyCriticalSchema
 };
diff --git a/lib/server/db/sqlite-schema-compat.ts b/lib/server/db/sqlite-schema-compat.ts
index 22f580d..8bbcb49 100644
--- a/lib/server/db/sqlite-schema-compat.ts
+++ b/lib/server/db/sqlite-schema-compat.ts
@@ -296,7 +296,23 @@ function ensureResearchWorkspaceSchema(client: Database) {
   `);
 }
 
+const TAXONOMY_SNAPSHOT_REQUIRED_COLUMNS = [
+  'parser_engine',
+  'parser_version',
+  'taxonomy_regime',
+  'fiscal_pack',
+  'faithful_rows',
+  'surface_rows',
+  'detail_rows',
+  'kpi_rows',
+  'normalization_summary'
+] as const;
+
 function ensureTaxonomySnapshotCompat(client: Database) {
+  if (!hasTable(client, 'filing_taxonomy_snapshot')) {
+    return;
+  }
+
   ensureColumns(client, 'filing_taxonomy_snapshot', [
     { name: 'parser_engine', sql: "ALTER TABLE `filing_taxonomy_snapshot` ADD `parser_engine` text NOT NULL DEFAULT 'fiscal-xbrl';" },
     { name: 'parser_version', sql: "ALTER TABLE `filing_taxonomy_snapshot` ADD `parser_version` text NOT NULL DEFAULT 'unknown';" },
@@ -309,8 +325,13 @@ function ensureTaxonomySnapshotCompat(client: Database) {
     { name: 'normalization_summary', sql: 'ALTER TABLE `filing_taxonomy_snapshot` ADD `normalization_summary` text;' }
   ]);
 
-  if (!hasTable(client, 'filing_taxonomy_snapshot')) {
-    return;
+  for (const columnName of TAXONOMY_SNAPSHOT_REQUIRED_COLUMNS) {
+    if (!hasColumn(client, 'filing_taxonomy_snapshot', columnName)) {
+      throw new Error(
+        `Schema compat failed: filing_taxonomy_snapshot missing required column '${columnName}'. ` +
+          `Delete the database file and restart to rebuild schema.`
+      );
+    }
   }
 
   client.exec(`
@@ -451,6 +472,10 @@ export function ensureLocalSqliteSchema(client: Database) {
 
   client.exec('CREATE INDEX IF NOT EXISTS `task_user_updated_idx` ON `task_run` (`user_id`, `updated_at`);');
 
+  client.exec(`CREATE UNIQUE INDEX IF NOT EXISTS task_active_resource_uidx 
+ON task_run (user_id, task_type, resource_key) 
+WHERE resource_key IS NOT NULL AND status IN ('queued', 'running');`);
+
   ensureColumns(client, 'watchlist_item', [
     { name: 'category', sql: 'ALTER TABLE `watchlist_item` ADD `category` text;' },
     { name: 'tags', sql: 'ALTER TABLE `watchlist_item` ADD `tags` text;' },
@@ -529,5 +554,8 @@ export const __sqliteSchemaCompatInternals = {
   applyBaseSchemaCompat,
   applySqlFile,
   hasColumn,
-  hasTable
+  hasTable,
+  TAXONOMY_SNAPSHOT_REQUIRED_COLUMNS
 };
+
+export { TAXONOMY_SNAPSHOT_REQUIRED_COLUMNS };