diff --git a/src/utils/parseEnvConfigs.ts b/src/utils/parseEnvConfigs.ts
index e8863f0..e26daf2 100644
--- a/src/utils/parseEnvConfigs.ts
+++ b/src/utils/parseEnvConfigs.ts
@@ -33,10 +33,14 @@ export function parseSystemConfigEnvValue(key: keyof typeof SYSTEM_CONFIG_ENV_MA
     case 'delay_after':
       return Number(raw);
 
-    // An empty value, or one of the words an operator is likely to reach for,
-    // means no limit. Without this the only way to express "uncapped" through the
-    // environment would be to unset the variable, which a deployment template
-    // cannot easily do.
+    // One of the words an operator is likely to reach for means no limit. Without
+    // this the only way to express "uncapped" through the environment would be to
+    // unset the variable, which a deployment template cannot easily do.
+    //
+    // A truly empty value never gets here: bootstrapSystemConfig skips empty env
+    // values, so they count as unset (an existing cap is kept, otherwise the
+    // default applies). The empty check below only catches a whitespace-only
+    // value, which is empty once trimmed.
     case 'max_concurrent_sessions': {
       const value = raw.trim().toLowerCase();
 
diff --git a/tests/unit/config/bootstrapMaxConcurrentSessions.spec.ts b/tests/unit/config/bootstrapMaxConcurrentSessions.spec.ts
new file mode 100644
index 0000000..2b67560
--- /dev/null
+++ b/tests/unit/config/bootstrapMaxConcurrentSessions.spec.ts
@@ -0,0 +1,78 @@
+import { vi } from 'vitest';
+
+vi.mock('../../../src/models/systemConfig', () => ({
+  SystemConfig: {
+    findByPk: vi.fn(),
+    create: vi.fn(),
+  },
+}));
+
+vi.mock('../../../src/config/systemConfig.envMap', () => ({
+  SYSTEM_CONFIG_ENV_MAP: {
+    max_concurrent_sessions: 'MAX_CONCURRENT_SESSIONS',
+  },
+}));
+
+vi.mock('../../../src/schemas/systemConfig.schema', () => ({
+  SystemConfigSchema: {
+    safeParse: vi.fn(),
+  },
+}));
+
+import { beforeEach, describe, expect, it } from 'vitest';
+
+// The real parser and defaults are used here. Bootstrap skips an empty env value
+// before parsing, so MAX_CONCURRENT_SESSIONS='' behaves as unset rather than as
+// "no limit". Only a whitespace-only value reaches the parser's empty check.
+describe('bootstrapSystemConfig with MAX_CONCURRENT_SESSIONS', () => {
+  beforeEach(() => {
+    vi.resetModules();
+    vi.clearAllMocks();
+    delete process.env.MAX_CONCURRENT_SESSIONS;
+  });
+
+  async function load() {
+    const { SystemConfig } = await import('../../../src/models/systemConfig');
+    const { SystemConfigSchema } = await import('../../../src/schemas/systemConfig.schema');
+    (SystemConfigSchema.safeParse as any).mockReturnValue({ success: true, data: {} });
+    const { bootstrapSystemConfig } = await import('../../../src/config/bootstrapSystemConfig');
+    return { SystemConfig, SystemConfigSchema, bootstrapSystemConfig };
+  }
+
+  it('keeps an existing cap when the value is empty', async () => {
+    const { SystemConfig, SystemConfigSchema, bootstrapSystemConfig } = await load();
+    const row = { value: 3, updatedBy: null, update: vi.fn(), destroy: vi.fn() };
+    (SystemConfig.findByPk as any).mockResolvedValue(row);
+    process.env.MAX_CONCURRENT_SESSIONS = '';
+
+    await bootstrapSystemConfig();
+
+    expect(row.update).not.toHaveBeenCalled();
+    expect(row.destroy).not.toHaveBeenCalled();
+    expect(SystemConfigSchema.safeParse).toHaveBeenCalledWith({ max_concurrent_sessions: 3 });
+  });
+
+  it('uses the default when the value is empty and no row exists', async () => {
+    const { SystemConfig, SystemConfigSchema, bootstrapSystemConfig } = await load();
+    (SystemConfig.findByPk as any).mockResolvedValue(null);
+    process.env.MAX_CONCURRENT_SESSIONS = '';
+
+    await bootstrapSystemConfig();
+
+    expect(SystemConfig.create).not.toHaveBeenCalled();
+    expect(SystemConfigSchema.safeParse).toHaveBeenCalledWith({ max_concurrent_sessions: null });
+  });
+
+  it('clears an existing cap when the value is whitespace only', async () => {
+    const { SystemConfig, SystemConfigSchema, bootstrapSystemConfig } = await load();
+    const row = { value: 3, updatedBy: null, update: vi.fn(), destroy: vi.fn() };
+    (SystemConfig.findByPk as any).mockResolvedValue(row);
+    process.env.MAX_CONCURRENT_SESSIONS = '   ';
+
+    await bootstrapSystemConfig();
+
+    expect(row.destroy).toHaveBeenCalled();
+    expect(row.update).not.toHaveBeenCalled();
+    expect(SystemConfigSchema.safeParse).toHaveBeenCalledWith({ max_concurrent_sessions: null });
+  });
+});