diff --git a/packages/runtime/src/sandbox/body-runner.ts b/packages/runtime/src/sandbox/body-runner.ts
index 82923bd873..c0cf89f483 100644
--- a/packages/runtime/src/sandbox/body-runner.ts
+++ b/packages/runtime/src/sandbox/body-runner.ts
@@ -71,7 +71,11 @@ export function hookBodyRunnerFactory(
             name: hook.name,
             object: typeof (hook as any).object === 'string' ? (hook as any).object : undefined,
           },
-          timeoutMs: (body as any).timeoutMs ?? 250,
+          // When the body declares no timeout, leave opts.timeoutMs unset so the
+          // runner's own configurable hook default applies (QuickJSScriptRunner
+          // defaults to 250ms). Hardcoding the fallback here would make that
+          // constructor option dead for hooks.
+          timeoutMs: (body as any).timeoutMs,
         });
         applyMutationsToInput(engineCtx, result);
       } catch (err: any) {
@@ -123,7 +127,9 @@ export function actionBodyRunnerFactory(
         });
         const result = await runner.run(body, sandboxCtx, {
           origin: { kind: 'action', name: action.name, object: action.object },
-          timeoutMs: (body as any).timeoutMs ?? action.timeoutMs ?? 5000,
+          // As with hooks above: no declared timeout → let the runner's
+          // configurable action default (5000ms) apply.
+          timeoutMs: (body as any).timeoutMs ?? action.timeoutMs,
         });
         return result.value;
       } catch (err: any) {
diff --git a/packages/runtime/src/sandbox/nested-write-real-sqlite.integration.test.ts b/packages/runtime/src/sandbox/nested-write-real-sqlite.integration.test.ts
index adb49c55e6..e31897f27a 100644
--- a/packages/runtime/src/sandbox/nested-write-real-sqlite.integration.test.ts
+++ b/packages/runtime/src/sandbox/nested-write-real-sqlite.integration.test.ts
@@ -86,7 +86,9 @@ describe('#1867 nested cross-object write — REAL SqlDriver (better-sqlite3, on
     engine.registerDriver(driver, true);
     await engine.init();
     for (const o of [EXPENSE_REPORT, EXPENSE_LINE]) engine.registry.registerObject(o as any);
-    engine.setDefaultBodyRunner(hookBodyRunnerFactory(new QuickJSScriptRunner(), { ql: engine, appId: 'expense' }));
+    // Generous hook budget — the subject is the nested-write path on a real
+    // driver, not the 250ms default (see nested-write.integration.test.ts).
+    engine.setDefaultBodyRunner(hookBodyRunnerFactory(new QuickJSScriptRunner({ hookTimeoutMs: 10_000 }), { ql: engine, appId: 'expense' }));
     bindHooksToEngine(engine, [ROLLUP_HOOK as any], { packageId: 'expense' });
     return engine;
   }
diff --git a/packages/runtime/src/sandbox/nested-write.integration.test.ts b/packages/runtime/src/sandbox/nested-write.integration.test.ts
index 53561aa077..57c143aa1d 100644
--- a/packages/runtime/src/sandbox/nested-write.integration.test.ts
+++ b/packages/runtime/src/sandbox/nested-write.integration.test.ts
@@ -90,8 +90,13 @@ describe('#1867 nested cross-object write from a hook (real engine + sandbox)',
     engine.registerDriver(driver, true);
     await engine.init();
     for (const o of [parent, child]) engine.registry.registerObject(o as any);
+    // Generous hook budget: the subject here is nested-write correctness, not
+    // the 250ms default. Each hook invocation compiles a fresh WASM module and
+    // the nested parent hook compiles another inside the child's budget — on a
+    // loaded CI machine that overhead alone blew 250ms ("hook
+    // 'rollup_parent_total' exceeded timeout of 250ms").
     engine.setDefaultBodyRunner(
-      hookBodyRunnerFactory(new QuickJSScriptRunner(), { ql: engine, appId: 'test' }),
+      hookBodyRunnerFactory(new QuickJSScriptRunner({ hookTimeoutMs: 10_000 }), { ql: engine, appId: 'test' }),
     );
   });
 
diff --git a/packages/runtime/src/sandbox/quickjs-runner.test.ts b/packages/runtime/src/sandbox/quickjs-runner.test.ts
index 7e0b25786e..a108fa42c4 100644
--- a/packages/runtime/src/sandbox/quickjs-runner.test.ts
+++ b/packages/runtime/src/sandbox/quickjs-runner.test.ts
@@ -4,7 +4,13 @@ import { describe, it, expect } from 'vitest';
 import { QuickJSScriptRunner, SandboxError } from './quickjs-runner.js';
 import type { ScriptContext, ScriptRunOptions } from './script-runner.js';
 
-const runner = new QuickJSScriptRunner();
+// Generous hook budget: these tests exercise sandbox *behaviour*, not the stock
+// 250ms hook budget. Every invocation compiles a fresh WASM module, and nested
+// hooks compile another one inside the parent's budget — on a loaded CI machine
+// that fixed cost alone can blow 250ms and flake (e.g. "hook 'lvl4' exceeded
+// timeout of 250ms"). Tests that ARE about the default budget use
+// `defaultRunner` below.
+const runner = new QuickJSScriptRunner({ hookTimeoutMs: 10_000 });
 const hookOpts: ScriptRunOptions = { origin: { kind: 'hook', name: 't' } };
 const actionOpts: ScriptRunOptions = { origin: { kind: 'action', name: 't' } };
 
@@ -364,6 +370,10 @@ describe('QuickJSScriptRunner — nested sandbox re-entrancy (#1867)', () => {
 // the 250ms hook default and killed mid-flight.
 // ---------------------------------------------------------------------------
 describe('QuickJSScriptRunner — timeout resolution honors body.timeoutMs (#1867)', () => {
+  // Stock engine defaults (250ms hooks) — these tests assert the default budget
+  // itself, so they must NOT use the generous shared `runner` above.
+  const defaultRunner = new QuickJSScriptRunner();
+
   it('honors a hook body timeoutMs above the 250ms hook default', async () => {
     // Host call settles at ~600ms — comfortably past the old 250ms hook cap but
     // within the body's declared 5000ms budget. Must resolve, not time out.
@@ -375,7 +385,7 @@ describe('QuickJSScriptRunner — timeout resolution honors body.timeoutMs (#186
         },
       }),
     };
-    const r = await runner.runScript(
+    const r = await defaultRunner.runScript(
       {
         language: 'js',
         source: "return await ctx.api.object('x').update({});",
@@ -390,27 +400,26 @@ describe('QuickJSScriptRunner — timeout resolution honors body.timeoutMs (#186
 
   it('still applies the 250ms hook default when the body declares no timeoutMs', async () => {
     const api = { object: () => ({ update: () => new Promise<never>(() => {}) }) };
-    const start = Date.now();
     await expect(
-      runner.runScript(
+      defaultRunner.runScript(
         { language: 'js', source: "return await ctx.api.object('x').update({});", capabilities: ['api.write'] },
         ctx({ api }),
         hookOpts,
       ),
-    ).rejects.toThrow(/timeout/i);
-    // Fired near the 250ms default, not some larger value.
-    expect(Date.now() - start).toBeLessThan(2000);
+      // The error message embeds the effective budget — asserting on it proves
+      // the 250ms default applied without a flaky wall-clock measurement.
+    ).rejects.toThrow(/timeout of 250ms/);
   }, 10000);
 
   it('lets a hook body LOWER its timeout below the default', async () => {
     const api = { object: () => ({ update: () => new Promise<never>(() => {}) }) };
     await expect(
-      runner.runScript(
+      defaultRunner.runScript(
         { language: 'js', source: "return await ctx.api.object('x').update({});", capabilities: ['api.write'], timeoutMs: 50 },
         ctx({ api }),
         hookOpts,
       ),
-    ).rejects.toThrow(/timeout/i);
+    ).rejects.toThrow(/timeout of 50ms/);
   }, 10000);
 });