diff --git a/projects/start-os/container-runtime/src/Adapters/EffectCreator.test.ts b/projects/start-os/container-runtime/src/Adapters/EffectCreator.test.ts
new file mode 100644
index 0000000000..caf2ebd7b6
--- /dev/null
+++ b/projects/start-os/container-runtime/src/Adapters/EffectCreator.test.ts
@@ -0,0 +1,22 @@
+import { effectParams } from './EffectCreator'
+
+describe('effectParams', () => {
+  test('tags the call with the calling procedure', () => {
+    expect(effectParams({ actionId: 'a' }, 'procedure')).toEqual({
+      actionId: 'a',
+      eventId: 'procedure',
+    })
+  })
+
+  test('keeps the event id an action run names', () => {
+    expect(
+      effectParams({ actionId: 'a', eventId: 'form' }, 'procedure'),
+    ).toEqual({ actionId: 'a', eventId: 'form' })
+  })
+
+  test('sends no event id outside a procedure', () => {
+    expect(JSON.stringify(effectParams({ actionId: 'a' }, null))).toBe(
+      '{"actionId":"a"}',
+    )
+  })
+})
diff --git a/projects/start-os/container-runtime/src/Adapters/EffectCreator.ts b/projects/start-os/container-runtime/src/Adapters/EffectCreator.ts
index a1e7e19d57..2bbed4e48b 100644
--- a/projects/start-os/container-runtime/src/Adapters/EffectCreator.ts
+++ b/projects/start-os/container-runtime/src/Adapters/EffectCreator.ts
@@ -46,6 +46,14 @@ export type EffectContext = {
   constRetry?: () => void
 }
 
+/** The effect call's params, tagged with the calling procedure's event id. An `eventId` the effect names itself wins. */
+export function effectParams(
+  params: Record<string, unknown>,
+  eventId: string | null,
+): Record<string, unknown> {
+  return { eventId: eventId ?? undefined, ...params }
+}
+
 const rpcRoundFor =
   (eventId: string | null) =>
   <K extends T.EffectMethod | 'clearCallbacks'>(
@@ -58,7 +66,7 @@ const rpcRoundFor =
         JSON.stringify({
           id,
           method,
-          params: { ...params, eventId: eventId ?? undefined },
+          params: effectParams(params, eventId),
         }) + '\n',
       )
     })