diff --git a/moli-core/tests/scripts.rs b/moli-core/tests/scripts.rs
index ddc1c5812c..dbb5472078 100644
--- a/moli-core/tests/scripts.rs
+++ b/moli-core/tests/scripts.rs
@@ -6728,6 +6728,9 @@ mod document_write_errors;
 #[path = "scripts/child_markup_insertion.rs"]
 mod child_markup_insertion;
 
+#[path = "scripts/child_input_stream_readiness.rs"]
+mod child_input_stream_readiness;
+
 #[path = "scripts/document_close.rs"]
 mod document_close;
 
diff --git a/moli-core/tests/scripts/child_input_stream_readiness.rs b/moli-core/tests/scripts/child_input_stream_readiness.rs
new file mode 100644
index 0000000000..7a8841d2b2
--- /dev/null
+++ b/moli-core/tests/scripts/child_input_stream_readiness.rs
@@ -0,0 +1,126 @@
+use super::*;
+
+async fn child_stream_readiness_probe(operation: &str) -> Result<serde_json::Value> {
+    let server = FixtureServer::spawn().await?;
+    let browser = Browser::new(AppConfig::default())?;
+    let mut page = browser.fetch(&server.url("/static")).await?;
+    let expression = r#"(async () => {
+      const frame = await new Promise(resolve => {
+        const frame = document.createElement('iframe');
+        frame.onload = () => resolve(frame);
+        frame.src = '/static';
+        document.body.append(frame);
+      });
+      frame.onload = null;
+      const doc = frame.contentDocument;
+      const win = frame.contentWindow;
+      const oldBody = doc.body;
+      let oldEvents = 0;
+      doc.onreadystatechange = () => ++oldEvents;
+      doc.addEventListener('readystatechange', () => ++oldEvents);
+      win.addEventListener('readystatechange', () => ++oldEvents, true);
+      oldBody.addEventListener('old-listener-probe', () => ++oldEvents);
+      const operation = OPERATION;
+      let opened = null;
+      if (operation === 'open' || operation === 'reopen') {
+        const same = doc.open() === doc;
+        opened = {same, readyState: doc.readyState, children: doc.childNodes.length};
+      }
+      const markup = '<p id="written">new stream</p><script>' +
+        'window.streamScriptReadyState = document.readyState;' + '<' + '/script>';
+      if (operation === 'writeln') doc.writeln(markup);
+      else doc.write(markup);
+      let reopened = null;
+      if (operation === 'reopen') {
+        doc.addEventListener('readystatechange', () => ++oldEvents);
+        const same = doc.open() === doc;
+        reopened = {same, readyState: doc.readyState, children: doc.childNodes.length};
+        doc.write(markup);
+      }
+      oldBody.dispatchEvent(new Event('old-listener-probe'));
+      const during = {readyState: doc.readyState,
+        scriptReadyState: win.streamScriptReadyState,
+        sameDocument: doc === frame.contentDocument,
+        text: doc.getElementById('written').textContent,
+        handlerCleared: doc.onreadystatechange === null,
+        trailingNewline: doc.body.lastChild.nodeType === Node.TEXT_NODE &&
+          doc.body.lastChild.data === '\n'};
+      const states = [];
+      doc.addEventListener('readystatechange', () => states.push(doc.readyState));
+      const finished = await new Promise(resolve => {
+        win.addEventListener('load', () => resolve({readyState: doc.readyState,
+          states, oldEvents, parentReadyState: document.readyState}), {once: true});
+        doc.close();
+      });
+      frame.remove();
+      return JSON.stringify({opened, reopened, during, finished});
+    })()"#
+        .replace("OPERATION", &serde_json::to_string(operation)?);
+    let result = page
+        .evaluate_runtime_expression_with_await_async(&expression, true)
+        .await?;
+    server.shutdown().await;
+    serde_json::from_str(
+        result["value"]
+            .as_str()
+            .expect("child stream readiness probe"),
+    )
+    .map_err(Into::into)
+}
+
+fn assert_child_stream_readiness(result: &serde_json::Value, newline: bool) {
+    assert_eq!(
+        result["during"],
+        serde_json::json!({
+            "readyState": "loading", "scriptReadyState": "loading", "sameDocument": true,
+            "text": "new stream", "handlerCleared": true, "trailingNewline": newline
+        }),
+        "{result}"
+    );
+    assert_eq!(
+        result["finished"],
+        serde_json::json!({
+            "readyState": "complete", "states": ["interactive", "complete"],
+            "oldEvents": 0, "parentReadyState": "complete"
+        }),
+        "{result}"
+    );
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn child_document_open_resets_readiness_after_erasing_listeners() -> Result<()> {
+    let result = child_stream_readiness_probe("open").await?;
+    assert_eq!(
+        result["opened"],
+        serde_json::json!({"same": true, "readyState": "loading", "children": 0}),
+        "{result}"
+    );
+    assert_child_stream_readiness(&result, false);
+    Ok(())
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn child_document_write_implicit_open_resets_readiness() -> Result<()> {
+    let result = child_stream_readiness_probe("write").await?;
+    assert_child_stream_readiness(&result, false);
+    Ok(())
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn child_document_writeln_implicit_open_resets_readiness() -> Result<()> {
+    let result = child_stream_readiness_probe("writeln").await?;
+    assert_child_stream_readiness(&result, true);
+    Ok(())
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn child_document_open_replaces_an_already_loading_stream() -> Result<()> {
+    let result = child_stream_readiness_probe("reopen").await?;
+    assert_eq!(
+        result["reopened"],
+        serde_json::json!({"same": true, "readyState": "loading", "children": 0}),
+        "{result}"
+    );
+    assert_child_stream_readiness(&result, false);
+    Ok(())
+}