diff --git a/crates/ide-host/tests/plugins.rs b/crates/ide-host/tests/plugins.rs
index 324add15..d303fd52 100644
--- a/crates/ide-host/tests/plugins.rs
+++ b/crates/ide-host/tests/plugins.rs
@@ -609,8 +609,9 @@ fn providers_of_several_plugins_run_concurrently() {
         text: text.into(),
     };
     let at = ide_core::Pos::new(0, 0);
-    // Activation is not what is measured.
-    assert_eq!(host.provide_completion(&doc("fast"), at, None).len(), 2);
+    // Activation is not what is measured: a first call that starts an instance
+    // can run past the edit-path budget, and its answer is dropped.
+    assert!(eventually(|| host.provide_completion(&doc("fast"), at, None).len() == 2));
 
     let started = Instant::now();
     let items = host.provide_completion(&doc("sleep:500"), at, None);
@@ -1676,22 +1677,21 @@ fn official_ai_completion_cancels_superseded_requests() {
     };
     let at = ide_core::Pos::new(1, 4);
     let host = Arc::new(f);
-    // A slow request, superseded 200 ms later by the next keystroke's.
+    // A slow request, superseded by the next keystroke's once the server has it
+    // (starting the instance comes first, and takes longer on a slow runner).
     let first = ide_core::CancellationToken::new();
     let slow = {
         let (host, doc, first) = (host.clone(), doc.clone(), first.clone());
-        std::thread::spawn(move || {
-            let started = Instant::now();
-            let r = host.host.provide_inline_completion(&doc, at, &first);
-            (r, started.elapsed())
-        })
+        std::thread::spawn(move || (host.host.provide_inline_completion(&doc, at, &first), Instant::now()))
     };
-    std::thread::sleep(Duration::from_millis(200));
+    assert!(eventually(|| seen.lock().len() == 1), "the first request reaches the server");
+    let cancelled = Instant::now();
     first.cancel();
     let started = Instant::now();
     let second = host.host.provide_inline_completion(&doc, at, &ide_core::CancellationToken::new());
     let took = started.elapsed();
-    let (old, old_took) = slow.join().unwrap();
+    let (old, old_done) = slow.join().unwrap();
+    let old_took = old_done.saturating_duration_since(cancelled);
     assert!(old.is_none(), "the superseded request yields nothing");
     assert!(old_took < Duration::from_secs(1), "cancelled, not waited out: {old_took:?}");
     assert_eq!(second.map(|(_, s)| s.insert_text).as_deref(), Some("a + b"));
@@ -1869,7 +1869,12 @@ fn official_mybatis_navigates_between_interface_and_xml() {
     assert_eq!((target.path, target.range.start), (xml_path.clone(), ide_core::Pos::new(1, 14)));
 
     let xdoc = doc(&xml_path, "xml", xml);
-    let to_java = f.host.provide_definition(&xdoc, ide_core::Pos::new(1, 16));
+    // Reads the interface from disk: on a slow machine that too can run past the budget.
+    let mut to_java = Vec::new();
+    assert!(eventually(|| {
+        to_java = f.host.provide_definition(&xdoc, ide_core::Pos::new(1, 16));
+        !to_java.is_empty()
+    }));
     assert_eq!(
         to_java.iter().map(|l| (l.path.clone(), l.range.start)).collect::<Vec<_>>(),
         [(java_path.clone(), ide_core::Pos::new(3, 9))]
@@ -2437,7 +2442,12 @@ fn completion_quick_fixes_problems_and_event_kinds_of_api_1() {
     };
     let at = ide_core::Pos::new(0, 0);
 
-    let items = f.host.provide_completion(&doc("rich"), at, None);
+    // The first call starts the instance, which may take longer than the edit-path budget.
+    let mut items = Vec::new();
+    assert!(eventually(|| {
+        items = f.host.provide_completion(&doc("rich"), at, None);
+        !items.is_empty()
+    }));
     let item = &items[0].1;
     assert_eq!(
         (item.insert_text.as_str(), item.snippet, item.filter_text.as_deref()),
diff --git a/src/ui/SourcePreview.test.tsx b/src/ui/SourcePreview.test.tsx
index 46e9a408..15f442f3 100644
--- a/src/ui/SourcePreview.test.tsx
+++ b/src/ui/SourcePreview.test.tsx
@@ -1,5 +1,5 @@
 import { describe, expect, it } from "vitest";
-import { render, screen } from "@testing-library/react";
+import { render, screen, waitFor } from "@testing-library/react";
 import { SourcePreview } from "./SourcePreview";
 
 /** A stable loader reference (a new function reloads, like the real module-level ones). */
@@ -24,6 +24,7 @@ describe("SourcePreview", () => {
     const { container } = render(<SourcePreview path="/p/a.ts" line={0} load={loadOf("// TODO")} />);
     await screen.findByText("// TODO");
     // The scroll pane is a selection scope: drags stay inside, text stays copyable.
-    expect(container.querySelector("[data-selection-scope]")).toBeTruthy();
+    // Set by an effect, which can run after the text is on screen.
+    await waitFor(() => expect(container.querySelector("[data-selection-scope]")).toBeTruthy());
   });
 });