diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8932cacc0f..668c6883a4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -28,6 +28,16 @@
 - Added `/transcript` to browse long TUI sessions without depending on terminal
   scrollback, with line, page, and first/last navigation.
 
+### Fixed
+
+- Fixed a renderer crash dialog reporting React error #185 ("Maximum update depth
+  exceeded") coming from the composer's prompt-history inline completion (#4117): the
+  offer engine the 0.1.11 composer fed could flip-flop its announcement state on
+  real-layout measurements until React hit its nested-update limit, which surfaced as
+  the crash dialog. The unstable completion wiring was removed from the composer
+  (#3292), Astryx 0.5.0 no longer ships the engine (#3755), and regression tests now
+  keep that seam closed.
+
 ### Changed
 
 - Made typed `request()` the sole direct Runtime Host operation API; removed the 17 forwarding
diff --git a/packages/ui/src/__tests__/composer-inline-completion-seam.test.tsx b/packages/ui/src/__tests__/composer-inline-completion-seam.test.tsx
new file mode 100644
index 0000000000..499ae75a48
--- /dev/null
+++ b/packages/ui/src/__tests__/composer-inline-completion-seam.test.tsx
@@ -0,0 +1,97 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+/**
+ * Regression contract for the renderer crash reported in apache/maka#4117.
+ *
+ * The 0.1.11 composer fed a prompt-history completion candidate to the Astryx
+ * `ChatComposerInput` inline-offer engine:
+ *
+ *     inlineCompletion={matchCompletion(text) ?? undefined}
+ *
+ * That vendor engine (0.4.0) re-decided the offer after every render through a
+ * dependency-less `useEffect(reconcileOffer)`, and both of its exits wrote the
+ * same announcement state — `withdrawOffer()` unconditionally called
+ * `setInlineCompletionAnnouncement('')` while a standing offer called it with
+ * the offer text. Whether the loop terminated depended on a
+ * `getBoundingClientRect` comparison (`offerFullyVisible`) agreeing between
+ * the pass that inserted the offer span and the pass that re-measured it after
+ * the announcement commit. When real layout disagreed — a draft at the
+ * max-rows scroll cap, the offer's tail wrapping the field's bottom edge
+ * inside the tolerance, zoom or font rounding — the two writes flip-flopped,
+ * each flip scheduled another commit-phase update in the same nested chain,
+ * and React threw error 185 ("Maximum update depth exceeded") at the
+ * fiftieth. The renderer crash dialog in the report is that throw; the
+ * minified stack resolves to `withdrawOffer`'s announcement dispatch called
+ * from `reconcileOffer` inside `ChatComposerInput`, mounted by the composer
+ * form.
+ *
+ * The seam is closed on two sides — the completion wiring was removed from
+ * the composer (#3292), and Astryx 0.5.0 no longer ships the engine (#3755).
+ * The flip-flop itself cannot be pinned by a unit harness: it needs real
+ * Chromium layout to disagree between the two measurement passes, which no
+ * DOM emulator performs. What every reintroduction would have to touch — and
+ * what these tests therefore pin — is the seam itself:
+ *
+ *   1. the composer passes no `inlineCompletion*` prop to `ChatComposerInput`;
+ *   2. the history hook carries no prompt-completion source to feed one.
+ *
+ * A safe reintroduction means a loop-proof offer engine (termination must not
+ * rest on cross-pass layout agreement) plus recorded capacity to detect the
+ * loop; neither exists today.
+ */
+
+import assert from 'node:assert/strict';
+import { readFileSync } from 'node:fs';
+import test from 'node:test';
+import { fileURLToPath } from 'node:url';
+
+function readPackageSource(relativePath: string): string {
+  const url = new URL(`../../src/${relativePath}`, import.meta.url);
+  try {
+    return readFileSync(fileURLToPath(url), 'utf8');
+  } catch (error) {
+    throw new Error(
+      `expected ${relativePath} beside the test source; update the seam contract if it moved`,
+      { cause: error },
+    );
+  }
+}
+
+test('the composer passes no inlineCompletion props to ChatComposerInput', () => {
+  const composerSource = readPackageSource('composer.tsx');
+  assert.doesNotMatch(
+    composerSource,
+    /inlineCompletion/,
+    'composer.tsx feeds ChatComposerInput an inline completion again — that wiring drove the ' +
+      'layout-dependent announcement flip-flop behind the #4117 renderer crash (React error 185). ' +
+      'Reintroducing it needs a loop-proof offer engine and a recorded decision; see the file ' +
+      'header and the removal in #3292.',
+  );
+});
+
+test('the history hook carries no prompt-completion source', () => {
+  const historySource = readPackageSource('use-composer-history.ts');
+  assert.doesNotMatch(
+    historySource,
+    /matchCompletion|matchPromptHistory|prompt-history-match/,
+    'use-composer-history.ts exposes a prompt-history completion again — the only consumer that ' +
+      'matcher ever had was the inline-completion prop behind the #4117 renderer crash.',
+  );
+});