diff --git a/CHANGELOG.md b/CHANGELOG.md
index f3e1dea4..ba9b0448 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,11 @@
 
 ## Unreleased
 
+- `@polymorfa/ui` Inbox: the conversation list and the thread sit side by side
+  from 560 px of Inbox width, down from 700 px, and Back appears only when
+  they cannot. Back showed beside the list before because its rule read the
+  thread's width. Back now has a visible border. Source-only until a nightly
+  publishes.
 - All six server SDKs expose optional automatic-pause `reason`/`code` and
   optional recipient-skip `messageIndex`/`followUpId` from accepted API source
   `9bb1e2ed`. Future reason/code strings and raw envelope fields are retained;
diff --git a/contracts/doc-snippets.json b/contracts/doc-snippets.json
index fde7b6b0..7d24d1f5 100644
--- a/contracts/doc-snippets.json
+++ b/contracts/doc-snippets.json
@@ -1,7 +1,7 @@
 {
   "schemaVersion": 1,
-  "sourceCommit": "f33cd3b9a949f8db495405d0733ca0bcdb4bd3bc",
-  "sourceFilesSha256": "7af428a30b1becaf20b3e9ce407cc0742d49353fac60a43aba71e568642a12c3",
+  "sourceCommit": "6bc7fe43a34dc2d7a37ea60a71429549dcb2ae5a",
+  "sourceFilesSha256": "5d8cbb667d2947c518fd084ee7e640301a85675097231968669919d95f601eda",
   "apiVersion": "2026-09-22",
   "apiSourceCommit": "171a9683ff45d11a4b5d3917dc428ad2722b0d99",
   "specs": {
diff --git a/packages/ui/src/styles.ts b/packages/ui/src/styles.ts
index 09924e7c..2d6398fa 100644
--- a/packages/ui/src/styles.ts
+++ b/packages/ui/src/styles.ts
@@ -1242,10 +1242,10 @@ video.pmfa-chip-player { max-height: 120px; border-radius: 6px; }
 
 /* Inbox */
 .pmfa-inbox {
-  container-type: inline-size;
+  container: pmfa-inbox / inline-size;
   position: relative;
   display: grid;
-  grid-template-columns: minmax(280px, 380px) minmax(0, 1fr);
+  grid-template-columns: minmax(240px, 380px) minmax(0, 1fr);
   grid-template-rows: minmax(0, 1fr);
   height: 100%;
   min-height: 420px;
@@ -1254,7 +1254,7 @@ video.pmfa-chip-player { max-height: 120px; border-radius: 6px; }
   border-radius: var(--pmfa-r-l);
   background: var(--pmfa-c-panel);
 }
-.pmfa-inbox[data-contact-open] { grid-template-columns: minmax(280px, 360px) minmax(0, 1fr) minmax(260px, 320px); }
+.pmfa-inbox[data-contact-open] { grid-template-columns: minmax(240px, 360px) minmax(0, 1fr) minmax(260px, 320px); }
 .pmfa-inbox-list {
   display: flex;
   flex-direction: column;
@@ -1525,8 +1525,10 @@ video.pmfa-chip-player { max-height: 120px; border-radius: 6px; }
 .pmfa-contact-fields > div { display: flex; flex-direction: column; gap: 2px; padding: 12px 0; border-top: 1px solid var(--pmfa-c-border); }
 .pmfa-contact-fields dt { color: var(--pmfa-c-muted); font-size: 0.75em; font-weight: 500; }
 .pmfa-contact-fields dd { margin: 0; font-size: 0.9375em; overflow-wrap: anywhere; }
-/* Container queries match the inbox's children; the inbox is the container. */
-@container (max-width: 1023px) {
+/* Named, because the thread is a container too: an unnamed query would read
+   the thread's width for the controls inside it. The list and the thread sit
+   side by side from 560px, where the thread keeps 320px. */
+@container pmfa-inbox (max-width: 1023px) {
   .pmfa-inbox > .pmfa-thread { grid-column: 2 / -1; }
   .pmfa-inbox .pmfa-contact {
     position: absolute;
@@ -1538,11 +1540,12 @@ video.pmfa-chip-player { max-height: 120px; border-radius: 6px; }
     animation: pmfa-slide 180ms ease-out;
   }
 }
-@container (max-width: 699px) {
+@container pmfa-inbox (max-width: 559px) {
   .pmfa-inbox > .pmfa-inbox-list, .pmfa-inbox > .pmfa-thread { grid-column: 1 / -1; grid-row: 1; border-inline-end: 0; }
   .pmfa-inbox[data-view="thread"] .pmfa-inbox-list { display: none; }
   .pmfa-inbox[data-view="list"] .pmfa-thread { display: none; }
-  .pmfa-inbox .pmfa-back { display: inline-flex; }
+  .pmfa-inbox .pmfa-back { display: inline-flex; border-color: var(--pmfa-c-border); background: var(--pmfa-c-bg); color: var(--pmfa-c-fg); }
+  .pmfa-inbox .pmfa-back:hover:not(:disabled) { background: var(--pmfa-c-surface); }
   .pmfa-inbox .pmfa-contact { width: 100%; border-inline-start: 0; }
   .pmfa-thread-head { padding-inline-start: 4px; }
 }
diff --git a/packages/ui/test/appearance.test.ts b/packages/ui/test/appearance.test.ts
index cb74a84a..ad45620c 100644
--- a/packages/ui/test/appearance.test.ts
+++ b/packages/ui/test/appearance.test.ts
@@ -106,6 +106,20 @@ describe("appearance", () => {
     );
   });
 
+  it("lays out the inbox by its own width, not the thread's", () => {
+    // The thread is a container too, so an unnamed query showed Back beside the list.
+    expect(COMPONENT_STYLES).toContain("container: pmfa-inbox / inline-size;");
+    expect(COMPONENT_STYLES).toContain(
+      "@container pmfa-inbox (max-width: 559px)",
+    );
+    expect(COMPONENT_STYLES).toContain(
+      "@container pmfa-inbox (max-width: 1023px)",
+    );
+    expect(COMPONENT_STYLES).not.toMatch(
+      /@container \(max-width: (699|1023)px\)/,
+    );
+  });
+
   it("lays out chat messages with day separators and direction groups", () => {
     const day = new Date(2026, 0, 5, 9).getTime();
     const entries = layoutMessages([
diff --git a/scripts/doc-snippets/recipes.mjs b/scripts/doc-snippets/recipes.mjs
index 51ff7aa5..b094fec3 100644
--- a/scripts/doc-snippets/recipes.mjs
+++ b/scripts/doc-snippets/recipes.mjs
@@ -1,7 +1,7 @@
 // Requests come from the pinned OpenAPI and existing native wire fixtures.
 // Calls are handwritten in the language modules. Never derive arguments from
 // contracts/coverage.json's display-only method names.
-export const sourceCommit = "f33cd3b9a949f8db495405d0733ca0bcdb4bd3bc";
+export const sourceCommit = "6bc7fe43a34dc2d7a37ea60a71429549dcb2ae5a";
 export const apiVersion = "2026-09-22";
 export const languages = [
   "typescript",