fix(fork): truncate the slim composer placeholder under the pills

.fork/customizations.yaml

@@ -674,11 +674,13 @@
     absolutely positioned overlay outside the editor's scroll box — wraps and
     paints straight through the 48px box, and stably so (the overlay never
     changes the observed editor height, so the latch cannot rescue it). A
-    narrow viewport resolves tall regardless. States the designs do not draw
-    also resolve tall: an approval request, a pending user-input question, and
-    the plan follow-up banner all own the box's internals and carry their own
-    action rows. Attachments deliberately do not force tall — attachment cards
-    render as a full-width band above the inline row.
+    narrow viewport resolves tall regardless. On desktop slim the default
+    empty-state hint is a shorter string that still names @, $, and /; tall
+    keeps the long form. States the designs do not draw also resolve tall: an
+    approval request, a pending user-input question, and the plan follow-up
+    banner all own the box's internals and carry their own action rows.
+    Attachments deliberately do not force tall — attachment cards render as a
+    full-width band above the inline row.
     The control row renders in every density, including collapsed; only its
     left half is conditional. The run controls are gated on a pending approval
     — they moved out of the box, which upstream unmounted wholesale during

.fork/notes/FORK-CUSTOMIZATION-DECISIONS.md

@@ -103,6 +103,11 @@ Related deep-dives that predate this file and stay where they are:
   beats them regardless of specificity.
 - Attachments forcing the tall shell was considered and declined; attachment cards render as a
   full-width band above the inline row instead.
+- Absolutely-positioned content in the prompt column is invisible to the wrap latch by
+  construction: it never changes the observed editor height. Phone widths already force tall for
+  that reason; on desktop slim the 64-character default hint wraps under the inline pills. Truncating
+  it would eat `$use skills` / `/ commands`, which have no other discovery surface — so slim uses a
+  shorter hint that still names `@`, `$`, and `/`, and tall keeps the long form.
 - A general weakness worth remembering for future guards: the composer-shell guards assert on the
   text of the stylesheet rather than on what it matches, so a selector that stops matching (for
   example, upstream adding a second child inside the frame) keeps every guard green. Selecting

apps/web/src/__fork_guards__/forkComposerShell.test.ts

@@ -303,6 +303,30 @@ describe("fork guard: fork-composer-shell", () => {
     ).toBe("tall");
   });
 
+  it("shortens the empty-state hint in the slim shell instead of truncating it", () => {
+    // The absolute placeholder is invisible to the wrap latch (empty prompt ⇒
+    // latch false; placeholder only exists when empty). Truncating the 64-char
+    // default hint would eat `$use skills` / `/ commands`, which have no other
+    // discovery surface — so slim uses a shorter string that still names all
+    // three affordances, and tall keeps the long one.
+    expect(chatComposer).toMatch(
+      /isComposerSlim\s*\?\s*"Ask anything, @tag, \$skills, \/ commands"/u,
+    );
+    expect(chatComposer).toContain(
+      "Ask anything, @tag files/folders, $use skills, or / for commands",
+    );
+    // Truncation was considered and declined: no ellipsis rule on the
+    // placeholder sibling, so a sync that reintroduces one is a regression.
+    const rules = cssRules(theme);
+    const placeholderTruncate = rules.find(
+      (rule) =>
+        rule.selector.includes('[data-testid="composer-editor"]') &&
+        rule.selector.includes("~") &&
+        (rule.body.includes("text-overflow") || rule.body.includes("ellipsis")),
+    );
+    expect(placeholderTruncate, "slim placeholder must not truncate").toBeUndefined();
+  });
+
   it("keeps the branch controls reachable while collapsed, and gates modes on approval", () => {
     // Two upstream behaviours the control row has to preserve. Upstream showed
     // BranchToolbar while collapsed (gated on showComposerContextStrip alone),

apps/web/src/components/chat/ChatComposer.tsx

@@ -2769,7 +2769,13 @@ export const ChatComposer = memo(function ChatComposer(props: ChatComposerProps)
                               ? "Enable a provider in Settings to send a message"
                               : phase === "disconnected"
                                 ? "Ask for follow-up changes or attach images"
-                                : "Ask anything, @tag files/folders, $use skills, or / for commands"
+                                : /* fork:begin fork-composer-shell — see .fork/customizations.yaml#fork-composer-shell */
+                                  // Absolute placeholder is invisible to the wrap latch. Slim shortens
+                                  // the hint so @/$/ stay discoverable instead of truncating them away.
+                                  isComposerSlim
+                                  ? "Ask anything, @tag, $skills, / commands"
+                                  : /* fork:end fork-composer-shell */
+                                    "Ask anything, @tag files/folders, $use skills, or / for commands"
                   }
                   disabled={isConnecting || isComposerApprovalState || projectSelectionRequired}
                 />