@@ -175,6 +175,15 @@ describe("orchestration V2 wire projection", () => {
       summary: '"'.repeat(159) + "…",
       truncated: true,
     });
+
+    const boundary = projectTurnItemForWire({
+      ...base,
+      input: { text: "a".repeat(149) + "😀" + "b".repeat(17_000) },
+    });
+    expect(boundary.type === "dynamic_tool" ? boundary.input : null).toEqual({
+      summary: '{"text":"' + "a".repeat(149) + "…",
+      truncated: true,
+    });
   });
 
   it("truncates detail at a UTF-8 boundary without changing the source", () => {
 
@@ -97,8 +97,10 @@ function summarizeDynamicValue(value: unknown): unknown {
     pendingSpace = false;
     if (firstLine.length > 160) break;
   }
+  const last = firstLine.charCodeAt(158);
+  const end = last >= 0xd800 && last <= 0xdbff ? 158 : 159;
   return {
-    summary: firstLine.length <= 160 ? firstLine : `${firstLine.slice(0, 159).trimEnd()}…`,
+    summary: firstLine.length <= 160 ? firstLine : `${firstLine.slice(0, end).trimEnd()}…`,
     truncated: true,
   };
 }
Original file line number	Diff line number	Diff line change
`@@ -97,8 +97,10 @@ function summarizeDynamicValue(value: unknown): unknown {`
`97`	`97`	`pendingSpace = false;`
`98`	`98`	`if (firstLine.length > 160) break;`
`99`	`99`	`}`
	`100`	`+ const last = firstLine.charCodeAt(158);`
	`101`	`+ const end = last >= 0xd800 && last <= 0xdbff ? 158 : 159;`
`100`	`102`	`return {`
`101`		- summary: firstLine.length <= 160 ? firstLine : `${firstLine.slice(0, 159).trimEnd()}…`,
	`103`	+ summary: firstLine.length <= 160 ? firstLine : `${firstLine.slice(0, end).trimEnd()}…`,
`102`	`104`	`truncated: true,`
`103`	`105`	`};`
`104`	`106`	`}`