fix(agents): report surrogate-safe omitted count

steipete · steipete · commit 686f644a7c38 · 2026-07-09T07:47:43.000+01:00
diff --git a/src/agents/embedded-agent-runner/tool-result-context-guard.test.ts b/src/agents/embedded-agent-runner/tool-result-context-guard.test.ts
@@ -179,23 +179,6 @@ function recordMockArg(
   return arg as Record<string, unknown>;
 }
 
-function hasLoneSurrogate(s: string): boolean {
-  for (let i = 0; i < s.length; i += 1) {
-    const c = s.charCodeAt(i);
-    if (c >= 0xd800 && c <= 0xdbff) {
-      if (i + 1 >= s.length || s.charCodeAt(i + 1) < 0xdc00 || s.charCodeAt(i + 1) > 0xdfff) {
-        return true;
-      }
-    }
-    if (c >= 0xdc00 && c <= 0xdfff) {
-      if (i === 0 || s.charCodeAt(i - 1) < 0xd800 || s.charCodeAt(i - 1) > 0xdbff) {
-        return true;
-      }
-    }
-  }
-  return false;
-}
-
 describe("formatContextLimitTruncationNotice", () => {
   it("formats truncation wording with a count", () => {
     expect(formatContextLimitTruncationNotice(123)).toBe(
@@ -358,9 +341,9 @@ describe("installToolResultContextGuard", () => {
       1_000,
     )) as AgentMessage[];
 
-    const truncated = getToolResultText(transformed[0]);
-    expectOpenClawTruncation(truncated);
-    expect(hasLoneSurrogate(truncated)).toBe(false);
+    expect(getToolResultText(transformed[0])).toBe(
+      "a".repeat(439) + formatContextLimitTruncationNotice(1_002),
+    );
     expect(getToolResultText(contextForNextCall[0])).toBe(text);
   });
 
diff --git a/src/agents/embedded-agent-runner/tool-result-context-guard.ts b/src/agents/embedded-agent-runner/tool-result-context-guard.ts
@@ -165,8 +165,8 @@ function truncateTextToBudget(text: string, maxChars: number): string {
     cutPoint = newline;
   }
 
-  const omittedChars = text.length - cutPoint;
-  return truncateUtf16Safe(text, cutPoint) + formatContextLimitTruncationNotice(omittedChars);
+  const prefix = truncateUtf16Safe(text, cutPoint);
+  return prefix + formatContextLimitTruncationNotice(text.length - prefix.length);
 }
 
 function replaceToolResultText(msg: AgentMessage, text: string): AgentMessage {

Original file line number	Diff line number	Diff line change
`@@ -165,8 +165,8 @@ function truncateTextToBudget(text: string, maxChars: number): string {`
`165`	`165`	`cutPoint = newline;`
`166`	`166`	`}`
`167`	`167`
`168`		`- const omittedChars = text.length - cutPoint;`
`169`		`- return truncateUtf16Safe(text, cutPoint) + formatContextLimitTruncationNotice(omittedChars);`
	`168`	`+ const prefix = truncateUtf16Safe(text, cutPoint);`
	`169`	`+ return prefix + formatContextLimitTruncationNotice(text.length - prefix.length);`
`170`	`170`	`}`
`171`	`171`
`172`	`172`	`function replaceToolResultText(msg: AgentMessage, text: string): AgentMessage {`