fix(signal): truncate verbose inbound preview on code-point boundaries

solodmd · claude · solodmd · commit 442322f449e8 · 2026-06-30T10:30:15.000+08:00
Signal verbose inbound message previews truncate with body.slice(0, 200),
which can split a UTF-16 surrogate pair when an emoji straddles position
200, producing a lone high surrogate in the debug log.

Use truncateUtf16Safe from openclaw/plugin-sdk/text-utility-runtime so the
preview always lands on a valid code-point boundary.

Tests: 5 new tests covering the straddling-emoji boundary, emoji-before-
boundary, plain ASCII truncation, position-0 edge case, and short-body
pass-through.

Co-Authored-By: Claude &lt;noreply@anthropic.com&gt;
diff --git a/extensions/signal/src/monitor/event-handler.truncation.test.ts b/extensions/signal/src/monitor/event-handler.truncation.test.ts
@@ -0,0 +1,52 @@
+import { truncateUtf16Safe } from "openclaw/plugin-sdk/text-utility-runtime";
+// Signal tests cover event handler.truncation plugin behavior.
+import { describe, expect, it } from "vitest";
+
+describe("signal inbound preview truncation", () => {
+  it("drops an emoji whole when it straddles the 200-char preview boundary", () => {
+    // Emoji 😀 (U+1F600) occupies UTF-16 indices 199-200.
+    // A raw .slice(0, 200) would keep the high surrogate at index 199 and
+    // drop the low surrogate at index 200, leaving a dangling U+D83D.
+    const body = `${"a".repeat(199)}\u{1F600}${"b".repeat(50)}`;
+    expect(body.length).toBeGreaterThanOrEqual(251);
+
+    const preview = truncateUtf16Safe(body, 200).replace(/\n/g, "\\n");
+
+    // No lone surrogate halves in the output
+    expect(/[\u{D800}-\u{DFFF}]/u.test(preview)).toBe(false);
+
+    // The safe truncation drops both surrogates, yielding 199 ASCII chars
+    expect(preview.length).toBe(199);
+    expect(preview).toBe("a".repeat(199));
+  });
+
+  it("preserves emoji when it fits within the 200-char limit", () => {
+    const body = `${"a".repeat(50)}\u{1F600}${"b".repeat(50)}`;
+    const preview = truncateUtf16Safe(body, 200).replace(/\n/g, "\\n");
+
+    expect(/[\u{D800}-\u{DFFF}]/u.test(preview)).toBe(false);
+    expect(preview).toBe(body);
+  });
+
+  it("truncates long plain ASCII text without modification", () => {
+    const body = "x".repeat(500);
+    const preview = truncateUtf16Safe(body, 200).replace(/\n/g, "\\n");
+
+    expect(preview.length).toBe(200);
+    expect(preview).toBe("x".repeat(200));
+  });
+
+  it("handles boundary at position 0", () => {
+    const body = "\u{1F600}" + "a".repeat(50);
+    const preview = truncateUtf16Safe(body, 1).replace(/\n/g, "\\n");
+    // The emoji takes 2 code units, so truncating at 1 drops it
+    expect(preview.length).toBe(0);
+    expect(/[\u{D800}-\u{DFFF}]/u.test(preview)).toBe(false);
+  });
+
+  it("handles body already shorter than limit", () => {
+    const body = "hello";
+    const preview = truncateUtf16Safe(body, 200).replace(/\n/g, "\\n");
+    expect(preview).toBe("hello");
+  });
+});
diff --git a/extensions/signal/src/monitor/event-handler.ts b/extensions/signal/src/monitor/event-handler.ts
@@ -38,7 +38,7 @@ import { resolvePinnedMainDmOwnerFromAllowlist } from "openclaw/plugin-sdk/secur
 import { readSessionUpdatedAt, resolveStorePath } from "openclaw/plugin-sdk/session-store-runtime";
 import { normalizeOptionalString } from "openclaw/plugin-sdk/string-coerce-runtime";
 import { enqueueSystemEvent } from "openclaw/plugin-sdk/system-event-runtime";
-import { normalizeE164 } from "openclaw/plugin-sdk/text-utility-runtime";
+import { normalizeE164, truncateUtf16Safe } from "openclaw/plugin-sdk/text-utility-runtime";
 import {
   maybeResolveSignalApprovalReaction,
   resolveSignalApprovalConversationKey,
@@ -263,7 +263,7 @@ export function createSignalEventHandler(deps: SignalEventHandlerDeps) {
     });
 
     if (shouldLogVerbose()) {
-      const preview = body.slice(0, 200).replace(/\\n/g, "\\\\n");
+      const preview = truncateUtf16Safe(body, 200).replace(/\\n/g, "\\\\n");
       logVerbose(`signal inbound: from=${ctxPayload.From} len=${body.length} preview="${preview}"`);
     }
 
