diff --git a/extensions/diagnostics-otel/src/service.test.ts b/extensions/diagnostics-otel/src/service.test.ts
index fb4a3527aa1..04541527e9a 100644
--- a/extensions/diagnostics-otel/src/service.test.ts
+++ b/extensions/diagnostics-otel/src/service.test.ts
@@ -2175,11 +2175,13 @@ describe("diagnostics-otel service", () => {
 
   test("bounds plugin-emitted log attributes and omits source paths", async () => {
     const service = createDiagnosticsOtelService();
-    const ctx = createOtelContext(OTEL_TEST_ENDPOINT, { logs: true });
+    const ctx = createOtelContext(OTEL_TEST_ENDPOINT, { logs: true, captureContent: true });
     await service.start(ctx);
 
+    const boundaryMessage = `${"x".repeat(4095)}🚀tail`;
+    const boundaryAttribute = `${"y".repeat(4095)}🚀tail`;
     const attributes = Object.create(null) as Record<string, string>;
-    attributes.good = "y".repeat(6000);
+    attributes.good = boundaryAttribute;
     attributes["bad key"] = "drop-me";
     attributes[PROTO_KEY] = "pollute";
     attributes["constructor"] = "pollute";
@@ -2189,7 +2191,7 @@ describe("diagnostics-otel service", () => {
     emitDiagnosticEvent({
       type: "log.record",
       level: "INFO",
-      message: "x".repeat(6000),
+      message: boundaryMessage,
       attributes,
       code: {
         filepath: "/Users/alice/openclaw/src/private.ts",
@@ -2204,11 +2206,10 @@ describe("diagnostics-otel service", () => {
       attributes: Record<string, unknown>;
       body: string;
     };
-    expect(emitCall.body.length).toBeLessThanOrEqual(4200);
-    expect(String(emitCall.attributes["openclaw.good"])).toMatch(/^y+/);
+    expect(emitCall.body).toBe(`${"x".repeat(4095)}...(truncated)`);
+    expect(emitCall.attributes["openclaw.good"]).toBe(`${"y".repeat(4095)}...(truncated)`);
     expect(emitCall.attributes["code.lineno"]).toBe(42);
     expect(emitCall.attributes["code.function"]).toBe("handler");
-    expect(String(emitCall.attributes["openclaw.good"]).length).toBeLessThanOrEqual(4200);
     expect(Object.hasOwn(emitCall.attributes, `openclaw.${PROTO_KEY}`)).toBe(false);
     expect(Object.hasOwn(emitCall.attributes, "openclaw.constructor")).toBe(false);
     expect(Object.hasOwn(emitCall.attributes, "openclaw.prototype")).toBe(false);
diff --git a/extensions/diagnostics-otel/src/service.ts b/extensions/diagnostics-otel/src/service.ts
index 34ba60a0890..e12def6baf9 100644
--- a/extensions/diagnostics-otel/src/service.ts
+++ b/extensions/diagnostics-otel/src/service.ts
@@ -40,6 +40,7 @@ import { waitForDiagnosticEventsDrained } from "openclaw/plugin-sdk/diagnostic-r
 import { createNodeProxyAgent } from "openclaw/plugin-sdk/fetch-runtime";
 import { registerUnhandledRejectionHandler } from "openclaw/plugin-sdk/runtime-env";
 import { isRecord } from "openclaw/plugin-sdk/string-coerce-runtime";
+import { truncateUtf16Safe } from "openclaw/plugin-sdk/text-utility-runtime";
 import type {
   DiagnosticEventMetadata,
   DiagnosticEventPayload,
@@ -682,7 +683,7 @@ function addUpstreamRequestIdSpanEvent(
 }
 
 function clampOtelLogText(value: string, maxChars: number): string {
-  return value.length > maxChars ? `${value.slice(0, maxChars)}...(truncated)` : value;
+  return value.length > maxChars ? `${truncateUtf16Safe(value, maxChars)}...(truncated)` : value;
 }
 
 function normalizeOtelLogString(value: string, maxChars: number): string {
diff --git a/extensions/parallel/src/parallel-search-normalize.ts b/extensions/parallel/src/parallel-search-normalize.ts
index 502ccb49d4e..92de1f868e8 100644
--- a/extensions/parallel/src/parallel-search-normalize.ts
+++ b/extensions/parallel/src/parallel-search-normalize.ts
@@ -8,6 +8,7 @@ import {
   wrapWebContent,
 } from "openclaw/plugin-sdk/provider-web-search";
 import { normalizeOptionalString } from "openclaw/plugin-sdk/string-coerce-runtime";
+import { truncateUtf16Safe } from "openclaw/plugin-sdk/text-utility-runtime";
 
 // Internal-only bounds (the model-facing tool schema declares its own copies).
 const PARALLEL_MAX_SEARCH_COUNT = 40;
@@ -58,7 +59,7 @@ export function normalizeParallelObjective(value: string | undefined): string |
   }
   return trimmed.length <= PARALLEL_MAX_OBJECTIVE_CHARS
     ? trimmed
-    : trimmed.slice(0, PARALLEL_MAX_OBJECTIVE_CHARS);
+    : truncateUtf16Safe(trimmed, PARALLEL_MAX_OBJECTIVE_CHARS);
 }
 
 export function normalizeParallelClientModel(value: string | undefined): string | undefined {
@@ -68,7 +69,7 @@ export function normalizeParallelClientModel(value: string | undefined): string
   }
   return trimmed.length <= PARALLEL_CLIENT_MODEL_MAX_LENGTH
     ? trimmed
-    : trimmed.slice(0, PARALLEL_CLIENT_MODEL_MAX_LENGTH);
+    : truncateUtf16Safe(trimmed, PARALLEL_CLIENT_MODEL_MAX_LENGTH);
 }
 
 // Parallel's API caps each entry at 200 chars and accepts up to 5 queries. We
@@ -90,7 +91,7 @@ export function normalizeParallelSearchQueries(value: unknown): string[] {
     const capped =
       trimmed.length <= PARALLEL_MAX_SEARCH_QUERY_CHARS
         ? trimmed
-        : trimmed.slice(0, PARALLEL_MAX_SEARCH_QUERY_CHARS);
+        : truncateUtf16Safe(trimmed, PARALLEL_MAX_SEARCH_QUERY_CHARS);
     if (seen.has(capped)) {
       continue;
     }
diff --git a/extensions/parallel/src/parallel-web-search-provider.test.ts b/extensions/parallel/src/parallel-web-search-provider.test.ts
index 3f19400e102..233495b5ab2 100644
--- a/extensions/parallel/src/parallel-web-search-provider.test.ts
+++ b/extensions/parallel/src/parallel-web-search-provider.test.ts
@@ -254,6 +254,7 @@ describe("parallel web search provider", () => {
     expect(testing.normalizeParallelObjective(undefined)).toBeUndefined();
     expect(testing.normalizeParallelObjective("")).toBeUndefined();
     expect((testing.normalizeParallelObjective("x".repeat(6000)) ?? "").length).toBe(5000);
+    expect(testing.normalizeParallelObjective(`${"x".repeat(4999)}🚀tail`)).toBe("x".repeat(4999));
   });
 
   it("normalizes search_queries: trim, drop blanks, dedupe, cap length, cap count", () => {
@@ -270,6 +271,9 @@ describe("parallel web search provider", () => {
     expect(testing.normalizeParallelSearchQueries(undefined)).toEqual([]);
     expect(testing.normalizeParallelSearchQueries("openclaw github")).toEqual([]);
     expect(testing.normalizeParallelSearchQueries(["x".repeat(250)])).toEqual(["x".repeat(200)]);
+    expect(testing.normalizeParallelSearchQueries([`${"x".repeat(199)}🚀tail`])).toEqual([
+      "x".repeat(199),
+    ]);
     const six = ["a", "b", "c", "d", "e", "f"];
     expect(testing.normalizeParallelSearchQueries(six)).toEqual(["a", "b", "c", "d", "e"]);
   });
@@ -289,6 +293,7 @@ describe("parallel web search provider", () => {
     expect(testing.normalizeParallelClientModel("  gpt-5.5  ")).toBe("gpt-5.5");
     expect(testing.normalizeParallelClientModel(undefined)).toBeUndefined();
     expect((testing.normalizeParallelClientModel("a".repeat(200)) ?? "").length).toBe(100);
+    expect(testing.normalizeParallelClientModel(`${"m".repeat(99)}🚀tail`)).toBe("m".repeat(99));
   });
 
   it("normalizes the Parallel /v1/search response shape", () => {
diff --git a/extensions/workboard/src/store.test.ts b/extensions/workboard/src/store.test.ts
index ced45e9e983..c0c21809277 100644
--- a/extensions/workboard/src/store.test.ts
+++ b/extensions/workboard/src/store.test.ts
@@ -1938,6 +1938,24 @@ describe("WorkboardStore", () => {
     await expect(store.buildWorkerContext(card.id)).resolves.toContain("Failure screenshot");
   });
 
+  it("keeps worker-context text bounds UTF-16 safe", async () => {
+    const store = new WorkboardStore(createMemoryStore());
+    const card = await store.create({
+      title: "Bound context",
+      metadata: {
+        comments: [
+          {
+            id: "comment-1",
+            body: `${"x".repeat(398)}🚀tail`,
+            createdAt: 10,
+          },
+        ],
+      },
+    });
+
+    await expect(store.buildWorkerContext(card.id)).resolves.toContain(`- ${"x".repeat(398)}…`);
+  });
+
   it("scopes idempotent creates and stats by board", async () => {
     const store = new WorkboardStore(createMemoryStore());
     const ops = await store.create({
diff --git a/extensions/workboard/src/store.ts b/extensions/workboard/src/store.ts
index f4e75de9cba..328f7f0b172 100644
--- a/extensions/workboard/src/store.ts
+++ b/extensions/workboard/src/store.ts
@@ -5,6 +5,7 @@ import {
   MAX_DATE_TIMESTAMP_MS,
   resolveExpiresAtMsFromDurationMs,
 } from "openclaw/plugin-sdk/number-runtime";
+import { truncateUtf16Safe } from "openclaw/plugin-sdk/text-utility-runtime";
 import type {
   PersistedWorkboardAttachment,
   PersistedWorkboardBoard,
@@ -2039,7 +2040,7 @@ function capText(value: string | undefined, max: number): string | undefined {
   if (!value) {
     return undefined;
   }
-  return value.length <= max ? value : `${value.slice(0, Math.max(0, max - 1))}…`;
+  return value.length <= max ? value : `${truncateUtf16Safe(value, Math.max(0, max - 1))}…`;
 }
 
 function cardBoardId(card: WorkboardCard): string {
diff --git a/src/agents/agent-hooks/compaction-safeguard.test.ts b/src/agents/agent-hooks/compaction-safeguard.test.ts
index 4329f8513b4..356a0430814 100644
--- a/src/agents/agent-hooks/compaction-safeguard.test.ts
+++ b/src/agents/agent-hooks/compaction-safeguard.test.ts
@@ -392,6 +392,21 @@ describe("compaction-safeguard tool failures", () => {
     expect(section).toContain("exec (exitCode=2): failed");
   });
 
+  it("keeps bounded tool-failure text UTF-16 safe", () => {
+    const failures = collectToolFailures([
+      {
+        role: "toolResult",
+        toolCallId: "call-boundary",
+        toolName: "exec",
+        isError: true,
+        content: [{ type: "text", text: `${"x".repeat(236)}🚀tail` }],
+        timestamp: Date.now(),
+      },
+    ]);
+
+    expect(failures[0]?.summary).toBe(`${"x".repeat(236)}...`);
+  });
+
   it("caps the number of failures and adds overflow line", () => {
     const messages: AgentMessage[] = Array.from({ length: 9 }, (_, idx) => ({
       role: "toolResult",
@@ -454,6 +469,18 @@ describe("compaction-safeguard summary budgets", () => {
     expect(capped.endsWith(SUMMARY_TRUNCATED_MARKER)).toBe(true);
   });
 
+  it("keeps compaction summary prefixes UTF-16 safe", () => {
+    const prefixBudget = MAX_COMPACTION_SUMMARY_CHARS - SUMMARY_TRUNCATED_MARKER.length;
+    const oversized = `${"x".repeat(prefixBudget - 1)}🚀${"z".repeat(
+      SUMMARY_TRUNCATED_MARKER.length + 10,
+    )}`;
+
+    expect(capCompactionSummary(oversized)).toBe(
+      `${"x".repeat(prefixBudget - 1)}${SUMMARY_TRUNCATED_MARKER}`,
+    );
+    expect(capCompactionSummary(`${"x".repeat(9)}🚀tail`, 10)).toBe("x".repeat(9));
+  });
+
   it("preserves workspace critical rules suffix when capping", () => {
     const suffix =
       "\n\n<workspace-critical-rules>\n## Session Startup\nRead AGENTS.md\n</workspace-critical-rules>";
@@ -522,6 +549,10 @@ describe("compaction-safeguard summary budgets", () => {
     expect(capped).toContain("<read-files>");
     expect(capped).toContain("## Session Startup");
   });
+
+  it("keeps an oversized preserved suffix UTF-16 safe at its leading edge", () => {
+    expect(capCompactionSummaryPreservingSuffix("body", "A🚀tail", 5)).toBe("tail");
+  });
 });
 
 describe("computeAdaptiveChunkRatio", () => {
@@ -906,6 +937,18 @@ describe("compaction-safeguard recent-turn preservation", () => {
     expect(section).toContain("[non-text content: image]");
   });
 
+  it("keeps bounded preserved-turn text UTF-16 safe", () => {
+    const section = formatPreservedTurnsSection([
+      {
+        role: "user",
+        content: `${"x".repeat(599)}🚀tail`,
+        timestamp: 1,
+      },
+    ]);
+
+    expect(section).toContain(`- User: ${"x".repeat(599)}...`);
+  });
+
   it("does not add non-text placeholders for text-only content blocks", () => {
     const section = formatPreservedTurnsSection([
       {
@@ -2692,6 +2735,14 @@ describe("readWorkspaceContextForSummary", () => {
     expect(result).not.toContain("Ignore me");
   });
 
+  it("keeps bounded workspace rules UTF-16 safe", async () => {
+    const heading = "## Session Startup\n";
+    const safePrefix = `${heading}${"x".repeat(1_999 - heading.length)}`;
+    const result = await withWorkspaceSummary(`${safePrefix}🚀tail\n`, ["Session Startup"]);
+
+    expect(result).toContain(`${safePrefix}\n...[truncated]...`);
+  });
+
   it("reads workspace context from the configured workspace instead of process cwd", async () => {
     const processRoot = fs.mkdtempSync(path.join(os.tmpdir(), "openclaw-compaction-cwd-"));
     const workspaceRoot = fs.mkdtempSync(path.join(os.tmpdir(), "openclaw-compaction-workspace-"));
diff --git a/src/agents/agent-hooks/compaction-safeguard.ts b/src/agents/agent-hooks/compaction-safeguard.ts
index 9dbbd7e84fd..7e2cfc2344f 100644
--- a/src/agents/agent-hooks/compaction-safeguard.ts
+++ b/src/agents/agent-hooks/compaction-safeguard.ts
@@ -1,10 +1,12 @@
 /** Extension that safeguards compaction with structured summaries and quality repair. */
+
 import fs from "node:fs";
 import path from "node:path";
+import { sliceUtf16Safe, truncateUtf16Safe } from "@openclaw/normalization-core/utf16-slice";
 import { extractSections } from "../../auto-reply/reply/post-compaction-context.js";
+import { isAbortError } from "../../infra/abort-signal.js";
 import { openRootFile } from "../../infra/boundary-file-read.js";
 import { formatErrorMessage } from "../../infra/errors.js";
-import { isAbortError } from "../../infra/abort-signal.js";
 import { createSubsystemLogger } from "../../logging/subsystem.js";
 import {
   getCompactionProvider,
@@ -404,7 +406,7 @@ function truncateFailureText(text: string, maxChars: number): string {
   if (text.length <= maxChars) {
     return text;
   }
-  return `${text.slice(0, Math.max(0, maxChars - 3))}...`;
+  return `${truncateUtf16Safe(text, Math.max(0, maxChars - 3))}...`;
 }
 
 function formatToolFailureMeta(details: unknown): string | undefined {
@@ -568,9 +570,9 @@ function capCompactionSummary(summary: string, maxChars = MAX_COMPACTION_SUMMARY
   const budget = Math.max(0, maxChars - marker.length);
   if (budget <= 0) {
     // Marker cannot fit; keep body prefix instead of a partial marker fragment.
-    return summary.slice(0, maxChars);
+    return truncateUtf16Safe(summary, maxChars);
   }
-  return `${summary.slice(0, budget)}${marker}`;
+  return `${truncateUtf16Safe(summary, budget)}${marker}`;
 }
 
 function capCompactionSummaryPreservingSuffix(
@@ -586,7 +588,7 @@ function capCompactionSummaryPreservingSuffix(
   }
   if (suffix.length >= maxChars) {
     // Preserve tail (workspace rules, diagnostics) over head (preserved turns).
-    return suffix.slice(-maxChars);
+    return sliceUtf16Safe(suffix, -maxChars);
   }
   const bodyBudget = Math.max(0, maxChars - suffix.length);
   const cappedBody = capCompactionSummary(summaryBody, bodyBudget);
@@ -790,7 +792,7 @@ function formatContextMessages(messages: AgentMessage[]): string[] {
       }
       const trimmed =
         rendered.length > MAX_RECENT_TURN_TEXT_CHARS
-          ? `${rendered.slice(0, MAX_RECENT_TURN_TEXT_CHARS)}...`
+          ? `${truncateUtf16Safe(rendered, MAX_RECENT_TURN_TEXT_CHARS)}...`
           : rendered;
       return `- ${roleLabel}: ${trimmed}`;
     })
@@ -884,7 +886,7 @@ async function readWorkspaceContextForSummary(
     const combined = sections.join("\n\n");
     const safeContent =
       combined.length > MAX_SUMMARY_CONTEXT_CHARS
-        ? combined.slice(0, MAX_SUMMARY_CONTEXT_CHARS) + "\n...[truncated]..."
+        ? `${truncateUtf16Safe(combined, MAX_SUMMARY_CONTEXT_CHARS)}\n...[truncated]...`
         : combined;
 
     return `\n\n<workspace-critical-rules>\n${safeContent}\n</workspace-critical-rules>`;
diff --git a/src/infra/system-presence.test.ts b/src/infra/system-presence.test.ts
index 50824bdbe80..9350ad4b6c5 100644
--- a/src/infra/system-presence.test.ts
+++ b/src/infra/system-presence.test.ts
@@ -114,6 +114,13 @@ describe("system-presence", () => {
     expect(entry?.text).toBe("Node: relay-host · mode operator");
   });
 
+  it("keeps fallback text keys UTF-16 safe", () => {
+    const keyPrefix = `presence-${randomUUID()}`.padEnd(63, "x");
+    const update = updateSystemPresence({ text: `${keyPrefix}🚀tail` });
+
+    expect(update.key).toBe(keyPrefix);
+  });
+
   it("prunes stale non-self entries after TTL", () => {
     vi.useFakeTimers();
     vi.setSystemTime(Date.now());
diff --git a/src/infra/system-presence.ts b/src/infra/system-presence.ts
index 39dea854f3f..25c904134e6 100644
--- a/src/infra/system-presence.ts
+++ b/src/infra/system-presence.ts
@@ -7,6 +7,7 @@ import {
   normalizeOptionalLowercaseString,
   normalizeOptionalString,
 } from "@openclaw/normalization-core/string-coerce";
+import { truncateUtf16Safe } from "@openclaw/normalization-core/utf16-slice";
 import { resolveRuntimeServiceVersion } from "../version.js";
 import { pickBestEffortPrimaryLanIPv4 } from "./network-discovery-display.js";
 
@@ -201,7 +202,7 @@ export function updateSystemPresence(payload: SystemPresencePayload): SystemPres
     normalizePresenceKey(parsed.instanceId) ||
     normalizePresenceKey(parsed.host) ||
     parsed.ip ||
-    parsed.text.slice(0, 64) ||
+    truncateUtf16Safe(parsed.text, 64) ||
     normalizeLowercaseStringOrEmpty(os.hostname());
   const hadExisting = entries.has(key);
   const existing = entries.get(key) ?? ({} as SystemPresence);
diff --git a/ui/src/lib/chat/commands.browser-import.test.ts b/ui/src/lib/chat/commands.browser-import.test.ts
index 00387c15356..c008410f00d 100644
--- a/ui/src/lib/chat/commands.browser-import.test.ts
+++ b/ui/src/lib/chat/commands.browser-import.test.ts
@@ -47,6 +47,7 @@ describe("slash command browser import", () => {
     );
 
     expect(importDeclarations(commands)).toEqual([
+      'import { truncateUtf16Safe } from "@openclaw/normalization-core/utf16-slice";',
       'import type { CommandEntry } from "../../../../packages/gateway-protocol/src/index.js";',
       'import { buildBuiltinChatCommands } from "../../../../src/auto-reply/commands-registry.shared.js";',
       'import { normalizeLowercaseStringOrEmpty } from "../string-coerce.ts";',
diff --git a/ui/src/lib/chat/commands.test.ts b/ui/src/lib/chat/commands.test.ts
index fc3ace24d63..07c76f25c14 100644
--- a/ui/src/lib/chat/commands.test.ts
+++ b/ui/src/lib/chat/commands.test.ts
@@ -234,7 +234,8 @@ describe("parseSlashCommand", () => {
 
   it("caps remote command payload size and long metadata before it reaches UI state", () => {
     const longName = "x".repeat(260);
-    const longDescription = "d".repeat(2_500);
+    const longDescription = `${"d".repeat(1_999)}🚀tail`;
+    const boundaryArgName = `${"n".repeat(199)}🚀tail`;
     const oversizedCommand = {
       name: "plugin-0",
       textAliases: Array.from({ length: 25 }, (_, aliasIndex) => `/plugin-0-${aliasIndex}`),
@@ -243,7 +244,7 @@ describe("parseSlashCommand", () => {
       scope: "both" as const,
       acceptsArgs: true,
       args: Array.from({ length: 25 }, (_, argIndex) => ({
-        name: `${longName}-${argIndex}`,
+        name: argIndex === 0 ? boundaryArgName : `${longName}-${argIndex}`,
         description: longDescription,
         type: "string" as const,
         choices: Array.from({ length: 55 }, (_Local, choiceIndex) => ({
@@ -268,8 +269,9 @@ describe("parseSlashCommand", () => {
     expect(remoteCommands).toHaveLength(500);
     const first = remoteCommands[0];
     expect(first.aliases).toHaveLength(19);
-    expect(first.description.length).toBeLessThanOrEqual(2_000);
+    expect(first.description).toBe("d".repeat(1_999));
     expect(first.args?.split(" ")).toHaveLength(20);
+    expect(first.args?.split(" ")[0]).toBe("[" + "n".repeat(199) + "]");
     expect(first.argOptions).toHaveLength(50);
   });
 
diff --git a/ui/src/lib/chat/commands.ts b/ui/src/lib/chat/commands.ts
index a221bd36017..613e5851321 100644
--- a/ui/src/lib/chat/commands.ts
+++ b/ui/src/lib/chat/commands.ts
@@ -1,4 +1,6 @@
 // Control UI chat domain owns pure slash command rules.
+
+import { truncateUtf16Safe } from "@openclaw/normalization-core/utf16-slice";
 import type { CommandEntry } from "../../../../packages/gateway-protocol/src/index.js";
 import { buildBuiltinChatCommands } from "../../../../src/auto-reply/commands-registry.shared.js";
 import { normalizeLowercaseStringOrEmpty } from "../string-coerce.ts";
@@ -253,7 +255,7 @@ function normalizeSlashIdentifier(raw: string): string | null {
 
 function clampText(value: unknown, maxLength: number): string {
   const text = typeof value === "string" ? value : "";
-  return text.length > maxLength ? text.slice(0, maxLength) : text;
+  return text.length > maxLength ? truncateUtf16Safe(text, maxLength) : text;
 }
 
 function asRecord(value: unknown): Record<string, unknown> | null {
diff --git a/ui/src/pages/workboard/view.test.ts b/ui/src/pages/workboard/view.test.ts
index a5e9af41a12..a464d193cf1 100644
--- a/ui/src/pages/workboard/view.test.ts
+++ b/ui/src/pages/workboard/view.test.ts
@@ -562,6 +562,55 @@ describe("renderWorkboard", () => {
     expect(container.textContent).toContain("Needs proof.");
   });
 
+  it("keeps bounded diagnostic badges UTF-16 safe", () => {
+    const host = {};
+    const state = getWorkboardState(host);
+    state.loaded = true;
+    state.cards = [
+      {
+        id: "card-boundary",
+        title: "Boundary badge",
+        status: "todo",
+        priority: "normal",
+        labels: [],
+        position: 1000,
+        createdAt: 1,
+        updatedAt: 1,
+        metadata: {
+          diagnostics: [
+            {
+              kind: "protocol_violation",
+              severity: "warning",
+              title: `${"x".repeat(62)}🚀tail`,
+              detail: "Boundary detail.",
+              firstSeenAt: 1,
+              lastSeenAt: 1,
+              count: 1,
+            },
+          ],
+        },
+      },
+    ];
+    const container = document.createElement("div");
+
+    render(
+      renderWorkboard({
+        host,
+        client: null,
+        connected: true,
+        pluginEnabled: true,
+        agentsList: null,
+        sessions: [],
+        onOpenSession: () => undefined,
+      }),
+      container,
+    );
+
+    expect(container.querySelector(".workboard-card__badge--warning")?.textContent?.trim()).toBe(
+      `${"x".repeat(62)}…`,
+    );
+  });
+
   it("renders sub-minute heartbeat ages with the duration count interpolation", () => {
     vi.useFakeTimers();
     vi.setSystemTime(new Date("2026-06-13T12:00:00Z"));
diff --git a/ui/src/pages/workboard/view.ts b/ui/src/pages/workboard/view.ts
index 830bd2e8620..b98ea61cfed 100644
--- a/ui/src/pages/workboard/view.ts
+++ b/ui/src/pages/workboard/view.ts
@@ -1,4 +1,6 @@
 // Control UI view renders workboard screen content.
+
+import { truncateUtf16Safe } from "@openclaw/normalization-core/utf16-slice";
 import { html, nothing, type TemplateResult } from "lit";
 import { ref } from "lit/directives/ref.js";
 import type { GatewayBrowserClient } from "../../api/gateway.ts";
@@ -206,7 +208,9 @@ function formatAge(value: number | undefined): string {
 
 function truncateBadgeText(value: string, maxLength = 64): string {
   const trimmed = value.trim();
-  return trimmed.length <= maxLength ? trimmed : `${trimmed.slice(0, maxLength - 1)}…`;
+  return trimmed.length <= maxLength
+    ? trimmed
+    : `${truncateUtf16Safe(trimmed, Math.max(0, maxLength - 1))}…`;
 }
 
 function canMutate(props: WorkboardProps): boolean {