diff --git a/docs/gateway/opentelemetry.md b/docs/gateway/opentelemetry.md
index a952e1566b12..6266fd8a59e9 100644
--- a/docs/gateway/opentelemetry.md
+++ b/docs/gateway/opentelemetry.md
@@ -238,6 +238,15 @@ OpenClaw's CLI boundary through
 - `paired-node-cli` - one-shot Claude Code execution delegated to a paired
   node.
 
+Claude CLI diagnostics are instantiated only while the process diagnostic
+dispatcher is enabled and an internal or trusted event listener is attached.
+With no observability plugin or other listener active, Claude CLI turns skip
+the synthetic trace hierarchy, content buffers, and diagnostic stream-byte
+accounting. When content capture is enabled, prompt and system-prompt fields
+are capped at 128 KiB each; assistant output is capped at 128 KiB across at
+most 200 envelopes, with 16 KiB and one item reserved for a final visible
+fallback response. A marker records truncation when the limit is reached.
+
 OpenClaw gives Claude CLI turns the same ownership hierarchy used by other
 agent runtimes: `openclaw.harness.run` (`openclaw.harness.id = claude-cli`)
 contains `openclaw.run`, which contains the Claude `openclaw.model.call`
diff --git a/src/agents/cli-runner.before-agent-reply-cron.test.ts b/src/agents/cli-runner.before-agent-reply-cron.test.ts
index db3cbd093260..6c4e36f1a3ab 100644
--- a/src/agents/cli-runner.before-agent-reply-cron.test.ts
+++ b/src/agents/cli-runner.before-agent-reply-cron.test.ts
@@ -200,6 +200,21 @@ describe("runCliAgent before_agent_reply seam", () => {
     expect(result?.diagnosticTrace).toEqual(harnessStarted?.trace);
   });
 
+  it("bypasses Claude CLI diagnostics when no event listener is active", async () => {
+    executePreparedCliRunMock.mockResolvedValue({ text: "real Claude reply" });
+
+    const result = await runCliAgent({
+      ...baseRunParams,
+      provider: "claude-cli",
+      modelProvider: "anthropic",
+      model: "claude-opus-4-7",
+      runId: "claude-no-diagnostics-listener",
+    });
+
+    expect(result.diagnosticTrace).toBeUndefined();
+    expect(executePreparedCliRunMock).toHaveBeenCalledOnce();
+  });
+
   it("preserves the send phase when execution fails before successful cleanup", async () => {
     executePreparedCliRunMock.mockRejectedValueOnce(new Error("CLI process failed"));
 
diff --git a/src/agents/cli-runner.ts b/src/agents/cli-runner.ts
index 67dfc9979f77..40c8cfd61013 100644
--- a/src/agents/cli-runner.ts
+++ b/src/agents/cli-runner.ts
@@ -10,6 +10,8 @@ import {
   captureAgentRunLifecycleGeneration,
   withAgentRunLifecycleGeneration,
 } from "../infra/agent-events.js";
+import { hasInternalDiagnosticEventListeners } from "../infra/diagnostic-event-listener-presence.js";
+import { areDiagnosticsEnabledForProcess } from "../infra/diagnostic-events.js";
 import { formatErrorMessage } from "../infra/errors.js";
 import { createSubsystemLogger } from "../logging/subsystem.js";
 import {
@@ -468,8 +470,12 @@ export function runCliAgent(paramsInput: RunCliAgentParams): Promise<EmbeddedAge
     ...paramsInput,
     lifecycleGeneration,
   };
+  // Observability services register before turns and keep subscriptions process-stable.
+  // Snapshot listener presence here so disabled installs pay no synthetic trace cost.
   return withAgentRunLifecycleGeneration(lifecycleGeneration, () =>
-    isClaudeCliProvider(params.provider)
+    isClaudeCliProvider(params.provider) &&
+    areDiagnosticsEnabledForProcess() &&
+    hasInternalDiagnosticEventListeners()
       ? runClaudeCliAgentTurnWithDiagnostics(params, (diagnosticLifecycle) =>
           runCliAgentInternal(params, diagnosticLifecycle),
         )
diff --git a/src/agents/cli-runner/execute.ts b/src/agents/cli-runner/execute.ts
index a6d0daf1245e..3d87efc17058 100644
--- a/src/agents/cli-runner/execute.ts
+++ b/src/agents/cli-runner/execute.ts
@@ -1644,8 +1644,9 @@ export async function executePreparedCliRun(
           const stderrHash = crypto.createHash("sha256");
           let stderrParseExceeded = false;
           const consumeStdout = (chunk: string) => {
-            claudeModelCallDiagnostics?.observeCliOutput(chunk, "stdout");
-            stdoutBytes += Buffer.byteLength(chunk);
+            const chunkBytes = Buffer.byteLength(chunk);
+            claudeModelCallDiagnostics?.observeCliOutput(chunk, "stdout", chunkBytes);
+            stdoutBytes += chunkBytes;
             stdoutHash.update(chunk);
             stdoutTail = appendCliOutputTail(stdoutTail, chunk);
             if (!stdoutParseExceeded) {
diff --git a/src/agents/cli-runner/model-call-diagnostics.test.ts b/src/agents/cli-runner/model-call-diagnostics.test.ts
new file mode 100644
index 000000000000..6a0ddb65c50c
--- /dev/null
+++ b/src/agents/cli-runner/model-call-diagnostics.test.ts
@@ -0,0 +1,355 @@
+// Verifies Claude CLI model diagnostics stay listener-gated and memory-bounded.
+import { expectDefined } from "@openclaw/normalization-core";
+import { afterEach, describe, expect, it } from "vitest";
+import {
+  onTrustedInternalDiagnosticEvent,
+  resetDiagnosticEventsForTest,
+  waitForDiagnosticEventsDrained,
+  type DiagnosticEventPrivateData,
+} from "../../infra/diagnostic-events.js";
+import type { CliOutput } from "../cli-output.js";
+import { createClaudeCliModelCallDiagnostics } from "./model-call-diagnostics.js";
+import type { PreparedCliRunContext } from "./types.js";
+
+const CONTENT_LIMIT_BYTES = 128 * 1024;
+
+function createContext(): PreparedCliRunContext {
+  return {
+    backendResolved: { id: "claude-cli", modelProvider: "anthropic" },
+    contextWindowInfo: undefined,
+    normalizedModel: "claude-test",
+    params: {
+      config: {
+        diagnostics: {
+          enabled: true,
+          otel: {
+            enabled: true,
+            traces: true,
+            captureContent: {
+              enabled: true,
+              inputMessages: true,
+              outputMessages: true,
+              systemPrompt: true,
+            },
+          },
+        },
+      },
+      runId: "claude-diagnostics-test",
+      sessionId: "session-test",
+    },
+  } as PreparedCliRunContext;
+}
+
+describe("Claude CLI model-call diagnostics", () => {
+  afterEach(() => {
+    resetDiagnosticEventsForTest();
+  });
+
+  it("does not create diagnostics without an active event listener", () => {
+    expect(
+      createClaudeCliModelCallDiagnostics({
+        context: createContext(),
+        prompt: "hello",
+        transport: "stdio",
+      }),
+    ).toBeUndefined();
+  });
+
+  it("bounds large prompt and assistant content during a burst", async () => {
+    let completedPrivateData: DiagnosticEventPrivateData | undefined;
+    const stop = onTrustedInternalDiagnosticEvent((event, _metadata, privateData) => {
+      if (event.type === "model.call.completed") {
+        completedPrivateData = privateData;
+      }
+    });
+    const largeText = "€".repeat(256 * 1024);
+    const diagnostics = expectDefined(
+      createClaudeCliModelCallDiagnostics({
+        context: createContext(),
+        prompt: largeText,
+        systemPrompt: largeText,
+        transport: "stdio",
+      }),
+      "Claude CLI diagnostics",
+    );
+
+    diagnostics.emitStarted();
+    for (let index = 0; index < 250; index += 1) {
+      diagnostics.observeAssistantMessage({
+        content: [{ type: "text", text: `${index}:${largeText}` }],
+      });
+    }
+    diagnostics.emitCompleted({ text: "done" } as CliOutput);
+    await waitForDiagnosticEventsDrained();
+    stop();
+
+    const modelContent = expectDefined(completedPrivateData?.modelContent, "model content");
+    const inputJson = JSON.stringify(modelContent.inputMessages);
+    const outputJson = JSON.stringify(modelContent.outputMessages);
+    expect(Buffer.byteLength(inputJson, "utf8")).toBeLessThanOrEqual(CONTENT_LIMIT_BYTES + 256);
+    expect(Buffer.byteLength(modelContent.systemPrompt ?? "", "utf8")).toBeLessThanOrEqual(
+      CONTENT_LIMIT_BYTES,
+    );
+    expect(Buffer.byteLength(outputJson, "utf8")).toBeLessThanOrEqual(CONTENT_LIMIT_BYTES);
+    expect(outputJson).toContain("...(truncated)");
+  });
+
+  it("bounds serialized escaped content across many envelopes", async () => {
+    let outputMessages: unknown;
+    const stop = onTrustedInternalDiagnosticEvent((event, _metadata, privateData) => {
+      if (event.type === "model.call.completed") {
+        outputMessages = privateData.modelContent?.outputMessages;
+      }
+    });
+    const diagnostics = expectDefined(
+      createClaudeCliModelCallDiagnostics({
+        context: createContext(),
+        prompt: "hello",
+        transport: "stdio",
+      }),
+      "Claude CLI diagnostics",
+    );
+
+    diagnostics.emitStarted();
+    for (let index = 0; index < 199; index += 1) {
+      diagnostics.observeAssistantMessage({ content: `part-${index}:\u0000`.repeat(100) });
+    }
+    diagnostics.emitCompleted({ text: "done" } as CliOutput);
+    await waitForDiagnosticEventsDrained();
+    stop();
+
+    expect(Buffer.byteLength(JSON.stringify(outputMessages), "utf8")).toBeLessThanOrEqual(
+      CONTENT_LIMIT_BYTES,
+    );
+  });
+
+  it("caps assistant envelope count and records truncation", async () => {
+    let outputMessages: unknown;
+    const stop = onTrustedInternalDiagnosticEvent((event, _metadata, privateData) => {
+      if (event.type === "model.call.completed") {
+        outputMessages = privateData.modelContent?.outputMessages;
+      }
+    });
+    const diagnostics = expectDefined(
+      createClaudeCliModelCallDiagnostics({
+        context: createContext(),
+        prompt: "hello",
+        transport: "stdio",
+      }),
+      "Claude CLI diagnostics",
+    );
+
+    diagnostics.emitStarted();
+    for (let index = 0; index < 250; index += 1) {
+      diagnostics.observeAssistantMessage({ content: `message-${index}` });
+    }
+    diagnostics.emitCompleted({ text: "done" } as CliOutput);
+    await waitForDiagnosticEventsDrained();
+    stop();
+
+    expect(outputMessages).toHaveLength(200);
+    expect(JSON.stringify(outputMessages)).toContain("...(truncated)");
+  });
+
+  it("records truncation when the item budget ends inside an envelope", async () => {
+    let outputMessages: unknown;
+    const stop = onTrustedInternalDiagnosticEvent((event, _metadata, privateData) => {
+      if (event.type === "model.call.completed") {
+        outputMessages = privateData.modelContent?.outputMessages;
+      }
+    });
+    const diagnostics = expectDefined(
+      createClaudeCliModelCallDiagnostics({
+        context: createContext(),
+        prompt: "hello",
+        transport: "stdio",
+      }),
+      "Claude CLI diagnostics",
+    );
+
+    diagnostics.emitStarted();
+    for (let index = 0; index < 197; index += 1) {
+      diagnostics.observeAssistantMessage({ content: `message-${index}` });
+    }
+    diagnostics.observeAssistantMessage({
+      content: [
+        { type: "text", text: "captured-a" },
+        { type: "text", text: "captured-b" },
+        { type: "text", text: "dropped-c" },
+      ],
+    });
+    diagnostics.emitCompleted({ text: "done" } as CliOutput);
+    await waitForDiagnosticEventsDrained();
+    stop();
+
+    expect(outputMessages).toHaveLength(199);
+    expect(JSON.stringify(outputMessages)).toContain("captured-b");
+    expect(JSON.stringify(outputMessages)).not.toContain("dropped-c");
+    expect(JSON.stringify(outputMessages)).toContain("...(truncated)");
+  });
+
+  it("keeps fallback response text when prior non-text envelopes fill the limit", async () => {
+    let outputMessages: unknown;
+    const stop = onTrustedInternalDiagnosticEvent((event, _metadata, privateData) => {
+      if (event.type === "model.call.completed") {
+        outputMessages = privateData.modelContent?.outputMessages;
+      }
+    });
+    const diagnostics = expectDefined(
+      createClaudeCliModelCallDiagnostics({
+        context: createContext(),
+        prompt: "hello",
+        transport: "stdio",
+      }),
+      "Claude CLI diagnostics",
+    );
+
+    diagnostics.emitStarted();
+    for (let index = 0; index < 200; index += 1) {
+      diagnostics.observeAssistantMessage({
+        content: [{ type: "thinking", thinking: `reason-${index}` }],
+      });
+    }
+    diagnostics.emitCompleted({ text: "final visible answer" } as CliOutput);
+    await waitForDiagnosticEventsDrained();
+    stop();
+
+    expect(outputMessages).toHaveLength(200);
+    expect(JSON.stringify(outputMessages)).toContain("final visible answer");
+    expect(JSON.stringify(outputMessages)).toContain("...(truncated)");
+  });
+
+  it("keeps fallback response text when non-text content fills the byte budget", async () => {
+    let outputMessages: unknown;
+    const stop = onTrustedInternalDiagnosticEvent((event, _metadata, privateData) => {
+      if (event.type === "model.call.completed") {
+        outputMessages = privateData.modelContent?.outputMessages;
+      }
+    });
+    const diagnostics = expectDefined(
+      createClaudeCliModelCallDiagnostics({
+        context: createContext(),
+        prompt: "hello",
+        transport: "stdio",
+      }),
+      "Claude CLI diagnostics",
+    );
+
+    diagnostics.emitStarted();
+    diagnostics.observeAssistantMessage({
+      content: [{ type: "thinking", thinking: "€".repeat(256 * 1024) }],
+    });
+    diagnostics.emitCompleted({ text: "final visible answer" } as CliOutput);
+    await waitForDiagnosticEventsDrained();
+    stop();
+
+    const outputJson = JSON.stringify(outputMessages);
+    expect(outputJson).toContain("final visible answer");
+    expect(outputJson).toContain("...(truncated)");
+    expect(Buffer.byteLength(outputJson, "utf8")).toBeLessThanOrEqual(CONTENT_LIMIT_BYTES + 512);
+  });
+
+  it("keeps the fallback reserve after empty text content", async () => {
+    let outputMessages: unknown;
+    const stop = onTrustedInternalDiagnosticEvent((event, _metadata, privateData) => {
+      if (event.type === "model.call.completed") {
+        outputMessages = privateData.modelContent?.outputMessages;
+      }
+    });
+    const diagnostics = expectDefined(
+      createClaudeCliModelCallDiagnostics({
+        context: createContext(),
+        prompt: "hello",
+        transport: "stdio",
+      }),
+      "Claude CLI diagnostics",
+    );
+
+    diagnostics.emitStarted();
+    diagnostics.observeAssistantMessage({ content: "" });
+    diagnostics.observeAssistantMessage({
+      content: Array.from({ length: 200 }, (_, index) => ({
+        type: "thinking",
+        thinking: `reason-${index}`,
+      })),
+    });
+    diagnostics.emitCompleted({ text: "final visible answer" } as CliOutput);
+    await waitForDiagnosticEventsDrained();
+    stop();
+
+    const outputJson = JSON.stringify(outputMessages);
+    expect(outputJson).toContain("final visible answer");
+    expect(outputJson).toContain("...(truncated)");
+  });
+
+  it("bounds text probing after the capture budget is exhausted", async () => {
+    let outputMessages: unknown;
+    const stop = onTrustedInternalDiagnosticEvent((event, _metadata, privateData) => {
+      if (event.type === "model.call.completed") {
+        outputMessages = privateData.modelContent?.outputMessages;
+      }
+    });
+    const diagnostics = expectDefined(
+      createClaudeCliModelCallDiagnostics({
+        context: createContext(),
+        prompt: "hello",
+        transport: "stdio",
+      }),
+      "Claude CLI diagnostics",
+    );
+
+    diagnostics.emitStarted();
+    diagnostics.observeAssistantMessage({
+      content: Array.from({ length: 198 }, (_, index) => ({
+        type: "thinking",
+        thinking: `reason-${index}`,
+      })),
+    });
+    diagnostics.observeAssistantMessage({
+      content: [
+        ...Array.from({ length: 10_000 }, () => ({ type: "thinking", thinking: "later" })),
+        { type: "text", text: "outside-probe-window" },
+      ],
+    });
+    diagnostics.emitCompleted({ text: "final visible answer" } as CliOutput);
+    await waitForDiagnosticEventsDrained();
+    stop();
+
+    const outputJson = JSON.stringify(outputMessages);
+    expect(outputJson).toContain("final visible answer");
+    expect(outputJson).not.toContain("outside-probe-window");
+  });
+
+  it("counts the truncation marker within the output item limit", async () => {
+    let outputMessages: unknown;
+    const stop = onTrustedInternalDiagnosticEvent((event, _metadata, privateData) => {
+      if (event.type === "model.call.completed") {
+        outputMessages = privateData.modelContent?.outputMessages;
+      }
+    });
+    const diagnostics = expectDefined(
+      createClaudeCliModelCallDiagnostics({
+        context: createContext(),
+        prompt: "hello",
+        transport: "stdio",
+      }),
+      "Claude CLI diagnostics",
+    );
+
+    diagnostics.emitStarted();
+    diagnostics.observeAssistantMessage({
+      content: Array.from({ length: 201 }, (_, index) => ({
+        type: "text",
+        text: `part-${index}`,
+      })),
+    });
+    diagnostics.emitCompleted({ text: "done" } as CliOutput);
+    await waitForDiagnosticEventsDrained();
+    stop();
+
+    const messages = outputMessages as Array<{ content?: unknown[] }>;
+    const itemCount = messages.reduce((sum, message) => sum + (message.content?.length ?? 0), 0);
+    expect(itemCount).toBe(200);
+    expect(JSON.stringify(messages)).toContain("...(truncated)");
+  });
+});
diff --git a/src/agents/cli-runner/model-call-diagnostics.ts b/src/agents/cli-runner/model-call-diagnostics.ts
index 49f3485c2026..5c668c4156f0 100644
--- a/src/agents/cli-runner/model-call-diagnostics.ts
+++ b/src/agents/cli-runner/model-call-diagnostics.ts
@@ -1,12 +1,15 @@
 /** Trusted turn-level model-call diagnostics for the Claude Code CLI runtime. */
 import crypto from "node:crypto";
 import { isRecord } from "@openclaw/normalization-core/record-coerce";
+import { truncateUtf16Safe } from "@openclaw/normalization-core/utf16-slice";
 import {
   diagnosticErrorCategory,
   diagnosticErrorFailureKind,
   diagnosticErrorMessage,
 } from "../../infra/diagnostic-error-metadata.js";
+import { hasInternalDiagnosticEventListeners } from "../../infra/diagnostic-event-listener-presence.js";
 import {
+  areDiagnosticsEnabledForProcess,
   emitTrustedDiagnosticEventWithPrivateData,
   type DiagnosticEventPrivateData,
   type DiagnosticModelCallContent,
@@ -29,15 +32,114 @@ type ModelCallFailureKind = Extract<
   { type: "model.call.error" }
 >["failureKind"];
 
-function assistantContentBlock(block: unknown): Record<string, unknown> | undefined {
+const MAX_CAPTURED_CONTENT_BYTES = 128 * 1024;
+const FALLBACK_RESPONSE_RESERVE_BYTES = 16 * 1024;
+const MAX_CAPTURED_OUTPUT_MESSAGES = 200;
+const MAX_CAPTURED_OUTPUT_BLOCKS = 200;
+const TRUNCATED_CONTENT_SUFFIX = "...(truncated)";
+// One maximal tool-call block per envelope plus stopReason is the largest
+// structure possible under the shared 200-envelope/item caps.
+const MAX_CAPTURED_OUTPUT_STRUCTURE_BYTES = Buffer.byteLength(
+  JSON.stringify(
+    Array.from({ length: MAX_CAPTURED_OUTPUT_MESSAGES }, () => ({
+      role: "assistant",
+      content: [{ type: "tool_call", name: "", id: "" }],
+      stopReason: "",
+    })),
+  ),
+  "utf8",
+);
+
+type DiagnosticContentBudget = {
+  remainingBytes: number;
+  remainingItems: number;
+  fallbackReserveBytes: number;
+  fallbackReserveItems: number;
+  truncated: boolean;
+};
+
+function serializedStringContentBytes(value: string): number {
+  return Buffer.byteLength(JSON.stringify(value), "utf8") - 2;
+}
+
+const TRUNCATED_CONTENT_SUFFIX_BYTES = serializedStringContentBytes(TRUNCATED_CONTENT_SUFFIX);
+
+function truncateSerializedStringSafe(value: string, maxBytes: number): string {
+  if (maxBytes <= 0) {
+    return "";
+  }
+  if (serializedStringContentBytes(value) <= maxBytes) {
+    return value;
+  }
+  let low = 0;
+  let high = Math.min(value.length, maxBytes);
+  let captured = "";
+  while (low <= high) {
+    const middle = Math.floor((low + high) / 2);
+    const candidate = truncateUtf16Safe(value, middle);
+    if (serializedStringContentBytes(candidate) <= maxBytes) {
+      captured = candidate;
+      low = middle + 1;
+    } else {
+      high = middle - 1;
+    }
+  }
+  return captured;
+}
+
+function releaseFallbackReserve(budget: DiagnosticContentBudget): void {
+  budget.remainingBytes += budget.fallbackReserveBytes;
+  budget.remainingItems += budget.fallbackReserveItems;
+  budget.fallbackReserveBytes = 0;
+  budget.fallbackReserveItems = 0;
+}
+
+function captureTextWithinBudget(
+  value: string,
+  budget: DiagnosticContentBudget,
+): string | undefined {
+  if (budget.remainingBytes <= 0) {
+    budget.truncated = true;
+    return undefined;
+  }
+  const valueBytes = serializedStringContentBytes(value);
+  if (valueBytes <= budget.remainingBytes) {
+    budget.remainingBytes -= valueBytes;
+    return value;
+  }
+  const suffix = truncateSerializedStringSafe(TRUNCATED_CONTENT_SUFFIX, budget.remainingBytes);
+  const prefixBudget = Math.max(0, budget.remainingBytes - serializedStringContentBytes(suffix));
+  const captured = `${truncateSerializedStringSafe(value, prefixBudget)}${suffix}`;
+  budget.remainingBytes -= serializedStringContentBytes(captured);
+  budget.truncated = true;
+  return captured;
+}
+
+function captureBoundedText(value: string): string {
+  const budget = {
+    remainingBytes: MAX_CAPTURED_CONTENT_BYTES,
+    remainingItems: 1,
+    fallbackReserveBytes: 0,
+    fallbackReserveItems: 0,
+    truncated: false,
+  };
+  return captureTextWithinBudget(value, budget) ?? "";
+}
+
+function assistantContentBlock(
+  block: unknown,
+  budget: DiagnosticContentBudget,
+): Record<string, unknown> | undefined {
   if (!isRecord(block)) {
     return undefined;
   }
-  if (block.type === "text" && typeof block.text === "string") {
-    return { type: "text", text: block.text };
+  if (block.type === "text" && typeof block.text === "string" && block.text.length > 0) {
+    const text = captureTextWithinBudget(block.text, budget);
+    return text === undefined ? undefined : { type: "text", text };
   }
   if (block.type === "thinking" && typeof block.thinking === "string") {
-    return { type: "thinking", thinking: block.thinking };
+    const thinking = captureTextWithinBudget(block.thinking, budget);
+    return thinking === undefined ? undefined : { type: "thinking", thinking };
   }
   if (
     (block.type === "tool_use" ||
@@ -45,37 +147,122 @@ function assistantContentBlock(block: unknown): Record<string, unknown> | undefi
       block.type === "mcp_tool_use") &&
     typeof block.name === "string"
   ) {
+    const name = captureTextWithinBudget(block.name, budget);
+    if (name === undefined) {
+      return undefined;
+    }
+    const id = typeof block.id === "string" ? captureTextWithinBudget(block.id, budget) : undefined;
     return {
       type: "tool_call",
-      name: block.name,
-      ...(typeof block.id === "string" ? { id: block.id } : {}),
+      name,
+      ...(id !== undefined ? { id } : {}),
     };
   }
   return undefined;
 }
 
+function isCapturableAssistantContentBlock(block: unknown): boolean {
+  if (!isRecord(block)) {
+    return false;
+  }
+  return (
+    (block.type === "text" && typeof block.text === "string") ||
+    (block.type === "thinking" && typeof block.thinking === "string") ||
+    ((block.type === "tool_use" ||
+      block.type === "server_tool_use" ||
+      block.type === "mcp_tool_use") &&
+      typeof block.name === "string")
+  );
+}
+
+function isTextAssistantContentBlock(block: unknown): boolean {
+  return (
+    isRecord(block) &&
+    block.type === "text" &&
+    typeof block.text === "string" &&
+    block.text.length > 0
+  );
+}
+
+function assistantMessageHasText(message: unknown): boolean {
+  if (!isRecord(message)) {
+    return false;
+  }
+  if (typeof message.content === "string") {
+    return message.content.length > 0;
+  }
+  if (!Array.isArray(message.content)) {
+    return false;
+  }
+  const limit = Math.min(message.content.length, MAX_CAPTURED_OUTPUT_BLOCKS);
+  for (let index = 0; index < limit; index += 1) {
+    if (isTextAssistantContentBlock(message.content[index])) {
+      return true;
+    }
+  }
+  return false;
+}
+
 // Claude's assistant envelopes can contain native tool arguments and opaque
 // thinking signatures. Keep only the visible response blocks OpenClaw can
 // represent accurately; external harness tool spans stay metadata-only.
-function normalizeClaudeAssistantMessage(message: unknown): Record<string, unknown> | undefined {
+function normalizeClaudeAssistantMessage(
+  message: unknown,
+  budget: DiagnosticContentBudget,
+): Record<string, unknown> | undefined {
   if (!isRecord(message)) {
     return undefined;
   }
-  const content =
-    typeof message.content === "string"
-      ? [{ type: "text", text: message.content }]
-      : Array.isArray(message.content)
-        ? message.content
-            .map(assistantContentBlock)
-            .filter((block): block is Record<string, unknown> => Boolean(block))
-        : [];
+  const content: Record<string, unknown>[] = [];
+  if (typeof message.content === "string") {
+    if (message.content.length === 0) {
+      return undefined;
+    }
+    releaseFallbackReserve(budget);
+    const text = captureTextWithinBudget(message.content, budget);
+    if (text !== undefined && budget.remainingItems > 0) {
+      content.push({ type: "text", text });
+      budget.remainingItems -= 1;
+    } else if (text !== undefined) {
+      budget.truncated = true;
+    }
+  } else if (Array.isArray(message.content)) {
+    const sourceBlocks = message.content.slice(0, MAX_CAPTURED_OUTPUT_BLOCKS);
+    if (sourceBlocks.length < message.content.length) {
+      budget.truncated = true;
+    }
+    for (const [index, sourceBlock] of sourceBlocks.entries()) {
+      if (isTextAssistantContentBlock(sourceBlock)) {
+        releaseFallbackReserve(budget);
+      }
+      const block = assistantContentBlock(sourceBlock, budget);
+      if (block) {
+        if (budget.remainingItems > 0) {
+          content.push(block);
+          budget.remainingItems -= 1;
+        } else {
+          budget.truncated = true;
+        }
+      }
+      if (budget.remainingBytes <= 0 || budget.remainingItems <= 0) {
+        if (sourceBlocks.slice(index + 1).some(isCapturableAssistantContentBlock)) {
+          budget.truncated = true;
+        }
+        break;
+      }
+    }
+  }
   if (content.length === 0) {
     return undefined;
   }
+  const stopReason =
+    typeof message.stop_reason === "string"
+      ? captureTextWithinBudget(message.stop_reason, budget)
+      : undefined;
   return {
     role: "assistant",
     content,
-    ...(typeof message.stop_reason === "string" ? { stopReason: message.stop_reason } : {}),
+    ...(stopReason !== undefined ? { stopReason } : {}),
   };
 }
 
@@ -84,11 +271,29 @@ function hasTextContent(messages: readonly Record<string, unknown>[]): boolean {
     (message) =>
       Array.isArray(message.content) &&
       message.content.some(
-        (block) => isRecord(block) && block.type === "text" && typeof block.text === "string",
+        (block) =>
+          isRecord(block) &&
+          block.type === "text" &&
+          typeof block.text === "string" &&
+          block.text.length > 0,
       ),
   );
 }
 
+function appendOutputTruncationMarker(messages: Record<string, unknown>[]): void {
+  const marker = { type: "text", text: TRUNCATED_CONTENT_SUFFIX };
+  if (messages.length < MAX_CAPTURED_OUTPUT_MESSAGES) {
+    messages.push({ role: "assistant", content: [marker] });
+    return;
+  }
+  const lastIndex = messages.length - 1;
+  const lastMessage = messages[lastIndex];
+  messages[lastIndex] = {
+    ...lastMessage,
+    content: [...(Array.isArray(lastMessage?.content) ? lastMessage.content : []), marker],
+  };
+}
+
 function privateData(params: {
   modelContent?: DiagnosticModelCallContent;
   errorMessage?: string;
@@ -128,7 +333,13 @@ export function createClaudeCliModelCallDiagnostics(params: {
   transport: "paired-node-cli" | "stdio" | "stdio-live";
   now?: () => number;
 }) {
-  if (params.context.backendResolved.id !== "claude-cli") {
+  // Listener registration is process-stable after plugin startup. This attempt-local
+  // snapshot avoids trace ids, capture buffers, and byte accounting when nobody consumes them.
+  if (
+    params.context.backendResolved.id !== "claude-cli" ||
+    !areDiagnosticsEnabledForProcess() ||
+    !hasInternalDiagnosticEventListeners()
+  ) {
     return undefined;
   }
 
@@ -169,6 +380,19 @@ export function createClaudeCliModelCallDiagnostics(params: {
     trace,
   };
   const capturedAssistantMessages: Record<string, unknown>[] = [];
+  const outputContentBudget: DiagnosticContentBudget = {
+    remainingBytes:
+      MAX_CAPTURED_CONTENT_BYTES -
+      MAX_CAPTURED_OUTPUT_STRUCTURE_BYTES -
+      TRUNCATED_CONTENT_SUFFIX_BYTES -
+      FALLBACK_RESPONSE_RESERVE_BYTES,
+    // One item stays available for the truncation marker; one more is held
+    // separately for the final visible fallback until normal text arrives.
+    remainingItems: MAX_CAPTURED_OUTPUT_BLOCKS - 2,
+    fallbackReserveBytes: FALLBACK_RESPONSE_RESERVE_BYTES,
+    fallbackReserveItems: 1,
+    truncated: false,
+  };
   let started = false;
   let terminalEmitted = false;
   let startedAt = 0;
@@ -186,19 +410,37 @@ export function createClaudeCliModelCallDiagnostics(params: {
       ...(capture.inputMessages
         ? {
             inputMessages: cloneDiagnosticContentValue([
-              { role: "user", content: [{ type: "text", text: params.prompt }] },
+              {
+                role: "user",
+                content: [{ type: "text", text: captureBoundedText(params.prompt) }],
+              },
             ]),
           }
         : {}),
-      ...(capture.systemPrompt && params.systemPrompt ? { systemPrompt: params.systemPrompt } : {}),
+      ...(capture.systemPrompt && params.systemPrompt
+        ? { systemPrompt: captureBoundedText(params.systemPrompt) }
+        : {}),
     };
     return Object.keys(content).length > 0 ? content : undefined;
   };
   const outputMessages = (output?: CliOutput): unknown => {
     const messages = capturedAssistantMessages.slice();
     const responseText = output?.rawText ?? output?.text;
-    if (!hasTextContent(messages) && responseText) {
-      messages.push({ role: "assistant", content: [{ type: "text", text: responseText }] });
+    if (
+      !hasTextContent(messages) &&
+      responseText &&
+      messages.length < MAX_CAPTURED_OUTPUT_MESSAGES
+    ) {
+      const fallback = normalizeClaudeAssistantMessage(
+        { content: responseText },
+        outputContentBudget,
+      );
+      if (fallback) {
+        messages.push(fallback);
+      }
+    }
+    if (outputContentBudget.truncated) {
+      appendOutputTruncationMarker(messages);
     }
     return cloneDiagnosticContentValue(messages);
   };
@@ -238,20 +480,32 @@ export function createClaudeCliModelCallDiagnostics(params: {
     observeRequestPayload: (payload: string): void => {
       requestPayloadBytes = Buffer.byteLength(payload, "utf8");
     },
-    observeCliOutput: (chunk: string, stream: "stderr" | "stdout"): void => {
+    observeCliOutput: (
+      chunk: string,
+      stream: "stderr" | "stdout",
+      knownByteLength?: number,
+    ): void => {
       if (!chunk) {
         return;
       }
       firstCliOutputAt ??= now();
       if (stream === "stdout") {
-        responseStreamBytes += Buffer.byteLength(chunk, "utf8");
+        responseStreamBytes += knownByteLength ?? Buffer.byteLength(chunk, "utf8");
       }
     },
     observeAssistantMessage: (message: unknown): void => {
-      if (!capture.outputMessages) {
+      if (
+        !capture.outputMessages ||
+        ((outputContentBudget.remainingBytes <= 0 || outputContentBudget.remainingItems <= 0) &&
+          !(outputContentBudget.fallbackReserveItems > 0 && assistantMessageHasText(message))) ||
+        capturedAssistantMessages.length >= MAX_CAPTURED_OUTPUT_MESSAGES - 1
+      ) {
+        if (capture.outputMessages) {
+          outputContentBudget.truncated = true;
+        }
         return;
       }
-      const normalized = normalizeClaudeAssistantMessage(message);
+      const normalized = normalizeClaudeAssistantMessage(message, outputContentBudget);
       if (normalized) {
         capturedAssistantMessages.push(normalized);
       }
diff --git a/src/infra/diagnostic-event-listener-presence.ts b/src/infra/diagnostic-event-listener-presence.ts
new file mode 100644
index 000000000000..778bf3904017
--- /dev/null
+++ b/src/infra/diagnostic-event-listener-presence.ts
@@ -0,0 +1,50 @@
+/** Process-wide listener counts used to avoid telemetry work without consumers. */
+
+const DIAGNOSTIC_EVENT_LISTENER_PRESENCE_KEY = Symbol.for(
+  "openclaw.diagnosticEventListenerPresence.v1",
+);
+
+type DiagnosticEventListenerPresence = {
+  marker: symbol;
+  internalCount: number;
+  trustedCount: number;
+};
+
+function getDiagnosticEventListenerPresence(): DiagnosticEventListenerPresence {
+  const globalRecord = globalThis as Record<PropertyKey, unknown>;
+  const existing = globalRecord[DIAGNOSTIC_EVENT_LISTENER_PRESENCE_KEY];
+  if (
+    existing &&
+    typeof existing === "object" &&
+    (existing as Partial<DiagnosticEventListenerPresence>).marker ===
+      DIAGNOSTIC_EVENT_LISTENER_PRESENCE_KEY
+  ) {
+    return existing as DiagnosticEventListenerPresence;
+  }
+  const state: DiagnosticEventListenerPresence = {
+    marker: DIAGNOSTIC_EVENT_LISTENER_PRESENCE_KEY,
+    internalCount: 0,
+    trustedCount: 0,
+  };
+  Object.defineProperty(globalThis, DIAGNOSTIC_EVENT_LISTENER_PRESENCE_KEY, {
+    configurable: true,
+    enumerable: false,
+    value: state,
+    writable: false,
+  });
+  return state;
+}
+
+export function setInternalDiagnosticEventListenerCounts(
+  internalCount: number,
+  trustedCount: number,
+): void {
+  const state = getDiagnosticEventListenerPresence();
+  state.internalCount = internalCount;
+  state.trustedCount = trustedCount;
+}
+
+export function hasInternalDiagnosticEventListeners(): boolean {
+  const state = getDiagnosticEventListenerPresence();
+  return state.internalCount > 0 || state.trustedCount > 0;
+}
diff --git a/src/infra/diagnostic-events.test.ts b/src/infra/diagnostic-events.test.ts
index 4132bd991c18..9f30bc270514 100644
--- a/src/infra/diagnostic-events.test.ts
+++ b/src/infra/diagnostic-events.test.ts
@@ -1,6 +1,8 @@
 // Covers diagnostic event emission and metadata handling.
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { hasInternalDiagnosticEventListeners } from "./diagnostic-event-listener-presence.js";
 import {
+  areDiagnosticsEnabledForProcess,
   emitDiagnosticEvent,
   emitInternalDiagnosticEvent,
   emitTrustedDiagnosticEvent,
@@ -46,6 +48,25 @@ describe("diagnostic-events", () => {
     expect((message as string).startsWith(prefix)).toBe(true);
   }
 
+  it("reports active internal diagnostic listeners only while dispatch is enabled", () => {
+    const hasActiveListeners = () =>
+      areDiagnosticsEnabledForProcess() && hasInternalDiagnosticEventListeners();
+    expect(hasActiveListeners()).toBe(false);
+
+    const stopInternal = onInternalDiagnosticEvent(() => undefined);
+    expect(hasActiveListeners()).toBe(true);
+    setDiagnosticsEnabledForProcess(false);
+    expect(hasActiveListeners()).toBe(false);
+    setDiagnosticsEnabledForProcess(true);
+    stopInternal();
+    expect(hasActiveListeners()).toBe(false);
+
+    const stopTrusted = onTrustedInternalDiagnosticEvent(() => undefined);
+    expect(hasActiveListeners()).toBe(true);
+    stopTrusted();
+    expect(hasActiveListeners()).toBe(false);
+  });
+
   it("emits monotonic seq and timestamps to subscribers", () => {
     vi.spyOn(Date, "now").mockReturnValueOnce(111).mockReturnValueOnce(222);
     const events: Array<{ seq: number; ts: number; type: string }> = [];
diff --git a/src/infra/diagnostic-events.ts b/src/infra/diagnostic-events.ts
index 0efa29b6c1b4..ce716231e574 100644
--- a/src/infra/diagnostic-events.ts
+++ b/src/infra/diagnostic-events.ts
@@ -2,6 +2,7 @@
 import { randomUUID } from "node:crypto";
 import type { OpenClawConfig } from "../config/types.openclaw.js";
 import type { TalkBrain, TalkEventType, TalkMode, TalkTransport } from "../talk/talk-events.js";
+import { setInternalDiagnosticEventListenerCounts } from "./diagnostic-event-listener-presence.js";
 import {
   formatDiagnosticTraceparent,
   getActiveDiagnosticTraceContext,
@@ -1387,8 +1388,10 @@ export function emitFailoverEvent(event: Omit<DiagnosticFailoverEvent, "seq" | "
 export function onInternalDiagnosticEvent(listener: DiagnosticEventListener): () => void {
   const state = getDiagnosticEventsState();
   state.listeners.add(listener);
+  setInternalDiagnosticEventListenerCounts(state.listeners.size, state.trustedListeners.size);
   return () => {
     state.listeners.delete(listener);
+    setInternalDiagnosticEventListenerCounts(state.listeners.size, state.trustedListeners.size);
   };
 }
 
@@ -1398,8 +1401,10 @@ export function onTrustedInternalDiagnosticEvent(
 ): () => void {
   const state = getDiagnosticEventsState();
   state.trustedListeners.add(listener);
+  setInternalDiagnosticEventListenerCounts(state.listeners.size, state.trustedListeners.size);
   return () => {
     state.trustedListeners.delete(listener);
+    setInternalDiagnosticEventListenerCounts(state.listeners.size, state.trustedListeners.size);
   };
 }
 
@@ -1466,6 +1471,7 @@ export function resetDiagnosticEventsForTest(): void {
   state.seq = 0;
   state.listeners.clear();
   state.trustedListeners.clear();
+  setInternalDiagnosticEventListenerCounts(0, 0);
   state.toolExecutionListeners.clear();
   state.toolExecutionSeq = 0;
   state.dispatchDepth = 0;