diff --git a/src/agents/cli-runner/helpers.ts b/src/agents/cli-runner/helpers.ts
index 26ee43495..6103125b0 100644
--- a/src/agents/cli-runner/helpers.ts
+++ b/src/agents/cli-runner/helpers.ts
@@ -13,6 +13,7 @@ import type { EmbeddedContextFile } from "../pi-embedded-helpers.js";
 import { buildSystemPromptParams } from "../system-prompt-params.js";
 import { resolveDefaultModelForAgent } from "../model-selection.js";
 import { buildAgentSystemPrompt } from "../system-prompt.js";
+import { buildTtsSystemPromptHint } from "../../tts/tts.js";
 
 const CLI_RUN_QUEUE = new Map<string, Promise<unknown>>();
 
@@ -194,6 +195,7 @@ export function buildSystemPrompt(params: {
       defaultModel: defaultModelLabel,
     },
   });
+  const ttsHint = params.config ? buildTtsSystemPromptHint(params.config) : undefined;
   return buildAgentSystemPrompt({
     workspaceDir: params.workspaceDir,
     defaultThinkLevel: params.defaultThinkLevel,
@@ -209,6 +211,7 @@ export function buildSystemPrompt(params: {
     userTime,
     userTimeFormat,
     contextFiles: params.contextFiles,
+    ttsHint,
   });
 }
 
diff --git a/src/agents/pi-embedded-runner/compact.ts b/src/agents/pi-embedded-runner/compact.ts
index 771994a83..8b151a3fc 100644
--- a/src/agents/pi-embedded-runner/compact.ts
+++ b/src/agents/pi-embedded-runner/compact.ts
@@ -66,6 +66,7 @@ import { splitSdkTools } from "./tool-split.js";
 import type { EmbeddedPiCompactResult } from "./types.js";
 import { formatUserTime, resolveUserTimeFormat, resolveUserTimezone } from "../date-time.js";
 import { describeUnknownError, mapThinkingLevel, resolveExecToolDefaults } from "./utils.js";
+import { buildTtsSystemPromptHint } from "../../tts/tts.js";
 
 export async function compactEmbeddedPiSession(params: {
   sessionId: string;
@@ -298,6 +299,7 @@ export async function compactEmbeddedPiSession(params: {
           cwd: process.cwd(),
           moduleUrl: import.meta.url,
         });
+        const ttsHint = params.config ? buildTtsSystemPromptHint(params.config) : undefined;
         const appendPrompt = buildEmbeddedSystemPrompt({
           workspaceDir: effectiveWorkspace,
           defaultThinkLevel: params.thinkLevel,
@@ -310,6 +312,7 @@ export async function compactEmbeddedPiSession(params: {
             : undefined,
           skillsPrompt,
           docsPath: docsPath ?? undefined,
+          ttsHint,
           promptMode,
           runtimeInfo,
           messageToolHints,
diff --git a/src/agents/pi-embedded-runner/run/attempt.ts b/src/agents/pi-embedded-runner/run/attempt.ts
index c121bb42b..776525658 100644
--- a/src/agents/pi-embedded-runner/run/attempt.ts
+++ b/src/agents/pi-embedded-runner/run/attempt.ts
@@ -78,6 +78,7 @@ import { toClientToolDefinitions } from "../../pi-tool-definition-adapter.js";
 import { buildSystemPromptParams } from "../../system-prompt-params.js";
 import { describeUnknownError, mapThinkingLevel } from "../utils.js";
 import { resolveSandboxRuntimeStatus } from "../../sandbox/runtime-status.js";
+import { buildTtsSystemPromptHint } from "../../../tts/tts.js";
 import { isTimeoutError } from "../../failover-error.js";
 import { getGlobalHookRunner } from "../../../plugins/hook-runner-global.js";
 import { MAX_IMAGE_BYTES } from "../../../media/constants.js";
@@ -315,6 +316,7 @@ export async function runEmbeddedAttempt(
       cwd: process.cwd(),
       moduleUrl: import.meta.url,
     });
+    const ttsHint = params.config ? buildTtsSystemPromptHint(params.config) : undefined;
 
     const appendPrompt = buildEmbeddedSystemPrompt({
       workspaceDir: effectiveWorkspace,
@@ -328,6 +330,7 @@ export async function runEmbeddedAttempt(
         : undefined,
       skillsPrompt,
       docsPath: docsPath ?? undefined,
+      ttsHint,
       workspaceNotes,
       reactionGuidance,
       promptMode,
diff --git a/src/agents/pi-embedded-runner/system-prompt.ts b/src/agents/pi-embedded-runner/system-prompt.ts
index cde0f0a15..33c4bfc8b 100644
--- a/src/agents/pi-embedded-runner/system-prompt.ts
+++ b/src/agents/pi-embedded-runner/system-prompt.ts
@@ -16,6 +16,7 @@ export function buildEmbeddedSystemPrompt(params: {
   heartbeatPrompt?: string;
   skillsPrompt?: string;
   docsPath?: string;
+  ttsHint?: string;
   reactionGuidance?: {
     level: "minimal" | "extensive";
     channel: string;
@@ -55,6 +56,7 @@ export function buildEmbeddedSystemPrompt(params: {
     heartbeatPrompt: params.heartbeatPrompt,
     skillsPrompt: params.skillsPrompt,
     docsPath: params.docsPath,
+    ttsHint: params.ttsHint,
     workspaceNotes: params.workspaceNotes,
     reactionGuidance: params.reactionGuidance,
     promptMode: params.promptMode,
diff --git a/src/agents/system-prompt.test.ts b/src/agents/system-prompt.test.ts
index ece7d8dcc..14f643e55 100644
--- a/src/agents/system-prompt.test.ts
+++ b/src/agents/system-prompt.test.ts
@@ -34,6 +34,7 @@ describe("buildAgentSystemPrompt", () => {
       toolNames: ["message", "memory_search"],
       docsPath: "/tmp/clawd/docs",
       extraSystemPrompt: "Subagent details",
+      ttsHint: "Voice (TTS) is enabled.",
     });
 
     expect(prompt).not.toContain("## User Identity");
@@ -42,6 +43,7 @@ describe("buildAgentSystemPrompt", () => {
     expect(prompt).not.toContain("## Documentation");
     expect(prompt).not.toContain("## Reply Tags");
     expect(prompt).not.toContain("## Messaging");
+    expect(prompt).not.toContain("## Voice (TTS)");
     expect(prompt).not.toContain("## Silent Replies");
     expect(prompt).not.toContain("## Heartbeats");
     expect(prompt).toContain("## Subagent Context");
@@ -49,6 +51,16 @@ describe("buildAgentSystemPrompt", () => {
     expect(prompt).toContain("Subagent details");
   });
 
+  it("includes voice hint when provided", () => {
+    const prompt = buildAgentSystemPrompt({
+      workspaceDir: "/tmp/clawd",
+      ttsHint: "Voice (TTS) is enabled.",
+    });
+
+    expect(prompt).toContain("## Voice (TTS)");
+    expect(prompt).toContain("Voice (TTS) is enabled.");
+  });
+
   it("adds reasoning tag hint when enabled", () => {
     const prompt = buildAgentSystemPrompt({
       workspaceDir: "/tmp/clawd",
diff --git a/src/agents/system-prompt.ts b/src/agents/system-prompt.ts
index 74be661aa..41ec9a7d5 100644
--- a/src/agents/system-prompt.ts
+++ b/src/agents/system-prompt.ts
@@ -103,6 +103,13 @@ function buildMessagingSection(params: {
   ];
 }
 
+function buildVoiceSection(params: { isMinimal: boolean; ttsHint?: string }) {
+  if (params.isMinimal) return [];
+  const hint = params.ttsHint?.trim();
+  if (!hint) return [];
+  return ["## Voice (TTS)", hint, ""];
+}
+
 function buildDocsSection(params: { docsPath?: string; isMinimal: boolean; readToolName: string }) {
   const docsPath = params.docsPath?.trim();
   if (!docsPath || params.isMinimal) return [];
@@ -137,6 +144,7 @@ export function buildAgentSystemPrompt(params: {
   heartbeatPrompt?: string;
   docsPath?: string;
   workspaceNotes?: string[];
+  ttsHint?: string;
   /** Controls which hardcoded sections to include. Defaults to "full". */
   promptMode?: PromptMode;
   runtimeInfo?: {
@@ -464,6 +472,7 @@ export function buildAgentSystemPrompt(params: {
       runtimeChannel,
       messageToolHints: params.messageToolHints,
     }),
+    ...buildVoiceSection({ isMinimal, ttsHint: params.ttsHint }),
   ];
 
   if (extraSystemPrompt) {
diff --git a/src/auto-reply/reply/commands-context-report.ts b/src/auto-reply/reply/commands-context-report.ts
index c38ae6b35..887b10722 100644
--- a/src/auto-reply/reply/commands-context-report.ts
+++ b/src/auto-reply/reply/commands-context-report.ts
@@ -12,6 +12,7 @@ import { buildToolSummaryMap } from "../../agents/tool-summaries.js";
 import { resolveBootstrapContextForRun } from "../../agents/bootstrap-files.js";
 import type { SessionSystemPromptReport } from "../../config/sessions/types.js";
 import { getRemoteSkillEligibility } from "../../infra/skills-remote.js";
+import { buildTtsSystemPromptHint } from "../../tts/tts.js";
 import type { ReplyPayload } from "../types.js";
 import type { HandleCommandsParams } from "./commands-types.js";
 
@@ -128,6 +129,7 @@ async function resolveContextReport(
         },
       }
     : { enabled: false };
+  const ttsHint = params.cfg ? buildTtsSystemPromptHint(params.cfg) : undefined;
 
   const systemPrompt = buildAgentSystemPrompt({
     workspaceDir,
@@ -145,6 +147,7 @@ async function resolveContextReport(
     contextFiles: injectedFiles,
     skillsPrompt,
     heartbeatPrompt: undefined,
+    ttsHint,
     runtimeInfo,
     sandboxInfo,
   });
diff --git a/src/tts/tts.ts b/src/tts/tts.ts
index c89acc05c..54aa4c512 100644
--- a/src/tts/tts.ts
+++ b/src/tts/tts.ts
@@ -244,6 +244,19 @@ export function resolveTtsPrefsPath(config: ResolvedTtsConfig): string {
   return path.join(CONFIG_DIR, "settings", "tts.json");
 }
 
+export function buildTtsSystemPromptHint(cfg: ClawdbotConfig): string | undefined {
+  const config = resolveTtsConfig(cfg);
+  const prefsPath = resolveTtsPrefsPath(config);
+  if (!isTtsEnabled(config, prefsPath)) return undefined;
+  const maxLength = getTtsMaxLength(prefsPath);
+  const summarize = isSummarizationEnabled(prefsPath) ? "on" : "off";
+  return [
+    "Voice (TTS) is enabled.",
+    `Keep spoken text ≤${maxLength} chars to avoid auto-summary (summary ${summarize}).`,
+    "Use [[tts:...]] and optional [[tts:text]]...[[/tts:text]] to control voice/expressiveness.",
+  ].join("\n");
+}
+
 function readPrefs(prefsPath: string): TtsUserPrefs {
   try {
     if (!existsSync(prefsPath)) return {};