diff --git a/src/agents/pi-embedded-runner/run.ts b/src/agents/pi-embedded-runner/run.ts
index 870453f38..a3ea34154 100644
--- a/src/agents/pi-embedded-runner/run.ts
+++ b/src/agents/pi-embedded-runner/run.ts
@@ -367,6 +367,7 @@ export async function runEmbeddedPiAgent(
                 log.warn(
                   `context overflow detected; attempting auto-compaction for ${provider}/${modelId}`,
                 );
+                await params.onCompactionStart?.();
                 overflowCompactionAttempted = true;
                 const compactResult = await compactEmbeddedPiSessionDirect({
                   sessionId: params.sessionId,
diff --git a/src/agents/pi-embedded-runner/run/params.ts b/src/agents/pi-embedded-runner/run/params.ts
index b21a5e3fc..4151075e3 100644
--- a/src/agents/pi-embedded-runner/run/params.ts
+++ b/src/agents/pi-embedded-runner/run/params.ts
@@ -86,6 +86,7 @@ export type RunEmbeddedPiAgentParams = {
   onBlockReplyFlush?: () => void | Promise<void>;
   blockReplyBreak?: "text_end" | "message_end";
   blockReplyChunking?: BlockReplyChunking;
+  onCompactionStart?: () => void | Promise<void>;
   onReasoningStream?: (payload: { text?: string; mediaUrls?: string[] }) => void | Promise<void>;
   onToolResult?: (payload: { text?: string; mediaUrls?: string[] }) => void | Promise<void>;
   onAgentEvent?: (evt: { stream: string; data: Record<string, unknown> }) => void;
diff --git a/src/auto-reply/reply/agent-runner-execution.ts b/src/auto-reply/reply/agent-runner-execution.ts
index f86ecb8a9..c7a2b86ff 100644
--- a/src/auto-reply/reply/agent-runner-execution.ts
+++ b/src/auto-reply/reply/agent-runner-execution.ts
@@ -276,6 +276,13 @@ export async function runAgentTurnWithFallback(params: {
             abortSignal: params.opts?.abortSignal,
             blockReplyBreak: params.resolvedBlockStreamingBreak,
             blockReplyChunking: params.blockReplyChunking,
+            onCompactionStart: async () => {
+              if (params.opts?.onPartialReply) {
+                await params.opts.onPartialReply({
+                  text: "🧹 Compacting context, please wait...",
+                });
+              }
+            },
             onPartialReply: allowPartialStream
               ? async (payload) => {
                   const textForTyping = await handlePartialForTyping(payload);
diff --git a/src/entry.ts b/src/entry.ts
index 8cd1c5060..0e5a55fae 100644
--- a/src/entry.ts
+++ b/src/entry.ts
@@ -5,11 +5,13 @@ import process from "node:process";
 
 import { applyCliProfileEnv, parseCliProfileArgs } from "./cli/profile.js";
 import { isTruthyEnvValue } from "./infra/env.js";
+import { installGlobalFetchSanitizer } from "./infra/fetch.js";
 import { installProcessWarningFilter } from "./infra/warnings.js";
 import { attachChildProcessBridge } from "./process/child-process-bridge.js";
 
 process.title = "moltbot";
 installProcessWarningFilter();
+installGlobalFetchSanitizer();
 
 if (process.argv.includes("--no-color")) {
   process.env.NO_COLOR = "1";
diff --git a/src/infra/fetch.ts b/src/infra/fetch.ts
index 61012e485..9997d868e 100644
--- a/src/infra/fetch.ts
+++ b/src/infra/fetch.ts
@@ -4,6 +4,90 @@ type FetchWithPreconnect = typeof fetch & {
 
 type RequestInitWithDuplex = RequestInit & { duplex?: "half" };
 
+function sanitizeHeaderValue(value: string): string {
+  // fast path for common ascii
+  let isClean = true;
+  for (let i = 0; i < value.length; i++) {
+    if (value.charCodeAt(i) > 255) {
+      isClean = false;
+      break;
+    }
+  }
+  if (isClean) return value; // eslint-disable-line no-control-regex
+
+  // Node's undici fetch crashes on header values > 255 (ByteString).
+  // We sanitize them by replacing non-latin1 chars with '?'.
+  return value.replace(/[^\u0000-\u00ff]/g, "?"); // eslint-disable-line no-control-regex
+}
+
+function sanitizeHeaders(init?: RequestInit): RequestInit | undefined {
+  if (!init || !init.headers) return init;
+
+  if (typeof Headers !== "undefined" && init.headers instanceof Headers) {
+    // Headers object: iterate
+    const dirtyEntries: [string, string][] = [];
+    init.headers.forEach((value, key) => {
+      const sanitized = sanitizeHeaderValue(value);
+      if (sanitized !== value) {
+        dirtyEntries.push([key, sanitized]);
+      }
+    });
+
+    if (dirtyEntries.length > 0) {
+      const h = new Headers(init.headers);
+      for (const [k, v] of dirtyEntries) {
+        h.set(k, v);
+      }
+      return { ...init, headers: h };
+    }
+    return init; // No changes
+  }
+
+  if (Array.isArray(init.headers)) {
+    // Array of tuples
+    const dirtyIndices: [number, string][] = [];
+    for (let i = 0; i < init.headers.length; i++) {
+      const entry = init.headers[i];
+      if (entry.length >= 2) {
+        const val = entry[1];
+        const sanitized = sanitizeHeaderValue(val);
+        if (sanitized !== val) {
+          dirtyIndices.push([i, sanitized]);
+        }
+      }
+    }
+    if (dirtyIndices.length > 0) {
+      const next = [...init.headers];
+      for (const [i, v] of dirtyIndices) {
+        next[i] = [next[i][0], v];
+      }
+      return { ...init, headers: next };
+    }
+    return init;
+  }
+
+  // Record<string, string>
+  const rec = init.headers as Record<string, string>;
+  let nextRec: Record<string, string> | undefined;
+
+  for (const k in rec) {
+    const v = rec[k];
+    if (typeof v === "string") {
+      const s = sanitizeHeaderValue(v);
+      if (s !== v) {
+        if (!nextRec) nextRec = { ...rec };
+        nextRec[k] = s;
+      }
+    }
+  }
+
+  if (nextRec) {
+    return { ...init, headers: nextRec };
+  }
+
+  return init;
+}
+
 function withDuplex(
   init: RequestInit | undefined,
   input: RequestInfo | URL,
@@ -23,7 +107,8 @@ function withDuplex(
 
 export function wrapFetchWithAbortSignal(fetchImpl: typeof fetch): typeof fetch {
   const wrapped = ((input: RequestInfo | URL, init?: RequestInit) => {
-    const patchedInit = withDuplex(init, input);
+    const sanitizedInit = sanitizeHeaders(init);
+    const patchedInit = withDuplex(sanitizedInit, input);
     const signal = patchedInit?.signal;
     if (!signal) return fetchImpl(input, patchedInit);
     if (typeof AbortSignal !== "undefined" && signal instanceof AbortSignal) {
@@ -65,3 +150,9 @@ export function resolveFetch(fetchImpl?: typeof fetch): typeof fetch | undefined
   if (!resolved) return undefined;
   return wrapFetchWithAbortSignal(resolved);
 }
+
+export function installGlobalFetchSanitizer(): void {
+  if (globalThis.fetch) {
+    globalThis.fetch = wrapFetchWithAbortSignal(globalThis.fetch);
+  }
+}