feat(privacy): redact PII from LLM context when privacy.redact_pii is enabled

Add privacy.redact_pii config option (boolean, default false). When
enabled, the gateway redacts personally identifiable information from
the system prompt before sending it to the LLM provider:

- Phone numbers (user IDs on WhatsApp/Signal) → hashed to user_<sha256>
- User IDs → hashed to user_<sha256>
- Chat IDs → numeric portion hashed, platform prefix preserved
- Home channel IDs → hashed
- Names/usernames → NOT affected (user-chosen, publicly visible)

Hashes are deterministic (same user → same hash) so the model can
still distinguish users in group chats. Routing and delivery use
the original values internally — redaction only affects LLM context.

Inspired by OpenClaw PR #47959.

gateway/run.py

@@ -1452,8 +1452,17 @@ class GatewayRunner:
         # Set environment variables for tools
         self._set_session_env(context)
         
+        # Read privacy.redact_pii from config (re-read per message)
+        _redact_pii = False
+        try:
+            with open(_config_path, encoding="utf-8") as _pf:
+                _pcfg = yaml.safe_load(_pf) or {}
+            _redact_pii = bool((_pcfg.get("privacy") or {}).get("redact_pii", False))
+        except Exception:
+            pass
+
         # Build the context prompt to inject
-        context_prompt = build_session_context_prompt(context)
+        context_prompt = build_session_context_prompt(context, redact_pii=_redact_pii)
         
         # If the previous session expired and was auto-reset, prepend a notice
         # so the agent knows this is a fresh conversation (not an intentional /reset).

gateway/session.py

@@ -8,9 +8,11 @@ Handles:
 - Dynamic system prompt injection (agent knows its context)
 """
 
+import hashlib
 import logging
 import os
 import json
+import re
 import uuid
 from pathlib import Path
 from datetime import datetime, timedelta
@@ -19,6 +21,41 @@ from typing import Dict, List, Optional, Any
 
 logger = logging.getLogger(__name__)
 
+
+# ---------------------------------------------------------------------------
+# PII redaction helpers
+# ---------------------------------------------------------------------------
+
+_PHONE_RE = re.compile(r"^\+?\d[\d\-\s]{6,}$")
+
+
+def _hash_id(value: str) -> str:
+    """Deterministic 12-char hex hash of an identifier."""
+    return hashlib.sha256(value.encode("utf-8")).hexdigest()[:12]
+
+
+def _hash_sender_id(value: str) -> str:
+    """Hash a sender ID to ``user_<12hex>``."""
+    return f"user_{_hash_id(value)}"
+
+
+def _hash_chat_id(value: str) -> str:
+    """Hash the numeric portion of a chat ID, preserving platform prefix.
+
+    ``telegram:12345`` → ``telegram:<hash>``
+    ``12345``          → ``<hash>``
+    """
+    colon = value.find(":")
+    if colon > 0:
+        prefix = value[:colon]
+        return f"{prefix}:{_hash_id(value[colon + 1:])}"
+    return _hash_id(value)
+
+
+def _looks_like_phone(value: str) -> bool:
+    """Return True if *value* looks like a phone number (E.164 or similar)."""
+    return bool(_PHONE_RE.match(value.strip()))
+
 from .config import (
     Platform,
     GatewayConfig,
@@ -146,7 +183,11 @@ class SessionContext:
         }
 
 
-def build_session_context_prompt(context: SessionContext) -> str:
+def build_session_context_prompt(
+    context: SessionContext,
+    *,
+    redact_pii: bool = False,
+) -> str:
     """
     Build the dynamic system prompt section that tells the agent about its context.
     
@@ -154,6 +195,10 @@ def build_session_context_prompt(context: SessionContext) -> str:
     - Where messages are coming from
     - What platforms are connected
     - Where it can deliver scheduled task outputs
+
+    When *redact_pii* is True, phone numbers are stripped and user/chat IDs
+    are replaced with deterministic hashes before being sent to the LLM.
+    Routing still uses the original values (they stay in SessionSource).
     """
     lines = [
         "## Current Session Context",
@@ -165,7 +210,25 @@ def build_session_context_prompt(context: SessionContext) -> str:
     if context.source.platform == Platform.LOCAL:
         lines.append(f"**Source:** {platform_name} (the machine running this agent)")
     else:
-        lines.append(f"**Source:** {platform_name} ({context.source.description})")
+        # Build a description that respects PII redaction
+        src = context.source
+        if redact_pii:
+            # Build a safe description without raw IDs
+            _uname = src.user_name or (
+                _hash_sender_id(src.user_id) if src.user_id else "user"
+            )
+            _cname = src.chat_name or _hash_chat_id(src.chat_id)
+            if src.chat_type == "dm":
+                desc = f"DM with {_uname}"
+            elif src.chat_type == "group":
+                desc = f"group: {_cname}"
+            elif src.chat_type == "channel":
+                desc = f"channel: {_cname}"
+            else:
+                desc = _cname
+        else:
+            desc = src.description
+        lines.append(f"**Source:** {platform_name} ({desc})")
     
     # Channel topic (if available - provides context about the channel's purpose)
     if context.source.chat_topic:
@@ -175,7 +238,10 @@ def build_session_context_prompt(context: SessionContext) -> str:
     if context.source.user_name:
         lines.append(f"**User:** {context.source.user_name}")
     elif context.source.user_id:
-        lines.append(f"**User ID:** {context.source.user_id}")
+        uid = context.source.user_id
+        if redact_pii:
+            uid = _hash_sender_id(uid)
+        lines.append(f"**User ID:** {uid}")
     
     # Platform-specific behavioral notes
     if context.source.platform == Platform.SLACK:
@@ -210,7 +276,8 @@ def build_session_context_prompt(context: SessionContext) -> str:
         lines.append("")
         lines.append("**Home Channels (default destinations):**")
         for platform, home in context.home_channels.items():
-            lines.append(f"  - {platform.value}: {home.name} (ID: {home.chat_id})")
+            hc_id = _hash_chat_id(home.chat_id) if redact_pii else home.chat_id
+            lines.append(f"  - {platform.value}: {home.name} (ID: {hc_id})")
     
     # Delivery options for scheduled tasks
     lines.append("")
@@ -220,7 +287,10 @@ def build_session_context_prompt(context: SessionContext) -> str:
     if context.source.platform == Platform.LOCAL:
         lines.append("- `\"origin\"` → Local output (saved to files)")
     else:
-        lines.append(f"- `\"origin\"` → Back to this chat ({context.source.chat_name or context.source.chat_id})")
+        _origin_label = context.source.chat_name or (
+            _hash_chat_id(context.source.chat_id) if redact_pii else context.source.chat_id
+        )
+        lines.append(f"- `\"origin\"` → Back to this chat ({_origin_label})")
     
     # Local always available
     lines.append("- `\"local\"` → Save to local files only (~/.hermes/cron/output/)")