diff --git a/nanobot/agent/context.py b/nanobot/agent/context.py
index 820baf5..2c648eb 100644
--- a/nanobot/agent/context.py
+++ b/nanobot/agent/context.py
@@ -59,6 +59,19 @@ Skills with available="false" need dependencies installed first - you can try in
         system = platform.system()
         runtime = f"{'macOS' if system == 'Darwin' else system} {platform.machine()}, Python {platform.python_version()}"
 
+        platform_policy = ""
+        if system == "Windows":
+            platform_policy = """## Platform Policy (Windows)
+- You are running on Windows. Do not assume GNU tools like `grep`, `sed`, or `awk` exist.
+- Prefer Windows-native commands or file tools when they are more reliable.
+- If terminal output is garbled, retry with UTF-8 output enabled.
+"""
+        else:
+            platform_policy = """## Platform Policy (POSIX)
+- You are running on a POSIX system. Prefer UTF-8 and standard shell tools.
+- Use file tools when they are simpler or more reliable than shell commands.
+"""
+
         return f"""# nanobot 🐈
 
 You are nanobot, a helpful AI assistant.
@@ -72,6 +85,8 @@ Your workspace is at: {workspace_path}
 - History log: {workspace_path}/memory/HISTORY.md (grep-searchable). Each entry starts with [YYYY-MM-DD HH:MM].
 - Custom skills: {workspace_path}/skills/{{skill-name}}/SKILL.md
 
+{platform_policy}
+
 ## nanobot Guidelines
 - State intent before tool calls, but NEVER predict or claim results before receiving them.
 - Before modifying a file, read it first. Do not assume files or directories exist.
diff --git a/nanobot/skills/memory/SKILL.md b/nanobot/skills/memory/SKILL.md
index 529a02d..3f0a8fc 100644
--- a/nanobot/skills/memory/SKILL.md
+++ b/nanobot/skills/memory/SKILL.md
@@ -9,15 +9,21 @@ always: true
 ## Structure
 
 - `memory/MEMORY.md` — Long-term facts (preferences, project context, relationships). Always loaded into your context.
-- `memory/HISTORY.md` — Append-only event log. NOT loaded into context. Search it with grep. Each entry starts with [YYYY-MM-DD HH:MM].
+- `memory/HISTORY.md` — Append-only event log. NOT loaded into context. Search it with grep-style tools or in-memory filters. Each entry starts with [YYYY-MM-DD HH:MM].
 
 ## Search Past Events
 
-```bash
-grep -i "keyword" memory/HISTORY.md
-```
+Choose the search method based on file size:
 
-Use the `exec` tool to run grep. Combine patterns: `grep -iE "meeting|deadline" memory/HISTORY.md`
+- Small `memory/HISTORY.md`: use `read_file`, then search in-memory
+- Large or long-lived `memory/HISTORY.md`: use the `exec` tool for targeted search
+
+Examples:
+- **Linux/macOS:** `grep -i "keyword" memory/HISTORY.md`
+- **Windows:** `findstr /i "keyword" memory\HISTORY.md`
+- **Cross-platform Python:** `python -c "from pathlib import Path; text = Path('memory/HISTORY.md').read_text(encoding='utf-8'); print('\n'.join([l for l in text.splitlines() if 'keyword' in l.lower()][-20:]))"`
+
+Prefer targeted command-line search for large history files.
 
 ## When to Update MEMORY.md