diff --git a/src/tool_implementations.py b/src/tool_implementations.py
index 092747452..e45fde1f9 100644
--- a/src/tool_implementations.py
+++ b/src/tool_implementations.py
@@ -46,6 +46,9 @@ from src.tools.cookbook import (  # noqa: F401
     _scan_running_model_processes, _cookbook_kill_session,
     _MODEL_PROCESS_PATTERNS,
 )
+# Search domain extracted to src/tools/search.py (slice 1, #4082/#4071).
+# Re-imported here so this module stays a working facade.
+from src.tools.search import do_search_chats  # noqa: F401
 
 logger = logging.getLogger(__name__)
 
@@ -119,50 +122,6 @@ def _parse_tool_args(content):
         args = args["body"]
     return args
 
-# ---------------------------------------------------------------------------
-# Search chats
-# ---------------------------------------------------------------------------
-
-async def do_search_chats(query: str, limit: int = 20, owner: str | None = None) -> Dict:
-    """Search past session transcripts for the calling user's sessions only.
-
-    Without an owner filter this used to leak EVERY user's chat history
-    into the agent's `search_chats` results (v2 review HIGH-11). The
-    caller in `tool_execution.execute_tool_block` now plumbs the owner
-    through; legacy callers without owner pass through as before but
-    will only see legacy/null-owner rows.
-    """
-    try:
-        from src.session_search import search_session_messages
-
-        results = search_session_messages(query, limit=limit, owner=owner)
-        if not results:
-            return {"results": f"No chats found matching \"{query}\"."}
-
-        # Group by session to avoid duplicate links
-        seen_sessions = {}
-        for result in results:
-            if result.session_id not in seen_sessions:
-                seen_sessions[result.session_id] = result
-
-        lines = [f"Found {len(seen_sessions)} session(s) matching \"{query}\":\n"]
-        for sid, result in seen_sessions.items():
-            lines.append(f"- **{result.session_name}** (#{sid})")
-            lines.append(f"  Link: [Open chat](#{sid})")
-            lines.append(f"  Match ({result.role}): {result.content_snippet}")
-            if result.context_before:
-                before = result.context_before[-1]
-                lines.append(f"  Before ({before['role']}): {before['content'][:180]}")
-            if result.context_after:
-                after = result.context_after[0]
-                lines.append(f"  After ({after['role']}): {after['content'][:180]}")
-            lines.append("")
-
-        return {"results": "\n".join(lines)}
-    except Exception as e:
-        logger.error(f"search_chats failed: {e}")
-        return {"error": str(e), "exit_code": 1}
-
 
 # ---------------------------------------------------------------------------
 # Notes / checklists management tool
diff --git a/src/tools/__init__.py b/src/tools/__init__.py
index 50c427baf..5f48777f0 100644
--- a/src/tools/__init__.py
+++ b/src/tools/__init__.py
@@ -21,3 +21,4 @@ from src.tools.cookbook import (  # noqa: F401
     _scan_running_model_processes, _cookbook_kill_session,
     _MODEL_PROCESS_PATTERNS,
 )
+from src.tools.search import do_search_chats  # noqa: F401
diff --git a/src/tools/search.py b/src/tools/search.py
new file mode 100644
index 000000000..882951333
--- /dev/null
+++ b/src/tools/search.py
@@ -0,0 +1,51 @@
+"""Search-domain tool implementations.
+
+Extracted from tool_implementations.py as part of slice 1 (#4082/#4071).
+Holds the search_chats tool.
+``src.tool_implementations`` re-exports these for backward compatibility.
+"""
+import logging
+from typing import Dict
+
+logger = logging.getLogger(__name__)
+
+
+async def do_search_chats(query: str, limit: int = 20, owner: str | None = None) -> Dict:
+    """Search past session transcripts for the calling user's sessions only.
+
+    Without an owner filter this used to leak EVERY user's chat history
+    into the agent's `search_chats` results (v2 review HIGH-11). The
+    caller in `tool_execution.execute_tool_block` now plumbs the owner
+    through; legacy callers without owner pass through as before but
+    will only see legacy/null-owner rows.
+    """
+    try:
+        from src.session_search import search_session_messages
+
+        results = search_session_messages(query, limit=limit, owner=owner)
+        if not results:
+            return {"results": f"No chats found matching \"{query}\"."}
+
+        # Group by session to avoid duplicate links
+        seen_sessions = {}
+        for result in results:
+            if result.session_id not in seen_sessions:
+                seen_sessions[result.session_id] = result
+
+        lines = [f"Found {len(seen_sessions)} session(s) matching \"{query}\":\n"]
+        for sid, result in seen_sessions.items():
+            lines.append(f"- **{result.session_name}** (#{sid})")
+            lines.append(f"  Link: [Open chat](#{sid})")
+            lines.append(f"  Match ({result.role}): {result.content_snippet}")
+            if result.context_before:
+                before = result.context_before[-1]
+                lines.append(f"  Before ({before['role']}): {before['content'][:180]}")
+            if result.context_after:
+                after = result.context_after[0]
+                lines.append(f"  After ({after['role']}): {after['content'][:180]}")
+            lines.append("")
+
+        return {"results": "\n".join(lines)}
+    except Exception as e:
+        logger.error(f"search_chats failed: {e}")
+        return {"error": str(e), "exit_code": 1}