diff --git a/navi/core/registry.py b/navi/core/registry.py
index e9df3fd..db2b53f 100644
--- a/navi/core/registry.py
+++ b/navi/core/registry.py
@@ -12,6 +12,7 @@
     HttpRequestTool,
     ImageViewTool,
     MemoryForgetTool,
+    MemorySaveTool,
     MemorySearchTool,
     SpawnAgentTool,
     SshExecTool,
@@ -111,12 +112,13 @@
     manual_tool = ToolManualTool(registry=tools)
     memory_search = MemorySearchTool(memory_store) if memory_store else None
     memory_forget = MemoryForgetTool(memory_store) if memory_store else None
+    memory_save = MemorySaveTool(memory_store) if memory_store else None
     builtins = [WebSearchTool(), FilesystemTool(), HttpRequestTool(), WebViewTool(),
                 CodeExecTool(), TerminalTool(), SshExecTool(), ImageViewTool(),
                 ShareFileTool(),
                 TodoTool(), ScratchpadTool(), reload_tool, write_tool, list_tool, manual_tool]
     if memory_search:
-        builtins.extend([memory_search, memory_forget])
+        builtins.extend([memory_search, memory_forget, memory_save])
     for builtin in builtins:
         tools.register(builtin, builtin=True)
 
diff --git a/navi/profiles/secretary.py b/navi/profiles/secretary.py
index 16af71f..b84436b 100644
--- a/navi/profiles/secretary.py
+++ b/navi/profiles/secretary.py
@@ -30,7 +30,7 @@
         "todo", "scratchpad", "switch_profile",
         "web_search", "web_view", "http_request",
         "filesystem", "code_exec", "image_view",
-        "memory_search", "memory_forget",
+        "memory_search", "memory_forget", "memory_save",
         "list_tools", "tool_manual",
         "spawn_agent",
         "share_file",
diff --git a/navi/profiles/server_admin.py b/navi/profiles/server_admin.py
index c788941..7c3cbe4 100644
--- a/navi/profiles/server_admin.py
+++ b/navi/profiles/server_admin.py
@@ -40,7 +40,7 @@
         "todo", "scratchpad", "switch_profile",
         "web_search", "web_view", "http_request",
         "filesystem", "code_exec", "terminal", "ssh_exec", "image_view",
-        "memory_search", "memory_forget",
+        "memory_search", "memory_forget", "memory_save",
         "reload_tools", "write_tool", "list_tools", "tool_manual",
         "spawn_agent",
         "share_file",
diff --git a/navi/profiles/smart_home.py b/navi/profiles/smart_home.py
index 5edcd93..dbf03a3 100644
--- a/navi/profiles/smart_home.py
+++ b/navi/profiles/smart_home.py
@@ -34,7 +34,7 @@
         "todo", "scratchpad", "switch_profile",
         "web_search", "web_view", "http_request",
         "filesystem", "code_exec", "ssh_exec", "image_view",
-        "memory_search", "memory_forget",
+        "memory_search", "memory_forget", "memory_save",
         "reload_tools", "write_tool", "list_tools", "tool_manual",
         "spawn_agent",
         "share_file",
diff --git a/navi/tools/__init__.py b/navi/tools/__init__.py
index 1c07ae0..839eaf3 100644
--- a/navi/tools/__init__.py
+++ b/navi/tools/__init__.py
@@ -7,6 +7,7 @@
 from .spawn_agent import SpawnAgentTool
 from .terminal import TerminalTool
 from .memory_forget import MemoryForgetTool
+from .memory_save import MemorySaveTool
 from .memory_search import MemorySearchTool
 from .todo import TodoTool
 from .scratchpad import ScratchpadTool
@@ -27,6 +28,7 @@
     "WebViewTool",
     "MemorySearchTool",
     "MemoryForgetTool",
+    "MemorySaveTool",
     "SpawnAgentTool",
     "TodoTool",
     "ScratchpadTool",
diff --git a/navi/tools/memory_save.py b/navi/tools/memory_save.py
new file mode 100644
index 0000000..2eed1f2
--- /dev/null
+++ b/navi/tools/memory_save.py
@@ -0,0 +1,71 @@
+"""Memory save tool — persist a fact about the user to long-term memory."""
+
+from navi.memory.store import MemoryStore
+from navi.tools.base import current_session_id
+
+from .base import Tool, ToolResult
+
+_VALID_CATEGORIES = {"profile", "preferences", "technical", "projects", "other"}
+
+
+class MemorySaveTool(Tool):
+    name = "memory_save"
+    description = (
+        "Save or update a fact about the user in long-term memory. "
+        "Use this when the user tells you something stable and reusable — name, location, "
+        "preferences, ongoing projects, technical environment, recurring workflows, etc. "
+        "Also use it to correct an outdated fact you know is wrong. "
+        "Facts survive across sessions and are available via memory_search."
+    )
+    parameters = {
+        "type": "object",
+        "properties": {
+            "category": {
+                "type": "string",
+                "enum": ["profile", "preferences", "technical", "projects", "other"],
+                "description": (
+                    "Broad category for the fact. "
+                    "profile=who they are, preferences=what they like/dislike, "
+                    "technical=OS/tools/servers/languages, projects=ongoing work, other=anything else."
+                ),
+            },
+            "key": {
+                "type": "string",
+                "description": (
+                    "Short snake_case identifier, unique within the category. "
+                    "Examples: 'name', 'primary_os', 'home_server_ip', 'preferred_language', "
+                    "'current_project', 'response_language'."
+                ),
+            },
+            "value": {
+                "type": "string",
+                "description": "The fact itself, written as a concise plain-text statement.",
+            },
+        },
+        "required": ["category", "key", "value"],
+    }
+
+    def __init__(self, memory_store: MemoryStore) -> None:
+        self._store = memory_store
+
+    async def execute(self, params: dict) -> ToolResult:
+        category = params.get("category", "").strip().lower()
+        key = params.get("key", "").strip()
+        value = params.get("value", "").strip()
+
+        if not category:
+            return ToolResult(success=False, output="category is required.", error="missing category")
+        if category not in _VALID_CATEGORIES:
+            return ToolResult(
+                success=False,
+                output=f"Invalid category '{category}'. Must be one of: {', '.join(sorted(_VALID_CATEGORIES))}",
+                error="invalid category",
+            )
+        if not key:
+            return ToolResult(success=False, output="key is required.", error="missing key")
+        if not value:
+            return ToolResult(success=False, output="value is required.", error="missing value")
+
+        session_id = current_session_id.get(None)
+        await self._store.upsert_fact(category, key, value, session_id)
+        return ToolResult(success=True, output=f"Saved [{category}] {key}: {value}")
diff --git a/persona.txt b/persona.txt
index 3327d00..1e8ceda 100644
--- a/persona.txt
+++ b/persona.txt
@@ -122,7 +122,14 @@
 
 Do NOT call memory_search as a reflex at the start of every session — only when the context genuinely calls for it.
 
-Call memory_forget only when the user explicitly asks you to forget something, or when you know a stored fact is clearly wrong or outdated.
+Call memory_save immediately when:
+- The user tells you anything stable and reusable: their name, location, employer, family, devices, server IPs, recurring projects, language preference, habits, or explicit instructions about how they want to be helped.
+- You notice an existing fact is wrong or outdated — correct it with a fresh memory_save call (no need to memory_forget first; save overwrites by key).
+- The user says "remember that..." or similar.
+
+Do NOT save ephemeral facts: temporary states, one-off tasks, or things specific to this session only.
+
+Call memory_forget only when the user explicitly asks you to forget something that memory_save cannot replace (e.g., "delete everything about X"), or when a key no longer exists in any useful form.
 
 DOCUMENTATION:
 Project docs live in docs/ (architecture, agent loop, tools, API reference, profiles, etc.).