diff --git a/navi/core/agent.py b/navi/core/agent.py
index 9ff833a..225b536 100644
--- a/navi/core/agent.py
+++ b/navi/core/agent.py
@@ -85,9 +85,11 @@
         tool_schemas = [t.schema() for t in tools]
         llm = self._get_backend(profile.llm_backend)
 
-        # System prompt only goes into context (not display history)
-        if not session.context:
-            session.context.append(Message(
+        # System prompt only goes into context (not display history).
+        # Use role check rather than empty check: backward-compat sessions have
+        # context initialised from messages (which never contain a system message).
+        if not any(m.role == "system" for m in session.context):
+            session.context.insert(0, Message(
                 role="system",
                 content=self._build_system_prompt(profile.system_prompt),
             ))
@@ -152,9 +154,11 @@
         tool_schemas = [t.schema() for t in tools]
         llm = self._get_backend(profile.llm_backend)
 
-        # System prompt only goes into context (not display history)
-        if not session.context:
-            session.context.append(Message(
+        # System prompt only goes into context (not display history).
+        # Use role check rather than empty check: backward-compat sessions have
+        # context initialised from messages (which never contain a system message).
+        if not any(m.role == "system" for m in session.context):
+            session.context.insert(0, Message(
                 role="system",
                 content=self._build_system_prompt(profile.system_prompt),
             ))
diff --git a/navi/core/session.py b/navi/core/session.py
index 4b5a7e8..790815a 100644
--- a/navi/core/session.py
+++ b/navi/core/session.py
@@ -14,6 +14,7 @@
     profile_id: str
     messages: list[Message] = Field(default_factory=list)   # full display history (never compressed)
     context: list[Message] = Field(default_factory=list)    # LLM context (may be compressed)
+    context_token_count: int = 0   # accumulated total; reset to 0 after compression
     pinned: bool = False
     created_at: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))
     last_active: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))