feat(chat): add admin-editable assistant system prompt

backend/server/chat/admin.py

@@ -1,6 +1,8 @@
 from django.contrib import admin
+from django.db import models
+from django.forms import Textarea
 
-from .models import ChatConversation, ChatMessage
+from .models import ChatConversation, ChatMessage, ChatSystemPrompt
 
 
 @admin.register(ChatConversation)
@@ -15,3 +17,14 @@ class ChatMessageAdmin(admin.ModelAdmin):
     list_display = ("id", "conversation", "role", "name", "created_at")
     search_fields = ("conversation__id", "content", "name")
     list_filter = ("role", "created_at")
+
+
+@admin.register(ChatSystemPrompt)
+class ChatSystemPromptAdmin(admin.ModelAdmin):
+    readonly_fields = ("updated_at",)
+    formfield_overrides = {
+        models.TextField: {"widget": Textarea(attrs={"rows": 20, "cols": 120})},
+    }
+
+    def has_add_permission(self, request):
+        return not ChatSystemPrompt.objects.exists()

backend/server/chat/llm_client.py

@@ -9,6 +9,33 @@ from integrations.models import UserAPIKey
 
 logger = logging.getLogger(__name__)
 
+DEFAULT_SYSTEM_PROMPT = """You are a helpful travel planning assistant for the Voyage travel app. You help users discover places, plan trips, and organize their itineraries.
+
+Your capabilities:
+- Search for interesting places (restaurants, tourist attractions, hotels) near any location
+- View and manage the user's trip collections and itineraries
+- Add new locations to trip itineraries
+- Check weather/temperature data for travel dates
+
+When suggesting places:
+- Be specific with names, addresses, and why a place is worth visiting
+- Consider the user's travel dates and weather conditions
+- Group suggestions logically (by area, by type, by day)
+
+When modifying itineraries:
+- Confirm with the user before the first add_to_itinerary action in a conversation
+- After the user clearly approves adding items (for example: "yes", "go ahead", "add them", "just add things there"), stop re-confirming and call add_to_itinerary directly for subsequent additions in that conversation
+- Suggest logical ordering based on geography
+- Consider travel time between locations
+
+When chat context includes a trip collection:
+- Treat context as itinerary-wide (potentially multiple stops), not a single destination
+- Use get_trip_details first when you need complete collection context before searching for places
+- Ground place searches in trip stops and dates from the provided trip context
+- Only call search_places when you have a concrete, non-empty location string; if location is missing or unclear, ask a clarifying question to obtain it first
+
+Be conversational, helpful, and enthusiastic about travel. Keep responses concise but informative."""
+
 PROVIDER_MODEL_PREFIX = {
     "openai": "openai",
     "anthropic": "anthropic",
@@ -321,34 +348,15 @@ def get_aggregated_preferences(collection):
 
 def get_system_prompt(user, collection=None):
     """Build the system prompt with user context."""
+    from chat.models import ChatSystemPrompt
     from integrations.models import UserRecommendationPreferenceProfile
 
-    base_prompt = """You are a helpful travel planning assistant for the Voyage travel app. You help users discover places, plan trips, and organize their itineraries.
-
-Your capabilities:
-- Search for interesting places (restaurants, tourist attractions, hotels) near any location
-- View and manage the user's trip collections and itineraries
-- Add new locations to trip itineraries
-- Check weather/temperature data for travel dates
-
-When suggesting places:
-- Be specific with names, addresses, and why a place is worth visiting
-- Consider the user's travel dates and weather conditions
-- Group suggestions logically (by area, by type, by day)
-
-When modifying itineraries:
-- Confirm with the user before the first add_to_itinerary action in a conversation
-- After the user clearly approves adding items (for example: "yes", "go ahead", "add them", "just add things there"), stop re-confirming and call add_to_itinerary directly for subsequent additions in that conversation
-- Suggest logical ordering based on geography
-- Consider travel time between locations
-
-When chat context includes a trip collection:
-- Treat context as itinerary-wide (potentially multiple stops), not a single destination
-- Use get_trip_details first when you need complete collection context before searching for places
-- Ground place searches in trip stops and dates from the provided trip context
-- Only call search_places when you have a concrete, non-empty location string; if location is missing or unclear, ask a clarifying question to obtain it first
-
-Be conversational, helpful, and enthusiastic about travel. Keep responses concise but informative."""
+    custom = ChatSystemPrompt.load()
+    base_prompt = (
+        custom.prompt_text
+        if custom and custom.prompt_text and custom.prompt_text.strip()
+        else DEFAULT_SYSTEM_PROMPT
+    )
 
     if collection and collection.shared_with.count() > 0:
         base_prompt += get_aggregated_preferences(collection)

backend/server/chat/migrations/0002_chatsystemprompt.py

@@ -0,0 +1,37 @@
+# Generated by Django 5.2.12 on 2026-03-10
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("chat", "0001_initial"),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="ChatSystemPrompt",
+            fields=[
+                (
+                    "id",
+                    models.BigAutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                (
+                    "prompt_text",
+                    models.TextField(
+                        help_text="Base system prompt for the travel assistant. User and party travel preferences are appended automatically."
+                    ),
+                ),
+                ("updated_at", models.DateTimeField(auto_now=True)),
+            ],
+            options={
+                "verbose_name": "Chat System Prompt",
+                "verbose_name_plural": "Chat System Prompt",
+            },
+        ),
+    ]

backend/server/chat/models.py

@@ -45,3 +45,37 @@ class ChatMessage(models.Model):
 
     class Meta:
         ordering = ["created_at"]
+
+
+class ChatSystemPrompt(models.Model):
+    """Admin-editable system prompt for the travel assistant.
+
+    Only one instance should exist (singleton pattern via Django admin).
+    The prompt text replaces the hardcoded base prompt in get_system_prompt().
+    Dynamic user/party preference injection is appended automatically.
+    """
+
+    prompt_text = models.TextField(
+        help_text="Base system prompt for the travel assistant. "
+        "User and party travel preferences are appended automatically."
+    )
+    updated_at = models.DateTimeField(auto_now=True)
+
+    class Meta:
+        verbose_name = "Chat System Prompt"
+        verbose_name_plural = "Chat System Prompt"
+
+    def __str__(self):
+        return f"System Prompt (updated {self.updated_at})"
+
+    def save(self, *args, **kwargs):
+        self.pk = 1
+        super().save(*args, **kwargs)
+
+    @classmethod
+    def load(cls):
+        """Return the singleton instance or None if not configured."""
+        try:
+            return cls.objects.get(pk=1)
+        except cls.DoesNotExist:
+            return None