diff --git a/drizzle/migrations/0005_fix_chat_db_fk_normalization.sql b/drizzle/migrations/0005_fix_chat_db_fk_normalization.sql
new file mode 100644
index 00000000..d7204b23
--- /dev/null
+++ b/drizzle/migrations/0005_fix_chat_db_fk_normalization.sql
@@ -0,0 +1,90 @@
+-- Migration: fix_chat_db_fk_normalization
+-- Description: Redirect all user_id foreign keys from auth.users to public.users
+-- to support Clerk-authenticated users who exist only in public.users.
+-- This normalizes the schema so public.users is the canonical identity table.
+-- Root cause: Clerk users authenticate via Clerk (not Supabase Auth), so their
+-- user IDs exist in public.users but NOT in auth.users. The FK constraint
+-- chats_user_id_fkey pointed to auth.users.id, causing foreign key violations
+-- when inserting chats for Clerk-authenticated users.
+--
+-- Note: The 0001_sync_schema_full.sql migration creates the tables with
+-- correct public.users FKs, but pre-existing FKs from the original schema
+-- (pointing to auth.users) may still exist in some deployments.
+-- This migration ensures all FKs are corrected.
+--
+-- FK creation uses NOT VALID to avoid blocking writes during creation,
+-- then VALIDATE CONSTRAINT is called separately to enforce the constraint
+-- only after existing data is verified. See migration 0006 for index creation.
+
+-- Step 1: Drop all affected foreign key constraints referencing auth.users
+ALTER TABLE public.chats
+  DROP CONSTRAINT IF EXISTS chats_user_id_fkey;
+
+ALTER TABLE public.messages
+  DROP CONSTRAINT IF EXISTS messages_user_id_fkey;
+
+ALTER TABLE public.system_prompts
+  DROP CONSTRAINT IF EXISTS system_prompts_user_id_fkey;
+
+ALTER TABLE public.locations
+  DROP CONSTRAINT IF EXISTS locations_user_id_fkey;
+
+ALTER TABLE public.visualizations
+  DROP CONSTRAINT IF EXISTS visualizations_user_id_fkey;
+
+ALTER TABLE public.chat_participants
+  DROP CONSTRAINT IF EXISTS chat_participants_user_id_fkey;
+
+ALTER TABLE public.prompt_generation_jobs
+  DROP CONSTRAINT IF EXISTS prompt_generation_jobs_user_id_fkey;
+
+-- Step 2: Add new foreign key constraints referencing public.users.id (NOT VALID)
+ALTER TABLE public.chats
+  ADD CONSTRAINT chats_user_id_fkey
+    FOREIGN KEY (user_id) REFERENCES public.users(id) ON DELETE CASCADE NOT VALID;
+
+ALTER TABLE public.messages
+  ADD CONSTRAINT messages_user_id_fkey
+    FOREIGN KEY (user_id) REFERENCES public.users(id) ON DELETE CASCADE NOT VALID;
+
+ALTER TABLE public.system_prompts
+  ADD CONSTRAINT system_prompts_user_id_fkey
+    FOREIGN KEY (user_id) REFERENCES public.users(id) ON DELETE CASCADE NOT VALID;
+
+ALTER TABLE public.locations
+  ADD CONSTRAINT locations_user_id_fkey
+    FOREIGN KEY (user_id) REFERENCES public.users(id) ON DELETE CASCADE NOT VALID;
+
+ALTER TABLE public.visualizations
+  ADD CONSTRAINT visualizations_user_id_fkey
+    FOREIGN KEY (user_id) REFERENCES public.users(id) ON DELETE CASCADE NOT VALID;
+
+ALTER TABLE public.chat_participants
+  ADD CONSTRAINT chat_participants_user_id_fkey
+    FOREIGN KEY (user_id) REFERENCES public.users(id) ON DELETE CASCADE NOT VALID;
+
+ALTER TABLE public.prompt_generation_jobs
+  ADD CONSTRAINT prompt_generation_jobs_user_id_fkey
+    FOREIGN KEY (user_id) REFERENCES public.users(id) ON DELETE CASCADE NOT VALID;
+
+-- Step 3: Validate all constraints (safe to run after data is verified)
+ALTER TABLE public.chats
+  VALIDATE CONSTRAINT chats_user_id_fkey;
+
+ALTER TABLE public.messages
+  VALIDATE CONSTRAINT messages_user_id_fkey;
+
+ALTER TABLE public.system_prompts
+  VALIDATE CONSTRAINT system_prompts_user_id_fkey;
+
+ALTER TABLE public.locations
+  VALIDATE CONSTRAINT locations_user_id_fkey;
+
+ALTER TABLE public.visualizations
+  VALIDATE CONSTRAINT visualizations_user_id_fkey;
+
+ALTER TABLE public.chat_participants
+  VALIDATE CONSTRAINT chat_participants_user_id_fkey;
+
+ALTER TABLE public.prompt_generation_jobs
+  VALIDATE CONSTRAINT prompt_generation_jobs_user_id_fkey;
diff --git a/drizzle/migrations/0006_add_user_id_indexes.sql b/drizzle/migrations/0006_add_user_id_indexes.sql
new file mode 100644
index 00000000..a67ec00b
--- /dev/null
+++ b/drizzle/migrations/0006_add_user_id_indexes.sql
@@ -0,0 +1,17 @@
+-- Migration: add_user_id_indexes
+-- Description: Add performance indexes on user_id columns.
+-- These use CREATE INDEX CONCURRENTLY to avoid blocking writes.
+-- IMPORTANT: This migration MUST run outside a transaction.
+-- CREATE INDEX CONCURRENTLY cannot execute inside a transaction block.
+-- Run this file manually against the database:
+--   psql $POSTGRES_URL -f 0006_add_user_id_indexes.sql
+-- Or use the Supabase dashboard SQL editor (which does not wrap in transactions).
+-- Do NOT use drizzle-kit migrate for this file; it wraps in a transaction.
+
+CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_chats_user_id ON public.chats(user_id);
+CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_messages_user_id ON public.messages(user_id);
+CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_system_prompts_user_id ON public.system_prompts(user_id);
+CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_locations_user_id ON public.locations(user_id);
+CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_visualizations_user_id ON public.visualizations(user_id);
+CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_chat_participants_user_id ON public.chat_participants(user_id);
+CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_prompt_generation_jobs_user_id ON public.prompt_generation_jobs(user_id);