fix(schema): make agent_threads/messages migration work on fresh DBs

Wrap the migration with CREATE TABLE IF NOT EXISTS for both
agent_threads and agent_messages so it runs cleanly on new
deployments, not just databases where the Go API had already
created the tables. Also drop any threads left without a user
after backfill so the NOT NULL constraint can be enforced when
the user table is empty.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: raghavyuva

drizzle/0044_agent_threads_messages.sql

@@ -1,13 +1,39 @@
--- Add user_id column to existing agent_threads table (created by Go API)
--- For existing rows, we set a placeholder that must be backfilled
+-- Create agent_threads if it does not exist (fresh deployments).
+-- On existing deployments where the Go API already created the table,
+-- this is a no-op and the user_id column is added by the ALTER below.
+CREATE TABLE IF NOT EXISTS "agent_threads" (
+	"id" text PRIMARY KEY NOT NULL,
+	"title" text DEFAULT '' NOT NULL,
+	"metadata" text DEFAULT '{}',
+	"created_at" timestamp with time zone DEFAULT now() NOT NULL,
+	"updated_at" timestamp with time zone DEFAULT now() NOT NULL
+);
+--> statement-breakpoint
+-- Create agent_messages if it does not exist (fresh deployments).
+CREATE TABLE IF NOT EXISTS "agent_messages" (
+	"id" text PRIMARY KEY NOT NULL,
+	"thread_id" text NOT NULL,
+	"role" text NOT NULL,
+	"content" text DEFAULT '' NOT NULL,
+	"tool_calls" text DEFAULT '[]',
+	"tool_call_id" text DEFAULT '',
+	"created_at" timestamp with time zone DEFAULT now() NOT NULL,
+	"seq" integer NOT NULL
+);
+--> statement-breakpoint
+-- Add user_id column to agent_threads (existing Go-API tables won't have it).
 ALTER TABLE "agent_threads" ADD COLUMN IF NOT EXISTS "user_id" uuid;
 --> statement-breakpoint
--- Backfill existing threads: assign to the first user in the org from metadata
+-- Backfill existing threads: assign to the first user available.
+-- No-op on fresh deployments where the table is empty.
 UPDATE "agent_threads" SET "user_id" = (
   SELECT u.id FROM "user" u LIMIT 1
 ) WHERE "user_id" IS NULL;
 --> statement-breakpoint
--- Now make it NOT NULL
+-- If backfill could not find a user (e.g. fresh DB with empty user table),
+-- delete any orphaned threads so we can enforce NOT NULL.
+DELETE FROM "agent_threads" WHERE "user_id" IS NULL;
+--> statement-breakpoint
 ALTER TABLE "agent_threads" ALTER COLUMN "user_id" SET NOT NULL;
 --> statement-breakpoint
 DO $$ BEGIN
@@ -18,10 +44,9 @@ END $$;
 --> statement-breakpoint
 CREATE INDEX IF NOT EXISTS "idx_agent_threads_user" ON "agent_threads" USING btree ("user_id");
 --> statement-breakpoint
--- Clean orphaned messages whose thread no longer exists
+-- Clean orphaned messages whose thread no longer exists.
 DELETE FROM "agent_messages" WHERE "thread_id" NOT IN (SELECT "id" FROM "agent_threads");
 --> statement-breakpoint
--- Ensure agent_messages has FK to agent_threads
 DO $$ BEGIN
  ALTER TABLE "agent_messages" ADD CONSTRAINT "agent_messages_thread_id_agent_threads_id_fk" FOREIGN KEY ("thread_id") REFERENCES "public"."agent_threads"("id") ON DELETE cascade ON UPDATE no action;
 EXCEPTION