diff --git a/docker-compose.prod.yml b/docker-compose.prod.yml
index bfaa678..5d5d42e 100644
--- a/docker-compose.prod.yml
+++ b/docker-compose.prod.yml
@@ -1442,7 +1442,12 @@ services:
       - INSTANCE_BASE_PATH=/app/instance
       # Pass the host's compose project name so the agent runs `docker compose -p <project>`
       # against the right project (not basename of INSTANCE_BASE_PATH, which is "instance").
+      # COMPOSE_PROJECT is read by the agent's TypeScript for slug derivation;
+      # COMPOSE_PROJECT_NAME is what Docker Compose itself reads when upgrade.sh
+      # shells out to `docker compose ...` — without it, compose defaults to
+      # basename(cwd)="instance" and collides with the host's existing containers.
       - COMPOSE_PROJECT=${COMPOSE_PROJECT_NAME:-changemaker-lite}
+      - COMPOSE_PROJECT_NAME=${COMPOSE_PROJECT_NAME:-changemaker-lite}
     logging: *default-logging
     networks:
       - changemaker-lite
diff --git a/docker-compose.yml b/docker-compose.yml
index fa307a1..b4631c8 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -1465,7 +1465,12 @@ services:
       - INSTANCE_BASE_PATH=/app/instance
       # Pass the host's compose project name so the agent runs `docker compose -p <project>`
       # against the right project (not basename of INSTANCE_BASE_PATH, which is "instance").
+      # COMPOSE_PROJECT is read by the agent's TypeScript for slug derivation;
+      # COMPOSE_PROJECT_NAME is what Docker Compose itself reads when upgrade.sh
+      # shells out to `docker compose ...` — without it, compose defaults to
+      # basename(cwd)="instance" and collides with the host's existing containers.
       - COMPOSE_PROJECT=${COMPOSE_PROJECT_NAME:-changemaker-lite}
+      - COMPOSE_PROJECT_NAME=${COMPOSE_PROJECT_NAME:-changemaker-lite}
     logging: *default-logging
     networks:
       - changemaker-lite