diff --git a/infra/disclosure-stack/docker-compose.yml b/infra/disclosure-stack/docker-compose.yml
index adbc594..4356b64 100644
--- a/infra/disclosure-stack/docker-compose.yml
+++ b/infra/disclosure-stack/docker-compose.yml
@@ -327,6 +327,9 @@ services:
       SUPABASE_SERVICE_ROLE_KEY: ${SERVICE_ROLE_KEY}
       NEXT_PUBLIC_SITE_URL: https://${DOMAIN_MAIN}
       UFO_ROOT: /data/ufo
+      # W3.9 — /c/[slug] case-report viewer + BureauSnapshot read the
+      # markdown files the investigator-runtime writes. Mounted below.
+      CASE_ROOT: /data/ufo/case
       # W1-TD#10: bump pg pool from default 5 to 20 (chat agent + hybrid_search
       # can saturate the smaller pool under concurrent load).
       PG_POOL_MAX: ${PG_POOL_MAX:-20}
@@ -354,6 +357,8 @@ services:
       - ${DATA_WIKI}:/data/ufo/wiki:ro
       - ${DATA_PROCESSING}:/data/ufo/processing:ro
       - ${DATA_RAW}:/data/ufo/raw:ro
+      # W3.9 — case/ is the investigator-runtime's write surface; web reads it.
+      - ${CASE_ROOT:-/data/disclosure/case}:/data/ufo/case:ro
     labels:
       - traefik.enable=true
       - traefik.docker.network=traefik-public