diff --git a/.env.example b/.env.example
index b9bfcada0ec..f251fc1e609 100644
--- a/.env.example
+++ b/.env.example
@@ -87,7 +87,8 @@ RELAY_URL=ws://localhost:3000
 # -----------------------------------------------------------------------------
 # The local MinIO container is reachable from host processes at localhost:9000.
 # Path style keeps the bucket in the URL path and is required by this local DNS
-# setup. Use `virtual` only when the provider requires bucket-as-subdomain URLs.
+# setup. Use `virtual` only when the provider requires bucket-as-subdomain URLs
+# (for example, real S3 endpoints rather than local MinIO).
 BUZZ_S3_ENDPOINT=http://localhost:9000
 BUZZ_S3_ACCESS_KEY=buzz_dev
 BUZZ_S3_SECRET_KEY=buzz_dev_secret
diff --git a/README.md b/README.md
index 72af92ce138..cd95f3f826e 100644
--- a/README.md
+++ b/README.md
@@ -229,6 +229,7 @@ A Rust workspace of focused crates. Single source of truth: the relay. See [ARCH
 <summary><strong>Configuration</strong> (env vars, defaults work for local dev)</summary>
 
 All defaults work out of the box. Override via `.env`. Full reference in [`.env.example`](.env.example).
+For local MinIO, keep `BUZZ_S3_ADDRESSING_STYLE=path`; real S3-style providers may require `virtual` bucket-subdomain addressing instead.
 
 </details>
 
diff --git a/deploy/compose/.env.example b/deploy/compose/.env.example
index f6ab4fcab97..3b7bb17c0e4 100644
--- a/deploy/compose/.env.example
+++ b/deploy/compose/.env.example
@@ -32,8 +32,12 @@ POSTGRES_PASSWORD=CHANGE_ME_RANDOM_PASSWORD
 REDIS_PASSWORD=CHANGE_ME_RANDOM_PASSWORD
 BUZZ_S3_ACCESS_KEY=CHANGE_ME_RANDOM_ACCESS_KEY
 BUZZ_S3_SECRET_KEY=CHANGE_ME_RANDOM_SECRET_KEY
+# Override this for external S3-compatible storage; the default targets the
+# bundled MinIO service.
+BUZZ_S3_ENDPOINT=http://minio:9000
 BUZZ_S3_BUCKET=buzz-media
-# Bundled MinIO uses path-style URLs; deploy/compose/compose.yml pins this.
+# Bundled MinIO uses path-style URLs. External S3-compatible providers may
+# require virtual addressing.
 BUZZ_S3_ADDRESSING_STYLE=path
 
 # Optional host ports. Base compose publishes the relay directly on BUZZ_HTTP_PORT.
diff --git a/deploy/compose/README.md b/deploy/compose/README.md
index bb0e63fe15d..ca7d4d59ee7 100644
--- a/deploy/compose/README.md
+++ b/deploy/compose/README.md
@@ -38,11 +38,13 @@ keypair.
   migrations.
 - The stack uses Postgres, Redis, MinIO, and a git data volume because
   those are real Buzz dependencies today. Minimal mode can simplify this later.
-- The bundled Compose stack fixes the relay endpoint to `http://minio:9000` and
-  `BUZZ_S3_ADDRESSING_STYLE=path`: Docker DNS resolves `minio`, not
-  `<bucket>.minio`. It is not configurable for an external S3 provider through
-  `.env`; use the Helm chart or a custom Compose configuration for providers
-  such as new Railway Storage Buckets that require `virtual` addressing.
+- The bundled Compose stack defaults `BUZZ_S3_ENDPOINT` to
+  `http://minio:9000` and `BUZZ_S3_ADDRESSING_STYLE=path`: Docker DNS resolves
+  `minio`, not `<bucket>.minio`. Keep `path` for bundled MinIO; check your
+  provider's addressing requirements before copying that default to real S3,
+  R2, or another S3-compatible service. Set both variables in `.env` when
+  pointing the relay at an external provider that requires a different endpoint
+  or `virtual` addressing.
 
 Run `./run.sh backup-hint` for the backup checklist.
 
diff --git a/deploy/compose/compose.yml b/deploy/compose/compose.yml
index 15337c92a27..ac3d16e343b 100644
--- a/deploy/compose/compose.yml
+++ b/deploy/compose/compose.yml
@@ -11,9 +11,9 @@ services:
       BUZZ_METRICS_PORT: "9102"
       DATABASE_URL: postgres://${POSTGRES_USER:-buzz}:${POSTGRES_PASSWORD:?set POSTGRES_PASSWORD}@postgres:5432/${POSTGRES_DB:-buzz}
       REDIS_URL: redis://:${REDIS_PASSWORD:?set REDIS_PASSWORD}@redis:6379
-      BUZZ_S3_ENDPOINT: http://minio:9000
+      BUZZ_S3_ENDPOINT: ${BUZZ_S3_ENDPOINT:-http://minio:9000}
       # Docker DNS resolves `minio`, not arbitrary `<bucket>.minio` hosts.
-      BUZZ_S3_ADDRESSING_STYLE: path
+      BUZZ_S3_ADDRESSING_STYLE: ${BUZZ_S3_ADDRESSING_STYLE:-path}
       BUZZ_S3_ACCESS_KEY: ${BUZZ_S3_ACCESS_KEY:?set BUZZ_S3_ACCESS_KEY}
       BUZZ_S3_SECRET_KEY: ${BUZZ_S3_SECRET_KEY:?set BUZZ_S3_SECRET_KEY}
       BUZZ_S3_BUCKET: ${BUZZ_S3_BUCKET:-buzz-media}