diff --git a/compose.yml b/compose.yml
index 112d08d..eafc3d6 100644
--- a/compose.yml
+++ b/compose.yml
@@ -57,14 +57,15 @@ services:
     restart: unless-stopped
     environment:
       NODE_ENV: production
-      # Every renderer setting carries the RENDERER_ prefix so it cannot clash
-      # with the bot's variables, which Coolify also injects into this service.
+      # Every renderer setting carries the RENDERER_ prefix so it reads as a
+      # renderer setting and cannot clash with the bot's variables.
       RENDERER_HOST: 0.0.0.0
       RENDERER_PORT: "3000"   # keep in sync with the bot's RENDERER_URL and the healthcheck
-      RENDERER_MAX_CONCURRENT_RENDERS: ${RENDERER_MAX_CONCURRENT_RENDERS:-1}
-      RENDERER_RENDER_TIMEOUT_MS: ${RENDERER_RENDER_TIMEOUT_MS:-15000}
-      RENDERER_MAX_OPTIONS: ${RENDERER_MAX_OPTIONS:-32}
-      RENDERER_MAX_OPTION_CHARS: ${RENDERER_MAX_OPTION_CHARS:-40}
+      # Tuning is left out on purpose: the renderer's own defaults apply
+      # (RENDERER_MAX_CONCURRENT_RENDERS=1, RENDERER_RENDER_TIMEOUT_MS=15000,
+      # RENDERER_MAX_OPTIONS=32, RENDERER_MAX_OPTION_CHARS=40). Coolify lists
+      # every ${VAR} referenced here as a setting, so to override one, add it
+      # here as a literal, e.g. RENDERER_MAX_OPTIONS: "48".
     expose:
       - "3000"
     healthcheck:
diff --git a/docs/deploy-coolify-selfhosted.md b/docs/deploy-coolify-selfhosted.md
index 5ff605e..150a862 100644
--- a/docs/deploy-coolify-selfhosted.md
+++ b/docs/deploy-coolify-selfhosted.md
@@ -62,8 +62,12 @@ to it.
 
 Renderer tuning (`RENDERER_MAX_CONCURRENT_RENDERS`,
 `RENDERER_RENDER_TIMEOUT_MS`, `RENDERER_MAX_OPTIONS`,
-`RENDERER_MAX_OPTION_CHARS`) can be set in Coolify too; the defaults are in
-[`renderer/docs/deployment.md`](../renderer/docs/deployment.md). Give the host
+`RENDERER_MAX_OPTION_CHARS`) is optional and needs nothing in Coolify: the
+renderer's defaults apply, listed in
+[`renderer/docs/deployment.md`](../renderer/docs/deployment.md). Coolify lists
+every `${VAR}` that `compose.yml` references as a setting, so the tuning values
+are deliberately not referenced there; to override one, add it to the
+`renderer` service's `environment:` in `compose.yml` as a literal value. Give the host
 1-2 GB of headroom for the renderer's Chrome.
 
 Outside compose, set `RENDERER_URL` to the base URL of any service that
diff --git a/renderer/docs/deployment.md b/renderer/docs/deployment.md
index bcd3f28..6270ed8 100644
--- a/renderer/docs/deployment.md
+++ b/renderer/docs/deployment.md
@@ -39,8 +39,9 @@ RENDERER_MAX_OPTIONS=32
 RENDERER_MAX_OPTION_CHARS=40
 ```
 
-The root `compose.yml` forwards the tuning values with `${VAR:-default}`
-fallbacks, so unset or empty variables use the defaults above.
+An unset or empty variable uses the default above. The root `compose.yml`
+sets only `RENDERER_HOST` and `RENDERER_PORT`, so the tuning values use these
+defaults unless added there.
 
 Start with 1-2 vCPU and 1-2 GB RAM. Increase only after render benchmarks show
 the service is CPU-bound or concurrency-limited.