diff --git a/.env.example b/.env.example
index 3de6771..f74b416 100644
--- a/.env.example
+++ b/.env.example
@@ -23,11 +23,11 @@ ADMIN_IDS=
 # Only the twentyq module needs this. Leave blank to disable that command.
 GEMINI_API_KEY=
 
-# SOURCE_COMMIT is injected into the container at runtime by Coolify (a
-# predefined env var holding the commit SHA); read at startup for the
-# deploynotify owner DM. Leave unset for local `docker compose up` —
-# deploynotify just stays silent.
-# SOURCE_COMMIT=
+# SOURCE_COMMIT (commit SHA) is auto-injected into the container at runtime by
+# Coolify and read at startup for the deploynotify owner DM — do NOT set it here
+# and do NOT declare it in docker-compose (that would clobber Coolify's value
+# with an empty string). Local `docker compose up` has none, so deploynotify
+# just stays silent.
 
 # ====================== Leave UNSET on self-host ==================
 # These are AWS-only. cmd/server reads secrets directly from the plain env
diff --git a/docker-compose.yml b/docker-compose.yml
index 5c88dcb..54ece36 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -16,10 +16,11 @@ services:
       ADMIN_IDS: ${ADMIN_IDS}              # CSV of admin Telegram user ids
       # --- Optional ---
       GEMINI_API_KEY: ${GEMINI_API_KEY}    # only the twentyq module needs it
-      # Coolify injects SOURCE_COMMIT (commit SHA) at deploy time; passed to the
-      # container so deploynotify DMs the owner once per new version. Empty (e.g.
-      # local `docker compose up` without it) just stays silent.
-      SOURCE_COMMIT: ${SOURCE_COMMIT:-}
+      # SOURCE_COMMIT (commit SHA, read at startup for the deploynotify owner DM)
+      # is auto-injected into the container by Coolify — do NOT declare it here.
+      # A `SOURCE_COMMIT: ${SOURCE_COMMIT:-}` entry resolves to "" at compose-parse
+      # time and would clobber Coolify's runtime value. Local `docker compose up`
+      # has no SOURCE_COMMIT, so deploynotify just stays silent there.
       # Storage auto-selects mongodb because MONGO_URL is set — no KV_PROVIDER.
       # The in-process cron scheduler runs by default — no CRON_MODE.
       # PORT defaults to 8080 (internal health server) — omit unless overriding.
diff --git a/docs/deploy-coolify-selfhosted.md b/docs/deploy-coolify-selfhosted.md
index f03fc1b..f0df31c 100644
--- a/docs/deploy-coolify-selfhosted.md
+++ b/docs/deploy-coolify-selfhosted.md
@@ -88,11 +88,12 @@ SSM/AWS lookup that fails with no AWS creds and bricks startup), `KV_PROVIDER`,
    bot token; a second poller gets HTTP 409, and a second in-process scheduler
    double-fires crons. Prefer **stop-first redeploys** so two containers never
    overlap near a cron time.
-5. **deploynotify commit SHA:** Coolify injects `SOURCE_COMMIT` (a predefined
-   runtime env var) into the container, and the compose `environment` forwards
-   it, so the bot reads it at startup and DMs the owner the "new version"
-   notice — no manual wiring. Without it, `deploynotify` stays silent (no
-   crash) — but you lose that notification.
+5. **deploynotify commit SHA:** Coolify auto-injects `SOURCE_COMMIT` (a
+   predefined runtime env var) into the container, and the bot reads it at
+   startup to DM the owner the "new version" notice — no manual wiring, and do
+   **not** declare `SOURCE_COMMIT` in compose/env (a `${SOURCE_COMMIT:-}` entry
+   resolves to `""` at parse time and clobbers Coolify's value). Without it,
+   `deploynotify` stays silent (no crash) — but you lose that notification.
 6. **Health check:** use Coolify's HTTP monitor against `GET /` (returns
    `text/plain` `miti99bot ok`). Do **not** use a compose `healthcheck` — the
    distroless image has no shell/curl and `cmd/server` has no `-healthcheck`