diff --git a/.taskfiles/engine.yml b/.taskfiles/engine.yml
index 244b48353..6393fa64d 100644
--- a/.taskfiles/engine.yml
+++ b/.taskfiles/engine.yml
@@ -37,9 +37,23 @@ tasks:
     dir: src
     vars:
       # When PORT is provided (e.g. from dev:all), use it directly.
-      # When running standalone, probe for a free port starting at 5001.
+      # With ENGINE_PORT_PROBE=false (Docker), use the fixed STIRLING_ENGINE_PORT
+      # (default 5001) without probing. Otherwise probe for a free port from 5001.
       PORT:
-        sh: '{{if .PORT}}echo {{.PORT}}{{else if eq OS "windows"}}{{.ENGINE_FIND_FREE_PORT_PS}} 5001{{else}}{{.ENGINE_FIND_FREE_PORT_SH}} 5001{{end}}'
+        sh: |
+          if [ -n "{{.PORT}}" ]; then
+            echo "{{.PORT}}"
+          elif [ -f /.dockerenv ] || [ "${ENGINE_PORT_PROBE:-true}" = "false" ]; then
+            # Never probe in a container: the port is fixed and the probe script
+            # isn't shipped in the image. /.dockerenv auto-detects Docker; the
+            # ENGINE_PORT_PROBE=false flag forces fixed-port mode anywhere else.
+            # The probe is a dev-only convenience for avoiding local port clashes.
+            echo "${STIRLING_ENGINE_PORT:-5001}"
+          elif [ "{{OS}}" = "windows" ]; then
+            {{.ENGINE_FIND_FREE_PORT_PS}} 5001
+          else
+            {{.ENGINE_FIND_FREE_PORT_SH}} 5001
+          fi
     env:
       PYTHONUNBUFFERED: "1"
     cmds:
@@ -52,9 +66,23 @@ tasks:
     dir: src
     vars:
       # When PORT is provided (e.g. from dev:all), use it directly.
-      # When running standalone, probe for a free port starting at 5001.
+      # With ENGINE_PORT_PROBE=false (Docker), use the fixed STIRLING_ENGINE_PORT
+      # (default 5001) without probing. Otherwise probe for a free port from 5001.
       PORT:
-        sh: '{{if .PORT}}echo {{.PORT}}{{else if eq OS "windows"}}{{.ENGINE_FIND_FREE_PORT_PS}} 5001{{else}}{{.ENGINE_FIND_FREE_PORT_SH}} 5001{{end}}'
+        sh: |
+          if [ -n "{{.PORT}}" ]; then
+            echo "{{.PORT}}"
+          elif [ -f /.dockerenv ] || [ "${ENGINE_PORT_PROBE:-true}" = "false" ]; then
+            # Never probe in a container: the port is fixed and the probe script
+            # isn't shipped in the image. /.dockerenv auto-detects Docker; the
+            # ENGINE_PORT_PROBE=false flag forces fixed-port mode anywhere else.
+            # The probe is a dev-only convenience for avoiding local port clashes.
+            echo "${STIRLING_ENGINE_PORT:-5001}"
+          elif [ "{{OS}}" = "windows" ]; then
+            {{.ENGINE_FIND_FREE_PORT_PS}} 5001
+          else
+            {{.ENGINE_FIND_FREE_PORT_SH}} 5001
+          fi
     env:
       PYTHONUNBUFFERED: "1"
     cmds:
diff --git a/engine/Dockerfile b/engine/Dockerfile
index e3f548e8d..375983142 100644
--- a/engine/Dockerfile
+++ b/engine/Dockerfile
@@ -27,6 +27,10 @@ COPY .taskfiles/ ./.taskfiles/
 ENV PATH="/app/engine/.venv/bin:$PATH"
 ENV PYTHONUNBUFFERED=1
 ENV STIRLING_ENGINE_WORKERS=4
+# Container runs on a fixed port; skip the host-only free-port probe (its script
+# is not shipped in the image). engine:run honours these.
+ENV ENGINE_PORT_PROBE=false
+ENV STIRLING_ENGINE_PORT=5001
 
 EXPOSE 5001