From b9b75805c91eed9cd89c0702d7eb7d9d5f566441 Mon Sep 17 00:00:00 2001
From: Elena Torro <elenatorro@gmail.com>
Date: Mon, 27 Jul 2026 16:48:36 +0200
Subject: [PATCH] :wrench: Warn at startup when headless wasm export is enabled

---
 exporter/src/app/core.cljs          |  8 ++++++++
 exporter/src/app/renderer/wasm.cljs |  2 +-
 exporter/src/app/wasm.cljs          | 12 +++++++++++-
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/exporter/src/app/core.cljs b/exporter/src/app/core.cljs
index 5ce68ebf98..35ebd830bd 100644
--- a/exporter/src/app/core.cljs
+++ b/exporter/src/app/core.cljs
@@ -12,6 +12,7 @@
    [app.config :as cf]
    [app.http :as http]
    [app.redis :as redis]
+   [app.wasm :as wasm]
    [promesa.core :as p]))
 
 (enable-console-print!)
@@ -23,6 +24,13 @@
           :public-uri (str (cf/get :public-uri))
           :internal-uri (str (cf/get-internal-uri))
           :version (:full cf/version))
+  (when (cf/get :wasm-headless)
+    (l/warn :msg "headless wasm export enabled (experimental)"
+            :hint (str "renders run in-process on a single shared wasm module "
+                       "and are serialized one at a time, so exports do not "
+                       "run concurrently; not recommended for busy instances")
+            :wasm-dir (wasm/artifact-dir)
+            :image-cache-mb (wasm/image-cache-mb)))
   (p/do!
    (bwr/init)
    (redis/init)
diff --git a/exporter/src/app/renderer/wasm.cljs b/exporter/src/app/renderer/wasm.cljs
index 92bc31e734..f4594d8bd2 100644
--- a/exporter/src/app/renderer/wasm.cljs
+++ b/exporter/src/app/renderer/wasm.cljs
@@ -442,7 +442,7 @@
                  ;; Trim the image store AFTER the request (never mid-render, so
                  ;; an image can't disappear under a running export). Images the
                  ;; next request needs again are simply re-provisioned.
-                 (let [evicted (wasm/evict-images! (cf/get :wasm-image-cache-mb 256))]
+                 (let [evicted (wasm/evict-images! (wasm/image-cache-mb))]
                    (when (pos? evicted)
                      (l/info :hint "wasm render: evicted cached images" :count evicted)))
                  result))
diff --git a/exporter/src/app/wasm.cljs b/exporter/src/app/wasm.cljs
index 2fcceb4ccf..8607166044 100644
--- a/exporter/src/app/wasm.cljs
+++ b/exporter/src/app/wasm.cljs
@@ -44,10 +44,20 @@
 ;; get_fonts_for_shape entry: [uuid 16 bytes][weight u32][style u32].
 (def ^:private FONT-ENTRY-BYTES 24)
 
-(defn- artifact-dir
+(defn artifact-dir
+  "Directory holding the built render-wasm artifact (render-wasm.js/.wasm).
+  The docker image points `PENPOT_WASM_DIR` at the copy shipped inside the
+  exporter bundle; the default is where `render-wasm/build` leaves it in
+  devenv."
   []
   (cf/get :wasm-dir "../frontend/resources/public/js"))
 
+(defn image-cache-mb
+  "Byte budget (in MB) the wasm image store is trimmed down to between
+  requests. See `evict-images!`."
+  []
+  (cf/get :wasm-image-cache-mb 256))
+
 (defn- read-result-bytes
   "Reads `len` bytes from the WASM heap starting at `offset`, copying them out
   (via `.slice`) before the buffer is freed."