diff --git a/.github/workflows/ci-ubicloud.yml b/.github/workflows/ci-ubicloud.yml
index f83d9f7..2b3ecf1 100644
--- a/.github/workflows/ci-ubicloud.yml
+++ b/.github/workflows/ci-ubicloud.yml
@@ -2,10 +2,10 @@ name: CI full build + e2e (Ubicloud)
 
 # Main/PR gate: build all 6 KiCad WASM tools + run the wxWidgets + KiCad e2e
 # suites on a Ubicloud runner. The actual recipe lives in the reusable
-# wasm-build.yml (the SINGLE build definition) — this is just the main/PR caller,
-# pinned to -O1 for fast feedback. The tag release (release.yml) calls the same
-# recipe at -O2 (the shipped demo opt level) and then publishes, so the build can
-# never diverge from what ships.
+# wasm-build.yml (the SINGLE build definition) — this is just the main/PR caller.
+# The asyncify wasm-opt tail is -O1 everywhere (main, release, local); the tag
+# release (release.yml) calls the same recipe at the same -O1 and then publishes,
+# so the build can never diverge from what ships.
 #
 # Routine edits under scripts/ do NOT bust the WASM output cache — only the subset
 # in scripts/deploy/wasm-cache-hash.mjs does. For inputs the sc-hash can't see
@@ -36,8 +36,8 @@ jobs:
   build:
     uses: ./.github/workflows/wasm-build.yml
     with:
-      # -O1: faster asyncify shrink, sufficient for the test gate (the demo ships
-      # -O2 via release.yml). 3D viewer ON so 3d-viewer.spec.ts has a viewer.
+      # -O1 asyncify shrink — the level we ship (release.yml uses the same -O1).
+      # 3D viewer ON so 3d-viewer.spec.ts has a viewer.
       opt_level: "-O1"
       build_3d_viewer: "ON"
       run_tests: true
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 6a8cf72..f64ea16 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -1,10 +1,11 @@
 name: release
 
 # Release pipeline on a vX.Y.Z tag, in order:
-#   1) build  — the SAME wasm-build.yml recipe as CI, but at -O2 (the shipped demo
-#               opt level) + run the e2e gate; reuses main's opt-independent base
-#               cache so only the asyncify/-O2 tail rebuilds. Uploads output/.
-#   2) publish-wasm — push the -O2 build to the CDN (content-addressed, idempotent)
+#   1) build  — the SAME wasm-build.yml recipe as CI, at the SAME -O1 asyncify tail
+#               + run the e2e gate. Because the opt level now matches main, this
+#               FINAL-cache-hits main's build and skips the asyncify tail rebuild.
+#               Uploads output/.
+#   2) publish-wasm — push the build to the CDN (content-addressed, idempotent)
 #               and write manifest-<tag>.json. The registry now reflects THIS tag.
 #   3) deploy-demo  — build the standalone pinned to that manifest + deploy to
 #               demo.pcbjam.com. So the demo can never point at stale wasm.
@@ -49,17 +50,18 @@ jobs:
       - id: tag
         run: echo "tag=${{ github.event.inputs.tag || github.ref_name }}" >> "$GITHUB_OUTPUT"
 
-  # 1) Build at -O2 (shipped) + e2e gate, reusing main's base cache. Uploads the
-  #    publishable output/ as the 'wasm-output' artifact for the publish job.
+  # 1) Build (-O1, identical to main) + e2e gate. Reuses main's FINAL cache (same
+  #    opt level) so the asyncify tail isn't rebuilt. Uploads the publishable
+  #    output/ as the 'wasm-output' artifact for the publish job.
   build:
     uses: ./.github/workflows/wasm-build.yml
     with:
-      opt_level: "-O2"
+      opt_level: "-O1"
       build_3d_viewer: "ON"
       run_tests: true
       upload_output: true
 
-  # 2) Publish the -O2 build to the CDN (content-addressed; unchanged tools reuse)
+  # 2) Publish the build to the CDN (content-addressed; unchanged tools reuse)
   #    and write manifest-<tag>.json. Cheap runner — just downloads + uploads.
   publish-wasm:
     needs: [meta, build]
diff --git a/.github/workflows/wasm-build.yml b/.github/workflows/wasm-build.yml
index 2d854e4..4de7685 100644
--- a/.github/workflows/wasm-build.yml
+++ b/.github/workflows/wasm-build.yml
@@ -1,27 +1,29 @@
 name: wasm-build (reusable)
 
-# THE single KiCad WASM build+test recipe, called by ci-ubicloud.yml (main/PR,
-# -O1 for fast feedback) and release.yml (tag, -O2 for the shipped demo). There
-# is no other build definition — publishing/deploy consume this job's output, so
-# the build can never diverge from what ships (the bug that shipped a -O1 / 3D-off
-# demo while CI built -O1 / 3D-on).
+# THE single KiCad WASM build+test recipe, called by ci-ubicloud.yml (main/PR) and
+# release.yml (tag). Both build the SAME way — the asyncify `wasm-opt` tail is -O1
+# everywhere — so the build can never diverge from what ships (the bug that shipped
+# a -O1 / 3D-off demo while CI built -O1 / 3D-on). The opt_level input remains as an
+# escape hatch for a one-off -O2 build, but is -O1 for both real callers, so a tag
+# release FINAL-cache-hits main's build and skips the asyncify tail entirely.
 #
 # Two-tier output cache around docker/build.sh's --compile-only / --postprocess-only
-# split. -O1 and -O2 differ ONLY in the final `wasm-opt -O` shrink; everything
-# before (docker compile → base wasm → asyncify instrument) is identical. So:
-#   - BASE cache  (opt-INDEPENDENT key): the --compile-only output (base wasm +
-#     sysroot headers). Warmed by main's -O1 CI; an -O2 release restores it and
-#     skips the expensive compile, running only the asyncify/-O2 tail.
-#   - FINAL cache (opt-SPECIFIC key): the post-processed output; fast-path for
-#     re-running the same opt+SHA (e.g. a re-deploy).
-# Both keys now include the 3D-viewer flag, so a 3D-on and 3D-off build can never
+# split. The expensive container compile (→ base wasm) is opt- and binaryen-
+# independent; only the host `asyncify + wasm-opt -O` tail depends on the binaryen
+# fork + opt level. So:
+#   - BASE cache  (compile-input key): the --compile-only output (base wasm +
+#     sysroot headers). Reused whenever only the binaryen fork / asyncify config
+#     changed — the compile is skipped and just the tail reruns.
+#   - FINAL cache (base + binaryen SHA + opt level): the post-processed output;
+#     fast-path for re-running the same SHA (a tag release reusing main, a re-deploy).
+# Both keys include the 3D-viewer flag, so a 3D-on and 3D-off build can never
 # poison each other's cache.
 
 on:
   workflow_call:
     inputs:
       opt_level:
-        description: "Binaryen wasm-opt shrink level for the asyncify tail (-O1 fast / -O2 shipped)"
+        description: "Binaryen wasm-opt shrink level for the asyncify tail (-O1 everywhere; escape hatch for a one-off -O2)"
         type: string
         default: "-O1"
       build_3d_viewer:
diff --git a/docker/build.sh b/docker/build.sh
index a0b7857..55f567f 100755
--- a/docker/build.sh
+++ b/docker/build.sh
@@ -22,15 +22,15 @@
 #
 # The build is split into two phases:
 # 1. Docker: Compile KiCad to WASM (without asyncify)
-# 2. Host: dyncall shims + finalize + asyncify + -O2 (Binaryen submodule via build-wasm-opt.sh)
+# 2. Host: dyncall shims + finalize + asyncify + wasm-opt -O1 (Binaryen submodule via build-wasm-opt.sh)
 #
 # KICAD_PIPELINE=1 (multi-app builds only): run phase 2 of each app in the
 # background while the next app compiles in the container. wasm-opt is
 # Amdahl-capped at ~4 effective cores, so on a many-core CI box the container
 # would otherwise sit idle for the 1-2h of host-side wasm-opt (run 27226030304:
 # 103 min of the 4h was tools serialized behind each other's wasm-opt). At most
-# KICAD_PIPELINE_JOBS (default 2) postprocesses run concurrently — pcbnew's -O2
-# peaks ~34 GB RSS, so 2 fits the 128 GB CI box but NOT a dev Mac: leave
+# KICAD_PIPELINE_JOBS (default 2) postprocesses run concurrently — pcbnew's wasm-opt
+# pass peaks ~34 GB RSS, so 2 fits the 128 GB CI box but NOT a dev Mac: leave
 # KICAD_PIPELINE unset locally.
 #
 # Binaryen is downloaded automatically - no prerequisites needed.
@@ -118,7 +118,7 @@ echo "Building app: ${APP_NAME}"
 # Build phase (cache split). The container compile produces an OPT-INDEPENDENT
 # base wasm; the only opt-DEPENDENT work is the final `wasm-opt -O$LEVEL` shrink
 # inside the host post-process (apply-asyncify.sh). Splitting them lets CI cache
-# the expensive compile once (shared across -O1/-O2) and re-run just the
+# the expensive compile once (shared regardless of the asyncify tail) and re-run just the
 # asyncify/-O tail per opt level — see .github/workflows/.
 #   (default) both       — compile in-container, then host post-process.
 #   --compile-only       — only the in-container compile → base wasm in output/.
@@ -248,7 +248,7 @@ compile_app() {
 }
 
 # Phase 2 of one app: host-side post-processing (dyncall shims, finalize,
-# asyncify + -O2). Pure host work on output/${app}.* — independent of the
+# asyncify + wasm-opt -O1). Pure host work on output/${app}.* — independent of the
 # container, which is what makes it safe to run in the background while the
 # next app compiles.
 postprocess_app() {
@@ -280,7 +280,7 @@ postprocess_app() {
     # Apply asyncify transformation on host. The converter is a synchronous node
     # CLI built with ASYNCIFY=0, so asyncify is unnecessary and would be wrong.
     # apply-asyncify always runs the --hoist-cpp-catches pass FIRST (native wasm-EH is the only build
-    # mode) so Asyncify can suspend from inside C++ catch arms, then asyncify + removelist + -O2.
+    # mode) so Asyncify can suspend from inside C++ catch arms, then asyncify + removelist + wasm-opt -O1.
     if [ "$app" != "sym_convert" ]; then
         kw_stage asyncify
         ./scripts/common/apply-asyncify.sh "${out_dir}/${app}.wasm" "${out_dir}/${app}.wasm"
@@ -304,7 +304,7 @@ pipeline_running_count() {
 }
 
 # Launch postprocess_app in the background, capped at KICAD_PIPELINE_JOBS
-# concurrent jobs (default 2: pcbnew's -O2 peaks ~34 GB RSS; two postprocesses
+# concurrent jobs (default 2: pcbnew's wasm-opt pass peaks ~34 GB RSS; two postprocesses
 # plus the container compile fit the 128 GB CI box). Portable poll loop instead
 # of `wait -n` (absent in macOS bash 3.2).
 pipeline_postprocess() {
diff --git a/scripts/common/apply-asyncify.sh b/scripts/common/apply-asyncify.sh
index a015d2d..e800111 100755
--- a/scripts/common/apply-asyncify.sh
+++ b/scripts/common/apply-asyncify.sh
@@ -128,9 +128,10 @@ fi
 
 # 3. Post-asyncify shrink. Asyncify spills every live local; without coalescing, large
 # coroutine-entry functions exceed V8's per-function locals limit and stall/crash the renderer.
-# -O1 already runs CoalesceLocals and suffices (CI uses it); -O2 is the default. NOT -Os/-Oz
-# (they break the asyncify runtime — Binaryen #4484). See docs/debugging/DEBUG.md §6-7.
-BINARYEN_OPT_LEVEL="${BINARYEN_OPT_LEVEL:--O2}"
+# -O1 runs CoalesceLocals (enough to keep instrumented functions under V8's local limit) and is the
+# level we ship EVERYWHERE — main CI, tag releases, and local builds all use it. NOT -Os/-Oz (they
+# break the asyncify runtime — Binaryen #4484). See docs/debugging/DEBUG.md §6-7.
+BINARYEN_OPT_LEVEL="${BINARYEN_OPT_LEVEL:--O1}"
 echo "Running wasm-opt ${BINARYEN_OPT_LEVEL} (shrink instrumented functions under V8's local limit)..."
 "${PRELOAD_CMD[@]}" "${TIME_CMD[@]}" "${WASM_OPT}" "${BINARYEN_OPT_LEVEL}" "${FEAT[@]}" ${G} "${OUTPUT_WASM}" -o "${OUTPUT_WASM}"