diff --git a/.github/workflows/build-solo-sim.yml b/.github/workflows/build-solo-sim.yml
index 72e35275..5c24200c 100644
--- a/.github/workflows/build-solo-sim.yml
+++ b/.github/workflows/build-solo-sim.yml
@@ -46,7 +46,17 @@ jobs:
             echo "emsdk 6.0.9 already cached"
           fi
 
+      - name: Resolve build version
+        run: |
+          if [ "$GITHUB_REF_TYPE" = "tag" ]; then
+            echo "BUILD_VERSION=${GITHUB_REF_NAME}" >> $GITHUB_ENV
+          else
+            echo "BUILD_VERSION=dev-$(git rev-parse --short HEAD)" >> $GITHUB_ENV
+          fi
+
       - name: Build companion WASM
+        env:
+          FIRMWARE_VERSION: ${{ env.BUILD_VERSION }}
         run: variants/sim/build_wasm.sh
 
       - name: Build repeater WASM
diff --git a/variants/sim/build_wasm.sh b/variants/sim/build_wasm.sh
index 73f801fc..8dc436ff 100755
--- a/variants/sim/build_wasm.sh
+++ b/variants/sim/build_wasm.sh
@@ -149,6 +149,15 @@ DEFINES=(
   -DUI_SENSORS_PAGE=1
 )
 
+# The on-device splash's "Solo <version>" bar shows FIRMWARE_VERSION. Without
+# it, MyMesh.h falls back to "dev-<compile date>" -- what the live demo showed
+# even for a tagged release. build-solo-sim.yml exports it (tag name for a
+# release, "dev-<commit>" otherwise), same as build-solo-firmwares.yml does
+# for the hardware builds; a local build with it unset keeps the old fallback.
+if [ -n "${FIRMWARE_VERSION:-}" ]; then
+  DEFINES+=("-DFIRMWARE_VERSION=\"${FIRMWARE_VERSION}\"")
+fi
+
 # -funsigned-char: carried over from Phase 1 verbatim -- real ARM cores
 # default `char` to unsigned; em++'s target (wasm32) defaults it to signed,
 # same mismatch Phase 1 hit on a native x86/ARM64 host, for the same reason