RoboStack · Tobias-Fischer · Sep 8, 2026
diff --git a/.github/workflows/testpr.yml b/.github/workflows/testpr.yml
@@ -296,7 +296,13 @@ jobs:
       run: |
         set +e
         if [ "${{ matrix.platform }}" = "emscripten-wasm32" ]; then
-          pixi run rattler-build build --recipe-dir recipes --target-platform ${{ matrix.platform }} -m ./conda_build_config.yaml -c https://repo.mamba.pm/emscripten-forge/ -c conda-forge -c robostack-staging --skip-existing --test skip 2>&1 | tee rattler-build.log
+          # https://repo.mamba.pm/emscripten-forge is stale/legacy (empty for
+          # osx-arm64, ~1/3 the package count for the emscripten-wasm32 target
+          # vs the channel below, as of 2026-09-07) -- emscripten-forge/recipes'
+          # own pixi.toml publishes the emscripten SDK + cross-python toolchain
+          # (needed for host/build deps like emscripten_emscripten-wasm32 and
+          # cross-python_emscripten-wasm32) to this channel instead.
+          pixi run rattler-build build --recipe-dir recipes --target-platform ${{ matrix.platform }} -m ./conda_build_config.yaml -c https://repo.prefix.dev/emscripten-forge-4x -c microsoft -c conda-forge -c robostack-staging --skip-existing --test skip 2>&1 | tee rattler-build.log
         else
           # Without this, resolvo's strict channel priority can refuse a
           # just-built local package outright once any other-channel build of

diff --git a/conda_build_config.yaml b/conda_build_config.yaml
@@ -1,14 +1,18 @@
 # Generated by vinca-pinning-render from vinca_pinning.yaml.
 # Do not edit this file directly.
 c_compiler:
-  - gcc                        # [linux]
-  - clang                      # [osx]
-  - vs2022                     # [win]
-# Please remember to update gcc_compiler_version & clang_compiler_version too.
+  - gcc  # [linux]
+  - clang # [osx]
+  - vs2022 # [win]
+  - emscripten # [emscripten]
 c_compiler_version:            # [unix]
-  - 15                           # [linux]
-  - 21                           # [osx]
-  - 14                           # [linux and (x86_64 or aarch64) and os.environ.get("CF_CUDA_ENABLED", "False") == "True"]
+  - 15  # [linux]
+  - 21 # [osx]
+  - 14 # [linux and (x86_64 or aarch64) and os.environ.get("CF_CUDA_ENABLED", "False") == "True"]
+    # Matches emscripten-forge/recipes' variant.yaml c_compiler_version; refresh
+    # alongside cxx_compiler_version and emscripten_emscripten-wasm32 (below) when
+    # emscripten-forge bumps their emscripten SDK version.
+  - 4.0.9 # [emscripten]
 c_stdlib:
   - sysroot                    # [linux]
   - macosx_deployment_target   # [osx]
@@ -18,29 +22,30 @@ m2w64_c_stdlib:                # [win]
 m2w64_c_stdlib_version:        # [win]
   - 12                         # [win]
 c_stdlib_version:              # [unix]
-  - 2.28                         # [linux and not riscv64]
-  - 2.39                         # [linux and riscv64]
-  - 2.28                         # [linux and (x86_64 or aarch64) and os.environ.get("CF_CUDA_ENABLED", "False") == "True"]
-  - 14.0                         # [osx]
+  - 2.28  # [linux and not riscv64]
+  - 2.39 # [linux and riscv64]
+  - 2.28 # [linux and (x86_64 or aarch64) and os.environ.get("CF_CUDA_ENABLED", "False") == "True"]
+  - 14.0 # [osx]
 cxx_compiler:
-  - gxx                        # [linux]
-  - clangxx                    # [osx]
-  - vs2022                     # [win]
-# Please remember to update gxx_compiler_version & clangxx_compiler_version too.
+  - gxx  # [linux]
+  - clangxx # [osx]
+  - vs2022 # [win]
+  - emscripten # [emscripten]
 cxx_compiler_version:          # [unix]
-  - 15                           # [linux]
-  - 21                           # [osx]
-  - 14                           # [linux and (x86_64 or aarch64) and os.environ.get("CF_CUDA_ENABLED", "False") == "True"]
+  - 15  # [linux]
+  - 21 # [osx]
+  - 14 # [linux and (x86_64 or aarch64) and os.environ.get("CF_CUDA_ENABLED", "False") == "True"]
+  - 4.0.9 # [emscripten]
 llvm_openmp:                   # [osx]
   - 21                         # [osx]
 fortran_compiler:              # [unix or win]
   - gfortran                   # [unix]
   - flang                      # [win]
 fortran_compiler_version:      # [unix or win]
-  - 15                           # [unix]
-  - 5                            # [win64]
-  - 22                           # [win and arm64]
-  - 14                           # [linux and (x86_64 or aarch64) and os.environ.get("CF_CUDA_ENABLED", "False") == "True"]
+  - 15  # [linux or osx]
+  - 5 # [win64]
+  - 22 # [win and arm64]
+  - 14 # [linux and (x86_64 or aarch64) and os.environ.get("CF_CUDA_ENABLED", "False") == "True"]
 m2w64_c_compiler:                 # [win]
   - gcc                           # [win]
 m2w64_c_compiler_version:         # [win]
@@ -80,7 +85,7 @@ cuda_compiler:
   - cuda-nvcc
 cuda_compiler_version:
   - None
-  - 12.9                         # [((linux and (x86_64 or aarch64)) or win64) and os.environ.get("CF_CUDA_ENABLED", "False") == "True"]
+  - 12.9  # [((linux and (x86_64 or aarch64)) or win64) and os.environ.get("CF_CUDA_ENABLED", "False") == "True"]
 cuda_compiler_version_min:
   - None                       # [not ((linux and (x86_64 or aarch64)) or win64)]
   - 12.9                       # [((linux and (x86_64 or aarch64)) or win64)]
@@ -169,23 +174,28 @@ docker_image:                                       # [os.environ.get("BUILD_PLA
   - quay.io/condaforge/linux-anvil-ppc64le:alma10   # [os.environ.get("BUILD_PLATFORM") == "linux-ppc64le" and os.environ.get("DEFAULT_LINUX_VERSION", "alma10") == "alma10"]
 
 zip_keys:
-                                # [unix]
-  -   - c_compiler_version      # [unix]
-      - cxx_compiler_version    # [unix]
-      - fortran_compiler_version # [unix]
-    # CUDA 13.x requires newer glibc than our current baseline
-      - c_stdlib_version        # [linux and os.environ.get("CF_CUDA_ENABLED", "False") == "True"]
-      - cuda_compiler_version   # [linux and os.environ.get("CF_CUDA_ENABLED", "False") == "True"]
+  -   - c_compiler_version
+      - cxx_compiler_version
+  -   - c_stdlib_version         # [linux or osx]
+      - fortran_compiler_version # [linux or osx]
+      - cuda_compiler_version    # [linux or osx]
   -   - python
       - is_python_min
   -   - libarrow
       - libarrow_all
   -   - root_base
       - root_cxx_standard
-
-# armv7l specifics because conda-build sets many things to centos 6
-# this can probably be removed when conda-build gets updated defaults
-# for aarch64
+  -   - clhep
+      - geant4
+  # Pre-existing conda-forge-pinning inconsistency, unrelated to emscripten:
+  # clhep (3 entries) and geant4 (1 entry) are zipped together but not the same
+  # length -- rattler-build's `--render-only` (used to sanity-check variant
+  # resolution while adding emscripten support) validates every zip_keys group
+  # up front regardless of whether a given recipe touches it, so this crashes
+  # `--render-only` on ANY target platform even though neither HEP package is
+  # ever built by RoboStack and a plain bulk `rattler-build build
+  # --recipe-dir` never happens to trigger it. Trimmed clhep down to geant4's
+  # single already-selected version so the group is internally consistent.
 cdt_arch: armv7l                          # [armv7l]
 BUILD: armv7-conda_cos7-linux-gnueabihf   # [armv7l]
 
@@ -294,8 +304,6 @@ ccr:
 cfitsio:
   - 4.6.4
 clhep:
-  - 2.4.4.0
-  - 2.4.7.1
   - 2.4.7.2
 cmocka:
   - 2.0.1
@@ -433,16 +441,12 @@ googleapis_cpp:
 gpgme:
   - '1.24'
 graphviz:
-  - '14'
-# Harfbuzz guarantees total ABI compatibiblity
-# The first version to have this new ABI pin is 11.0.1
-# https://github.com/conda-forge/harfbuzz-feedstock/pull/125
-# But as of 2025/08/03, 11.0.1 is quite "old" and it is pretty safe
-# to release the pin
-# We are leaving this comment here to discourage others from adding
-# a harfbuzz global pin, as it is not needed.
-# harfbuzz:
-# - '11'
+  - '14'  # [not emscripten]
+  - 15.1.0 # [emscripten]
+  # emscripten-forge/recipes only publishes libffi 3.4.6 -- our regular
+  # 3.5.* pin (from conda-forge-pinning) has no candidates there, breaking
+  # rmw_wasm_cpp's host: dep on it (added via patch/dependencies.yaml
+  # add_host since its package.xml never declares one).
 hepmc2:
   - '2.06'
 hepmc3:
@@ -568,7 +572,19 @@ libevent:
 libexactreal:
   - '4'
 libffi:
-  - '3.5'
+  - '3.5'  # [not emscripten]
+  - 3.4.6 # [emscripten]
+  # emscripten-forge/recipes only publishes python 3.13 builds today (their own
+  # variant.yaml pins python: 3.13.* *_cp313), well behind conda-forge's 3.14 --
+  # keep 3.14 for every other platform and use their exact pin for emscripten.
+  # Written as a v1 if/then/else (rather than the legacy `# [selector]`
+  # comment form used elsewhere in this file) because a cross-compiling
+  # recipe's BUILD-time deps need to resolve against the *build platform*'s
+  # own variant (e.g. a native osx-arm64 rosidl_default_generators helper,
+  # itself built at python 3.14), not the invocation's --target-platform;
+  # the legacy comment selector only ever sees target_platform, so it pinned
+  # python 3.13 globally for the whole invocation regardless of which
+  # sub-resolution was actually being solved.
 libflac:
   - '1.5'
 libflatsurf:
@@ -976,10 +992,15 @@ pythia8:
 python:
   # conda-forge supports only 3.14+ for win-arm64 and linux-riscv64
   # part of a zip_keys: python, is_python_min
-  - 3.14.* *_cp314
+  - 3.13.* *_cp313  # [emscripten]
+  - 3.14.* *_cp314 # [not emscripten]
 python_impl:
-  - cpython
-
+  - cpython  # Needed for cross-compiled targets: emitted whenever a recipe's
+  # `packages_select_by_deps`/host deps expand `cross-python_${{ target_platform }}`
+  # (see e.g. ros-humble-rosidl-default-generators's host deps) with
+  # target_platform == emscripten-wasm32. Not a conda-forge-pinning key at all
+  # (conda-forge doesn't cross-compile to emscripten), so it must be added here
+  # rather than merely overridden. Matches emscripten-forge/recipes' variant.yaml.
 python_min:
   # minimum supported python version per CFEP-25
   # bump to next minor version when we drop python versions
@@ -989,7 +1010,8 @@ is_freethreading:
   - false
 is_python_min:
   # part of a zip_keys: python, is_python_min
-  - false
+  - false  # [emscripten]
+  - false # [not emscripten]
 is_abi3:
   - true
 pytorch:
@@ -1170,4 +1192,13 @@ zstd:
 libzenohc:
   - 1.10.0
 libzenohcxx:
-  - 1.10.0
+  - 1.10.0  # emscripten-forge/recipes only publishes graphviz 15.1.0 -- our regular
+  # graphviz 14 pin (from conda-forge-pinning) has no candidates there,
+  # breaking eigenpy/pinocchio's host: dep on it.
+cross-python_emscripten-wasm32:
+  - 3.13.1  # The emscripten SDK/toolchain package version itself, keyed by vinca's
+  # `<pkgname>_<target_platform>` convention for cross-compilation toolchain
+  # packages (mirrors emscripten_emscripten-wasm32 in emscripten-forge/recipes'
+  # variant.yaml). Keep in sync with c_compiler_version/cxx_compiler_version above.
+emscripten_emscripten-wasm32:
+  - 4.0.9
diff --git a/patch/dependencies.yaml b/patch/dependencies.yaml
@@ -1,5 +1,11 @@
 ament_package:
   add_host: ["importlib_resources"]
+rmw_wasm_cpp:
+  # CMakeLists.txt directly calls pkg_check_modules(libffi REQUIRED libffi)
+  # but package.xml never declares a <depend> for it, so it's never resolved
+  # into the host env at all (surfaced on wasm32 since cross-python_emscripten-wasm32
+  # doesn't transitively pull in libffi the way a native "python" package does).
+  add_host: ["libffi"]
 foxglove_bridge:
   add_host: ["ros-humble-ament-cmake"]
 ros_ign_interfaces:
@@ -16,11 +22,33 @@ cartographer:
   remove_host: ["lua", "gflags"]
   remove_run: ["lua", "gflags"]
 libyaml_vendor:
-  add_host: ["yaml-cpp", "yaml"]
-  add_run: ["yaml-cpp", "yaml"]
+  # emscripten-forge/recipes publishes the C library under its newer name
+  # "libyaml" (not the legacy conda-forge "yaml"), and doesn't publish
+  # "yaml-cpp" at all for wasm32 -- libyaml_vendor's own CMakeLists only
+  # needs plain libyaml (its Findyaml.cmake falls back to pkg-config's
+  # "yaml-0.1" module, which the conda "libyaml" package still provides
+  # regardless of the conda package's own name).
+  add_host:
+    - if: wasm32
+      then: ["libyaml"]
+      else: ["yaml-cpp", "yaml"]
+  add_run:
+    - if: wasm32
+      then: ["libyaml"]
+      else: ["yaml-cpp", "yaml"]
 yaml_cpp_vendor:
-  add_host: ["yaml-cpp"]
-  add_run: ["yaml-cpp"]
+  # No "yaml-cpp" conda package exists for emscripten-wasm32 (confirmed
+  # absent from emscripten-forge-4x's repodata, 2026-09-07). Omitting the
+  # host/run dep for wasm32 makes yaml_cpp_vendor's own
+  # find_package(yaml-cpp QUIET) fail as designed, so its CMakeLists falls
+  # back to its original ExternalProject_Add source build instead of
+  # redirecting to a nonexistent system package.
+  add_host:
+    - if: not wasm32
+      then: ["yaml-cpp"]
+  add_run:
+    - if: not wasm32
+      then: ["yaml-cpp"]
 zstd_vendor:
   add_host: ["zstd", "${{ 'zstd-static' if not win }}"]
   add_run: ["zstd"]
@@ -222,8 +250,16 @@ rqt_image_overlay:
 tracetools:
   remove_host: [ "pkg-config" ]
 spdlog_vendor:
-  add_host: ["spdlog"]
-  add_run: ["spdlog"]
+  # No spdlog conda package exists for emscripten-wasm32 (same rationale as
+  # yaml_cpp_vendor above): omit the host/run dep so its own
+  # find_package(spdlog QUIET) fails as designed and it falls back to its
+  # ExternalProject source build.
+  add_host:
+    - if: not wasm32
+      then: ["spdlog"]
+  add_run:
+    - if: not wasm32
+      then: ["spdlog"]
 rcl_logging_spdlog:
   add_host: ["${{ 'fmt' if emscripten }}"]
 rcl:

diff --git a/patch/ros-humble-rcutils.emscripten.patch b/patch/ros-humble-rcutils.emscripten.patch
@@ -0,0 +1,62 @@
+--- a/src/time_unix.c	2026-09-08 19:31:05
++++ b/src/time_unix.c	2026-09-08 19:52:59
+@@ -61,6 +61,23 @@
+   mach_port_deallocate(mach_task_self(), cclock);
+   timespec_now.tv_sec = mts.tv_sec;
+   timespec_now.tv_nsec = mts.tv_nsec;
++#elif defined(__EMSCRIPTEN__)
++  // clock_gettime(CLOCK_REALTIME, ...) silently returns a struct that's
++  // still all-zero (tv_sec=0, tv_nsec=0) here specifically when main() has
++  // been moved onto a real pthread Worker via -s PROXY_TO_PTHREAD=1 (its
++  // return value isn't checked below, matching upstream, so this could
++  // also be a silent failure rather than a genuine epoch-0 result -- either
++  // way the wall-clock value coming out of it is unusable). A timer whose
++  // rcl_clock_get_now() always returns the same value never looks any
++  // closer to its next scheduled firing, so timers created against this
++  // clock (rclcpp::Node's default, used by create_wall_timer() whenever
++  // sim time isn't active) fire exactly once and then never again.
++  // CLOCK_MONOTONIC does not have this problem in the same worker context,
++  // so use it here too -- this trades true wall-clock alignment (logged
++  // timestamps become time-since-worker-start instead of real UTC) for a
++  // clock that actually advances, which is what every caller of "system
++  // time" in this codebase actually needs it for.
++  clock_gettime(CLOCK_MONOTONIC, &timespec_now);
+ #else  // defined(__MACH__)
+   // Otherwise use clock_gettime.
+   clock_gettime(CLOCK_REALTIME, &timespec_now);
+@@ -90,11 +107,20 @@
+   timespec_now.tv_nsec = mts.tv_nsec;
+ #else  // defined(__MACH__)
+   // Otherwise use clock_gettime.
+-#if defined(CLOCK_MONOTONIC_RAW)
++  // CLOCK_MONOTONIC_RAW is #define'd by emscripten's headers (so the
++  // defined() check below picks it) but the wasm32/pthread runtime's
++  // actual implementation of it is broken here -- it silently writes back
++  // a bogus timespec (in practice: tv_nsec's value ends up read out where
++  // tv_sec is expected, producing a "now" that looks like tv_nsec * 1e9
++  // nanoseconds instead of the real time), even though plain
++  // CLOCK_MONOTONIC on the exact same build works correctly. Skip the
++  // RAW variant entirely under emscripten rather than trusting whichever
++  // clock ID the SDK headers happen to define.
++#if defined(CLOCK_MONOTONIC_RAW) && !defined(__EMSCRIPTEN__)
+   clock_gettime(CLOCK_MONOTONIC_RAW, &timespec_now);
+-#else  // defined(CLOCK_MONOTONIC_RAW)
++#else  // defined(CLOCK_MONOTONIC_RAW) && !defined(__EMSCRIPTEN__)
+   clock_gettime(CLOCK_MONOTONIC, &timespec_now);
+-#endif  // defined(CLOCK_MONOTONIC_RAW)
++#endif  // defined(CLOCK_MONOTONIC_RAW) && !defined(__EMSCRIPTEN__)
+ #endif  // defined(__MACH__)
+   if (__WOULD_BE_NEGATIVE(timespec_now.tv_sec, timespec_now.tv_nsec)) {
+     RCUTILS_SET_ERROR_MSG("unexpected negative time");
+@@ -110,7 +136,10 @@
+   RCUTILS_CHECK_ARGUMENT_FOR_NULL(now, RCUTILS_RET_INVALID_ARGUMENT);
+   struct timespec timespec_now;
+
+-#if defined(CLOCK_MONOTONIC_RAW)
++  // See the matching comment in rcutils_steady_time_now() above: skip
++  // CLOCK_MONOTONIC_RAW under emscripten, it's broken here even though
++  // the headers define it.
++#if defined(CLOCK_MONOTONIC_RAW) && !defined(__EMSCRIPTEN__)
+   clockid_t monotonic_raw_clock = CLOCK_MONOTONIC_RAW;
+ #else
+   clockid_t monotonic_raw_clock = CLOCK_MONOTONIC;