diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 77ab39e..69a8d57 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -2,7 +2,7 @@ name: Do the thing in CI
 
 on:
   push:
-    branches: ['master']
+    branches: ['master', 'max_rss']
 
   # Allows you to run this workflow manually from the Actions tab
   workflow_dispatch:
@@ -14,39 +14,39 @@ jobs:
       matrix:
         # do the slow ones first, to make the overall build quicker
         build:
-          # - 00 tcl
-          - 01 prolog
-          - 02 smalltalk
-          - 03 python3
-          - 04 julia
-          - 05 perl
-          - 06 cobol
-          - 07 haskell
-          - 08 ruby
-          - 09 forth
-          - 10 lua
-          - 11 php
-          - 12 erlang
-          - 13 crystal
-          - 14 scala
-          - 15 csharp
-          - 16 coffeescript
-          - 17 kotlin
-          - 18 java
-          - 19 deno
-          - 20 node
-          - 21 go
-          - 22 bun
-          - 23 fortran
-          - 24 rust
-          - 25 cpp-clang
-          - 26 cpp-gcc
-          - 27 c-clang
-          - 28 c-gcc
-          - 29 nim
-          - 30 pascal
-          - 31 zig
-          - 32 assembly
+          # - 00_tcl
+          - 01_prolog
+          - 02_smalltalk
+          - 03_python3
+          - 04_julia
+          - 05_perl
+          - 06_cobol
+          - 07_haskell
+          - 08_ruby
+          - 09_forth
+          - 10_lua
+          - 11_php
+          - 12_erlang
+          - 13_crystal
+          - 14_scala
+          - 15_csharp
+          - 16_coffeescript
+          - 17_kotlin
+          - 18_java
+          - 19_deno
+          - 20_node
+          - 21_go
+          - 22_bun
+          - 23_fortran
+          - 24_rust
+          - 25_cpp-clang
+          - 26_cpp-gcc
+          - 27_c-clang
+          - 28_c-gcc
+          - 29_nim
+          - 30_pascal
+          - 31_zig
+          - 32_assembly
     runs-on: ubuntu-latest
     container:
       image: acheronfail/count
@@ -55,14 +55,18 @@ jobs:
         uses: actions/checkout@v3
       # really github? why do you override $HOME?
       # https://github.com/actions/runner/issues/863
-      - run: 'echo HOME=/root >> $GITHUB_ENV'
+      - name: Setup environment
+        run: |
+          echo HOME=/root >> $GITHUB_ENV
+          WHAT=${{ matrix.build }}
+          echo WHAT=${WHAT##*_} >> $GITHUB_ENV
       # do the thing
-      - run: just test    ${{ matrix.build }}
-      - run: just measure ${{ matrix.build }}
+      - run: just test    ${WHAT}
+      - run: just measure ${WHAT}
       # report
       - uses: actions/upload-artifact@v3
         with:
-          path: 'results/${{ matrix.build }}.json'
+          path: 'results/${WHAT}.json'
 
   report:
     needs: ['run']
diff --git a/Dockerfile b/Dockerfile
index 78553c4..64a6d08 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,15 +1,16 @@
-FROM ubuntu:latest
+FROM ubuntu:23.04
 
 ENV DEBIAN_FRONTEND="noninteractive" TZ="Europe/London"
 
 RUN apt-get update && apt-get install -y \
-  bc build-essential clang coffeescript curl default-jdk default-jre erlang \
-  fp-compiler gdb lldb gforth gfortran git gnu-smalltalk gnucobol3 golang \
-  haskell-platform jq kotlin lua5.4 mono-complete moreutils nasm php ruby \
-  scala swi-prolog tar tcl unzip wget xz-utils \
+  bc build-essential clang curl default-jdk default-jre erlang fp-compiler gdb \
+  ghc lldb gforth gfortran git gnu-smalltalk gnucobol3 golang jq kotlin lua5.4 \
+  mono-complete moreutils nasm php ruby scala swi-prolog tar tcl unzip wget \
+  xz-utils \
   && apt-get clean
 RUN curl -fSL https://deb.nodesource.com/setup_lts.x | bash - \
-  && apt-get install -y nodejs
+  && apt-get install -y nodejs \
+  && npm install --global coffeescript
 
 RUN curl -fSL https://sh.rustup.rs | sh -s -- -y --default-toolchain stable
 ENV PATH="/root/.cargo/bin:$PATH"
@@ -28,7 +29,7 @@ ENV PATH="/root/.bun/bin:$PATH"
 RUN curl -fSL https://deno.land/x/install/install.sh | sh
 ENV PATH="/root/.deno/bin:$PATH"
 
-RUN curl -fSL https://crystal-lang.org/install.sh | bash
+RUN curl -fSL https://crystal-lang.org/install.sh | bash -s -- --version=1.11
 
 RUN curl -fSL https://nim-lang.org/choosenim/init.sh | sh -s -- -y
 ENV PATH="/root/.nimble/bin:$PATH"
@@ -40,4 +41,6 @@ RUN cd && curl -fSL "$(curl -fSL https://ziglang.org/download/index.json | jq -r
   && rm zig.tar.xz
 ENV PATH="/root/.zig:$PATH"
 
+RUN cargo install --git https://github.com/acheronfail/max_rss.git --rev fae12f9
+
 WORKDIR /var/count
diff --git a/justfile b/justfile
index 54c9863..f4e5bca 100644
--- a/justfile
+++ b/justfile
@@ -93,8 +93,8 @@ measure what:
     jq '. += {"size":"'"$(cat SIZE)"'"}' "$out" | sponge "$out"
   fi
 
-  gdb --command rss.gdb --args $(cat CMD) >/dev/null
-  jq '. += {"rss":'$(( $(rg -oPr '$1' 'Rss:\s*(\d+)' ./rss.txt) * 1024 ))'}' "$out" | sponge "$out"
+  max_rss $(cat CMD)
+  jq '. += {"rss":'$(jq '.max_rss' ./max_rss.json)'}' "$out" | sponge "$out"
 
 measure-all:
   #!/usr/bin/env bash