diff --git a/Dockerfile b/Dockerfile
index fc71fea..8726068 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,15 +1,26 @@
 FROM perl:5.42.2-slim-bookworm@sha256:49f4e5e7e2fc5b12e5fc9b5a0603d96502feb24b97babd1bdf42e3f1fc3ebc43
 
+# expect-dev - provides `unbuffer`
 RUN apt-get update && \
-    apt-get install -y curl npm expect-dev && \
-    apt-get purge --auto-remove -y && \
+    apt-get install -y --no-install-recommends expect-dev && \
     apt-get clean && \
     rm -rf /var/lib/apt/lists/*
 
-RUN npm install -g tap-parser
-
 WORKDIR /opt/test-runner
 COPY . .
-RUN curl -fsSL https://raw.githubusercontent.com/skaji/cpm/main/cpm | perl - install -g --cpanfile /opt/test-runner/cpanfile --snapshot /dev/null
+
+# Fetch the cpm installer (a single-file Perl script).
+ADD https://raw.githubusercontent.com/skaji/cpm/main/cpm /tmp/cpm
+
+# Build the CPAN deps. A C toolchain is needed to compile the XS modules, but it is
+# installed and purged within this single layer so the compiler doesn't bloat the
+# final image. The cpm build cache is removed too.
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends build-essential && \
+    perl /tmp/cpm install -g --cpanfile /opt/test-runner/cpanfile --snapshot /dev/null && \
+    apt-get purge -y build-essential && \
+    apt-get autoremove -y && \
+    apt-get clean && \
+    rm -rf "$HOME/.perl-cpm" /usr/share/doc /var/lib/apt/lists/* /tmp/*
 
 ENTRYPOINT ["/opt/test-runner/bin/run.sh"]
diff --git a/bin/run.sh b/bin/run.sh
index 03d7baa..cc16d33 100755
--- a/bin/run.sh
+++ b/bin/run.sh
@@ -45,7 +45,7 @@ else
     test_file="${input_dir}/${slug}.t"
 fi
 chmod +x $test_file
-TABLE_TERM_SIZE=120 HARNESS_ACTIVE=1 PERL5OPT='-MXXX=-global' unbuffer perl -I"${input_dir}/lib" -I"${input_dir}/local/lib/perl5" $test_file 2>&1 | tap-parser -j 0 > "${output_dir}/tap.json"
+TABLE_TERM_SIZE=120 HARNESS_ACTIVE=1 PERL5OPT='-MXXX=-global' unbuffer perl -I"${input_dir}/lib" -I"${input_dir}/local/lib/perl5" $test_file 2>&1 | perl "$(dirname "$0")/tap-to-json.pl" > "${output_dir}/tap.json"
 bin/transform-results.pl "${output_dir}/tap.json" "${results_file}" $test_file
 
 echo "${slug}: done"
diff --git a/bin/tap-to-json.pl b/bin/tap-to-json.pl
new file mode 100755
index 0000000..2ca7421
--- /dev/null
+++ b/bin/tap-to-json.pl
@@ -0,0 +1,88 @@
+#!/usr/bin/env perl
+
+# Drop-in replacement for `tap-parser -j 0` (the npm package), using only core Perl
+# (JSON::PP). Reads a TAP stream on STDIN and writes, to STDOUT, the JSON event array
+# that bin/transform-results.pl consumes:
+#
+#   ["assert",  {"ok": <bool>, "name": <str>}]        one per TAP test point
+#   ["comment", "# ...\n"]                             diagnostic (# ...) lines
+#   ["extra",   "...\n"]                               non-TAP output (errors, prints)
+#   ["bailout", "<reason>"]                            a `Bail out!` line
+#   ["complete",{"count":N,"ok":<bool>,
+#                "plan":{"end":<N|null>,"skipAll":<bool>}}]   emitted once at the end
+#
+# Only the fields transform-results.pl reads are emitted; version/plan lines are folded
+# into the trailing `complete` event exactly as the npm tap-parser reports them.
+
+use v5.36;
+use JSON::PP ();
+
+binmode STDIN,  ':encoding(UTF-8)';
+binmode STDOUT, ':encoding(UTF-8)';
+
+sub jbool { $_[0] ? JSON::PP::true : JSON::PP::false }
+
+my @events;
+my ($count, $failed, $bailed) = (0, 0, 0);
+my $plan_end;    # stays undef unless a `1..N` plan line is seen
+
+while (my $line = <STDIN>) {
+    if ($line =~ /^TAP version \d+/) {
+        # version is not consumed by transform-results.pl
+    }
+    elsif ($line =~ /^(\d+)\.\.(\d+)/) {
+        $plan_end = 0 + $2;    # reported via the `complete` event, not as its own event
+    }
+    elsif ($line =~ /^Bail out!\s*(.*?)\s*$/) {
+        $bailed = 1;
+        push @events, [ 'bailout', $1 ];
+    }
+    elsif ($line =~ /^(not )?ok\b[ \t]*[0-9]*(.*)$/) {
+        my $is_not = $1;
+        $failed++ if $is_not;
+        $count++;
+        my $name = $2 // '';
+        $name =~ s/^\s*-\s*//;                       # drop the "- " separator
+        $name =~ s/\s+#\s*(?:SKIP|TODO)\b.*$//i;     # drop a trailing TAP directive
+        $name =~ s/\s+$//;
+        push @events, [ 'assert', { ok => jbool(!$is_not), name => $name } ];
+    }
+    elsif ($line =~ /^\s*#/) {
+        push @events, [ 'comment', $line ];
+    }
+    elsif ($line =~ /^\s*$/) {
+        # blank lines produce no event (matches the npm tap-parser)
+    }
+    else {
+        push @events, [ 'extra', $line ];
+    }
+}
+
+# Reproduce how tap-parser fills in the plan for the `complete` event:
+#   - real `1..N` plan         -> end = N,    skipAll = false
+#   - no plan and no tests run -> end = 0,    skipAll = true   ("no tests found")
+#   - tests ran but no plan    -> end = null, skipAll = false  (e.g. died mid-run)
+my ($end, $skip_all);
+if (defined $plan_end) { ($end, $skip_all) = ($plan_end, 0); }
+elsif ($count == 0)    { ($end, $skip_all) = (0,         1); }
+else                   { ($end, $skip_all) = (undef,     0); }
+
+my $ok =
+      $bailed   ? 0
+    : $skip_all ? 1
+    : ($failed == 0 && (!defined $plan_end || $count == $plan_end)) ? 1
+    : 0;
+
+# tap-parser injects this diagnostic when the test count doesn't match the plan
+# (e.g. a test died before done_testing()), just before the `complete` event.
+if (defined $plan_end ? $count != $plan_end : $count > 0) {
+    my $plan_str = defined $plan_end ? $plan_end : 'null';
+    push @events, [ 'comment', "# test count($count) != plan($plan_str)\n" ];
+}
+
+push @events, [
+    'complete',
+    { count => $count, ok => jbool($ok), plan => { end => $end, skipAll => jbool($skip_all) } },
+];
+
+print JSON::PP->new->canonical->encode(\@events);