Build boxes: the engine gate (igneumd and igneum-miner fetched by build-remote must carry igneum-pow/src/ paths; a commit string alone does not prove the engine: the stub-engine 21d8f454 that rejected every block on the Devnet 3 hub, 7 Oct 2026); tools/ci/engine-check.sh with its self-test in the gate

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

tools/build-remote.sh

@@ -255,6 +255,9 @@ if [ "$FETCH" = 1 ] && [ -n "$ARTEFACTS" ]; then
     bs_log "artefact $dest: $(bs_size "$dest") bytes, sha256 $(bs_sha256 "$dest"), $(file -b "$dest" | cut -c1-60)"
     # the commit-string gate (rule of 6 October 2026): a node binary without its commit in its strings fails the run
     case "$BS_KIND:$(basename "$dest")" in node:igneumd) "$HERE/ci/commit-string-check.sh" "$dest" "$BS_SHA" || bs_die "commit-string gate failed for $a" ;; esac   # only kaspad depends on kaspa-build-info
+    # the engine gate (7 Oct 2026, the Devnet 3 start): igneumd and igneum-miner must carry igneum-pow/src/ paths; a commit string
+    # alone does not prove the engine (a stub-engine 21d8f454 rejected every mined block on the fleet's hub)
+    case "$BS_KIND:$(basename "$dest")" in node:igneumd|node:igneum-miner) [ "${IGNEUM_ALLOW_STUB:-}" = 1 ] || "$HERE/ci/engine-check.sh" "$dest" || bs_die "engine gate failed for $a (IGNEUM_ALLOW_STUB=1 to fetch a stub-engine binary on purpose)" ;; esac
     # the glibc ceiling of anything that ships (main, 7 Oct 2026): a seed or a rig refuses a binary needing more than 2.36
     if [ "$SHIP" = 1 ]; then "$HERE/ci/glibc-ceiling-check.sh" "$dest" "$GLIBC" || bs_die "glibc ceiling gate failed for $a"; fi
   done

tools/ci/engine-check.sh

@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+# The engine gate (7 October 2026, the Devnet 3 start): a 21d8f454 igneumd with its commit string twice but ZERO igneum-pow/src/
+# paths was placed in the artefact folder by a build outside the app tree; the fleet's hub ran it, the igneum-pow miner's blocks
+# were every one rejected (Reject(BlockInvalid)), the go stopped. The commit-string gate cannot see this: the string comes from the
+# fork's own git, the engine from the igneum-pow tree the build sat next to. So every igneumd and igneum-miner that
+# tools/build-remote.sh fetches must carry igneum-pow source paths in its strings (rustc embeds the panic locations of the engine
+# crate it compiled in: igneum-pow/src/...); none means the stub engine or a foreign igneum-pow, and the fetch refuses.
+#
+#   tools/ci/engine-check.sh <binary>              # exit 0 with the count, exit 1 "no igneum-pow/src/ path in <binary>"
+#   tools/ci/engine-check.sh --self-test           # a fixture with the paths passes, one without fails
+set -euo pipefail
+if [ "${1:-}" = --self-test ]; then
+  t=$(mktemp -d); trap 'rm -rf "$t"' EXIT
+  printf 'binary junk\0/srv/builds/x/igneum-pow/src/lib.rs\0more junk\0igneum-pow/src/lottery.rs\0' > "$t/good"
+  printf 'binary junk\0/srv/builds/x/consensus/pow/src/stub.rs\0commit 21d8f454\0' > "$t/bad"
+  "$0" "$t/good" >/dev/null || { echo "engine-check self-test: a binary WITH igneum-pow paths was refused"; exit 1; }
+  if "$0" "$t/bad" >/dev/null 2>&1; then echo "engine-check self-test: a binary WITHOUT igneum-pow paths passed"; exit 1; fi
+  echo "engine-check self-test: a binary with igneum-pow/src/ paths passes, one without is refused"; exit 0
+fi
+f="${1:-}"; [ -f "$f" ] || { echo "engine-check: no file '$f'" >&2; exit 2; }
+n=$(LC_ALL=C grep -a -c 'igneum-pow/src/' "$f" || true)
+if [ "${n:-0}" -gt 0 ]; then echo "engine-check: $(basename "$f") carries $n igneum-pow/src/ path line(s): the igneum-pow engine"; exit 0; fi
+echo "engine-check: no igneum-pow/src/ path in $(basename "$f"): the stub engine or a foreign igneum-pow tree (the commit string alone does not prove the engine; 7 Oct 2026 Devnet 3)" >&2
+exit 1

tools/ci/pre-push.sh

@@ -95,6 +95,7 @@ tree_checks() {
   run "pinned guest programs match their manifest"                             bash tools/ci/pinned-guests-check.sh
   run "root prover playbooks kill the GPU server and unlink its socket"        bash tools/ci/prover-socket-check.sh
   run "commit-string gate self-test"                                           bash tools/ci/commit-string-check.sh --self-test
+  run "engine gate self-test (igneumd and igneum-miner must carry igneum-pow/src/ paths)" bash tools/ci/engine-check.sh --self-test
   run "build server remote checkout self-test"                                 bash infra/build-server/remote-run.sh --self-test
   run "a slot holder keeps its own line for the whole run (the watcher-trust rule)" bash infra/build-server/remote-run.sh --self-test-keeper
   run "the remote checkout resets the mirror's tree before the branch checkout (the stale-overlay class)" bash -c 'bash tools/ci/mirror-reset-check.sh --self-test && bash tools/ci/mirror-reset-check.sh'