diff --git a/.github/workflows/validate.yml b/.github/workflows/validate.yml
index 0d3ae0ce..cfddd750 100644
--- a/.github/workflows/validate.yml
+++ b/.github/workflows/validate.yml
@@ -377,7 +377,27 @@ env:
   # as its floor, and tests/examples/mcpp-plugins builds against it. Engine
   # warnings the members may newly print: W1 to W3 of SPEC-008 (the library
   # interface), warnings only.
-  MCPP_VERSION: "2026.9.28.3"
+  #
+  # 2026.9.29.1 (mcpp-community/mcpp#738) builds a workspace as one graph per
+  # configuration: `mcpp test -p <member>` plans that member and what it
+  # reaches in the workspace's build directory, `target/<triple>/<key>/` at
+  # this repository's root, with the member's products in `bin/<name>/`. The
+  # members' own `tests/examples/*/target/` directories are no longer written.
+  # The directory name no longer hashes a package's own flags, so a member
+  # whose flags differ from another's shares the directory and ninja rebuilds
+  # the commands that changed.
+  #
+  # 2026.9.29.2 (mcpp-community/mcpp#739) reads what a member states about
+  # itself from the member: a member's own relative [indices].path is anchored
+  # at the member, a member whose tests import std is tested with the std
+  # module built, and a member's product directory holds every shared library
+  # of its closure. 2026.9.29.1 is not used here: its sweep refused the 47
+  # members that declare their own [indices].
+  #
+  # 2026.9.29.3 (mcpp-community/mcpp#740): a program a member ships through
+  # `artifacts` waits for no plan-level runtime file, and its own runtime
+  # files are placed beside it in the member's product directory.
+  MCPP_VERSION: "2026.9.29.3"
 
 jobs:
   lint:
diff --git a/.gitignore b/.gitignore
index 772af0bf..9f58afa2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,10 @@
 .xlings-index-cache.json
+# The workspace's build directory, project data, compile database and lock:
+# mcpp 2026.9.29.1+ writes them at the workspace root for every member.
+/target/
+/.mcpp/
+/compile_commands.json
+/mcpp.lock
 # example project build/fetch artifacts
 tests/examples/*/target/
 tests/examples/*/.mcpp/
diff --git a/index.toml b/index.toml
index 3feb98ba..6f3da6a9 100644
--- a/index.toml
+++ b/index.toml
@@ -126,7 +126,15 @@
 # registers mcpp.plugins 0.17.0, whose package floor it is. The release changes
 # no descriptor grammar; its `[package] mcpp` key is manifest vocabulary, which
 # an older engine reports as unsupported and ignores.
+# ── 2026-09-29: latest_mcpp -> 2026.9.29.3, min_mcpp unchanged ─────────────
+#
+# Moved in the pull request that moves validate.yml's pin to 2026.9.29.3,
+# which runs every member on every platform with it. 2026.9.29.1 is skipped:
+# it resolved a member's own relative [indices].path against the workspace
+# root; 2026.9.29.2 is the version the full sweep ran with, and 2026.9.29.3
+# adds the runtime placement of programs shipped through `artifacts`. None of
+# the three changes descriptor grammar.
 [index]
 spec        = "1"
 min_mcpp    = "2026.9.18.3"
-latest_mcpp = "2026.9.28.3"
+latest_mcpp = "2026.9.29.3"
diff --git a/tests/check_graphics_install_side_effects.sh b/tests/check_graphics_install_side_effects.sh
index 9e9ebabd..5fee79ac 100755
--- a/tests/check_graphics_install_side_effects.sh
+++ b/tests/check_graphics_install_side_effects.sh
@@ -81,11 +81,15 @@ describe() {
 # which is the failure that would actually invalidate the comparison.
 build_and_describe() {
     ( cd "$PROJ" && "$MCPP" test ) > "$1" 2>&1 || true
-    local bin
-    bin=$(find "$PROJ/target" -type f -path '*/bin/*' -perm -u+x 2>/dev/null \
-          | head -1)
+    # mcpp 2026.9.29.1+ builds a workspace at its root: a member's programs
+    # are in `bin/<package name>/` of the workspace's build directory, and
+    # the member's own directory holds no build.
+    local pkg bin
+    pkg=$(sed -n 's/^name *= *"\(.*\)".*/\1/p' "$PROJ/mcpp.toml" | head -1)
+    bin=$(find "$ROOT/target" -type f -path "*/bin/$pkg/*" ! -name '*.so*' \
+               -perm -u+x 2>/dev/null | head -1)
     [[ -n "$bin" ]] || {
-        echo "no artifact produced under $PROJ/target:" >&2
+        echo "no artifact produced under $ROOT/target/*/*/bin/$pkg:" >&2
         tail -25 "$1" >&2; return 1; }
     describe "$bin"
 }
@@ -161,7 +165,7 @@ this check installs into.
 
   Installing the graphics stack into one home and measuring artifacts from
   another compares two unrelated things, and the comparison passes for any
-  mcpp. Clean the member's target/ (or use a checkout that has none) so the
+  mcpp. Clean the workspace's target/ (or use a checkout that has none) so the
   build actually resolves through MCPP_HOME.
 MSG
         exit 1 ;;