diff --git a/changelog.d/200.md b/changelog.d/200.md
index 16add90..52ca386 100644
--- a/changelog.d/200.md
+++ b/changelog.d/200.md
@@ -27,9 +27,10 @@
 - `.upstream-ref` records the upstream commit this tree carries, in
   machine-readable form beside the CHANGELOG's prose (#200).
 
-- `test/upstream-delta.test.sh` fails the PR that scatters forge branching into
-  a file the inventory does not name — across shell, workflows, `labels.conf`
-  and `drills/`, not shell alone (#200).
+- `test/upstream-delta.test.sh` fails the PR that scatters a forge decision
+  into a file the inventory does not name. Discovery is derived from the tree,
+  so a composite `action.yml` or a `.yaml` workflow is seen without anyone
+  remembering to add a glob (#200).
 
 - It refuses when the recorded commit is missing, absent from the object store,
   or not an ancestor — three distinct refusals, none of them a skip. `ci.yml`
diff --git a/docs/UPSTREAM-SYNC.md b/docs/UPSTREAM-SYNC.md
index 8377e42..e111fe3 100644
--- a/docs/UPSTREAM-SYNC.md
+++ b/docs/UPSTREAM-SYNC.md
@@ -227,6 +227,20 @@ Forge-specific behaviour is confined to the files below. Keeping it there is
 what makes each sync cost 18 hunks instead of hundreds, and
 `test/upstream-delta.test.sh` fails the PR that scatters it into a new file.
 
+**What that guard actually checks**, stated precisely so the table is not read
+as a stronger promise than it is: it walks every tracked file except prose
+(`*.md`), the test harness and `changelog.d/`, and flags any that **decides**
+the forge — the selector's verbs, `CEREMONY_FORGE*`, or a server-URL comparison
+written inline. Discovery is derived from the tree rather than from a list of
+directories and extensions, so a composite `action.yml` or a `.yaml` workflow
+is seen without anyone remembering to add it.
+
+It is a check on *forge decisions in executable and configuration files*. It is
+**not** a diff against upstream, so it cannot see a file that differs from
+upstream for some other forge-specific reason — `drills/` and
+`.github/labels.conf` are in the table for that kind of reason and are listed
+by judgement, not by scan.
+
 | file | what is forge-specific about it |
 |---|---|
 | `lib/forge.sh` | the selector: `forge_detect`, `forge_client`, `forge_preflight` |
diff --git a/test/upstream-delta.test.sh b/test/upstream-delta.test.sh
index 4299f38..a9a1c96 100644
--- a/test/upstream-delta.test.sh
+++ b/test/upstream-delta.test.sh
@@ -110,17 +110,43 @@ FORGE_MARKERS='forge_detect|forge_select|forge_preflight|forge_client|CEREMONY_F
 # invoked no_unlisted — the guard could have been `return 0` and still passed.
 scan_root() { printf '%s' "${SCAN_ROOT:-$ROOT}"; }
 
+# DISCOVERY IS DERIVED FROM THE TREE, not from a list of directories, depths
+# and extensions. The earlier version hand-picked five globs and therefore
+# could not see `actions/*/action.yml` — this repository's normal composite
+# structure, where a client declaration is exactly a forge decision — or a
+# workflow written `.yaml` rather than `.yml`. @codex-reviewer-andresmgsl
+# constructed both and the guard stayed 21/21 green, which is the whole
+# argument against maintaining a glob list.
+#
+# So: walk everything, then EXCLUDE by class, and let content classify the
+# rest. Excluding is safer than including because a new file type arrives
+# scanned rather than invisible.
+#
+#   .git/         not source
+#   test/         the harness stubs and asserts these tokens by design
+#   changelog.d/  prose fragments
+#   *.md          prose. `drills/` stays in the INVENTORY because its records
+#                 are forge-specific by content, but a record mentioning a
+#                 selector verb in prose is not a decision, and scanning prose
+#                 for decisions is the mistake this guard's own comment
+#                 handling exists to avoid.
+scanned_paths() {
+  local root; root="$(scan_root)"
+  find "$root" -type f \
+    -not -path "$root/.git/*" \
+    -not -path "$root/test/*" \
+    -not -path "$root/changelog.d/*" \
+    -not -name '*.md' \
+    2>/dev/null | sed "s|^$root/||" | sort
+}
+
 forge_specific_files() {
-  local root f rel
-  root="$(scan_root)"
-  for f in "$root"/lib/*.sh "$root"/actions/*/*.sh "$root"/bin/* \
-           "$root"/.github/scripts/*.sh "$root"/.github/workflows/*.yml \
-           "$root"/.github/labels.conf "$root"/drills/*.md; do
-    [ -f "$f" ] || continue
-    rel="${f#"$root"/}"
-    sed 's/[[:space:]]#.*$//; s/^[[:space:]]*#.*$//' "$f" \
+  local root rel; root="$(scan_root)"
+  while IFS= read -r rel; do
+    [ -n "$rel" ] || continue
+    sed 's/[[:space:]]#.*$//; s/^[[:space:]]*#.*$//' "$root/$rel" 2>/dev/null \
       | grep -qE "$FORGE_MARKERS" && printf '%s\n' "$rel"
-  done
+  done < <(scanned_paths)
   return 0
 }
 
@@ -211,6 +237,30 @@ check "a new WORKFLOW deciding the forge fails it too" 1 "" scattered_workflow
 check "...naming that file" 1 ".github/workflows/scattered.yml" scattered_workflow
 rm -f "$root/.github/workflows/scattered.yml"
 
+# @codex-reviewer-andresmgsl's two reproductions, verbatim as fixtures. Both
+# passed the hand-picked-glob version 21/21, which is why discovery is derived
+# from the tree now. Deleting a discovery class must make these red.
+mkdir -p "$root/actions/unlisted-forge-decision"
+printf '%s\n' 'name: x' 'runs:' '  using: composite' '  steps:' \
+  '    - shell: bash' '      env:' '        CEREMONY_FORGE_CLIENT: gh' \
+  '      run: true' >"$root/actions/unlisted-forge-decision/action.yml"
+composite_action_seen() { SCAN_ROOT="$root" no_unlisted; }
+check "a forge declaration in actions/*/action.yml fails the guard" 1 \
+  "actions/unlisted-forge-decision/action.yml" composite_action_seen
+rm -rf "$root/actions/unlisted-forge-decision"
+
+# ...and a workflow written .yaml rather than .yml — `*.yml` was never a
+# complete workflow surface.
+# shellcheck disable=SC2016 # fixture CONTENT: the literal text a scanned file would hold
+printf '%s\n' 'name: x' 'on: [push]' 'jobs:' '  j:' \
+  "    if: github.server_url == 'https://github.com'" '    steps: []' \
+  >"$root/.github/workflows/unlisted-forge-decision.yaml"
+yaml_workflow_seen() { SCAN_ROOT="$root" no_unlisted; }
+check "...and one in a .yaml workflow does too" 1 \
+  ".github/workflows/unlisted-forge-decision.yaml" yaml_workflow_seen
+rm -f "$root/.github/workflows/unlisted-forge-decision.yaml"
+check "...leaving the fixture tree green again" 0 "" clean_tree_passes
+
 # A declaration is a delta location even in a file that would otherwise read as
 # a shim consumer, so the consumer allow-list cannot hide one.
 mkdir -p "$root/lib"