diff --git a/.github/workflows/ocaml-ci.yml b/.github/workflows/ocaml-ci.yml
index 9d9a87c..c90234b 100644
--- a/.github/workflows/ocaml-ci.yml
+++ b/.github/workflows/ocaml-ci.yml
@@ -29,10 +29,16 @@ on:
     branches: [main]
     paths:
       - 'compiler/**'
+      - 'examples/**'
+      - 'conformance/**'
+      - 'scripts/check-corpus.sh'
       - '.github/workflows/ocaml-ci.yml'
   pull_request:
     paths:
       - 'compiler/**'
+      - 'examples/**'
+      - 'conformance/**'
+      - 'scripts/check-corpus.sh'
       - '.github/workflows/ocaml-ci.yml'
   workflow_dispatch: {}
 
@@ -93,6 +99,15 @@ jobs:
           fi
           echo "OCaml compiler: build + all suites GREEN."
 
+      - name: Corpus gate (examples + conformance)
+        run: |
+          set -euo pipefail
+          # Runs the language's OWN programs. Neither examples/ nor conformance/
+          # was executed by anything before this, which is how
+          # examples/isotopy.tangle — the demonstration of the central claim —
+          # sat failing its own assertions until TG-7 (#87) fixed `~`.
+          bash scripts/check-corpus.sh
+
       - name: TG-7 semantics guard
         working-directory: compiler
         run: |
diff --git a/Justfile b/Justfile
index d59bd23..f4a648b 100644
--- a/Justfile
+++ b/Justfile
@@ -74,3 +74,13 @@ crg-badge:
 
 secret-scan-trufflehog:
     @command -v trufflehog >/dev/null && trufflehog filesystem . --only-verified || true
+
+# Run the language's own programs (examples/ + conformance/) — same gate as CI
+corpus:
+    @cd compiler && dune build
+    @bash scripts/check-corpus.sh
+
+# Compiler build + full test suite (4,000+ assertions) + the corpus gate.
+check-all:
+    @cd compiler && dune build && dune test --force
+    @bash scripts/check-corpus.sh
diff --git a/conformance/run_conformance.sh b/conformance/run_conformance.sh
index 6773809..c326014 100755
--- a/conformance/run_conformance.sh
+++ b/conformance/run_conformance.sh
@@ -17,9 +17,25 @@ if [[ -n "${1:-}" ]]; then
     # shellcheck disable=SC2206 # deliberate word-splitting of caller's string
     PARSER_CMD=(${1})
 else
-    PARSER_CMD=(dune exec --root "${SCRIPT_DIR}/../compiler" -- tangle --parse-only)
+    # The default used to be `dune exec -- tangle --parse-only`. BOTH halves were
+    # wrong: the executable is named `main` (compiler/bin/dune), not `tangle`, and
+    # there has never been a `--parse-only` flag — bare `<file>` is parse +
+    # pretty-print. So every invocation failed, which made this suite REPORT
+    # 3/19 while proving nothing: the three "passes" were invalid/ cases, and an
+    # invalid case "passes" precisely when the command fails. It failed for the
+    # wrong reason and scored a point for it.
+    #
+    # Prefer a pre-built binary (CI builds once); fall back to `dune exec`.
+    BIN="${SCRIPT_DIR}/../compiler/_build/default/bin/main.exe"
+    if [[ -x "${BIN}" ]]; then
+        PARSER_CMD=("${BIN}")
+    else
+        PARSER_CMD=(dune exec --root "${SCRIPT_DIR}/../compiler" -- ./bin/main.exe)
+    fi
 fi
 
+echo "parser: ${PARSER_CMD[*]}"
+
 PASS=0
 FAIL=0
 TOTAL=0
diff --git a/scripts/check-corpus.sh b/scripts/check-corpus.sh
new file mode 100755
index 0000000..0627332
--- /dev/null
+++ b/scripts/check-corpus.sh
@@ -0,0 +1,169 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: MPL-2.0
+# check-corpus.sh — gate the RUNNABLE corpus: examples/ and conformance/.
+#
+# ── Why this exists ────────────────────────────────────────────────────────
+# Neither examples/ nor conformance/ was executed by anything — not CI, not the
+# Justfile. The cost of that was concrete: `examples/isotopy.tangle`, the file
+# whose entire purpose is to demonstrate the language's central claim ("two
+# braids can be structurally different but topologically equivalent"), FAILED
+# with "Assertion failed" and had done for as long as `~` used free reduction.
+# It only began passing when TG-7 (#50/#87) made `~` decide real braid-group
+# equivalence. A showcase example can sit broken indefinitely if nothing runs it.
+#
+# ── Why a RATCHET rather than a pass/fail ──────────────────────────────────
+# Five example programs do not typecheck and five conformance `valid/` programs
+# do not parse. Those are real gaps (see below), not things to paper over — but
+# they also cannot be fixed in the change that introduces the gate. So each
+# known failure is recorded EXPLICITLY here with its cause. The gate then
+# enforces, in both directions:
+#
+#   * nothing currently working may break  (regression)
+#   * nothing may join the known-bad lists  (new debt)
+#   * anything that starts working MUST be removed from the list (the ratchet
+#     tightens — a stale entry is itself a failure)
+#
+# That last rule is what stops an "expected failures" list decaying into a
+# permanent excuse.
+#
+# USAGE:  scripts/check-corpus.sh [path-to-tangle-binary]
+# EXIT:   0 = corpus matches the manifest exactly; 1 = drift in either direction
+
+set -uo pipefail
+
+ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+BIN="${1:-${ROOT}/compiler/_build/default/bin/main.exe}"
+
+if [[ ! -x "${BIN}" ]]; then
+  echo "::error::tangle binary not found or not executable: ${BIN}"
+  echo "Build it first:  (cd compiler && dune build)"
+  exit 1
+fi
+
+# ── MANIFEST ───────────────────────────────────────────────────────────────
+# Examples that must fully TYPECHECK and EVALUATE (all their asserts hold).
+EXAMPLES_MUST_RUN=(
+  echo_pd.tangle
+  isotopy.tangle          # the TG-7 witness — see header
+)
+
+# Examples that PARSE but do not yet TYPECHECK. Cause is recorded per entry so
+# the list cannot quietly become a dumping ground. Tracked in #88.
+#   braids_as_data / trefoil : recursive fn returning Num — `1 + length(rest)`
+#                              infers the recursive call as Word[0], not Num
+#   compositional_pd / tensor_product : `identity == braid[...]` is a width
+#                              mismatch (Word[0] vs Word[n]) under T-Eq-Word
+#   turing_complete          : match arms disagree in width (Word[0] vs Word[2])
+EXAMPLES_KNOWN_UNTYPED=(
+  braids_as_data.tangle
+  compositional_pd.tangle
+  tensor_product.tangle
+  trefoil.tangle
+  turing_complete.tangle
+)
+
+# conformance/valid programs the parser does not yet accept. These specify
+# language surface that exists in the spec but not in parser.mly. Tracked in #88.
+#   v02/v08/v09/v12 : `weave strands a:Q, b:Q into (...) yield strands ...`
+#   v11             : `add{ ... }` blocks (JTV data injection)
+CONFORMANCE_KNOWN_UNPARSED=(
+  v02_weave.tangle
+  v08_crossing.tangle
+  v09_twist.tangle
+  v11_add_block.tangle
+  v12_weave_expr.tangle
+)
+
+fail=0
+note() { printf '  %-34s %s\n' "$1" "$2"; }
+
+in_list() { local n="$1"; shift; local x; for x in "$@"; do [[ "$x" == "$n" ]] && return 0; done; return 1; }
+
+# ── 1. Every example must PARSE. No exceptions: a file that cannot even parse
+#       is not documentation, it is a syntax error with a licence header.
+echo "== examples: parse =="
+for f in "${ROOT}"/examples/*.tangle; do
+  n="$(basename "$f")"
+  if "${BIN}" "$f" >/dev/null 2>&1; then note "$n" "parse ok"; else
+    note "$n" "PARSE FAILED"; echo "::error::${n} does not parse"; fail=1; fi
+done
+
+# ── 2. The working examples must keep typechecking AND evaluating.
+echo "== examples: typecheck + evaluate (must-run set) =="
+for n in "${EXAMPLES_MUST_RUN[@]}"; do
+  f="${ROOT}/examples/${n}"
+  if [[ ! -f "$f" ]]; then
+    echo "::error::manifest lists ${n} but the file is gone"; fail=1; continue; fi
+  if "${BIN}" --eval "$f" >/dev/null 2>&1; then note "$n" "eval ok"; else
+    note "$n" "EVAL FAILED"
+    echo "::error::${n} must evaluate cleanly (all asserts holding) and does not:"
+    "${BIN}" --eval "$f" 2>&1 | head -5
+    fail=1
+  fi
+done
+
+# ── 3. The known-untyped examples: still parse, still fail to typecheck.
+#       If one starts typechecking, the manifest is STALE and must be updated.
+echo "== examples: known-untyped (ratchet) =="
+for n in "${EXAMPLES_KNOWN_UNTYPED[@]}"; do
+  f="${ROOT}/examples/${n}"
+  if [[ ! -f "$f" ]]; then
+    echo "::error::manifest lists ${n} but the file is gone"; fail=1; continue; fi
+  if "${BIN}" --eval "$f" >/dev/null 2>&1; then
+    note "$n" "NOW WORKS"
+    echo "::error::${n} now evaluates — good! Move it to EXAMPLES_MUST_RUN and drop it from EXAMPLES_KNOWN_UNTYPED."
+    fail=1
+  else
+    note "$n" "still untyped (expected)"
+  fi
+done
+
+# ── 4. Any example NOT in either list is unaccounted for.
+echo "== examples: manifest covers every file =="
+for f in "${ROOT}"/examples/*.tangle; do
+  n="$(basename "$f")"
+  if ! in_list "$n" "${EXAMPLES_MUST_RUN[@]}" && ! in_list "$n" "${EXAMPLES_KNOWN_UNTYPED[@]}"; then
+    note "$n" "UNLISTED"
+    echo "::error::${n} is in examples/ but not in the manifest. Add it to EXAMPLES_MUST_RUN (preferred) or, with a recorded cause, EXAMPLES_KNOWN_UNTYPED."
+    fail=1
+  fi
+done
+
+# ── 5. Conformance: valid must parse (except the recorded set); invalid must NOT.
+echo "== conformance =="
+for f in "${ROOT}"/conformance/valid/*.tangle; do
+  n="$(basename "$f")"
+  if "${BIN}" "$f" >/dev/null 2>&1; then
+    if in_list "$n" "${CONFORMANCE_KNOWN_UNPARSED[@]}"; then
+      note "valid/$n" "NOW PARSES"
+      echo "::error::conformance/valid/${n} now parses — drop it from CONFORMANCE_KNOWN_UNPARSED."
+      fail=1
+    else
+      note "valid/$n" "parse ok"
+    fi
+  else
+    if in_list "$n" "${CONFORMANCE_KNOWN_UNPARSED[@]}"; then
+      note "valid/$n" "still unparsed (expected)"
+    else
+      note "valid/$n" "PARSE FAILED"
+      echo "::error::conformance/valid/${n} must parse and does not"; fail=1
+    fi
+  fi
+done
+for f in "${ROOT}"/conformance/invalid/*.tangle; do
+  n="$(basename "$f")"
+  if "${BIN}" "$f" >/dev/null 2>&1; then
+    note "invalid/$n" "PARSED (should not)"
+    echo "::error::conformance/invalid/${n} parsed successfully but is meant to be rejected"; fail=1
+  else
+    note "invalid/$n" "rejected ok"
+  fi
+done
+
+echo
+if [[ "$fail" -ne 0 ]]; then
+  echo "::error::corpus drifted from the manifest — see the errors above."
+  exit 1
+fi
+echo "Corpus matches the manifest: examples parse, the must-run set evaluates,"
+echo "known gaps are unchanged, and invalid programs are still rejected."