diff --git a/.gitignore b/.gitignore
index 55e0cdb0..cdee4900 100644
--- a/.gitignore
+++ b/.gitignore
@@ -30,3 +30,9 @@ frontier_wave1.json
 # are committed; the renders are not.
 evals/audit_passed/
 evals/expert_demos/
+
+# ADR-0119.7 — GSM8K sealed-holdout discipline. Only the encrypted
+# .age file may be tracked; plaintext companions must never land in git.
+evals/gsm8k_math/holdouts/v1/cases.jsonl
+evals/gsm8k_math/holdouts/v1/cases_plaintext.jsonl
+evals/gsm8k_math/holdouts/v1/cases-train*
diff --git a/docs/decisions/ADR-0119.7-sealed-gsm8k-test.md b/docs/decisions/ADR-0119.7-sealed-gsm8k-test.md
new file mode 100644
index 00000000..abbc10b0
--- /dev/null
+++ b/docs/decisions/ADR-0119.7-sealed-gsm8k-test.md
@@ -0,0 +1,229 @@
+# ADR-0119.7 — Sealed GSM8K Test Set as gsm8k_math Holdout
+
+**Status:** Accepted
+**Date:** 2026-05-23
+**Author:** CORE agents + reviewers
+**Depends on:** ADR-0105 (sealed holdout encryption), ADR-0114, ADR-0114a, ADR-0119, ADR-0119.1, ADR-0119.3
+
+---
+
+## Context
+
+Phase 5.7 of [ADR-0119](ADR-0119-gsm8k-eval-lane-roadmap.md). Closes
+the last substrate sub-phase before ADR-0120 (first `expert` promotion
+contract) becomes feasible.
+
+ADR-0114 §Phase 5 designated the real GSM8K test set as a **sealed
+holdout** — never read during development. This ADR ships that seal:
+the 1,319 GSM8K test cases are encrypted to the recipient established
+under ADR-0119.1 and live on disk at
+`evals/gsm8k_math/holdouts/v1/cases.jsonl.age`. Plaintext never
+touches disk; the seal is one-way until a release event signed by a
+reviewer opens the lane.
+
+This ADR also surfaces the **first honest measurement of CORE against
+real GSM8K**:
+
+| Cases | Correct | Wrong | Refused |
+|---|---|---|---|
+| 1,319 | 0 | 0 | 1,319 |
+
+The parser grammar covers zero GSM8K test problems today. That is
+the truthful gap. **`wrong == 0` discipline holds against the
+external corpus** — CORE refuses, never confabulates. ADR-0114a
+Obligation #4 holds without modification.
+
+---
+
+## Decision
+
+### Source
+
+Hugging Face `openai/gsm8k` (config `"main"`, `test` split, 1,319 rows).
+Loaded once at seal time via `datasets.load_dataset`. The plaintext is
+held in memory only during encryption — never written to disk in the
+working tree.
+
+### Schema (per case)
+
+```text
+id              "gsm8k-test-NNNN"  (zero-padded)
+problem         the GSM8K question, verbatim
+expected_answer the integer or float after "#### N" in the answer field
+                (commas stripped; e.g. "2,125" → 2125)
+expected_unit   ""  (sentinel — runner skips unit-comparison; gates on
+                     answer value alone)
+```
+
+GSM8K answers carry no unit (they're pure numbers), so the lane runner
+(ADR-0119.3) was extended in this PR with the rule:
+
+> "An empty `expected_unit` means the case carries no unit-level
+> expectation; the runner skips the unit comparison and grades on
+> answer value alone."
+
+This is a minimal extension to ADR-0119.3's outcome rules; the
+`wrong == 0` discipline is preserved.
+
+### Sealing
+
+`scripts/seal_gsm8k_test.py` performs the conversion + encryption:
+
+1. Loads GSM8K test split via `datasets`
+2. Strips the worked-solution portion of each answer; keeps only the
+   final numeric (after `####`)
+3. Builds the in-memory JSONL plaintext
+4. Reads the recipient key from `docs/holdout_recipients.txt`
+   (established under ADR-0119.1 — same recipient as fab_control;
+   single repo-level key)
+5. Encrypts via `pyrage` (X25519 age recipient)
+6. Writes the ciphertext to
+   `evals/gsm8k_math/holdouts/v1/cases.jsonl.age` (only the ciphertext
+   ever exists on disk)
+
+The script refuses to overwrite the test-seal path with a
+train-derived seal (`--split train` writes to a sibling path with a
+distinct name).
+
+### Seal discipline (per ADR-0119)
+
+The development team **MUST** operate blind to the sealed contents
+until a release event signed by a reviewer opens the lane:
+
+- The plaintext does not appear in the working tree
+- No CI workflow may set `CORE_HOLDOUT_KEY`
+- The recipient identity is stored OUTSIDE the repo (per
+  ADR-0119.1, at `~/.config/core/holdout_keys/repo_holdout.txt`)
+- Tests requiring decryption skip (not fail) without the env var
+- Re-encryption / re-seal events go through their own ADR amendment
+
+### First measurement on main
+
+Running the lane runner (ADR-0119.3) against the sealed file
+(decrypted under `CORE_HOLDOUT_KEY`):
+
+```text
+cases_total: 1319
+correct:     0
+wrong:       0
+refused:     1319
+correct_rate: 0.0
+wrong_rate:   0.0
+refused_rate: 1.0
+wrong_count_is_zero: True
+overall_pass: True
+```
+
+**This is the load-bearing first number.** It says exactly how far
+CORE's grammar is from GSM8K coverage. ADR-0120 (first `expert`
+promotion contract) will require a minimum `correct_rate` — and that
+threshold will tell us how much parser expansion is required before
+the lane can promote `mathematics_logic` to `expert`.
+
+---
+
+## ADR-0114a obligation roll-up after Phase 5.7
+
+| # | Obligation | Status |
+|---|---|---|
+| 1 | Sealed-holdout discipline | ✓ fab_control (0119.1) + **gsm8k_math (this ADR)** |
+| 2 | OOD surface variation | ✓ ADR-0118a |
+| 3 | Replay-equal trace | ✓ ADR-0117 |
+| 4 | Typed refusal + wrong==0 | ✓ ADR-0116 + 0119.3; **holds against real GSM8K** |
+| 5 | Reasoning-isolation perturbation suite | ✓ ADR-0125 |
+| 6 | Compositional-depth curve harness | ✓ ADR-0119.6 |
+| 7 | Frontier-baseline comparison | ✓ ADR-0119.4 |
+| 8 | Adversarial generation; wrong==0 | ✓ ADR-0119.5 |
+| 9 | Determinism | ✓ |
+| 10 | Operation provenance via pack | ✓ ADR-0116 |
+
+**All 10 obligations now discharged on main for the gsm8k_math lane.**
+ADR-0120 can compose them into the first `expert` promotion contract.
+
+---
+
+## Invariants
+
+### `adr_0119_7_sealed_file_present_and_age_formatted`
+
+`evals/gsm8k_math/holdouts/v1/cases.jsonl.age` exists, is non-empty,
+and starts with the `age-encryption.org/` header.
+
+### `adr_0119_7_no_plaintext_companion_files`
+
+No sibling plaintext files (`cases.jsonl`, `cases_plaintext.jsonl`,
+`cases-train.jsonl`, etc.) exist in the holdout directory. The seal
+is one-way: only ciphertext on disk.
+
+### `adr_0119_7_seal_decrypts_to_documented_schema`
+
+Decrypting with the registered identity yields ≥ 1,000 cases, each
+matching the documented schema (id, problem, expected_answer,
+expected_unit=="").
+
+### `adr_0119_7_runner_holds_wrong_zero_against_real_gsm8k`
+
+Running the lane runner against the decrypted sealed file produces
+`wrong == 0`. CORE refuses what it cannot grammar-handle; it does
+not confabulate. ADR-0114a Obligation #4 holds against the external
+corpus.
+
+### `adr_0119_7_skip_without_key`
+
+Tests that require decryption SKIP (do not fail) when
+`CORE_HOLDOUT_KEY` is unset. Matches ADR-0105 dev-mode discipline;
+CI runs do not need the key.
+
+---
+
+## Acceptance evidence
+
+- `evals/gsm8k_math/holdouts/v1/cases.jsonl.age` (420,486 bytes)
+  encrypted to the ADR-0119.1 recipient
+- `scripts/seal_gsm8k_test.py` reproduces the seal from
+  `datasets.load_dataset("openai/gsm8k", "main")["test"]`
+- `evals/gsm8k_math/runner.py` extended with empty-unit
+  semantics: empty `expected_unit` skips unit-comparison
+- `tests/test_adr_0119_7_sealed_gsm8k.py` (6 cases) green with
+  `CORE_HOLDOUT_KEY` set; 3 pass + 3 skip without
+- First measurement recorded above
+- ADR linked from `docs/decisions/README.md`
+
+---
+
+## Consequences
+
+- **Phase 5 is now substrate-complete.** All 8 sub-phases (5.1..5.8)
+  have landed or are in flight; the only remaining piece for ADR-0120
+  is the numeric threshold-setting work (depth-curve ε, minimum
+  correct_rate, etc.) — that's a single ADR's job, not a multi-phase
+  arc.
+- **The first honest CORE-vs-real-GSM8K number is on the books.**
+  0/1319 correct is a real measurement, not a placeholder. Future
+  parser-expansion work has a concrete target — every lift moves
+  that number.
+- **`wrong == 0` is now a discharged invariant against an external
+  test set.** A future parser regression that introduces
+  confabulation will be caught by ADR-0119.7's runner-against-sealed
+  test — the lane gate refuses the regression at promotion time.
+- **The seal is one-way under standard operation.** No CI workflow
+  reads `CORE_HOLDOUT_KEY`; only an explicit release event (with
+  the env var set) decrypts the test. The standard development loop
+  stays blind to the contents.
+
+---
+
+## Out of scope
+
+- The `expert` ledger tier definition and promotion contract
+  (ADR-0120) — composes ADR-0114a obligations with numeric thresholds.
+- Parser-grammar expansion to handle rate/comparison/percentage GSM8K
+  problems. Future ADR(s); each expansion is its own scope-bounded
+  unit.
+- A second sealed corpus (e.g. MATH, AIME) — would be a new lane
+  under a future ADR.
+- Multi-reviewer threshold signing (currently single-recipient seal;
+  open candidate frontier item from ADR-0105).
+- Auto-re-sealing on dataset updates. The current ADR seals one
+  snapshot; if GSM8K is updated upstream a future re-seal ADR
+  documents the change.
diff --git a/docs/decisions/README.md b/docs/decisions/README.md
index d6c54c7f..6fe7a30c 100644
--- a/docs/decisions/README.md
+++ b/docs/decisions/README.md
@@ -53,6 +53,7 @@ ADRs record significant architectural decisions: what was decided, why, what alt
 | [ADR-0119.4](ADR-0119.4-frontier-baseline-comparison.md) | GSM8K Math: Frontier-Baseline Comparison (ADR-0114a §Obligation #7) | Accepted (2026-05-22) |
 | [ADR-0119.5](ADR-0119.5-adversarial-generation.md) | GSM8K Math Adversarial Generation (ADR-0114a Obligation #8) | Accepted (2026-05-23) |
 | [ADR-0119.6](ADR-0119.6-depth-curve-harness.md) | GSM8K Math Depth-Curve Measurement Harness | Accepted (2026-05-23) |
+| [ADR-0119.7](ADR-0119.7-sealed-gsm8k-test.md) | Sealed GSM8K Test Set as gsm8k_math Holdout | Accepted (2026-05-23) |
 | [ADR-0119.8](ADR-0119.8-lane-gate.md) | gsm8k_math Overall Lane Gate (`gsm8k_capability_shape`) | Accepted (2026-05-23) |
 
 ---
@@ -101,6 +102,7 @@ The ADR-0091..0114 slate is fully accepted (0091..0113) plus one proposed-roadma
 - gsm8k_math Lane Runner (Phase 5.3; correct/wrong/refused triple; wrong==0 gate; current: 200/200 correct on dev+public) — ADR-0119.3
 - GSM8K Math: Frontier-Baseline Comparison (citations for Claude 3.5, GPT-4, Gemini 1.5; comparison_v1.json; discharges ADR-0114a §Obligation #7) — ADR-0119.4
 - GSM8K Math Depth-Curve Measurement Harness (discharges ADR-0114a Obligation #6 measurement-side) — ADR-0119.6
+- Sealed GSM8K Test Set (1,319 cases age-encrypted; one-way seal; first honest CORE-vs-real-GSM8K measurement: 0/1319 correct, **0 wrong** — ADR-0114a Obligation #4 holds against external corpus) — ADR-0119.7
 - GSM8K Math Adversarial Generation (38 cases × 12 families; **closes ADR-0114a Obligation #8**; misparse rate 0/38; 10 of 10 obligations now discharged on main) — ADR-0119.5
 - gsm8k_math Overall Lane Gate (Phase 5.8; new `gsm8k_capability_shape` in `LANE_SHAPE_REGISTRY`; composes wrong==0 + correct+refused==total + overall_pass; live dev 50/50 + public 150/150 pass) — ADR-0119.8
 
diff --git a/evals/gsm8k_math/holdouts/v1/cases.jsonl b/evals/gsm8k_math/holdouts/v1/cases.jsonl
deleted file mode 100644
index e69de29b..00000000
diff --git a/evals/gsm8k_math/holdouts/v1/cases.jsonl.age b/evals/gsm8k_math/holdouts/v1/cases.jsonl.age
new file mode 100644
index 00000000..fbf9cc6c
Binary files /dev/null and b/evals/gsm8k_math/holdouts/v1/cases.jsonl.age differ
diff --git a/evals/gsm8k_math/holdouts/v1/cases_plaintext.jsonl b/evals/gsm8k_math/holdouts/v1/cases_plaintext.jsonl
deleted file mode 100644
index e69de29b..00000000
diff --git a/evals/gsm8k_math/runner.py b/evals/gsm8k_math/runner.py
index f485c48e..5b94cb76 100644
--- a/evals/gsm8k_math/runner.py
+++ b/evals/gsm8k_math/runner.py
@@ -154,8 +154,13 @@ def _score_one(case: dict[str, Any]) -> CaseOutcome:
             realized_prose=None,
         )
 
-    # Stage 5 — compare against expected
-    if trace.answer_unit != expected_unit:
+    # Stage 5 — compare against expected.
+    # An empty expected_unit ("") means the case carries no unit-level
+    # expectation (e.g. the sealed GSM8K test set under ADR-0119.7
+    # records pure-number answers without a parsed unit). In that case
+    # the runner skips the unit comparison and grades on answer value
+    # alone. Cases that DO specify expected_unit get the strict check.
+    if expected_unit != "" and trace.answer_unit != expected_unit:
         return CaseOutcome(
             case_id=case_id,
             outcome="wrong",
diff --git a/pyproject.toml b/pyproject.toml
index 4e0a5201..7e8b10f9 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -14,6 +14,7 @@ dependencies = [
     "pyrage==1.2.3",
     "pyyaml>=6.0",
     "ruff>=0.15.12",
+    "datasets>=4.8.5",
 ]
 
 [project.optional-dependencies]
diff --git a/scripts/seal_gsm8k_test.py b/scripts/seal_gsm8k_test.py
new file mode 100644
index 00000000..b267b7c3
--- /dev/null
+++ b/scripts/seal_gsm8k_test.py
@@ -0,0 +1,241 @@
+"""ADR-0119.7 — seal the real GSM8K test set as the gsm8k_math holdout.
+
+Loads the GSM8K test split via Hugging Face ``datasets``, converts each
+row to the lane-runner JSONL schema (id / problem / expected_answer /
+expected_unit), and encrypts the result against the recipient key
+registered in ``docs/holdout_recipients.txt``.
+
+The plaintext never lands on disk — it's held in memory only during
+encryption. The final artifact is
+``evals/gsm8k_math/holdouts/v1/cases.jsonl.age``.
+
+Per ADR-0119 §5.7 the seal is one-way: development MUST operate blind
+to the test contents until a release event signed-by-reviewer opens
+the lane.
+
+Usage:
+
+    uv run python scripts/seal_gsm8k_test.py [--split test|train] \\
+        [--recipient <age recipient string>]
+
+The default split is ``test``. Use ``--split train --limit N`` to
+seal a small chunk of train for sanity-check purposes (does NOT
+overwrite the real test seal).
+"""
+
+from __future__ import annotations
+
+import argparse
+import json
+import re
+import sys
+from pathlib import Path
+
+_REPO_ROOT = Path(__file__).resolve().parent.parent
+_RECIPIENTS_FILE = _REPO_ROOT / "docs" / "holdout_recipients.txt"
+_GSM8K_SEAL_PATH = _REPO_ROOT / "evals" / "gsm8k_math" / "holdouts" / "v1" / "cases.jsonl.age"
+
+
+# GSM8K answer pattern: each `answer` field ends with "#### N" where N is the
+# final numeric answer. Numbers may be integers, decimals, or carry thousands
+# separators (commas) like "2,125".
+_GSM8K_FINAL_ANSWER_RE = re.compile(r"####\s*(-?[\d,]+(?:\.\d+)?)\s*$")
+
+
+def _extract_answer(answer_text: str) -> float:
+    """Pull the final numeric answer from a GSM8K answer string.
+
+    Strips comma thousands-separators. Raises ValueError if the
+    "#### N" marker is absent.
+    """
+    match = _GSM8K_FINAL_ANSWER_RE.search(answer_text)
+    if not match:
+        raise ValueError(
+            f"no '#### N' final-answer marker in answer text: "
+            f"{answer_text[-80:]!r}"
+        )
+    raw = match.group(1).replace(",", "")
+    if "." not in raw:
+        return int(raw)
+    return float(raw)
+
+
+def _convert_to_lane_schema(
+    rows: list[dict], prefix: str
+) -> list[dict]:
+    """Convert GSM8K rows → lane-runner case dicts.
+
+    Each case carries:
+        id              — "{prefix}-{i:04d}" (deterministic ordering)
+        problem         — the GSM8K question, verbatim
+        expected_answer — the integer (or float) after "####"
+        expected_unit   — "" (sentinel; runner skips unit check)
+
+    No ground_truth_graph is emitted — GSM8K problems generally require
+    rate/comparison reasoning the ADR-0115 parser does not handle, so
+    most cases will refuse rather than parse. That's the expected
+    behavior; the wrong-count discipline is preserved by the runner.
+    """
+    cases: list[dict] = []
+    for i, row in enumerate(rows, start=1):
+        question = row["question"]
+        answer = row["answer"]
+        try:
+            expected_answer = _extract_answer(answer)
+        except ValueError as exc:
+            raise ValueError(f"case {prefix}-{i:04d}: {exc}") from exc
+        cases.append({
+            "id": f"{prefix}-{i:04d}",
+            "problem": question,
+            "expected_answer": expected_answer,
+            "expected_unit": "",
+        })
+    return cases
+
+
+def _load_recipient() -> str:
+    """Read the recipient public key from docs/holdout_recipients.txt.
+
+    Format (per ADR-0119.1):
+        # <comment lines>
+        fabrication_control: age1xxx...
+
+    For ADR-0119.7 we use the SAME recipient as fabrication_control
+    by default (single key per repo). A future amendment could split
+    per-lane keys if needed.
+    """
+    if not _RECIPIENTS_FILE.exists():
+        raise FileNotFoundError(
+            f"recipients file missing: {_RECIPIENTS_FILE}. "
+            "Run ADR-0119.1 first to establish the keypair."
+        )
+    text = _RECIPIENTS_FILE.read_text(encoding="utf-8")
+    for line in text.splitlines():
+        line = line.strip()
+        if line.startswith("#") or not line:
+            continue
+        # "lane_name: age1xxx" or just "age1xxx"
+        if ":" in line:
+            _, _, value = line.partition(":")
+            value = value.strip()
+        else:
+            value = line
+        if value.startswith("age1"):
+            return value
+    raise ValueError(
+        f"no age1... recipient key found in {_RECIPIENTS_FILE}"
+    )
+
+
+def _encrypt_to_age(plaintext: bytes, recipient_str: str) -> bytes:
+    """Encrypt plaintext bytes to age ciphertext under the recipient."""
+    try:
+        import pyrage
+        from pyrage.x25519 import Recipient
+    except ImportError as exc:
+        raise RuntimeError(
+            "pyrage not installed; required for ADR-0119.7 sealing"
+        ) from exc
+    recipient = Recipient.from_str(recipient_str)
+    return pyrage.encrypt(plaintext, [recipient])
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(
+        description="Seal the GSM8K test set as the gsm8k_math holdout"
+    )
+    parser.add_argument(
+        "--split",
+        default="test",
+        choices=["test", "train"],
+        help="GSM8K split to seal (default: test). Use 'train' for "
+             "sanity-check sealing; never overwrites the test seal.",
+    )
+    parser.add_argument(
+        "--limit",
+        type=int,
+        default=None,
+        help="Limit the number of rows sealed (for sanity-check runs)",
+    )
+    parser.add_argument(
+        "--output",
+        type=Path,
+        default=None,
+        help="Override the output path (default: "
+             "evals/gsm8k_math/holdouts/v1/cases.jsonl.age for test split; "
+             "a sibling path for train)",
+    )
+    parser.add_argument(
+        "--recipient",
+        default=None,
+        help="age recipient string (default: read from "
+             "docs/holdout_recipients.txt)",
+    )
+    args = parser.parse_args()
+
+    try:
+        from datasets import load_dataset  # type: ignore[import-not-found]
+    except ImportError:
+        print(
+            "datasets package not installed. Run: uv add datasets",
+            file=sys.stderr,
+        )
+        return 2
+
+    # Resolve output path
+    if args.output is not None:
+        output_path = args.output
+    elif args.split == "test":
+        output_path = _GSM8K_SEAL_PATH
+    else:
+        # Sanity-check sealing of train → distinct path
+        suffix = f"-train{f'-limit{args.limit}' if args.limit else ''}"
+        output_path = _GSM8K_SEAL_PATH.with_name(
+            f"cases{suffix}.jsonl.age"
+        )
+
+    # Refuse to overwrite the test seal accidentally
+    if (
+        args.split == "train"
+        and output_path == _GSM8K_SEAL_PATH
+    ):
+        print(
+            f"refusing to write a train-derived seal to the test path "
+            f"{output_path}; use --output to override",
+            file=sys.stderr,
+        )
+        return 2
+
+    recipient_str = args.recipient or _load_recipient()
+    print(f"recipient: {recipient_str}", file=sys.stderr)
+
+    print(f"loading GSM8K {args.split} split...", file=sys.stderr)
+    ds = load_dataset("openai/gsm8k", "main")
+    rows = list(ds[args.split])
+    if args.limit is not None:
+        rows = rows[:args.limit]
+    print(f"loaded {len(rows)} rows", file=sys.stderr)
+
+    prefix = f"gsm8k-{args.split}"
+    cases = _convert_to_lane_schema(rows, prefix=prefix)
+    print(f"converted to {len(cases)} lane-schema cases", file=sys.stderr)
+
+    plaintext = (
+        "\n".join(
+            json.dumps(c, sort_keys=True, separators=(",", ":")) for c in cases
+        )
+        + "\n"
+    ).encode("utf-8")
+    print(f"plaintext size: {len(plaintext)} bytes", file=sys.stderr)
+
+    ciphertext = _encrypt_to_age(plaintext, recipient_str)
+    print(f"ciphertext size: {len(ciphertext)} bytes", file=sys.stderr)
+
+    output_path.parent.mkdir(parents=True, exist_ok=True)
+    output_path.write_bytes(ciphertext)
+    print(f"wrote sealed file: {output_path}", file=sys.stderr)
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())
diff --git a/tests/test_adr_0119_7_sealed_gsm8k.py b/tests/test_adr_0119_7_sealed_gsm8k.py
new file mode 100644
index 00000000..37ab1cd2
--- /dev/null
+++ b/tests/test_adr_0119_7_sealed_gsm8k.py
@@ -0,0 +1,145 @@
+"""ADR-0119.7 — sealed GSM8K test set invariants.
+
+Pins four load-bearing invariants:
+
+1. **Sealed file exists.** ``evals/gsm8k_math/holdouts/v1/cases.jsonl.age``
+   is on disk and age-formatted.
+
+2. **No plaintext leaks.** No other plaintext-form holdout file
+   (``cases.jsonl``, ``cases_plaintext.jsonl``, etc.) exists alongside
+   the sealed file. The seal is one-way per ADR-0119.7's discipline.
+
+3. **Sealed file is on the expected key.** Decrypting with the recipe
+   identity registered under ADR-0119.1 succeeds; the plaintext parses
+   to JSONL with the documented schema.
+
+4. **Sealed file runs through the lane runner with `wrong == 0`.**
+   Even on real GSM8K data, the runner produces zero misparses. CORE
+   refuses what it can't grammar-handle; ADR-0114a Obligation #4
+   discipline is preserved against an external corpus.
+
+Skip behavior: tests that need to decrypt require the CORE_HOLDOUT_KEY
+env var pointing at the age identity. They are skipped (not failed)
+when the key is absent — matches ADR-0105's dev-mode discipline.
+"""
+
+from __future__ import annotations
+
+import json
+import os
+from pathlib import Path
+
+import pytest
+
+
+_REPO_ROOT = Path(__file__).resolve().parent.parent
+_HOLDOUT_DIR = _REPO_ROOT / "evals" / "gsm8k_math" / "holdouts" / "v1"
+_SEALED_PATH = _HOLDOUT_DIR / "cases.jsonl.age"
+
+
+def _decrypt_or_skip() -> bytes:
+    """Decrypt the sealed file using CORE_HOLDOUT_KEY, or skip the test."""
+    key_path_str = os.environ.get("CORE_HOLDOUT_KEY")
+    if not key_path_str:
+        pytest.skip(
+            "CORE_HOLDOUT_KEY not set; cannot decrypt sealed holdout. "
+            "This matches ADR-0105 dev-mode discipline — set the env "
+            "var only at release events."
+        )
+    try:
+        import pyrage
+        from pyrage.x25519 import Identity
+    except ImportError:
+        pytest.skip("pyrage not installed")
+    key_path = Path(key_path_str)
+    if not key_path.exists():
+        pytest.skip(f"CORE_HOLDOUT_KEY={key_path} does not exist")
+    identity = Identity.from_str(key_path.read_text(encoding="utf-8").strip())
+    return pyrage.decrypt(_SEALED_PATH.read_bytes(), [identity])
+
+
+class TestSealedFileExists:
+    def test_sealed_file_present(self) -> None:
+        assert _SEALED_PATH.exists()
+        assert _SEALED_PATH.is_file()
+        assert _SEALED_PATH.stat().st_size > 0
+
+    def test_sealed_file_is_age_formatted(self) -> None:
+        # age files start with "age-encryption.org/" magic header
+        head = _SEALED_PATH.read_bytes()[:64]
+        assert head.startswith(b"age-encryption.org/"), (
+            f"sealed file does not look age-formatted; head={head!r}"
+        )
+
+
+class TestNoPlaintextLeaks:
+    def test_no_plaintext_companions(self) -> None:
+        """Per ADR-0119.7 seal discipline: only the .age file is on disk."""
+        forbidden_names = (
+            "cases.jsonl",
+            "cases_plaintext.jsonl",
+            "cases-train.jsonl",
+        )
+        for name in forbidden_names:
+            path = _HOLDOUT_DIR / name
+            if path.exists():
+                # Size 0 placeholders are tolerable only if non-empty cases
+                # are guaranteed sealed. Default: refuse any sibling file.
+                pytest.fail(
+                    f"plaintext companion file {path} exists alongside "
+                    f"the sealed holdout; remove it or never commit it"
+                )
+
+
+class TestSealedFileDecryptsCleanly:
+    def test_decrypt_produces_jsonl(self) -> None:
+        plaintext = _decrypt_or_skip()
+        lines = plaintext.decode("utf-8").splitlines()
+        cases = [json.loads(line) for line in lines if line.strip()]
+        assert len(cases) >= 1000, (
+            f"sealed file decrypts to {len(cases)} cases; "
+            f"expected ≥ 1000 (GSM8K test has 1319)"
+        )
+
+    def test_every_case_has_documented_schema(self) -> None:
+        plaintext = _decrypt_or_skip()
+        cases = [
+            json.loads(line)
+            for line in plaintext.decode("utf-8").splitlines()
+            if line.strip()
+        ]
+        for case in cases[:20]:  # sample to keep test fast
+            assert "id" in case
+            assert case["id"].startswith("gsm8k-test-")
+            assert "problem" in case
+            assert isinstance(case["problem"], str) and case["problem"]
+            assert "expected_answer" in case
+            assert isinstance(case["expected_answer"], (int, float))
+            assert "expected_unit" in case
+            # ADR-0119.7 schema: empty unit signals "no unit-level check"
+            assert case["expected_unit"] == ""
+
+
+class TestSealedRunnerWrongZero:
+    """ADR-0114a Obligation #4 holds against real GSM8K."""
+
+    def test_runner_against_sealed_test_produces_zero_wrong(self) -> None:
+        from evals.gsm8k_math.runner import run_lane
+
+        plaintext = _decrypt_or_skip()
+        cases = [
+            json.loads(line)
+            for line in plaintext.decode("utf-8").splitlines()
+            if line.strip()
+        ]
+        report = run_lane(cases)
+        assert report.metrics["wrong"] == 0, (
+            f"runner produced {report.metrics['wrong']} wrong outcomes on "
+            f"the sealed GSM8K test; CORE silently confabulated"
+        )
+        assert report.metrics["wrong_count_is_zero"] is True
+        # correct + refused == total (accounting completeness, ADR-0119.3)
+        assert (
+            report.metrics["correct"] + report.metrics["refused"]
+            == report.metrics["cases_total"]
+        )