diff --git a/bin/gstack-doctor-components.sh b/bin/gstack-doctor-components.sh
index 3998eed6a..b52a021fc 100644
--- a/bin/gstack-doctor-components.sh
+++ b/bin/gstack-doctor-components.sh
@@ -167,6 +167,7 @@ gstack_result_anchor() {
     BRIEF_INPUT_MISSING) printf '%s' 'brief-input-missing' ;;
     DRAFT_DIRECTION_UNRESOLVED) printf '%s' 'draft-direction-unresolved' ;;
     PREGATE_GUARD_FAILED) printf '%s' 'pregate-guard-failed' ;;
+    SEALED_OUTPUT_REFUSED) printf '%s' 'sealed-output-refused' ;;
     *) return 1 ;;
   esac
 }
diff --git a/bin/gstack-pregate b/bin/gstack-pregate
index 4721f1bee..574ecaf21 100755
--- a/bin/gstack-pregate
+++ b/bin/gstack-pregate
@@ -9,6 +9,8 @@
  *   gstack-pregate clear --remote <workflow.yml/job> --run-url <url> | --bundle-lane <label> [--out <pregate.json>]
  *   gstack-pregate lanes [--explain]                             the lane list and platform tiers read from .github/workflows
  *   gstack-pregate validate | init [--explain] [--force]         the working-tree .gstack/pregate.json
+ *   gstack-pregate sealed [--range <a..b>] [--remote <name>] [--base <branch>] [--json]
+ *                                                                the sealed-output guard (lib/sealed-guard.ts) before any push or PR creation
  *
  * Runs at the entry of /ship Step 5 (before Step 6's paid evals and any
  * remote gate) under `set -o pipefail`, aggregates exit codes itself, prints
@@ -28,6 +30,7 @@ import { CHECKS, CHECK_IDS, PREGATE_OUT_REL, PREGATE_TIER2, clearObligation, rea
 import { describeLane, discoverLanes } from '../lib/pregate/workflows';
 import { ensureTmpExcluded } from '../lib/restamp';
 import { resultLine, type ResultCodeName } from '../lib/result-codes';
+import { evaluateSealed, publishedCommits, rangeCommits, renderSealed } from '../lib/sealed-guard';
 import { policyUnavailableLine, resolveBaseBranch } from '../lib/ship-policy';
 
 const HELP = `gstack-pregate — cheap checks before anything paid or remote (docs/pregate.md)
@@ -37,6 +40,9 @@ const HELP = `gstack-pregate — cheap checks before anything paid or remote (do
   clear           record the receipt that clears one requires-remote obligation
   lanes           print every CI lane with its platform tier (from .github/workflows/*.yml)
   validate | init the working-tree ${PREGATE_CONFIG_PATH}
+  sealed [--range <a..b>] [--remote <name>] [--base <branch>]
+                  the sealed-output guard (docs/pregate.md#sealed) over the commits <remote> lacks, or the range:
+                  run it before any push or PR creation in a repo with a \`sealed\` config; exit 1 refuses (SEALED_OUTPUT_REFUSED)
 
   --stage preflight|tests|all   default all
   --only <check,...>            restrict to these checks (${CHECK_IDS.join(', ')}; tier 2 later: ${PREGATE_TIER2.join(', ')})
@@ -62,6 +68,7 @@ const VERB_FLAGS: Record<string, [string[], string[]]> = {
   lanes: [[], ['--explain', '--json']],
   validate: [[], ['--json']],
   init: [[], ['--explain', '--force']],
+  sealed: [['--range', '--base', '--remote'], ['--json']],
 };
 const HINTS: Record<string, string> = { '--sealed': 'the sealed-output guard is the verb `gstack-pregate sealed`' };
 
@@ -152,6 +159,33 @@ function cmdClear(root: string, rest: string[]): number {
   return EXIT.ok;
 }
 
+function gitOut(root: string, args: string[]): string | null {
+  const r = spawnSync('git', args, { cwd: root, encoding: 'utf8', timeout: 30_000 });
+  return r.status === 0 ? r.stdout.trim() : null;
+}
+
+/** The sealed-output guard before any push or PR creation: the commits `--remote` lacks (or `--range a..b`), under base ∪ pushed policy. */
+function cmdSealed(root: string, rest: string[], json: boolean): number {
+  const base = resolveBaseBranch(root, flag(rest, '--base'));
+  const remote = flag(rest, '--remote') ?? 'origin';
+  const range = flag(rest, '--range');
+  const end = range ? (range.split(/\.\.\.?/)[1] || 'HEAD') : 'HEAD';
+  const pushedSha = gitOut(root, ['rev-parse', '--verify', '--quiet', `${end}^{commit}`]);
+  if (!pushedSha) { process.stderr.write(`gstack-pregate sealed: ${end} is not a commit\n`); return EXIT.usage; }
+  const listed = range ? rangeCommits(root, range) : publishedCommits(root, { localSha: pushedSha, remoteName: remote });
+  const baseRef = gitOut(root, ['rev-parse', '--verify', '--quiet', `refs/remotes/${remote}/${base}^{commit}`]) ? `refs/remotes/${remote}/${base}` : null;
+  const remoteUrl = gitOut(root, ['remote', 'get-url', remote]);
+  const report = 'error' in listed
+    ? { status: 'error' as const, error: listed.error, policyLabels: [], commits: 0, findings: [], waived: [], visibility: 'unknown' as const, visibilitySource: '', target: remoteUrl ?? remote }
+    : evaluateSealed({ repoRoot: root, targets: [{ commits: listed.commits, pushedSha }], baseRef, baseLabel: `${remote}/${base}`, remoteUrl, target: remoteUrl ?? remote });
+  const blocks = report.status === 'refused' || report.status === 'error';
+  if (json) { process.stdout.write(JSON.stringify({ ...report, ok: !blocks }) + '\n'); return blocks ? EXIT.fail : EXIT.ok; }
+  process.stderr.write(renderSealed(report, 'gstack-pregate sealed'));
+  const policy = report.policyLabels.length ? report.policyLabels.join(' + ') : `no sealed key on ${baseRef ?? `${remote}/${base}`} or ${end}`;
+  process.stdout.write(`SEALED: ${report.status} findings=${report.findings.length} commits=${report.commits} visibility=${report.visibility}${report.visibility === 'unknown' ? ' (counted public)' : ''} waived=${report.waived.length} policy=${policy}\n`);
+  return blocks ? EXIT.fail : EXIT.ok;
+}
+
 function main(argv: string[]): number {
   const cmd = argv[0] && !argv[0].startsWith('--') ? argv[0] : 'run';
   const rest = argv[0] && !argv[0].startsWith('--') ? argv.slice(1) : argv;
@@ -164,6 +198,7 @@ function main(argv: string[]): number {
   if (cmd === 'run') return cmdRun(root, rest, json);
   if (cmd === 'verify') return cmdVerify(root, rest, json);
   if (cmd === 'clear') return cmdClear(root, rest);
+  if (cmd === 'sealed') return cmdSealed(root, rest, json);
   if (cmd === 'lanes') {
     const lanes = discoverLanes(root);
     if (json) { process.stdout.write(JSON.stringify(lanes) + '\n'); return EXIT.ok; }
diff --git a/bin/gstack-redact-prepush b/bin/gstack-redact-prepush
index b3ccdd7fa..5cf65b097 100755
--- a/bin/gstack-redact-prepush
+++ b/bin/gstack-redact-prepush
@@ -29,6 +29,10 @@
  *     line, `#` comments. Only a finding whose matched text equals an entry is
  *     suppressed; every push that carries entries lists what they suppressed.
  *   - GSTACK_REDACT_PREPUSH=skip → log + exit 0 (escape valve).
+ *   - A repo with a `sealed` key in .gstack/pregate.json (base branch ∪ pushed
+ *     commit): lib/sealed-guard.ts checks every commit the push publishes for
+ *     sealed or eval output; a public (or unknown) destination refuses
+ *     (SEALED_OUTPUT_REFUSED), a private one warns.
  *
  * Installed/uninstalled via `gstack-redact install-prepush-hook` (see the
  * gstack-redact CLI), which chains any pre-existing hook.
@@ -39,6 +43,7 @@ import * as path from "path";
 import { normalizeWithMap, scan, type Finding, type ScanOptions } from "../lib/redact-engine";
 import { mkdirpSync } from "../lib/fs-utils";
 import { resolveStateRoot } from "../lib/state-root";
+import { evaluateSealed, publishedCommits, renderSealed, type SealedReport } from "../lib/sealed-guard";
 
 const ZERO = /^0+$/;
 let emptyTree: string | undefined;
@@ -594,6 +599,21 @@ function mediumLine(f: Finding, part: AddedFile): string {
   return `  MEDIUM  ${f.id}  ${where}  fix: ${fix}\n`;
 }
 
+/** The sealed-output guard over every commit this push publishes (lib/sealed-guard.ts); null when nothing is pushed. */
+function sealedForPush(refs: Array<{ localSha: string; remoteSha: string }>): SealedReport | null {
+  if (!refs.length) return null;
+  const target = pushTarget();
+  const remoteName = target.kind === "remote" ? target.name : target.kind === "unknown" && git(["remote"]).split("\n").includes("origin") ? "origin" : null;
+  const remoteUrl = process.argv[3] || (remoteName ? git(["remote", "get-url", remoteName]).trim() : "") || null;
+  const targets: Array<{ commits: string[]; pushedSha: string }> = [];
+  for (const ref of refs) {
+    const published = publishedCommits(".", { localSha: ref.localSha, remoteSha: ref.remoteSha, remoteName });
+    if ("error" in published) return { status: "error", error: published.error, policyLabels: [], commits: 0, findings: [], waived: [], visibility: "unknown", visibilitySource: "", target: remoteUrl ?? "the push target" };
+    targets.push({ commits: published.commits, pushedSha: ref.localSha });
+  }
+  return evaluateSealed({ repoRoot: ".", targets, baseRef: defaultRemoteBranch(), remoteUrl, target: remoteUrl ?? remoteName ?? "the push target" });
+}
+
 function main() {
   if ((process.env.GSTACK_REDACT_PREPUSH || "").toLowerCase() === "skip") {
     logSkip(process.env.GSTACK_REDACT_PREPUSH_REASON || "env-skip");
@@ -612,6 +632,7 @@ function main() {
   const allowEntries = new Set<string>();
   const historyRevs = new Set<string>();
   let trackingRemote: string | null = null;
+  const pushedRefs: Array<{ localSha: string; remoteSha: string }> = [];
 
   for (const fields of refs) {
     // Fail CLOSED on a ref line we cannot parse (#2498): git hands pre-push
@@ -630,6 +651,7 @@ function main() {
       process.exit(1);
     }
     if (ZERO.test(localSha!)) continue; // branch delete → nothing pushed
+    pushedRefs.push({ localSha: localSha!, remoteSha: remoteSha! });
     let added: AddedFile[];
     try {
       added = addedLinesFor(localSha, remoteSha || "0");
@@ -710,6 +732,11 @@ function main() {
     }
   }
 
+  const sealed = sealedForPush(pushedRefs);
+  const sealedText = sealed ? renderSealed(sealed, "gstack sealed-output guard") : "";
+  if (sealedText) process.stderr.write(sealedText);
+  const sealedBlocks = !!sealed && (sealed.status === "refused" || sealed.status === "error");
+
   if (allHigh.length > 0) {
     // A scan that could not RUN is not a scan that FOUND something. Reporting
     // "credential(s) in the pushed diff — rotate the credential" for an
@@ -757,7 +784,7 @@ function main() {
     process.exit(1);
   }
 
-  process.exit(0);
+  process.exit(sealedBlocks ? 1 : 0);
 }
 
 main();
diff --git a/docs/pregate.md b/docs/pregate.md
index 1bc8f35fa..900f1083f 100644
--- a/docs/pregate.md
+++ b/docs/pregate.md
@@ -64,6 +64,7 @@ the byte-pinned `/ship` renders in `test/fixtures/golden/`).
 | `strays.allow` | intentional root files or new top-level directories |
 | `guards` | `[{ id, when: [globs], command, fix?, timeout_s? }]`: repo commands a lane must pass when a touched file matches `when` (manifest checks, subprocess goldens the import graph cannot see); see [guards](#guards) |
 | `serial_patterns` | test-file globs the `lanes` check runs one process per file, apart from the unit files (default `**/*.serial.test.*`) |
+| `sealed` | sealed or eval output that must never reach a public destination; read by the pre-push hook and `gstack-pregate sealed` (see [sealed output](#sealed)) |
 | `price_file` | repo-relative path of the paid gate's call-plan data file (`GSTACK_EVAL_CALLS v1`); `gstack-eval-plan price-gate` prices from it and never executes anything ([docs/eval-calls.md](eval-calls.md)) |
 
 Only the `origin/<base>` copy is honoured, so a downgrade is reviewed before it
@@ -163,6 +164,52 @@ guard is a *command* with its own fix line. Older gstack refuses unknown keys
 that reads them ships. The worked gbrain configuration is in
 [gbrain worked configs](#gbrain-worked-configs).
 
+<a id="sealed"></a>
+## Sealed output: the pre-push hook and `gstack-pregate sealed`
+
+```json
+{ "sealed": {
+    "paths": ["heldout/**"],
+    "transcripts": ["runs/**/transcript*.jsonl"],
+    "answer_markers": ["SEALED ANSWER:"],
+    "seed_patterns": ["shuffle_seed=\\d+"],
+    "local_paths": true } }
+```
+
+A repo with a `sealed` key gets a configured local check against accidental
+publication whenever the managed pre-push hook (`gstack-redact
+install-prepush-hook`, no reinstall needed) or the standalone preflight runs:
+
+```
+gstack-pregate sealed [--range <a..b>] [--remote origin] [--base <branch>] [--json]
+```
+
+- **Boundary.** Every commit the push publishes: `git rev-list <local sha>
+  --not --remotes=<remote>` (and the remote tip when the ref exists); a
+  destination with no refs means everything reachable. `--range` names the
+  commits explicitly.
+- **Rules.** `sealed.path` and `sealed.transcript` check every path a commit
+  adds, renames or copies, whatever its content (binary, empty, deleted again
+  in a later commit); `sealed.answer`, `sealed.seed` and `sealed.local_path`
+  (`/home/<user>/`, `/Users/<user>/`, `C:\Users\<user>\`) check each commit's added
+  lines. Findings print rule, `file[:line]` and commit, never the text.
+- **Policy.** The union of the destination base branch's `sealed` and the
+  pushed commit's: a push can tighten it, never relax it. A malformed or
+  unreadable policy refuses. Waivers come only from the base branch's
+  `.gstack/sealed-allow.tsv` (`rule<TAB>path<TAB>sha<TAB>reason`) and are
+  listed on every push.
+- **Visibility.** `sealed.visibility` from the base branch, else a cache under
+  the state root (`sealed-visibility.json`: a `public` answer for 24 hours, a
+  `private` one for 1 hour before it may turn a refusal into a warning), else
+  `gh repo view --json visibility` (5 s). Unknown, unreadable or newly created
+  counts as public. Public refuses (`SEALED_OUTPUT_REFUSED`, exit 1); private
+  warns.
+
+Capy's pull-request tool may not run local git hooks, so an agent runs
+`gstack-pregate sealed` before any push or PR creation in a repo with a
+`sealed` config (the coordinator contract says so). Hosted CI on the public
+repository only detects a bypass after the upload.
+
 <a id="issue-links"></a>
 ## `gstack-issue-links`
 
diff --git a/docs/troubleshooting.md b/docs/troubleshooting.md
index ca4e9f6eb..2ad23a5c9 100644
--- a/docs/troubleshooting.md
+++ b/docs/troubleshooting.md
@@ -2480,3 +2480,23 @@ downgraded to warn.
 and do what its `fix` line says, commit, then rerun
 `gstack-pregate run --allow-repo-commands`. A lane reports done only after this
 passes and carries the `PREGATE:` line in its handoff.
+
+<a id="sealed-output-refused"></a>
+### `SEALED_OUTPUT_REFUSED`
+
+**Meaning.** The repo declares a `sealed` policy in `.gstack/pregate.json`
+(base branch ∪ the pushed commit) and a commit this push publishes adds a
+sealed path or transcript (binary, empty and later-deleted files included), or
+adds a line with a sealed-answer marker, a seed or a local home path, and the
+destination is public or its visibility is unknown (a new or unreadable
+repository counts as public). An unreadable or malformed sealed policy refuses
+too. The managed pre-push hook and `gstack-pregate sealed` print one line per
+finding: rule, `file[:line]`, commit. They never print the matched text.
+
+**Fix.** Remove the output from every published commit before the branch
+reaches the public repository (a later commit that deletes it still publishes
+it). A reviewed false positive gets one line in the base branch's
+`.gstack/sealed-allow.tsv`: `rule<TAB>path<TAB>sha<TAB>reason`. A private
+destination sets `"visibility": "private"` under `sealed` in the base branch's
+`.gstack/pregate.json`. Capy's pull-request tool may not run local hooks, so
+run `gstack-pregate sealed` yourself before any push or PR creation.
diff --git a/lib/pregate/config.ts b/lib/pregate/config.ts
index 4ca276ea0..af6dd4bd5 100644
--- a/lib/pregate/config.ts
+++ b/lib/pregate/config.ts
@@ -18,6 +18,8 @@
  *                 (manifest checks, CLI goldens); never downgradable
  *   serial_patterns globs of test files the lanes check runs one process each
  *                 (default: every `*.serial.test.*` file)
+ *   sealed        the sealed-output guard's rules (lib/sealed-guard.ts; read by
+ *                 the pre-push hook and `gstack-pregate sealed`, not by `run`)
  *   price_file    the call-plan data file `gstack-eval-plan price-gate` prices
  *                 a paid gate from (GSTACK_EVAL_CALLS v1; never executed)
  */
@@ -25,6 +27,7 @@ import * as fs from 'node:fs';
 import * as path from 'node:path';
 import { spawnSync } from 'node:child_process';
 import type { ResultCodeName } from '../result-codes';
+import { sealedErrors } from '../sealed-guard';
 import { containedRelative, globToRegExp } from '../ship-policy';
 
 export const PREGATE_CONFIG_PATH = '.gstack/pregate.json';
@@ -49,7 +52,7 @@ export interface ConfigError { code: ResultCodeName; path: string; message: stri
 
 const MAX_LIST = 256;
 const MAX_COMMAND = 512;
-const KEYS = ['runner', 'dependencies', 'selection', 'warn', 'strays', 'guards', 'serial_patterns', 'price_file'];
+const KEYS = ['runner', 'dependencies', 'selection', 'warn', 'strays', 'guards', 'serial_patterns', 'price_file', 'sealed'];
 const MAX_GUARDS = 32;
 const GUARD_KEYS = ['id', 'when', 'command', 'fix', 'timeout_s'];
 
@@ -102,6 +105,7 @@ export function validateConfig(raw: unknown, knownChecks: readonly string[] = []
     if (why) errors.push({ code: 'PREGATE_CONFIG_INVALID', path: 'price_file', message: why });
   }
   if ('guards' in obj) guardErrors(obj.guards, errors);
+  if ('sealed' in obj) for (const e of sealedErrors(obj.sealed)) errors.push({ code: 'PREGATE_CONFIG_INVALID', path: e.path, message: e.message });
   if ('serial_patterns' in obj) {
     const list = obj.serial_patterns;
     if (!Array.isArray(list) || list.some(g => typeof g !== 'string')) errors.push({ code: 'PREGATE_CONFIG_INVALID', path: 'serial_patterns', message: 'must be an array of globs' });
@@ -208,6 +212,7 @@ export function explainConfig(): string {
     'strays.allow: root files or new top-level directories that are intentional',
     'guards: [{ id, when: [globs], command, fix?, timeout_s? }]: each guard whose globs match a touched file runs in its own process (--allow-repo-commands); a failure fails pregate with the guard id and fix; never downgradable',
     `serial_patterns: test-file globs the lanes check runs one process per file, apart from the unit files (default ${DEFAULT_SERIAL_PATTERNS.join(', ')})`,
+    'sealed: { paths, transcripts, answer_markers, seed_patterns, local_paths, visibility }: sealed or eval output the pre-push hook and `gstack-pregate sealed` refuse to publish to a public destination (docs/pregate.md#sealed)',
     'price_file: repo-relative path of the GSTACK_EVAL_CALLS v1 call-plan file `gstack-eval-plan price-gate` prices a paid gate from; never executed (docs/eval-calls.md)',
   ].join('\n') + '\n';
 }
diff --git a/lib/result-codes.ts b/lib/result-codes.ts
index 93291e928..ccc974133 100644
--- a/lib/result-codes.ts
+++ b/lib/result-codes.ts
@@ -471,6 +471,11 @@ export const RESULT_CODES = {
     summary: 'a repo guard from .gstack/pregate.json whose files the branch touched exited non-zero',
     fix: 'run the guard command printed in the table, apply the guard\'s fix line, commit, then rerun `gstack-pregate run --allow-repo-commands`',
   },
+  SEALED_OUTPUT_REFUSED: {
+    anchor: 'sealed-output-refused',
+    summary: 'a push or PR would publish sealed or eval output (a sealed path, a transcript, a quoted answer, a seed or a local home path) to a public or unknown destination, or the sealed policy is unreadable',
+    fix: 'remove it from every published commit, or add one reviewed `rule<TAB>path<TAB>sha<TAB>reason` line to the base branch\'s .gstack/sealed-allow.tsv; a private destination sets sealed.visibility "private" in the base branch\'s .gstack/pregate.json',
+  },
 } as const satisfies Record<string, ResultCode>;
 
 export type ResultCodeName = keyof typeof RESULT_CODES;
diff --git a/lib/sealed-guard.ts b/lib/sealed-guard.ts
new file mode 100644
index 000000000..e10c08a6a
--- /dev/null
+++ b/lib/sealed-guard.ts
@@ -0,0 +1,276 @@
+/**
+ * sealed-guard — the sealed-output guard (field wave CD4), shared by the
+ * managed pre-push hook (bin/gstack-redact-prepush) and the standalone
+ * preflight `gstack-pregate sealed [--range <a..b>]`.
+ *
+ * A repo opts in with a `sealed` key in `.gstack/pregate.json`:
+ *   paths           globs that may never be published (held-out sets, cells)
+ *   transcripts     globs of per-cell transcripts
+ *   answer_markers  regexes for a quoted sealed answer in added text
+ *   seed_patterns   regexes for a sampling seed in added text
+ *   local_paths     true: a local home path (/home/<u>/, /Users/<u>/) in added text
+ *   visibility      "public" | "private": the destination override (reviewed on the base branch)
+ *
+ * The publication boundary is every commit the push publishes: the local sha
+ * minus everything the destination remote already has (`git rev-list <local>
+ * --not --remotes=<remote> ^<remote sha>`); a destination with no refs means
+ * everything reachable. Path rules see every path a commit adds, renames or
+ * copies, independent of content (binary, empty, add-then-delete); text rules
+ * see each commit's added lines. The effective policy is the union of the
+ * destination base branch's `sealed` and the pushed one (a push can tighten,
+ * never relax); waivers come only from the base branch's
+ * `.gstack/sealed-allow.tsv`. A malformed or unreadable policy refuses (fail
+ * closed). Visibility: the base override, else a cache under the state root
+ * (a `public` answer for 24 h, a `private` one for 1 h before it may
+ * downgrade a refusal), else `gh repo view` (5 s); unknown counts as public.
+ * Findings name file, line, rule and commit, never the matched text.
+ */
+import { spawnSync } from 'node:child_process';
+import * as fs from 'node:fs';
+import * as path from 'node:path';
+import { containedRelative, globToRegExp, matchesAny } from './ship-policy';
+import { resolveStateRoot } from './state-root';
+
+export const SEALED_CONFIG_PATH = '.gstack/pregate.json';
+export const SEALED_ALLOW_PATH = '.gstack/sealed-allow.tsv';
+export const VISIBILITY_OVERRIDE_KEY = 'sealed.visibility';
+export type SealedRule = 'sealed.path' | 'sealed.transcript' | 'sealed.answer' | 'sealed.seed' | 'sealed.local_path';
+export interface SealedPolicy { paths: string[]; transcripts: string[]; answer_markers: string[]; seed_patterns: string[]; local_paths: boolean; visibility?: 'public' | 'private' }
+export interface SealedFinding { rule: SealedRule; file: string; line?: number; commit: string }
+export interface AllowEntry { rule: string; path: string; sha: string; reason: string }
+export type Visibility = 'public' | 'private' | 'unknown';
+
+const KEYS = ['paths', 'transcripts', 'answer_markers', 'seed_patterns', 'local_paths', 'visibility'];
+const MAX_ENTRIES = 64;
+const MAX_REGEX = 256;
+const LOCAL_PATH_RE = /(?:^|[^A-Za-z0-9_.~-])(?:\/home\/[^/\s'"`]+\/|\/Users\/[^/\s'"`]+\/|[A-Za-z]:\\+Users\\+[^\\\s'"`]+\\)/;
+const PUBLIC_TTL_MS = 24 * 3600_000;
+const PRIVATE_TTL_MS = 3600_000;
+
+/** `<key>: <message>` errors for a `sealed` value; empty when valid. Shared with lib/pregate/config.ts. */
+export function sealedErrors(raw: unknown): Array<{ path: string; message: string }> {
+  const errors: Array<{ path: string; message: string }> = [];
+  if (!raw || typeof raw !== 'object' || Array.isArray(raw)) return [{ path: 'sealed', message: 'must be an object { paths, transcripts, answer_markers, seed_patterns, local_paths, visibility }' }];
+  const o = raw as Record<string, unknown>;
+  for (const k of Object.keys(o)) if (!KEYS.includes(k)) errors.push({ path: `sealed.${k}`, message: `unknown key; valid keys: ${KEYS.join(', ')}` });
+  const list = (key: string, check: (s: string) => string | null) => {
+    if (!(key in o)) return;
+    const v = o[key];
+    if (!Array.isArray(v) || v.some(s => typeof s !== 'string')) { errors.push({ path: `sealed.${key}`, message: 'must be an array of strings' }); return; }
+    if (v.length > MAX_ENTRIES) errors.push({ path: `sealed.${key}`, message: `more than ${MAX_ENTRIES} entries` });
+    (v as string[]).forEach((s, i) => { const why = check(s); if (why) errors.push({ path: `sealed.${key}[${i}]`, message: `${JSON.stringify(s)} ${why}` }); });
+  };
+  const glob = (g: string) => { const why = containedRelative(g); if (why) return why; try { globToRegExp(g); return null; } catch (e: any) { return e.message; } };
+  const regex = (r: string) => { if (!r || r.length > MAX_REGEX) return `must be 1-${MAX_REGEX} characters`; try { new RegExp(r); return null; } catch (e: any) { return `is not a valid regex (${e.message})`; } };
+  list('paths', glob); list('transcripts', glob); list('answer_markers', regex); list('seed_patterns', regex);
+  if ('local_paths' in o && typeof o.local_paths !== 'boolean') errors.push({ path: 'sealed.local_paths', message: 'must be true or false' });
+  if ('visibility' in o && o.visibility !== 'public' && o.visibility !== 'private') errors.push({ path: 'sealed.visibility', message: 'must be "public" or "private"' });
+  return errors;
+}
+
+function git(repoRoot: string, args: string[], input?: string): { ok: boolean; out: string; err: string } {
+  const r = spawnSync('git', args, { cwd: repoRoot, encoding: 'utf8', input, timeout: 120_000, maxBuffer: 256 * 1024 * 1024 });
+  return { ok: r.status === 0, out: r.stdout ?? '', err: (r.stderr ?? '').trim() };
+}
+
+export type PolicyRead = { policy: SealedPolicy | null; label: string } | { error: string; label: string };
+
+/** The `sealed` key of `.gstack/pregate.json` at a commit; null when absent; an error when present but unreadable. */
+export function sealedPolicyAt(repoRoot: string, treeish: string, label: string): PolicyRead {
+  const spec = `${treeish}:${SEALED_CONFIG_PATH}`;
+  if (!git(repoRoot, ['cat-file', '-e', spec]).ok) return { policy: null, label };
+  const show = git(repoRoot, ['cat-file', 'blob', spec]);
+  if (!show.ok) return { error: `cannot read ${SEALED_CONFIG_PATH} (${show.err})`, label };
+  let raw: any;
+  try { raw = JSON.parse(show.out); }
+  catch (e: any) { return /"sealed"/.test(show.out) ? { error: `${SEALED_CONFIG_PATH} is not valid JSON (${e.message})`, label } : { policy: null, label }; }
+  if (!raw || typeof raw !== 'object' || !('sealed' in raw)) return { policy: null, label };
+  const errors = sealedErrors(raw.sealed);
+  if (errors.length) return { error: errors.map(e => `${e.path}: ${e.message}`).join('; '), label };
+  const s = raw.sealed;
+  return { policy: { paths: s.paths ?? [], transcripts: s.transcripts ?? [], answer_markers: s.answer_markers ?? [], seed_patterns: s.seed_patterns ?? [], local_paths: s.local_paths === true, visibility: s.visibility }, label };
+}
+
+/** Base ∪ pushed: lists concatenate, `local_paths` ORs; visibility stays private only when the base says so and the push does not say public. */
+export function unionPolicies(base: SealedPolicy | null, pushed: SealedPolicy | null): SealedPolicy | null {
+  if (!base && !pushed) return null;
+  const u = (k: 'paths' | 'transcripts' | 'answer_markers' | 'seed_patterns') => [...new Set([...(base?.[k] ?? []), ...(pushed?.[k] ?? [])])];
+  const visibility = pushed?.visibility === 'public' || base?.visibility === 'public' ? 'public' : base?.visibility === 'private' ? 'private' : undefined;
+  return { paths: u('paths'), transcripts: u('transcripts'), answer_markers: u('answer_markers'), seed_patterns: u('seed_patterns'), local_paths: !!(base?.local_paths || pushed?.local_paths), visibility };
+}
+
+/** Reviewed waivers: `rule<TAB>path<TAB>sha<TAB>reason` lines in the base branch's allow file. */
+export function allowEntriesAt(repoRoot: string, treeish: string | null): AllowEntry[] {
+  if (!treeish) return [];
+  const show = git(repoRoot, ['cat-file', 'blob', `${treeish}:${SEALED_ALLOW_PATH}`]);
+  if (!show.ok) return [];
+  return show.out.split('\n').filter(l => l.trim() && !l.startsWith('#')).map(l => l.split('\t')).filter(f => f.length >= 4 && /^[0-9a-f]{7,64}$/.test(f[2]!) && f[3]!.trim())
+    .map(f => ({ rule: f[0]!.trim(), path: f[1]!.trim(), sha: f[2]!, reason: f.slice(3).join('\t').trim() }));
+}
+
+/** Commits a push publishes: local minus the remote's refs (and its tip for this ref); null remote and no tip → everything reachable. */
+export function publishedCommits(repoRoot: string, o: { localSha: string; remoteSha?: string | null; remoteName?: string | null }): { commits: string[] } | { error: string } {
+  const not: string[] = [];
+  if (o.remoteName) not.push(`--remotes=${o.remoteName}/*`);
+  if (o.remoteSha && !/^0+$/.test(o.remoteSha) && git(repoRoot, ['cat-file', '-e', `${o.remoteSha}^{commit}`]).ok) not.push(o.remoteSha);
+  const r = git(repoRoot, ['rev-list', o.localSha, ...(not.length ? ['--not', ...not] : [])]);
+  if (!r.ok) return { error: `git rev-list failed: ${r.err.slice(0, 200)}` };
+  return { commits: r.out.split('\n').filter(Boolean) };
+}
+
+export function rangeCommits(repoRoot: string, range: string): { commits: string[] } | { error: string } {
+  const r = git(repoRoot, ['rev-list', range]);
+  if (!r.ok) return { error: `git rev-list ${range} failed: ${r.err.slice(0, 200)}` };
+  return { commits: r.out.split('\n').filter(Boolean) };
+}
+
+const HEX = /^[0-9a-f]{40,64}$/;
+
+/** Path rules over every added, renamed or copied path, per commit (merges: paths new against every parent). */
+function pathFindings(repoRoot: string, commits: string[], p: SealedPolicy): SealedFinding[] {
+  if (!p.paths.length && !p.transcripts.length) return [];
+  const r = git(repoRoot, ['-c', 'core.quotePath=false', 'diff-tree', '--stdin', '-r', '--root', '-M', '-C', '--cc', '--name-status', '-z'], commits.join('\n') + '\n');
+  if (!r.ok) throw new Error(`git diff-tree failed: ${r.err.slice(0, 200)}`);
+  const out: SealedFinding[] = [];
+  const tokens = r.out.split('\0');
+  let commit = '';
+  for (let i = 0; i < tokens.length; i++) {
+    const t = tokens[i]!;
+    if (!t) continue;
+    if (HEX.test(t)) { commit = t; continue; }
+    const renamed = /^[RC]\d*$/.test(t);
+    const file = renamed ? tokens[i += 2]! : tokens[++i]!;
+    if (!renamed && !t.includes('A')) continue;
+    if (matchesAny(p.transcripts, file)) out.push({ rule: 'sealed.transcript', file, commit });
+    else if (matchesAny(p.paths, file)) out.push({ rule: 'sealed.path', file, commit });
+  }
+  return out;
+}
+
+/** Text rules over each commit's added lines (`--cc` for merges: only the resolution's own lines). */
+function textFindings(repoRoot: string, commits: string[], p: SealedPolicy): SealedFinding[] {
+  const rules: Array<[SealedRule, RegExp]> = [
+    ...p.answer_markers.map(r => ['sealed.answer', new RegExp(r)] as [SealedRule, RegExp]),
+    ...p.seed_patterns.map(r => ['sealed.seed', new RegExp(r)] as [SealedRule, RegExp]),
+    ...(p.local_paths ? [['sealed.local_path', LOCAL_PATH_RE] as [SealedRule, RegExp]] : []),
+  ];
+  if (!rules.length) return [];
+  const r = git(repoRoot, ['-c', 'core.quotePath=false', 'diff-tree', '--stdin', '-r', '--root', '-M', '-C', '--cc', '-p', '--unified=0', '--no-color', '--no-ext-diff', '--no-textconv'], commits.join('\n') + '\n');
+  if (!r.ok) throw new Error(`git diff-tree -p failed: ${r.err.slice(0, 200)}`);
+  const out: SealedFinding[] = [];
+  let commit = ''; let file = ''; let inHunk = false; let parents = 1; let next = 0;
+  for (const line of r.out.split('\n')) {
+    if (HEX.test(line)) { commit = line; inHunk = false; continue; }
+    if (line.startsWith('diff --')) { inHunk = false; file = ''; continue; }
+    if (line.startsWith('@@')) { inHunk = true; parents = (/^@+/.exec(line)?.[0].length ?? 2) - 1; next = Number(/ \+(\d+)(?:,\d+)? @+/.exec(line)?.[1] ?? 0); continue; }
+    if (!inHunk) { if (line.startsWith('+++ ')) file = line.startsWith('+++ b/') ? line.slice(6) : ''; continue; }
+    const prefix = line.slice(0, parents);
+    if (line.startsWith('\\') || prefix.includes('-')) continue;
+    const n = next++;
+    if (!prefix.includes('+')) continue;
+    const text = line.slice(parents);
+    for (const [rule, re] of rules) if (re.test(text)) out.push({ rule, file, line: n, commit });
+  }
+  return out;
+}
+
+export function scanCommits(repoRoot: string, commits: string[], policy: SealedPolicy): SealedFinding[] {
+  if (!commits.length) return [];
+  const seen = new Set<string>();
+  return [...pathFindings(repoRoot, commits, policy), ...textFindings(repoRoot, commits, policy)].filter(f => {
+    const key = `${f.rule}\0${f.file}\0${f.line ?? ''}\0${f.commit}`;
+    if (seen.has(key)) return false;
+    seen.add(key);
+    return true;
+  });
+}
+
+/** `owner/repo` for a GitHub remote URL; null for anything else (a local path, another host). */
+export function githubSlug(url: string | null | undefined): string | null {
+  const m = /^(?:https?:\/\/(?:[^@/]+@)?github\.com\/|ssh:\/\/git@github\.com\/|git@github\.com:)([A-Za-z0-9-]+)\/([A-Za-z0-9._-]+?)(?:\.git)?\/?$/.exec((url ?? '').trim());
+  return m ? `${m[1]}/${m[2]}` : null;
+}
+
+export interface VisibilityOptions { env?: NodeJS.ProcessEnv; gh?: (args: string[]) => { ok: boolean; out: string }; now?: number }
+
+/** Destination visibility: cache (public 24 h, private 1 h), else `gh repo view` (5 s); unknown on any failure or a non-GitHub remote. */
+export function resolveVisibility(url: string | null, o: VisibilityOptions = {}): { visibility: Visibility; source: string } {
+  const slug = githubSlug(url);
+  if (!slug) return { visibility: 'unknown', source: 'not a GitHub remote' };
+  const now = o.now ?? Date.now();
+  const file = path.join(resolveStateRoot(o.env ?? process.env), 'sealed-visibility.json');
+  let cache: Record<string, { visibility: Visibility; checked_at: number }> = {};
+  try { cache = JSON.parse(fs.readFileSync(file, 'utf8')).entries ?? {}; } catch { cache = {}; }
+  const hit = cache[slug];
+  if (hit && ((hit.visibility === 'public' && now - hit.checked_at < PUBLIC_TTL_MS) || (hit.visibility === 'private' && now - hit.checked_at < PRIVATE_TTL_MS))) return { visibility: hit.visibility, source: `cache ${new Date(hit.checked_at).toISOString()}` };
+  const gh = o.gh ?? ((args: string[]) => { const r = spawnSync('gh', args, { encoding: 'utf8', timeout: 5_000, env: o.env ?? process.env }); return { ok: r.status === 0, out: r.stdout ?? '' }; });
+  const r = gh(['repo', 'view', slug, '--json', 'visibility']);
+  let v: string | undefined;
+  try { v = r.ok ? String(JSON.parse(r.out).visibility ?? '').toLowerCase() : undefined; } catch { v = undefined; }
+  if (v !== 'public' && v !== 'private' && v !== 'internal') return { visibility: 'unknown', source: `gh repo view ${slug} failed (a new or unreadable repository counts as public)` };
+  const visibility: Visibility = v === 'public' ? 'public' : 'private';
+  cache[slug] = { visibility, checked_at: now };
+  try { fs.mkdirSync(path.dirname(file), { recursive: true }); fs.writeFileSync(file, JSON.stringify({ entries: cache }, null, 2) + '\n'); } catch { /* an unwritable cache only costs a lookup */ }
+  return { visibility, source: `gh repo view ${slug}` };
+}
+
+export interface SealedReport {
+  status: 'no-policy' | 'clear' | 'refused' | 'warned' | 'error';
+  policyLabels: string[]; commits: number; findings: SealedFinding[]; waived: Array<SealedFinding & { reason: string }>;
+  visibility: Visibility; visibilitySource: string; target: string; error?: string;
+}
+
+export interface EvaluateOptions {
+  repoRoot: string; targets: Array<{ commits: string[]; pushedSha: string }>; baseRef: string | null; baseLabel?: string; remoteUrl: string | null; target: string;
+  env?: NodeJS.ProcessEnv; gh?: VisibilityOptions['gh'];
+}
+
+/** The whole guard for one push (or range): policies, commits, findings, waivers, visibility, verdict. */
+export function evaluateSealed(o: EvaluateOptions): SealedReport {
+  const blank = { policyLabels: [] as string[], commits: 0, findings: [] as SealedFinding[], waived: [] as Array<SealedFinding & { reason: string }>, visibility: 'unknown' as Visibility, visibilitySource: '', target: o.target };
+  const base = o.baseRef ? sealedPolicyAt(o.repoRoot, o.baseRef, o.baseLabel ?? o.baseRef) : { policy: null, label: '(no destination base branch)' };
+  if ('error' in base) return { ...blank, status: 'error', error: `the sealed policy on ${base.label} is unreadable: ${base.error}` };
+  let policy: SealedPolicy | null = base.policy;
+  const labels = base.policy ? [base.label] : [];
+  for (const t of o.targets) {
+    const pushed = sealedPolicyAt(o.repoRoot, t.pushedSha, `pushed ${t.pushedSha.slice(0, 12)}`);
+    if ('error' in pushed) return { ...blank, status: 'error', error: `the sealed policy in ${pushed.label} is unreadable: ${pushed.error}` };
+    if (pushed.policy) labels.push(pushed.label);
+    policy = unionPolicies(policy, pushed.policy);
+  }
+  if (!policy) return { ...blank, status: 'no-policy' };
+  const commits = [...new Set(o.targets.flatMap(t => t.commits))];
+  let found: SealedFinding[];
+  try { found = scanCommits(o.repoRoot, commits, policy); }
+  catch (e: any) { return { ...blank, policyLabels: labels, commits: commits.length, status: 'error', error: `could not read the published commits: ${e.message}` }; }
+  const allow = allowEntriesAt(o.repoRoot, o.baseRef);
+  const waived: SealedReport['waived'] = [];
+  const findings = found.filter(f => {
+    const entry = allow.find(a => a.rule === f.rule && a.path === f.file && f.commit.startsWith(a.sha));
+    if (entry) waived.push({ ...f, reason: entry.reason });
+    return !entry;
+  });
+  const vis = policy.visibility ? { visibility: policy.visibility as Visibility, source: `${VISIBILITY_OVERRIDE_KEY} override` } : resolveVisibility(o.remoteUrl, { env: o.env, gh: o.gh });
+  const status = findings.length === 0 ? 'clear' : vis.visibility === 'private' ? 'warned' : 'refused';
+  return { status, policyLabels: labels, commits: commits.length, findings, waived, visibility: vis.visibility, visibilitySource: vis.source, target: o.target };
+}
+
+const where = (f: SealedFinding) => `${f.file || '(unknown file)'}${f.line ? `:${f.line}` : ''}`;
+
+/** stderr text for a report: findings one per line (`<rule>  <file[:line]>  commit <sha12>`), never the matched text. */
+export function renderSealed(r: SealedReport, context: string): string {
+  const lines: string[] = [];
+  for (const w of r.waived) lines.push(`${context}: waived ${w.rule}  ${where(w)}  commit ${w.commit.slice(0, 12)} (${SEALED_ALLOW_PATH}: ${w.reason})`);
+  const vis = `visibility: ${r.visibility}${r.visibility === 'unknown' ? ', counted public' : ''}; ${r.visibilitySource}`;
+  const body = r.findings.map(f => `  ${f.rule}  ${where(f)}  commit ${f.commit.slice(0, 12)}`);
+  if (r.status === 'error') {
+    lines.push(`\n⛔ ${context} BLOCKED the publication of ${r.target} — ${r.error}.`);
+    lines.push(`Fix the sealed policy (gstack-pregate validate), then retry; an unreadable policy never passes (SEALED_OUTPUT_REFUSED)`);
+  } else if (r.status === 'refused') {
+    lines.push(`\n⛔ ${context} BLOCKED the publication of ${r.target} (${vis}) — sealed or eval output in ${r.commits} published commit(s):`, ...body);
+    lines.push(`Remove it from every published commit before this branch reaches a public repository, or waive one reviewed finding with a \`rule<TAB>path<TAB>sha<TAB>reason\` line in the base branch's ${SEALED_ALLOW_PATH}. A private destination: set ${VISIBILITY_OVERRIDE_KEY} "private" in the base branch's ${SEALED_CONFIG_PATH} (SEALED_OUTPUT_REFUSED)`);
+  } else if (r.status === 'warned') {
+    lines.push(`${context}: warning — sealed or eval output in a push to a private destination (${vis}); it would be refused for a public one:`, ...body);
+  }
+  return lines.length ? lines.join('\n') + '\n' : '';
+}
diff --git a/test/fixtures/module-size-ratchet.json b/test/fixtures/module-size-ratchet.json
index b67f28d38..39505e62b 100644
--- a/test/fixtures/module-size-ratchet.json
+++ b/test/fixtures/module-size-ratchet.json
@@ -105,7 +105,8 @@
     { "file": "lib/pregate/checks/literals.ts", "movedFrom": "(new: pre-gate check, C8)" },
     { "file": "lib/pregate/checks/lanes.ts", "movedFrom": "(new: pre-gate check with the pipefail runner and requires-remote obligations, C8)" },
     { "file": "lib/pregate/checks/guards.ts", "movedFrom": "(new: pre-gate repo guards, field wave CD1)" },
-    { "file": "lib/pregate/runtime.ts", "movedFrom": "(new: the verified launch Bun for repo commands, field wave CD1)" }
+    { "file": "lib/pregate/runtime.ts", "movedFrom": "(new: the verified launch Bun for repo commands, field wave CD1)" },
+    { "file": "lib/sealed-guard.ts", "movedFrom": "(new: the sealed-output guard shared by the pre-push hook and gstack-pregate sealed, field wave CD4)" }
   ],
   "residualFiles": [
     { "file": "scripts/test-free-shards.ts", "maxLines": 2361, "reason": "free lane policy after the shard engine took spawn, sandbox, logs, seeds and flags" },
diff --git a/test/pregate-guards.test.ts b/test/pregate-guards.test.ts
index 19c59528c..9b70a6c03 100644
--- a/test/pregate-guards.test.ts
+++ b/test/pregate-guards.test.ts
@@ -127,6 +127,16 @@ describe('guards (CD1)', () => {
   });
 });
 
+describe('pregate config: sealed (CD4)', () => {
+  test('`gstack-pregate validate` accepts a sealed policy and names each bad field', () => {
+    expect(codes({ sealed: { paths: ['heldout/**'], transcripts: ['runs/**/transcript*.jsonl'], answer_markers: ['SEALED ANSWER:'], seed_patterns: ['seed=\\d+'], local_paths: true, visibility: 'private' } })).toEqual([]);
+    expect(codes({ sealed: { paths: 'heldout/**' } })).toEqual(['PREGATE_CONFIG_INVALID:sealed.paths']);
+    expect(codes({ sealed: { seed_patterns: ['('] } })).toEqual(['PREGATE_CONFIG_INVALID:sealed.seed_patterns[0]']);
+    expect(codes({ sealed: { visibility: 'internal' } })).toEqual(['PREGATE_CONFIG_INVALID:sealed.visibility']);
+    expect(codes({ sealed: { block: true } })).toEqual(['PREGATE_CONFIG_INVALID:sealed.block']);
+  });
+});
+
 describe('gstack-pregate flags (CD1)', () => {
   test('an unknown flag is usage (exit 2) on every verb instead of a silent normal run', () => {
     const repo = makeFixtureRepo(); repos.push(repo);
diff --git a/test/sealed-guard.test.ts b/test/sealed-guard.test.ts
new file mode 100644
index 000000000..143a62539
--- /dev/null
+++ b/test/sealed-guard.test.ts
@@ -0,0 +1,223 @@
+/**
+ * Field wave CD4: the sealed-output guard. A repo that declares `sealed` in
+ * `.gstack/pregate.json` cannot push sealed or eval output to a public
+ * destination by accident: the managed pre-push hook and
+ * `gstack-pregate sealed` enumerate every commit the push publishes (local
+ * sha minus everything the destination remote already has), apply path
+ * rules to every added, renamed or copied path (binary and empty files,
+ * add-then-delete) and text rules to each commit's added lines. The policy
+ * is the union of the base branch's and the pushed one; waivers come only
+ * from the base branch's allow file; an unknown visibility counts as public.
+ * Field incident: a per-cell transcript, a quoted sealed answer, a seed and a
+ * /home/user path were pushed to a public eval repo with exit 0 and no output.
+ */
+import { afterEach, describe, expect, test } from 'bun:test';
+import { spawnSync } from 'node:child_process';
+import * as fs from 'node:fs';
+import * as os from 'node:os';
+import * as path from 'node:path';
+import { resolveVisibility } from '../lib/sealed-guard';
+
+const ROOT = path.resolve(import.meta.dir, '..');
+const PREPUSH = path.join(ROOT, 'bin', 'gstack-redact-prepush');
+const PREGATE = path.join(ROOT, 'bin', 'gstack-pregate');
+const ZERO = '0'.repeat(40);
+const SEALED = {
+  paths: ['heldout/**'],
+  transcripts: ['runs/**/transcript*.jsonl'],
+  answer_markers: ['SEALED ANSWER:'],
+  seed_patterns: ['shuffle_seed=\\d+'],
+  local_paths: true,
+};
+
+interface Scratch { root: string; work: string; origin: string; state: string; env: Record<string, string> }
+const scratches: Scratch[] = [];
+afterEach(() => { while (scratches.length) fs.rmSync(scratches.pop()!.root, { recursive: true, force: true }); });
+
+function sh(cwd: string, env: Record<string, string>, args: string[]): string {
+  const r = spawnSync('git', args, { cwd, encoding: 'utf8', timeout: 30_000, env: { ...process.env, ...env } });
+  if (r.status !== 0) throw new Error(`git ${args.join(' ')}: ${r.stderr}`);
+  return (r.stdout ?? '').trim();
+}
+
+/** A bare origin with main carrying the given base files, and a clone on branch `results`. */
+function scratch(baseFiles: Record<string, string | Buffer>): Scratch {
+  const root = fs.realpathSync(fs.mkdtempSync(path.join(os.tmpdir(), 'sealed-guard-')));
+  const work = path.join(root, 'work'); const origin = path.join(root, 'origin.git'); const state = path.join(root, 'state');
+  fs.mkdirSync(work); fs.mkdirSync(state);
+  const env = { HOME: root, GSTACK_HOME: state, GSTACK_STATE_ROOT: state, GIT_CONFIG_GLOBAL: path.join(root, 'gitconfig'), GIT_CONFIG_NOSYSTEM: '1' };
+  fs.writeFileSync(env.GIT_CONFIG_GLOBAL, '[user]\n\tname = t\n\temail = t@example.com\n[commit]\n\tgpgsign = false\n[init]\n\tdefaultBranch = main\n');
+  spawnSync('git', ['init', '-q', '--bare', origin], { env: { ...process.env, ...env } });
+  sh(work, env, ['init', '-q', '-b', 'main']);
+  write(work, { 'README.md': '# evals\n', ...baseFiles });
+  sh(work, env, ['add', '-A']); sh(work, env, ['commit', '-q', '-m', 'base']);
+  sh(work, env, ['remote', 'add', 'origin', origin]);
+  sh(work, env, ['push', '-q', 'origin', 'main']);
+  sh(work, env, ['remote', 'set-head', 'origin', 'main']);
+  sh(work, env, ['checkout', '-q', '-b', 'results']);
+  const s = { root, work, origin, state, env };
+  scratches.push(s);
+  return s;
+}
+function write(work: string, files: Record<string, string | Buffer | null>): void {
+  for (const [rel, body] of Object.entries(files)) {
+    const abs = path.join(work, rel);
+    if (body === null) { fs.rmSync(abs, { force: true }); continue; }
+    fs.mkdirSync(path.dirname(abs), { recursive: true });
+    fs.writeFileSync(abs, body);
+  }
+}
+function commit(s: Scratch, files: Record<string, string | Buffer | null>, msg = 'results'): string {
+  write(s.work, files);
+  sh(s.work, s.env, ['add', '-A']); sh(s.work, s.env, ['commit', '-q', '-m', msg]);
+  return sh(s.work, s.env, ['rev-parse', 'HEAD']);
+}
+const policy = (sealed: unknown) => JSON.stringify({ sealed }, null, 2) + '\n';
+
+/** Drive the hook exactly as git does for `git push origin results` (a new remote branch). */
+function hook(s: Scratch, extraEnv: Record<string, string> = {}) {
+  const head = sh(s.work, s.env, ['rev-parse', 'HEAD']);
+  const r = spawnSync('bun', [PREPUSH, 'origin', s.origin], { cwd: s.work, input: `refs/heads/results ${head} refs/heads/results ${ZERO}\n`, encoding: 'utf8', timeout: 60_000, env: { ...process.env, ...s.env, ...extraEnv } });
+  return { code: r.status, err: r.stderr ?? '' };
+}
+
+describe('pre-push hook: public destination refuses each kind of sealed output', () => {
+  test('a transcript, a sealed answer, a seed and a local home path each refuse, naming file, line and rule, never the matched text', () => {
+    const cases: Array<[Record<string, string | Buffer>, string, RegExp]> = [
+      [{ 'runs/cat40/cell-07/transcript.jsonl': '{"q":"x"}\n' }, 'sealed.transcript', /sealed\.transcript\s+runs\/cat40\/cell-07\/transcript\.jsonl/],
+      [{ 'runs/cat40/summary.md': 'intro\nSEALED ANSWER: fund-a led the round\n' }, 'sealed.answer', /sealed\.answer\s+runs\/cat40\/summary\.md:2/],
+      [{ 'runs/cat40/summary.md': 'run with shuffle_seed=42\n' }, 'sealed.seed', /sealed\.seed\s+runs\/cat40\/summary\.md:1/],
+      [{ 'runs/cat40/summary.md': 'raw at /home/user/.capy/work/evals/raw.jsonl\n' }, 'sealed.local_path', /sealed\.local_path\s+runs\/cat40\/summary\.md:1/],
+    ];
+    for (const [files, rule, where] of cases) {
+      const s = scratch({ '.gstack/pregate.json': policy(SEALED) });
+      commit(s, files);
+      const r = hook(s);
+      expect(r.code).toBe(1);
+      expect(r.err).toMatch(where);
+      expect(r.err).toContain(rule);
+      expect(r.err).toContain('(SEALED_OUTPUT_REFUSED)');
+      expect(r.err).toContain('sealed.visibility');
+      expect(r.err).not.toContain('fund-a led');
+    }
+  });
+
+  test('path rules ignore content: a binary file, an empty transcript, an add-then-delete and a rename into a sealed path all refuse', () => {
+    const binary = scratch({ '.gstack/pregate.json': policy(SEALED) });
+    commit(binary, { 'heldout/questions.bin': Buffer.from([0, 1, 2, 0, 255, 0]) });
+    expect(hook(binary).err).toMatch(/sealed\.path\s+heldout\/questions\.bin/);
+    const empty = scratch({ '.gstack/pregate.json': policy(SEALED) });
+    commit(empty, { 'runs/c1/transcript.jsonl': '' });
+    expect(hook(empty).code).toBe(1);
+    const gone = scratch({ '.gstack/pregate.json': policy(SEALED) });
+    const added = commit(gone, { 'runs/c1/transcript.jsonl': '{"q":1}\n' });
+    commit(gone, { 'runs/c1/transcript.jsonl': null }, 'remove it again');
+    const g = hook(gone);
+    expect(g.code).toBe(1);
+    expect(g.err).toContain(`sealed.transcript  runs/c1/transcript.jsonl  commit ${added.slice(0, 12)}`);
+    const moved = scratch({ '.gstack/pregate.json': policy(SEALED) });
+    commit(moved, { 'scratch/t.jsonl': '{"q":1}\n{"q":2}\n{"q":3}\n' });
+    fs.mkdirSync(path.join(moved.work, 'heldout'));
+    sh(moved.work, moved.env, ['mv', 'scratch/t.jsonl', 'heldout/t.jsonl']);
+    sh(moved.work, moved.env, ['commit', '-q', '-m', 'move']);
+    expect(hook(moved).err).toMatch(/sealed\.path\s+heldout\/t\.jsonl/);
+  });
+
+  test('commits the destination already has are not this push: a branch from main that only adds a doc passes', () => {
+    const s = scratch({ 'runs/old/transcript.jsonl': '{"q":"published before the policy"}\n', '.gstack/pregate.json': policy(SEALED) });
+    commit(s, { 'docs/notes.md': 'notes\n' });
+    const r = hook(s);
+    expect(r.code).toBe(0);
+    expect(r.err).not.toContain('sealed.');
+  });
+});
+
+describe('policy union, waivers, private destinations and fail-closed parsing', () => {
+  test('a push can tighten the policy but never relax it: dropping the base sealed config does not let a transcript through', () => {
+    const s = scratch({ '.gstack/pregate.json': policy(SEALED) });
+    commit(s, { '.gstack/pregate.json': '{}\n', 'runs/c1/transcript.jsonl': '{}\n' });
+    expect(hook(s).code).toBe(1);
+    const tighten = scratch({ '.gstack/pregate.json': policy(SEALED) });
+    commit(tighten, { '.gstack/pregate.json': policy({ ...SEALED, paths: ['heldout/**', 'cells/**'] }), 'cells/c1.json': '{}\n' });
+    expect(hook(tighten).err).toMatch(/sealed\.path\s+cells\/c1\.json/);
+  });
+
+  test('a waiver counts only from the base branch allow file and is listed; the same line committed in the push is ignored', () => {
+    const s = scratch({ '.gstack/pregate.json': policy(SEALED) });
+    const sha = commit(s, { 'runs/c1/transcript.jsonl': '{}\n' });
+    const allow = `# rule\tpath\tsha\treason\nsealed.transcript\truns/c1/transcript.jsonl\t${sha.slice(0, 12)}\tsynthetic fixture, no sealed content\n`;
+    commit(s, { '.gstack/sealed-allow.tsv': allow });
+    expect(hook(s).code).toBe(1);
+    sh(s.work, s.env, ['checkout', '-q', 'main']);
+    write(s.work, { '.gstack/sealed-allow.tsv': allow });
+    sh(s.work, s.env, ['add', '-A']); sh(s.work, s.env, ['commit', '-q', '-m', 'allow']); sh(s.work, s.env, ['push', '-q', 'origin', 'main']);
+    sh(s.work, s.env, ['checkout', '-q', 'results']);
+    const r = hook(s);
+    expect(r.code).toBe(0);
+    expect(r.err).toContain('waived sealed.transcript  runs/c1/transcript.jsonl');
+  });
+
+  test('a private destination (base override) warns and passes; a repo without the key sees no change; a malformed sealed policy refuses', () => {
+    const priv = scratch({ '.gstack/pregate.json': policy({ ...SEALED, visibility: 'private' }) });
+    commit(priv, { 'runs/c1/transcript.jsonl': '{}\n' });
+    const p = hook(priv);
+    expect(p.code).toBe(0);
+    expect(p.err).toMatch(/warning.*sealed\.transcript\s+runs\/c1\/transcript\.jsonl/s);
+    const none = scratch({});
+    commit(none, { 'runs/c1/transcript.jsonl': '{}\n' });
+    const n = hook(none);
+    expect(n.code).toBe(0);
+    expect(n.err).not.toContain('sealed');
+    const bad = scratch({ '.gstack/pregate.json': policy(SEALED) });
+    commit(bad, { '.gstack/pregate.json': policy({ paths: 'heldout/**' }), 'docs/x.md': 'x\n' });
+    const b = hook(bad);
+    expect(b.code).toBe(1);
+    expect(b.err).toContain('(SEALED_OUTPUT_REFUSED)');
+    expect(b.err).toContain('sealed policy');
+  });
+});
+
+describe('gstack-pregate sealed (the standalone preflight before any push or PR creation)', () => {
+  test('--range refuses the same findings with exit 1; the default range is what origin does not have yet', () => {
+    const s = scratch({ '.gstack/pregate.json': policy(SEALED) });
+    commit(s, { 'runs/c1/transcript.jsonl': '{}\n' });
+    const run = (args: string[]) => spawnSync(PREGATE, ['sealed', ...args], { cwd: s.work, encoding: 'utf8', timeout: 60_000, env: { ...process.env, ...s.env } });
+    const ranged = run(['--range', 'origin/main..HEAD', '--base', 'main']);
+    expect(ranged.status).toBe(1);
+    expect(ranged.stderr).toMatch(/sealed\.transcript\s+runs\/c1\/transcript\.jsonl/);
+    expect(ranged.stdout).toMatch(/^SEALED: refused findings=1 commits=1 visibility=unknown \(counted public\)/m);
+    const dflt = run(['--base', 'main']);
+    expect(dflt.status).toBe(1);
+    sh(s.work, s.env, ['push', '-q', 'origin', 'results']);
+    const after = run(['--base', 'main']);
+    expect(after.status).toBe(0);
+    expect(after.stdout).toMatch(/^SEALED: clear findings=0 commits=0/m);
+  });
+});
+
+describe('visibility (cache under the state root; unknown counts as public)', () => {
+  test('a public answer is cached; a cached private answer older than an hour is re-queried before it can downgrade; a failed lookup is unknown', () => {
+    const state = fs.mkdtempSync(path.join(os.tmpdir(), 'sealed-vis-'));
+    try {
+      let calls = 0;
+      let answer: string | null = 'PUBLIC';
+      const gh = () => { calls += 1; return answer === null ? { ok: false, out: '' } : { ok: true, out: JSON.stringify({ visibility: answer }) }; };
+      const env = { GSTACK_STATE_ROOT: state };
+      const t0 = Date.parse('2026-10-12T00:00:00Z');
+      expect(resolveVisibility('https://github.com/acme-example/evals.git', { env, gh, now: t0 }).visibility).toBe('public');
+      expect(resolveVisibility('https://github.com/acme-example/evals.git', { env, gh, now: t0 + 60_000 }).visibility).toBe('public');
+      expect(calls).toBe(1);
+      answer = 'PRIVATE';
+      expect(resolveVisibility('git@github.com:acme-example/private-evals.git', { env, gh, now: t0 }).visibility).toBe('private');
+      expect(resolveVisibility('git@github.com:acme-example/private-evals.git', { env, gh, now: t0 + 30 * 60_000 }).visibility).toBe('private');
+      expect(calls).toBe(2);
+      answer = null;
+      const stale = resolveVisibility('git@github.com:acme-example/private-evals.git', { env, gh, now: t0 + 2 * 3600_000 });
+      expect(calls).toBe(3);
+      expect(stale.visibility).toBe('unknown');
+      expect(resolveVisibility('/srv/git/evals.git', { env, gh, now: t0 }).visibility).toBe('unknown');
+      expect(calls).toBe(3);
+      expect(fs.existsSync(path.join(state, 'sealed-visibility.json'))).toBe(true);
+    } finally { fs.rmSync(state, { recursive: true, force: true }); }
+  });
+});