diff --git a/.github/workflows/_process-resume.yml b/.github/workflows/_process-resume.yml
index bd63cede..8462221a 100644
--- a/.github/workflows/_process-resume.yml
+++ b/.github/workflows/_process-resume.yml
@@ -54,7 +54,11 @@ jobs:
           SHA: ${{ github.event.workflow_run.head_sha }}
           EVENT: ${{ github.event.workflow_run.event }}
           STATUS: ${{ github.event.workflow_run.status }}
+        # #751: без pipefail код конвейера — код tee, и исключение скрипта (gh,
+        # API) проходило зелёным шагом: событие возобновления терялось до
+        # прохода process-reconcile.
         run: |
+          set -o pipefail
           node scripts/process-resume.mjs \
             --repo="$REPO" --branch="$BRANCH" --sha="$SHA" \
             --event="$EVENT" --status="$STATUS" --apply=true | tee -a "$GITHUB_STEP_SUMMARY"
diff --git a/.github/workflows/release-review.yml b/.github/workflows/release-review.yml
index cd916378..8beda322 100644
--- a/.github/workflows/release-review.yml
+++ b/.github/workflows/release-review.yml
@@ -75,6 +75,9 @@ jobs:
           FORCE: ${{ inputs.force }}
           RUN_URL: ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}
         run: |
+          # Отказ prepare за `| tee` не должен идти дальше с неполным
+          # GITHUB_OUTPUT и proceed=true (#751).
+          set -o pipefail
           doc=$(node scripts/release-review.mjs doc --tag="$TAG")
           git fetch -q --tags origin
           if [ -z "$CANDIDATE" ]; then
diff --git a/.github/workflows/validate.yml b/.github/workflows/validate.yml
index 849a69d0..8e6dbb16 100644
--- a/.github/workflows/validate.yml
+++ b/.github/workflows/validate.yml
@@ -368,7 +368,11 @@ jobs:
           FULL_INPUT: ${{ inputs.full }}
           MUTANTS_INPUT: ${{ inputs.mutants }}
           REF_NAME: ${{ github.ref_name }}
-        run: node scripts/classify-changes.mjs --heavy | tee -a "$GITHUB_OUTPUT"
+        # #751: без pipefail упавший classify-changes оставлял heavy пустым —
+        # тяжёлые job молча пропускались, а job changes зеленела.
+        run: |
+          set -o pipefail
+          node scripts/classify-changes.mjs --heavy | tee -a "$GITHUB_OUTPUT"
       - id: base
         if: github.event_name != 'pull_request'
         env:
diff --git a/scripts/ci-proof.mjs b/scripts/ci-proof.mjs
index ebb0a5ee..30787624 100644
--- a/scripts/ci-proof.mjs
+++ b/scripts/ci-proof.mjs
@@ -495,23 +495,32 @@ const apiHeaders = (token) => ({
   'User-Agent': 'houseplan-ci-proof', 'X-GitHub-Api-Version': '2022-11-28',
 });
 
+/**
+ * База REST API (#751): `GITHUB_API_URL`, как у раннера, без хвостового `/`.
+ * На github.com это тот же `https://api.github.com`; на GHES — `…/api/v3`.
+ * `archive_download_url` приходит из API абсолютным и базу не берёт.
+ */
+export const githubApiBase = (env = process.env) => String(env.GITHUB_API_URL || 'https://api.github.com').replace(/\/+$/, '');
+
 async function githubJson(url, token, fetchImpl) {
   const response = await fetchImpl(url, { headers: apiHeaders(token) });
   if (!response.ok) throw new Error(`GitHub API ${response.status}: ${await response.text()}`);
   return response.json();
 }
 
-export async function githubCandidateTree({ repo, sha, token, fetchImpl = fetch }) {
-  const row = await githubJson(`https://api.github.com/repos/${repo}/git/commits/${sha}`, token, fetchImpl);
+export async function githubCandidateTree({ repo, sha, token, fetchImpl = fetch, apiBase = githubApiBase() }) {
+  const row = await githubJson(`${apiBase}/repos/${repo}/git/commits/${sha}`, token, fetchImpl);
   return row?.tree?.sha || null;
 }
 
-export async function loadGithubProofContext({ repo, run, token, fetchImpl = fetch, withReviewedRun = false }) {
+export async function loadGithubProofContext({
+  repo, run, token, fetchImpl = fetch, withReviewedRun = false, apiBase = githubApiBase(),
+}) {
   const runId = runIdOf(run);
   const attempt = runAttemptOf(run);
   const name = ciProofArtifactName(runId, attempt);
   const list = await githubJson(
-    `https://api.github.com/repos/${repo}/actions/runs/${runId}/artifacts?name=${encodeURIComponent(name)}`,
+    `${apiBase}/repos/${repo}/actions/runs/${runId}/artifacts?name=${encodeURIComponent(name)}`,
     token, fetchImpl,
   );
   const artifact = (list?.artifacts || []).find((item) => item.name === name && !item.expired);
@@ -522,7 +531,7 @@ export async function loadGithubProofContext({ repo, run, token, fetchImpl = fet
     proof = readCiProofArtifact(Buffer.from(await response.arrayBuffer()));
   }
   const jobsBody = await githubJson(
-    `https://api.github.com/repos/${repo}/actions/runs/${runId}/jobs?per_page=100`, token, fetchImpl,
+    `${apiBase}/repos/${repo}/actions/runs/${runId}/jobs?per_page=100`, token, fetchImpl,
   );
   const jobs = jobsBody?.jobs || [];
   const reuseRuns = new Map();
@@ -532,10 +541,10 @@ export async function loadGithubProofContext({ repo, run, token, fetchImpl = fet
     const sourceKey = reuseSourceKey(sourceId, sourceAttempt);
     if (!sourceId || !sourceAttempt || reuseRuns.has(sourceKey)) continue;
     const sourceRun = await githubJson(
-      `https://api.github.com/repos/${repo}/actions/runs/${sourceId}/attempts/${sourceAttempt}`, token, fetchImpl,
+      `${apiBase}/repos/${repo}/actions/runs/${sourceId}/attempts/${sourceAttempt}`, token, fetchImpl,
     );
     const sourceJobs = await githubJson(
-      `https://api.github.com/repos/${repo}/actions/runs/${sourceId}/attempts/${sourceAttempt}/jobs?per_page=100`,
+      `${apiBase}/repos/${repo}/actions/runs/${sourceId}/attempts/${sourceAttempt}/jobs?per_page=100`,
       token, fetchImpl,
     );
     reuseRuns.set(sourceKey, { run: sourceRun, jobs: sourceJobs?.jobs || [] });
@@ -547,7 +556,7 @@ export async function loadGithubProofContext({ repo, run, token, fetchImpl = fet
   const declared = proof?.evidence?.baselines?.reviewedRun;
   if (withReviewedRun && declared) {
     try {
-      reviewedRun = { run: await githubJson(`https://api.github.com/repos/${repo}/actions/runs/${declared}`, token, fetchImpl) };
+      reviewedRun = { run: await githubJson(`${apiBase}/repos/${repo}/actions/runs/${declared}`, token, fetchImpl) };
     } catch {
       reviewedRun = null;
     }
diff --git a/scripts/night-red.mjs b/scripts/night-red.mjs
index 4a0b82d5..1f0d0c1d 100644
--- a/scripts/night-red.mjs
+++ b/scripts/night-red.mjs
@@ -36,7 +36,7 @@ import { isMainModule } from './spawn-portable.mjs';
 import { classify } from './change-classes.mjs';
 import { issueTrailers } from './release-membership.mjs';
 import { hasReleaseTrailer } from './ship-review.mjs';
-import { CI_PROOF_POLICIES, evaluateCiProof, loadGithubProofContext } from './ci-proof.mjs';
+import { CI_PROOF_POLICIES, evaluateCiProof, githubApiBase, loadGithubProofContext } from './ci-proof.mjs';
 
 /** Сколько последних dispatch-прогонов Validate на `dev` смотрит поиск `G`. */
 export const RUN_WINDOW = 50;
@@ -44,7 +44,6 @@ export const RUN_WINDOW = 50;
 export const LIST_LIMIT = 10;
 export const NIGHT_RED_MARKER_RE = /<!-- hp:night-red green=([0-9a-f]{40,64}) red=([0-9a-f]{40,64}) commits=([0-9a-f+]*) -->/g;
 
-const GITHUB_API = 'https://api.github.com';
 const short = (sha, n) => String(sha || '').slice(0, n);
 const stamp = (run) => Date.parse(run?.created_at || '') || 0;
 const runUrl = (repo, run) => run?.html_url || `https://github.com/${repo}/actions/runs/${run?.id}`;
@@ -236,12 +235,15 @@ export function gitClient({ cwd } = {}) {
   };
 }
 
-/** Actions API: `token` — `github.token`; база — `GITHUB_API_URL`, как у раннера. */
-export function actionsClient({ repo, token, apiBase = GITHUB_API, fetchImpl = fetch }) {
-  const base = String(apiBase || GITHUB_API).replace(/\/+$/, '');
-  const fetchApi = (url, init) => fetchImpl(String(url).startsWith(GITHUB_API) ? base + String(url).slice(GITHUB_API.length) : url, init);
+/**
+ * Actions API: `token` — `github.token`; база — `GITHUB_API_URL`, как у раннера.
+ * #751: база идёт в `loadGithubProofContext` параметром — переписывать URL
+ * обёрткой над `fetch` больше незачем.
+ */
+export function actionsClient({ repo, token, apiBase = githubApiBase(), fetchImpl = fetch }) {
+  const base = String(apiBase || githubApiBase()).replace(/\/+$/, '');
   const json = async (path) => {
-    const response = await fetchApi(`${GITHUB_API}/repos/${repo}${path}`, {
+    const response = await fetchImpl(`${base}/repos/${repo}${path}`, {
       headers: {
         Accept: 'application/vnd.github+json', Authorization: `Bearer ${token}`,
         'User-Agent': 'houseplan-night-red', 'X-GitHub-Api-Version': '2022-11-28',
@@ -256,7 +258,7 @@ export function actionsClient({ repo, token, apiBase = GITHUB_API, fetchImpl = f
       ?.workflow_runs || [],
     failedJobs: async (id) => ((await json(`/actions/runs/${id}/jobs?per_page=100`))?.jobs || [])
       .filter((job) => job?.conclusion === 'failure').map((job) => job.name),
-    proofContext: (run) => loadGithubProofContext({ repo, run, token, fetchImpl: fetchApi }),
+    proofContext: (run) => loadGithubProofContext({ repo, run, token, fetchImpl, apiBase: base }),
   };
 }
 
@@ -284,7 +286,7 @@ if (isMainModule(import.meta.url)) {
     if (!/^[1-9]\d*$/.test(redRunId)) throw new Error(`--red-run=<id прогона> обязателен, получено «${redRunId}»`);
     const result = await nightRed({
       repo, redRunId,
-      api: actionsClient({ repo, token: process.env.ACTIONS_TOKEN || '', apiBase: process.env.GITHUB_API_URL || GITHUB_API }),
+      api: actionsClient({ repo, token: process.env.ACTIONS_TOKEN || '', apiBase: githubApiBase() }),
       issues: ghIssues({ repo }),
       git: gitClient(),
     });
diff --git a/scripts/release-gate.mjs b/scripts/release-gate.mjs
index 2f0b2f7d..c987c0ed 100644
--- a/scripts/release-gate.mjs
+++ b/scripts/release-gate.mjs
@@ -5,7 +5,7 @@ import { execFileSync } from 'node:child_process';
 import { resolve } from 'node:path';
 import { fileURLToPath } from 'node:url';
 import {
-  CI_PROOF_POLICIES, evaluateCiProof, githubCandidateTree, localEvidence,
+  CI_PROOF_POLICIES, evaluateCiProof, githubApiBase, githubCandidateTree, localEvidence,
   loadGithubProofContext, selectCiProofVerdict,
 } from './ci-proof.mjs';
 
@@ -85,8 +85,9 @@ export async function classifyValidateProofs({
   return selectCiProofVerdict(evaluations);
 }
 
-export const workflowRunsUrl = ({ repo, workflow, sha }) => (
-  `https://api.github.com/repos/${repo}/actions/workflows/${encodeURIComponent(workflow)}`
+// #751: база — `GITHUB_API_URL` раннера (githubApiBase), не зашитый api.github.com.
+export const workflowRunsUrl = ({ repo, workflow, sha, apiBase = githubApiBase() }) => (
+  `${apiBase}/repos/${repo}/actions/workflows/${encodeURIComponent(workflow)}`
   + `/runs?head_sha=${encodeURIComponent(sha)}&per_page=100`
 );
 
diff --git a/test/ci-proof.test.mjs b/test/ci-proof.test.mjs
index e2ee23fe..d3b710e1 100644
--- a/test/ci-proof.test.mjs
+++ b/test/ci-proof.test.mjs
@@ -5,7 +5,8 @@ import { deflateRawSync } from 'node:zlib';
 import { fileURLToPath } from 'node:url';
 
 import {
-  CI_PROOF_POLICIES, MUTANT_JOB_PREFIX, baselineReviewedRun, buildCiProof, evaluateCiProof, loadGithubProofContext, localEvidence,
+  CI_PROOF_POLICIES, MUTANT_JOB_PREFIX, baselineReviewedRun, buildCiProof, evaluateCiProof, githubApiBase, githubCandidateTree,
+  loadGithubProofContext, localEvidence,
   parseReuseMarker, productTreeId, readCiProofArtifact, requiredCheckIds, selectCiProofVerdict,
 } from '../scripts/ci-proof.mjs';
 import { REUSE_JOBS } from '../scripts/check-inputs.mjs';
@@ -442,6 +443,63 @@ test('#573 r1 M1: reviewed run спрашивается у GitHub только 
   assert.ok(urls.some((url) => url.endsWith('/actions/runs/34853080375')), 'release спрашивает объявленный run');
 });
 
+// #751: база REST API — `GITHUB_API_URL` раннера, а не зашитый api.github.com.
+// На github.com раннер даёт тот же адрес; на GHES — `…/api/v3`.
+const GHE = 'https://ghe.example/api/v3';
+
+/** `GITHUB_API_URL` процесса на время `body`; прежнее значение возвращается. */
+async function withApiUrl(value, body) {
+  const before = process.env.GITHUB_API_URL;
+  if (value === undefined) delete process.env.GITHUB_API_URL; else process.env.GITHUB_API_URL = value;
+  try { return await body(); } finally {
+    if (before === undefined) delete process.env.GITHUB_API_URL; else process.env.GITHUB_API_URL = before;
+  }
+}
+
+test('#751 AC2: githubApiBase — GITHUB_API_URL без хвостового /, без него — api.github.com', () => {
+  assert.equal(githubApiBase({}), 'https://api.github.com');
+  assert.equal(githubApiBase({ GITHUB_API_URL: '' }), 'https://api.github.com');
+  assert.equal(githubApiBase({ GITHUB_API_URL: `${GHE}/` }), GHE);
+  assert.equal(githubApiBase({ GITHUB_API_URL: 'https://api.github.com' }), 'https://api.github.com');
+});
+
+test('#751 AC2: loadGithubProofContext и githubCandidateTree ходят в apiBase; ссылка на архив — как отдал API', async () => {
+  const proof = {
+    reusedChecks: ['unit'], checks: { unit: { reuse: { sourceRun: 11, sourceAttempt: 2 } } },
+    evidence: { baselines: { reviewedRun: 99 } },
+  };
+  const archive = 'https://objects.example/artifacts/7/zip';
+  const urls = [];
+  const fetchImpl = async (url) => {
+    urls.push(String(url));
+    if (url === archive) return { ok: true, arrayBuffer: async () => zipWith(proof) };
+    if (/\/artifacts\?name=/.test(url)) return { ok: true, json: async () => ({ artifacts: [{ name: 'ci-proof-20-1', expired: false, archive_download_url: archive }] }) };
+    if (/\/jobs\?/.test(url)) return { ok: true, json: async () => ({ jobs: [] }) };
+    if (/\/git\/commits\//.test(url)) return { ok: true, json: async () => ({ tree: { sha: TREE } }) };
+    return { ok: true, json: async () => ({ id: 1 }) };
+  };
+  const run = { id: 20, run_attempt: 1 };
+  await loadGithubProofContext({ repo: 'x/y', run, token: 't', fetchImpl, withReviewedRun: true, apiBase: GHE });
+  assert.equal(await githubCandidateTree({ repo: 'x/y', sha: SHA, token: 't', fetchImpl, apiBase: GHE }), TREE);
+  assert.deepEqual(urls, [
+    `${GHE}/repos/x/y/actions/runs/20/artifacts?name=ci-proof-20-1`,
+    archive,
+    `${GHE}/repos/x/y/actions/runs/20/jobs?per_page=100`,
+    `${GHE}/repos/x/y/actions/runs/11/attempts/2`,
+    `${GHE}/repos/x/y/actions/runs/11/attempts/2/jobs?per_page=100`,
+    `${GHE}/repos/x/y/actions/runs/99`,
+    `${GHE}/repos/x/y/git/commits/${SHA}`,
+  ]);
+  // Без параметра база — из окружения в момент вызова.
+  urls.length = 0;
+  await withApiUrl(`${GHE}/`, () => githubCandidateTree({ repo: 'x/y', sha: SHA, token: 't', fetchImpl }));
+  await withApiUrl(undefined, () => githubCandidateTree({ repo: 'x/y', sha: SHA, token: 't', fetchImpl }));
+  await withApiUrl(`${GHE}/`, () => loadGithubProofContext({ repo: 'x/y', run, token: 't', fetchImpl }));
+  assert.equal(urls[0], `${GHE}/repos/x/y/git/commits/${SHA}`);
+  assert.equal(urls[1], `https://api.github.com/repos/x/y/git/commits/${SHA}`);
+  assert.equal(urls[2], `${GHE}/repos/x/y/actions/runs/20/artifacts?name=ci-proof-20-1`);
+});
+
 test('#573: identity продуктового дерева не видит overlay эталонов, но видит всё остальное', () => {
   const lines = [
     '100644 blob 1111\tsrc/logic.ts',
diff --git a/test/night-red.test.mjs b/test/night-red.test.mjs
index 344519a5..6362e301 100644
--- a/test/night-red.test.mjs
+++ b/test/night-red.test.mjs
@@ -10,7 +10,7 @@ import { fileURLToPath } from 'node:url';
 import { buildCiProof } from '../scripts/ci-proof.mjs';
 import { jobInstanceNames, validateJobs } from '../scripts/workflow-jobs.mjs';
 import {
-  LIST_LIMIT, NIGHT_RED_MARKER_RE, commentBody, commentVerdict, countsForNightRed, findLastGreen, gitClient,
+  LIST_LIMIT, NIGHT_RED_MARKER_RE, actionsClient, commentBody, commentVerdict, countsForNightRed, findLastGreen, gitClient,
   nightRed, parseNightRedMarkers, rangeSuspects,
 } from '../scripts/night-red.mjs';
 
@@ -413,6 +413,34 @@ async function runNightStep(t, { cwd, items, issues = {}, fail = false, scripts
   return { status, stdout, stderr, requests: api.requests, log: text(files.log).split('\n').filter(Boolean), summary: text(files.summary), comment };
 }
 
+// #751: база API идёт в loadGithubProofContext параметром; обёртки над fetch,
+// переписывавшей префикс api.github.com, больше нет. Ссылку на архив
+// доказательства API отдаёт абсолютной — она не трогается.
+test('#751 AC2: actionsClient — прогоны, job и доказательство из apiBase, архив — по ссылке API', async () => {
+  const base = 'https://ghe.example/api/v3';
+  const archive = 'https://objects.example/artifacts/5/zip';
+  const urls = [];
+  const fetchImpl = async (url) => {
+    urls.push(String(url));
+    if (url === archive) return { ok: true, arrayBuffer: async () => zipWith({}) };
+    if (/\/artifacts\?name=/.test(url)) return { ok: true, json: async () => ({ artifacts: [{ name: 'ci-proof-5-1', expired: false, archive_download_url: archive }] }) };
+    return { ok: true, json: async () => ({ id: 5, workflow_runs: [], jobs: [] }) };
+  };
+  const api = actionsClient({ repo: REPO, token: 'actions-token', apiBase: `${base}/`, fetchImpl });
+  await api.run(5);
+  await api.runs();
+  await api.failedJobs(5);
+  await api.proofContext({ id: 5, run_attempt: 1 });
+  assert.deepEqual(urls, [
+    `${base}/repos/${REPO}/actions/runs/5`,
+    `${base}/repos/${REPO}/actions/workflows/validate.yml/runs?branch=dev&event=workflow_dispatch&per_page=50`,
+    `${base}/repos/${REPO}/actions/runs/5/jobs?per_page=100`,
+    `${base}/repos/${REPO}/actions/runs/5/artifacts?name=ci-proof-5-1`,
+    archive,
+    `${base}/repos/${REPO}/actions/runs/5/jobs?per_page=100`,
+  ]);
+});
+
 test('#736 AC2/AC3 на настоящем bash: шаг ночи читает Actions токеном ночи, пишет issue токеном процесса', async (t) => {
   if (!hasBash()) { t.skip('bash недоступен'); return; }
   const { cwd, sha } = history(t);
diff --git a/test/release-gate.test.mjs b/test/release-gate.test.mjs
index ee5ce011..8bd717c0 100644
--- a/test/release-gate.test.mjs
+++ b/test/release-gate.test.mjs
@@ -136,6 +136,21 @@ test('release gate can target the dedicated exact-SHA performance workflow', ()
   );
 });
 
+test('#751 AC2: workflowRunsUrl — база из apiBase или GITHUB_API_URL раннера', () => {
+  const args = { repo: 'Matysh/houseplan-card', workflow: 'validate.yml', sha: 'abc' };
+  const tail = '/repos/Matysh/houseplan-card/actions/workflows/validate.yml/runs?head_sha=abc&per_page=100';
+  assert.equal(workflowRunsUrl({ ...args, apiBase: 'https://ghe.example/api/v3' }), `https://ghe.example/api/v3${tail}`);
+  const before = process.env.GITHUB_API_URL;
+  try {
+    process.env.GITHUB_API_URL = 'https://ghe.example/api/v3/';
+    assert.equal(workflowRunsUrl(args), `https://ghe.example/api/v3${tail}`, 'без параметра — окружение раннера');
+    delete process.env.GITHUB_API_URL;
+    assert.equal(workflowRunsUrl(args), `https://api.github.com${tail}`, 'без GITHUB_API_URL — прежний адрес');
+  } finally {
+    if (before === undefined) delete process.env.GITHUB_API_URL; else process.env.GITHUB_API_URL = before;
+  }
+});
+
 test('#541: the release documents describe proof semantics', () => {
   const development = readFileSync(new URL('../docs/DEVELOPMENT.md', import.meta.url), 'utf8');
   assert.match(development, /requires a complete Validate proof for its SHA and\nGit tree/);
diff --git a/test/workflow-pipefail.test.mjs b/test/workflow-pipefail.test.mjs
new file mode 100644
index 00000000..e643306f
--- /dev/null
+++ b/test/workflow-pipefail.test.mjs
@@ -0,0 +1,145 @@
+// #751: у каждого `| tee` в workflow — pipefail.
+//
+// Ни один workflow не задаёт `shell:`, а шаг без него GitHub на Linux
+// исполняет как `bash -e {0}` — без pipefail (`-eo pipefail` даёт только явный
+// `shell: bash`). Код выхода `… | tee` — код tee, и падение левой части
+// проходило молча: `_process-resume.yml` терял событие возобновления,
+// `release-review.yml` шёл дальше с неполным GITHUB_OUTPUT и `proceed=true`,
+// `validate.yml` оставлял `heavy` пустым, и тяжёлые job пропускались. Образец —
+// #727 (`_ship-review.yml`) и #472 (`_mutation-gate.yml`). Контракт обходит все
+// `.github/workflows/*.yml`: строка с `| tee` в `run` либо идёт после
+// `set -o pipefail` (`set -[a-z]*o pipefail`), либо у шага стоит `shell: bash`.
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { spawnSync } from 'node:child_process';
+import { mkdirSync, mkdtempSync, readdirSync, readFileSync, rmSync, writeFileSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const WORKFLOWS = fileURLToPath(new URL('../.github/workflows/', import.meta.url));
+
+const indentOf = (line) => line.length - line.trimStart().length;
+const TEE = /(?<!\|)\|(?!\|)\s*tee\b/;
+const PIPEFAIL = /\bset\s+-[A-Za-z]*o\s+pipefail\b/;
+
+/**
+ * Все `run` файла: тело так, как его прочтёт YAML (блок `|`/`>` кончается на
+ * первой непустой строке с отступом не больше ключа), строка начала и `shell:`
+ * того же шага — ключ на том же отступе, что и `run`, в пределах элемента `- `.
+ */
+function runBlocks(text) {
+  const lines = text.split('\n');
+  const blocks = [];
+  lines.forEach((line, at) => {
+    const m = /^(\s*)(- )?run:\s*(.*)$/.exec(line);
+    if (!m) return;
+    const keyIndent = m[1].length + (m[2] ? 2 : 0);
+    const inline = !/^[|>][-+]?\s*(#.*)?$/.test(m[3]);
+    const body = [];
+    if (inline) body.push(m[3].replace(/^(['"])(.*)\1$/, '$2'));
+    else {
+      for (const next of lines.slice(at + 1)) {
+        if (next.trim() && indentOf(next) <= keyIndent) break;
+        body.push(next.trim() ? next.slice(keyIndent + 2) : '');
+      }
+    }
+    // Шаг — от своего `- ` (отступ ключа минус два) до первой строки левее ключей.
+    let start = at;
+    const item = new RegExp(`^ {${keyIndent - 2}}- `);
+    while (start > 0 && !item.test(lines[start])) start -= 1;
+    let end = at + 1;
+    while (end < lines.length && !(lines[end].trim() && indentOf(lines[end]) < keyIndent)) end += 1;
+    const keys = lines.slice(start, end).map((l, i) => (i === 0 ? l.replace(/^(\s*)- /, '$1  ') : l));
+    const shell = keys.find((l) => indentOf(l) === keyIndent && /^\s*shell:/.test(l))?.trim().slice('shell:'.length).trim() ?? '';
+    blocks.push({ line: at + 1, inline, body, shell });
+  });
+  return blocks;
+}
+
+/** Строки с `| tee`, перед которыми в том же `run` нет pipefail, а у шага — `shell: bash`. */
+function teeWithoutPipefail(text) {
+  const found = [];
+  for (const block of runBlocks(text)) {
+    if (/^bash\s*$/.test(block.shell) || /pipefail/.test(block.shell)) continue;
+    let guarded = false;
+    block.body.forEach((raw, i) => {
+      const code = raw.trimStart().startsWith('#') ? '' : raw;
+      const tee = code.search(TEE);
+      if (tee >= 0 && !guarded && !PIPEFAIL.test(code.slice(0, tee))) {
+        found.push({ line: block.inline ? block.line : block.line + 1 + i, text: raw.trim() });
+      }
+      if (PIPEFAIL.test(code)) guarded = true;
+    });
+  }
+  return found;
+}
+
+const workflowFiles = () => readdirSync(WORKFLOWS).filter((name) => /\.ya?ml$/.test(name)).sort();
+
+test('#751 AC1: разбор находит | tee без pipefail и пропускает защищённые', () => {
+  const step = (run, extra = '') => `jobs:\n  a:\n    steps:\n      - name: x\n${extra}        run: ${run}\n`;
+  const block = (...lines) => `|\n${lines.map((l) => `          ${l}`).join('\n')}`;
+  assert.equal(teeWithoutPipefail(step('node a.mjs | tee -a "$GITHUB_OUTPUT"')).length, 1, 'строка в одну строку');
+  assert.equal(teeWithoutPipefail(step(block('node a.mjs \\', '  --x=1 | tee out.txt'))).length, 1, 'блок без pipefail');
+  assert.equal(teeWithoutPipefail(step(block('set -o pipefail', 'node a.mjs | tee out.txt'))).length, 0);
+  assert.equal(teeWithoutPipefail(step(block('set -euo pipefail', 'node a.mjs | tee out.txt'))).length, 0, 'set -euo pipefail');
+  assert.equal(teeWithoutPipefail(step(block('node a.mjs | tee out.txt', 'set -o pipefail'))).length, 1, 'pipefail после tee не защищает');
+  assert.equal(teeWithoutPipefail(step(block('# set -o pipefail', 'node a.mjs | tee out.txt'))).length, 1, 'комментарий не защищает');
+  assert.equal(teeWithoutPipefail(step(block('# вывод идёт | tee в сводку', 'echo ok'))).length, 0, 'комментарий с | tee — не конвейер');
+  assert.equal(teeWithoutPipefail(step(block('a || tee x'))).length, 0, '|| — не конвейер');
+  assert.equal(teeWithoutPipefail(step(block('tee -a "$GITHUB_OUTPUT" < /tmp/x'))).length, 0, 'tee без конвейера');
+  assert.equal(teeWithoutPipefail(step('node a.mjs | tee out.txt', '        shell: bash\n')).length, 0, 'shell: bash даёт -eo pipefail');
+  assert.equal(teeWithoutPipefail(step('node a.mjs | tee out.txt', '        shell: bash -e {0}\n')).length, 1, 'свой shell без pipefail');
+  // shell соседнего шага — не этого.
+  const two = 'jobs:\n  a:\n    steps:\n      - name: x\n        shell: bash\n        run: echo\n      - name: y\n        run: node a.mjs | tee out.txt\n';
+  assert.deepEqual(teeWithoutPipefail(two).map((f) => f.text), ['node a.mjs | tee out.txt']);
+});
+
+test('#751 AC1: у каждого | tee во всех workflow — pipefail; пять известных мест видны разбору', () => {
+  const tees = new Set();
+  const offenders = [];
+  for (const name of workflowFiles()) {
+    const text = readFileSync(join(WORKFLOWS, name), 'utf8');
+    if (runBlocks(text).some((block) => block.body.some((line) => !line.trimStart().startsWith('#') && TEE.test(line)))) tees.add(name);
+    for (const found of teeWithoutPipefail(text)) offenders.push(`${name}:${found.line}: ${found.text}`);
+  }
+  for (const name of ['_mutation-gate.yml', '_ship-review.yml', '_process-resume.yml', 'release-review.yml', 'validate.yml']) {
+    assert.ok(tees.has(name), `${name}: | tee не найден — разбор ослеп`);
+  }
+  assert.deepEqual(offenders, [], 'добавить `set -o pipefail` первой строкой run (образец #727, #472)');
+});
+
+const hasBash = () => process.platform !== 'win32' && spawnSync('bash', ['--version']).status === 0;
+
+/** Тело `run` шага `name` файла `file` — как его исполнит раннер. */
+function stepRun(file, name) {
+  const text = readFileSync(join(WORKFLOWS, file), 'utf8');
+  const at = text.split('\n').findIndex((line) => line === `      - name: ${name}` || line === `      - id: ${name}`);
+  assert.ok(at >= 0, `шаг «${name}» в ${file}`);
+  const block = runBlocks(text).find((b) => b.line > at + 1);
+  assert.ok(block, `у шага «${name}» есть run`);
+  return block.body.join('\n');
+}
+
+test('#751 AC1 на настоящем bash: упавший скрипт слева от | tee роняет шаг под bash -e, как у раннера', (t) => {
+  if (!hasBash()) { t.skip('bash недоступен'); return; }
+  const root = mkdtempSync(join(tmpdir(), 'hp-751-tee-'));
+  t.after(() => rmSync(root, { recursive: true, force: true }));
+  const bin = join(root, 'bin');
+  mkdirSync(bin);
+  // Подменённый node: печатает строку, как скрипт до исключения, и выходит 1.
+  writeFileSync(join(bin, 'node'), '#!/bin/sh\necho "action=partial"\necho "boom: $*" >&2\nexit 1\n', { mode: 0o755 });
+  for (const [file, name] of [['_process-resume.yml', 'Решить по маркеру ожидания и переставить S7'], ['validate.yml', 'heavy']]) {
+    const out = join(root, `${file}.out`);
+    writeFileSync(out, '');
+    // Шаг без `shell:` GitHub исполняет как `bash -e {0}`.
+    const r = spawnSync('bash', ['--noprofile', '--norc', '-e', '-c', stepRun(file, name)], {
+      cwd: root, encoding: 'utf8',
+      env: { ...process.env, PATH: `${bin}:${process.env.PATH}`, GITHUB_STEP_SUMMARY: out, GITHUB_OUTPUT: out },
+    });
+    assert.notEqual(r.status, 0, `${file} «${name}»: падение скрипта прошло зелёным шагом`);
+    assert.match(r.stderr, /boom: scripts\//, `${file}: упал именно скрипт шага`);
+    assert.equal(readFileSync(out, 'utf8'), 'action=partial\n', `${file}: tee по-прежнему пишет вывод`);
+  }
+});