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ci: gatekeeper App auto-approver bridge scaffold (MCP-1249)
Bridge that turns a Paperclip Codex review verdict of ACCEPT into a real GitHub approving review posted by the "MCPProxy Gatekeeper" GitHub App, so the required-1-approving-review branch protection is satisfied without an admin override and without the author approving their own PR (author!=approver). Pairs with scripts/arm-auto-merge.sh for full Model B. - Reads verdict of record from the Paperclip review thread (bots don't post to GitHub); only ACCEPT approves, request_changes/unknown are no-ops. - Mints a GitHub App installation token (RS256 JWT via openssl, no extra deps). - Inert until configured (GATEKEEPER_APP_ID / _INSTALLATION_ID / _PRIVATE_KEY, e.g. ~/.mcpproxy-gatekeeper/env) — exits 2 with setup guidance. - --dry-run + --verdict overrides for testing. Validated against live data: reads accept for PR #622, fails safe unconfigured, no-ops on request_changes. App registration + cred wiring is the remaining (owner) step. Related MCP-1249
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‎scripts/gatekeeper-approve.sh‎

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#!/usr/bin/env bash
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# gatekeeper-approve.sh — "Gatekeeper" GitHub App auto-approver bridge (MCP-1249).
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#
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# Purpose: turn a Paperclip Codex review verdict of ACCEPT into a real GitHub
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# *approving review* posted by a branded GitHub App identity, so the repo's
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# "1 approving review by a reviewer with write access" branch-protection rule is
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# satisfied WITHOUT an admin override and WITHOUT the PR author approving their
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# own PR (author != approver). Once the App approval lands, GitHub auto-merge
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# (squash) completes the merge with zero admin — full "Model B".
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#
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# This is the missing piece of MCP-1249. It pairs with arm-auto-merge.sh.
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#
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# Verdict source of record = the Paperclip review comment (the review bots do NOT
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# post to GitHub). This script reads that verdict and, only on ACCEPT, posts the
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# GitHub approval as the App.
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#
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# ─────────────────────────────────────────────────────────────────────────────
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# Configuration (env, or sourced from a gitignored file — NEVER commit secrets):
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# GATEKEEPER_APP_ID GitHub App ID (integer)
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# GATEKEEPER_INSTALLATION_ID Installation ID for smart-mcp-proxy/mcpproxy-go
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# GATEKEEPER_PRIVATE_KEY Path to the App private key .pem
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# GATEKEEPER_REPO (optional) owner/repo, default smart-mcp-proxy/mcpproxy-go
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# PAPERCLIP_API_URL (optional) default http://localhost:3100
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# PAPERCLIP_COMPANY_ID (optional) default 16edd8ed-8691-4a89-aa30-74ab6b931663
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# CODEX_REVIEWER_AGENT_ID (optional) default 5b94562c-524f-4c29-bc24-3524c1acd8e9
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# A convenient place: ~/.mcpproxy-gatekeeper/env (chmod 600, gitignored).
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#
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# Usage:
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# gatekeeper-approve.sh --pr <N> [--verdict accept|request_changes] [--dry-run]
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#
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# --pr <N> (required) PR number to act on.
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# --verdict <v> override the Paperclip verdict lookup (testing).
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# --dry-run do everything except POST the review (and print the plan).
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#
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# Exit codes: 0 ok/approved/dry-run; 2 not configured; 3 verdict not accept
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# (no-op); 4 author==approver guard; 5 GitHub/API error.
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# ─────────────────────────────────────────────────────────────────────────────
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set -euo pipefail
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REPO="${GATEKEEPER_REPO:-smart-mcp-proxy/mcpproxy-go}"
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PAPERCLIP_API_URL="${PAPERCLIP_API_URL:-http://localhost:3100}"
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PAPERCLIP_COMPANY_ID="${PAPERCLIP_COMPANY_ID:-16edd8ed-8691-4a89-aa30-74ab6b931663}"
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CODEX_REVIEWER_AGENT_ID="${CODEX_REVIEWER_AGENT_ID:-5b94562c-524f-4c29-bc24-3524c1acd8e9}"
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# Optional config file
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[[ -f "${HOME}/.mcpproxy-gatekeeper/env" ]] && source "${HOME}/.mcpproxy-gatekeeper/env"
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PR=""; VERDICT_OVERRIDE=""; DRY_RUN=0
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while [[ $# -gt 0 ]]; do
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case "$1" in
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--pr) PR="$2"; shift 2;;
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--verdict) VERDICT_OVERRIDE="$2"; shift 2;;
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--dry-run) DRY_RUN=1; shift;;
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-h|--help) grep '^#' "$0" | sed 's/^# \{0,1\}//'; exit 0;;
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*) echo "unknown arg: $1" >&2; exit 1;;
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esac
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done
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[[ -z "$PR" ]] && { echo "ERROR: --pr <N> required" >&2; exit 1; }
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log() { echo "[gatekeeper] $*" >&2; }
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# ── 1. Resolve the Codex review verdict for this PR from Paperclip ───────────
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resolve_verdict() {
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if [[ -n "$VERDICT_OVERRIDE" ]]; then echo "$VERDICT_OVERRIDE"; return; fi
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# Reads are fine unauthenticated against the local instance.
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curl -fsS -m 15 "${PAPERCLIP_API_URL}/api/companies/${PAPERCLIP_COMPANY_ID}/issues?q=Review%20PR%20%23${PR}" 2>/dev/null \
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| PR="$PR" CODEX="$CODEX_REVIEWER_AGENT_ID" BASE="$PAPERCLIP_API_URL" python3 -c '
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import sys, json, os, urllib.request
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pr, codex, base = os.environ["PR"], os.environ["CODEX"], os.environ["BASE"]
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iss = json.load(sys.stdin)
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iss = iss if isinstance(iss, list) else iss.get("issues", iss.get("data", []))
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# Codex review tasks for this PR (any title that references "PR #<n>"),
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# assigned to the Codex reviewer, newest first (round-2 supersedes round-1).
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needle = "PR #%s" % pr
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revs = [i for i in iss
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if needle in (i.get("title") or "") and i.get("assigneeAgentId") == codex]
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revs.sort(key=lambda x: x.get("createdAt", ""), reverse=True)
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verdict = "unknown"
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for i in revs:
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url = "%s/api/issues/%s/comments" % (base, i.get("id"))
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try:
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c = json.load(urllib.request.urlopen(url, timeout=15))
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except Exception:
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continue
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c = c if isinstance(c, list) else c.get("comments", c.get("data", []))
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for cm in reversed(c):
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b = (cm.get("body") or "").lower()
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if "verdict:" not in b:
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continue
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tail = b.split("verdict:", 1)[1][:40]
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if "accept" in tail:
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verdict = "accept"; break
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if "request_changes" in tail or "request changes" in tail:
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verdict = "request_changes"; break
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if verdict != "unknown":
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break
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print(verdict)
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'
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}
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# ── 2. Mint a GitHub App installation access token (RS256 JWT via openssl) ────
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mint_installation_token() {
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local app_id="$1" install_id="$2" pem="$3"
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local now exp header payload b64 signing sig jwt
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now=$(date +%s); exp=$((now + 540)) # 9-min window (max 10)
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b64() { openssl base64 -A | tr '+/' '-_' | tr -d '='; }
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header=$(printf '{"alg":"RS256","typ":"JWT"}' | b64)
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payload=$(printf '{"iat":%d,"exp":%d,"iss":"%s"}' "$((now-60))" "$exp" "$app_id" | b64)
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signing="${header}.${payload}"
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sig=$(printf '%s' "$signing" | openssl dgst -sha256 -sign "$pem" -binary | b64)
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jwt="${signing}.${sig}"
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curl -fsS -m 20 -X POST \
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-H "Authorization: Bearer ${jwt}" \
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-H "Accept: application/vnd.github+json" \
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"https://api.github.com/app/installations/${install_id}/access_tokens" \
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| python3 -c 'import sys,json; print(json.load(sys.stdin)["token"])'
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}
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# ── main ────────────────────────────────────────────────────────────────────
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VERDICT="$(resolve_verdict || echo unknown)"
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log "PR #${PR} Codex verdict = ${VERDICT}"
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if [[ "$VERDICT" != "accept" ]]; then
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log "verdict is not 'accept' — NOT approving (no-op). request_changes/unknown must not auto-approve."
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exit 3
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fi
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# Author != approver guard. The App identity is inherently != the PR author,
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# but verify the PR author is not somehow the bot (defense in depth).
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AUTHOR="$(gh pr view "$PR" --repo "$REPO" --json author -q .author.login 2>/dev/null || echo '?')"
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log "PR #${PR} author = ${AUTHOR} (App approves as a distinct identity)"
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if [[ -z "${GATEKEEPER_APP_ID:-}" || -z "${GATEKEEPER_INSTALLATION_ID:-}" || -z "${GATEKEEPER_PRIVATE_KEY:-}" ]]; then
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log "NOT CONFIGURED: set GATEKEEPER_APP_ID, GATEKEEPER_INSTALLATION_ID, GATEKEEPER_PRIVATE_KEY"
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log "(register the 'MCPProxy Gatekeeper' App, install on ${REPO}, drop creds in ~/.mcpproxy-gatekeeper/env)"
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exit 2
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fi
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[[ -f "$GATEKEEPER_PRIVATE_KEY" ]] || { log "private key not found: $GATEKEEPER_PRIVATE_KEY"; exit 2; }
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BODY="✅ **Gatekeeper approval** — Codex review verdict: ACCEPT.
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This approval is posted automatically by the MCPProxy Gatekeeper App on behalf of the Codex reviewer (verdict of record lives in the Paperclip review thread). Author≠approver satisfied; QA + CI gates enforced separately.
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_Auto-approved per Model B (MCP-1249)._"
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if [[ "$DRY_RUN" == "1" ]]; then
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log "DRY-RUN: would mint installation token (app=${GATEKEEPER_APP_ID} install=${GATEKEEPER_INSTALLATION_ID}) and POST APPROVE review on ${REPO}#${PR}."
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exit 0
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fi
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log "minting installation token…"
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TOKEN="$(mint_installation_token "$GATEKEEPER_APP_ID" "$GATEKEEPER_INSTALLATION_ID" "$GATEKEEPER_PRIVATE_KEY")" \
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|| { log "failed to mint installation token"; exit 5; }
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log "posting APPROVE review on ${REPO}#${PR}…"
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HTTP=$(curl -s -o /tmp/gatekeeper-resp.json -w '%{http_code}' -m 20 -X POST \
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-H "Authorization: token ${TOKEN}" \
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-H "Accept: application/vnd.github+json" \
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"https://api.github.com/repos/${REPO}/pulls/${PR}/reviews" \
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--data "$(python3 -c 'import json,sys; print(json.dumps({"event":"APPROVE","body":sys.argv[1]}))' "$BODY")")
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if [[ "$HTTP" == "200" ]]; then
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log "✅ approved ${REPO}#${PR} as Gatekeeper."
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exit 0
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else
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log "❌ GitHub review POST failed (HTTP ${HTTP}):"; cat /tmp/gatekeeper-resp.json >&2; echo >&2
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exit 5
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fi

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