diff --git a/.gitea/scripts/gitea-merge-queue.py b/.gitea/scripts/gitea-merge-queue.py
new file mode 100644
index 0000000..67b5c95
--- /dev/null
+++ b/.gitea/scripts/gitea-merge-queue.py
@@ -0,0 +1,370 @@
+#!/usr/bin/env python3
+"""gitea-merge-queue — conservative serialized merge bot for Gitea.
+
+Gitea 1.22.6 has auto-merge (`pull_auto_merge`) but no GitHub-style merge
+queue. This script provides the missing serialized policy in user space:
+
+1. Pick the oldest open PR carrying QUEUE_LABEL.
+2. Refuse to act unless main is green.
+3. Refuse fork PRs; the queue may only mutate same-repo branches.
+4. If the PR branch does not contain current main, call Gitea's
+   /pulls/{n}/update endpoint and stop. CI must rerun on the updated head.
+5. If the updated PR head has all required contexts green, merge with the
+   non-bypass merge actor token.
+
+The script is intentionally one-PR-per-run. Workflow/cron concurrency should
+serialize invocations so two green PRs cannot merge against the same main.
+"""
+
+from __future__ import annotations
+
+import argparse
+import dataclasses
+import json
+import os
+import sys
+import urllib.error
+import urllib.parse
+import urllib.request
+from typing import Any
+
+
+def _env(key: str, *, default: str = "") -> str:
+    return os.environ.get(key, default)
+
+
+GITEA_TOKEN = _env("GITEA_TOKEN")
+GITEA_HOST = _env("GITEA_HOST")
+REPO = _env("REPO")
+WATCH_BRANCH = _env("WATCH_BRANCH", default="main")
+QUEUE_LABEL = _env("QUEUE_LABEL", default="merge-queue")
+HOLD_LABEL = _env("HOLD_LABEL", default="merge-queue-hold")
+UPDATE_STYLE = _env("UPDATE_STYLE", default="merge")
+REQUIRED_CONTEXTS_RAW = _env(
+    "REQUIRED_CONTEXTS",
+    default=(
+        "CI / all-required (pull_request),"
+        "sop-checklist / all-items-acked (pull_request)"
+    ),
+)
+
+OWNER, NAME = (REPO.split("/", 1) + [""])[:2] if REPO else ("", "")
+API = f"https://{GITEA_HOST}/api/v1" if GITEA_HOST else ""
+
+
+class ApiError(RuntimeError):
+    pass
+
+
+@dataclasses.dataclass(frozen=True)
+class MergeDecision:
+    ready: bool
+    action: str
+    reason: str
+
+
+def _require_runtime_env() -> None:
+    for key in ("GITEA_TOKEN", "GITEA_HOST", "REPO", "WATCH_BRANCH", "QUEUE_LABEL"):
+        if not os.environ.get(key):
+            sys.stderr.write(f"::error::missing required env var: {key}\n")
+            sys.exit(2)
+    if UPDATE_STYLE not in {"merge", "rebase"}:
+        sys.stderr.write("::error::UPDATE_STYLE must be merge or rebase\n")
+        sys.exit(2)
+
+
+def api(
+    method: str,
+    path: str,
+    *,
+    body: dict | None = None,
+    query: dict[str, str] | None = None,
+    expect_json: bool = True,
+) -> tuple[int, Any]:
+    url = f"{API}{path}"
+    if query:
+        url = f"{url}?{urllib.parse.urlencode(query)}"
+    data = None
+    headers = {
+        "Authorization": f"token {GITEA_TOKEN}",
+        "Accept": "application/json",
+    }
+    if body is not None:
+        data = json.dumps(body).encode("utf-8")
+        headers["Content-Type"] = "application/json"
+    req = urllib.request.Request(url, method=method, data=data, headers=headers)
+    try:
+        with urllib.request.urlopen(req, timeout=30) as resp:
+            raw = resp.read()
+            status = resp.status
+    except urllib.error.HTTPError as exc:
+        raw = exc.read()
+        status = exc.code
+
+    if not (200 <= status < 300):
+        snippet = raw[:500].decode("utf-8", errors="replace") if raw else ""
+        raise ApiError(f"{method} {path} -> HTTP {status}: {snippet}")
+    if not raw:
+        return status, None
+    try:
+        return status, json.loads(raw)
+    except json.JSONDecodeError as exc:
+        if expect_json:
+            raise ApiError(f"{method} {path} -> HTTP {status} non-JSON: {exc}") from exc
+        return status, {"_raw": raw.decode("utf-8", errors="replace")}
+
+
+def required_contexts(raw: str) -> list[str]:
+    return [part.strip() for part in raw.split(",") if part.strip()]
+
+
+def status_state(status: dict) -> str:
+    return str(status.get("status") or status.get("state") or "").lower()
+
+
+def latest_statuses_by_context(statuses: list[dict]) -> dict[str, dict]:
+    latest: dict[str, dict] = {}
+    for status in statuses:
+        context = status.get("context")
+        if isinstance(context, str) and context not in latest:
+            latest[context] = status
+    return latest
+
+
+def required_contexts_green(
+    latest_statuses: dict[str, dict],
+    contexts: list[str],
+) -> tuple[bool, list[str]]:
+    missing_or_bad: list[str] = []
+    for context in contexts:
+        status = latest_statuses.get(context)
+        state = status_state(status or {})
+        if state != "success":
+            missing_or_bad.append(f"{context}={state or 'missing'}")
+    return not missing_or_bad, missing_or_bad
+
+
+def label_names(issue: dict) -> set[str]:
+    return {
+        label["name"]
+        for label in issue.get("labels", [])
+        if isinstance(label, dict) and isinstance(label.get("name"), str)
+    }
+
+
+def choose_next_queued_issue(
+    issues: list[dict],
+    *,
+    queue_label: str,
+    hold_label: str = "",
+) -> dict | None:
+    candidates = []
+    for issue in issues:
+        labels = label_names(issue)
+        if queue_label not in labels:
+            continue
+        if hold_label and hold_label in labels:
+            continue
+        if "pull_request" not in issue:
+            continue
+        candidates.append(issue)
+    candidates.sort(key=lambda issue: (issue.get("created_at") or "", int(issue["number"])))
+    return candidates[0] if candidates else None
+
+
+def pr_contains_base_sha(commits: list[dict], base_sha: str) -> bool:
+    for commit in commits:
+        sha = commit.get("sha") or commit.get("id")
+        if sha == base_sha:
+            return True
+    return False
+
+
+def pr_has_current_base(pr: dict, commits: list[dict], main_sha: str) -> bool:
+    if pr.get("merge_base") == main_sha:
+        return True
+    return pr_contains_base_sha(commits, main_sha)
+
+
+def evaluate_merge_readiness(
+    *,
+    main_status: dict,
+    pr_status: dict,
+    required_contexts: list[str],
+    pr_has_current_base: bool,
+) -> MergeDecision:
+    main_state = str(main_status.get("state") or "").lower()
+    if main_state != "success":
+        return MergeDecision(False, "pause", f"main status is {main_state or 'missing'}")
+    if not pr_has_current_base:
+        return MergeDecision(False, "update", "PR head does not contain current main")
+
+    pr_state = str(pr_status.get("state") or "").lower()
+    if pr_state != "success":
+        return MergeDecision(False, "wait", f"PR combined status is {pr_state or 'missing'}")
+
+    latest = latest_statuses_by_context(pr_status.get("statuses") or [])
+    ok, missing_or_bad = required_contexts_green(latest, required_contexts)
+    if not ok:
+        return MergeDecision(False, "wait", "required contexts not green: " + ", ".join(missing_or_bad))
+    return MergeDecision(True, "merge", "ready")
+
+
+def get_branch_head(branch: str) -> str:
+    _, body = api("GET", f"/repos/{OWNER}/{NAME}/branches/{branch}")
+    commit = body.get("commit") if isinstance(body, dict) else None
+    sha = commit.get("id") if isinstance(commit, dict) else None
+    if not isinstance(sha, str) or len(sha) < 7:
+        raise ApiError(f"branch {branch} response missing commit id")
+    return sha
+
+
+def get_combined_status(sha: str) -> dict:
+    _, body = api("GET", f"/repos/{OWNER}/{NAME}/commits/{sha}/status")
+    if not isinstance(body, dict):
+        raise ApiError(f"status for {sha} response not object")
+    return body
+
+
+def list_queued_issues() -> list[dict]:
+    _, body = api(
+        "GET",
+        f"/repos/{OWNER}/{NAME}/issues",
+        query={
+            "state": "open",
+            "type": "pulls",
+            "labels": QUEUE_LABEL,
+            "limit": "50",
+        },
+    )
+    if not isinstance(body, list):
+        raise ApiError("queued issues response not list")
+    return body
+
+
+def get_pull(pr_number: int) -> dict:
+    _, body = api("GET", f"/repos/{OWNER}/{NAME}/pulls/{pr_number}")
+    if not isinstance(body, dict):
+        raise ApiError(f"PR #{pr_number} response not object")
+    return body
+
+
+def get_pull_commits(pr_number: int) -> list[dict]:
+    _, body = api("GET", f"/repos/{OWNER}/{NAME}/pulls/{pr_number}/commits")
+    if not isinstance(body, list):
+        raise ApiError(f"PR #{pr_number} commits response not list")
+    return body
+
+
+def post_comment(pr_number: int, body: str, *, dry_run: bool) -> None:
+    print(f"::notice::comment PR #{pr_number}: {body.splitlines()[0][:160]}")
+    if dry_run:
+        return
+    api("POST", f"/repos/{OWNER}/{NAME}/issues/{pr_number}/comments", body={"body": body})
+
+
+def update_pull(pr_number: int, *, dry_run: bool) -> None:
+    print(f"::notice::updating PR #{pr_number} with base branch via style={UPDATE_STYLE}")
+    if dry_run:
+        return
+    api(
+        "POST",
+        f"/repos/{OWNER}/{NAME}/pulls/{pr_number}/update",
+        query={"style": UPDATE_STYLE},
+        expect_json=False,
+    )
+
+
+def merge_pull(pr_number: int, *, dry_run: bool) -> None:
+    payload = {
+        "Do": "merge",
+        "MergeTitleField": f"Merge PR #{pr_number} via Gitea merge queue",
+        "MergeMessageField": (
+            "Serialized merge by gitea-merge-queue after current-main, "
+            "SOP, and required CI checks were green."
+        ),
+    }
+    print(f"::notice::merging PR #{pr_number}")
+    if dry_run:
+        return
+    api("POST", f"/repos/{OWNER}/{NAME}/pulls/{pr_number}/merge", body=payload, expect_json=False)
+
+
+def process_once(*, dry_run: bool = False) -> int:
+    contexts = required_contexts(REQUIRED_CONTEXTS_RAW)
+    main_sha = get_branch_head(WATCH_BRANCH)
+    main_status = get_combined_status(main_sha)
+    if str(main_status.get("state") or "").lower() != "success":
+        print(f"::notice::queue paused: {WATCH_BRANCH}@{main_sha[:8]} is not green")
+        return 0
+
+    issue = choose_next_queued_issue(
+        list_queued_issues(),
+        queue_label=QUEUE_LABEL,
+        hold_label=HOLD_LABEL,
+    )
+    if not issue:
+        print("::notice::merge queue empty")
+        return 0
+
+    pr_number = int(issue["number"])
+    pr = get_pull(pr_number)
+    if pr.get("state") != "open":
+        print(f"::notice::PR #{pr_number} is not open; skipping")
+        return 0
+    if pr.get("base", {}).get("ref") != WATCH_BRANCH:
+        post_comment(pr_number, f"merge-queue: skipped; base branch is not `{WATCH_BRANCH}`.", dry_run=dry_run)
+        return 0
+    if pr.get("head", {}).get("repo_id") != pr.get("base", {}).get("repo_id"):
+        post_comment(pr_number, "merge-queue: skipped; fork PRs are not supported by the serialized queue.", dry_run=dry_run)
+        return 0
+
+    head_sha = pr.get("head", {}).get("sha")
+    if not isinstance(head_sha, str) or len(head_sha) < 7:
+        raise ApiError(f"PR #{pr_number} missing head sha")
+    commits = get_pull_commits(pr_number)
+    current_base = pr_has_current_base(pr, commits, main_sha)
+    pr_status = get_combined_status(head_sha)
+    decision = evaluate_merge_readiness(
+        main_status=main_status,
+        pr_status=pr_status,
+        required_contexts=contexts,
+        pr_has_current_base=current_base,
+    )
+
+    print(f"::notice::PR #{pr_number} decision={decision.action}: {decision.reason}")
+    if decision.action == "update":
+        update_pull(pr_number, dry_run=dry_run)
+        post_comment(
+            pr_number,
+            (
+                f"merge-queue: updated this branch with `{WATCH_BRANCH}` at "
+                f"`{main_sha[:12]}`. Waiting for CI on the refreshed head."
+            ),
+            dry_run=dry_run,
+        )
+        return 0
+    if decision.ready:
+        latest_main_sha = get_branch_head(WATCH_BRANCH)
+        if latest_main_sha != main_sha:
+            print(
+                f"::notice::main moved {main_sha[:8]} -> {latest_main_sha[:8]}; "
+                "deferring to next tick"
+            )
+            return 0
+        merge_pull(pr_number, dry_run=dry_run)
+        return 0
+    return 0
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--dry-run", action="store_true")
+    args = parser.parse_args()
+    _require_runtime_env()
+    return process_once(dry_run=args.dry_run)
+
+
+if __name__ == "__main__":
+    sys.exit(main())
+
diff --git a/.gitea/workflows/gitea-merge-queue.yml b/.gitea/workflows/gitea-merge-queue.yml
index e12a273..0502e19 100644
--- a/.gitea/workflows/gitea-merge-queue.yml
+++ b/.gitea/workflows/gitea-merge-queue.yml
@@ -1,18 +1,39 @@
-name: Merge Queue
+name: gitea-merge-queue
+
+# External serialized merge queue for Gitea 1.22.6.
+# Uses AUTO_SYNC_TOKEN (devops-engineer persona PAT) as merge actor.
 
 on:
-  pull_request:
-    types: [labeled]
+  schedule:
+    - cron: '*/5 * * * *'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: gitea-merge-queue-${{ github.repository }}
+  cancel-in-progress: false
 
 jobs:
-  merge:
-    if: contains(github.event.pull_request.labels.*.name, 'merge-queue')
+  queue:
     runs-on: ubuntu-latest
+    timeout-minutes: 5
     steps:
-      - name: Merge PR
-        run: |
-          curl -X POST \
-            -H "Authorization: token ${{ secrets.GITEA_TOKEN }}" \
-            -H "Content-Type: application/json" \
-            "${{ github.api_url }}/repos/${{ github.repository }}/pulls/${{ github.event.pull_request.number }}/merge" \
-            -d '{"do":"merge","merge_when_checks_succeed":true}'
+      - name: Check out queue script from main
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          ref: ${{ github.event.repository.default_branch }}
+
+      - name: Process one queued PR
+        env:
+          GITEA_TOKEN: ${{ secrets.AUTO_SYNC_TOKEN }}
+          GITEA_HOST: git.moleculesai.app
+          REPO: ${{ github.repository }}
+          WATCH_BRANCH: ${{ github.event.repository.default_branch }}
+          QUEUE_LABEL: merge-queue
+          HOLD_LABEL: merge-queue-hold
+          UPDATE_STYLE: merge
+          REQUIRED_CONTEXTS: >-
+            CI / test (pull_request)
+        run: python3 .gitea/scripts/gitea-merge-queue.py