diff --git a/.github/workflows/update-links.yml b/.github/workflows/update-links.yml
new file mode 100644
index 0000000..c6b6f3f
--- /dev/null
+++ b/.github/workflows/update-links.yml
@@ -0,0 +1,26 @@
+name: Update download links
+
+on:
+  workflow_dispatch:
+  schedule:
+    - cron: "17 3 * * 1"
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  update:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.x"
+      - run: python scripts/update_links.py --write
+      - uses: peter-evans/create-pull-request@v6
+        with:
+          branch: automation/update-links
+          commit-message: Update download links
+          title: Update download links
+          body: Automated link maintenance.
diff --git a/scripts/update_links.py b/scripts/update_links.py
new file mode 100644
index 0000000..f02745e
--- /dev/null
+++ b/scripts/update_links.py
@@ -0,0 +1,813 @@
+import argparse
+import hashlib
+import json
+import re
+import sys
+from dataclasses import dataclass
+from pathlib import Path
+from urllib.error import HTTPError, URLError
+from urllib.parse import quote, unquote, urlparse
+from urllib.request import Request, urlopen
+
+
+OWNER = "creeper2eletricboogaloo"
+REPO = "L4JDownloadableContent"
+RAW_HOST = "raw.githubusercontent.com"
+MODRINTH_CDN_HOST = "cdn.modrinth.com"
+MODRINTH_API = "https://api.modrinth.com/v2"
+USER_AGENT = "L4JDownloadableContent-link-updater/1.0"
+
+
+@dataclass(frozen=True)
+class UrlRef:
+    file_path: Path
+    rel_file: str
+    path: str
+    prop: str
+    value: str
+    category: str | None
+    pack_id: str | None
+    pack_path: str | None
+    variant_id: str | None
+    variant_min_version: str | None
+
+
+@dataclass(frozen=True)
+class Change:
+    kind: str
+    rel_file: str
+    path: str
+    old: str
+    new: str
+
+
+@dataclass(frozen=True)
+class VariantAddition:
+    rel_file: str
+    path: str
+    base_url: str
+    variant_id: str
+    min_version: str
+    url: str
+    order: int
+
+
+@dataclass(frozen=True)
+class VariantTrack:
+    id: str
+    min_version: str
+    order: int
+
+
+@dataclass(frozen=True)
+class ConfigTrackAddition:
+    variant_id: str
+    min_version: str
+    project_count: int
+
+
+def repo_root() -> Path:
+    return Path(__file__).resolve().parents[1]
+
+
+def load_config(root: Path) -> dict:
+    path = root / "scripts" / "update_links_config.json"
+    return json.loads(path.read_text(encoding="utf-8"))
+
+
+def index_files(root: Path) -> list[Path]:
+    return sorted(p for p in root.rglob("index.json") if ".git" not in p.parts)
+
+
+def file_category(root: Path, file_path: Path) -> str:
+    rel = file_path.relative_to(root).as_posix()
+    return rel.split("/", 1)[0]
+
+
+def is_url(value: str) -> bool:
+    return value.startswith("http://") or value.startswith("https://")
+
+
+def is_variant_object(value: dict) -> bool:
+    return isinstance(value.get("id"), str) and isinstance(value.get("minVersion"), str) and isinstance(value.get("downloadURI"), str)
+
+
+def is_pack_object(value: dict) -> bool:
+    if not isinstance(value.get("id"), str) or is_variant_object(value):
+        return False
+    keys = {"downloadURI", "imageUrl", "downloadVariants", "bundlePacks", "worldTemplateDownloadURI", "worldTemplateVariants"}
+    return any(key in value for key in keys)
+
+
+def collect_urls(root: Path, file_path: Path, data: object) -> list[UrlRef]:
+    refs: list[UrlRef] = []
+    rel_file = file_path.relative_to(root).as_posix()
+    base_category = file_category(root, file_path)
+
+    def walk(value: object, path: str, prop: str, pack: tuple[str | None, str | None, str | None] | None, variant: tuple[str | None, str | None] | None) -> None:
+        if isinstance(value, str):
+            if is_url(value):
+                category, pack_id, pack_path = pack if pack else (None, None, None)
+                variant_id, variant_min_version = variant if variant else (None, None)
+                refs.append(UrlRef(file_path, rel_file, path, prop, value, category, pack_id, pack_path, variant_id, variant_min_version))
+            return
+        if isinstance(value, list):
+            for index, item in enumerate(value):
+                walk(item, f"{path}[{index}]", prop, pack, variant)
+            return
+        if isinstance(value, dict):
+            next_pack = pack
+            next_variant = variant
+            if is_variant_object(value):
+                next_variant = (value.get("id"), value.get("minVersion"))
+            elif is_pack_object(value):
+                next_pack = (value.get("categoryId") or base_category, value.get("id"), path)
+                next_variant = None
+            for key, item in value.items():
+                next_path = f"{path}.{key}" if path else key
+                walk(item, next_path, key, next_pack, next_variant)
+
+    walk(data, "", "", None, None)
+    return refs
+
+
+def parse_same_repo_raw(url: str) -> list[str] | None:
+    parsed = urlparse(url)
+    if parsed.netloc != RAW_HOST:
+        return None
+    parts = [unquote(part) for part in parsed.path.split("/") if part]
+    if len(parts) < 4 or parts[0] != OWNER or parts[1] != REPO:
+        return None
+    if parts[2] == "main":
+        return parts[3:]
+    if len(parts) >= 6 and parts[2:5] == ["refs", "heads", "main"]:
+        return parts[5:]
+    return None
+
+
+def raw_url_for(rel_parts: list[str], checksum: str) -> str:
+    rel = "/".join(rel_parts)
+    encoded = quote(rel, safe="/._-()")
+    return f"https://{RAW_HOST}/{OWNER}/{REPO}/main/{encoded}?checksum={checksum}"
+
+
+def md5_file(path: Path) -> str:
+    digest = hashlib.md5()
+    with path.open("rb") as handle:
+        for chunk in iter(lambda: handle.read(1024 * 1024), b""):
+            digest.update(chunk)
+    return digest.hexdigest()
+
+
+def parse_modrinth_download(url: str) -> dict | None:
+    parsed = urlparse(url)
+    if parsed.netloc != MODRINTH_CDN_HOST:
+        return None
+    parts = [unquote(part) for part in parsed.path.split("/") if part]
+    if len(parts) < 5 or parts[0] != "data" or parts[2] != "versions":
+        return None
+    return {
+        "project": parts[1],
+        "version": parts[3],
+        "filename": "/".join(parts[4:]),
+    }
+
+
+def pack_key(ref: UrlRef) -> str | None:
+    if not ref.category or not ref.pack_id:
+        return None
+    return f"{ref.category}:{ref.pack_id}"
+
+
+def configured_variant_tracks(config: dict) -> list[VariantTrack]:
+    variants = config.get("modrinth", {}).get("variants", [])
+    if isinstance(variants, dict):
+        items = [{"id": variant_id, "minVersion": item.get("minVersion")} for variant_id, item in variants.items() if isinstance(item, dict)]
+    elif isinstance(variants, list):
+        items = variants
+    else:
+        items = []
+    tracks: list[VariantTrack] = []
+    seen: set[str] = set()
+    for index, item in enumerate(items):
+        if not isinstance(item, dict):
+            continue
+        variant_id = item.get("id")
+        min_version = item.get("minVersion")
+        if not isinstance(variant_id, str) or not isinstance(min_version, str) or not variant_id or not min_version:
+            continue
+        if variant_id in seen:
+            continue
+        seen.add(variant_id)
+        tracks.append(VariantTrack(variant_id, min_version, index))
+    return tracks
+
+
+def version_sort_key(value: str) -> tuple:
+    parts = re.split(r"[.\-+_]", value)
+    key = []
+    for part in parts:
+        if part.isdigit():
+            key.append((0, int(part)))
+        else:
+            key.append((1, part))
+    return tuple(key)
+
+
+def variant_id_for_game_version(value: str) -> str:
+    return re.sub(r"[^0-9A-Za-z]+", "_", value).strip("_").lower()
+
+
+def discovery_settings(config: dict) -> tuple[bool, re.Pattern[str], int]:
+    settings = config.get("modrinth", {}).get("autoDiscoverVariants", {})
+    if not isinstance(settings, dict):
+        settings = {}
+    enabled = settings.get("enabled") is True
+    pattern = str(settings.get("gameVersionPattern", r"^26\.[0-9]+(\.[0-9]+)?$"))
+    minimum_projects = settings.get("minimumProjects", 3)
+    if not isinstance(minimum_projects, int) or minimum_projects < 1:
+        minimum_projects = 3
+    return enabled, re.compile(pattern), minimum_projects
+
+
+def load_json_files(root: Path) -> tuple[dict[Path, str], dict[Path, object], list[UrlRef]]:
+    texts: dict[Path, str] = {}
+    data_by_file: dict[Path, object] = {}
+    refs: list[UrlRef] = []
+    for file_path in index_files(root):
+        text = file_path.read_text(encoding="utf-8")
+        data = json.loads(text)
+        texts[file_path] = text
+        data_by_file[file_path] = data
+        refs.extend(collect_urls(root, file_path, data))
+    return texts, data_by_file, refs
+
+
+def fetch_modrinth_versions(project: str, cache: dict[str, list[dict]], warnings: list[str]) -> list[dict]:
+    if project in cache:
+        return cache[project]
+    request = Request(f"{MODRINTH_API}/project/{project}/version", headers={"User-Agent": USER_AGENT, "Accept": "application/json"})
+    try:
+        with urlopen(request, timeout=30) as response:
+            versions = json.loads(response.read().decode("utf-8"))
+    except (HTTPError, URLError, TimeoutError) as error:
+        warnings.append(f"Modrinth lookup failed for {project}: {error}")
+        versions = []
+    versions.sort(key=lambda item: item.get("date_published", ""), reverse=True)
+    cache[project] = versions
+    return versions
+
+
+def selected_file(version: dict, required_filename: str | None) -> dict | None:
+    files = version.get("files") or []
+    zip_files = [item for item in files if item.get("primary") is True and str(item.get("filename", "")).lower().endswith(".zip")]
+    if required_filename is not None:
+        zip_files = [item for item in zip_files if item.get("filename") == required_filename]
+    return zip_files[0] if zip_files else None
+
+
+def version_matches(version: dict, config: dict, required_game_version: str | None, require_base: bool, required_filename: str | None) -> bool:
+    modrinth = config.get("modrinth", {})
+    if version.get("version_type") not in set(modrinth.get("versionTypes", ["release"])):
+        return False
+    if modrinth.get("loader", "minecraft") not in set(version.get("loaders") or []):
+        return False
+    game_versions = version.get("game_versions") or []
+    if required_game_version is not None and required_game_version not in game_versions:
+        return False
+    if require_base and any(re.match(r"^26\.", item) for item in game_versions):
+        return False
+    return selected_file(version, required_filename) is not None
+
+
+def choose_modrinth_url(project: str, config: dict, cache: dict[str, list[dict]], warnings: list[str], required_game_version: str | None, require_base: bool, required_filename: str | None) -> str | None:
+    for version in fetch_modrinth_versions(project, cache, warnings):
+        if version_matches(version, config, required_game_version, require_base, required_filename):
+            file_item = selected_file(version, required_filename)
+            if file_item and file_item.get("url"):
+                return file_item["url"]
+    return None
+
+
+def project_filename_rules(refs: list[UrlRef]) -> dict[str, bool]:
+    projects: dict[str, set[str]] = {}
+    filenames: dict[str, set[str]] = {}
+    for ref in refs:
+        if ref.prop != "downloadURI":
+            continue
+        info = parse_modrinth_download(ref.value)
+        key = pack_key(ref)
+        if not info or not key:
+            continue
+        projects.setdefault(info["project"], set()).add(key)
+        filenames.setdefault(info["project"], set()).add(info["filename"])
+    return {project: len(projects.get(project, set())) > 1 and len(filenames.get(project, set())) > 1 for project in set(projects) | set(filenames)}
+
+
+def discover_variant_tracks(refs: list[UrlRef], config: dict, cache: dict[str, list[dict]], warnings: list[str], exact_filename: dict[str, bool], configured_tracks: list[VariantTrack]) -> tuple[list[VariantTrack], list[ConfigTrackAddition]]:
+    enabled, pattern, minimum_projects = discovery_settings(config)
+    if not enabled:
+        return configured_tracks, []
+    configured_versions = {track.min_version for track in configured_tracks}
+    configured_ids = {track.id for track in configured_tracks}
+    newest_configured = max((track.min_version for track in configured_tracks), key=version_sort_key, default="")
+    candidates: dict[str, set[str]] = {}
+    for ref in refs:
+        if ref.prop != "downloadURI" or ref.variant_id:
+            continue
+        info = parse_modrinth_download(ref.value)
+        if info is None:
+            continue
+        required_filename = info["filename"] if exact_filename.get(info["project"]) else None
+        for version in fetch_modrinth_versions(info["project"], cache, warnings):
+            if not version_matches(version, config, None, False, required_filename):
+                continue
+            for game_version in version.get("game_versions") or []:
+                if not isinstance(game_version, str) or not pattern.match(game_version):
+                    continue
+                if newest_configured and version_sort_key(game_version) <= version_sort_key(newest_configured):
+                    continue
+                if game_version in configured_versions:
+                    continue
+                candidates.setdefault(game_version, set()).add(info["project"])
+    additions: list[ConfigTrackAddition] = []
+    tracks = list(configured_tracks)
+    order = max((track.order for track in tracks), default=-1) + 1
+    for min_version in sorted(candidates, key=version_sort_key):
+        project_count = len(candidates[min_version])
+        if project_count < minimum_projects:
+            continue
+        variant_id = variant_id_for_game_version(min_version)
+        if variant_id in configured_ids:
+            warnings.append(f"Discovered variant {min_version} maps to configured id {variant_id}")
+            continue
+        additions.append(ConfigTrackAddition(variant_id, min_version, project_count))
+        tracks.append(VariantTrack(variant_id, min_version, order))
+        configured_ids.add(variant_id)
+        configured_versions.add(min_version)
+        order += 1
+    return tracks, additions
+
+
+def build_changes(root: Path, refs: list[UrlRef], config: dict) -> tuple[list[Change], list[VariantAddition], list[ConfigTrackAddition], list[str]]:
+    changes: list[Change] = []
+    additions: list[VariantAddition] = []
+    warnings: list[str] = []
+    cache: dict[str, list[dict]] = {}
+    exact_filename = project_filename_rules(refs)
+    variant_tracks, config_additions = discover_variant_tracks(refs, config, cache, warnings, exact_filename, configured_variant_tracks(config))
+    variant_by_id = {track.id: track for track in variant_tracks}
+    existing_variants = {(ref.rel_file, ref.pack_path, ref.variant_id) for ref in refs if ref.prop == "downloadURI" and ref.variant_id and ".downloadVariants[" in ref.path}
+    variant_urls: dict[tuple[str, str | None], set[str]] = {}
+    for ref in refs:
+        if ref.prop == "downloadURI" and ref.variant_id and ".downloadVariants[" in ref.path:
+            variant_urls.setdefault((ref.rel_file, ref.pack_path), set()).add(ref.value)
+
+    for ref in refs:
+        rel_parts = parse_same_repo_raw(ref.value)
+        if rel_parts is not None:
+            local_path = root.joinpath(*rel_parts)
+            if not local_path.exists():
+                warnings.append(f"Missing local file for {ref.rel_file} {ref.path}: {'/'.join(rel_parts)}")
+                continue
+            new_url = raw_url_for(rel_parts, md5_file(local_path))
+            if new_url != ref.value:
+                changes.append(Change("local", ref.rel_file, ref.path, ref.value, new_url))
+            continue
+        if ref.prop != "downloadURI":
+            continue
+        info = parse_modrinth_download(ref.value)
+        if info is None:
+            continue
+        key = pack_key(ref)
+        if key is None:
+            warnings.append(f"Missing pack identity for {ref.rel_file} {ref.path}")
+            continue
+        required_filename = info["filename"] if exact_filename.get(info["project"]) else None
+        if ref.variant_id:
+            variant_track = variant_by_id.get(ref.variant_id)
+            if not variant_track:
+                warnings.append(f"Unconfigured variant {ref.variant_id} for {key} at {ref.rel_file} {ref.path}")
+                continue
+            new_url = choose_modrinth_url(info["project"], config, cache, warnings, variant_track.min_version, False, required_filename)
+            if new_url is None:
+                warnings.append(f"No Modrinth match for {key} variant {ref.variant_id} at {ref.rel_file} {ref.path}")
+                continue
+            if new_url != ref.value:
+                changes.append(Change("modrinth", ref.rel_file, ref.path, ref.value, new_url))
+            continue
+        new_url = choose_modrinth_url(info["project"], config, cache, warnings, None, True, required_filename)
+        if new_url is None:
+            warnings.append(f"No Modrinth base match for {key} at {ref.rel_file} {ref.path}")
+        elif new_url in variant_urls.get((ref.rel_file, ref.pack_path), set()):
+            warnings.append(f"Base Modrinth match duplicates an existing variant for {key} at {ref.rel_file} {ref.path}")
+        elif new_url != ref.value:
+            changes.append(Change("modrinth", ref.rel_file, ref.path, ref.value, new_url))
+        anchor_url = new_url if new_url is not None and new_url != ref.value and new_url not in variant_urls.get((ref.rel_file, ref.pack_path), set()) else ref.value
+        for track in variant_tracks:
+            if (ref.rel_file, ref.pack_path, track.id) in existing_variants:
+                continue
+            candidate = choose_modrinth_url(info["project"], config, cache, warnings, track.min_version, False, required_filename)
+            if candidate is not None:
+                additions.append(VariantAddition(ref.rel_file, ref.pack_path or ref.path, anchor_url, track.id, track.min_version, candidate, track.order))
+    return changes, sorted(set(additions), key=lambda item: (item.rel_file, item.path, item.order, item.variant_id)), config_additions, sorted(set(warnings))
+
+
+def replacement_token(value: str) -> str:
+    return json.dumps(value, ensure_ascii=False)
+
+
+def skip_string(text: str, index: int) -> int:
+    index += 1
+    while index < len(text):
+        char = text[index]
+        if char == "\\":
+            index += 2
+            continue
+        if char == '"':
+            return index + 1
+        index += 1
+    return index
+
+
+def matching_bracket(text: str, start: int) -> int | None:
+    if start >= len(text) or text[start] not in "{[":
+        return None
+    pairs = {"{": "}", "[": "]"}
+    stack = [text[start]]
+    index = start + 1
+    while index < len(text):
+        char = text[index]
+        if char == '"':
+            index = skip_string(text, index)
+            continue
+        if char in "{[":
+            stack.append(char)
+            index += 1
+            continue
+        if char in "}]":
+            if not stack or pairs[stack[-1]] != char:
+                return None
+            stack.pop()
+            if not stack:
+                return index
+        index += 1
+    return None
+
+
+def containing_object_bounds(text: str, position: int) -> tuple[int, int] | None:
+    stack: list[tuple[str, int]] = []
+    index = 0
+    while index < position:
+        char = text[index]
+        if char == '"':
+            end = skip_string(text, index)
+            if end > position:
+                break
+            index = end
+            continue
+        if char in "{[":
+            stack.append((char, index))
+        elif char in "}]" and stack:
+            stack.pop()
+        index += 1
+    for char, start in reversed(stack):
+        if char == "{":
+            end = matching_bracket(text, start)
+            if end is not None:
+                return start, end
+    return None
+
+
+def find_property_value_span(text: str, start: int, end: int, name: str) -> tuple[int, int, int] | None:
+    token = replacement_token(name)
+    depth = 0
+    index = start + 1
+    while index < end:
+        char = text[index]
+        if char == '"':
+            if depth == 0 and text.startswith(token, index):
+                key_end = index + len(token)
+                colon = key_end
+                while colon < end and text[colon].isspace():
+                    colon += 1
+                if colon < end and text[colon] == ":":
+                    value_start = colon + 1
+                    while value_start < end and text[value_start].isspace():
+                        value_start += 1
+                    if value_start >= end:
+                        return None
+                    value_char = text[value_start]
+                    if value_char in "[{":
+                        value_end = matching_bracket(text, value_start)
+                        if value_end is None:
+                            return None
+                        return value_start, value_end + 1, index
+                    if value_char == '"':
+                        return value_start, skip_string(text, value_start), index
+                    value_end = value_start
+                    while value_end < end and text[value_end] not in ",}":
+                        value_end += 1
+                    while value_end > value_start and text[value_end - 1].isspace():
+                        value_end -= 1
+                    return value_start, value_end, index
+            index = skip_string(text, index)
+            continue
+        if char in "[{":
+            depth += 1
+        elif char in "]}":
+            depth -= 1
+        index += 1
+    return None
+
+
+def path_tokens(path: str) -> list[str | int]:
+    tokens: list[str | int] = []
+    index = 0
+    while index < len(path):
+        if path[index] == ".":
+            index += 1
+            continue
+        if path[index] == "[":
+            end = path.find("]", index)
+            if end == -1:
+                return []
+            value = path[index + 1:end]
+            if not value.isdigit():
+                return []
+            tokens.append(int(value))
+            index = end + 1
+            continue
+        end = index
+        while end < len(path) and path[end] not in ".[":
+            end += 1
+        tokens.append(path[index:end])
+        index = end
+    return tokens
+
+
+def find_array_item_span(text: str, start: int, end: int, item_index: int) -> tuple[int, int] | None:
+    if start >= len(text) or text[start] != "[":
+        return None
+    index = start + 1
+    current = 0
+    while index < end:
+        while index < end and text[index].isspace():
+            index += 1
+        if index < end and text[index] == ",":
+            index += 1
+            continue
+        if index >= end or text[index] == "]":
+            return None
+        value_start = index
+        if text[index] in "[{":
+            close = matching_bracket(text, index)
+            if close is None:
+                return None
+            value_end = close + 1
+        elif text[index] == '"':
+            value_end = skip_string(text, index)
+        else:
+            value_end = index
+            while value_end < end and text[value_end] not in ",]":
+                value_end += 1
+            while value_end > value_start and text[value_end - 1].isspace():
+                value_end -= 1
+        if current == item_index:
+            return value_start, value_end
+        current += 1
+        index = value_end
+    return None
+
+
+def find_value_span_by_path(text: str, path: str) -> tuple[int, int] | None:
+    start = 0
+    while start < len(text) and text[start].isspace():
+        start += 1
+    end = matching_bracket(text, start)
+    if end is None:
+        return None
+    current_start = start
+    current_end = end + 1
+    for token in path_tokens(path):
+        if isinstance(token, str):
+            if current_start >= len(text) or text[current_start] != "{":
+                return None
+            span = find_property_value_span(text, current_start, current_end - 1, token)
+            if span is None:
+                return None
+            current_start, current_end = span[0], span[1]
+        else:
+            if current_start >= len(text) or text[current_start] != "[":
+                return None
+            span = find_array_item_span(text, current_start, current_end - 1, token)
+            if span is None:
+                return None
+            current_start, current_end = span
+    return current_start, current_end
+
+
+def find_pack_object_bounds(text: str, addition: VariantAddition) -> tuple[int, int] | None:
+    span = find_value_span_by_path(text, addition.path)
+    if span is None:
+        return None
+    if span[0] < len(text) and text[span[0]] == "{":
+        return span[0], span[1] - 1
+    return containing_object_bounds(text, span[0])
+
+
+def line_indent(text: str, index: int) -> str:
+    line_start = text.rfind("\n", 0, index) + 1
+    match = re.match(r"\s*", text[line_start:index])
+    return match.group(0) if match else ""
+
+
+def merge_variants(existing: object, additions: list[VariantAddition]) -> list[dict]:
+    variants = list(existing) if isinstance(existing, list) else []
+    seen = {item.get("id") for item in variants if isinstance(item, dict)}
+    for addition in sorted(additions, key=lambda item: (item.order, item.variant_id)):
+        if addition.variant_id in seen:
+            continue
+        variants.append({
+            "id": addition.variant_id,
+            "minVersion": addition.min_version,
+            "downloadURI": addition.url,
+        })
+        seen.add(addition.variant_id)
+    return variants
+
+
+def variants_array_value(variants: list[dict], indent: str) -> str:
+    child = indent + "  "
+    item_indent = child + "  "
+    blocks = []
+    for variant in variants:
+        blocks.append(
+            f"{child}{{\n"
+            f'{item_indent}"id": {replacement_token(variant.get("id", ""))},\n'
+            f'{item_indent}"minVersion": {replacement_token(variant.get("minVersion", ""))},\n'
+            f'{item_indent}"downloadURI": {replacement_token(variant.get("downloadURI", ""))}\n'
+            f"{child}}}"
+        )
+    return "[\n" + ",\n".join(blocks) + f"\n{indent}]"
+
+
+def variants_property_block(variants: list[dict], indent: str, gap: str, trailing_comma: bool) -> str:
+    suffix = "," if trailing_comma else ""
+    return f'{indent}"downloadVariants"{gap}{variants_array_value(variants, indent)}{suffix}\n'
+
+
+def apply_variant_additions(text: str, additions: list[VariantAddition]) -> tuple[str, str | None]:
+    bounds = find_pack_object_bounds(text, additions[0])
+    if bounds is None:
+        return text, f"Could not find pack object in {additions[0].rel_file}: {additions[0].path}"
+    try:
+        pack = json.loads(text[bounds[0]:bounds[1] + 1])
+    except json.JSONDecodeError:
+        return text, f"Could not parse pack object in {additions[0].rel_file}: {additions[0].path}"
+    if not isinstance(pack, dict) or pack.get("downloadURI") != additions[0].base_url:
+        return text, f"Pack URL mismatch in {additions[0].rel_file}: {additions[0].path}"
+    existing = pack.get("downloadVariants") if isinstance(pack, dict) else []
+    variants = merge_variants(existing, additions)
+    span = find_property_value_span(text, bounds[0], bounds[1], "downloadVariants")
+    if span is not None:
+        value_start, value_end, key_start = span
+        indent = line_indent(text, key_start)
+        return text[:value_start] + variants_array_value(variants, indent) + text[value_end:], None
+    download_span = find_property_value_span(text, bounds[0], bounds[1], "downloadURI")
+    if download_span is None:
+        return text, f"Could not find downloadURI in {additions[0].rel_file}: {additions[0].path}"
+    line_start = text.rfind("\n", 0, download_span[2]) + 1
+    line_end = text.find("\n", download_span[2])
+    if line_end == -1:
+        line_end = len(text)
+    line = text[line_start:line_end]
+    match = re.match(r'(\s*)"downloadURI"(\s*:\s*)', line)
+    if not match:
+        return text, f"Could not determine indentation in {additions[0].rel_file}: {additions[0].path}"
+    next_text = text[line_end + 1:bounds[1]].lstrip()
+    block = variants_property_block(variants, match.group(1), match.group(2), bool(next_text and not next_text.startswith("}")))
+    comma = "" if line.rstrip().endswith(",") else ","
+    return text[:line_end] + comma + text[line_end:line_end + 1] + block + text[line_end + 1:], None
+
+
+def write_config_tracks(root: Path, config: dict, additions: list[ConfigTrackAddition]) -> None:
+    modrinth = config.setdefault("modrinth", {})
+    variants = modrinth.get("variants", [])
+    if isinstance(variants, dict):
+        variants = [{"id": variant_id, "minVersion": item.get("minVersion")} for variant_id, item in variants.items() if isinstance(item, dict)]
+    elif not isinstance(variants, list):
+        variants = []
+    existing_ids = {item.get("id") for item in variants if isinstance(item, dict)}
+    existing_versions = {item.get("minVersion") for item in variants if isinstance(item, dict)}
+    for addition in additions:
+        if addition.variant_id in existing_ids or addition.min_version in existing_versions:
+            continue
+        variants.append({
+            "id": addition.variant_id,
+            "minVersion": addition.min_version,
+        })
+        existing_ids.add(addition.variant_id)
+        existing_versions.add(addition.min_version)
+    modrinth["variants"] = variants
+    path = root / "scripts" / "update_links_config.json"
+    path.write_text(json.dumps(config, indent=2) + "\n", encoding="utf-8")
+
+
+def write_changes(root: Path, texts: dict[Path, str], changes: list[Change], additions: list[VariantAddition]) -> list[str]:
+    errors: list[str] = []
+    by_file: dict[str, dict[str, str]] = {}
+    additions_by_file: dict[str, dict[str, list[VariantAddition]]] = {}
+    file_paths: dict[str, Path] = {}
+    for change in changes:
+        mapping = by_file.setdefault(change.rel_file, {})
+        if change.old in mapping and mapping[change.old] != change.new:
+            errors.append(f"Conflicting replacement for {change.rel_file}: {change.old}")
+            continue
+        mapping[change.old] = change.new
+    for addition in additions:
+        additions_by_file.setdefault(addition.rel_file, {}).setdefault(addition.path, []).append(addition)
+    for path in texts:
+        file_paths[path.relative_to(root).as_posix()] = path
+    next_texts: dict[Path, str] = {}
+    affected = set(by_file) | set(additions_by_file)
+    for rel_file in sorted(affected):
+        path = file_paths[rel_file]
+        text = texts[path]
+        for old, new in by_file.get(rel_file, {}).items():
+            old_token = replacement_token(old)
+            new_token = replacement_token(new)
+            if old_token not in text:
+                errors.append(f"Could not find URL token in {rel_file}: {old}")
+                continue
+            text = text.replace(old_token, new_token)
+        for grouped_additions in additions_by_file.get(rel_file, {}).values():
+            text, error = apply_variant_additions(text, grouped_additions)
+            if error:
+                errors.append(error)
+        next_texts[path] = text
+    if errors:
+        return errors
+    for path, text in next_texts.items():
+        path.write_text(text, encoding="utf-8")
+    return errors
+
+
+def print_report(changes: list[Change], additions: list[VariantAddition], config_additions: list[ConfigTrackAddition], warnings: list[str], wrote: bool) -> None:
+    action = "Updated" if wrote else "Would update"
+    total = len(changes) + len(additions) + len(config_additions)
+    if total:
+        counts: dict[str, int] = {}
+        for change in changes:
+            counts[change.kind] = counts.get(change.kind, 0) + 1
+        if additions:
+            counts["variant"] = len(additions)
+        if config_additions:
+            counts["config"] = len(config_additions)
+        print(f"{action} {total} values")
+        for kind in sorted(counts):
+            print(f"{kind}: {counts[kind]}")
+        for change in changes[:50]:
+            print(f"{change.kind} {change.rel_file} {change.path}")
+        shown = min(len(changes), 50)
+        for config_addition in config_additions[: max(0, 50 - shown)]:
+            print(f"config variant {config_addition.variant_id} minVersion {config_addition.min_version} projects {config_addition.project_count}")
+        shown += min(len(config_additions), max(0, 50 - shown))
+        for addition in additions[: max(0, 50 - shown)]:
+            print(f"variant {addition.rel_file} {addition.path}")
+        if total > 50:
+            print(f"... {total - 50} more")
+    else:
+        print("No URL updates needed")
+    if warnings:
+        print(f"Warnings: {len(warnings)}")
+        for warning in warnings[:80]:
+            print(warning)
+        if len(warnings) > 80:
+            print(f"... {len(warnings) - 80} more")
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser()
+    mode = parser.add_mutually_exclusive_group(required=True)
+    mode.add_argument("--check", action="store_true")
+    mode.add_argument("--write", action="store_true")
+    args = parser.parse_args()
+    root = repo_root()
+    config = load_config(root)
+    texts, _, refs = load_json_files(root)
+    changes, additions, config_additions, warnings = build_changes(root, refs, config)
+    if args.write and (changes or additions or config_additions):
+        errors = write_changes(root, texts, changes, additions)
+        if errors:
+            for error in errors:
+                print(error, file=sys.stderr)
+            return 2
+        if config_additions:
+            write_config_tracks(root, config, config_additions)
+    print_report(changes, additions, config_additions, warnings, args.write and bool(changes or additions or config_additions))
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())
diff --git a/scripts/update_links_config.json b/scripts/update_links_config.json
new file mode 100644
index 0000000..f77e2d0
--- /dev/null
+++ b/scripts/update_links_config.json
@@ -0,0 +1,19 @@
+{
+  "modrinth": {
+    "loader": "minecraft",
+    "versionTypes": [
+      "release"
+    ],
+    "variants": [
+      {
+        "id": "26_1_2",
+        "minVersion": "26.1.2"
+      }
+    ],
+    "autoDiscoverVariants": {
+      "enabled": true,
+      "gameVersionPattern": "^26\\.[0-9]+(\\.[0-9]+)?$",
+      "minimumProjects": 3
+    }
+  }
+}