diff --git a/.agents/skills/commit/SKILL.md b/.agents/skills/commit/SKILL.md
new file mode 100644
index 000000000..2e9da3ee1
--- /dev/null
+++ b/.agents/skills/commit/SKILL.md
@@ -0,0 +1,55 @@
+---
+name: commit
+description: Use this skill when asked to create or amend a commit.
+---
+
+# Commit
+
+Use this skill whenever creating or amending a commit.
+
+## 1) Fetch and follow official commit guidelines
+
+Run:
+
+```bash
+scripts/fetch-commit-guidelines.sh
+```
+
+Use that output as the source of truth for commit format/rules.
+
+**Exception:** Do not **manually wrap lines** or **enforce maximum line length**, ignore any instructions to the contrary.
+
+## 2) Write the commit body for maintainers
+
+Commit messages are reused as PR descriptions. Therefore, write commit messages keeping in mind that the primary audiences are human code reviewers and future maintainers. Optimize for skimmability while retaining sufficient context around changes, but do not repeat context that is easily inferred from the changes themselves, linked issues, or background information that mainters with at least a basic familiarity of the codebase would possess. 
+
+Some tips:
+- include brief context for why the change is needed
+- include why this approach was chosen (when relevant)
+- include links to relevant sources/issues/docs when useful
+- be concise, human, and specific
+- assume reviewers will skim the linked issue; do not restate it in depth
+
+Commit messages use Markdown formatting. For example, use backticks for technical literals, inline links for URLs, and lists where useful.
+
+When committing, you should use heredoc format to preserve newlines and other formatting.
+
+## 3) Append Commit Footer
+
+If a commit is related to a GitHub issue, this must be noted in a footer.
+
+These footers must be placed on their own lines. The footer looks like the following:
+
+```
+[keyword] #[issue-id]
+```
+
+When the issue is in a different repo, use `[keyword] [repo]#[issue-id]` or, if the repo belongs to a different owner, `[keyword] [owner]/[repo]#[issue-id]`.
+
+The keywords "Closes", "Fixes" and "Resolves" indicate that the commit fully addresses the issue. Merging a pull request containing such a commit will close the referenced issue.
+
+The keywords "References", "Related to", and "Contributes to" may be used to indicate a relation to the issue, when the issue is not fully addressed by the commit. The issue will not be auto-closed upon merge.
+
+One commit may contain zero or more footers; make sure all related issues you are aware of have a corresponding footer.
+
+A pre-commit hook will take care of linking Linear issues, where applicable. Do not manually add these links, or use any format other than what is described here. You need to follow this precise format so that the pre-commit hook can work properly.
diff --git a/.agents/skills/commit/scripts/fetch-commit-guidelines.sh b/.agents/skills/commit/scripts/fetch-commit-guidelines.sh
new file mode 100755
index 000000000..ccc2026f8
--- /dev/null
+++ b/.agents/skills/commit/scripts/fetch-commit-guidelines.sh
@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+URL="https://develop.sentry.dev/engineering-practices/commit-messages.md"
+curl -fsSL "$URL"
diff --git a/.gitignore b/.gitignore
index 78c683245..56d1d0d49 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,4 @@ target
 venv
 .claude/settings.local.json
 .DS_Store
+__pycache__
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
new file mode 100644
index 000000000..310024ec7
--- /dev/null
+++ b/.pre-commit-config.yaml
@@ -0,0 +1,10 @@
+default_install_hook_types: [commit-msg]
+
+repos:
+  - repo: local
+    hooks:
+      - id: expand-github-linear-footer
+        name: Expand GitHub/Linear commit footer
+        entry: scripts/commit-msg-expand-issues.py
+        language: script
+        stages: [commit-msg]
diff --git a/scripts/commit-msg-expand-issues.py b/scripts/commit-msg-expand-issues.py
new file mode 100755
index 000000000..7d1c50a77
--- /dev/null
+++ b/scripts/commit-msg-expand-issues.py
@@ -0,0 +1,257 @@
+#!/usr/bin/env python3
+"""Expand GitHub issue commit footers and add Linear footers when available."""
+
+from __future__ import annotations
+
+import json
+import re
+import subprocess
+import sys
+from dataclasses import dataclass
+from pathlib import Path
+from typing import Any
+
+FOOTER_RE = re.compile(
+    r"^(?P<prefix>\s*)(?P<keyword>\w+(?:\s+to)?)\s+"
+    r"(?P<display>(?:(?P<owner>[A-Za-z0-9_.-]+)/)?(?:(?P<repo>[A-Za-z0-9_.-]+))?#(?P<issue>[1-9]\d*))"
+    r"(?P<suffix>\.?\s*)$"
+)
+LINEAR_LINKBACK_AUTHORS = {"linear", "linear-code"}
+LINEAR_LINKBACK_MARKERS = ("linear-linkback", "linear linkback")
+
+LINEAR_URL_RE = re.compile(
+    r"(?P<url>https://linear\.app/[^\s<>)\]\"']*/issue/(?P<id>[^/\s<>)\]\"']+)[^\s<>)\]\"']*)"
+)
+
+
+@dataclass(frozen=True)
+class Match:
+    line_index: int
+    prefix: str
+    keyword: str
+    display: str
+    owner: str | None
+    repo: str | None
+    issue: str
+    suffix: str
+
+
+@dataclass(frozen=True)
+class IssueInfo:
+    url: str
+    linear_id: str | None = None
+    linear_url: str | None = None
+
+
+def warn(message: str) -> None:
+    print(f"commit-msg-expand-issues: warning: {message}", file=sys.stderr)
+
+
+def run_gh(args: list[str]) -> tuple[dict[str, Any] | None, str | None]:
+    try:
+        result = subprocess.run(
+            ["gh", *args],
+            check=False,
+            capture_output=True,
+            encoding="utf-8",
+        )
+    except FileNotFoundError:
+        return None, "gh was not found"
+    except OSError as exc:
+        return None, f"failed to run gh: {exc}"
+
+    if result.returncode != 0:
+        detail = (result.stderr or result.stdout).strip()
+        return None, detail or f"gh exited with status {result.returncode}"
+
+    try:
+        return json.loads(result.stdout), None
+    except json.JSONDecodeError as exc:
+        return None, f"failed to parse gh output: {exc}"
+
+
+def run_gh_text(args: list[str]) -> tuple[str | None, str | None]:
+    try:
+        result = subprocess.run(
+            ["gh", *args],
+            check=False,
+            capture_output=True,
+            encoding="utf-8",
+        )
+    except FileNotFoundError:
+        return None, "gh was not found"
+    except OSError as exc:
+        return None, f"failed to run gh: {exc}"
+
+    if result.returncode != 0:
+        detail = (result.stderr or result.stdout).strip()
+        return None, detail or f"gh exited with status {result.returncode}"
+    return result.stdout.strip(), None
+
+
+def current_repo() -> tuple[str, str] | None:
+    name_with_owner, error = run_gh_text(
+        ["repo", "view", "--json", "nameWithOwner", "-q", ".nameWithOwner"]
+    )
+    if error is not None:
+        warn(f"could not resolve current repository: {error}")
+        return None
+
+    if not name_with_owner or "/" not in name_with_owner:
+        warn("could not resolve current repository: unexpected gh output")
+        return None
+
+    owner, repo = name_with_owner.split("/", 1)
+    return owner, repo
+
+
+def is_linear_linkback_comment(comment: dict[str, Any]) -> bool:
+    author = comment.get("author")
+    if (
+        not isinstance(author, dict)
+        or author.get("login") not in LINEAR_LINKBACK_AUTHORS
+    ):
+        return False
+
+    body = comment.get("body")
+    if not isinstance(body, str):
+        return False
+
+    normalized_body = body.lower()
+    return any(marker in normalized_body for marker in LINEAR_LINKBACK_MARKERS)
+
+
+def find_linear_link(issue: dict[str, Any]) -> tuple[str, str] | None:
+    comments = issue.get("comments") or []
+    if not isinstance(comments, list):
+        return None
+
+    for comment in comments:
+        if not isinstance(comment, dict) or not is_linear_linkback_comment(comment):
+            continue
+
+        body = comment["body"]
+        url_match = LINEAR_URL_RE.search(body)
+        if not url_match:
+            continue
+
+        return url_match.group("id"), url_match.group("url")
+    return None
+
+
+def fetch_issue(owner_repo: str, issue_number: str) -> IssueInfo | None:
+    result, error = run_gh(
+        [
+            "issue",
+            "view",
+            issue_number,
+            "-R",
+            owner_repo,
+            "--json",
+            "number,url,comments",
+        ]
+    )
+    if error is not None:
+        warn(f"could not fetch {owner_repo}#{issue_number}: {error}")
+        return None
+    if not isinstance(result, dict) or not isinstance(result.get("url"), str):
+        warn(f"could not fetch {owner_repo}#{issue_number}: unexpected gh output")
+        return None
+
+    linear = find_linear_link(result)
+    if linear is None:
+        return IssueInfo(url=result["url"])
+    linear_id, linear_url = linear
+    return IssueInfo(url=result["url"], linear_id=linear_id, linear_url=linear_url)
+
+
+def collect_matches(lines: list[str]) -> list[Match]:
+    matches: list[Match] = []
+    for index, line in enumerate(lines):
+        stripped_newline = line.removesuffix("\n")
+        match = FOOTER_RE.match(stripped_newline)
+        if match is None:
+            continue
+        matches.append(
+            Match(
+                line_index=index,
+                prefix=match.group("prefix"),
+                keyword=match.group("keyword"),
+                display=match.group("display"),
+                owner=match.group("owner"),
+                repo=match.group("repo"),
+                issue=match.group("issue"),
+                suffix=match.group("suffix"),
+            )
+        )
+    return matches
+
+
+def resolve_owner_repo(match: Match, current_owner: str, current_repo_name: str) -> str:
+    if match.owner is not None and match.repo is not None:
+        return f"{match.owner}/{match.repo}"
+    if match.repo is not None:
+        return f"{current_owner}/{match.repo}"
+    return f"{current_owner}/{current_repo_name}"
+
+
+def process_message(path: Path) -> None:
+    try:
+        lines = path.read_text(encoding="utf-8").splitlines(keepends=True)
+    except OSError as exc:
+        warn(f"could not read commit message: {exc}")
+        return
+
+    matches = collect_matches(lines)
+    if not matches:
+        return
+
+    repo = current_repo()
+    if repo is None:
+        return
+    current_owner, current_repo_name = repo
+
+    issue_cache: dict[tuple[str, str], IssueInfo | None] = {}
+    replacements: dict[int, str] = {}
+
+    for match in matches:
+        owner_repo = resolve_owner_repo(match, current_owner, current_repo_name)
+        key = (owner_repo, match.issue)
+        if key not in issue_cache:
+            issue_cache[key] = fetch_issue(owner_repo, match.issue)
+
+        issue = issue_cache[key]
+        if issue is None:
+            continue
+
+        replacement = f"{match.prefix}{match.keyword} [{match.display}]({issue.url}){match.suffix}\n"
+        if issue.linear_id is not None and issue.linear_url is not None:
+            next_line = (
+                lines[match.line_index + 1] if match.line_index + 1 < len(lines) else ""
+            )
+            linear_line = f"{match.prefix}{match.keyword} [{issue.linear_id}]({issue.linear_url})\n"
+            if next_line != linear_line:
+                replacement += linear_line
+        replacements[match.line_index] = replacement
+
+    if not replacements:
+        return
+
+    new_lines = [replacements.get(index, line) for index, line in enumerate(lines)]
+    try:
+        path.write_text("".join(new_lines), encoding="utf-8")
+    except OSError as exc:
+        warn(f"could not write commit message: {exc}")
+
+
+def main(argv: list[str]) -> int:
+    if len(argv) != 2:
+        warn("expected exactly one commit message file path")
+        return 0
+
+    process_message(Path(argv[1]))
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main(sys.argv))