diff --git a/akd_ext/artifacts/stores/github.py b/akd_ext/artifacts/stores/github.py
new file mode 100644
index 0000000..acbd4cb
--- /dev/null
+++ b/akd_ext/artifacts/stores/github.py
@@ -0,0 +1,209 @@
+import os
+import re
+from contextlib import nullcontext
+from datetime import datetime, timezone
+from pathlib import PurePosixPath
+from typing import Self
+
+from github import Auth, Github, UnknownObjectException
+from loguru import logger
+
+from akd_ext.artifacts._base import Artifact, ArtifactStore
+
+
+class GitHubArtifactStore(ArtifactStore[str]):
+    """GitHub-backed artifact store.
+
+    Reads and writes artifacts inside a sub-tree of a GitHub repo via
+    the GitHub REST API (PyGithub). `root` can be either
+    "owner/repo[/path/within/repo]" or a github.com URL; in both cases
+    the first two segments identify the repo and any remaining segments
+    scope the store to that sub-tree. Slugs returned by the store are
+    relative to the sub-tree, matching `LocalArtifactStore`'s form — so
+    an agent's tool calls don't depend on which backend is in use.
+    """
+
+    def __init__(
+        self,
+        root: str,
+        *,
+        branch: str = "main",
+        access_token: str | None = None,
+        github_client: Github | None = None,
+        index_file: str | None = "README.md",
+        supported_extensions: tuple[str, ...] = (".md",),
+        debug: bool = False,
+    ) -> None:
+        """Construct a GitHub-backed artifact store.
+
+        Args:
+            root: "owner/repo[/path]" or a github.com URL (e.g.
+                "https://github.com/NASA-IMPACT/akd/tree/main/agents/x/artifacts").
+            branch: Branch to read/write. Defaults to "main". A branch
+                embedded in a `.../tree/<branch>/...` URL takes precedence
+                over this kwarg.
+            access_token: GitHub personal access token. Falls back to
+                the `GITHUB_ACCESS_TOKEN` env var. Anonymous (public-read
+                only) if neither is set. Ignored if `github_client` is set.
+            github_client: Optional pre-built PyGithub client. When set,
+                the store uses it for all API calls and does NOT close
+                it on method exit (caller owns the lifetime). Useful for
+                bulk writes (reuses the HTTP session) and for tests
+                (inject a MagicMock). When None (default), a fresh
+                client is constructed per method call.
+            index_file: Directory-overview filename (defaults to README.md,
+                which GitHub renders at the directory level).
+            supported_extensions: Extensions to include; see ArtifactStore.
+            debug: Enable debug logging.
+
+        Raises:
+            ValueError: If `root` does not contain at least "owner/repo".
+        """
+        super().__init__(
+            root=root,
+            index_file=index_file,
+            supported_extensions=supported_extensions,
+            debug=debug,
+        )
+        self.repo_name, self.path_prefix, url_branch = self._parse_root(root)
+        self.branch = url_branch or branch
+        self._token = access_token or os.getenv("GITHUB_ACCESS_TOKEN")
+        self._auth = Auth.Token(self._token) if self._token else None
+        self._github_client = github_client
+
+    def _client(self):
+        """Context manager yielding a Github client.
+
+        If a `github_client` was injected via `__init__`, returns it
+        wrapped in `nullcontext` (no close on exit — caller owns it).
+        Otherwise constructs a fresh client that closes on context exit.
+        """
+        if self._github_client is not None:
+            return nullcontext(self._github_client)
+        return Github(auth=self._auth, retry=None)
+
+    @staticmethod
+    def _parse_root(root: str) -> tuple[str, str, str | None]:
+        """Parse `root` into (repo_name, path_prefix, branch_hint).
+
+        Accepts plain ``owner/repo[/path]`` or a github.com URL (with or
+        without scheme; with or without a ``/tree/<branch>/...`` segment).
+        `branch_hint` is the URL-extracted branch if present, else None.
+        """
+        s = re.sub(r"^(?:https?://)?(?:www\.)?github\.com/?", "", root.strip()).rstrip("/")
+        parts = PurePosixPath(s).parts
+        if len(parts) < 2:
+            raise ValueError(f"GitHub root must be 'owner/repo[/path]' or a github.com URL, got {root!r}")
+        repo_name = f"{parts[0]}/{parts[1]}"
+        if len(parts) >= 4 and parts[2] in ("tree", "blob"):
+            return repo_name, "/".join(parts[4:]), parts[3]
+        return repo_name, "/".join(parts[2:]), None
+
+    async def load_artifacts(self) -> Self:
+        """Load all available artifacts into the cache.
+
+        Returns:
+            Self, for fluent chaining.
+        """
+        prefix = PurePosixPath(self.path_prefix) if self.path_prefix else None
+        with self._client() as gh:
+            repo = gh.get_repo(self.repo_name)
+            tree = repo.get_git_tree(self.branch, recursive=True)
+            for entry in tree.tree:
+                if entry.type != "blob":
+                    continue
+                full = PurePosixPath(entry.path)
+                if prefix and not full.is_relative_to(prefix):
+                    continue
+                slug = str(full.relative_to(prefix)) if prefix else entry.path
+                if not self._is_supported(slug):
+                    continue
+                content_file = repo.get_contents(entry.path, ref=self.branch)
+                self[slug] = Artifact[str](
+                    path=slug,
+                    content=content_file.decoded_content.decode("utf-8"),
+                    metadata={"sha": entry.sha},
+                    updated_at=content_file.last_modified_datetime,
+                )
+        logger.info(
+            "[GitHubArtifactStore] loaded {} artifacts from {}",
+            len(self),
+            self.root,
+        )
+        return self
+
+    async def read_artifact(self, path: str) -> Artifact[str]:
+        """Fetch an artifact by path from the cache.
+
+        Cache-only — does not hit the GitHub API. Call `refresh()` to
+        re-sync after external changes to the repo.
+
+        Args:
+            path: Path of the artifact to load (e.g. "contexts/role.md").
+
+        Returns:
+            The artifact including its content.
+
+        Raises:
+            KeyError: If the artifact is not in the cache — call
+                `load_artifacts()` or `refresh()` first.
+        """
+        return self[path]
+
+    async def write_artifact(self, artifact: Artifact[str]) -> Artifact[str]:
+        """Persist an artifact to the repo as a commit.
+
+        Args:
+            artifact: Artifact to write. Commit message comes from
+                `artifact.metadata["commit_message"]` if set, else
+                "Update {path}".
+
+        Returns:
+            Stored artifact with refreshed `metadata["sha"]` and
+            `updated_at` from the new commit.
+        """
+        full_path = str(PurePosixPath(self.path_prefix) / artifact.path) if self.path_prefix else artifact.path
+        message = artifact.metadata.get("commit_message") or f"Update {artifact.path}"
+
+        cached = self._artifacts.get(artifact.path)
+        # Fast-path: skip write if content is unchanged vs. cache — avoids a
+        # spurious commit with identical tree.
+        if cached and cached.content == artifact.content:
+            logger.debug(
+                "[GitHubArtifactStore] no-op write (unchanged): {}",
+                artifact.path,
+            )
+            return cached
+        sha = cached.metadata.get("sha") if cached else None
+
+        with self._client() as gh:
+            repo = gh.get_repo(self.repo_name)
+
+            # Probe remote if we don't already know the sha
+            if sha is None:
+                try:
+                    sha = repo.get_contents(full_path, ref=self.branch).sha
+                except UnknownObjectException:
+                    pass  # stays None → will create
+
+            common = dict(
+                path=full_path,
+                message=message,
+                content=artifact.content,
+                branch=self.branch,
+            )
+            result = repo.update_file(sha=sha, **common) if sha else repo.create_file(**common)
+
+        stored = artifact.model_copy(
+            update={
+                "metadata": {**artifact.metadata, "sha": result["content"].sha},
+                "updated_at": datetime.now(timezone.utc),
+            }
+        )
+        self[artifact.path] = stored
+        logger.info(
+            "[GitHubArtifactStore] wrote: {} (sha={})",
+            stored.path,
+            result["content"].sha,
+        )
+        return stored
diff --git a/tests/artifacts/test_github.py b/tests/artifacts/test_github.py
new file mode 100644
index 0000000..aac02c8
--- /dev/null
+++ b/tests/artifacts/test_github.py
@@ -0,0 +1,79 @@
+"""Barebone mocked tests for GitHubArtifactStore: load, read, write.
+
+Uses the `github_client` injection kwarg rather than patching — see
+`GitHubArtifactStore.__init__` docstring.
+"""
+
+from unittest.mock import MagicMock
+
+import pytest
+from github import UnknownObjectException
+
+from akd_ext.artifacts import Artifact
+from akd_ext.artifacts.stores.github import GitHubArtifactStore
+
+
+def _tree_entry(path: str, sha: str, type_: str = "blob"):
+    e = MagicMock()
+    e.path = path
+    e.sha = sha
+    e.type = type_
+    return e
+
+
+def _content_file(content: str, sha: str):
+    cf = MagicMock()
+    cf.decoded_content = content.encode()
+    cf.sha = sha
+    cf.last_modified_datetime = None
+    return cf
+
+
+@pytest.fixture
+def mock_github():
+    """Return (github_client_mock, repo_mock) for tests to configure."""
+    gh = MagicMock()
+    repo = gh.get_repo.return_value
+    return gh, repo
+
+
+async def test_load(mock_github):
+    gh, repo = mock_github
+    repo.get_git_tree.return_value.tree = [
+        _tree_entry("index.md", "sha1"),
+        _tree_entry("data.json", "sha2"),  # filtered by supported_extensions
+    ]
+    repo.get_contents.return_value = _content_file("root", "sha1")
+
+    store = await GitHubArtifactStore("akd/test", github_client=gh).load_artifacts()
+
+    assert "index.md" in store
+    assert "data.json" not in store
+    assert store["index.md"].metadata["sha"] == "sha1"
+
+
+async def test_read(mock_github):
+    gh, repo = mock_github
+    repo.get_git_tree.return_value.tree = []
+    store = await GitHubArtifactStore("akd/test", github_client=gh).load_artifacts()
+    store["foo.md"] = Artifact(path="foo.md", content="hi")
+
+    got = await store.read_artifact("foo.md")
+    assert got.content == "hi"
+
+
+async def test_write(mock_github):
+    gh, repo = mock_github
+    repo.get_git_tree.return_value.tree = []
+    repo.get_contents.side_effect = UnknownObjectException(404, {}, {})
+    repo.create_file.return_value = {
+        "content": _content_file("new", "new_sha"),
+        "commit": MagicMock(),
+    }
+
+    store = await GitHubArtifactStore("akd/test", github_client=gh).load_artifacts()
+    stored = await store.write_artifact(Artifact(path="new.md", content="hello"))
+
+    repo.create_file.assert_called_once()
+    assert stored.metadata["sha"] == "new_sha"
+    assert "new.md" in store