simplify(skills): remove GitHub URL resolution per maintainer feedback

Per review comment, Skill.from_url() should not be opinionated about
URL format. Remove all resolve_to_raw_url logic — the method now simply
GETs the provided URL and passes content to from_content(). Users are
responsible for providing a direct link to raw SKILL.md content.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Davide Gallitelli

src/strands/vended_plugins/skills/_url_loader.py

@@ -1,23 +1,19 @@
 """Utilities for loading skills from HTTPS URLs.
 
-This module provides functions to detect URL-type skill sources, resolve
-GitHub web URLs to raw content URLs, and fetch SKILL.md content over HTTPS.
-No git dependency or local caching is required.
+This module provides functions to detect URL-type skill sources and
+fetch SKILL.md content over HTTPS.  No git dependency, local caching,
+or URL resolution is required — callers provide a direct URL to the
+raw SKILL.md content.
 """
 
 from __future__ import annotations
 
 import logging
-import re
 import urllib.error
 import urllib.request
 
 logger = logging.getLogger(__name__)
 
-# Matches GitHub /tree/<ref>/path and /blob/<ref>/path URLs.
-# e.g. /owner/repo/tree/main/skills/my-skill -> groups: (owner/repo, main, skills/my-skill)
-_GITHUB_TREE_PATTERN = re.compile(r"^/([^/]+/[^/]+)/(?:tree|blob)/([^/]+)(?:/(.+?))?/?$")
-
 
 def is_url(source: str) -> bool:
     """Check whether a skill source string looks like an HTTPS URL.
@@ -34,93 +30,15 @@ def is_url(source: str) -> bool:
     return source.startswith("https://")
 
 
-def resolve_to_raw_url(url: str) -> str:
-    """Resolve a GitHub web URL to a raw content URL for SKILL.md.
-
-    Supports several GitHub URL patterns and converts them to
-    ``raw.githubusercontent.com`` URLs::
-
-        # Repository root (assumes HEAD and SKILL.md at root)
-        https://github.com/owner/repo
-            -> https://raw.githubusercontent.com/owner/repo/HEAD/SKILL.md
-
-        # Repository root with @ref
-        https://github.com/owner/repo@v1.0
-            -> https://raw.githubusercontent.com/owner/repo/v1.0/SKILL.md
-
-        # Tree URL pointing to a directory
-        https://github.com/owner/repo/tree/main/skills/my-skill
-            -> https://raw.githubusercontent.com/owner/repo/main/skills/my-skill/SKILL.md
-
-        # Blob URL pointing to SKILL.md directly
-        https://github.com/owner/repo/blob/main/skills/my-skill/SKILL.md
-            -> https://raw.githubusercontent.com/owner/repo/main/skills/my-skill/SKILL.md
-
-    Non-GitHub URLs and ``raw.githubusercontent.com`` URLs are returned as-is,
-    so they must point directly to a raw SKILL.md file.
-
-    Args:
-        url: An HTTPS URL, possibly a GitHub web URL.
-
-    Returns:
-        A URL that can be fetched directly to obtain SKILL.md content.
-    """
-    # Already a raw URL — return as-is
-    if "raw.githubusercontent.com" in url:
-        return url
-
-    # Not a github.com URL — return as-is (user provides a direct link)
-    if not url.startswith("https://github.com"):
-        return url
-
-    # Parse the path portion
-    path_start = len("https://github.com")
-    path = url[path_start:]
-
-    # Handle /tree/<ref>/path and /blob/<ref>/path
-    tree_match = _GITHUB_TREE_PATTERN.match(path)
-    if tree_match:
-        owner_repo = tree_match.group(1)
-        ref = tree_match.group(2)
-        subpath = tree_match.group(3) or ""
-
-        # If the URL points to a SKILL.md file directly, use it as-is
-        if subpath.lower().endswith("skill.md"):
-            return f"https://raw.githubusercontent.com/{owner_repo}/{ref}/{subpath}"
-
-        # Otherwise, assume it's a directory and append SKILL.md
-        if subpath:
-            return f"https://raw.githubusercontent.com/{owner_repo}/{ref}/{subpath}/SKILL.md"
-        return f"https://raw.githubusercontent.com/{owner_repo}/{ref}/SKILL.md"
-
-    # Handle plain repo URL: /owner/repo or /owner/repo@ref
-    # Strip leading slash and any trailing slash
-    clean_path = path.strip("/")
-
-    # Check for @ref suffix
-    if "@" in clean_path:
-        at_idx = clean_path.rfind("@")
-        owner_repo = clean_path[:at_idx]
-        ref = clean_path[at_idx + 1 :]
-    else:
-        owner_repo = clean_path
-        ref = "HEAD"
-
-    # Only match owner/repo (exactly two path segments)
-    if owner_repo.count("/") == 1:
-        return f"https://raw.githubusercontent.com/{owner_repo}/{ref}/SKILL.md"
-
-    # Unrecognised GitHub URL pattern — return as-is
-    return url
-
-
 def fetch_skill_content(url: str) -> str:
     """Fetch SKILL.md content from an HTTPS URL.
 
     Uses ``urllib.request`` (stdlib) so no additional dependencies are needed.
 
     Args:
-        url: The HTTPS URL to fetch.
+        url: The HTTPS URL to fetch.  Must point directly to the raw
+            SKILL.md content (for example,
+            ``https://raw.githubusercontent.com/org/repo/main/SKILL.md``).
 
     Returns:
         The response body as a string.
@@ -132,15 +50,14 @@ def fetch_skill_content(url: str) -> str:
     if not url.startswith("https://"):
         raise ValueError(f"url=<{url}> | only https:// URLs are supported")
 
-    resolved = resolve_to_raw_url(url)
-    logger.info("url=<%s> | fetching skill content from %s", url, resolved)
+    logger.info("url=<%s> | fetching skill content", url)
 
     try:
-        req = urllib.request.Request(resolved, headers={"User-Agent": "strands-agents-sdk"})  # noqa: S310
+        req = urllib.request.Request(url, headers={"User-Agent": "strands-agents-sdk"})  # noqa: S310
         with urllib.request.urlopen(req, timeout=30) as response:  # noqa: S310
             content: str = response.read().decode("utf-8")
             return content
     except urllib.error.HTTPError as e:
-        raise RuntimeError(f"url=<{resolved}> | HTTP {e.code}: {e.reason}") from e
+        raise RuntimeError(f"url=<{url}> | HTTP {e.code}: {e.reason}") from e
     except urllib.error.URLError as e:
-        raise RuntimeError(f"url=<{resolved}> | failed to fetch skill: {e.reason}") from e
+        raise RuntimeError(f"url=<{url}> | failed to fetch skill: {e.reason}") from e

src/strands/vended_plugins/skills/skill.py

@@ -337,26 +337,18 @@ def from_content(cls, content: str, *, strict: bool = False) -> Skill:
     def from_url(cls, url: str, *, strict: bool = False) -> Skill:
         """Load a skill by fetching its SKILL.md content from an HTTPS URL.
 
-        Fetches the SKILL.md content over HTTPS and parses it using
-        :meth:`from_content`.  GitHub web URLs are automatically resolved
-        to ``raw.githubusercontent.com``::
+        Fetches the raw SKILL.md content over HTTPS and parses it using
+        :meth:`from_content`.  The URL must point directly to the raw
+        file content (not an HTML page).
 
-            # Direct raw URL
-            skill = Skill.from_url(
-                "https://raw.githubusercontent.com/org/repo/main/SKILL.md"
-            )
+        Example::
 
-            # GitHub web URL (auto-resolved)
             skill = Skill.from_url(
-                "https://github.com/org/repo/tree/main/skills/my-skill"
+                "https://raw.githubusercontent.com/org/repo/main/SKILL.md"
             )
 
-            # Repository root with @ref
-            skill = Skill.from_url("https://github.com/org/my-skill@v1.0.0")
-
         Args:
-            url: An ``https://`` URL pointing to a SKILL.md file, a GitHub
-                repository, or a GitHub ``/tree/<ref>/path`` URL.
+            url: An ``https://`` URL pointing directly to raw SKILL.md content.
             strict: If True, raise on any validation issue. If False (default),
                 warn and load anyway.
 

tests/strands/vended_plugins/skills/test_skill.py

@@ -571,24 +571,6 @@ def test_from_url_returns_skill(self):
         assert "Remote instructions." in skill.instructions
         assert skill.path is None
 
-    def test_from_url_github_web_url(self):
-        """Test that GitHub web URLs are handled (resolved in fetch_skill_content)."""
-        from unittest.mock import patch
-
-        with patch(f"{self._URL_LOADER}.fetch_skill_content", return_value=self._SAMPLE_CONTENT):
-            skill = Skill.from_url("https://github.com/org/repo/tree/main/skills/my-skill")
-
-        assert skill.name == "my-skill"
-
-    def test_from_url_with_ref(self):
-        """Test URL with @ref suffix."""
-        from unittest.mock import patch
-
-        with patch(f"{self._URL_LOADER}.fetch_skill_content", return_value=self._SAMPLE_CONTENT):
-            skill = Skill.from_url("https://github.com/org/my-skill@v1.0.0")
-
-        assert skill.name == "my-skill"
-
     def test_from_url_invalid_url_raises(self):
         """Test that a non-HTTPS URL raises ValueError."""
         with pytest.raises(ValueError, match="not a valid HTTPS URL"):

tests/strands/vended_plugins/skills/test_url_loader.py

@@ -10,30 +10,27 @@
 from strands.vended_plugins.skills._url_loader import (
     fetch_skill_content,
     is_url,
-    resolve_to_raw_url,
 )
 
 
 class TestIsUrl:
     """Tests for is_url."""
 
     def test_https_url(self):
-        assert is_url("https://github.com/org/skill-repo") is True
+        assert is_url("https://example.com/SKILL.md") is True
 
-    def test_https_raw_url(self):
+    def test_https_raw_github_url(self):
         assert is_url("https://raw.githubusercontent.com/org/repo/main/SKILL.md") is True
 
     def test_http_rejected(self):
         """Plaintext http:// is rejected for security."""
-        assert is_url("http://github.com/org/skill-repo") is False
+        assert is_url("http://example.com/SKILL.md") is False
 
     def test_ssh_rejected(self):
-        """SSH URLs are not supported in HTTPS-only mode."""
-        assert is_url("ssh://git@github.com/org/skill-repo") is False
+        assert is_url("ssh://git@github.com/org/repo") is False
 
     def test_git_at_rejected(self):
-        """git@ URLs are not supported in HTTPS-only mode."""
-        assert is_url("git@github.com:org/skill-repo.git") is False
+        assert is_url("git@github.com:org/repo.git") is False
 
     def test_local_relative_path(self):
         assert is_url("./skills/my-skill") is False
@@ -48,78 +45,6 @@ def test_empty_string(self):
         assert is_url("") is False
 
 
-class TestResolveToRawUrl:
-    """Tests for resolve_to_raw_url."""
-
-    def test_raw_url_passthrough(self):
-        url = "https://raw.githubusercontent.com/org/repo/main/SKILL.md"
-        assert resolve_to_raw_url(url) == url
-
-    def test_non_github_passthrough(self):
-        url = "https://example.com/skills/SKILL.md"
-        assert resolve_to_raw_url(url) == url
-
-    def test_repo_root(self):
-        assert resolve_to_raw_url("https://github.com/org/repo") == (
-            "https://raw.githubusercontent.com/org/repo/HEAD/SKILL.md"
-        )
-
-    def test_repo_root_trailing_slash(self):
-        assert resolve_to_raw_url("https://github.com/org/repo/") == (
-            "https://raw.githubusercontent.com/org/repo/HEAD/SKILL.md"
-        )
-
-    def test_repo_root_with_ref(self):
-        assert resolve_to_raw_url("https://github.com/org/repo@v1.0.0") == (
-            "https://raw.githubusercontent.com/org/repo/v1.0.0/SKILL.md"
-        )
-
-    def test_repo_root_with_branch_ref(self):
-        assert resolve_to_raw_url("https://github.com/org/repo@main") == (
-            "https://raw.githubusercontent.com/org/repo/main/SKILL.md"
-        )
-
-    def test_tree_url_directory(self):
-        assert resolve_to_raw_url("https://github.com/org/repo/tree/main/skills/my-skill") == (
-            "https://raw.githubusercontent.com/org/repo/main/skills/my-skill/SKILL.md"
-        )
-
-    def test_tree_url_branch_only(self):
-        assert resolve_to_raw_url("https://github.com/org/repo/tree/main") == (
-            "https://raw.githubusercontent.com/org/repo/main/SKILL.md"
-        )
-
-    def test_tree_url_trailing_slash(self):
-        assert resolve_to_raw_url("https://github.com/org/repo/tree/main/skills/my-skill/") == (
-            "https://raw.githubusercontent.com/org/repo/main/skills/my-skill/SKILL.md"
-        )
-
-    def test_tree_url_with_tag(self):
-        assert resolve_to_raw_url("https://github.com/org/repo/tree/v2.0/skills/brainstorming") == (
-            "https://raw.githubusercontent.com/org/repo/v2.0/skills/brainstorming/SKILL.md"
-        )
-
-    def test_blob_url_to_skill_md(self):
-        assert resolve_to_raw_url("https://github.com/org/repo/blob/main/skills/my-skill/SKILL.md") == (
-            "https://raw.githubusercontent.com/org/repo/main/skills/my-skill/SKILL.md"
-        )
-
-    def test_blob_url_to_lowercase_skill_md(self):
-        assert resolve_to_raw_url("https://github.com/org/repo/blob/main/skills/my-skill/skill.md") == (
-            "https://raw.githubusercontent.com/org/repo/main/skills/my-skill/skill.md"
-        )
-
-    def test_unrecognized_github_path_passthrough(self):
-        """Unrecognized GitHub URL patterns are returned as-is."""
-        url = "https://github.com/org/repo/wiki/Some-Page"
-        assert resolve_to_raw_url(url) == url
-
-    def test_github_deep_unrecognized_path(self):
-        """GitHub URLs with more than owner/repo segments (not tree/blob) pass through."""
-        url = "https://github.com/org/repo/actions/runs/12345"
-        assert resolve_to_raw_url(url) == url
-
-
 class TestFetchSkillContent:
     """Tests for fetch_skill_content."""
 
@@ -139,22 +64,33 @@ def test_fetch_success(self):
 
         assert result == skill_content
 
-    def test_fetch_resolves_github_url(self):
-        """Test that GitHub web URLs are resolved before fetching."""
-        skill_content = "---\nname: test\ndescription: test\n---\n"
+    def test_fetch_uses_url_directly(self):
+        """Test that the URL is used as-is with no resolution."""
+        url = "https://raw.githubusercontent.com/org/repo/main/skills/my-skill/SKILL.md"
 
         mock_response = MagicMock()
-        mock_response.read.return_value = skill_content.encode("utf-8")
+        mock_response.read.return_value = b"---\nname: t\ndescription: t\n---\n"
+        mock_response.__enter__ = MagicMock(return_value=mock_response)
+        mock_response.__exit__ = MagicMock(return_value=False)
+
+        with patch(f"{self._LOADER}.urllib.request.urlopen", return_value=mock_response) as mock_urlopen:
+            fetch_skill_content(url)
+
+        request_obj = mock_urlopen.call_args[0][0]
+        assert request_obj.full_url == url
+
+    def test_fetch_sets_user_agent(self):
+        """Test that requests include a User-Agent header."""
+        mock_response = MagicMock()
+        mock_response.read.return_value = b"---\nname: t\ndescription: t\n---\n"
         mock_response.__enter__ = MagicMock(return_value=mock_response)
         mock_response.__exit__ = MagicMock(return_value=False)
 
         with patch(f"{self._LOADER}.urllib.request.urlopen", return_value=mock_response) as mock_urlopen:
-            fetch_skill_content("https://github.com/org/repo/tree/main/skills/my-skill")
+            fetch_skill_content("https://example.com/SKILL.md")
 
-        # Verify the resolved raw URL was used
-        call_args = mock_urlopen.call_args
-        request_obj = call_args[0][0]
-        assert "raw.githubusercontent.com" in request_obj.full_url
+        request_obj = mock_urlopen.call_args[0][0]
+        assert request_obj.get_header("User-agent") == "strands-agents-sdk"
 
     def test_fetch_http_error(self):
         """Test that HTTP errors raise RuntimeError."""