Validate post-redirect URL scheme before reading response body

Co-authored-by: Copilot Autofix powered by AI <223894421+github-code-quality[bot]@users.noreply.github.com>

src/specify_cli/__init__.py

@@ -2576,7 +2576,7 @@ def preset_list():
 @preset_app.command("add")
 def preset_add(
     preset_id: str = typer.Argument(None, help="Preset ID to install from catalog"),
-    from_url: str = typer.Option(None, "--from", help="Install from a URL (ZIP file)"),
+    from_url: str = typer.Option(None, "--from", help="Install from a URL (ZIP or .tar.gz/.tgz archive)"),
     dev: str = typer.Option(None, "--dev", help="Install from local directory (development mode)"),
     priority: int = typer.Option(10, "--priority", help="Resolution priority (lower = higher precedence, default 10)"),
 ):
@@ -2629,17 +2629,46 @@ def preset_add(
             import urllib.request
             import urllib.error
             import tempfile
+            from .extensions import detect_archive_format as _det_fmt
 
             with tempfile.TemporaryDirectory() as tmpdir:
-                zip_path = Path(tmpdir) / "preset.zip"
+                final_url = from_url
+                archive_fmt = ""
                 try:
                     with urllib.request.urlopen(from_url, timeout=60) as response:
-                        zip_path.write_bytes(response.read())
+                        final_url = response.geturl()
+                        # Re-validate scheme after any redirect (scheme-downgrade
+                        # guard). Check BEFORE reading the body so an insecure
+                        # redirect cannot cause us to fetch the payload.
+                        _fp = _urlparse(final_url)
+                        _fl = _fp.hostname in ("localhost", "127.0.0.1", "::1")
+                        if _fp.scheme != "https" and not (_fp.scheme == "http" and _fl):
+                            console.print(f"[red]Error:[/red] URL was redirected to a non-HTTPS URL: {final_url}")
+                            raise typer.Exit(1)
+                        content_type = response.headers.get("Content-Type", "")
+                        # Prefer the post-redirect URL for format detection;
+                        # fall back to the original URL only as a last hint.
+                        archive_fmt = _det_fmt(final_url, content_type)
+                        if not archive_fmt:
+                            archive_fmt = _det_fmt(from_url)
+                        archive_data = response.read()
                 except urllib.error.URLError as e:
                     console.print(f"[red]Error:[/red] Failed to download: {e}")
                     raise typer.Exit(1)
 
-                manifest = manager.install_from_zip(zip_path, speckit_version, priority)
+                if not archive_fmt:
+                    console.print("[red]Error:[/red] Could not determine archive format from URL or Content-Type.")
+                    console.print("Ensure the URL points to a .zip or .tar.gz/.tgz file.")
+                    raise typer.Exit(1)
+
+                suffix = ".tar.gz" if archive_fmt == "tar.gz" else ".zip"
+                archive_path = Path(tmpdir) / f"preset{suffix}"
+                try:
+                    archive_path.write_bytes(archive_data)
+                    manifest = manager.install_from_zip(archive_path, speckit_version, priority)
+                except OSError as e:
+                    console.print(f"[red]Error:[/red] Failed to save or install archive: {e}")
+                    raise typer.Exit(1)
 
             console.print(f"[green]✓[/green] Preset '{manifest.name}' v{manifest.version} installed (priority {priority})")
 
@@ -3573,7 +3602,7 @@ def catalog_remove(
 def extension_add(
     extension: str = typer.Argument(help="Extension name or path"),
     dev: bool = typer.Option(False, "--dev", help="Install from local directory"),
-    from_url: Optional[str] = typer.Option(None, "--from", help="Install from custom URL"),
+    from_url: Optional[str] = typer.Option(None, "--from", help="Install from custom URL (ZIP or .tar.gz/.tgz archive)"),
     priority: int = typer.Option(10, "--priority", help="Resolution priority (lower = higher precedence, default 10)"),
 ):
     """Install an extension."""
@@ -3612,10 +3641,11 @@ def extension_add(
                 manifest = manager.install_from_directory(source_path, speckit_version, priority=priority)
 
             elif from_url:
-                # Install from URL (ZIP file)
+                # Install from URL (ZIP or tar.gz archive)
                 import urllib.request
                 import urllib.error
                 from urllib.parse import urlparse
+                from .extensions import detect_archive_format
 
                 # Validate URL
                 parsed = urlparse(from_url)
@@ -3631,25 +3661,53 @@ def extension_add(
                 console.print("Only install extensions from sources you trust.\n")
                 console.print(f"Downloading from {from_url}...")
 
-                # Download ZIP to temp location
+                # Download archive to temp location; detect format from the
+                # post-redirect URL (with Content-Type fallback), only using
+                # the original URL as a last hint.
                 download_dir = project_root / ".specify" / "extensions" / ".cache" / "downloads"
                 download_dir.mkdir(parents=True, exist_ok=True)
-                zip_path = download_dir / f"{extension}-url-download.zip"
+                archive_fmt = ""
+                archive_path = None
 
                 try:
                     with urllib.request.urlopen(from_url, timeout=60) as response:
-                        zip_data = response.read()
-                    zip_path.write_bytes(zip_data)
+                        final_url = response.geturl()
+                        # Re-validate scheme after any redirect (scheme-downgrade
+                        # guard). Check BEFORE reading the body so an insecure
+                        # redirect cannot cause us to fetch the payload.
+                        _fp = urlparse(final_url)
+                        _fl = _fp.hostname in ("localhost", "127.0.0.1", "::1")
+                        if _fp.scheme != "https" and not (_fp.scheme == "http" and _fl):
+                            console.print(f"[red]Error:[/red] URL was redirected to a non-HTTPS URL: {final_url}")
+                            raise typer.Exit(1)
+                        content_type = response.headers.get("Content-Type", "")
+                        archive_fmt = detect_archive_format(final_url, content_type)
+                        if not archive_fmt:
+                            archive_fmt = detect_archive_format(from_url)
+                        archive_data = response.read()
 
-                    # Install from downloaded ZIP
-                    manifest = manager.install_from_zip(zip_path, speckit_version, priority=priority)
+                    if not archive_fmt:
+                        console.print("[red]Error:[/red] Could not determine archive format from URL or Content-Type.")
+                        console.print("Ensure the URL points to a .zip or .tar.gz/.tgz file.")
+                        raise typer.Exit(1)
+
+                    suffix = ".tar.gz" if archive_fmt == "tar.gz" else ".zip"
+                    safe_name = Path(extension).name or "extension"
+                    archive_path = download_dir / f"{safe_name}-url-download{suffix}"
+                    archive_path.write_bytes(archive_data)
+
+                    # Install from downloaded archive
+                    manifest = manager.install_from_zip(archive_path, speckit_version, priority=priority)
                 except urllib.error.URLError as e:
                     console.print(f"[red]Error:[/red] Failed to download from {from_url}: {e}")
                     raise typer.Exit(1)
+                except OSError as e:
+                    console.print(f"[red]Error:[/red] Failed to save or install archive: {e}")
+                    raise typer.Exit(1)
                 finally:
-                    # Clean up downloaded ZIP
-                    if zip_path.exists():
-                        zip_path.unlink()
+                    # Clean up the downloaded archive
+                    if archive_path is not None and archive_path.exists():
+                        archive_path.unlink()
 
             else:
                 # Try bundled extensions first (shipped with spec-kit)
@@ -4301,29 +4359,55 @@ def extension_update(
                             backup_hooks[hook_name] = ext_hooks
 
                 # 5. Download new version
-                zip_path = catalog.download_extension(extension_id)
+                archive_path = catalog.download_extension(extension_id)
                 try:
-                    # 6. Validate extension ID from ZIP BEFORE modifying installation
-                    # Handle both root-level and nested extension.yml (GitHub auto-generated ZIPs)
-                    with zipfile.ZipFile(zip_path, "r") as zf:
-                        import yaml
-                        manifest_data = None
-                        namelist = zf.namelist()
+                    # 6. Validate extension ID from archive BEFORE modifying installation
+                    # Handle both root-level and nested extension.yml (GitHub auto-generated archives)
+                    from .extensions import detect_archive_format
+                    import tarfile
+                    archive_fmt = detect_archive_format(str(archive_path))
+                    import yaml
+                    manifest_data = None
 
-                        # First try root-level extension.yml
-                        if "extension.yml" in namelist:
-                            with zf.open("extension.yml") as f:
-                                manifest_data = yaml.safe_load(f) or {}
-                        else:
-                            # Look for extension.yml in a single top-level subdirectory
-                            # (e.g., "repo-name-branch/extension.yml")
-                            manifest_paths = [n for n in namelist if n.endswith("/extension.yml") and n.count("/") == 1]
-                            if len(manifest_paths) == 1:
-                                with zf.open(manifest_paths[0]) as f:
+                    if archive_fmt == "tar.gz":
+                        with tarfile.open(archive_path, "r:gz") as tf:
+                            # First try root-level extension.yml
+                            try:
+                                m = tf.getmember("extension.yml")
+                                f = tf.extractfile(m)
+                                if f is not None:
+                                    with f:
+                                        manifest_data = yaml.safe_load(f.read()) or {}
+                            except KeyError:
+                                # extension.yml not present at archive root; use nested fallback below.
+                                manifest_data = None
+                            # Fall back to nested-directory search if root-level
+                            # was missing (KeyError) or not a regular file (None).
+                            if manifest_data is None:
+                                members = [m for m in tf.getmembers() if m.name.endswith("/extension.yml") and m.name.count("/") == 1]
+                                if len(members) == 1:
+                                    f = tf.extractfile(members[0])
+                                    if f is not None:
+                                        with f:
+                                            manifest_data = yaml.safe_load(f.read()) or {}
+                    else:
+                        with zipfile.ZipFile(archive_path, "r") as zf:
+                            namelist = zf.namelist()
+
+                            # First try root-level extension.yml
+                            if "extension.yml" in namelist:
+                                with zf.open("extension.yml") as f:
                                     manifest_data = yaml.safe_load(f) or {}
+                            else:
+                                # Look for extension.yml in a single top-level subdirectory
+                                # (e.g., "repo-name-branch/extension.yml")
+                                manifest_paths = [n for n in namelist if n.endswith("/extension.yml") and n.count("/") == 1]
+                                if len(manifest_paths) == 1:
+                                    with zf.open(manifest_paths[0]) as f:
+                                        manifest_data = yaml.safe_load(f) or {}
 
-                        if manifest_data is None:
-                            raise ValueError("Downloaded extension archive is missing 'extension.yml'")
+                    if manifest_data is None:
+                        raise ValueError("Downloaded extension archive is missing 'extension.yml'")
 
                     zip_extension_id = manifest_data.get("extension", {}).get("id")
                     if zip_extension_id != extension_id:
@@ -4335,7 +4419,7 @@ def extension_update(
                     manager.remove(extension_id, keep_config=True)
 
                     # 8. Install new version
-                    _ = manager.install_from_zip(zip_path, speckit_version)
+                    _ = manager.install_from_zip(archive_path, speckit_version)
 
                     # Restore user config files from backup after successful install.
                     new_extension_dir = manager.extensions_dir / extension_id
@@ -4381,9 +4465,9 @@ def extension_update(
                                             hook["enabled"] = False
                                 hook_executor.save_project_config(config)
                 finally:
-                    # Clean up downloaded ZIP
-                    if zip_path.exists():
-                        zip_path.unlink()
+                    # Clean up downloaded archive
+                    if archive_path.exists():
+                        archive_path.unlink()
 
                 # 10. Clean up backup on success
                 if backup_base.exists():
@@ -4875,6 +4959,59 @@ def workflow_list():
         console.print()
 
 
+def _extract_workflow_yml(archive_path: Path, archive_fmt: str) -> bytes:
+    """Extract ``workflow.yml`` from a ZIP or ``.tar.gz`` archive.
+
+    Searches the archive root and a single nested top-level subdirectory
+    (e.g., ``repo-name-1.0/workflow.yml``).
+
+    Args:
+        archive_path: Path to the downloaded archive.
+        archive_fmt: ``"zip"`` or ``"tar.gz"``.
+
+    Returns:
+        Raw bytes of the ``workflow.yml`` file.
+
+    Raises:
+        ValueError: If no ``workflow.yml`` is found in the archive.
+    """
+    import tarfile
+
+    if archive_fmt == "tar.gz":
+        with tarfile.open(archive_path, "r:gz") as tf:
+            # Try root-level first.
+            try:
+                f = tf.extractfile(tf.getmember("workflow.yml"))
+                if f is not None:
+                    with f:
+                        return f.read()
+            except KeyError:
+                pass  # Root-level workflow.yml not found; fall through to subdirectory search below.
+            # Look in a single top-level subdirectory.
+            candidates = [
+                m for m in tf.getmembers()
+                if m.name.endswith("/workflow.yml") and m.name.count("/") == 1
+            ]
+            if len(candidates) == 1:
+                f = tf.extractfile(candidates[0])
+                if f is not None:
+                    with f:
+                        return f.read()
+    else:
+        with zipfile.ZipFile(archive_path, "r") as zf:
+            namelist = zf.namelist()
+            if "workflow.yml" in namelist:
+                return zf.read("workflow.yml")
+            candidates = [
+                n for n in namelist
+                if n.endswith("/workflow.yml") and n.count("/") == 1
+            ]
+            if len(candidates) == 1:
+                return zf.read(candidates[0])
+
+    raise ValueError("No workflow.yml found in the downloaded archive")
+
+
 @workflow_app.command("add")
 def workflow_add(
     source: str = typer.Argument(..., help="Workflow ID, URL, or local path"),
@@ -4928,6 +5065,7 @@ def workflow_add(
         from ipaddress import ip_address
         from urllib.parse import urlparse
         from urllib.request import urlopen  # noqa: S310
+        from .extensions import detect_archive_format
 
         parsed_src = urlparse(source)
         src_host = parsed_src.hostname or ""
@@ -4958,18 +5096,53 @@ def workflow_add(
                 if final_parsed.scheme != "https" and not (final_parsed.scheme == "http" and final_lb):
                     console.print(f"[red]Error:[/red] URL redirected to non-HTTPS: {final_url}")
                     raise typer.Exit(1)
-                with tempfile.NamedTemporaryFile(suffix=".yml", delete=False) as tmp:
-                    tmp.write(resp.read())
-                    tmp_path = Path(tmp.name)
+
+                # Detect archive format from the final URL or Content-Type header.
+                archive_fmt = detect_archive_format(final_url)
+                if not archive_fmt:
+                    content_type = resp.headers.get("Content-Type", "")
+                    archive_fmt = detect_archive_format(final_url, content_type)
+
+                raw_data = resp.read()
         except typer.Exit:
             raise
         except Exception as exc:
             console.print(f"[red]Error:[/red] Failed to download workflow: {exc}")
             raise typer.Exit(1)
+
+        tmp_path = None
+        try:
+            if archive_fmt in ("tar.gz", "zip"):
+                # Extract workflow.yml from the archive.
+                suffix = ".tar.gz" if archive_fmt == "tar.gz" else ".zip"
+                arc_tmp_path = None
+                with tempfile.NamedTemporaryFile(suffix=suffix, delete=False) as arc_tmp:
+                    arc_tmp_path = Path(arc_tmp.name)
+                    arc_tmp.write(raw_data)
+                try:
+                    wf_yaml = _extract_workflow_yml(arc_tmp_path, archive_fmt)
+                    with tempfile.NamedTemporaryFile(suffix=".yml", delete=False) as tmp:
+                        tmp_path = Path(tmp.name)
+                        tmp.write(wf_yaml)
+                finally:
+                    if arc_tmp_path is not None:
+                        arc_tmp_path.unlink(missing_ok=True)
+            else:
+                # Treat as a plain YAML file (existing behaviour).
+                with tempfile.NamedTemporaryFile(suffix=".yml", delete=False) as tmp:
+                    tmp.write(raw_data)
+                    tmp_path = Path(tmp.name)
+        except typer.Exit:
+            raise
+        except Exception as exc:
+            console.print(f"[red]Error:[/red] Failed to process downloaded workflow: {exc}")
+            raise typer.Exit(1)
+
         try:
             _validate_and_install_local(tmp_path, source)
         finally:
-            tmp_path.unlink(missing_ok=True)
+            if tmp_path is not None:
+                tmp_path.unlink(missing_ok=True)
         return
 
     # Try as a local file/directory
@@ -4978,6 +5151,27 @@ def workflow_add(
         if source_path.is_file() and source_path.suffix in (".yml", ".yaml"):
             _validate_and_install_local(source_path, str(source_path))
             return
+        elif source_path.is_file() and (
+            source.lower().endswith(".tar.gz") or source.lower().endswith(".tgz") or source.lower().endswith(".zip")
+        ):
+            # Local archive file containing workflow.yml
+            from .extensions import detect_archive_format
+            local_fmt = detect_archive_format(source)
+            try:
+                wf_yaml = _extract_workflow_yml(source_path, local_fmt)
+            except Exception as exc:
+                console.print(f"[red]Error:[/red] Failed to extract workflow from archive: {exc}")
+                raise typer.Exit(1)
+            import tempfile
+            tmp_local = None
+            with tempfile.NamedTemporaryFile(suffix=".yml", delete=False) as tmp:
+                tmp_local = Path(tmp.name)
+                tmp.write(wf_yaml)
+            try:
+                _validate_and_install_local(tmp_local, str(source_path))
+            finally:
+                tmp_local.unlink(missing_ok=True)
+            return
         elif source_path.is_dir():
             wf_file = source_path / "workflow.yml"
             if not wf_file.exists():
@@ -5041,6 +5235,7 @@ def workflow_add(
 
     try:
         from urllib.request import urlopen  # noqa: S310 — URL comes from catalog
+        from .extensions import detect_archive_format
 
         workflow_dir.mkdir(parents=True, exist_ok=True)
         with urlopen(workflow_url, timeout=30) as response:  # noqa: S310
@@ -5063,7 +5258,32 @@ def workflow_add(
                     f"[red]Error:[/red] Workflow '{source}' redirected to non-HTTPS URL: {final_url}"
                 )
                 raise typer.Exit(1)
-            workflow_file.write_bytes(response.read())
+
+            # Detect archive format from the final URL or Content-Type header.
+            cat_archive_fmt = detect_archive_format(final_url)
+            if not cat_archive_fmt:
+                cat_ct = response.headers.get("Content-Type", "")
+                cat_archive_fmt = detect_archive_format(final_url, cat_ct)
+
+            raw_response = response.read()
+
+        if cat_archive_fmt in ("tar.gz", "zip"):
+            # Download URL points to an archive — extract workflow.yml from it.
+            suffix = ".tar.gz" if cat_archive_fmt == "tar.gz" else ".zip"
+            arc_tmp = None
+            with tempfile.NamedTemporaryFile(suffix=suffix, delete=False) as arc_f:
+                arc_tmp = Path(arc_f.name)
+                arc_f.write(raw_response)
+            try:
+                wf_yaml_bytes = _extract_workflow_yml(arc_tmp, cat_archive_fmt)
+            finally:
+                if arc_tmp is not None:
+                    arc_tmp.unlink(missing_ok=True)
+            workflow_file.write_bytes(wf_yaml_bytes)
+        else:
+            workflow_file.write_bytes(raw_response)
+    except typer.Exit:
+        raise
     except Exception as exc:
         if workflow_dir.exists():
             import shutil

src/specify_cli/extensions.py

@@ -9,6 +9,8 @@ without bloating the core framework.
 import json
 import hashlib
 import os
+import sys
+import tarfile
 import tempfile
 import zipfile
 import shutil
@@ -106,6 +108,137 @@ def normalize_priority(value: Any, default: int = 10) -> int:
     return priority if priority >= 1 else default
 
 
+def detect_archive_format(url: str, content_type: str = "") -> str:
+    """Detect archive format from URL path extension or Content-Type header.
+
+    Args:
+        url: URL or file path to inspect.
+        content_type: Optional ``Content-Type`` header value from the HTTP response.
+
+    Returns:
+        ``"zip"`` for ZIP archives, ``"tar.gz"`` for gzipped tarballs, or ``""``
+        when the format cannot be determined.
+    """
+    # Strip query-string / fragment before examining the path extension.
+    url_path = url.split("?")[0].split("#")[0].lower()
+    if url_path.endswith(".zip"):
+        return "zip"
+    if url_path.endswith(".tar.gz") or url_path.endswith(".tgz"):
+        return "tar.gz"
+
+    # Fall back to Content-Type header inspection.
+    ct = content_type.lower()
+    if "application/zip" in ct or "application/x-zip" in ct:
+        return "zip"
+    if any(
+        t in ct
+        for t in (
+            "application/gzip",
+            "application/x-gzip",
+            "application/x-tar+gzip",
+        )
+    ):
+        return "tar.gz"
+
+    return ""
+
+
+def safe_extract_tarball(
+    archive_path: Path,
+    dest_dir: Path,
+    error_class: "type[Exception]" = Exception,
+) -> None:
+    """Safely extract a ``.tar.gz`` or ``.tgz`` archive into *dest_dir*.
+
+    All members are validated before extraction to prevent *tar slip*
+    (path traversal) attacks.  Symlinks, hard links, and special files
+    (devices, FIFOs, etc.) are rejected.
+
+    On Python 3.12 and later the ``"data"`` extraction filter is applied
+    for an additional layer of OS-level protection.  On earlier versions
+    the explicit member list (containing only pre-validated regular files
+    and directories) is passed to ``extractall()`` — since all symlinks are
+    already rejected in the validation phase, no archive-introduced symlink
+    can be followed during extraction.
+
+    Args:
+        archive_path: Path to the ``.tar.gz``/``.tgz`` archive.
+        dest_dir: Destination directory (must already exist).
+        error_class: Exception class to raise on unsafe entries.
+
+    Raises:
+        error_class: If any member is unsafe or the archive cannot be read.
+    """
+    dest_resolved = dest_dir.resolve()
+    # Tar metadata member types to skip during validation — they carry no
+    # extractable payload and are generated automatically by many common
+    # archiving tools (e.g. PAX headers, GNU longname/longlink entries).
+    # GNUTYPE_SPARSE is intentionally excluded: it carries a real file payload
+    # and tarfile.TarInfo.isreg() returns True for it, so it passes the
+    # regular-file check below and is extracted correctly.
+    _TAR_METADATA_TYPES = (
+        tarfile.XHDTYPE,           # PAX extended header
+        tarfile.XGLTYPE,           # PAX global extended header
+        tarfile.SOLARIS_XHDTYPE,   # Solaris PAX extended header
+        tarfile.GNUTYPE_LONGNAME,  # GNU long path name (metadata only)
+        tarfile.GNUTYPE_LONGLINK,  # GNU long link name (metadata only)
+    )
+
+    try:
+        with tarfile.open(archive_path, "r:gz") as tf:
+            members = tf.getmembers()
+            safe_members = []
+
+            # Validate every member before extracting anything.
+            for member in members:
+                # Reject absolute paths and any path component that is "..".
+                if os.path.isabs(member.name) or any(
+                    part == ".." for part in member.name.replace("\\", "/").split("/")
+                ):
+                    raise error_class(
+                        f"Unsafe path in tar archive: {member.name} (potential path traversal)"
+                    )
+
+                # Confirm the resolved path stays inside dest_dir.
+                member_path = (dest_dir / member.name).resolve()
+                try:
+                    member_path.relative_to(dest_resolved)
+                except ValueError:
+                    raise error_class(
+                        f"Unsafe path in tar archive: {member.name} (potential path traversal)"
+                    )
+
+                # Skip tar metadata members — they carry no extractable payload.
+                if member.type in _TAR_METADATA_TYPES:
+                    continue
+
+                # Reject symlinks and hard links.
+                if member.issym() or member.islnk():
+                    raise error_class(
+                        f"Symlinks are not allowed in archive: {member.name}"
+                    )
+
+                # Reject devices, FIFOs and other special file types.
+                if not (member.isreg() or member.isdir()):
+                    raise error_class(
+                        f"Non-regular file in archive: {member.name}"
+                    )
+
+                safe_members.append(member)
+
+            # Extract — use the "data" filter on Python 3.12+ for extra hardening.
+            # On all versions pass only the pre-validated members so that no
+            # unvetted entry (added concurrently or via a race) slips through.
+            if sys.version_info >= (3, 12):
+                tf.extractall(dest_dir, members=safe_members, filter="data")  # type: ignore[call-arg]
+            else:
+                tf.extractall(dest_dir, members=safe_members)  # noqa: S202 — validated above
+    except error_class:
+        raise
+    except (tarfile.TarError, OSError) as e:
+        raise error_class(f"Failed to read archive {archive_path}: {e}") from e
+
+
 @dataclass
 class CatalogEntry:
     """Represents a single catalog entry in the catalog stack."""
@@ -1202,10 +1335,10 @@ class ExtensionManager:
         speckit_version: str,
         priority: int = 10,
     ) -> ExtensionManifest:
-        """Install extension from ZIP file.
+        """Install extension from a ZIP or ``.tar.gz``/``.tgz`` archive.
 
         Args:
-            zip_path: Path to extension ZIP file
+            zip_path: Path to the extension archive (ZIP or gzipped tarball).
             speckit_version: Current spec-kit version
             priority: Resolution priority (lower = higher precedence, default 10)
 
@@ -1213,7 +1346,8 @@ class ExtensionManager:
             Installed extension manifest
 
         Raises:
-            ValidationError: If manifest is invalid or priority is invalid
+            ValidationError: If manifest is invalid, the archive is unsafe, or
+                priority is invalid
             CompatibilityError: If extension is incompatible
         """
         # Validate priority early
@@ -1223,21 +1357,27 @@ class ExtensionManager:
         with tempfile.TemporaryDirectory() as tmpdir:
             temp_path = Path(tmpdir)
 
-            # Extract ZIP safely (prevent Zip Slip attack)
-            with zipfile.ZipFile(zip_path, 'r') as zf:
-                # Validate all paths first before extracting anything
-                temp_path_resolved = temp_path.resolve()
-                for member in zf.namelist():
-                    member_path = (temp_path / member).resolve()
-                    # Use is_relative_to for safe path containment check
-                    try:
-                        member_path.relative_to(temp_path_resolved)
-                    except ValueError:
-                        raise ValidationError(
-                            f"Unsafe path in ZIP archive: {member} (potential path traversal)"
-                        )
-                # Only extract after all paths are validated
-                zf.extractall(temp_path)
+            archive_fmt = detect_archive_format(str(zip_path))
+
+            if archive_fmt == "tar.gz":
+                # Extract tarball safely (prevent tar slip attack)
+                safe_extract_tarball(zip_path, temp_path, ValidationError)
+            else:
+                # Extract ZIP safely (prevent Zip Slip attack)
+                with zipfile.ZipFile(zip_path, 'r') as zf:
+                    # Validate all paths first before extracting anything
+                    temp_path_resolved = temp_path.resolve()
+                    for member in zf.namelist():
+                        member_path = (temp_path / member).resolve()
+                        # Use is_relative_to for safe path containment check
+                        try:
+                            member_path.relative_to(temp_path_resolved)
+                        except ValueError:
+                            raise ValidationError(
+                                f"Unsafe path in ZIP archive: {member} (potential path traversal)"
+                            )
+                    # Only extract after all paths are validated
+                    zf.extractall(temp_path)
 
             # Find extension directory (may be nested)
             extension_dir = temp_path
@@ -1251,7 +1391,7 @@ class ExtensionManager:
                     manifest_path = extension_dir / "extension.yml"
 
             if not manifest_path.exists():
-                raise ValidationError("No extension.yml found in ZIP file")
+                raise ValidationError("No extension.yml found in archive")
 
             # Install from extracted directory
             return self.install_from_directory(extension_dir, speckit_version, priority=priority)
@@ -1965,14 +2105,18 @@ class ExtensionCatalog:
         return None
 
     def download_extension(self, extension_id: str, target_dir: Optional[Path] = None) -> Path:
-        """Download extension ZIP from catalog.
+        """Download extension archive from catalog.
+
+        Supports both ZIP (``.zip``) and gzipped tarball (``.tar.gz``/``.tgz``)
+        archives.  The format is detected from the download URL's path extension;
+        when ambiguous the ``Content-Type`` header is used as a fallback.
 
         Args:
             extension_id: ID of the extension to download
-            target_dir: Directory to save ZIP file (defaults to temp directory)
+            target_dir: Directory to save the archive (defaults to cache directory)
 
         Returns:
-            Path to downloaded ZIP file
+            Path to downloaded archive file
 
         Raises:
             ExtensionError: If extension not found or download fails
@@ -2011,21 +2155,60 @@ class ExtensionCatalog:
         target_dir.mkdir(parents=True, exist_ok=True)
 
         version = ext_info.get("version", "unknown")
-        zip_filename = f"{extension_id}-{version}.zip"
-        zip_path = target_dir / zip_filename
 
-        # Download the ZIP file
+        # Download the archive. Determine the archive format from the
+        # post-redirect URL first (with Content-Type fallback); only use the
+        # original `download_url` as a last hint if the final URL gives no
+        # signal.
+        final_url = download_url
+        archive_fmt = ""
         try:
             with self._open_url(download_url, timeout=60) as response:
-                zip_data = response.read()
-
-            zip_path.write_bytes(zip_data)
-            return zip_path
+                final_url = response.geturl()
+                # Re-validate scheme after any redirect to guard against
+                # scheme-downgrade. Validate BEFORE reading the body so a
+                # malicious redirect cannot cause us to fetch the payload
+                # over an insecure scheme.
+                _final_parsed = urlparse(final_url)
+                _final_is_localhost = _final_parsed.hostname in (
+                    "localhost",
+                    "127.0.0.1",
+                    "::1",
+                )
+                if _final_parsed.scheme != "https" and not (
+                    _final_parsed.scheme == "http" and _final_is_localhost
+                ):
+                    raise ExtensionError(
+                        f"Extension download URL was redirected to a non-HTTPS URL: {final_url}"
+                    )
+                content_type = response.headers.get("Content-Type", "")
+                archive_fmt = detect_archive_format(final_url, content_type)
+                if not archive_fmt:
+                    archive_fmt = detect_archive_format(download_url)
+                archive_data = response.read()
 
         except urllib.error.URLError as e:
             raise ExtensionError(f"Failed to download extension from {download_url}: {e}")
         except IOError as e:
-            raise ExtensionError(f"Failed to save extension ZIP: {e}")
+            raise ExtensionError(f"Failed to read extension archive from {download_url}: {e}")
+
+        # Choose file extension based on detected format.
+        if not archive_fmt:
+            raise ExtensionError(
+                f"Could not determine archive format for {download_url}. "
+                "Ensure the URL points to a .zip or .tar.gz/.tgz file."
+            )
+        if archive_fmt == "tar.gz":
+            archive_filename = f"{extension_id}-{version}.tar.gz"
+        else:
+            archive_filename = f"{extension_id}-{version}.zip"
+
+        archive_path = target_dir / archive_filename
+        try:
+            archive_path.write_bytes(archive_data)
+        except IOError as e:
+            raise ExtensionError(f"Failed to save extension archive: {e}")
+        return archive_path
 
     def clear_cache(self):
         """Clear the catalog cache (both legacy and URL-hash-based files)."""

src/specify_cli/presets.py

@@ -27,7 +27,7 @@ import yaml
 from packaging import version as pkg_version
 from packaging.specifiers import SpecifierSet, InvalidSpecifier
 
-from .extensions import ExtensionRegistry, normalize_priority
+from .extensions import ExtensionRegistry, normalize_priority, detect_archive_format, safe_extract_tarball
 
 
 def _substitute_core_template(
@@ -1604,10 +1604,10 @@ class PresetManager:
         speckit_version: str,
         priority: int = 10,
     ) -> PresetManifest:
-        """Install preset from ZIP file.
+        """Install preset from a ZIP or ``.tar.gz``/``.tgz`` archive.
 
         Args:
-            zip_path: Path to preset ZIP file
+            zip_path: Path to the preset archive (ZIP or gzipped tarball).
             speckit_version: Current spec-kit version
             priority: Resolution priority (lower = higher precedence, default 10)
 
@@ -1615,7 +1615,8 @@ class PresetManager:
             Installed preset manifest
 
         Raises:
-            PresetValidationError: If manifest is invalid or priority is invalid
+            PresetValidationError: If manifest is invalid, the archive is unsafe,
+                or priority is invalid
             PresetCompatibilityError: If pack is incompatible
         """
         # Validate priority early
@@ -1625,18 +1626,24 @@ class PresetManager:
         with tempfile.TemporaryDirectory() as tmpdir:
             temp_path = Path(tmpdir)
 
-            with zipfile.ZipFile(zip_path, 'r') as zf:
-                temp_path_resolved = temp_path.resolve()
-                for member in zf.namelist():
-                    member_path = (temp_path / member).resolve()
-                    try:
-                        member_path.relative_to(temp_path_resolved)
-                    except ValueError:
-                        raise PresetValidationError(
-                            f"Unsafe path in ZIP archive: {member} "
-                            "(potential path traversal)"
-                        )
-                zf.extractall(temp_path)
+            archive_fmt = detect_archive_format(str(zip_path))
+
+            if archive_fmt == "tar.gz":
+                # Extract tarball safely (prevent tar slip attack)
+                safe_extract_tarball(zip_path, temp_path, PresetValidationError)
+            else:
+                with zipfile.ZipFile(zip_path, 'r') as zf:
+                    temp_path_resolved = temp_path.resolve()
+                    for member in zf.namelist():
+                        member_path = (temp_path / member).resolve()
+                        try:
+                            member_path.relative_to(temp_path_resolved)
+                        except ValueError:
+                            raise PresetValidationError(
+                                f"Unsafe path in ZIP archive: {member} "
+                                "(potential path traversal)"
+                            )
+                    zf.extractall(temp_path)
 
             pack_dir = temp_path
             manifest_path = pack_dir / "preset.yml"
@@ -1649,7 +1656,7 @@ class PresetManager:
 
             if not manifest_path.exists():
                 raise PresetValidationError(
-                    "No preset.yml found in ZIP file"
+                    "No preset.yml found in archive"
                 )
 
             return self.install_from_directory(pack_dir, speckit_version, priority)
@@ -2242,14 +2249,18 @@ class PresetCatalog:
     def download_pack(
         self, pack_id: str, target_dir: Optional[Path] = None
     ) -> Path:
-        """Download preset ZIP from catalog.
+        """Download preset archive from catalog.
+
+        Supports both ZIP (``.zip``) and gzipped tarball (``.tar.gz``/``.tgz``)
+        archives.  The format is detected from the download URL's path extension;
+        when ambiguous the ``Content-Type`` header is used as a fallback.
 
         Args:
             pack_id: ID of the preset to download
-            target_dir: Directory to save ZIP file (defaults to cache directory)
+            target_dir: Directory to save the archive (defaults to cache directory)
 
         Returns:
-            Path to downloaded ZIP file
+            Path to downloaded archive file
 
         Raises:
             PresetError: If pack not found or download fails
@@ -2301,22 +2312,61 @@ class PresetCatalog:
         target_dir.mkdir(parents=True, exist_ok=True)
 
         version = pack_info.get("version", "unknown")
-        zip_filename = f"{pack_id}-{version}.zip"
-        zip_path = target_dir / zip_filename
 
+        # Determine the archive format from the post-redirect URL first
+        # (with Content-Type fallback); only use the original `download_url`
+        # as a last hint if the final URL gives no signal.
+        final_url = download_url
+        archive_fmt = ""
         try:
             with self._open_url(download_url, timeout=60) as response:
-                zip_data = response.read()
-
-            zip_path.write_bytes(zip_data)
-            return zip_path
+                final_url = response.geturl()
+                # Re-validate scheme after any redirect to guard against
+                # scheme-downgrade. Validate BEFORE reading the body so a
+                # malicious redirect cannot cause us to fetch the payload
+                # over an insecure scheme.
+                _final_parsed = urlparse(final_url)
+                _final_is_localhost = _final_parsed.hostname in (
+                    "localhost",
+                    "127.0.0.1",
+                    "::1",
+                )
+                if _final_parsed.scheme != "https" and not (
+                    _final_parsed.scheme == "http" and _final_is_localhost
+                ):
+                    raise PresetError(
+                        f"Preset download URL was redirected to a non-HTTPS URL: {final_url}"
+                    )
+                content_type = response.headers.get("Content-Type", "")
+                archive_fmt = detect_archive_format(final_url, content_type)
+                if not archive_fmt:
+                    archive_fmt = detect_archive_format(download_url)
+                archive_data = response.read()
 
         except urllib.error.URLError as e:
             raise PresetError(
                 f"Failed to download preset from {download_url}: {e}"
             )
         except IOError as e:
-            raise PresetError(f"Failed to save preset ZIP: {e}")
+            raise PresetError(f"Failed to read preset archive from {download_url}: {e}")
+
+        # Choose file extension based on detected format.
+        if not archive_fmt:
+            raise PresetError(
+                f"Could not determine archive format for {download_url}. "
+                "Ensure the URL points to a .zip or .tar.gz/.tgz file."
+            )
+        if archive_fmt == "tar.gz":
+            archive_filename = f"{pack_id}-{version}.tar.gz"
+        else:
+            archive_filename = f"{pack_id}-{version}.zip"
+
+        archive_path = target_dir / archive_filename
+        try:
+            archive_path.write_bytes(archive_data)
+        except IOError as e:
+            raise PresetError(f"Failed to save preset archive: {e}")
+        return archive_path
 
     def clear_cache(self):
         """Clear all catalog cache files, including per-URL hashed caches."""

tests/test_extensions.py

@@ -178,6 +178,47 @@ class TestNormalizePriority:
         assert normalize_priority("invalid", default=1) == 1
 
 
+# ===== detect_archive_format Tests =====
+
+class TestDetectArchiveFormat:
+    """Test the detect_archive_format helper."""
+
+    def _fmt(self, url, ct=""):
+        from specify_cli.extensions import detect_archive_format
+        return detect_archive_format(url, ct)
+
+    def test_zip_url_extension(self):
+        assert self._fmt("https://example.com/ext-1.0.0.zip") == "zip"
+
+    def test_tar_gz_url_extension(self):
+        assert self._fmt("https://example.com/ext-1.0.0.tar.gz") == "tar.gz"
+
+    def test_tgz_url_extension(self):
+        assert self._fmt("https://example.com/ext-1.0.0.tgz") == "tar.gz"
+
+    def test_zip_uppercase_url_extension(self):
+        assert self._fmt("https://example.com/ext.ZIP") == "zip"
+
+    def test_tar_gz_with_query_string(self):
+        assert self._fmt("https://example.com/ext.tar.gz?token=abc") == "tar.gz"
+
+    def test_zip_content_type_fallback(self):
+        assert self._fmt("https://example.com/download", "application/zip") == "zip"
+
+    def test_gzip_content_type_fallback(self):
+        assert self._fmt("https://example.com/download", "application/gzip") == "tar.gz"
+
+    def test_x_gzip_content_type_fallback(self):
+        assert self._fmt("https://example.com/download", "application/x-gzip") == "tar.gz"
+
+    def test_unknown_returns_empty_string(self):
+        assert self._fmt("https://example.com/workflow.yml") == ""
+
+    def test_url_extension_takes_precedence_over_content_type(self):
+        # URL says .zip — content-type claiming gzip should not override.
+        assert self._fmt("https://example.com/ext.zip", "application/gzip") == "zip"
+
+
 # ===== ExtensionManifest Tests =====
 
 class TestExtensionManifest:
@@ -1013,6 +1054,97 @@ class TestExtensionManager:
         assert backup_file.read_text() == "test: config"
 
 
+# ===== install_from_zip Tarball Tests =====
+
+class TestInstallFromTarball:
+    """Tests for install_from_zip accepting .tar.gz/.tgz archives."""
+
+    def _make_tarball(self, dest: Path, extension_dir: Path, nested: bool = False) -> None:
+        """Create a minimal .tar.gz archive from *extension_dir*."""
+        import tarfile
+        with tarfile.open(dest, "w:gz") as tf:
+            for file_path in extension_dir.rglob("*"):
+                if file_path.is_file():
+                    arcname = file_path.relative_to(extension_dir)
+                    if nested:
+                        arcname = Path("test-ext-v1.0.0") / arcname
+                    tf.add(file_path, arcname=str(arcname))
+
+    def test_install_from_tar_gz(self, extension_dir, project_dir, temp_dir):
+        """install_from_zip should accept a .tar.gz archive."""
+        archive = temp_dir / "test-ext-1.0.0.tar.gz"
+        self._make_tarball(archive, extension_dir)
+
+        manager = ExtensionManager(project_dir)
+        manifest = manager.install_from_zip(archive, "0.1.0")
+        assert manifest.id == "test-ext"
+        assert manager.registry.is_installed("test-ext")
+
+    def test_install_from_tgz(self, extension_dir, project_dir, temp_dir):
+        """install_from_zip should accept a .tgz archive."""
+        archive = temp_dir / "test-ext-1.0.0.tgz"
+        self._make_tarball(archive, extension_dir)
+
+        manager = ExtensionManager(project_dir)
+        manifest = manager.install_from_zip(archive, "0.1.0")
+        assert manifest.id == "test-ext"
+        assert manager.registry.is_installed("test-ext")
+
+    def test_install_from_tar_gz_nested(self, extension_dir, project_dir, temp_dir):
+        """install_from_zip should handle a single nested directory inside the tarball."""
+        archive = temp_dir / "test-ext-nested.tar.gz"
+        self._make_tarball(archive, extension_dir, nested=True)
+
+        manager = ExtensionManager(project_dir)
+        manifest = manager.install_from_zip(archive, "0.1.0")
+        assert manifest.id == "test-ext"
+        assert manager.registry.is_installed("test-ext")
+
+    def test_install_from_tar_gz_no_manifest(self, project_dir, temp_dir):
+        """install_from_zip raises ValidationError when tarball has no extension.yml."""
+        import tarfile
+        import io
+        archive = temp_dir / "bad.tar.gz"
+        with tarfile.open(archive, "w:gz") as tf:
+            data = b"no manifest here"
+            info = tarfile.TarInfo(name="readme.txt")
+            info.size = len(data)
+            tf.addfile(info, io.BytesIO(data))
+
+        manager = ExtensionManager(project_dir)
+        with pytest.raises(ValidationError, match="No extension.yml found"):
+            manager.install_from_zip(archive, "0.1.0")
+
+    def test_install_from_tar_gz_rejects_path_traversal(self, project_dir, temp_dir):
+        """install_from_zip must reject tarballs with path traversal entries."""
+        import tarfile
+        import io
+        archive = temp_dir / "evil.tar.gz"
+        with tarfile.open(archive, "w:gz") as tf:
+            info = tarfile.TarInfo(name="../../evil.txt")
+            data = b"evil"
+            info.size = len(data)
+            tf.addfile(info, io.BytesIO(data))
+
+        manager = ExtensionManager(project_dir)
+        with pytest.raises(ValidationError, match="Unsafe path"):
+            manager.install_from_zip(archive, "0.1.0")
+
+    def test_install_from_tar_gz_rejects_symlinks(self, project_dir, temp_dir):
+        """install_from_zip must reject tarballs containing symlinks."""
+        import tarfile
+        archive = temp_dir / "symlink.tar.gz"
+        with tarfile.open(archive, "w:gz") as tf:
+            info = tarfile.TarInfo(name="link")
+            info.type = tarfile.SYMTYPE
+            info.linkname = "/etc/passwd"
+            tf.addfile(info)
+
+        manager = ExtensionManager(project_dir)
+        with pytest.raises(ValidationError, match="Symlinks"):
+            manager.install_from_zip(archive, "0.1.0")
+
+
 # ===== CommandRegistrar Tests =====
 
 class TestCommandRegistrar:
@@ -2627,6 +2759,7 @@ class TestExtensionCatalog:
 
         mock_response = MagicMock()
         mock_response.read.return_value = zip_bytes
+        mock_response.geturl.return_value = "https://github.com/org/repo/releases/download/v1/test-ext.zip"
         mock_response.__enter__ = lambda s: s
         mock_response.__exit__ = MagicMock(return_value=False)
 
@@ -3529,6 +3662,7 @@ class TestDownloadExtensionBundled:
 
         mock_response = MagicMock()
         mock_response.read.return_value = b"fake zip data"
+        mock_response.geturl.return_value = "https://example.com/git-2.0.0.zip"
         mock_response.__enter__ = lambda s: s
         mock_response.__exit__ = MagicMock(return_value=False)
 

tests/test_presets.py

@@ -649,6 +649,90 @@ class TestPresetManager:
         with pytest.raises(PresetValidationError, match="No preset.yml found"):
             manager.install_from_zip(zip_path, "0.1.5")
 
+    def _make_tarball(self, dest, pack_dir, nested=False):
+        import tarfile
+        with tarfile.open(dest, "w:gz") as tf:
+            for file_path in pack_dir.rglob("*"):
+                if file_path.is_file():
+                    arcname = file_path.relative_to(pack_dir)
+                    if nested:
+                        arcname = Path("test-pack-v1.0.0") / arcname
+                    tf.add(file_path, arcname=str(arcname))
+
+    def test_install_from_tar_gz(self, project_dir, pack_dir, temp_dir):
+        """Test installing a preset from a .tar.gz archive."""
+        archive = temp_dir / "test-pack-1.0.tar.gz"
+        self._make_tarball(archive, pack_dir)
+
+        manager = PresetManager(project_dir)
+        manifest = manager.install_from_zip(archive, "0.1.5")
+        assert manifest.id == "test-pack"
+        assert manager.registry.is_installed("test-pack")
+
+    def test_install_from_tgz(self, project_dir, pack_dir, temp_dir):
+        """Test installing a preset from a .tgz archive."""
+        archive = temp_dir / "test-pack-1.0.tgz"
+        self._make_tarball(archive, pack_dir)
+
+        manager = PresetManager(project_dir)
+        manifest = manager.install_from_zip(archive, "0.1.5")
+        assert manifest.id == "test-pack"
+        assert manager.registry.is_installed("test-pack")
+
+    def test_install_from_tar_gz_nested(self, project_dir, pack_dir, temp_dir):
+        """Test installing a preset from a .tar.gz archive with a single nested directory."""
+        archive = temp_dir / "test-pack-nested.tar.gz"
+        self._make_tarball(archive, pack_dir, nested=True)
+
+        manager = PresetManager(project_dir)
+        manifest = manager.install_from_zip(archive, "0.1.5")
+        assert manifest.id == "test-pack"
+        assert manager.registry.is_installed("test-pack")
+
+    def test_install_from_tar_gz_no_manifest(self, project_dir, temp_dir):
+        """Test installing a preset from a .tar.gz without preset.yml raises error."""
+        import tarfile
+        import io
+        archive = temp_dir / "bad.tar.gz"
+        with tarfile.open(archive, "w:gz") as tf:
+            data = b"no manifest here"
+            info = tarfile.TarInfo(name="readme.txt")
+            info.size = len(data)
+            tf.addfile(info, io.BytesIO(data))
+
+        manager = PresetManager(project_dir)
+        with pytest.raises(PresetValidationError, match="No preset.yml found"):
+            manager.install_from_zip(archive, "0.1.5")
+
+    def test_install_from_tar_gz_rejects_path_traversal(self, project_dir, temp_dir):
+        """install_from_zip must reject tarballs with path traversal entries."""
+        import tarfile
+        import io
+        archive = temp_dir / "evil.tar.gz"
+        with tarfile.open(archive, "w:gz") as tf:
+            info = tarfile.TarInfo(name="../../evil.txt")
+            data = b"evil"
+            info.size = len(data)
+            tf.addfile(info, io.BytesIO(data))
+
+        manager = PresetManager(project_dir)
+        with pytest.raises(PresetValidationError, match="Unsafe path"):
+            manager.install_from_zip(archive, "0.1.5")
+
+    def test_install_from_tar_gz_rejects_symlinks(self, project_dir, temp_dir):
+        """install_from_zip must reject tarballs containing symlinks."""
+        import tarfile
+        archive = temp_dir / "symlink.tar.gz"
+        with tarfile.open(archive, "w:gz") as tf:
+            info = tarfile.TarInfo(name="link")
+            info.type = tarfile.SYMTYPE
+            info.linkname = "/etc/passwd"
+            tf.addfile(info)
+
+        manager = PresetManager(project_dir)
+        with pytest.raises(PresetValidationError, match="Symlinks"):
+            manager.install_from_zip(archive, "0.1.5")
+
     def test_remove(self, project_dir, pack_dir):
         """Test removing a preset."""
         manager = PresetManager(project_dir)
@@ -1529,6 +1613,7 @@ class TestPresetCatalog:
 
         mock_response = MagicMock()
         mock_response.read.return_value = zip_bytes
+        mock_response.geturl.return_value = "https://github.com/org/repo/releases/download/v1/test-pack.zip"
         mock_response.__enter__ = lambda s: s
         mock_response.__exit__ = MagicMock(return_value=False)
 

tests/test_workflows.py

@@ -1843,3 +1843,230 @@ steps:
         assert state.status == RunStatus.COMPLETED
         assert "do-plan" in state.step_results
         assert "do-specify" not in state.step_results
+
+
+# ===== workflow add archive CLI tests =====
+
+MINIMAL_WORKFLOW_YAML = """\
+schema_version: "1.0"
+workflow:
+  id: "arc-workflow"
+  name: "Archive Workflow"
+  version: "1.0.0"
+  description: "Installed from archive"
+steps:
+  - id: step-one
+    type: shell
+    run: "echo hello"
+"""
+
+
+class TestWorkflowAddArchive:
+    """CLI-level tests for `workflow add` with local archive files."""
+
+    @pytest.fixture
+    def project_dir(self, tmp_path):
+        """Create a minimal spec-kit project."""
+        specify = tmp_path / ".specify"
+        specify.mkdir()
+        (specify / "workflows").mkdir()
+        return tmp_path
+
+    def _runner_and_app(self):
+        from typer.testing import CliRunner
+        from specify_cli import app
+        return CliRunner(), app
+
+    # -- Local ZIP archive --------------------------------------------------
+
+    def test_workflow_add_local_zip_flat(self, project_dir):
+        """workflow add installs from a local ZIP with workflow.yml at root."""
+        import zipfile
+        from unittest.mock import patch
+        runner, app = self._runner_and_app()
+
+        archive = project_dir / "workflow.zip"
+        with zipfile.ZipFile(archive, "w") as zf:
+            zf.writestr("workflow.yml", MINIMAL_WORKFLOW_YAML)
+
+        with patch.object(Path, "cwd", return_value=project_dir):
+            result = runner.invoke(app, ["workflow", "add", str(archive)], catch_exceptions=False)
+
+        assert result.exit_code == 0, result.output
+        assert "arc-workflow" in result.output
+        installed = project_dir / ".specify" / "workflows" / "arc-workflow" / "workflow.yml"
+        assert installed.exists()
+
+    def test_workflow_add_local_zip_nested(self, project_dir):
+        """workflow add installs from a local ZIP with workflow.yml in a subdirectory."""
+        import zipfile
+        from unittest.mock import patch
+        runner, app = self._runner_and_app()
+
+        archive = project_dir / "workflow.zip"
+        with zipfile.ZipFile(archive, "w") as zf:
+            zf.writestr("repo-1.0/workflow.yml", MINIMAL_WORKFLOW_YAML)
+
+        with patch.object(Path, "cwd", return_value=project_dir):
+            result = runner.invoke(app, ["workflow", "add", str(archive)], catch_exceptions=False)
+
+        assert result.exit_code == 0, result.output
+        assert "arc-workflow" in result.output
+
+    def test_workflow_add_local_zip_missing_workflow_yml(self, project_dir):
+        """workflow add exits with an error when the ZIP has no workflow.yml."""
+        import zipfile
+        from unittest.mock import patch
+        runner, app = self._runner_and_app()
+
+        archive = project_dir / "empty.zip"
+        with zipfile.ZipFile(archive, "w") as zf:
+            zf.writestr("README.md", "nothing here")
+
+        with patch.object(Path, "cwd", return_value=project_dir):
+            result = runner.invoke(app, ["workflow", "add", str(archive)], catch_exceptions=True)
+
+        assert result.exit_code != 0
+        assert "extract" in result.output.lower() or "workflow" in result.output.lower()
+
+    # -- Local tar.gz archive -----------------------------------------------
+
+    def test_workflow_add_local_tar_gz_flat(self, project_dir):
+        """workflow add installs from a local .tar.gz with workflow.yml at root."""
+        import tarfile, io
+        from unittest.mock import patch
+        runner, app = self._runner_and_app()
+
+        archive = project_dir / "workflow.tar.gz"
+        with tarfile.open(archive, "w:gz") as tf:
+            data = MINIMAL_WORKFLOW_YAML.encode()
+            info = tarfile.TarInfo(name="workflow.yml")
+            info.size = len(data)
+            tf.addfile(info, io.BytesIO(data))
+
+        with patch.object(Path, "cwd", return_value=project_dir):
+            result = runner.invoke(app, ["workflow", "add", str(archive)], catch_exceptions=False)
+
+        assert result.exit_code == 0, result.output
+        assert "arc-workflow" in result.output
+        installed = project_dir / ".specify" / "workflows" / "arc-workflow" / "workflow.yml"
+        assert installed.exists()
+
+    def test_workflow_add_local_tar_gz_nested(self, project_dir):
+        """workflow add installs from a local .tar.gz with workflow.yml in a subdirectory."""
+        import tarfile, io
+        from unittest.mock import patch
+        runner, app = self._runner_and_app()
+
+        archive = project_dir / "workflow.tar.gz"
+        with tarfile.open(archive, "w:gz") as tf:
+            data = MINIMAL_WORKFLOW_YAML.encode()
+            info = tarfile.TarInfo(name="repo-1.0/workflow.yml")
+            info.size = len(data)
+            tf.addfile(info, io.BytesIO(data))
+
+        with patch.object(Path, "cwd", return_value=project_dir):
+            result = runner.invoke(app, ["workflow", "add", str(archive)], catch_exceptions=False)
+
+        assert result.exit_code == 0, result.output
+        assert "arc-workflow" in result.output
+
+    def test_workflow_add_local_tgz_flat(self, project_dir):
+        """workflow add recognises the .tgz extension as a gzipped tarball."""
+        import tarfile, io
+        from unittest.mock import patch
+        runner, app = self._runner_and_app()
+
+        archive = project_dir / "workflow.tgz"
+        with tarfile.open(archive, "w:gz") as tf:
+            data = MINIMAL_WORKFLOW_YAML.encode()
+            info = tarfile.TarInfo(name="workflow.yml")
+            info.size = len(data)
+            tf.addfile(info, io.BytesIO(data))
+
+        with patch.object(Path, "cwd", return_value=project_dir):
+            result = runner.invoke(app, ["workflow", "add", str(archive)], catch_exceptions=False)
+
+        assert result.exit_code == 0, result.output
+        assert "arc-workflow" in result.output
+
+    def test_workflow_add_local_tar_gz_missing_workflow_yml(self, project_dir):
+        """workflow add exits with an error when the .tar.gz has no workflow.yml."""
+        import tarfile, io
+        from unittest.mock import patch
+        runner, app = self._runner_and_app()
+
+        archive = project_dir / "empty.tar.gz"
+        with tarfile.open(archive, "w:gz") as tf:
+            data = b"nothing"
+            info = tarfile.TarInfo(name="README.md")
+            info.size = len(data)
+            tf.addfile(info, io.BytesIO(data))
+
+        with patch.object(Path, "cwd", return_value=project_dir):
+            result = runner.invoke(app, ["workflow", "add", str(archive)], catch_exceptions=True)
+
+        assert result.exit_code != 0
+        assert "extract" in result.output.lower() or "workflow" in result.output.lower()
+
+    # -- URL archive download -----------------------------------------------
+
+    def test_workflow_add_url_tar_gz(self, project_dir):
+        """workflow add downloads a .tar.gz from a URL and installs the workflow."""
+        import tarfile, io
+        from unittest.mock import patch, MagicMock
+        runner, app = self._runner_and_app()
+
+        # Build an in-memory tar.gz archive containing workflow.yml.
+        buf = io.BytesIO()
+        with tarfile.open(fileobj=buf, mode="w:gz") as tf:
+            data = MINIMAL_WORKFLOW_YAML.encode()
+            info = tarfile.TarInfo(name="workflow.yml")
+            info.size = len(data)
+            tf.addfile(info, io.BytesIO(data))
+        raw_bytes = buf.getvalue()
+
+        mock_resp = MagicMock()
+        mock_resp.geturl.return_value = "https://example.com/workflow.tar.gz"
+        mock_resp.headers.get.return_value = "application/gzip"
+        mock_resp.read.return_value = raw_bytes
+        mock_resp.__enter__ = lambda s: s
+        mock_resp.__exit__ = MagicMock(return_value=False)
+
+        with patch("urllib.request.urlopen", return_value=mock_resp), \
+             patch.object(Path, "cwd", return_value=project_dir):
+            result = runner.invoke(
+                app, ["workflow", "add", "https://example.com/workflow.tar.gz"],
+                catch_exceptions=False,
+            )
+
+        assert result.exit_code == 0, result.output
+        assert "arc-workflow" in result.output
+
+    def test_workflow_add_url_zip(self, project_dir):
+        """workflow add downloads a .zip from a URL and installs the workflow."""
+        import zipfile, io
+        from unittest.mock import patch, MagicMock
+        runner, app = self._runner_and_app()
+
+        buf = io.BytesIO()
+        with zipfile.ZipFile(buf, "w") as zf:
+            zf.writestr("workflow.yml", MINIMAL_WORKFLOW_YAML)
+        raw_bytes = buf.getvalue()
+
+        mock_resp = MagicMock()
+        mock_resp.geturl.return_value = "https://example.com/workflow.zip"
+        mock_resp.headers.get.return_value = "application/zip"
+        mock_resp.read.return_value = raw_bytes
+        mock_resp.__enter__ = lambda s: s
+        mock_resp.__exit__ = MagicMock(return_value=False)
+
+        with patch("urllib.request.urlopen", return_value=mock_resp), \
+             patch.object(Path, "cwd", return_value=project_dir):
+            result = runner.invoke(
+                app, ["workflow", "add", "https://example.com/workflow.zip"],
+                catch_exceptions=False,
+            )
+
+        assert result.exit_code == 0, result.output
+        assert "arc-workflow" in result.output