Restore load_skill + surface skill catalog in system prompt

Main's load_skill tool was deleted during the SDK migration along
with the prompt-mutation pattern it relied on. Re-add the capability
without the mutation: load_skill(skills=[...]) now returns the skill
markdown bodies as a tool result, so the content lands in conversation
history as in-context reference rather than as patched-in system
prompt content. Same source of truth (load_skills + skill files),
same validation (validate_requested_skills) as create_agent.

Tool result format is plain markdown (## Skill: <name> headers joined
with ---), not the <specialized_knowledge> XML wrapping used at
agent-build time. The XML framing was deliberately reserved for
prompt-level privileged context; tool-loaded skills are honestly
labelled as just-fetched reference material.

Close the discovery loop by surfacing the full skill catalog in the
system prompt. Without it the model could only guess skill names —
discovering them via validation errors on misses. Now every agent
sees a categorised <available_skills> block right after the
<specialized_knowledge> block with a short hint pointing at
create_agent / load_skill.

Skills module: factored _iter_user_skill_files() so get_all_skill_names
(set, for validation) and get_available_skills (dict by category,
for the prompt) share one source of truth on what counts as
user-selectable. Internal categories (scan_modes, coordination) stay
excluded from both.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

strix/agents/factory.py

@@ -40,6 +40,7 @@ from strix.tools.agents_graph.tools import (
     wait_for_message,
 )
 from strix.tools.finish.tool import finish_scan
+from strix.tools.load_skill.tool import load_skill
 from strix.tools.notes.tools import (
     create_note,
     delete_note,
@@ -342,6 +343,8 @@ def _finish_tool_use_behavior(
 _BASE_TOOLS: tuple[Tool, ...] = (
     # Thinking + planning
     think,
+    # On-demand skill reference (returns the skill markdown inline)
+    load_skill,
     # Per-agent todos
     create_todo,
     list_todos,

strix/agents/prompt.py

@@ -12,7 +12,7 @@ from typing import Any
 
 from jinja2 import Environment, FileSystemLoader, select_autoescape
 
-from strix.skills import load_skills
+from strix.skills import get_available_skills, load_skills
 from strix.utils.resource_paths import get_strix_resource_path
 
 
@@ -114,6 +114,7 @@ def render_system_prompt(
 
         rendered = env.get_template("system_prompt.jinja").render(
             loaded_skill_names=list(skill_content.keys()),
+            available_skills=get_available_skills(),
             interactive=interactive,
             system_prompt_context=system_prompt_context or {},
             **skill_content,

strix/agents/prompts/system_prompt.jinja

@@ -437,3 +437,13 @@ Default user: pentester (sudo available)
 {% endfor %}
 </specialized_knowledge>
 {% endif %}
+
+{% if available_skills %}
+<available_skills>
+On-demand specialist skills. Spawn a specialist via `create_agent(skills=[...])`, or pull guidance inline for yourself via `load_skill(skills=[...])`. Anything wrapped in `<specialized_knowledge>` above is already loaded for you.
+
+{% for category, names in available_skills | dictsort -%}
+- {{ category }}: {{ names | join(', ') }}
+{% endfor -%}
+</available_skills>
+{% endif %}

strix/skills/__init__.py

@@ -1,5 +1,6 @@
 import logging
 import re
+from collections.abc import Iterator
 
 from strix.utils.resource_paths import get_strix_resource_path
 
@@ -14,25 +15,31 @@ _FRONTMATTER_PATTERN = re.compile(r"^---\s*\n.*?\n---\s*\n", re.DOTALL)
 _INTERNAL_SKILL_CATEGORIES: frozenset[str] = frozenset({"scan_modes", "coordination"})
 
 
-def get_all_skill_names() -> set[str]:
-    """Return every user-selectable skill name (bare, no category prefix).
-
-    Used by :func:`validate_requested_skills` so ``create_agent`` can
-    reject typos / hallucinated names with a useful list, and by callers
-    that need to enumerate the catalog.
-    """
+def _iter_user_skill_files() -> Iterator[tuple[str, str]]:
+    """Yield ``(category_name, skill_name)`` for every user-selectable skill."""
     skills_dir = get_strix_resource_path("skills")
     if not skills_dir.exists():
-        return set()
-    names: set[str] = set()
-    for category_dir in skills_dir.iterdir():
+        return
+    for category_dir in sorted(skills_dir.iterdir()):
         if not category_dir.is_dir() or category_dir.name.startswith("__"):
             continue
         if category_dir.name in _INTERNAL_SKILL_CATEGORIES:
             continue
-        for file_path in category_dir.glob("*.md"):
-            names.add(file_path.stem)
-    return names
+        for file_path in sorted(category_dir.glob("*.md")):
+            yield category_dir.name, file_path.stem
+
+
+def get_all_skill_names() -> set[str]:
+    """Return every user-selectable skill name (bare, no category prefix)."""
+    return {name for _, name in _iter_user_skill_files()}
+
+
+def get_available_skills() -> dict[str, list[str]]:
+    """Return user-selectable skills grouped by category, alphabetised."""
+    grouped: dict[str, list[str]] = {}
+    for category, name in _iter_user_skill_files():
+        grouped.setdefault(category, []).append(name)
+    return grouped
 
 
 def validate_requested_skills(skill_list: list[str], max_skills: int = 5) -> str | None:

strix/tools/load_skill/tool.py

@@ -0,0 +1,36 @@
+"""``load_skill`` — fetch skill reference material into the conversation."""
+
+from __future__ import annotations
+
+from agents import RunContextWrapper, function_tool
+
+from strix.skills import load_skills, validate_requested_skills
+
+
+@function_tool(timeout=10)
+async def load_skill(ctx: RunContextWrapper, skills: list[str]) -> str:
+    """Return the markdown body of one or more skills as reference material.
+
+    Use this when you need exact syntax / workflow / payload guidance
+    right before acting on a technology that wasn't preloaded for your
+    agent. The skill content lands inline as a tool result — no
+    permanent prompt change, just in-conversation reference.
+
+    For permanent skill assignment, pass ``skills=[…]`` to
+    ``create_agent`` when spawning a specialist child instead.
+
+    Args:
+        skills: List of skill names (e.g. ``["xss", "sql_injection"]``).
+            Max 5. Names match the bare files under
+            ``strix/skills/<category>/<name>.md``.
+    """
+    del ctx
+    requested = list(skills or [])
+    err = validate_requested_skills(requested)
+    if err:
+        return f"load_skill: {err}"
+    contents = load_skills(requested)
+    if not contents:
+        return "load_skill: no content loaded for requested skills."
+    sections = [f"## Skill: {name}\n\n{body}" for name, body in contents.items()]
+    return "\n\n---\n\n".join(sections)