Per-tree AI model policy (owner-only admin view)

The operator decides which model providers exist (env / registry — Anthropic,
OpenAI, x.AI, Ollama, several at once). The *tree owner* decides who uses which:

- Members' assistant -> one configured provider (or none)
- Recommender (association/connection finder) -> one configured provider (or none)
- Owner -> may use any configured provider

Backend: two nullable columns on `trees` (ai_member_provider,
ai_recommender_provider) + migration; `configured_llm_providers()` exposes the
registry as {name, model} with no secrets; owner-gated GET/PATCH
/trees/{id}/ai validate names against the configured set. Frontend: owner-only
"AI models" page with a dropdown per role, graceful 403 for non-owners, and a
sidebar link.

Per-model-within-a-provider selection is a follow-up; today each provider maps
to its single configured model.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Justin Paul <justin@jpaul.me>

backend/app/api/deps.py

@@ -101,6 +101,22 @@ def build_llm_providers() -> dict[str, LLMProvider]:
     return providers
 
 
+def configured_llm_providers() -> list[dict]:
+    """Configured LLM providers as {name, model} — for the AI admin view (no
+    secrets). Mirrors build_llm_providers() without constructing clients."""
+    s = get_settings()
+    out: list[dict] = []
+    if s.anthropic_api_key:
+        out.append({"name": "anthropic", "model": s.anthropic_model})
+    if s.openai_api_key:
+        out.append({"name": "openai", "model": s.openai_model})
+    if s.xai_api_key:
+        out.append({"name": "xai", "model": s.xai_model})
+    if s.ollama_enabled:
+        out.append({"name": "ollama", "model": s.ollama_model})
+    return out
+
+
 def get_llm_provider(name: str | None = None) -> LLMProvider:
     """The named LLM provider, or the configured default, or Null if unconfigured."""
     providers = build_llm_providers()

backend/app/api/v1/__init__.py

@@ -3,6 +3,7 @@
 from fastapi import APIRouter
 
 from app.api.v1 import (
+    ai,
     auth,
     citations,
     cleanup,
@@ -36,3 +37,4 @@ api_router.include_router(cleanup.router)
 api_router.include_router(public.router)
 api_router.include_router(members.router)
 api_router.include_router(proposals.router)
+api_router.include_router(ai.router)

backend/app/api/v1/ai.py

@@ -0,0 +1,34 @@
+"""Per-tree AI model policy — owner-only admin view."""
+
+import uuid
+
+from fastapi import APIRouter
+
+from app.api.deps import CurrentUser, SessionDep
+from app.schemas.ai_policy import TreeAiPolicyRead, TreeAiPolicyUpdate
+from app.services import ai_policy_service, tree_service
+
+router = APIRouter(prefix="/trees", tags=["ai"])
+
+
+@router.get("/{tree_id}/ai", response_model=TreeAiPolicyRead)
+async def get_ai_policy(
+    tree_id: uuid.UUID, session: SessionDep, current: CurrentUser
+) -> TreeAiPolicyRead:
+    tree = await tree_service.get_tree(session, viewer_id=current.id, tree_id=tree_id)
+    return TreeAiPolicyRead(**await ai_policy_service.get_policy(session, actor=current, tree=tree))
+
+
+@router.patch("/{tree_id}/ai", response_model=TreeAiPolicyRead)
+async def update_ai_policy(
+    tree_id: uuid.UUID, data: TreeAiPolicyUpdate, session: SessionDep, current: CurrentUser
+) -> TreeAiPolicyRead:
+    tree = await tree_service.get_tree(session, viewer_id=current.id, tree_id=tree_id)
+    policy = await ai_policy_service.update_policy(
+        session,
+        actor=current,
+        tree=tree,
+        member_provider=data.member_provider,
+        recommender_provider=data.recommender_provider,
+    )
+    return TreeAiPolicyRead(**policy)