refactor(model-routing): centralize explicit foreground fallback policy

core/database.py

@@ -1404,8 +1404,25 @@ def _migrate_assign_legacy_owner():
             with open(prefs_path, "r", encoding="utf-8") as f:
                 prefs = _json.load(f)
             if "_users" not in prefs and prefs:
-                # Flat format → nest under admin user
-                new_prefs = {"_users": {admin_user: prefs}}
+                # Flat format → nest ordinary preferences under the admin
+                # user. Foreground fallback is an explicit per-owner opt-in,
+                # so auth-disabled consent must remain inert at the flat root
+                # rather than becoming consent for the first named owner.
+                foreground_keys = {
+                    "foreground_fallback_enabled",
+                    "foreground_model_fallbacks",
+                }
+                named_prefs = {
+                    key: value
+                    for key, value in prefs.items()
+                    if key not in foreground_keys
+                }
+                new_prefs = {
+                    key: prefs[key]
+                    for key in foreground_keys
+                    if key in prefs
+                }
+                new_prefs["_users"] = {admin_user: named_prefs}
                 with open(prefs_path, "w", encoding="utf-8") as f:
                     _json.dump(new_prefs, f, indent=2)
                 logger.info(f"Migrated user_prefs.json to per-user format under '{admin_user}'")

mcp_servers/email_server.py

@@ -1540,7 +1540,6 @@ async def _ai_draft_reply_to_email(uid, folder="INBOX", reply_all=False, account
         from src.endpoint_resolver import (
             resolve_endpoint,
             resolve_utility_fallback_candidates,
-            resolve_chat_fallback_candidates,
         )
         from src.llm_core import llm_call_async_with_fallback
     except Exception as exc:
@@ -1582,13 +1581,6 @@ def _add(url, model, headers):
         utility_fallbacks = resolve_utility_fallback_candidates() or []
     for cand in utility_fallbacks:
         _add(*cand)
-    try:
-        chat_fallbacks = resolve_chat_fallback_candidates(owner=None) or []
-    except TypeError:
-        chat_fallbacks = resolve_chat_fallback_candidates() or []
-    for cand in chat_fallbacks:
-        _add(*cand)
-
     if not candidates:
         return {"error": "No LLM endpoint configured for AI reply"}
 

routes/auth_routes.py

@@ -22,6 +22,8 @@
     load_features as _load_features,
     save_features as _save_features,
     DEFAULT_SETTINGS,
+    RETIRED_SETTING_KEYS,
+    without_retired_settings,
 )
 from src.integrations import (
     load_integrations,
@@ -637,7 +639,7 @@ async def get_settings(request: Request):
         a scrubbed copy with secret keys blanked. The frontend uses this
         for keybinds + TTS prefs, so it stays callable without admin."""
         user = _get_current_user(request)
-        settings = _load_settings()
+        settings = without_retired_settings(_load_settings())
         if user and auth_manager.is_admin(user):
             return settings
         return scrub_settings(settings)
@@ -657,6 +659,8 @@ async def set_settings(request: Request):
             "agent_max_tool_calls": (0, 1000),  # 0 = unlimited
         }
         for key in DEFAULT_SETTINGS:
+            if key in RETIRED_SETTING_KEYS:
+                continue
             if key not in body:
                 continue
             val = body[key]
@@ -669,7 +673,7 @@ async def set_settings(request: Request):
                 val = max(lo, min(val, hi))
             current[key] = val
         _save_settings(current)
-        return current
+        return without_retired_settings(current)
 
     # ---- Integrations CRUD ----
 

routes/chat_helpers.py

@@ -14,7 +14,7 @@
 from src.llm_core import normalize_model_id
 from src.endpoint_resolver import normalize_base
 from src.context_compactor import maybe_compact, trim_for_context
-from src.model_context import estimate_tokens
+from src.model_context import estimate_tokens, get_context_length
 from src.auth_helpers import effective_user
 from src.prompt_security import untrusted_context_message
 from src.attachment_refs import attachment_ref
@@ -114,10 +114,38 @@ class ChatContext:
     # Uploads attached to this user turn, resolved and owner-checked for the
     # agent's private context. This is not emitted to the browser.
     uploaded_files: list = field(default_factory=list)
+    # Route-neutral prompt before any model-window compaction/trimming. This is
+    # retained only when explicit foreground fallbacks are enabled so each
+    # concrete candidate can apply its own context budget independently.
+    route_messages: list = field(default_factory=list)
 
 
 # ── Helpers ────────────────────────────────────────────────────────────── #
 
+def _allowed_models_from_privileges(privs: dict) -> Optional[frozenset[str]]:
+    if privs.get("block_all_models"):
+        return frozenset()
+    allowed_raw = privs.get("allowed_models")
+    allowed = allowed_raw if isinstance(allowed_raw, list) else []
+    restricted = bool(privs.get("allowed_models_restricted")) or bool(allowed)
+    return frozenset(model for model in allowed if isinstance(model, str)) if restricted else None
+
+
+def _allowed_models_for_request(request) -> Optional[frozenset[str]]:
+    """Return the caller's model allowlist, or ``None`` when unrestricted."""
+
+    try:
+        user = effective_user(request)
+    except Exception:
+        user = None
+    if not user:
+        return None
+    auth_manager = getattr(getattr(request.app, "state", None), "auth_manager", None)
+    if not auth_manager:
+        return None
+    privs = auth_manager.get_privileges(user) or {}
+    return _allowed_models_from_privileges(privs)
+
 def _enforce_chat_privileges(request, sess) -> None:
     """Apply the per-user privilege gates (allowed_models + max_messages_per_day)
     that both /api/chat and /api/chat_stream must enforce BEFORE any LLM work.
@@ -147,10 +175,8 @@ def _enforce_chat_privileges(request, sess) -> None:
     if privs.get("block_all_models"):
         raise HTTPException(403, f"Your account is not allowed to use model '{sess.model}'.")
 
-    allowed_raw = privs.get("allowed_models")
-    allowed = allowed_raw if isinstance(allowed_raw, list) else []
-    restricted = bool(privs.get("allowed_models_restricted")) or bool(allowed)
-    if restricted and sess.model and sess.model not in allowed:
+    allowed_models = _allowed_models_from_privileges(privs)
+    if allowed_models is not None and sess.model and sess.model not in allowed_models:
         raise HTTPException(403, f"Your account is not allowed to use model '{sess.model}'.")
 
     cap = int(privs.get("max_messages_per_day") or 0)
@@ -249,96 +275,6 @@ async def auto_name_session(session_manager, sess):
         logger.error(f"Auto-name failed for {sess.id}: {e}\n{traceback.format_exc()}")
 
 
-def try_fallback_endpoint(sess, session_id: str) -> dict | None:
-    """Find an alternative working endpoint when the current one fails.
-
-    Returns {"model": ..., "endpoint_url": ..., "endpoint_name": ...} or None.
-    """
-    import requests as _req
-    from src.endpoint_resolver import (
-        build_chat_url,
-        build_headers,
-        build_models_url,
-        normalize_base,
-        resolve_endpoint_runtime,
-    )
-    from src.chatgpt_subscription import is_chatgpt_subscription_base
-
-    current_url = sess.endpoint_url or ""
-    owner = getattr(sess, "owner", None)
-    db = SessionLocal()
-    try:
-        q = db.query(ModelEndpoint).filter(
-            ModelEndpoint.is_enabled == True
-        )
-        if owner:
-            from src.auth_helpers import owner_filter
-            q = owner_filter(q, ModelEndpoint, owner)
-        endpoints = q.all()
-    finally:
-        db.close()
-
-    for ep in endpoints:
-        base = normalize_base(ep.base_url)
-        # Skip current endpoint
-        if current_url and base in current_url:
-            continue
-        try:
-            base, api_key = resolve_endpoint_runtime(ep, owner=owner)
-        except Exception:
-            continue
-        ping_url = build_models_url(base)
-        headers = build_headers(api_key, base)
-        try:
-            if ping_url:
-                r = _req.get(ping_url, headers=headers, timeout=5)
-                r.raise_for_status()
-                data = r.json()
-                models = [m.get("id") for m in (data.get("data") or []) if m.get("id")]
-                if not models:
-                    models = [
-                        m.get("name") or m.get("model")
-                        for m in (data.get("models") or [])
-                        if m.get("name") or m.get("model")
-                    ]
-            else:
-                models = json.loads(ep.cached_models or "[]")
-            if not models:
-                continue
-            # Found a working endpoint — update session
-            new_model = models[0]
-            chat_url = build_chat_url(base)
-            new_headers = build_headers(api_key, base)
-            persisted_headers = {} if is_chatgpt_subscription_base(base) else new_headers
-
-            sess.model = new_model
-            sess.endpoint_url = chat_url
-            sess.headers = new_headers
-
-            # Persist
-            _db = SessionLocal()
-            try:
-                _db.query(DBSession).filter(DBSession.id == session_id).update({
-                    "model": new_model,
-                    "endpoint_url": chat_url,
-                    "headers": persisted_headers,
-                })
-                _db.commit()
-            finally:
-                _db.close()
-
-            logger.info(f"Fallback: switched session {session_id} from {current_url} to {ep.name} ({new_model})")
-            return {
-                "model": new_model,
-                "endpoint_url": chat_url,
-                "endpoint_name": ep.name,
-            }
-        except Exception:
-            continue
-
-    return None
-
-
 def extract_preset(chat_handler, preset_id) -> PresetInfo:
     """Extract preset parameters via chat_handler."""
     temperature, max_tokens, system_prompt, char_name = (
@@ -648,6 +584,7 @@ async def build_chat_context(
     use_enhanced_message: bool = False,
     agent_mode: bool = False,
     allow_tool_preprocessing: bool = True,
+    defer_context_shaping: bool = False,
 ) -> ChatContext:
     """Build the full context (preface + messages) for an LLM call.
 
@@ -783,13 +720,22 @@ async def build_chat_context(
         except Exception:
             logger.debug("Failed to add current date/time context", exc_info=True)
 
-    # Auto-compact
-    messages, context_length, was_compacted = await maybe_compact(
-        sess, sess.endpoint_url, sess.model, messages, sess.headers, owner=user,
-    )
+    route_messages = list(messages)
+    # Explicit fallback routing must shape from the same route-neutral prompt
+    # for every candidate. Running selected-model compaction here would mutate
+    # session history before we know which route can answer and would make a
+    # later larger-context candidate unable to recover discarded history.
+    if defer_context_shaping:
+        context_length = get_context_length(sess.endpoint_url, sess.model)
+        was_compacted = False
+    else:
+        messages, context_length, was_compacted = await maybe_compact(
+            sess, sess.endpoint_url, sess.model, messages, sess.headers, owner=user,
+        )
     _before_trim_messages = len(messages)
     _before_trim_tokens = estimate_tokens(messages)
-    messages = trim_for_context(messages, context_length)
+    if not defer_context_shaping:
+        messages = trim_for_context(messages, context_length)
     _after_trim_messages = len(messages)
     _after_trim_tokens = estimate_tokens(messages)
     _context_trimmed = _after_trim_messages < _before_trim_messages or _after_trim_tokens < _before_trim_tokens
@@ -813,6 +759,7 @@ async def build_chat_context(
         context_tokens_after_trim=_after_trim_tokens,
         auto_opened_docs=auto_opened_docs,
         uploaded_files=uploaded_files,
+        route_messages=route_messages,
     )