#+TITLE: SKILL: Model Router (org-skill-model-router.org)
#+AUTHOR: Agent
#+FILETAGS: :system:model:routing:
#+PROPERTY: header-args:lisp :tangle ../lisp/system-model-router.lisp

* Overview: Quadrant-Based Model Routing

The Model Router implements the four-quadrant cognitive architecture for
LLM model selection. Each signal is routed through a pipeline of three
filters — privacy, quadrant, and complexity — before a model is chosen.

The routing pipeline for every probabilistic signal:

  all backends → privacy filter → quadrant/classifier → per-slot cascade → model

- **Privacy filter** strips cloud backends when content carries ~@personal~ tags.
- **Quadrant** determines if the signal is foreground or background.
- **Complexity classifier** assigns foreground signals to one of three slots:
  ~:code~, ~:plan~, or ~:chat~.
- **Per-slot cascade** selects a backend and model for the slot, with fallback
  ordering defined in each cascade list.

The model selector function is registered into the core ~*model-selector*~ hook
at load time. The core iterates providers, calling the selector for each one.

* Implementation

** Package Context

#+begin_src lisp
(in-package :passepartout)
#+end_src

** Configuration: Per-Slot Cascades

Four env-configurable cascade variables, one per slot. Each cascade is a list
of ~(provider-keyword . "model-name")~ pairs. The first match for the current
backend is used.

Example:
  MODEL_CASCADE_CODE='((:ollama . "deepseek-coder:6.7b") (:openrouter . "claude-sonnet"))'

*** *model-cascade-code*

The cascade for ~:code~ tasks (code generation, refactoring, bug fixing).
Format: ~((:ollama . "model-name") ...)~. Configured via ~MODEL_CASCADE_CODE~.

;; REPL-VERIFIED: 2026-05-03T14:00:00
#+begin_src lisp
(defvar *model-cascade-code* nil
  "Cascade for :code tasks: ((:ollama . \"model\") ...)")
#+end_src

*** *model-cascade-plan*

Cascade for planning and architecture tasks. Configured via ~MODEL_CASCADE_PLAN~.

;; REPL-VERIFIED: 2026-05-03T14:00:00
#+begin_src lisp
(defvar *model-cascade-plan* nil
  "Cascade for :plan tasks.")
#+end_src

*** *model-cascade-chat*

Cascade for general conversation and simple Q&A. Configured via ~MODEL_CASCADE_CHAT~.

;; REPL-VERIFIED: 2026-05-03T14:00:00
#+begin_src lisp
(defvar *model-cascade-chat* nil
  "Cascade for :chat tasks.")
#+end_src

*** *model-cascade-background*

Cascade for background tasks (heartbeat scraping, delegation processing).
Configured via ~MODEL_CASCADE_BACKGROUND~.

;; REPL-VERIFIED: 2026-05-03T14:00:00
#+begin_src lisp
(defvar *model-cascade-background* nil
  "Cascade for background tasks (heartbeat, delegation).")
#+end_src

*** *local-backends*

List of backend keywords considered local for privacy routing. Content tagged
with ~@personal~ will only be sent to these backends.

;; REPL-VERIFIED: 2026-05-03T14:00:00
#+begin_src lisp
(defvar *local-backends* '(:ollama :llama-cpp)
  "Backend keywords considered local (privacy-safe).")
#+end_src

** Complexity Classifier

Keyword-based heuristic that assigns signal text to a complexity slot.
Pluggable — set ~*complexity-classifier*~ to override.

;; REPL-VERIFIED: 2026-05-03T14:00:00
#+begin_src lisp
(defun model-classify-complexity (text)
  "Classify TEXT into :code, :plan, or :chat."
  (let ((lower (string-downcase text)))
    (cond
      ((or (search "defun" lower) (search "defmacro" lower)
           (search "write" lower) (search "refactor" lower)
           (search "fix " lower) (search "implement" lower)
           (search "code" lower)
           (search "#+begin_src" lower))
       :code)
      ((or (search "plan" lower) (search "roadmap" lower)
           (search "strategy" lower) (search "design" lower)
           (search "architecture" lower))
       :plan)
      (t :chat))))
#+end_src

** Cascade Lookup

The core iterates each backend in ~*provider-cascade*~ and calls the model
selector for each one. This function matches the current backend against the
per-slot cascade list to find the appropriate model. Returns the first
~:code~ ~(provider . model)~ entry whose provider matches, or ~nil~ if
the backend has no entry in that slot's cascade (the core will skip to
the next provider).

;; REPL-VERIFIED: 2026-05-03T14:00:00
#+begin_src lisp
(defun model-cascade-find (cascade backend)
  "Find first (PROVIDER . MODEL) in CASCADE matching BACKEND."
  (assoc backend cascade
         :test (lambda (a b) (string-equal (string a) (string b)))))
#+end_src

** Model Selector

The main routing function. Registered into ~*model-selector*~ at init time.
Called per-backend by ~backend-cascade-call~. Returns a model name string,
or ~:skip~ if the backend should not be tried (e.g., privacy filter).

Filter order: privacy → quadrant → complexity → cascade.

;; REPL-VERIFIED: 2026-05-03T14:00:00
#+begin_src lisp
(defun model-select (backend context)
  "Select model for BACKEND given CONTEXT signal.
Returns model name or :skip."
  (let* ((payload (getf context :payload))
         (text (or (getf payload :text) ""))
         (sensor (getf payload :sensor))
         (has-personal (and (boundp '*dispatcher-privacy-tags*)
                            (some (lambda (tag) (search tag text))
                                  (symbol-value '*dispatcher-privacy-tags*))))
         (is-local (member backend *local-backends*)))
    ;; Privacy: skip cloud backends for personal content
    (when (and has-personal (not is-local))
      (log-message "MODEL-ROUTER: Skipping ~a (personal content)" backend)
      (return-from model-select :skip))
    ;; Quadrant: background tasks use background cascade
    (if (member sensor '(:heartbeat :delegation :tool-output :loop-error))
        (let ((entry (car (or *model-cascade-background*
                              '((:ollama . "phi-2"))))))
          (cdr entry))
        ;; Foreground: classify complexity, use slot cascade
        (let* ((slot (model-classify-complexity text))
               (cascade (case slot
                          (:code *model-cascade-code*)
                          (:plan *model-cascade-plan*)
                          (t *model-cascade-chat*)))
               (entry (model-cascade-find
                       (or cascade '((:ollama . "qwen2.5:14b"))) backend)))
          (if entry (cdr entry) nil)))))
#+end_src

** Initialization

Reads cascade configuration from environment variables and registers
~model-select~ into the core ~*model-selector*~ hook.

;; REPL-VERIFIED: 2026-05-03T14:00:00
#+begin_src lisp
(defun model-router-init ()
  "Read env vars and wire model-select into *model-selector*."
  (flet ((parse-cascade (str)
           (when (and str (> (length str) 0))
             (let ((*read-eval* nil))
               (read-from-string str)))))
    (setf *model-cascade-code* (parse-cascade (uiop:getenv "MODEL_CASCADE_CODE"))
          *model-cascade-plan* (parse-cascade (uiop:getenv "MODEL_CASCADE_PLAN"))
          *model-cascade-chat* (parse-cascade (uiop:getenv "MODEL_CASCADE_CHAT"))
          *model-cascade-background* (parse-cascade (uiop:getenv "MODEL_CASCADE_BACKGROUND"))
          *local-backends* (let ((env (uiop:getenv "LOCAL_BACKENDS")))
                             (if env
                                 (mapcar (lambda (s) (intern (string-upcase (string-trim '(#\Space #\" #\') s)) :keyword))
                                         (uiop:split-string env :separator '(#\,)))
                                 '(:ollama :llama-cpp)))))
    (setf *model-selector* #'model-select)
    (log-message "MODEL-ROUTER: Initialized, selector=~a" *model-selector*))
#+end_src

** Skill Registration

The model router is an observer skill — it has no trigger and no
deterministic gate. All work happens at load time via ~model-router-init~,
which reads env vars and registers into the core ~*model-selector*~ hook.
The ~defskill~ call exists only to register metadata (priority, name) for
telemetry and lifecycle management.

#+begin_src lisp
(defskill :passepartout-model-router
  :priority 250
  :trigger (lambda (ctx) (declare (ignore ctx)) nil))
#+end_src

** Auto-Init

#+begin_src lisp
(model-router-init)
#+end_src