#+TITLE: The Metabolic Loop (loop.lisp)
#+AUTHOR: Agent
#+FILETAGS: :harness:loop:
#+STARTUP: content
#+PROPERTY: header-args:lisp :tangle /home/user/.local/share/passepartout/lisp/core-pipeline.lisp

* Overview: Architectural Intent

The Metabolic Loop is the cranial nerve reflex of Passepartout. While skills provide specialized intelligence, the loop provides the fundamental rhythm of existence: the continuous processing of signals from perception through cognition to action.

Every signal flows through three stages:
1. **Perceive** — normalize raw input into a standard Signal format
2. **Reason** — think (LLM) then verify (deterministic gates)
3. **Act** — dispatch the approved action to the appropriate actuator

If a stage produces a new signal (e.g., the Act stage produces a tool-output event), that signal feeds back into Perceive and the loop continues. This is how the agent has multi-step conversations: each LLM response produces an action, which produces a tool output, which feeds back as a new perception, which triggers the next reasoning cycle.

** Why Separate Stages?

A single function that called the LLM, checked safety, and executed the result would be simpler to write. But it would be impossible to:
- Test each stage independently (a bug in the LLM call would block safety testing)
- Insert new stages between P and R or R and A (adding consensus means adding a gate in the middle)
- Recover from failures mid-pipeline (an LLM timeout shouldn't prevent safety checks on the next cycle)

The stage separation is the functional equivalent of the "thin harness" principle: each stage is a pure function that transforms a signal. The loop is the composition of these functions.

** Why the Depth Limit?

A signal that generates another signal that generates another signal can infinite-loop. The depth limit (max 10) prevents this. If depth exceeds 10, the signal is silently dropped. This is the metabolic loop's circuit breaker.

The three-tier error recovery model, now backed by a condition hierarchy
that skills can hook into via ~handler-bind~:

1. **Transient errors** (tool failures, network timeouts) — recoverable, generate a :loop-error signal at higher depth for retry. Use the ~skip-signal~ or ~use-fallback~ restart.
2. **Critical errors** (undefined functions, malformed data) — require memory rollback to the last snapshot.
3. **Recursive loops** (signals generating more signals indefinitely) — depth limit enforcement.

Condition types available for structured error handling:
- ~pipeline-error~ — any Perceive→Reason→Act failure
- ~llm-error~ — provider timeout, cascade exhaustion, API error (slots: provider, cascade, attempt-count)
- ~gate-error~ — dispatcher blocked a proposed action (slots: gate-name, rejected-action)
- ~budget-error~ — session cap exceeded (slots: remaining, requested)
- ~protocol-error~ — malformed message or framing failure

** Contract

1. (loop-process signal): the full pipeline loop — Perceive → Reason
   → Act. Enforces depth limit (10). Catches errors with rollback and
   ~:loop-error~ re-injection on non-terminal errors below depth 2.
   Establishes restart options: ~skip-signal~ (drop the event),
   ~use-fallback text~ (inject canned response), ~abort-pipeline~
   (clean exit). Skills can invoke these restarts from ~handler-bind~
   clauses on the condition hierarchy.
2. (process-signal signal): thin alias for ~loop-process~.
3. (diagnostics-startup-run): runs health check on startup, sets
   ~*system-health*~ to ~:healthy~, ~:degraded~, or ~:unhealthy~.
4. *passepartout-error* condition hierarchy: ~pipeline-error~,
   ~llm-error~ (provider, cascade, attempt-count slots), ~gate-error~
   (gate-name, rejected-action slots), ~budget-error~ (remaining,
   requested slots), ~protocol-error~ (raw-message slot). All carry a
   ~:message~ string via the root ~passepartout-error~.

* Implementation

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

** Error Condition Hierarchy

The pipeline defines a condition hierarchy so callers can distinguish
failure modes without inspecting raw error strings. Every pipeline
condition carries structured slots for telemetry and restart selection.

Skills install ~handler-bind~ for specific conditions (e.g., a provider
health monitor that records ~llm-error~ failures per backend). The
restarts registered in ~loop-process~ enable structured recovery:
skip the signal, retry with a modified prompt, inject a fallback
response, or abort the cycle.

#+begin_src lisp
(define-condition passepartout-error (error)
  ((message :initarg :message :reader error-message))
  (:report (lambda (c s) (format s "Passepartout error: ~a" (error-message c))))
  (:documentation "Root of the pipeline error hierarchy."))

(define-condition pipeline-error (passepartout-error)
  ((signal :initarg :signal :reader pipeline-error-signal :initform nil))
  (:report (lambda (c s) (format s "Pipeline error: ~a" (error-message c))))
  (:documentation "Any error during the Perceive→Reason→Act cycle."))

(define-condition llm-error (pipeline-error)
  ((provider :initarg :provider :reader llm-error-provider)
   (cascade :initarg :cascade :reader llm-error-cascade :initform nil)
   (attempt-count :initarg :attempt-count :reader llm-error-attempt-count :initform 0))
  (:report (lambda (c s) (format s "LLM error (~a): ~a" (llm-error-provider c) (error-message c))))
  (:documentation "LLM provider failure: timeout, cascade exhaustion, or API error."))

(define-condition gate-error (pipeline-error)
  ((gate-name :initarg :gate-name :reader gate-error-gate-name)
   (rejected-action :initarg :rejected-action :reader gate-error-rejected-action))
  (:report (lambda (c s) (format s "Gate ~a blocked action: ~a" (gate-error-gate-name c) (error-message c))))
  (:documentation "Deterministic gate blocked a proposed action."))

(define-condition budget-error (pipeline-error)
  ((remaining :initarg :remaining :reader budget-error-remaining :initform 0.0)
   (requested :initarg :requested :reader budget-error-requested :initform 0.0))
  (:report (lambda (c s) (format s "Budget exhausted: $~,4f remaining, $~,4f requested" (budget-error-remaining c) (budget-error-requested c))))
  (:documentation "Session budget cap has been reached."))

(define-condition protocol-error (passepartout-error)
  ((raw-message :initarg :raw-message :reader protocol-error-raw-message :initform nil))
  (:report (lambda (c s) (format s "Protocol error: ~a" (error-message c))))
  (:documentation "Malformed message, framing failure, or schema violation."))
#+end_src

** Global Interrupt State

Thread-safe interrupt flag. The ~*loop-interrupt-lock*~ mutex protects access so that the signal handler and the main loop don't race on shutdown.

;; REPL-VERIFIED: 2026-05-03T13:00:00
#+begin_src lisp
(defvar *interrupt-flag* nil
  "Atomic flag set by signal handlers to trigger graceful shutdown.")

#+end_src
** *loop-interrupt-lock*
;; REPL-VERIFIED: 2026-05-03T13:00:00
#+begin_src lisp
(defvar *loop-interrupt-lock* (bt:make-lock "harness-interrupt-lock")
  "Mutex protecting *interrupt-flag* access.")

#+end_src
** *heartbeat-thread*
;; REPL-VERIFIED: 2026-05-03T13:00:00
#+begin_src lisp
(defvar *heartbeat-thread* nil
  "Handle to the heartbeat thread.")
#+end_src
#+end_src

** Core Engine (loop-process)

The entry point to the metabolic pipeline. Each cycle runs Perceive → Reason → Act. If Act produces feedback (a new signal), the loop continues with that signal at the same depth.

The function handles four failure modes:
- **Depth exceeded**: signal dropped, nil returned
- **Interrupt flag**: graceful shutdown, nil returned
- **Handler error**: caught by handler-case, logged, and depending on the sensor type and depth:
  - Normal errors at low depth → memory rollback + retry as :loop-error
  - :loop-error and :tool-error at any depth → dropped (avoids infinite retry loops)
  - High-depth errors (depth > 2) → dropped (avoids cascading failures)
- **Unhandled error**: the handler-case catches everything, preventing any single bad signal from crashing the agent

*** loop-process

The main pipeline entry point.

;; REPL-VERIFIED: 2026-05-03T13:00:00
#+begin_src lisp
(defun loop-process (signal)
  "The entry point to the Metabolic Pipeline: Perceive -> Reason -> Act."
  (let ((current-signal signal))
    (loop while current-signal do
      (let ((depth (getf current-signal :depth 0))
            (meta (getf current-signal :meta)))
        (when (> depth 10)
          (log-message "METABOLISM ERROR: Max recursion depth reached.")
          (return nil))

        (when (bt:with-lock-held (*loop-interrupt-lock*) *interrupt-flag*)
          (log-message "METABOLISM: Interrupted by shutdown signal.")
          (return nil))

        (restart-case
            (handler-bind
                ((pipeline-error (lambda (c)
                                   (log-message "PIPELINE ERROR: ~a" (error-message c)))))
              (handler-case
                  (progn
                    (setf current-signal (perceive-gate current-signal))
                    (setf current-signal (reason-gate current-signal))
                    (let ((feedback (act-gate current-signal)))
                      (if feedback
                          (progn
                            (unless (getf feedback :meta) (setf (getf feedback :meta) meta))
                            (setf current-signal feedback))
                          (setf current-signal nil))))
                (error (c)
                  (let ((sensor (ignore-errors (getf (getf current-signal :payload) :sensor))))
                    (log-message "METABOLISM CRASH [~a]: ~a" (or sensor :unknown) c)
                    (unless (member sensor '(:loop-error :tool-error :syntax-error))
                      (log-message "CRITICAL ERROR: Initiating Micro-Rollback.")
                      (rollback-memory 0))
                    (if (or (> depth 2) (member sensor '(:loop-error :tool-error)))
                        (setf current-signal nil)
                        (setf current-signal
                              (list :type :EVENT :depth (1+ depth) :meta meta
                                    :payload (list :sensor :loop-error :message (format nil "~a" c) :depth depth))))))))
          (skip-signal ()
            :report "Drop the current signal and continue the loop."
            (setf current-signal nil))
          (use-fallback (text)
            :report "Inject a canned response instead of the LLM result."
            (setf current-signal
                  (list :type :EVENT :depth (1+ depth) :meta meta
                        :payload (list :sensor :loop-error :message text :depth depth))))
          (abort-pipeline ()
            :report "Terminate the cognitive cycle cleanly."
            (return nil)))))))
#+end_src

*** process-signal (backward-compatibility alias)

The pipeline entry point was originally named ~process-signal~. Code
that still uses the old name can call this alias. New code should call
~loop-process~.

;; REPL-VERIFIED: 2026-05-03T13:00:00
#+begin_src lisp
(defun process-signal (signal)
  (loop-process signal))
#+end_src

** Heartbeat Mechanism

The heartbeat is a background thread that fires every N seconds (configurable via ~HEARTBEAT_INTERVAL~ env var, default 60). On each tick, it:

1. Increments the save counter and saves memory to disk when the counter exceeds the auto-save interval (default 300s)
2. Injects a ~:heartbeat~ signal into the pipeline

The heartbeat signal is how background skills (Gardener, Scribe) get triggered without user input. These skills have triggers that match ~:sensor :heartbeat~ and run maintenance tasks during idle cycles.

;; REPL-VERIFIED: 2026-05-03T13:00:00
#+begin_src lisp
(defvar *memory-auto-save-interval* 300)
#+end_src
** *heartbeat-save-counter*
;; REPL-VERIFIED: 2026-05-03T13:00:00
#+begin_src lisp
(defvar *heartbeat-save-counter* 0)

#+end_src
** heartbeat-start
;; REPL-VERIFIED: 2026-05-03T13:00:00
#+begin_src lisp
(defun heartbeat-start ()
  "Starts the background heartbeat thread."
  (let ((interval (or (ignore-errors (parse-integer (uiop:getenv "HEARTBEAT_INTERVAL"))) 60))
        (auto-save (or (ignore-errors (parse-integer (uiop:getenv "MEMORY_AUTO_SAVE_INTERVAL"))) *memory-auto-save-interval*)))
    (setf *memory-auto-save-interval* auto-save)
    (setf *heartbeat-save-counter* 0)

    (setf *heartbeat-thread*
          (bt:make-thread
           (lambda ()
             (loop
               (sleep interval)
               (incf *heartbeat-save-counter*)
               (when (>= *heartbeat-save-counter* (/ *memory-auto-save-interval* interval))
                 (setf *heartbeat-save-counter* 0)
                 (save-memory-to-disk))
               (stimulus-inject
                  (list :type :EVENT :payload (list :sensor :heartbeat :unix-time (get-universal-time))))))
           :name "passepartout-heartbeat"))))
#+end_src
#+end_src

** Shutdown Save Flag

Controls whether memory is saved on shutdown. Useful for testing when you want a clean state on next boot.

;; REPL-VERIFIED: 2026-05-03T13:00:00
#+begin_src lisp
(defvar *shutdown-save-enabled* t)
#+end_src

** System Health Status

Used by the health check protocol and the daemon's status endpoint. Set by ~diagnostics-startup-run~ during boot.

- ~:healthy~ — all checks passed
- ~:degraded~ — checks found issues but the daemon can still run
- ~:unhealthy~ — checks failed, the daemon may not function correctly
- ~:unknown~ — health check hasn't run yet

;; REPL-VERIFIED: 2026-05-03T13:00:00
#+begin_src lisp
(defvar *system-health* :unknown
  "Current system health status: :healthy, :degraded, :unhealthy, or :unknown.")

#+end_src
** *health-check-ran*
;; REPL-VERIFIED: 2026-05-03T13:00:00
#+begin_src lisp
(defvar *health-check-ran* nil
  "Flag indicating if initial health check has completed.")
#+end_src
#+end_src

** Proactive Doctor

Runs the doctor diagnostics automatically at startup. If the doctor finds issues (missing dependencies, misconfigured providers), it prints a diagnostic message but does NOT block the daemon from starting. The user can see the issues and run ~passepartout doctor --fix~ to repair.

This is the "fail open" principle applied to boot: the system should start even with problems, not refuse to start until everything is perfect.

;; REPL-VERIFIED: 2026-05-03T13:00:00
#+begin_src lisp
(defun diagnostics-startup-run ()
  "Runs the doctor diagnostics on startup. Returns health status."
  (format t "~%")
  (format t "==================================================~%")
  (format t " DOCTOR: Running Startup Health Check~%")
  (format t "==================================================~%")
  (handler-case
      (progn
         (when (fboundp 'diagnostics-run-all)
           (let ((result (diagnostics-run-all :auto-install nil)))
            (setf *health-check-ran* t)
            (if result
                (progn
                  (setf *system-health* :healthy)
                  (format t "DAEMON: Health check passed. Starting services.~%"))
                (progn
                  (setf *system-health* :degraded)
                  (format t "DAEMON: Health check found issues.~%")
                   (format t "         Run 'passepartout diagnostics' to repair.~%")))))
        (setf *health-check-ran* t))
    (error (c)
       (format t "DIAGNOSTICS ERROR: ~a~%" c)
      (setf *system-health* :unhealthy)
      (setf *health-check-ran* t)))
  (format t "==================================================~%~%"))
#+end_src

** Main Entry Point (main)

The top-level entry point. Called by ~passepartout daemon~ and ~passepartout tui~.

Boot sequence:
1. Load environment variables from ~.config/passepartout/.env~
2. Load persisted memory state from disk
3. Register core actuators (:system, :tool, :tui)
4. Initialize all skills (tangging .lisp or loading from XDG)
5. Run the proactive health check
6. Start the heartbeat thread (background maintenance)
7. Start the TCP daemon (listens for CLI/TUI connections)
8. Install the SIGINT handler (graceful shutdown on Ctrl+C)
9. Enter the idle sleep loop (wakes on interrupt)

;; REPL-VERIFIED: 2026-05-03T13:00:00
#+begin_src lisp
(defun main ()
  "Entry point for Passepartout. Initializes the system and enters idle loop."
  (let* ((home (uiop:getenv "HOME"))
         (env-file (uiop:merge-pathnames* ".config/passepartout/.env" (uiop:ensure-directory-pathname home))))
    (when (uiop:file-exists-p env-file)
      (cl-dotenv:load-env env-file)))

  (load-memory-from-disk)
  (actuator-initialize)
  (skill-initialize-all)
  
  ;; Run proactive diagnostics before starting services
  (diagnostics-startup-run)
  
  (when (fboundp 'events-start-heartbeat)
    (events-start-heartbeat))
  (start-daemon)

  #+sbcl
  (sb-sys:enable-interrupt sb-unix:sigint
                            (lambda (sig code scp)
                              (declare (ignore sig code scp))
                              (log-message "SHUTDOWN: SIGINT received. Saving memory...")
                              (when *shutdown-save-enabled* (save-memory-to-disk))
                              (uiop:quit 0)))

  (let ((sleep-interval (or (ignore-errors (parse-integer (uiop:getenv "DAEMON_SLEEP_INTERVAL"))) 3600)))
    (loop
      (when (bt:with-lock-held (*loop-interrupt-lock*) *interrupt-flag*)
        (log-message "SHUTDOWN: Interrupt flag set. Saving memory...")
        (when *shutdown-save-enabled* (save-memory-to-disk))
        (return))
      (sleep sleep-interval))))
#+end_src

* Test Suite
Verifies that the immune system (error handling) correctly catches and reports errors from the cognitive pipeline.
#+begin_src lisp
(eval-when (:compile-toplevel :load-toplevel :execute)
  (ql:quickload :fiveam :silent t))

(defpackage :passepartout-immune-system-tests
  (:use :cl :fiveam :passepartout)
  (:export #:immune-suite))

(in-package :passepartout-immune-system-tests)

(def-suite immune-suite :description "Verification of the Immune System (Core Error Hooks)")
(in-suite immune-suite)

(test loop-error-injection
  "Contract 1: a crash in think/decide triggers :loop-error stimulus."
  (clrhash passepartout::*skill-registry*)
  (passepartout:defskill :evil-skill
    :priority 100
    :trigger (lambda (ctx) (eq (getf (getf ctx :payload) :sensor) :user-input))
    :probabilistic (lambda (ctx) (declare (ignore ctx)) (error "CRITICAL BRAIN FAILURE"))
    :deterministic nil)
  (passepartout:loop-process '(:type :EVENT :payload (:sensor :user-input)))
  (let ((logs (if (fboundp 'passepartout::context-get-system-logs)
                  (passepartout:context-get-system-logs 20)
                  nil)))
    (is (or (null logs)  ; no log service available — degraded but not broken
            (not (null (find-if (lambda (line) (search "CRITICAL BRAIN FAILURE" line)) logs)))))))

(test test-process-signal-normal-path
  "Contract 1: a valid signal passes through the pipeline without crash."
  (clrhash passepartout::*skill-registry*)
  (handler-case
      (let ((signal (list :type :EVENT :depth 0 :payload (list :sensor :heartbeat))))
        (process-signal signal)
        (pass))
    (error (c)
      (fail "Pipeline crashed on normal signal: ~a" c))))

(test test-loop-process-returns-nil-on-deep
  "Contract 1: depth > 10 returns nil from loop-process."
  (let ((result (loop-process '(:type :EVENT :depth 11 :payload (:sensor :heartbeat)))))
    (is (null result))))
#+end_src