passepartout/org/core-loop.org

#+TITLE: The Metabolic Loop (loop.lisp)
#+AUTHOR: Agent
#+FILETAGS: :harness:loop:
#+STARTUP: content
#+PROPERTY: header-args:lisp :tangle ../lisp/core-loop.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:
1. **Transient errors** (tool failures, network timeouts) — recoverable, generate a :loop-error signal at higher depth for retry
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

* Implementation

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

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

(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))

        (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)))))))))))
#+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))
               (inject-stimulus
                 (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 'doctor-run-all)
          (let ((result (doctor-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 doctor --fix' to repair.~%")))))
        (setf *health-check-ran* t))
    (error (c)
      (format t "DOCTOR 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 doctor before starting services
  (diagnostics-startup-run)
  
  (heartbeat-start)
  (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 :tangle ../lisp/core-loop.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
  "Verify that a crash in think/decide triggers a :loop-error stimulus."
  (clrhash passepartout::*skills-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 (passepartout:context-get-system-logs 20)))
    (is (not (null (find-if (lambda (line) (search "CRITICAL BRAIN FAILURE" line)) logs))))))
#+end_src