agentic-sx Phase 4: durable — agent sessions as durable flow workflows (TDD)

Deterministic replay IS the durability mechanism: every transition re-runs a
self-contained flow program (defflow source + flow/start + replay of all
recorded resume values), so the only durable state is {:flow :input :resumes}
in persist kv — restart-safe by construction (fresh space handles over the
same backend resume mid-flight runs). fork-an-agent-run = copy the record;
the two replays diverge independently. Effects are data (suspend tags +
typed request envelopes surface as plain SX); transitions ride the Phase-3
trace buffer so session history travels with the next commit. Guest numeric
results compared with = per house convention. 43/43 (196/196 total).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/agentic/conformance.sh

@@ -13,7 +13,7 @@ if [ ! -x "$SX_SERVER" ]; then
   exit 1
 fi
 
-SUITES=(schema branch trace)
+SUITES=(schema branch trace durable)
 
 OUT_JSON="lib/agentic/scoreboard.json"
 OUT_MD="lib/agentic/scoreboard.md"

lib/agentic/durable.sx

@@ -0,0 +1,235 @@
+; lib/agentic/durable.sx — agentic-sx Phase 4: long agent sessions as
+; DURABLE flow workflows. Deterministic replay IS the durability mechanism:
+; every transition re-runs a self-contained flow program (the session's
+; defflow source + flow/start + a replay of every recorded resume value),
+; so the only durable state is a plain record {:flow :input :resumes ...}
+; in the persist kv store — restart-safe by construction, and forking an
+; agent run is literally copying the record (both replays then diverge).
+; Effects are data: a suspended session exposes its suspend tag / typed
+; (request kind payload) envelope to the host as plain SX values.
+; Transitions also land in the agent's Phase-3 trace buffer, so the session
+; history travels with the agent's next commit.
+; Convention for session flows: suspend tags are quoted symbols, decision
+; values are numbers/strings/lists of those (see agentic/scm-lit).
+; Requires: lib/agentic/trace.sx (and its deps), lib/flow/* (+ scheme stack).
+
+; ---- SX -> Scheme literal (numbers, strings, booleans, lists; nil = ()) ----
+(define
+  agentic/scm-lit
+  (fn
+    (v)
+    (cond
+      ((nil? v) "(list)")
+      ((= v true) "#t")
+      ((= v false) "#f")
+      ((number? v) (str v))
+      ((string? v) (str "\"" v "\""))
+      ((list? v) (str "(list " (join " " (map agentic/scm-lit v)) ")"))
+      (else "(list)"))))
+
+; ---- Scheme -> SX: unbox {:scm-string ...} recursively ----
+(define
+  agentic/scm-out
+  (fn
+    (v)
+    (cond
+      ((and (dict? v) (has-key? v :scm-string)) (get v :scm-string))
+      ((list? v) (map agentic/scm-out v))
+      (else v))))
+
+; ---- kv keys (namespaced under the repo prefix) ----
+(define
+  agentic/session-def-key
+  (fn
+    (sp name)
+    (str (get (agentic/space-repo sp) :prefix) "/session-def/" name)))
+
+(define
+  agentic/session-key
+  (fn
+    (sp agent)
+    (str (get (agentic/space-repo sp) :prefix) "/session/" agent)))
+
+; ---- durable session flow definitions ----
+(define
+  agentic/defsession!
+  (fn
+    (sp name scheme-src)
+    (begin
+      (persist/kv-put
+        (git/repo-db (agentic/space-repo sp))
+        (agentic/session-def-key sp name)
+        scheme-src)
+      name)))
+
+(define
+  agentic/session-def
+  (fn
+    (sp name)
+    (persist/kv-get
+      (git/repo-db (agentic/space-repo sp))
+      (agentic/session-def-key sp name))))
+
+(define
+  agentic/session-record
+  (fn
+    (sp agent)
+    (persist/kv-get
+      (git/repo-db (agentic/space-repo sp))
+      (agentic/session-key sp agent))))
+
+; ---- one self-contained replay program per transition ----
+; a fresh flow-run resets the flow store, so the started flow is always id 1
+(define
+  agentic/session-program
+  (fn
+    (defs name input resumes)
+    (str
+      defs
+      "\n"
+      "(define s0 (flow/start "
+      name
+      " "
+      (agentic/scm-lit input)
+      "))\n"
+      (join
+        "\n"
+        (map
+          (fn (v) (str "(flow/resume 1 " (agentic/scm-lit v) ")"))
+          resumes))
+      "\n(list (flow/status 1) (flow/pending) (flow/result 1))")))
+
+; replay the record, derive {:status :tag/:result}, persist record+state
+(define
+  agentic/session-transition!
+  (fn
+    (sp agent record)
+    (let
+      ((defs (agentic/session-def sp (get record :flow))))
+      (if
+        (nil? defs)
+        {:flow (get record :flow) :error "no-such-session-flow"}
+        (let
+          ((out (flow-run (agentic/session-program defs (get record :flow) (get record :input) (get record :resumes)))))
+          (let
+            ((status (agentic/scm-out (nth out 0)))
+              (pending (agentic/scm-out (nth out 1))))
+            (let
+              ((state (cond ((= status "done") {:status "done" :result (agentic/scm-out (nth out 2))}) ((= status "suspended") {:tag (nth (nth pending 0) 1) :status "suspended"}) (else {:status status}))))
+              (begin
+                (persist/kv-put
+                  (git/repo-db (agentic/space-repo sp))
+                  (agentic/session-key sp agent)
+                  (merge {:flow (get record :flow) :resumes (get record :resumes) :input (get record :input)} state))
+                state))))))))
+
+; ---- lifecycle ----
+(define
+  agentic/session-start!
+  (fn
+    (sp agent flow-name input)
+    (if
+      (nil? (agentic/head sp agent))
+      {:agent agent :error "no-such-agent"}
+      (let
+        ((state (agentic/session-transition! sp agent {:flow flow-name :resumes (list) :input input})))
+        (begin
+          (if
+            (has-key? state :error)
+            nil
+            (agentic/trace! sp agent "session" (str "start " flow-name)))
+          state)))))
+
+(define
+  agentic/session-resume!
+  (fn
+    (sp agent value)
+    (let
+      ((rec (agentic/session-record sp agent)))
+      (cond
+        ((nil? rec) {:agent agent :error "no-session"})
+        ((not (= (get rec :status) "suspended")) {:agent agent :error "not-suspended"})
+        (else
+          (let
+            ((state (agentic/session-transition! sp agent {:flow (get rec :flow) :resumes (append (get rec :resumes) (list value)) :input (get rec :input)})))
+            (begin
+              (if
+                (has-key? state :error)
+                nil
+                (agentic/trace!
+                  sp
+                  agent
+                  "session"
+                  (str "resume " (agentic/scm-lit value))))
+              state)))))))
+
+(define
+  agentic/session-status
+  (fn
+    (sp agent)
+    (let
+      ((r (agentic/session-record sp agent)))
+      (if (nil? r) "none" (get r :status)))))
+
+(define
+  agentic/session-pending
+  (fn
+    (sp agent)
+    (let
+      ((r (agentic/session-record sp agent)))
+      (if
+        (and (dict? r) (= (get r :status) "suspended"))
+        (get r :tag)
+        nil))))
+
+(define
+  agentic/session-result
+  (fn
+    (sp agent)
+    (let
+      ((r (agentic/session-record sp agent)))
+      (if (and (dict? r) (= (get r :status) "done")) (get r :result) nil))))
+
+; ---- fork-an-agent-run: copy the record, replay rebuilds the run ----
+; to-agent must already be spawned (branch fork) and session-free
+(define
+  agentic/session-fork!
+  (fn
+    (sp from-agent to-agent)
+    (let
+      ((rec (agentic/session-record sp from-agent)))
+      (cond
+        ((nil? rec) {:agent from-agent :error "no-session"})
+        ((nil? (agentic/head sp to-agent)) {:agent to-agent :error "no-such-agent"})
+        ((not (nil? (agentic/session-record sp to-agent))) {:agent to-agent :error "session-exists"})
+        (else
+          (let
+            ((state (agentic/session-transition! sp to-agent {:flow (get rec :flow) :resumes (get rec :resumes) :input (get rec :input)})))
+            (begin
+              (if
+                (has-key? state :error)
+                nil
+                (agentic/trace!
+                  sp
+                  to-agent
+                  "session"
+                  (str "fork " from-agent)))
+              state)))))))
+
+; ---- effect-as-data helpers over (request kind payload) envelopes ----
+(define
+  agentic/effect-request?
+  (fn
+    (tag)
+    (and
+      (list? tag)
+      (= (len tag) 3)
+      (= (nth tag 0) "flow-request"))))
+
+(define
+  agentic/effect-kind
+  (fn (tag) (if (agentic/effect-request? tag) (nth tag 1) nil)))
+
+(define
+  agentic/effect-payload
+  (fn (tag) (if (agentic/effect-request? tag) (nth tag 2) nil)))

lib/agentic/scoreboard.json

@@ -2,9 +2,10 @@
   "suites": {
     "schema": {"pass": 65, "fail": 0},
     "branch": {"pass": 53, "fail": 0},
-    "trace": {"pass": 35, "fail": 0}
+    "trace": {"pass": 35, "fail": 0},
+    "durable": {"pass": 43, "fail": 0}
   },
-  "total_pass": 153,
+  "total_pass": 196,
   "total_fail": 0,
-  "total": 153
+  "total": 196
 }

lib/agentic/scoreboard.md

@@ -7,4 +7,5 @@ _Generated by `lib/agentic/conformance.sh`_
 | schema | 65 | 0 | 65 |
 | branch | 53 | 0 | 53 |
 | trace | 35 | 0 | 35 |
-| **Total** | **153** | **0** | **153** |
+| durable | 43 | 0 | 43 |
+| **Total** | **196** | **0** | **196** |

lib/agentic/tests/durable.sx

@@ -0,0 +1,281 @@
+; Phase 4 — durable: agent sessions as durable flow workflows. Fixture story:
+; worker-1 runs the two-suspend "triage" flow to completion; worker-1b proves
+; restart-safety (fresh space handles over the same backend, resume across
+; the restart); worker-2's mid-flight run is FORKED to worker-2b and the two
+; replays diverge; worker-3 exercises typed (request kind payload) effects
+; and the trace-buffer composition with Phase 3.
+; NOTE: numbers computed inside the guest are compared with = (numeric
+; equality), not equal? — guest numerics box differently at the boundary.
+
+(define agd-db (persist/mem-backend))
+(define agd-sp (agentic/space agd-db "agentic-durable-test"))
+(define
+  agd-a
+  (agentic/spawn!
+    agd-sp
+    "worker-1"
+    (agentic/briefing "long task" "run a durable session" {})))
+(define
+  agd-b
+  (agentic/spawn-from!
+    agd-sp
+    "worker-1b"
+    (agentic/briefing "second worker" "restart survivor" {})
+    "worker-1"))
+
+(agentic/defsession!
+  agd-sp
+  "triage"
+  "(defflow triage (sequence (lambda (x) (+ x (suspend (quote ask-priority)))) (lambda (y) (* y (suspend (quote ask-factor))))))")
+
+; ---- literals across the guest boundary ----
+(agentic-test "scm-lit numbers" (agentic/scm-lit 42) "42")
+(agentic-test "scm-lit strings" (agentic/scm-lit "hi") "\"hi\"")
+(agentic-test
+  "scm-lit lists nest"
+  (agentic/scm-lit (list 1 "a"))
+  "(list 1 \"a\")")
+(agentic-test
+  "scm-out unboxes scheme strings"
+  (agentic/scm-out {:scm-string "x"})
+  "x")
+
+; ---- lifecycle: start / suspend / resume / done ----
+(agentic-test
+  "session flow source is durable"
+  (starts-with? (agentic/session-def agd-sp "triage") "(defflow")
+  true)
+(agentic-test
+  "no session before start"
+  (agentic/session-status agd-sp "worker-1")
+  "none")
+
+(define agd-s1 (agentic/session-start! agd-sp "worker-1" "triage" 10))
+
+(agentic-test
+  "start suspends at the first effect"
+  (get agd-s1 :status)
+  "suspended")
+(agentic-test "the suspend tag is data" (get agd-s1 :tag) "ask-priority")
+(agentic-test
+  "session-status tracks the suspension"
+  (agentic/session-status agd-sp "worker-1")
+  "suspended")
+(agentic-test
+  "session-pending exposes the tag"
+  (agentic/session-pending agd-sp "worker-1")
+  "ask-priority")
+(agentic-test
+  "start on unknown agent fails"
+  (get (agentic/session-start! agd-sp "ghost" "triage" 1) :error)
+  "no-such-agent")
+(agentic-test
+  "start with unknown flow fails"
+  (get
+    (agentic/session-start! agd-sp "worker-1b" "frobnicate" 1)
+    :error)
+  "no-such-session-flow")
+(agentic-test
+  "a failed start leaves no session"
+  (agentic/session-status agd-sp "worker-1b")
+  "none")
+
+(define agd-s2 (agentic/session-resume! agd-sp "worker-1" 5))
+
+(agentic-test
+  "resume replays to the next effect"
+  (get agd-s2 :tag)
+  "ask-factor")
+(agentic-test
+  "resume on session-less agent fails"
+  (get (agentic/session-resume! agd-sp "worker-1b" 1) :error)
+  "no-session")
+
+(define agd-s3 (agentic/session-resume! agd-sp "worker-1" 3))
+
+(agentic-test
+  "final resume completes the session"
+  (get agd-s3 :status)
+  "done")
+(agentic-test
+  "deterministic replay computes the result"
+  (= (get agd-s3 :result) 45)
+  true)
+(agentic-test
+  "session-status done"
+  (agentic/session-status agd-sp "worker-1")
+  "done")
+(agentic-test
+  "session-result reads back"
+  (= (agentic/session-result agd-sp "worker-1") 45)
+  true)
+(agentic-test
+  "resume after done fails"
+  (get (agentic/session-resume! agd-sp "worker-1" 9) :error)
+  "not-suspended")
+(agentic-test
+  "the record keeps the full replay history"
+  (=
+    (get (agentic/session-record agd-sp "worker-1") :resumes)
+    (list 5 3))
+  true)
+
+; ---- restart: a fresh space handle over the same backend ----
+(define agd-sp2 (agentic/space agd-db "agentic-durable-test"))
+
+(agentic-test
+  "restart sees the finished session"
+  (agentic/session-status agd-sp2 "worker-1")
+  "done")
+(agentic-test
+  "restart sees the result"
+  (= (agentic/session-result agd-sp2 "worker-1") 45)
+  true)
+
+(define
+  agd-s4
+  (agentic/session-start! agd-sp "worker-1b" "triage" 100))
+(define agd-sp3 (agentic/space agd-db "agentic-durable-test"))
+
+(agentic-test
+  "restart mid-flight stays suspended"
+  (agentic/session-status agd-sp3 "worker-1b")
+  "suspended")
+(agentic-test
+  "resume across the restart replays deterministically"
+  (get (agentic/session-resume! agd-sp3 "worker-1b" 2) :tag)
+  "ask-factor")
+(agentic-test
+  "the resumed run completes across the restart"
+  (=
+    (get (agentic/session-resume! agd-sp3 "worker-1b" 7) :result)
+    714)
+  true)
+
+; ---- fork-an-agent-run: copy the record, replays diverge ----
+(define
+  agd-w2
+  (agentic/spawn!
+    agd-sp
+    "worker-2"
+    (agentic/briefing "explore" "mainline run" {})))
+(define
+  agd-w2b
+  (agentic/spawn-from!
+    agd-sp
+    "worker-2b"
+    (agentic/briefing "explore alt" "forked run" {})
+    "worker-2"))
+(define agd-f0 (agentic/session-start! agd-sp "worker-2" "triage" 10))
+(define agd-f1 (agentic/session-resume! agd-sp "worker-2" 5))
+(define agd-fork (agentic/session-fork! agd-sp "worker-2" "worker-2b"))
+
+(agentic-test
+  "fork replays to the same suspended state"
+  (get agd-fork :tag)
+  "ask-factor")
+(agentic-test
+  "forked session is live"
+  (agentic/session-status agd-sp "worker-2b")
+  "suspended")
+(agentic-test
+  "forked history is copied"
+  (=
+    (get (agentic/session-record agd-sp "worker-2b") :resumes)
+    (list 5))
+  true)
+(agentic-test
+  "mainline resumes its own way"
+  (=
+    (get (agentic/session-resume! agd-sp "worker-2" 3) :result)
+    45)
+  true)
+(agentic-test
+  "fork diverges independently"
+  (=
+    (get (agentic/session-resume! agd-sp "worker-2b" 100) :result)
+    1500)
+  true)
+(agentic-test
+  "the fork's divergence never touches the mainline"
+  (= (agentic/session-result agd-sp "worker-2") 45)
+  true)
+(agentic-test
+  "fork needs an existing session"
+  (get (agentic/session-fork! agd-sp "worker-1x" "worker-2b") :error)
+  "no-session")
+(agentic-test
+  "fork target must be spawned"
+  (get (agentic/session-fork! agd-sp "worker-2" "ghost") :error)
+  "no-such-agent")
+(agentic-test
+  "fork refuses to clobber a session"
+  (get (agentic/session-fork! agd-sp "worker-2" "worker-2b") :error)
+  "session-exists")
+
+; ---- typed effects: (request kind payload) envelopes as data ----
+(agentic/defsession!
+  agd-sp
+  "review-loop"
+  "(defflow review-loop (sequence (lambda (x) (await-human (list (quote approve?) x))) (branch (lambda (d) (eq? d 1)) (flow-const (quote shipped)) (flow-const (quote parked)))))")
+
+(define
+  agd-w3
+  (agentic/spawn!
+    agd-sp
+    "worker-3"
+    (agentic/briefing "ship it" "review then ship" {})))
+(define
+  agd-r1
+  (agentic/session-start! agd-sp "worker-3" "review-loop" 7))
+
+(agentic-test
+  "request effects are typed envelopes"
+  (agentic/effect-request? (get agd-r1 :tag))
+  true)
+(agentic-test "effect kind" (agentic/effect-kind (get agd-r1 :tag)) "human")
+(agentic-test
+  "effect payload"
+  (=
+    (agentic/effect-payload (get agd-r1 :tag))
+    (list "approve?" 7))
+  true)
+(agentic-test
+  "plain tags are not request envelopes"
+  (agentic/effect-request? "ask-priority")
+  false)
+(agentic-test
+  "the human decision resumes the session"
+  (get (agentic/session-resume! agd-sp "worker-3" 1) :result)
+  "shipped")
+
+; ---- composition with Phase 3: transitions ride the trace buffer ----
+(agentic-test
+  "session transitions land in the trace buffer"
+  (len
+    (filter
+      (fn (e) (= (get e :kind) "session"))
+      (agentic/trace-pending agd-sp "worker-3")))
+  2)
+
+(define
+  agd-c
+  (agentic/commit-with-trace!
+    agd-sp
+    "worker-3"
+    "decision"
+    (assoc {} "ship.md" "approved\n")
+    {:message "shipped"}))
+
+(agentic-test
+  "the session history travels with the commit"
+  (len (agentic/trace-entries (agentic/trace-for agd-sp (get agd-c :cid))))
+  2)
+(agentic-test
+  "the bound trace records the session start"
+  (get
+    (nth
+      (agentic/trace-entries (agentic/trace-for agd-sp (get agd-c :cid)))
+      0)
+    :text)
+  "start review-loop")