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/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")