diff --git a/lib/flow/conformance.sh b/lib/flow/conformance.sh
index 5d0e7b6b..787c9c9e 100755
--- a/lib/flow/conformance.sh
+++ b/lib/flow/conformance.sh
@@ -30,6 +30,7 @@ SUITES=(
   "combinators flow-cmb-tests-run!       lib/flow/tests/combinators.sx"
   "railway     flow-rail-tests-run!      lib/flow/tests/railway.sx"
   "integration flow-int-tests-run!       lib/flow/tests/integration.sx"
+  "hygiene     flow-hyg-tests-run!       lib/flow/tests/hygiene.sx"
 )
 
 TMPFILE=$(mktemp); trap "rm -f $TMPFILE" EXIT
@@ -56,7 +57,7 @@ emit_eval () { echo "(epoch $EPOCH)"; echo "(eval \"$1\")"; EPOCH=$((EPOCH+1));
   done
 } > "$TMPFILE"
 
-OUTPUT=$(timeout 300 "$SX_SERVER" < "$TMPFILE" 2>&1 || true)
+OUTPUT=$(timeout 540 "$SX_SERVER" < "$TMPFILE" 2>&1 || true)
 
 TOTAL_PASS=0
 TOTAL_FAIL=0
diff --git a/lib/flow/scoreboard.json b/lib/flow/scoreboard.json
index b8cff6b9..012c8bfb 100644
--- a/lib/flow/scoreboard.json
+++ b/lib/flow/scoreboard.json
@@ -1,6 +1,6 @@
 {
-  "total": 142,
-  "passed": 142,
+  "total": 151,
+  "passed": 151,
   "failed": 0,
   "suites": {
     "basic": { "passed": 18, "total": 18 },
@@ -11,7 +11,8 @@
     "api": { "passed": 12, "total": 12 },
     "combinators": { "passed": 17, "total": 17 },
     "railway": { "passed": 10, "total": 10 },
-    "integration": { "passed": 10, "total": 10 }
+    "integration": { "passed": 10, "total": 10 },
+    "hygiene": { "passed": 9, "total": 9 }
   },
   "phases": { "phase1": "done", "phase2": "done", "phase3": "done", "phase4": "done", "phase5": "done", "phase6": "done", "phase7": "done" }
 }
diff --git a/lib/flow/scoreboard.md b/lib/flow/scoreboard.md
index 0f539a36..41eaf45d 100644
--- a/lib/flow/scoreboard.md
+++ b/lib/flow/scoreboard.md
@@ -1,6 +1,6 @@
 # flow-on-sx Scoreboard
 
-**All tests pass: 142 / 142 across 9 suites. Phases 1-7 complete.**
+**All tests pass: 151 / 151 across 10 suites. Phases 1-7 complete.**
 
 `bash lib/flow/conformance.sh`
 
@@ -17,6 +17,7 @@
 | combinators | 17 | Phase 5: `tap`, `recover` (fail-value), `map-flow` fan-over-list, `flow-while`/`flow-until` bounded iteration |
 | railway | 10 | Phase 6: `attempt` — fail-value short-circuiting sequence + recover rejoin |
 | integration | 10 | Phase 7: end-to-end order + onboarding flows composing every phase (suspend, branch, federation, crash recovery, handoff, introspection) |
+| hygiene | 9 | Phase 5: `flow/gc` (prune terminal flows), `flow/forget` (drop one terminal record) |
 
 ## Architecture
 
diff --git a/lib/flow/store.sx b/lib/flow/store.sx
index b88e6c5b..abd75360 100644
--- a/lib/flow/store.sx
+++ b/lib/flow/store.sx
@@ -28,10 +28,15 @@
 ;;   (flow/result id)        — result if done, else (flow-error reason)
 ;;   (flow/list)             — list of (id status) for every flow
 ;;   (flow/pending)          — list of (id waiting-tag) for suspended flows
+;; Store hygiene (Phase 5):
+;;   (flow/gc)               — drop all terminal (done/cancelled) records, keeping
+;;                             suspended (live) flows; returns the count removed
+;;   (flow/forget id)        — drop one TERMINAL record (#t); refuses to forget a
+;;                             still-suspended flow or an unknown id (#f)
 
 (define
   flow-store-src
-  "(define flow-registry (list))\n   (define (flow-register! name proc) (set! flow-registry (cons (list name proc) flow-registry)))\n   (define (flow-lookup-in name reg)\n     (if (null? reg)\n         #f\n         (if (eq? (car (car reg)) name) (car (cdr (car reg))) (flow-lookup-in name (cdr reg)))))\n   (define (flow-lookup name) (flow-lookup-in name flow-registry))\n   (define (flow-name-of proc reg)\n     (if (null? reg)\n         #f\n         (if (eq? (car (cdr (car reg))) proc) (car (car reg)) (flow-name-of proc (cdr reg)))))\n\n   (define flow-store (list))\n   (define flow-next-id 0)\n   (define (flow-store-remove id store)\n     (if (null? store)\n         (list)\n         (if (= (car (car store)) id)\n             (flow-store-remove id (cdr store))\n             (cons (car store) (flow-store-remove id (cdr store))))))\n   (define (flow-store-put! id rec) (set! flow-store (cons (list id rec) (flow-store-remove id flow-store))))\n   (define (flow-store-find id store)\n     (if (null? store)\n         (list)\n         (if (= (car (car store)) id)\n             (car (cdr (car store)))\n             (flow-store-find id (cdr store)))))\n   (define (flow-store-get id) (flow-store-find id flow-store))\n\n   (define (flow-mk-rec name proc input log status payload)\n     (list name proc input log status payload))\n   (define (flow-rec-name r) (car r))\n   (define (flow-rec-proc r) (car (cdr r)))\n   (define (flow-rec-input r) (car (cdr (cdr r))))\n   (define (flow-rec-log r) (car (cdr (cdr (cdr r)))))\n   (define (flow-rec-status r) (car (cdr (cdr (cdr (cdr r))))))\n   (define (flow-rec-payload r) (car (cdr (cdr (cdr (cdr (cdr r)))))))\n   (define (flow-rec-resolve rec)\n     (let ((byname (flow-lookup (flow-rec-name rec))))\n       (if byname byname (flow-rec-proc rec))))\n\n   (define (flow-outcome id name proc input log outcome)\n     (if (eq? (car outcome) (quote flow-done))\n         (begin\n           (flow-store-put! id (flow-mk-rec name proc input log (quote done) (car (cdr outcome))))\n           (car (cdr outcome)))\n         (begin\n           (flow-store-put! id (flow-mk-rec name proc input log (quote suspended) (car (cdr outcome))))\n           (list (quote flow-suspended) id (car (cdr outcome))))))\n   (define (flow/start flow input)\n     (set! flow-next-id (+ flow-next-id 1))\n     (flow-outcome flow-next-id (flow-name-of flow flow-registry) flow input (list)\n       (flow-drive flow input (list))))\n   (define (flow/resume id value)\n     (let ((rec (flow-store-get id)))\n       (if (null? rec)\n           (list (quote flow-error) (quote no-such-flow))\n           (if (eq? (flow-rec-status rec) (quote suspended))\n               (let ((proc (flow-rec-resolve rec)))\n                 (let ((newlog (cons (list (flow-rec-payload rec) value) (flow-rec-log rec))))\n                   (flow-outcome id (flow-rec-name rec) proc (flow-rec-input rec) newlog\n                     (flow-drive proc (flow-rec-input rec) newlog))))\n               (list (quote flow-error) (quote not-suspended))))))\n   (define (flow/cancel id)\n     (let ((rec (flow-store-get id)))\n       (if (null? rec)\n           (list (quote flow-error) (quote no-such-flow))\n           (begin\n             (flow-store-put! id\n               (flow-mk-rec (flow-rec-name rec) (flow-rec-proc rec) (flow-rec-input rec)\n                 (flow-rec-log rec) (quote cancelled) #f))\n             (list (quote flow-cancelled) id)))))\n\n   (define (flow-export-entry entry)\n     (let ((rec (car (cdr entry))))\n       (list (car entry)\n         (flow-mk-rec (flow-rec-name rec) #f (flow-rec-input rec)\n           (flow-rec-log rec) (flow-rec-status rec) (flow-rec-payload rec)))))\n   (define (flow-export-map store)\n     (if (null? store) (list) (cons (flow-export-entry (car store)) (flow-export-map (cdr store)))))\n   (define (flow-store-export) (flow-export-map flow-store))\n   (define (flow-max-id store m)\n     (if (null? store) m (flow-max-id (cdr store) (if (> (car (car store)) m) (car (car store)) m))))\n   (define (flow-store-import! data)\n     (begin (set! flow-store data) (set! flow-next-id (flow-max-id data 0))))\n   (define (flow-collect-resumable store)\n     (if (null? store)\n         (list)\n         (if (eq? (flow-rec-status (car (cdr (car store)))) (quote suspended))\n             (cons (car (car store)) (flow-collect-resumable (cdr store)))\n             (flow-collect-resumable (cdr store)))))\n   (define (flow-resumable-ids) (flow-collect-resumable flow-store))\n\n   (define (flow/status id)\n     (let ((rec (flow-store-get id)))\n       (if (null? rec) (quote unknown) (flow-rec-status rec))))\n   (define (flow/result id)\n     (let ((rec (flow-store-get id)))\n       (if (null? rec)\n           (list (quote flow-error) (quote no-such-flow))\n           (if (eq? (flow-rec-status rec) (quote done))\n               (flow-rec-payload rec)\n               (list (quote flow-error) (quote not-done))))))\n   (define (flow-list-step store)\n     (if (null? store)\n         (list)\n         (cons (list (car (car store)) (flow-rec-status (car (cdr (car store)))))\n               (flow-list-step (cdr store)))))\n   (define (flow/list) (flow-list-step flow-store))\n   (define (flow-pending-step store)\n     (if (null? store)\n         (list)\n         (if (eq? (flow-rec-status (car (cdr (car store)))) (quote suspended))\n             (cons (list (car (car store)) (flow-rec-payload (car (cdr (car store)))))\n                   (flow-pending-step (cdr store)))\n             (flow-pending-step (cdr store)))))\n   (define (flow/pending) (flow-pending-step flow-store))")
+  "(define flow-registry (list))\n   (define (flow-register! name proc) (set! flow-registry (cons (list name proc) flow-registry)))\n   (define (flow-lookup-in name reg)\n     (if (null? reg)\n         #f\n         (if (eq? (car (car reg)) name) (car (cdr (car reg))) (flow-lookup-in name (cdr reg)))))\n   (define (flow-lookup name) (flow-lookup-in name flow-registry))\n   (define (flow-name-of proc reg)\n     (if (null? reg)\n         #f\n         (if (eq? (car (cdr (car reg))) proc) (car (car reg)) (flow-name-of proc (cdr reg)))))\n\n   (define flow-store (list))\n   (define flow-next-id 0)\n   (define (flow-store-remove id store)\n     (if (null? store)\n         (list)\n         (if (= (car (car store)) id)\n             (flow-store-remove id (cdr store))\n             (cons (car store) (flow-store-remove id (cdr store))))))\n   (define (flow-store-put! id rec) (set! flow-store (cons (list id rec) (flow-store-remove id flow-store))))\n   (define (flow-store-find id store)\n     (if (null? store)\n         (list)\n         (if (= (car (car store)) id)\n             (car (cdr (car store)))\n             (flow-store-find id (cdr store)))))\n   (define (flow-store-get id) (flow-store-find id flow-store))\n\n   (define (flow-mk-rec name proc input log status payload)\n     (list name proc input log status payload))\n   (define (flow-rec-name r) (car r))\n   (define (flow-rec-proc r) (car (cdr r)))\n   (define (flow-rec-input r) (car (cdr (cdr r))))\n   (define (flow-rec-log r) (car (cdr (cdr (cdr r)))))\n   (define (flow-rec-status r) (car (cdr (cdr (cdr (cdr r))))))\n   (define (flow-rec-payload r) (car (cdr (cdr (cdr (cdr (cdr r)))))))\n   (define (flow-rec-resolve rec)\n     (let ((byname (flow-lookup (flow-rec-name rec))))\n       (if byname byname (flow-rec-proc rec))))\n\n   (define (flow-outcome id name proc input log outcome)\n     (if (eq? (car outcome) (quote flow-done))\n         (begin\n           (flow-store-put! id (flow-mk-rec name proc input log (quote done) (car (cdr outcome))))\n           (car (cdr outcome)))\n         (begin\n           (flow-store-put! id (flow-mk-rec name proc input log (quote suspended) (car (cdr outcome))))\n           (list (quote flow-suspended) id (car (cdr outcome))))))\n   (define (flow/start flow input)\n     (set! flow-next-id (+ flow-next-id 1))\n     (flow-outcome flow-next-id (flow-name-of flow flow-registry) flow input (list)\n       (flow-drive flow input (list))))\n   (define (flow/resume id value)\n     (let ((rec (flow-store-get id)))\n       (if (null? rec)\n           (list (quote flow-error) (quote no-such-flow))\n           (if (eq? (flow-rec-status rec) (quote suspended))\n               (let ((proc (flow-rec-resolve rec)))\n                 (let ((newlog (cons (list (flow-rec-payload rec) value) (flow-rec-log rec))))\n                   (flow-outcome id (flow-rec-name rec) proc (flow-rec-input rec) newlog\n                     (flow-drive proc (flow-rec-input rec) newlog))))\n               (list (quote flow-error) (quote not-suspended))))))\n   (define (flow/cancel id)\n     (let ((rec (flow-store-get id)))\n       (if (null? rec)\n           (list (quote flow-error) (quote no-such-flow))\n           (begin\n             (flow-store-put! id\n               (flow-mk-rec (flow-rec-name rec) (flow-rec-proc rec) (flow-rec-input rec)\n                 (flow-rec-log rec) (quote cancelled) #f))\n             (list (quote flow-cancelled) id)))))\n\n   (define (flow-export-entry entry)\n     (let ((rec (car (cdr entry))))\n       (list (car entry)\n         (flow-mk-rec (flow-rec-name rec) #f (flow-rec-input rec)\n           (flow-rec-log rec) (flow-rec-status rec) (flow-rec-payload rec)))))\n   (define (flow-export-map store)\n     (if (null? store) (list) (cons (flow-export-entry (car store)) (flow-export-map (cdr store)))))\n   (define (flow-store-export) (flow-export-map flow-store))\n   (define (flow-max-id store m)\n     (if (null? store) m (flow-max-id (cdr store) (if (> (car (car store)) m) (car (car store)) m))))\n   (define (flow-store-import! data)\n     (begin (set! flow-store data) (set! flow-next-id (flow-max-id data 0))))\n   (define (flow-collect-resumable store)\n     (if (null? store)\n         (list)\n         (if (eq? (flow-rec-status (car (cdr (car store)))) (quote suspended))\n             (cons (car (car store)) (flow-collect-resumable (cdr store)))\n             (flow-collect-resumable (cdr store)))))\n   (define (flow-resumable-ids) (flow-collect-resumable flow-store))\n\n   (define (flow/status id)\n     (let ((rec (flow-store-get id)))\n       (if (null? rec) (quote unknown) (flow-rec-status rec))))\n   (define (flow/result id)\n     (let ((rec (flow-store-get id)))\n       (if (null? rec)\n           (list (quote flow-error) (quote no-such-flow))\n           (if (eq? (flow-rec-status rec) (quote done))\n               (flow-rec-payload rec)\n               (list (quote flow-error) (quote not-done))))))\n   (define (flow-list-step store)\n     (if (null? store)\n         (list)\n         (cons (list (car (car store)) (flow-rec-status (car (cdr (car store)))))\n               (flow-list-step (cdr store)))))\n   (define (flow/list) (flow-list-step flow-store))\n   (define (flow-pending-step store)\n     (if (null? store)\n         (list)\n         (if (eq? (flow-rec-status (car (cdr (car store)))) (quote suspended))\n             (cons (list (car (car store)) (flow-rec-payload (car (cdr (car store)))))\n                   (flow-pending-step (cdr store)))\n             (flow-pending-step (cdr store)))))\n   (define (flow/pending) (flow-pending-step flow-store))\n\n   (define (flow-store-count store) (if (null? store) 0 (+ 1 (flow-store-count (cdr store)))))\n   (define (flow-gc-keep store)\n     (if (null? store)\n         (list)\n         (if (eq? (flow-rec-status (car (cdr (car store)))) (quote suspended))\n             (cons (car store) (flow-gc-keep (cdr store)))\n             (flow-gc-keep (cdr store)))))\n   (define (flow/gc)\n     (let ((before (flow-store-count flow-store)))\n       (set! flow-store (flow-gc-keep flow-store))\n       (- before (flow-store-count flow-store))))\n   (define (flow/forget id)\n     (let ((rec (flow-store-get id)))\n       (if (null? rec)\n           #f\n           (if (eq? (flow-rec-status rec) (quote suspended))\n               #f\n               (begin (set! flow-store (flow-store-remove id flow-store)) #t)))))")
 
 (define
   flow-load-store!
diff --git a/lib/flow/tests/hygiene.sx b/lib/flow/tests/hygiene.sx
new file mode 100644
index 00000000..a53122f8
--- /dev/null
+++ b/lib/flow/tests/hygiene.sx
@@ -0,0 +1,67 @@
+;; lib/flow/tests/hygiene.sx — Phase 5: store hygiene (flow/gc, flow/forget).
+
+(define flow-hyg-pass 0)
+(define flow-hyg-fail 0)
+(define flow-hyg-fails (list))
+
+(define
+  flow-hyg-test
+  (fn
+    (name actual expected)
+    (if
+      (= actual expected)
+      (set! flow-hyg-pass (+ flow-hyg-pass 1))
+      (begin
+        (set! flow-hyg-fail (+ flow-hyg-fail 1))
+        (append! flow-hyg-fails {:name name :expected expected :actual actual})))))
+
+(define flow-h (fn (src) (flow-run src)))
+
+;; ── flow/gc ─────────────────────────────────────────────────────
+(flow-hyg-test
+  "gc: empty store removes nothing"
+  (flow-h "(flow/gc)")
+  0)
+(flow-hyg-test
+  "gc: removes a done flow, keeps a suspended one"
+  (flow-h
+    "(defflow w (lambda (x) (suspend (quote q)))) (flow/start w 0) (flow/start (lambda (x) x) 5) (define removed (flow/gc)) (list removed (flow/list))")
+  (list 1 (list (list 1 "suspended"))))
+(flow-hyg-test
+  "gc: removes a cancelled flow"
+  (flow-h
+    "(defflow w (lambda (x) (suspend (quote q)))) (define id (car (cdr (flow/start w 0)))) (flow/cancel id) (flow/gc)")
+  1)
+(flow-hyg-test
+  "gc: a kept suspended flow is still resumable"
+  (flow-h
+    "(defflow w (sequence (lambda (x) (suspend (quote q))) (lambda (v) (* v 2)))) (define id (car (cdr (flow/start w 0)))) (flow/start (lambda (x) x) 1) (flow/gc) (flow/resume id 21)")
+  42)
+(flow-hyg-test
+  "gc: counts every terminal flow it drops"
+  (flow-h
+    "(flow/start (lambda (x) x) 1) (flow/start (lambda (x) x) 2) (defflow w (lambda (x) (suspend (quote q)))) (flow/start w 0) (flow/gc)")
+  2)
+
+;; ── flow/forget ─────────────────────────────────────────────────
+(flow-hyg-test
+  "forget: drops a completed flow"
+  (flow-h
+    "(defflow w (sequence (lambda (x) (suspend (quote q))) (lambda (v) v))) (define id (car (cdr (flow/start w 0)))) (flow/resume id 7) (list (flow/forget id) (flow/status id))")
+  (list true "unknown"))
+(flow-hyg-test
+  "forget: refuses to drop a live (suspended) flow"
+  (flow-h
+    "(defflow w (lambda (x) (suspend (quote q)))) (define id (car (cdr (flow/start w 0)))) (list (flow/forget id) (flow/status id))")
+  (list false "suspended"))
+(flow-hyg-test
+  "forget: drops a cancelled flow"
+  (flow-h
+    "(defflow w (lambda (x) (suspend (quote q)))) (define id (car (cdr (flow/start w 0)))) (flow/cancel id) (list (flow/forget id) (flow/status id))")
+  (list true "unknown"))
+(flow-hyg-test
+  "forget: unknown id yields false"
+  (flow-h "(flow/forget 999)")
+  false)
+
+(define flow-hyg-tests-run! (fn () {:total (+ flow-hyg-pass flow-hyg-fail) :passed flow-hyg-pass :failed flow-hyg-fail :fails flow-hyg-fails}))
diff --git a/plans/flow-on-sx.md b/plans/flow-on-sx.md
index 95a8a57b..108e74f9 100644
--- a/plans/flow-on-sx.md
+++ b/plans/flow-on-sx.md
@@ -16,7 +16,7 @@ federation extension via fed-sx for remote-node execution.
 
 ## Status (rolling)
 
-`bash lib/flow/conformance.sh` → **142/142** (Phases 1-7 complete)
+`bash lib/flow/conformance.sh` → **151/151** (Phases 1-7 complete; +store hygiene)
 
 ## Ground rules
 
@@ -141,6 +141,9 @@ something operators and authors actually use. Accumulation, not a rewrite.
 - [x] introspection API — `flow/status id`, `flow/result id`, `flow/list`,
   `flow/pending` (operator view of what each suspended flow awaits). 12 tests in
   `tests/api.sx`.
+- [x] store hygiene — `flow/gc` drops terminal (done/cancelled) records keeping
+  live suspended flows (returns count); `flow/forget id` drops one terminal record
+  and refuses live flows. Bounds unbounded store growth. 9 tests in `tests/hygiene.sx`.
 - [x] `tap` — side-effecting pass-through node (logging/metrics) that returns input
 - [x] `recover` — complement to try-catch for the fail-VALUE channel: run node; if it
   yields `(fail ...)`, run a recovery node on the reason