diff --git a/Makefile b/Makefile
index d0f8721..a7e70ba 100644
--- a/Makefile
+++ b/Makefile
@@ -33,7 +33,8 @@ SEARCH_Q     ?= computer
         chain-check chain-check-shards \
         falsify burn burn-kindergarten inspect bootstrap-crawler test-crawler crawl-ingest \
         recrawl-check bench-qa bench-qa-smoke bench-qa-progressive-and \
-        prometheus-trigger-probe \
+        prometheus-trigger-probe bench-5f-threshold-calibration \
+        bench-5f-selfmodel-snapshot bench-5f-finetuning-shardchain \
         bootstrap-math clean clean-db clean-data help \
         textbooks-summary textbooks-urls fetch-textbooks textbooks-stats textbooks-verify \
         crawl-textbooks crawl-textbooks-stats textbook textbook-list
@@ -489,6 +490,32 @@ bench-5f-falsification-live: bootstrap ## 5F Falsification via real arborist.qa.
 
 bench-5f-live: bench-5f-formulate-live bench-5f-feedback-loop-live bench-5f-function-live bench-5f-finetuning-live bench-5f-falsification-live ## all 5F Phase-1b.2 live wire-ups
 
+# #000025 §10.11 — persistent SelfModel-chain lineage. Each run of
+# bench-5f-selfmodel-snapshot runs the 5S/5T/5F embedded packs and
+# appends ONE chained snapshot (capability claims = the battery
+# rates) to SELFMODEL_CHAIN_DB. Run it >= 2x, then
+# bench-5f-finetuning-shardchain measures improvement between the two
+# most-recent snapshots — a real cross-run lineage, not a synthetic
+# parent/child pair. Operator targets: NOT part of `make bench-5f`,
+# `make test`, or a fresh checkout.
+SELFMODEL_CHAIN_DB ?= $(SHARDS_DIR)/selfmodel-chain.db
+bench-5f-selfmodel-snapshot: bootstrap ## #000025 §10.11 — append one SelfModel snapshot (rates as claims) to the chain shard
+	PYTHONUNBUFFERED=1 ARBORIST_SELFMODEL_CHAIN_DB=$(SELFMODEL_CHAIN_DB) \
+	    $(PY) bench/scripts/selfmodel_chain_snapshot.py
+bench-5f-finetuning-shardchain: bootstrap ## #000025 §10.11 — Finetuning over the two latest chain snapshots (run bench-5f-selfmodel-snapshot >=2x first)
+	PYTHONUNBUFFERED=1 ARBORIST_SELFMODEL_CHAIN_DB=$(SELFMODEL_CHAIN_DB) \
+	    $(PY) -m bench.batteries.runner --battery 5f --sub finetuning \
+	    --fixtures bench/fixtures/5f/finetuning-shardchain-v1.jsonl
+
+# #000025 §10.14 — ForkScore threshold-calibration handoff to #000012.
+# Runs the canonical 5S/5T/5F packs + the 5F live packs, reports
+# baseline rates / granularity / floor-constant sanity checks.
+# Pure measurement; output is the deliverable #000012 cites.
+FIVEF_CALIBRATION_OUT ?= bench/results/5f-threshold-calibration-$(shell date -u +%Y-%m-%d).md
+bench-5f-threshold-calibration: bootstrap ## #000025 §10.14 — 5S/5T/5F → ForkScore threshold calibration report
+	PYTHONUNBUFFERED=1 $(PY) bench/scripts/fivef_threshold_calibration.py \
+	    --out $(FIVEF_CALIBRATION_OUT)
+
 bench-5r: bootstrap ## 5R battery (React+Rearrange+Restore+Replicate+Resonate)
 	PYTHONUNBUFFERED=1 $(PY) -m bench.batteries.runner --battery 5r --sub react      --fixtures bench/fixtures/5r/react-v1.jsonl
 	PYTHONUNBUFFERED=1 $(PY) -m bench.batteries.runner --battery 5r --sub rearrange  --fixtures bench/fixtures/5r/rearrange-v1.jsonl
diff --git a/bench/batteries/b_5f.py b/bench/batteries/b_5f.py
index 182deb7..5e3027c 100644
--- a/bench/batteries/b_5f.py
+++ b/bench/batteries/b_5f.py
@@ -15,6 +15,7 @@ memory_snapshot carriers; future carriers fail/skip explicitly.
 
 from __future__ import annotations
 
+import time
 from pathlib import Path
 
 from bench.batteries.base import (
@@ -305,13 +306,83 @@ def _live_finetuning_measure(task: dict) -> dict:
             pass
 
 
+def _chain_finetuning_measure(task: dict) -> dict:
+    """Read the two most-recent SelfModel snapshots from a *persistent*
+    chain shard (#000025 §10.11) and return the parent/child measured
+    values for ``target_capability``.
+
+    The shard is the one ``bench/scripts/selfmodel_chain_snapshot.py``
+    appends to (default ``~/.arborist/shards/selfmodel-chain.db``,
+    overridable per-task via ``selfmodel_shard`` and via the
+    ``ARBORIST_SELFMODEL_CHAIN_DB`` env var). Unlike the Phase-1b.2
+    "live" path — which fabricates a parent + child in a fresh temp
+    shard every run — this reads a genuine lineage that outlives the
+    process: ``latest()`` is the child, its ``parent_selfmodel_root``
+    is the parent.
+
+    Raises if the shard is absent, has < 2 snapshots, or neither
+    snapshot carries a claim for ``target_capability`` — the caller
+    turns that into an honest task failure (this pack is meant to run
+    *after* the chain has been bootstrapped, not on a fresh checkout).
+    """
+    import os as _os
+
+    from arborist.selfmodel.store import claims_for, latest, load
+    from arborist.store import connect
+
+    metric = task["target_capability"]
+    # Resolution order: ARBORIST_SELFMODEL_CHAIN_DB env (the test /
+    # operator override) → the fixture's ``selfmodel_shard`` value
+    # (which is also the dispatch gate) → the conventional default.
+    raw_path = (
+        _os.environ.get("ARBORIST_SELFMODEL_CHAIN_DB")
+        or task.get("selfmodel_shard")
+        or "~/.arborist/shards/selfmodel-chain.db"
+    )
+    shard = Path(_os.path.expandvars(str(raw_path))).expanduser()
+    if not shard.exists():
+        raise FileNotFoundError(
+            f"selfmodel chain shard not found: {shard} — run "
+            "`make bench-5f-selfmodel-snapshot` (twice) to bootstrap it"
+        )
+    conn = connect(shard)
+    try:
+        child_row = latest(conn)
+        if child_row is None:
+            raise ValueError(f"no SelfModel snapshots in {shard}")
+        parent_root = child_row.get("parent_selfmodel_root")
+        if not parent_root:
+            raise ValueError(
+                f"chain shard {shard} has only one snapshot; need >= 2 "
+                "(run the bootstrapper again to extend the lineage)"
+            )
+        parent_row = load(conn, parent_root)
+        if parent_row is None:
+            raise ValueError(f"parent snapshot {parent_root[:12]}… missing from {shard}")
+
+        def _measured(root: str) -> float:
+            for c in claims_for(conn, root):
+                if c["metric"] == metric and c["measured_value"] is not None:
+                    return float(c["measured_value"])
+            raise ValueError(f"no claim for {metric!r} on snapshot {root[:12]}…")
+
+        return {
+            "parent_root": parent_root,
+            "child_root": child_row["selfmodel_root"],
+            "parent_measured": _measured(parent_root),
+            "child_measured": _measured(child_row["selfmodel_root"]),
+        }
+    finally:
+        conn.close()
+
+
 def run_finetuning(fixtures_path: Path) -> BatteryResult:
     """Adaptation improvement check + adaptation_efficiency metric.
 
     Each task asserts that ``child_measured_value >=
     parent_measured_value + expected_improvement_min``.
 
-    Two fixture modes:
+    Three fixture modes (selected per-task):
 
     - **Embedded** (Phase 1a): parent/child measured values come
       directly from the fixture; runner does the math.
@@ -323,6 +394,15 @@ def run_finetuning(fixtures_path: Path) -> BatteryResult:
       :func:`arborist.selfmodel.store.claims_for`, then runs the
       same improvement check. Tests the SelfModel persistence
       surface, not just the fixture data.
+    - **Shard-chain** (§10.11 — gate via ``"selfmodel_shard"``):
+      runner reads the two most-recent snapshots from a *persistent*
+      chain shard (the one ``bench/scripts/selfmodel_chain_snapshot.py``
+      grows, one snapshot per run) and measures improvement on
+      ``target_capability`` between them. This is the real lineage —
+      not a pair fabricated for the test — so the chained Δ reflects
+      genuine cross-run drift (0.0 today; the packs are at ceiling).
+      A task whose shard is absent / too short fails honestly: the
+      pack runs *after* the bootstrapper, not on a fresh checkout.
 
     Per #000025 §5.2 and the 2026-05-08 fbd99a8 review:
     ``adaptation_efficiency = Δimprovement / Δcapital_cost`` with
@@ -340,7 +420,12 @@ def run_finetuning(fixtures_path: Path) -> BatteryResult:
             )
             continue
         try:
-            if task.get("live"):
+            if task.get("selfmodel_shard"):
+                source = "shard-chain"
+                chain = _chain_finetuning_measure(task)
+                parent = float(chain["parent_measured"])
+                child = float(chain["child_measured"])
+            elif task.get("live"):
                 source = "live"
                 live = _live_finetuning_measure(task)
                 parent = float(live["parent_measured"])
@@ -370,6 +455,9 @@ def run_finetuning(fixtures_path: Path) -> BatteryResult:
                 "adaptation_efficiency": efficiency,
                 "expected": expected,
             }
+            if source == "shard-chain":
+                detail["chain_parent_root"] = chain["parent_root"]
+                detail["chain_child_root"] = chain["child_root"]
         except Exception as exc:  # noqa: BLE001
             passed = False
             detail = {"reason": f"{type(exc).__name__}: {exc}"}
@@ -725,15 +813,32 @@ def _live_delta_satisfied(state: dict, expected: dict) -> tuple[bool, str]:
     return True, "all live deltas satisfied"
 
 
+def _persisted_cost(state: dict) -> float:
+    """Real-workload cost of a live feedback chain: the persisted
+    footprint it actually produced, not the count of *requested* ops.
+
+    ``audit_event`` rows the chain wrote (count) + their body bytes /
+    1e6 (matching :func:`_capital_cost_delta`'s 1 MB = 1 cost-unit
+    convention). Every non-empty live chain writes ≥ 1 audit event
+    (the ``append_audit`` op, the ``memory_snapshot_landed`` event,
+    etc.), so this is > 0 for any chain that did work — :func:`_efficiency`
+    still handles the cost-0 edge as documented.
+    """
+    n_audit = len(state.get("audit_event_types", []))
+    body_bytes = sum(len(b) for b in state.get("audit_event_bodies", []) if b)
+    return float(n_audit) + body_bytes / 1e6
+
+
 def run_feedback_loop(fixtures_path: Path) -> BatteryResult:
-    """Integration coverage + feedback_efficiency metric.
+    """Integration coverage + feedback_efficiency + feedback_latency.
 
     Two fixture modes (selected per-task):
 
     - **Embedded** (Phase 1a): fixture provides a ``chain`` of
       ``(operation, observation)`` pairs; runner aggregates the
       observation text and checks ``expected_delta`` (a string
-      marker) appears in it.
+      marker) appears in it. No real work happens, so latency is
+      ``None`` and the cost-proxy stays ``len(chain)``.
     - **Live** (Phase 1b.2): fixture provides ``live_chain`` —
       a sequence of ops applied to a fresh temp arborist shard via
       :func:`_live_feedback_chain` — plus an ``expected_delta``
@@ -743,15 +848,28 @@ def run_feedback_loop(fixtures_path: Path) -> BatteryResult:
 
     Per #000025 §5.5 and the 2026-05-08 fbd99a8 review:
     ``feedback_efficiency = downstream_effect_count / Δcapital_cost``
-    with explicit zero-cost guards (see :func:`_efficiency`). For
-    Phase 1a the per-task cost is the chain length (one cost-unit
-    per operation); Phase 1b.2 will use the capital_ledger directly.
+    with explicit zero-cost guards (see :func:`_efficiency`).
+
+    **§10.13 (2026-05-11) — calibrated against real workload.** For a
+    live chain the cost is the *persisted footprint* :func:`_persisted_cost`
+    — the audit-event rows the chain actually wrote plus their body
+    bytes — instead of the Phase-1a ``len(chain)`` proxy (which
+    counted *requested* ops, not work done). §10.13 also computes
+    ``feedback_latency`` — listed in §5.5 since Phase 1a but never
+    implemented — as the wall-clock seconds to apply a live chain
+    against its temp shard. Latency is a wall-clock field
+    (non-deterministic run-to-run, like ``BatteryResult.timestamp``)
+    and is **not** consumed by ``fork_score`` — it's surfaced for
+    operational observability + the capital ledger (#000020), not for
+    fork selection. Embedded tasks keep ``len(chain)`` as cost and
+    report ``feedback_latency_seconds = None``.
     """
     per_task: list[TaskResult] = []
     integrated = 0
     total_obs = 0
     efficiency_values: list[float] = []
     finite_efficiency_values: list[float] = []
+    live_latencies: list[float] = []
     for task in iter_tasks(fixtures_path):
         task_id = task["id"]
         ok, reason = _carrier_check(task)
@@ -764,7 +882,10 @@ def run_feedback_loop(fixtures_path: Path) -> BatteryResult:
             if "live_chain" in task:
                 source = "live"
                 live_chain = task["live_chain"]
+                _t0 = time.perf_counter()
                 state = _live_feedback_chain(live_chain)
+                latency_s = time.perf_counter() - _t0
+                live_latencies.append(latency_s)
                 ok_live, why = _live_delta_satisfied(
                     state, task.get("expected_delta", {}) or {}
                 )
@@ -777,7 +898,7 @@ def run_feedback_loop(fixtures_path: Path) -> BatteryResult:
                 observed = "pass" if integrated_ok else "fail"
                 passed = observed == expected_outcome
                 downstream_effect = 1.0 if integrated_ok else 0.0
-                cost = float(chain_length)
+                cost = _persisted_cost(state)  # §10.13: real footprint
                 efficiency = _efficiency(downstream_effect, cost)
                 efficiency_values.append(efficiency)
                 if efficiency not in (
@@ -790,6 +911,9 @@ def run_feedback_loop(fixtures_path: Path) -> BatteryResult:
                     "reason": why,
                     "chain_length": chain_length,
                     "feedback_efficiency": efficiency,
+                    "feedback_latency_seconds": latency_s,
+                    "persisted_cost": cost,
+                    "persisted_audit_rows": len(state.get("audit_event_types", [])),
                     "live_state": {
                         "audit_event_count": len(state["audit_event_types"]),
                         "memory_branch_count": len(state["memory_branch_ids"]),
@@ -824,6 +948,7 @@ def run_feedback_loop(fixtures_path: Path) -> BatteryResult:
                     "delta_marker": delta_marker,
                     "chain_length": len(chain),
                     "feedback_efficiency": efficiency,
+                    "feedback_latency_seconds": None,  # no real work
                 }
         except Exception as exc:  # noqa: BLE001
             passed = False
@@ -838,6 +963,12 @@ def run_feedback_loop(fixtures_path: Path) -> BatteryResult:
         if finite_efficiency_values else 0.0
     )
     inf_count = sum(1 for e in efficiency_values if e == EFFICIENCY_INFINITE)
+    # §10.13: mean wall-clock latency over the live tasks (0.0 when a
+    # pack has no live_chain tasks). Wall-clock, run-to-run variable —
+    # not a fork_score input.
+    feedback_latency_mean = (
+        sum(live_latencies) / len(live_latencies) if live_latencies else 0.0
+    )
     meta = fixture_meta(fixtures_path)
     return _build_result(
         meta.get("sub_battery", "feedback-loop"),
@@ -848,6 +979,8 @@ def run_feedback_loop(fixtures_path: Path) -> BatteryResult:
             "downstream_effect_rate": integration_rate,
             "feedback_efficiency_mean_finite": mean_finite_efficiency,
             "feedback_efficiency_infinite_count": float(inf_count),
+            "feedback_latency_mean_seconds": feedback_latency_mean,
+            "feedback_live_task_count": float(len(live_latencies)),
         },
     )
 
diff --git a/bench/fixtures/5f/finetuning-shardchain-v1.jsonl b/bench/fixtures/5f/finetuning-shardchain-v1.jsonl
new file mode 100644
index 0000000..b02db6e
--- /dev/null
+++ b/bench/fixtures/5f/finetuning-shardchain-v1.jsonl
@@ -0,0 +1,7 @@
+{"_meta": {"battery": "5f", "sub_battery": "finetuning", "version": "v1", "task_count": 6, "notes": "#000025 §10.11: shard-chain Finetuning — reads the two most-recent SelfModel snapshots from a PERSISTENT chain shard (default ~/.arborist/shards/selfmodel-chain.db, override via ARBORIST_SELFMODEL_CHAIN_DB) and measures improvement on target_capability between them. The chain is grown one snapshot per run by `make bench-5f-selfmodel-snapshot`; run THAT (>=2x) before this pack. Tasks fail honestly if the shard is absent / too short — this is an operator pack, not part of `make bench-5f` or the default test suite. expected_improvement_min=0.0 = a no-regression assertion (the embedded packs are at ceiling, so the chained delta is 0.0)."}}
+{"id":"5f-ft-chain-001","battery":"5f","sub_battery":"finetuning","version":"v1","carrier":"capability_transition","domain":"capability_transition","pi_star_ref":"pi_selfmodel_v1","selfmodel_shard":"~/.arborist/shards/selfmodel-chain.db","target_capability":"5S-syntax","expected_improvement_min":0.0,"resource_budget":{"max_compute_ms_delta":0,"max_storage_delta_bytes":0},"expected":"pass"}
+{"id":"5f-ft-chain-002","battery":"5f","sub_battery":"finetuning","version":"v1","carrier":"capability_transition","domain":"capability_transition","pi_star_ref":"pi_selfmodel_v1","selfmodel_shard":"~/.arborist/shards/selfmodel-chain.db","target_capability":"5S-syllogism","expected_improvement_min":0.0,"resource_budget":{"max_compute_ms_delta":0,"max_storage_delta_bytes":0},"expected":"pass"}
+{"id":"5f-ft-chain-003","battery":"5f","sub_battery":"finetuning","version":"v1","carrier":"capability_transition","domain":"capability_transition","pi_star_ref":"pi_selfmodel_v1","selfmodel_shard":"~/.arborist/shards/selfmodel-chain.db","target_capability":"5T-time","expected_improvement_min":0.0,"resource_budget":{"max_compute_ms_delta":0,"max_storage_delta_bytes":0},"expected":"pass"}
+{"id":"5f-ft-chain-004","battery":"5f","sub_battery":"finetuning","version":"v1","carrier":"capability_transition","domain":"capability_transition","pi_star_ref":"pi_selfmodel_v1","selfmodel_shard":"~/.arborist/shards/selfmodel-chain.db","target_capability":"5T-truthtables","expected_improvement_min":0.0,"resource_budget":{"max_compute_ms_delta":0,"max_storage_delta_bytes":0},"expected":"pass"}
+{"id":"5f-ft-chain-005","battery":"5f","sub_battery":"finetuning","version":"v1","carrier":"capability_transition","domain":"capability_transition","pi_star_ref":"pi_selfmodel_v1","selfmodel_shard":"~/.arborist/shards/selfmodel-chain.db","target_capability":"5F-feedback-loop","expected_improvement_min":0.0,"resource_budget":{"max_compute_ms_delta":0,"max_storage_delta_bytes":0},"expected":"pass"}
+{"id":"5f-ft-chain-006","battery":"5f","sub_battery":"finetuning","version":"v1","carrier":"capability_transition","domain":"capability_transition","pi_star_ref":"pi_selfmodel_v1","selfmodel_shard":"~/.arborist/shards/selfmodel-chain.db","target_capability":"5F-falsification","expected_improvement_min":0.0,"resource_budget":{"max_compute_ms_delta":0,"max_storage_delta_bytes":0},"expected":"pass"}
diff --git a/bench/results/5f-threshold-calibration-2026-05-11.md b/bench/results/5f-threshold-calibration-2026-05-11.md
new file mode 100644
index 0000000..39e3b36
--- /dev/null
+++ b/bench/results/5f-threshold-calibration-2026-05-11.md
@@ -0,0 +1,60 @@
+# 5S/5T/5F → v8 ForkScore threshold-calibration handoff
+
+**Date:** 2026-05-11T11:26:39Z
+**Ticket:** #000025 §10.14 (closure deliverable) — handoff to #000012.
+**Method:** ran the canonical 5S/5T/5F sub-batteries (the packs `fork_score._BATTERY_RATE_KEYS` reads) plus the 5F live packs; computed baseline rates, observability granularity (1/n), and ran `fork_score` on the parent vs three synthetic child perturbations. Pure measurement.
+
+## 1. Baseline rates + granularity
+
+Each row's *rate* is the single metric `fork_score` consumes for that sub-battery (`_BATTERY_RATE_KEYS`). *Granularity* = 1/n — the smallest rate change a single fixture flip can produce, i.e. the finest Δ the scorer could ever observe on that pack.
+
+| battery | sub-battery | fixtures (n) | embedded rate | live rate | granularity (1/n) |
+|---|---|---|---|---|---|
+| 5s | syntax | 10 | 1.0000 | — | 0.1000 (10.0pp) |
+| 5s | semantics | 8 | 1.0000 | — | 0.1250 (12.5pp) |
+| 5s | syllogism | 30 | 1.0000 | — | 0.0333 (3.3pp) |
+| 5s | synthesis | 30 | 1.0000 | — | 0.0333 (3.3pp) |
+| 5s | semiotics | 30 | 1.0000 | — | 0.0333 (3.3pp) |
+| 5t | transfer-learning | 30 | 1.0000 | — | 0.0333 (3.3pp) |
+| 5t | triangulation | 30 | 1.0000 | — | 0.0333 (3.3pp) |
+| 5t | truthtables | 30 | 1.0000 | — | 0.0333 (3.3pp) |
+| 5t | transitivity | 30 | 1.0000 | — | 0.0333 (3.3pp) |
+| 5t | time | 30 | 1.0000 | — | 0.0333 (3.3pp) |
+| 5f | function | 50 | 1.0000 | 1.0000 | 0.0200 (2.0pp) |
+| 5f | finetuning | 50 | 1.0000 | 1.0000 | 0.0200 (2.0pp) |
+| 5f | falsification | 62 | 1.0000 | 1.0000 | 0.0161 (1.6pp) |
+| 5f | formulate | 50 | 1.0000 | 1.0000 | 0.0200 (2.0pp) |
+| 5f | feedback-loop | 50 | 1.0000 | 1.0000 | 0.0200 (2.0pp) |
+
+- **5S mean baseline rate:** 1.0000
+- **5T mean baseline rate:** 1.0000
+- **5F mean baseline rate:** 1.0000
+- **Coarsest pack granularity:** 0.1250 (12.5pp)
+- **Finest pack granularity:** 0.0161 (1.6pp)
+
+## 2. Identity-fork verdict (no change)
+
+`fork_score(parent, parent)` → **MARGINAL (score +0.0000)**
+
+Every 5S/5T/5F pack is at ceiling (rate 1.0) at HEAD, so every Δ-rate term is exactly 0 and the identity fork lands in the `[0, SIGNAL_FLOOR)` band → **MARGINAL**, not ACCEPT. Takeaway for #000012: an unchanged child is *not* auto-accepted; positive score has to come from a Δ-rate gain (needs harder fixtures, see §4), an efficiency-bonus increase (`adaptation_efficiency` / `feedback_efficiency`), or one of the non-bench terms (`selfmodel_calibration_gain`, `audit_completeness`, …).
+
+## 3. Floor-constant sanity checks
+
+`SIGNAL_FLOOR = 0.05` · `HARD_REGRESSION_FLOOR = 0.05` (current `arborist/substrate/fork_score.py`). The production parent is at ceiling, so these are exercised against a synthetic *degraded parent* — every 5F sub-battery rate knocked to 0.90, giving a child headroom to improve.
+
+| scenario | verdict |
+|---|---|
+| identity — `fork_score(HEAD, HEAD)` | MARGINAL (score +0.0000) |
+| degraded parent → child recovers **all 5** 5F subs by +0.06 | ACCEPT (score +0.0600) |
+| degraded parent → child recovers **only 1** 5F sub by +0.06 | MARGINAL (score +0.0120) |
+| degraded parent → child drops one 5F sub by −0.05 | REJECT (score -0.0300) — flags: REGRESSION_5F:5f/falsification: -0.050 |
+
+Row 2 vs row 3 is the **5× averaging dilution**: `_delta_5f` means over all 5 sub-batteries, so the same +0.06 gain scores `1.0·0.06 = 0.06` (ACCEPT) when applied to all five subs but only `1.0·(0.06/5) = 0.012` (MARGINAL) when applied to one. Each battery contributes a separate Δ-term at weight 1.0, so a uniform +`SIGNAL_FLOOR` across *every* sub of *all three* batteries would score `~0.15`.
+
+## 4. Recommendation for #000012
+
+- **Keep `SIGNAL_FLOOR = 0.05` and `HARD_REGRESSION_FLOOR = 0.05`.** They match `docs/bench-maxing.md`'s 5-pp signal floor and the sanity checks in §3 behave as documented.
+- **Granularity caveat (load-bearing):** the foundational 5S packs are *coarser* than the floors — `syntax` (n=10 → 10.0pp) and `semantics` (n=8 → 12.5pp). On those packs a single fixture flip is ≥ 5pp, so *any* regression there trips the hard-reject. That is the intended zero-tolerance behaviour on the syntax/semantics base — not a bug — but #000012 should document it: HARD_REGRESSION_FLOOR is not a tunable knob on the small packs, it's effectively 'one fixture'. The n=30 / n=50 / n=62 packs have 3.3pp / 2.0pp / 1.6pp granularity, so there 5pp ≈ 1.5–3 fixture flips.
+- **5× averaging dilution (document this in #000012):** a single sub-battery's rate gain is worth a fifth of its face value because `_delta_5{s,t,f}` means over 5 subs. So 'a fork must improve by `SIGNAL_FLOOR`' really means *one of*: ~`0.25` on a single sub, ~`0.05` uniform across one battery's 5 subs, or ~`0.017` uniform across the whole 15-sub suite. If #000012 wants single-sub improvements to weigh equally it should switch `_delta_*` from mean to max-or-sum — but that's a #000012-owned design call, not a calibration finding.
+- **Ceiling saturation:** until harder fixtures drop a pack's baseline below 1.0, the `α·Δ5s + β·Δ5t + γ·Δ5f` terms can only be ≤ 0. ForkScore acceptance at the current pack difficulty is driven by the efficiency bonuses + non-bench terms. If #000012 wants the bench Δ-rate terms to carry real positive signal, the 5S/5T/5F packs need a harder tier (or a deliberately-degraded parent baseline) — track that as a #000025 follow-up, not a #000012 blocker.
+- **No constant change shipped by this calibration.** This is a handoff document; if #000012 decides to move a floor it owns that edit (and the resulting `governance_policy_hash` is unaffected — ForkScore constants don't fold into it; they're estimator parameters pinned by `ESTIMATOR_VERSION`).
diff --git a/bench/scripts/fivef_threshold_calibration.py b/bench/scripts/fivef_threshold_calibration.py
new file mode 100644
index 0000000..7177389
--- /dev/null
+++ b/bench/scripts/fivef_threshold_calibration.py
@@ -0,0 +1,349 @@
+"""5S/5T/5F → v8 ForkScore threshold-calibration handoff (#000025 §10.14).
+
+Closure deliverable for ticket #000025 §10.14 ("threshold calibration for
+v8 selection acceptance handed off to #000012"). Pure measurement — runs
+the canonical 5S / 5T / 5F sub-batteries (embedded packs + the 5F live
+packs), builds the parent/child metrics bundle the ForkScore reads
+(:func:`arborist.substrate.fork_score.bench_result_to_metrics` shape),
+and reports:
+
+  1. Per-pack baseline rate (the ``_BATTERY_RATE_KEYS`` metric the scorer
+     consumes) + fixture count + 1/n observability granularity.
+  2. The identity-fork verdict — ``fork_score(parent, parent)`` — which
+     tells #000012 what "no change" scores to (it's MARGINAL, not
+     ACCEPT, because every Δ-rate term is 0).
+  3. Synthetic-perturbation verdicts: a single +``SIGNAL_FLOOR`` bump on
+     one 5F sub-battery → ACCEPT; a single −``HARD_REGRESSION_FLOOR``
+     drop → REJECT. Confirms the floor constants do what the docstrings
+     claim.
+  4. A recommendation block: are ``SIGNAL_FLOOR`` / ``HARD_REGRESSION_FLOOR``
+     (both 0.05 today) appropriate given the observed pack granularity?
+
+No mutation, no LLM call, no schema / governance-hash / canonicalization
+change. The markdown report is the deliverable; #000012 cites it.
+"""
+
+from __future__ import annotations
+
+import argparse
+import statistics
+import sys
+from dataclasses import asdict
+from datetime import datetime, timezone
+from pathlib import Path
+
+# bench/ is on sys.path when run as a module (python -m); when run as a
+# script, add the repo root so `import bench...` and `import arborist...`
+# resolve.
+_REPO_ROOT = Path(__file__).resolve().parents[2]
+if str(_REPO_ROOT) not in sys.path:
+    sys.path.insert(0, str(_REPO_ROOT))
+
+from bench.batteries import b_5f, b_5s, b_5t  # noqa: E402
+from bench.batteries.base import BatteryResult  # noqa: E402
+from arborist.substrate.fork_score import (  # noqa: E402
+    HARD_REGRESSION_FLOOR,
+    SIGNAL_FLOOR,
+    _BATTERY_RATE_KEYS,
+    bench_result_to_metrics,
+    fork_score,
+)
+
+_FIX = _REPO_ROOT / "bench" / "fixtures"
+
+# The canonical sub-battery → fixture-pack map the ForkScore Δ-rate terms
+# read. Mirrors bench.batteries.runner._DEFAULT_FIXTURES but restricted
+# to the keys present in fork_score._BATTERY_RATE_KEYS (so legacy 5t
+# "transfer" is excluded — the scorer drops it). The "live" 5F packs are
+# included as a separate column because their runners exercise real
+# arborist surfaces on temp shards (Phase 1b.2).
+_EMBEDDED_PACKS: dict[tuple[str, str], Path] = {
+    ("5s", "syntax"): _FIX / "5s" / "syntax-v1.jsonl",
+    ("5s", "semantics"): _FIX / "5s" / "semantics-v1.jsonl",
+    ("5s", "syllogism"): _FIX / "5s" / "syllogism-v1.jsonl",
+    ("5s", "synthesis"): _FIX / "5s" / "synthesis-v1.jsonl",
+    ("5s", "semiotics"): _FIX / "5s" / "semiotics-v1.jsonl",
+    ("5t", "transfer-learning"): _FIX / "5t" / "transfer-learning-v2.jsonl",
+    ("5t", "triangulation"): _FIX / "5t" / "triangulation-v1.jsonl",
+    ("5t", "truthtables"): _FIX / "5t" / "truthtables-v1.jsonl",
+    ("5t", "transitivity"): _FIX / "5t" / "transitivity-v1.jsonl",
+    ("5t", "time"): _FIX / "5t" / "time-v1.jsonl",
+    ("5f", "function"): _FIX / "5f" / "function-v1.jsonl",
+    ("5f", "finetuning"): _FIX / "5f" / "finetuning-v1.jsonl",
+    ("5f", "falsification"): _FIX / "5f" / "falsification-v1.jsonl",
+    ("5f", "formulate"): _FIX / "5f" / "formulate-v1.jsonl",
+    ("5f", "feedback-loop"): _FIX / "5f" / "feedback-loop-v1.jsonl",
+}
+
+_LIVE_PACKS: dict[tuple[str, str], Path] = {
+    ("5f", "function"): _FIX / "5f" / "function-live-v1.jsonl",
+    ("5f", "finetuning"): _FIX / "5f" / "finetuning-live-v1.jsonl",
+    ("5f", "falsification"): _FIX / "5f" / "falsification-live-v1.jsonl",
+    ("5f", "formulate"): _FIX / "5f" / "formulate-live-v1.jsonl",
+    ("5f", "feedback-loop"): _FIX / "5f" / "feedback-loop-live-v1.jsonl",
+}
+
+_SUB_RUNNERS = {"5s": b_5s.SUB_BATTERIES, "5t": b_5t.SUB_BATTERIES, "5f": b_5f.SUB_BATTERIES}
+
+
+def _run_pack(battery: str, sub: str, path: Path) -> BatteryResult:
+    return _SUB_RUNNERS[battery][sub](path)
+
+
+def _results_payload(packs: dict[tuple[str, str], Path]) -> dict:
+    """Run every pack and shape the output like bench.batteries.runner."""
+    results = []
+    for (battery, sub), path in packs.items():
+        r = _run_pack(battery, sub, path)
+        results.append(asdict(r))
+    return {"schema_version": "bench-result-v1", "results": results}
+
+
+def _rate_of(metrics: dict, battery: str, sub: str) -> float | None:
+    key = _BATTERY_RATE_KEYS.get(battery, {}).get(sub)
+    if key is None:
+        return None
+    v = metrics.get(key)
+    return float(v) if v is not None else None
+
+
+def _deepcopy_bundle(metrics_bundle: dict) -> dict:
+    return {b: {s: dict(m) for s, m in subs.items()} for b, subs in metrics_bundle.items()}
+
+
+def _set_rate(bundle: dict, battery: str, sub: str, value: float) -> None:
+    key = _BATTERY_RATE_KEYS[battery][sub]
+    bundle.setdefault(battery, {}).setdefault(sub, {})[key] = max(0.0, min(1.0, value))
+
+
+def _shift_rate(bundle: dict, battery: str, sub: str, delta: float) -> None:
+    key = _BATTERY_RATE_KEYS[battery][sub]
+    base = float(bundle.get(battery, {}).get(sub, {}).get(key, 0.0))
+    _set_rate(bundle, battery, sub, base + delta)
+
+
+def _degraded_parent(parent: dict, knock_to: float = 0.90) -> dict:
+    """A synthetic parent with every 5F sub-battery rate knocked down to
+    ``knock_to`` — gives a child headroom to improve. The production
+    parent is at ceiling (rate 1.0 on every pack), so threshold
+    mechanics can only be exercised against a below-ceiling baseline."""
+    out = _deepcopy_bundle(parent)
+    for sub in _BATTERY_RATE_KEYS["5f"]:
+        _set_rate(out, "5f", sub, knock_to)
+    return out
+
+
+def _fmt_verdict(sf) -> str:
+    flags = f" — flags: {', '.join(sf.flags)}" if sf.flags else ""
+    return f"{sf.verdict} (score {sf.score:+.4f}){flags}"
+
+
+def build_report() -> str:
+    now = datetime.now(timezone.utc).strftime("%Y-%m-%dT%H:%M:%SZ")
+    embedded = _results_payload(_EMBEDDED_PACKS)
+    live = _results_payload(_LIVE_PACKS)
+    parent = bench_result_to_metrics(embedded)
+    live_metrics = bench_result_to_metrics(live)
+
+    # ---- per-pack table rows -------------------------------------------------
+    rows = []
+    granularities: list[float] = []
+    for r in embedded["results"]:
+        battery, sub = r["battery"], r["sub_battery"]
+        n = r["pass_count"] + r["fail_count"]
+        rate = _rate_of(r["metrics"], battery, sub)
+        gran = (1.0 / n) if n else float("nan")
+        if n:
+            granularities.append(gran)
+        live_r = next(
+            (lr for lr in live["results"] if lr["battery"] == battery and lr["sub_battery"] == sub),
+            None,
+        )
+        live_rate = _rate_of(live_r["metrics"], battery, sub) if live_r else None
+        rows.append((battery, sub, n, rate, gran, live_rate))
+
+    coarsest = max(granularities) if granularities else float("nan")
+    finest = min(granularities) if granularities else float("nan")
+
+    # ---- fork-score sanity verdicts ------------------------------------------
+    # The production parent is at ceiling (rate 1.0 everywhere), so a
+    # "+SIGNAL_FLOOR" child clamps right back to 1.0 and shows nothing.
+    # Exercise the threshold mechanics against a synthetic below-ceiling
+    # parent (every 5F sub knocked to 0.90).
+    identity = fork_score(parent, parent)
+    knock = 0.90
+    degraded = _degraded_parent(parent, knock)
+
+    # Child recovers EVERY 5F sub uniformly by 0.06 (> SIGNAL_FLOOR each)
+    # → mean Δ5F = 0.06 → score = γ·0.06 = 0.06 ≥ SIGNAL_FLOOR → ACCEPT.
+    child_uniform = _deepcopy_bundle(degraded)
+    for sub in _BATTERY_RATE_KEYS["5f"]:
+        _shift_rate(child_uniform, "5f", sub, 0.06)
+    accept_uniform = fork_score(degraded, child_uniform)
+
+    # Child recovers only ONE 5F sub by 0.06 → mean Δ5F = 0.06/5 = 0.012
+    # → score 0.012 < SIGNAL_FLOOR → MARGINAL. This is the 5× averaging
+    # dilution: a single-sub gain is worth a fifth of its face value.
+    child_single = _deepcopy_bundle(degraded)
+    _shift_rate(child_single, "5f", "function", 0.06)
+    marginal_single = fork_score(degraded, child_single)
+
+    # Child drops one 5F sub by HARD_REGRESSION_FLOOR from the degraded
+    # parent → hard regression → REJECT regardless of the other terms.
+    child_regress = _deepcopy_bundle(degraded)
+    _shift_rate(child_regress, "5f", "falsification", -HARD_REGRESSION_FLOOR)
+    reject_regress = fork_score(degraded, child_regress)
+
+    # ---- emit ----------------------------------------------------------------
+    out: list[str] = []
+    out.append("# 5S/5T/5F → v8 ForkScore threshold-calibration handoff")
+    out.append("")
+    out.append(f"**Date:** {now}")
+    out.append("**Ticket:** #000025 §10.14 (closure deliverable) — handoff to #000012.")
+    out.append(
+        "**Method:** ran the canonical 5S/5T/5F sub-batteries (the packs "
+        "`fork_score._BATTERY_RATE_KEYS` reads) plus the 5F live packs; "
+        "computed baseline rates, observability granularity (1/n), and "
+        "ran `fork_score` on the parent vs three synthetic child "
+        "perturbations. Pure measurement."
+    )
+    out.append("")
+    out.append("## 1. Baseline rates + granularity")
+    out.append("")
+    out.append(
+        "Each row's *rate* is the single metric `fork_score` consumes for "
+        "that sub-battery (`_BATTERY_RATE_KEYS`). *Granularity* = 1/n — "
+        "the smallest rate change a single fixture flip can produce, i.e. "
+        "the finest Δ the scorer could ever observe on that pack."
+    )
+    out.append("")
+    out.append("| battery | sub-battery | fixtures (n) | embedded rate | live rate | granularity (1/n) |")
+    out.append("|---|---|---|---|---|---|")
+    for battery, sub, n, rate, gran, live_rate in rows:
+        rate_s = f"{rate:.4f}" if rate is not None else "—"
+        live_s = f"{live_rate:.4f}" if live_rate is not None else "—"
+        out.append(f"| {battery} | {sub} | {n} | {rate_s} | {live_s} | {gran:.4f} ({gran*100:.1f}pp) |")
+    out.append("")
+    # Per-battery mean rate.
+    for battery in ("5s", "5t", "5f"):
+        vals = [rate for b, s, n, rate, g, lr in rows if b == battery and rate is not None]
+        if vals:
+            out.append(f"- **{battery.upper()} mean baseline rate:** {statistics.fmean(vals):.4f}")
+    out.append(f"- **Coarsest pack granularity:** {coarsest:.4f} ({coarsest*100:.1f}pp)")
+    out.append(f"- **Finest pack granularity:** {finest:.4f} ({finest*100:.1f}pp)")
+    out.append("")
+    out.append("## 2. Identity-fork verdict (no change)")
+    out.append("")
+    out.append(f"`fork_score(parent, parent)` → **{_fmt_verdict(identity)}**")
+    out.append("")
+    out.append(
+        "Every 5S/5T/5F pack is at ceiling (rate 1.0) at HEAD, so every "
+        "Δ-rate term is exactly 0 and the identity fork lands in the "
+        "`[0, SIGNAL_FLOOR)` band → **MARGINAL**, not ACCEPT. Takeaway for "
+        "#000012: an unchanged child is *not* auto-accepted; positive "
+        "score has to come from a Δ-rate gain (needs harder fixtures, see "
+        "§4), an efficiency-bonus increase (`adaptation_efficiency` / "
+        "`feedback_efficiency`), or one of the non-bench terms "
+        "(`selfmodel_calibration_gain`, `audit_completeness`, …)."
+    )
+    out.append("")
+    out.append("## 3. Floor-constant sanity checks")
+    out.append("")
+    out.append(
+        f"`SIGNAL_FLOOR = {SIGNAL_FLOOR}` · `HARD_REGRESSION_FLOOR = "
+        f"{HARD_REGRESSION_FLOOR}` (current `arborist/substrate/fork_score.py`). "
+        f"The production parent is at ceiling, so these are exercised against "
+        f"a synthetic *degraded parent* — every 5F sub-battery rate knocked "
+        f"to {knock:.2f}, giving a child headroom to improve."
+    )
+    out.append("")
+    out.append("| scenario | verdict |")
+    out.append("|---|---|")
+    out.append(f"| identity — `fork_score(HEAD, HEAD)` | {_fmt_verdict(identity)} |")
+    out.append(f"| degraded parent → child recovers **all 5** 5F subs by +0.06 | {_fmt_verdict(accept_uniform)} |")
+    out.append(f"| degraded parent → child recovers **only 1** 5F sub by +0.06 | {_fmt_verdict(marginal_single)} |")
+    out.append(f"| degraded parent → child drops one 5F sub by −{HARD_REGRESSION_FLOOR} | {_fmt_verdict(reject_regress)} |")
+    out.append("")
+    out.append(
+        "Row 2 vs row 3 is the **5× averaging dilution**: `_delta_5f` means "
+        "over all 5 sub-batteries, so the same +0.06 gain scores `1.0·0.06 = "
+        "0.06` (ACCEPT) when applied to all five subs but only `1.0·(0.06/5) "
+        "= 0.012` (MARGINAL) when applied to one. Each battery contributes a "
+        "separate Δ-term at weight 1.0, so a uniform +`SIGNAL_FLOOR` across "
+        "*every* sub of *all three* batteries would score `~0.15`."
+    )
+    out.append("")
+    out.append("## 4. Recommendation for #000012")
+    out.append("")
+    out.append(
+        f"- **Keep `SIGNAL_FLOOR = {SIGNAL_FLOOR}` and "
+        f"`HARD_REGRESSION_FLOOR = {HARD_REGRESSION_FLOOR}`.** They match "
+        "`docs/bench-maxing.md`'s 5-pp signal floor and the sanity checks "
+        "in §3 behave as documented."
+    )
+    out.append(
+        f"- **Granularity caveat (load-bearing):** the foundational 5S "
+        f"packs are *coarser* than the floors — `syntax` (n=10 → 10.0pp) "
+        f"and `semantics` (n=8 → 12.5pp). On those packs a single fixture "
+        f"flip is ≥ {HARD_REGRESSION_FLOOR*100:.0f}pp, so *any* regression "
+        f"there trips the hard-reject. That is the intended zero-tolerance "
+        f"behaviour on the syntax/semantics base — not a bug — but #000012 "
+        f"should document it: HARD_REGRESSION_FLOOR is not a tunable knob "
+        f"on the small packs, it's effectively 'one fixture'. The n=30 / "
+        f"n=50 / n=62 packs have 3.3pp / 2.0pp / 1.6pp granularity, so "
+        f"there {HARD_REGRESSION_FLOOR*100:.0f}pp ≈ 1.5–3 fixture flips."
+    )
+    out.append(
+        "- **5× averaging dilution (document this in #000012):** a single "
+        "sub-battery's rate gain is worth a fifth of its face value because "
+        "`_delta_5{s,t,f}` means over 5 subs. So 'a fork must improve "
+        f"by `SIGNAL_FLOOR`' really means *one of*: ~`{SIGNAL_FLOOR*5:.2f}` "
+        f"on a single sub, ~`{SIGNAL_FLOOR:.2f}` uniform across one "
+        f"battery's 5 subs, or ~`{SIGNAL_FLOOR/3:.3f}` uniform across the "
+        "whole 15-sub suite. If #000012 wants single-sub improvements to "
+        "weigh equally it should switch `_delta_*` from mean to "
+        "max-or-sum — but that's a #000012-owned design call, not a "
+        "calibration finding."
+    )
+    out.append(
+        "- **Ceiling saturation:** until harder fixtures drop a pack's "
+        "baseline below 1.0, the `α·Δ5s + β·Δ5t + γ·Δ5f` terms can only be "
+        "≤ 0. ForkScore acceptance at the current pack difficulty is "
+        "driven by the efficiency bonuses + non-bench terms. If #000012 "
+        "wants the bench Δ-rate terms to carry real positive signal, the "
+        "5S/5T/5F packs need a harder tier (or a deliberately-degraded "
+        "parent baseline) — track that as a #000025 follow-up, not a "
+        "#000012 blocker."
+    )
+    out.append(
+        "- **No constant change shipped by this calibration.** This is a "
+        "handoff document; if #000012 decides to move a floor it owns that "
+        "edit (and the resulting `governance_policy_hash` is unaffected — "
+        "ForkScore constants don't fold into it; they're estimator "
+        "parameters pinned by `ESTIMATOR_VERSION`)."
+    )
+    out.append("")
+    return "\n".join(out)
+
+
+def main(argv: list[str] | None = None) -> int:
+    p = argparse.ArgumentParser(description=__doc__.splitlines()[0])
+    p.add_argument(
+        "--out",
+        type=Path,
+        default=None,
+        help="Write the markdown report here (default: stdout).",
+    )
+    args = p.parse_args(argv)
+    md = build_report()
+    if args.out:
+        args.out.parent.mkdir(parents=True, exist_ok=True)
+        args.out.write_text(md, encoding="utf-8")
+        print(f"wrote {args.out}")
+    else:
+        print(md)
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/bench/scripts/selfmodel_chain_snapshot.py b/bench/scripts/selfmodel_chain_snapshot.py
new file mode 100644
index 0000000..81a60a4
--- /dev/null
+++ b/bench/scripts/selfmodel_chain_snapshot.py
@@ -0,0 +1,171 @@
+"""Append one SelfModel snapshot to a persistent chain shard, with
+capability claims drawn from a fresh 5S/5T/5F bench run (#000025 §10.11).
+
+Why this exists: Phase 1a's Finetuning sub-battery scored *synthetic*
+parent→child SelfModel pairs; Phase 1b.2's "live" path round-trips a
+parent + child through a *fresh temp* shard each run. §10.11 wants the
+real thing — a SelfModel lineage that *persists across runs*, so the
+Finetuning runner can measure improvement between two genuine,
+chained snapshots instead of a pair fabricated for the occasion.
+
+Each invocation:
+
+  1. Runs the canonical 5S/5T/5F sub-batteries (embedded packs — the
+     ones `fork_score._BATTERY_RATE_KEYS` reads). Deterministic, ~1s,
+     no LLM call.
+  2. Builds one :class:`arborist.selfmodel.CapabilityClaim` per
+     sub-battery: ``metric = "5S-syntax"`` etc., ``measured_value`` =
+     that pack's rate, ``eval_digest`` = that pack's fixture digest,
+     ``threshold`` = ``fork_score.SIGNAL_FLOOR`` (the rate floor below
+     which a fork-score Δ on this capability is a hard regression).
+  3. Calls :func:`arborist.selfmodel.snapshot` (which auto-parents to
+     the latest root in the shard) → :func:`with_claims` →
+     :func:`store_snapshot`. The new snapshot's distinct parent makes
+     it a distinct root, so the chain grows by exactly one per run.
+
+Output shard defaults to ``~/.arborist/shards/selfmodel-chain.db``
+(override with ``--shard`` or ``ARBORIST_SELFMODEL_CHAIN_DB``). The
+shard carries an ``audit_events`` table (every ``store_snapshot``
+write chains through it), so ``make chain-check-shards`` covers it.
+
+Idempotent on content: re-running with no chain growth in between is
+a no-op only if the parent root is unchanged — which it isn't after
+the first append, so successive runs always extend the lineage. The
+bench rates are at ceiling (1.0) today, so the chained Δ is 0.0; the
+point is that the *mechanism* is real and the lineage outlives any
+single process.
+"""
+
+from __future__ import annotations
+
+import argparse
+import os
+import sys
+import time
+from dataclasses import asdict
+from pathlib import Path
+
+_REPO_ROOT = Path(__file__).resolve().parents[2]
+if str(_REPO_ROOT) not in sys.path:
+    sys.path.insert(0, str(_REPO_ROOT))
+
+from bench.batteries import b_5f, b_5s, b_5t  # noqa: E402
+from arborist.selfmodel import CapabilityClaim, snapshot, store_snapshot  # noqa: E402
+from arborist.selfmodel.canonical import with_claims  # noqa: E402
+from arborist.selfmodel.store import claims_for, latest  # noqa: E402
+from arborist.store import connect, transaction  # noqa: E402
+from arborist.substrate.fork_score import SIGNAL_FLOOR, _BATTERY_RATE_KEYS  # noqa: E402
+
+_FIX = _REPO_ROOT / "bench" / "fixtures"
+
+# Canonical sub-battery → embedded fixture pack (the keys fork_score
+# reads). Mirrors bench.batteries.runner._DEFAULT_FIXTURES minus the
+# legacy 5t "transfer" the scorer ignores.
+_PACKS: list[tuple[str, str, Path]] = [
+    ("5s", "syntax", _FIX / "5s" / "syntax-v1.jsonl"),
+    ("5s", "semantics", _FIX / "5s" / "semantics-v1.jsonl"),
+    ("5s", "syllogism", _FIX / "5s" / "syllogism-v1.jsonl"),
+    ("5s", "synthesis", _FIX / "5s" / "synthesis-v1.jsonl"),
+    ("5s", "semiotics", _FIX / "5s" / "semiotics-v1.jsonl"),
+    ("5t", "transfer-learning", _FIX / "5t" / "transfer-learning-v2.jsonl"),
+    ("5t", "triangulation", _FIX / "5t" / "triangulation-v1.jsonl"),
+    ("5t", "truthtables", _FIX / "5t" / "truthtables-v1.jsonl"),
+    ("5t", "transitivity", _FIX / "5t" / "transitivity-v1.jsonl"),
+    ("5t", "time", _FIX / "5t" / "time-v1.jsonl"),
+    ("5f", "function", _FIX / "5f" / "function-v1.jsonl"),
+    ("5f", "finetuning", _FIX / "5f" / "finetuning-v1.jsonl"),
+    ("5f", "falsification", _FIX / "5f" / "falsification-v1.jsonl"),
+    ("5f", "formulate", _FIX / "5f" / "formulate-v1.jsonl"),
+    ("5f", "feedback-loop", _FIX / "5f" / "feedback-loop-v1.jsonl"),
+]
+
+_SUB_RUNNERS = {"5s": b_5s.SUB_BATTERIES, "5t": b_5t.SUB_BATTERIES, "5f": b_5f.SUB_BATTERIES}
+
+
+def default_shard() -> Path:
+    env = os.environ.get("ARBORIST_SELFMODEL_CHAIN_DB")
+    if env:
+        return Path(env).expanduser()
+    return Path.home() / ".arborist" / "shards" / "selfmodel-chain.db"
+
+
+def _battery_claims(measured_at: int) -> list[CapabilityClaim]:
+    claims: list[CapabilityClaim] = []
+    for battery, sub, path in _PACKS:
+        res = _SUB_RUNNERS[battery][sub](path)
+        metric_key = _BATTERY_RATE_KEYS[battery][sub]
+        rate = float(res.metrics.get(metric_key, 0.0))
+        claims.append(
+            CapabilityClaim(
+                metric=f"{battery.upper()}-{sub}",
+                threshold=float(SIGNAL_FLOOR),
+                eval_digest=res.fixture_digest,
+                measured_value=rate,
+                measured_at=measured_at,
+                validity_horizon="next-checkpoint",
+                claim_text=f"{battery.upper()} {sub} {metric_key} on the embedded pack",
+            )
+        )
+    return claims
+
+
+def append_snapshot(shard: Path, *, ts: int | None = None) -> dict:
+    """Run the suite, append one chained SelfModel snapshot, return a
+    summary dict ``{root, parent_root, depth, claims: [...]}``."""
+    if ts is None:
+        ts = int(time.time())
+    shard.parent.mkdir(parents=True, exist_ok=True)
+    conn = connect(shard)
+    try:
+        prev = latest(conn)
+        claims = _battery_claims(ts)
+        with transaction(conn):
+            sm = with_claims(snapshot(conn), claims)
+            root = store_snapshot(conn, sm, claims=claims, ts=ts)
+        # Walk the parent chain to report depth.
+        depth = 1
+        cur = load_parent(conn, root)
+        while cur is not None:
+            depth += 1
+            cur = load_parent(conn, cur)
+        rows = claims_for(conn, root)
+        return {
+            "shard": str(shard),
+            "root": root,
+            "parent_root": prev["selfmodel_root"] if prev else None,
+            "depth": depth,
+            "claims": {r["metric"]: r["measured_value"] for r in rows},
+        }
+    finally:
+        conn.close()
+
+
+def load_parent(conn, root: str) -> str | None:
+    row = conn.execute(
+        "SELECT parent_selfmodel_root FROM selfmodel_records WHERE selfmodel_root = ?",
+        (root,),
+    ).fetchone()
+    if row is None:
+        return None
+    return row["parent_selfmodel_root"]
+
+
+def main(argv: list[str] | None = None) -> int:
+    p = argparse.ArgumentParser(description=__doc__.splitlines()[0])
+    p.add_argument(
+        "--shard",
+        type=Path,
+        default=None,
+        help="Chain shard path (default: $ARBORIST_SELFMODEL_CHAIN_DB or ~/.arborist/shards/selfmodel-chain.db)",
+    )
+    args = p.parse_args(argv)
+    shard = args.shard.expanduser() if args.shard else default_shard()
+    summary = append_snapshot(shard)
+    import json as _json
+
+    print(_json.dumps(summary, indent=2, default=str))
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/docs/TICKETS.md b/docs/TICKETS.md
index 413f5c3..79d810b 100644
--- a/docs/TICKETS.md
+++ b/docs/TICKETS.md
@@ -112,7 +112,7 @@ Newest first. Update on every open/close.
 | #000028  | Multi-modality witness for canonical shapes    | closed · landed 2026-05-09 + follow-ups (capital ledger · sample rate) | 2026-05-08 | —         |
 | #000027  | Canonical projections persist to providence_cache | closed · landed 2026-05-09 | 2026-05-08 | —         |
 | #000026  | Real-shard workload baseline + search latency  | closed · Phase 1 + 2 + 3 landed 2026-05-09 (Phase 3 in `60b5748`) | 2026-05-08 | —         |
-| #000025  | 5F battery (Function · Finetuning · Falsification · Formulate · Feedback Loop) | in progress · Phase 1a + 1b.2 + 1c + 1d landed 2026-05-09; Phase 1e (motif coverage, §10.12 closed) landed 2026-05-10 | 2026-05-07 | —         |
+| #000025  | 5F battery (Function · Finetuning · Falsification · Formulate · Feedback Loop) | closed · 2026-05-11 — Phase 1a–1f landed 2026-05-09/10; Phase 1g (§10.13 feedback latency + persisted-footprint efficiency), 1h (§10.14 ForkScore threshold-calibration handoff → #000012 §8), 1i (§10.11 persistent SelfModel-chain lineage: `bench-5f-selfmodel-snapshot` grows the chain, `run_finetuning` shard-chain mode reads the 2 latest snapshots) all landed 2026-05-11. Every §10 closure criterion met | 2026-05-07 | —         |
 | #000024  | 5T Phase 1b + Dav1DPrometheus vocabulary alignment | closed · landed 2026-05-08 | 2026-05-07 | —         |
 | #000023  | 5S Phase 1b: Syllogism · Synthesis · Semiotics | closed · landed 2026-05-08 | 2026-05-07 | —         |
 | #000022  | Adapter LossReport (PRD I9 analogue)           | closed · landed 2026-05-07 | 2026-05-07 | —         |
diff --git a/docs/tickets/ticket-000012-selection-consensus-protocol.md b/docs/tickets/ticket-000012-selection-consensus-protocol.md
index 9fe1764..bc0c047 100644
--- a/docs/tickets/ticket-000012-selection-consensus-protocol.md
+++ b/docs/tickets/ticket-000012-selection-consensus-protocol.md
@@ -506,3 +506,64 @@ its own ticket. Until then, #000037 Trigger 1 simply reports "no
 data — Phase 1c not landed" and the controller's multi-branch path
 is paper-only. That matches §12's "measured trigger, not calendar
 date" discipline.
+
+---
+
+## 8. ForkScore threshold calibration handoff (from #000025 §10.14)
+
+Ticket #000025 §10.14 ("threshold calibration for v8 selection
+acceptance handed off to #000012") landed 2026-05-11. Deliverable:
+`bench/scripts/fivef_threshold_calibration.py` →
+`bench/results/5f-threshold-calibration-2026-05-11.md`
+(regenerate via `make bench-5f-threshold-calibration`). It runs the
+canonical 5S/5T/5F packs (the ones `fork_score._BATTERY_RATE_KEYS`
+reads) plus the 5F live packs and reports baseline rates,
+observability granularity (1/n), and `fork_score` verdicts on the
+parent vs synthetic child perturbations. Findings the v8 acceptance
+protocol must account for:
+
+1. **Floor constants stay at 0.05.** `SIGNAL_FLOOR = 0.05` and
+   `HARD_REGRESSION_FLOOR = 0.05` match `docs/bench-maxing.md`'s
+   5-pp signal floor; the synthetic sanity checks (identity →
+   MARGINAL; degraded-parent → uniform-recovery → ACCEPT;
+   single-sub regression → REJECT) all behave as the docstrings
+   claim. The calibration ships **no constant change** — if a
+   future revision moves a floor, this ticket owns that edit, and
+   it does **not** fold into `governance_policy_hash` (ForkScore
+   constants are estimator parameters pinned by
+   `ESTIMATOR_VERSION`, not governance-policy inputs).
+
+2. **Pack granularity vs the floors (load-bearing).** The
+   foundational 5S packs are *coarser* than `HARD_REGRESSION_FLOOR`:
+   `syntax` n=10 → 10.0 pp/fixture, `semantics` n=8 → 12.5
+   pp/fixture. On those packs a single fixture flip is ≥ 5 pp, so
+   *any* regression on syntax/semantics trips the hard-reject —
+   intended zero-tolerance on the base, not a bug, but the v8
+   protocol should state it: on the small packs
+   `HARD_REGRESSION_FLOOR` is effectively "one fixture", not a
+   tunable knob. The n=30 / n=50 / n=62 packs run 3.3 / 2.0 / 1.6
+   pp per fixture, so there 5 pp ≈ 1.5–3 fixture flips.
+
+3. **5× averaging dilution.** `_delta_5{s,t,f}` *means* over the 5
+   sub-batteries of a battery, so a single sub-battery's rate gain
+   contributes a fifth of its face value. "A fork must improve by
+   `SIGNAL_FLOOR`" therefore means one of: ≈ 0.25 on a single
+   sub-battery, ≈ 0.05 uniform across one battery's 5 subs, or
+   ≈ 0.017 uniform across the whole 15-sub suite. Each battery
+   contributes a separate Δ-term at weight 1.0, so a uniform
+   +`SIGNAL_FLOOR` across every sub of all three batteries scores
+   ≈ 0.15. If v8 wants single-sub improvements to weigh equally,
+   switch `_delta_*` from mean to a max/sum aggregator — a design
+   call this ticket owns, not a calibration finding.
+
+4. **Ceiling saturation.** Every 5S/5T/5F pack is at rate 1.0 at
+   HEAD, so `α·Δ5s + β·Δ5t + γ·Δ5f` can only be ≤ 0 — an unchanged
+   child scores 0 → MARGINAL (not ACCEPT). Until a harder fixture
+   tier (or a deliberately-degraded parent baseline) drops a pack
+   below ceiling, fork *acceptance* at the current pack difficulty
+   is carried by the efficiency bonuses (`adaptation_efficiency` /
+   `feedback_efficiency`) + the non-bench terms
+   (`selfmodel_calibration_gain`, `audit_completeness`,
+   `validator_diversity`, …), not by bench Δ-rate. Adding the
+   harder tier is tracked as a #000025 follow-up, not a #000012
+   blocker.
diff --git a/docs/tickets/ticket-000025-5f-battery.md b/docs/tickets/ticket-000025-5f-battery.md
index efef499..fb8c9a7 100644
--- a/docs/tickets/ticket-000025-5f-battery.md
+++ b/docs/tickets/ticket-000025-5f-battery.md
@@ -1,6 +1,6 @@
 # Ticket #000025 — 5F battery: Function · Finetuning · Falsification · Formulate · Feedback Loop
 
-**Status:** in progress · Phase 1a + 1b.2 + 1c + 1d + 1e (motif coverage, 2026-05-10) landed; §10.11 (real shard finetuning chains), §10.13 (Feedback Loop latency/efficiency calibrated to real workload), §10.14 (threshold handoff to #000012) still open
+**Status:** closed · 2026-05-11 — Phase 1a + 1b.2 + 1c + 1d + 1e + 1f all landed; §10.11 (real shard finetuning chains — persistent SelfModel-chain lineage), §10.13 (Feedback Loop latency + persisted-footprint efficiency on real workload), §10.14 (ForkScore threshold-calibration handoff to #000012) all landed 2026-05-11. Every §10 closure criterion met
 **Opened:** 2026-05-07
 **Revised:** 2026-05-08 (cross-modality + state-space synthesis
 folded in per review response)
@@ -361,8 +361,21 @@ feedback_efficiency = downstream_effect_count / capital_cost_delta
 
 `feedback_efficiency` again hooks the capital ledger (#000020).
 Same zero-cost-guard semantics as `adaptation_efficiency` — see the
-:func:`_efficiency` helper. Phase 1a uses chain length as the
-cost-proxy; Phase 1b.2 reads from the capital_ledger directly.
+:func:`_efficiency` helper. Phase 1a used chain length (count of
+*requested* ops) as the cost-proxy. **§10.13 (2026-05-11)** replaced
+that for live chains with the *persisted footprint* —
+:func:`bench.batteries.b_5f._persisted_cost` = the audit-event rows
+the chain actually wrote + their body bytes / 1e6 (matching
+`_capital_cost_delta`'s 1 MB = 1 unit convention) — and finally
+implemented `feedback_latency` (listed above since Phase 1a, never
+computed): wall-clock seconds to apply a live chain against its temp
+shard, surfaced as per-task `feedback_latency_seconds` + battery
+`feedback_latency_mean_seconds` (0.0 when a pack has no live tasks)
++ `feedback_live_task_count`. Latency is a wall-clock field
+(run-to-run variable, like `BatteryResult.timestamp`) and is **not**
+a `fork_score` input — it's for operational observability + the
+#000020 ledger. Embedded chains keep `len(chain)` as cost and report
+`feedback_latency_seconds = None`.
 
 **Phase 1a uses existing surfaces only:** `memory_records`,
 `memory_branch_summaries`, `audit_events`. No new substrate work.
@@ -578,7 +591,7 @@ against real workload), §10.14 (threshold handoff to #000012).
 
 ## 11. Status
 
-**As of 2026-05-10: in progress.**
+**As of 2026-05-11: closed — all §10 closure criteria met.**
 
 - **Phase 1a** (Function + Finetuning seed): landed.
 - **Phase 1b.2** (Falsification curated fixtures): landed.
@@ -608,11 +621,72 @@ against real workload), §10.14 (threshold handoff to #000012).
   `audit_mode_at_harvest`, `harvest_threshold`, and
   `source_ticket: "#000037 §13 step 11"` for full traceability.
   Regenerate via `make bench-5f-harvest`.
+- **Phase 1g** (§10.13 — Feedback Loop latency / real-workload
+  efficiency): landed 2026-05-11. `run_feedback_loop` now computes
+  `feedback_latency` (listed in §5.5 since Phase 1a, never
+  implemented) — wall-clock seconds to apply a live chain against its
+  temp shard, surfaced per-task (`feedback_latency_seconds`) +
+  battery (`feedback_latency_mean_seconds`, `feedback_live_task_count`).
+  For live chains `feedback_efficiency`'s cost denominator switched
+  from `len(chain)` (count of *requested* ops) to the *persisted
+  footprint* `_persisted_cost` = audit-event rows the chain actually
+  wrote + their body bytes / 1e6. Embedded chains keep `len(chain)`
+  and report `feedback_latency_seconds = None`. Latency is a
+  wall-clock field (run-to-run variable, like
+  `BatteryResult.timestamp`) and is **not** a `fork_score` input.
+  Tests: 3 new in `tests/test_bench_batteries.py`
+  (`_persisted_cost` helper; embedded reports no latency; live
+  reports latency + persisted cost + the `efficiency = 1/cost`
+  identity).
+- **Phase 1h** (§10.14 — ForkScore threshold-calibration handoff to
+  #000012): landed 2026-05-11. `bench/scripts/fivef_threshold_calibration.py`
+  (run via `make bench-5f-threshold-calibration`) runs the canonical
+  5S/5T/5F packs + the 5F live packs and reports baseline rates,
+  observability granularity (1/n), and `fork_score` verdicts on the
+  parent vs synthetic perturbations →
+  `bench/results/5f-threshold-calibration-2026-05-11.md`. Findings
+  written into #000012 §8: keep `SIGNAL_FLOOR` / `HARD_REGRESSION_FLOOR`
+  at 0.05; the small 5S packs (`syntax` n=10, `semantics` n=8) are
+  *coarser* than the floors so any regression there trips hard-reject
+  (intended zero-tolerance); the 5× averaging dilution in `_delta_*`;
+  ceiling saturation (every pack at 1.0 → Δ-rate terms ≤ 0, so fork
+  *acceptance* is carried by the efficiency bonuses + non-bench
+  terms until a harder fixture tier lands). No constant change
+  shipped — that's #000012's call. Tests: 6 in
+  `tests/test_fivef_threshold_calibration.py`.
+- **Phase 1i** (§10.11 — real shard finetuning chains): landed
+  2026-05-11. `bench/scripts/selfmodel_chain_snapshot.py`
+  (`make bench-5f-selfmodel-snapshot`) appends ONE chained SelfModel
+  snapshot per run to a persistent shard
+  (`~/.arborist/shards/selfmodel-chain.db`, override via
+  `ARBORIST_SELFMODEL_CHAIN_DB`) with one `CapabilityClaim` per
+  sub-battery (`metric = "5S-syntax"` etc., `measured_value` = that
+  pack's rate, `eval_digest` = the pack's fixture digest, `threshold`
+  = `fork_score.SIGNAL_FLOOR`). `snapshot()` auto-parents, so the
+  distinct parent makes each snapshot a distinct root and the
+  lineage grows by one per run. `run_finetuning` gains a third
+  dispatch mode — **shard-chain** (gated on a task's `selfmodel_shard`
+  key) — via `_chain_finetuning_measure`: reads the two most-recent
+  snapshots (`latest()` = child, its `parent_selfmodel_root` =
+  parent) and measures improvement on `target_capability` between
+  them. This is the real lineage replacing Phase-1a's synthetic
+  parent→child pairs; the chained Δ reflects genuine cross-run drift
+  (0.0 today — the embedded packs are at ceiling). Operator pack
+  `bench/fixtures/5f/finetuning-shardchain-v1.jsonl` (6 tasks) +
+  `make bench-5f-finetuning-shardchain`; NOT in `make bench-5f`,
+  `make test`, or a fresh checkout (a missing/too-short chain fails
+  honestly). The real chain shard was bootstrapped 2-deep on
+  2026-05-11; `make chain-check-shards` reports 0 breaks on it.
+  Tests: 10 in `tests/test_selfmodel_chain.py`.
 
-**Still open** (carried in file header):
-- §10.11 — real shard finetuning chains
-- §10.13 — Feedback Loop latency/efficiency calibrated to real workload
-- §10.14 — threshold handoff to #000012
+**All §10 closure criteria met (2026-05-11).** §10 Phase 1a criteria
+1–9 + Phase 1b criteria 10–14 are satisfied:
+- 10 (30–50 fixtures per sub-battery): 5F embedded packs at 50 each
+  (62 for falsification per Phase 1e).
+- 11 (real shard finetuning chains): Phase 1i above.
+- 12 (motif coverage): Phase 1e.
+- 13 (Feedback Loop latency/efficiency on real workload): Phase 1g.
+- 14 (threshold calibration handed to #000012): Phase 1h.
 
 Larger surface than #000023 / #000024 (five sub-batteries vs three / four).
 
diff --git a/tests/test_bench_batteries.py b/tests/test_bench_batteries.py
index 6ac4291..544d7d1 100644
--- a/tests/test_bench_batteries.py
+++ b/tests/test_bench_batteries.py
@@ -547,6 +547,55 @@ def test_5f_live_feedback_chain_audit_chain_intact():
             pass
 
 
+# --- 5F §10.13 — feedback latency / real-workload efficiency --------
+
+
+def test_5f_persisted_cost_helper():
+    """_persisted_cost = audit-row count + body bytes / 1e6 (the real
+    footprint a live chain wrote, not the count of requested ops)."""
+    from bench.batteries.b_5f import _persisted_cost
+
+    assert _persisted_cost({}) == 0.0
+    state = {
+        "audit_event_types": ["a", "b", "c"],
+        "audit_event_bodies": ['{"x":1}', '{"y":2}', ""],  # 7 + 7 + 0 bytes
+    }
+    assert _persisted_cost(state) == pytest.approx(3.0 + 14 / 1e6)
+
+
+def test_5f_feedback_loop_embedded_reports_no_latency():
+    res = b_5f.run_feedback_loop(F5F / "feedback-loop-v1.jsonl")
+    assert res.metrics["feedback_latency_mean_seconds"] == 0.0
+    assert res.metrics["feedback_live_task_count"] == 0.0
+    for t in res.per_task:
+        assert t.detail.get("feedback_latency_seconds") is None
+        # Embedded cost-proxy stays len(chain) → integer-ratio efficiency.
+        assert "persisted_cost" not in t.detail
+
+
+def test_5f_feedback_loop_live_reports_latency_and_persisted_cost():
+    res = b_5f.run_feedback_loop(F5F / "feedback-loop-live-v1.jsonl")
+    assert res.metrics["feedback_live_task_count"] == 50.0  # Phase 1d
+    assert res.metrics["feedback_latency_mean_seconds"] > 0.0
+    for t in res.per_task:
+        if not t.passed:
+            continue
+        lat = t.detail["feedback_latency_seconds"]
+        assert isinstance(lat, float) and lat >= 0.0
+        # Real footprint: every live chain has >= 1 append_audit op.
+        assert t.detail["persisted_audit_rows"] >= 1
+        assert t.detail["persisted_cost"] >= 1.0
+        # feedback_efficiency now = downstream_effect / persisted_cost,
+        # not / len(chain). downstream_effect is 1.0 when the chain
+        # integrated, else 0.0 (an expected-"fail" task still passes).
+        if t.detail["integrated"]:
+            assert t.detail["feedback_efficiency"] == pytest.approx(
+                1.0 / t.detail["persisted_cost"]
+            )
+        else:
+            assert t.detail["feedback_efficiency"] == 0.0
+
+
 # --- 5F Phase 1b.2 — Function / Finetuning / Falsification live -
 
 
diff --git a/tests/test_fivef_threshold_calibration.py b/tests/test_fivef_threshold_calibration.py
new file mode 100644
index 0000000..5f66883
--- /dev/null
+++ b/tests/test_fivef_threshold_calibration.py
@@ -0,0 +1,86 @@
+"""Tests for the #000025 §10.14 ForkScore threshold-calibration handoff
+script (``bench/scripts/fivef_threshold_calibration.py``).
+
+The script is pure measurement over the canonical 5S/5T/5F packs +
+`fork_score`, so its markdown report is deterministic given fixed
+fixtures + code. These tests pin the structural anchors and the
+floor-constant sanity verdicts so the handoff doesn't drift silently.
+
+The live 5F packs (``*-live-v1.jsonl``) spin up temp shards and add
+~15s per run; the calibration *logic* (granularity, fork-score sanity)
+doesn't depend on them, so the tests stub ``_LIVE_PACKS`` to empty.
+The live runners are exercised by ``tests/test_bench_batteries.py``
+and ``make bench-5f-live``.
+"""
+from __future__ import annotations
+
+import pytest
+
+from bench.scripts import fivef_threshold_calibration as calib
+
+
+@pytest.fixture(scope="module", autouse=True)
+def _no_live_packs():
+    saved = calib._LIVE_PACKS
+    calib._LIVE_PACKS = {}
+    try:
+        yield
+    finally:
+        calib._LIVE_PACKS = saved
+
+
+@pytest.fixture(scope="module")
+def report() -> str:
+    return calib.build_report()
+
+
+def test_report_is_deterministic():
+    a = calib.build_report()
+    b = calib.build_report()
+
+    def _strip_ts(s: str) -> str:
+        return "\n".join(ln for ln in s.splitlines() if not ln.startswith("**Date:**"))
+
+    assert _strip_ts(a) == _strip_ts(b)
+
+
+def test_report_has_structural_anchors(report: str):
+    assert report.startswith("# 5S/5T/5F → v8 ForkScore threshold-calibration handoff")
+    assert "#000025 §10.14" in report
+    assert "## 1. Baseline rates + granularity" in report
+    assert "## 2. Identity-fork verdict (no change)" in report
+    assert "## 3. Floor-constant sanity checks" in report
+    assert "## 4. Recommendation for #000012" in report
+    for sub in (
+        "syntax", "semantics", "syllogism", "synthesis", "semiotics",
+        "transfer-learning", "triangulation", "truthtables", "transitivity", "time",
+        "function", "finetuning", "falsification", "formulate", "feedback-loop",
+    ):
+        assert f"| {sub} |" in report
+
+
+def test_identity_fork_is_marginal(report: str):
+    # Packs are at ceiling at HEAD → every Δ-rate term is 0 → MARGINAL.
+    assert "`fork_score(parent, parent)` → **MARGINAL (score +0.0000)**" in report
+
+
+def test_floor_sanity_verdicts_present(report: str):
+    assert "child recovers **all 5** 5F subs by +0.06 | ACCEPT" in report
+    assert "child recovers **only 1** 5F sub by +0.06 | MARGINAL" in report
+    assert "child drops one 5F sub by −0.05 | REJECT" in report
+    assert "REGRESSION_5F:5f/falsification" in report
+
+
+def test_recommendation_keeps_floors_and_flags_dilution(report: str):
+    assert "Keep `SIGNAL_FLOOR = 0.05` and `HARD_REGRESSION_FLOOR = 0.05`" in report
+    assert "5× averaging dilution" in report
+    assert "Ceiling saturation" in report
+    assert "No constant change shipped" in report
+
+
+def test_cli_main_writes_report(tmp_path):
+    out = tmp_path / "calib.md"
+    rc = calib.main(["--out", str(out)])
+    assert rc == 0
+    text = out.read_text(encoding="utf-8")
+    assert text.startswith("# 5S/5T/5F → v8 ForkScore threshold-calibration handoff")
diff --git a/tests/test_selfmodel_chain.py b/tests/test_selfmodel_chain.py
new file mode 100644
index 0000000..8722708
--- /dev/null
+++ b/tests/test_selfmodel_chain.py
@@ -0,0 +1,134 @@
+"""Tests for the #000025 §10.11 SelfModel snapshot-chain — the
+persistent lineage that replaces Phase-1a's synthetic parent→child
+pairs in the Finetuning sub-battery.
+
+Two surfaces:
+  - ``bench/scripts/selfmodel_chain_snapshot.py`` — the bootstrapper
+    that appends one chained snapshot per run (capability claims =
+    the 5S/5T/5F battery rates).
+  - ``bench.batteries.b_5f._chain_finetuning_measure`` + the
+    ``run_finetuning`` "shard-chain" dispatch — reads the two latest
+    snapshots and measures improvement on ``target_capability``.
+
+All against temp shards (``tmp_path`` / ``tmp_path_factory``) — never
+the real ``~/.arborist/shards/selfmodel-chain.db``.
+"""
+from __future__ import annotations
+
+from pathlib import Path
+
+import pytest
+
+from bench.batteries import b_5f
+from bench.scripts.selfmodel_chain_snapshot import append_snapshot
+
+_F5F = Path(__file__).parent.parent / "bench" / "fixtures" / "5f"
+_SHARDCHAIN_PACK = _F5F / "finetuning-shardchain-v1.jsonl"
+
+
+@pytest.fixture(scope="module")
+def chain_shard(tmp_path_factory) -> Path:
+    """A persistent 2-deep SelfModel chain on a temp shard."""
+    shard = tmp_path_factory.mktemp("smchain") / "chain.db"
+    s1 = append_snapshot(shard, ts=1_700_000_000)
+    s2 = append_snapshot(shard, ts=1_700_000_001)
+    assert s1["depth"] == 1 and s1["parent_root"] is None
+    assert s2["depth"] == 2 and s2["parent_root"] == s1["root"]
+    return shard
+
+
+# ---- bootstrapper -------------------------------------------------------
+
+
+def test_bootstrapper_grows_chain_one_per_run(tmp_path):
+    shard = tmp_path / "c.db"
+    a = append_snapshot(shard, ts=1_700_000_000)
+    assert a["depth"] == 1
+    assert a["parent_root"] is None
+    # 15 canonical sub-batteries → 15 capability claims.
+    assert len(a["claims"]) == 15
+    assert all(v == 1.0 for v in a["claims"].values())  # packs at ceiling
+    b = append_snapshot(shard, ts=1_700_000_001)
+    assert b["depth"] == 2
+    assert b["parent_root"] == a["root"]
+    assert b["root"] != a["root"]  # distinct parent ⇒ distinct root
+
+
+def test_bootstrapper_claims_carry_real_metric_names(chain_shard: Path):
+    a = append_snapshot(chain_shard, ts=1_700_000_002)  # depth 3
+    assert a["depth"] == 3
+    assert {"5S-syntax", "5T-time", "5F-feedback-loop"} <= set(a["claims"])
+
+
+# ---- _chain_finetuning_measure -----------------------------------------
+
+
+def test_chain_measure_reads_two_latest(chain_shard: Path):
+    out = b_5f._chain_finetuning_measure(
+        {"target_capability": "5F-feedback-loop", "selfmodel_shard": str(chain_shard)}
+    )
+    assert out["parent_measured"] == 1.0
+    assert out["child_measured"] == 1.0
+    assert out["parent_root"] != out["child_root"]
+
+
+def test_chain_measure_env_var_overrides_fixture(chain_shard: Path, monkeypatch):
+    monkeypatch.setenv("ARBORIST_SELFMODEL_CHAIN_DB", str(chain_shard))
+    out = b_5f._chain_finetuning_measure(
+        {"target_capability": "5S-syntax", "selfmodel_shard": "/nonexistent/ignored.db"}
+    )
+    assert out["child_measured"] == 1.0
+
+
+def test_chain_measure_absent_shard_raises(tmp_path):
+    with pytest.raises(FileNotFoundError, match="chain shard not found"):
+        b_5f._chain_finetuning_measure(
+            {"target_capability": "5S-syntax", "selfmodel_shard": str(tmp_path / "nope.db")}
+        )
+
+
+def test_chain_measure_single_snapshot_raises(tmp_path):
+    shard = tmp_path / "one.db"
+    append_snapshot(shard, ts=1_700_000_000)  # depth 1
+    with pytest.raises(ValueError, match="only one snapshot"):
+        b_5f._chain_finetuning_measure(
+            {"target_capability": "5S-syntax", "selfmodel_shard": str(shard)}
+        )
+
+
+def test_chain_measure_unknown_metric_raises(chain_shard: Path):
+    with pytest.raises(ValueError, match="no claim for"):
+        b_5f._chain_finetuning_measure(
+            {"target_capability": "NOT-A-REAL-METRIC", "selfmodel_shard": str(chain_shard)}
+        )
+
+
+# ---- run_finetuning shard-chain dispatch -------------------------------
+
+
+def test_run_finetuning_shardchain_pack_passes(chain_shard: Path, monkeypatch):
+    monkeypatch.setenv("ARBORIST_SELFMODEL_CHAIN_DB", str(chain_shard))
+    res = b_5f.run_finetuning(_SHARDCHAIN_PACK)
+    assert res.pass_count == 6
+    assert res.fail_count == 0
+    for t in res.per_task:
+        assert t.detail["source"] == "shard-chain"
+        assert t.detail["improvement"] == 0.0  # packs at ceiling ⇒ no drift
+        assert t.detail["chain_parent_root"] != t.detail["chain_child_root"]
+
+
+def test_run_finetuning_shardchain_pack_fails_honestly_without_chain(tmp_path, monkeypatch):
+    monkeypatch.setenv("ARBORIST_SELFMODEL_CHAIN_DB", str(tmp_path / "absent.db"))
+    res = b_5f.run_finetuning(_SHARDCHAIN_PACK)
+    assert res.pass_count == 0
+    assert res.fail_count == 6
+    assert "FileNotFoundError" in res.per_task[0].detail["reason"]
+
+
+def test_embedded_and_live_finetuning_unaffected():
+    """The shard-chain dispatch is gated on ``selfmodel_shard``; the
+    embedded + live packs still route through their original paths."""
+    emb = b_5f.run_finetuning(_F5F / "finetuning-v1.jsonl")
+    assert emb.pass_count == 50
+    for t in emb.per_task:
+        assert t.detail["source"] == "embedded"