diff --git a/benchmarks/unseen/bank.py b/benchmarks/unseen/bank.py
new file mode 100644
index 0000000..ec9cc6a
--- /dev/null
+++ b/benchmarks/unseen/bank.py
@@ -0,0 +1,160 @@
+"""Durable, content-addressed draw decisions; object I/O stays on the coordinator."""
+
+from __future__ import annotations
+
+import hashlib
+import json
+import os
+from collections.abc import Mapping
+from datetime import UTC, datetime
+from urllib.parse import urlencode, urlsplit
+
+CORPUS_KEYS = ("CORPUS_S3_ENDPOINT", "CORPUS_S3_BUCKET", "CORPUS_AWS_ACCESS_KEY_ID", "CORPUS_AWS_SECRET_ACCESS_KEY")
+
+
+def corpus_settings(environ: Mapping[str, str] | None = None) -> dict:
+    """Read corpus-only credentials, naming missing settings without exposing values."""
+    if environ is None:
+        from openultrasast.config import load_dotenv
+
+        load_dotenv()
+        environ = os.environ
+    missing = [key for key in CORPUS_KEYS if not environ.get(key)]
+    if missing:
+        raise ValueError(f"Corpus bank needs {', '.join(missing)} in .env or the environment")
+    endpoint = environ["CORPUS_S3_ENDPOINT"].strip()
+    try:
+        parsed = urlsplit(endpoint)
+        valid_endpoint = parsed.scheme in ("http", "https") and bool(parsed.netloc)
+    except ValueError:
+        valid_endpoint = False
+    if not valid_endpoint:
+        raise ValueError("CORPUS_S3_ENDPOINT must be a URL with a scheme (https://host[:port])")
+    settings = {
+        "endpoint": endpoint,
+        "bucket": environ["CORPUS_S3_BUCKET"],
+        "access_key": environ["CORPUS_AWS_ACCESS_KEY_ID"],
+        "secret_key": environ["CORPUS_AWS_SECRET_ACCESS_KEY"],
+    }
+    if environ.get("CORPUS_S3_REGION"):
+        settings["region"] = environ["CORPUS_S3_REGION"]
+    return settings
+
+
+class CorpusObjects:
+    """Plain S3 put/get/list, with no bucket administration or capability probes."""
+
+    def __init__(self, *, endpoint: str, bucket: str, access_key: str, secret_key: str, region: str | None = None):
+        import boto3
+        from botocore.config import Config
+
+        self.bucket = bucket
+        self.client = boto3.client(
+            "s3",
+            endpoint_url=endpoint,
+            aws_access_key_id=access_key,
+            aws_secret_access_key=secret_key,
+            region_name=region or "us-east-1",
+            # RustFS/MinIO at an IP endpoint needs path-style addressing
+            # (virtual-host bucket.<ip> does not resolve) and SigV4. Verified
+            # against ousast-corpus @ 10.0.0.54:9001.
+            config=Config(
+                signature_version="s3v4",
+                s3={"addressing_style": "path"},
+                retries={"total_max_attempts": 1},
+            ),
+        )
+
+    def get(self, key: str) -> tuple[bytes, str] | None:
+        try:
+            result = self.client.get_object(Bucket=self.bucket, Key=key)
+        except Exception as error:
+            if getattr(error, "response", {}).get("Error", {}).get("Code") in {"NoSuchKey", "404", "NotFound"}:
+                return None
+            raise
+        body = result["Body"]
+        try:
+            return body.read(), result.get("VersionId") or result.get("ETag", "")
+        finally:
+            body.close()
+
+    def put(self, key: str, data: bytes, labels: dict) -> None:
+        self.client.put_object(
+            Bucket=self.bucket,
+            Key=key,
+            Body=data,
+            ContentType="application/json",
+            Tagging=urlencode(labels),
+        )
+
+    def keys(self, prefix: str) -> list[str]:
+        pages = self.client.get_paginator("list_objects_v2").paginate(Bucket=self.bucket, Prefix=prefix)
+        return [item["Key"] for page in pages for item in page.get("Contents", [])]
+
+
+def _retry(operation, *args, **kwargs):
+    """Retry one object operation once; a second failure is fatal to durability."""
+    try:
+        return operation(*args, **kwargs)
+    except Exception:
+        return operation(*args, **kwargs)
+
+
+class CorpusBank:
+    def __init__(self, client, *, seed: int, prefix: str = "unseen"):
+        self.client = client
+        self.seed = seed
+        self.decisions_prefix = f"{prefix}/{seed}/decisions/"
+
+    @staticmethod
+    def key_for(repository: str, fix: str) -> str:
+        return hashlib.sha256(f"{repository}\n{fix}".encode()).hexdigest()
+
+    def bank(self, repository: str, fix: str, result: dict, *, contract: str) -> None:
+        decision = {
+            "repository": repository,
+            "fix": fix,
+            "decision": "accept" if "entry" in result else "reject",
+            "reason": result.get("rejected"),
+            "entry": result.get("entry"),
+            "ordinary_exclusions": result.get("ordinary_exclusions", {}),
+            "counts": result.get("counts", {}),
+            "contract": contract,
+            "seed": self.seed,
+        }
+        key = self.decisions_prefix + self.key_for(repository, fix) + ".json"
+        existing = _retry(self.client.get, key)
+        if existing is not None:
+            previous = json.loads(existing[0])
+            if {field: value for field, value in previous.items() if field != "ts"} == decision:
+                return  # Preserve the first timestamp and avoid an unnecessary object version.
+        decision["ts"] = datetime.now(UTC).isoformat()
+        data = json.dumps(decision, sort_keys=True, separators=(",", ":"), ensure_ascii=False).encode()
+        _retry(self.client.put, key, data, labels={"decision": decision["decision"], "contract": contract})
+
+    def decided(self) -> dict[str, dict]:
+        decisions = {}
+        for key in sorted(self.client.keys(self.decisions_prefix)):
+            stored = _retry(self.client.get, key)
+            if stored is None:
+                raise ValueError("corpus_decision_missing")
+            decision = json.loads(stored[0])
+            digest = self.key_for(decision["repository"], decision["fix"])
+            if key != self.decisions_prefix + digest + ".json" or decision["seed"] != self.seed:
+                raise ValueError("corpus_decision_identity")
+            if decision["decision"] not in {"accept", "reject"}:
+                raise ValueError("corpus_decision_invalid")
+            decisions[digest] = decision
+        return decisions
+
+
+def split_decided(decisions: Mapping[str, dict], *, contract: str) -> tuple[list[dict], set[str]]:
+    """Split reusable results, sorted independently of bucket listing order.
+
+    The coordinator merges entries into the full advisory population before seeded
+    ordering: shuffling only the accepted subset would change the draw's order.
+    """
+    accepted = [row["entry"] for row in decisions.values() if row["decision"] == "accept"]
+    accepted.sort(key=lambda entry: (entry.get("advisory", ""), entry["repository"], entry["fix"]))
+    reusable = {key for key, row in decisions.items() if row["decision"] == "accept" or row["contract"] == contract}
+    return accepted, reusable
diff --git a/benchmarks/unseen/draft.py b/benchmarks/unseen/draft.py
index 0770126..d90ea09 100644
--- a/benchmarks/unseen/draft.py
+++ b/benchmarks/unseen/draft.py
@@ -2,7 +2,7 @@
 
 All network and git operations are injected at the run() boundary. Only counts,
 digests and fixed failure codes go to stdout; identity-bearing output stays in the
-private journal outside the repository. No population guard is run here.
+private journal or corpus bucket. No population guard is run here.
 """
 
 from __future__ import annotations
@@ -20,12 +20,13 @@ import time
 from collections import Counter, defaultdict, deque
 from concurrent.futures import FIRST_COMPLETED, ProcessPoolExecutor, wait
 from concurrent.futures.process import BrokenProcessPool
-from contextlib import contextmanager
+from contextlib import ExitStack, contextmanager
 from dataclasses import asdict
 from pathlib import Path
 
 from . import eligibility, extract, source
-from .extract import Git, InstrumentFailure
+from .bank import CorpusBank, CorpusObjects, corpus_settings, split_decided
+from .extract import EXTRACTION_CONTRACT, Git, InstrumentFailure
 from .journal import Journal, ResolvedGitHub, ResumeMismatch, Stopped, atomic, digest, external
 
 
@@ -367,7 +368,21 @@ def finish_license(result, github):
 
 
 @contextmanager
-def ordered_extractions(rows, api, osv, used, clones, fixes, seed, checkpoint, entries, workers, pool_size):
+def ordered_extractions(
+    rows,
+    api,
+    osv,
+    used,
+    clones,
+    fixes,
+    seed,
+    checkpoint,
+    entries,
+    workers,
+    pool_size,
+    bank: CorpusBank | None = None,
+    decided=None,
+):
     """Bounded in-flight work, completion journaling, and seed-order acceptance.
 
     Only running jobs count against `workers`; completed results wait in the
@@ -376,6 +391,8 @@ def ordered_extractions(rows, api, osv, used, clones, fixes, seed, checkpoint, e
     Graceful STOP/guard/target exits drain started work into the journal for resume;
     a hard interrupt may lose unjournaled work but cannot change accepted order.
     """
+    decided = dict(decided or {})
+    identities = {}
     pending = deque()  # Seed-order acceptance cursor; contains no futures/results.
     in_flight = {}  # Future -> extraction key, independent of the cursor.
     # Fork shares the coordinator's memory copy-on-write. Jobs receive only the
@@ -383,8 +400,22 @@ def ordered_extractions(rows, api, osv, used, clones, fixes, seed, checkpoint, e
     context = multiprocessing.get_context("fork")
     pool = ProcessPoolExecutor(max_workers=workers, mp_context=context)
 
+    def remember(repository, fix, result):
+        bank.bank(repository, fix, result, contract=EXTRACTION_CONTRACT)
+        # Reuse decisions made during this invocation too: another advisory for
+        # the same pair must not overwrite an earlier accept with a rejection.
+        decided[bank.key_for(repository, fix)] = {
+            "repository": repository,
+            "fix": fix,
+            "decision": "accept" if "entry" in result else "reject",
+            "entry": result.get("entry"),
+            "reason": result.get("rejected"),
+            "ordinary_exclusions": result.get("ordinary_exclusions", {}),
+            "counts": result.get("counts", {}),
+        }
+
     def collect(future):
-        key = in_flight[future]
+        key = in_flight.pop(future)
         try:
             result = future.result()
         except BrokenProcessPool:
@@ -401,8 +432,10 @@ def ordered_extractions(rows, api, osv, used, clones, fixes, seed, checkpoint, e
             else:
                 clones.counts[name] += value
         result = finish_license(result, api)
+        if bank is not None:
+            repository, fix = identities[key]
+            remember(repository, fix, result)
         checkpoint.put("extraction", key, result)
-        del in_flight[future]
 
     def iterate():
         nonlocal pool
@@ -428,6 +461,53 @@ def ordered_extractions(rows, api, osv, used, clones, fixes, seed, checkpoint, e
                     exhausted = True
                     break
                 key = row["ghsa_id"]
+                identity = None
+                if bank is not None:
+                    links = source.fix_links(row)
+                    if len(links) == 1:
+                        repository, fix = next(iter(links))
+                        try:
+                            resolved = eligibility.resolve(repository, api)
+                            repository = resolved.full_name
+                        except eligibility.RepositoryNotFound:
+                            resolved = None
+                        except ValueError as exc:
+                            if str(exc) != "http_failure":
+                                raise
+                            resolved = None  # decide() records this as a resilient skip.
+                        identity = (repository, fix)
+                        saved = decided.get(bank.key_for(*identity))
+                        if saved is None and len(fix) < 40:
+                            matches = [
+                                value for value in decided.values() if value["repository"] == repository and value["fix"].startswith(fix)
+                            ]
+                            if len(matches) == 1:
+                                saved = matches[0]
+                                identity = (repository, saved["fix"])
+                        if saved is None:
+                            # A duplicate advisory can arrive before its pair's
+                            # worker finishes. Share that pending result as well.
+                            matching = [key for key, pair in identities.items() if pair[0] == repository and pair[1].startswith(fix)]
+                            if len(matching) == 1:
+                                pending.append((row, {"network": resolved.network if resolved else repository}, matching[0]))
+                                break
+                        if saved is not None:
+                            decision = {"network": resolved.network if resolved is not None else repository}
+                            blocked = eligibility.rejection(resolved, used, set()) if resolved is not None else None
+                            if blocked:
+                                decision["rejected"] = "used_" + blocked
+                                pending.append((row, decision, None))
+                            else:
+                                result = {"ordinary_exclusions": saved["ordinary_exclusions"], "counts": saved["counts"]}
+                                if saved["decision"] == "accept":
+                                    result["entry"] = saved["entry"]
+                                else:
+                                    result["rejected"] = saved["reason"]
+                                extraction_key = bank.key_for(*identity)
+                                if extraction_key not in checkpoint.rows["extraction"]:
+                                    checkpoint.put("extraction", extraction_key, result)
+                                pending.append((row, decision, extraction_key))
+                            break
                 if key not in checkpoint.rows["eligibility"]:
                     checkpoint.put("eligibility", key, decide(row, api, osv, used))
                 decision = checkpoint.rows["eligibility"][key]
@@ -435,7 +515,10 @@ def ordered_extractions(rows, api, osv, used, clones, fixes, seed, checkpoint, e
                 if "candidate" in decision:
                     candidate = source.Candidate(**decision["candidate"])
                     extraction_key = digest({"repository": candidate.repository, "advisory": key, "fix": candidate.fix})
-                    if extraction_key not in checkpoint.rows["extraction"]:
+                    if bank is not None:
+                        extraction_key = bank.key_for(candidate.repository, candidate.fix)
+                        identities[extraction_key] = (candidate.repository, candidate.fix)
+                    if extraction_key not in checkpoint.rows["extraction"] and extraction_key not in in_flight.values():
                         checkpoint.boundary()
                         local = copy.copy(clones)
                         local.counts = Counter()
@@ -449,6 +532,8 @@ def ordered_extractions(rows, api, osv, used, clones, fixes, seed, checkpoint, e
                             pool = ProcessPoolExecutor(max_workers=workers, mp_context=context)
                             future = pool.submit(extract_repository, *args)
                         in_flight[future] = extraction_key
+                elif bank is not None and identity is not None:
+                    remember(*identity, decision)
                 pending.append((row, decision, extraction_key))
                 # Finalize cached decisions promptly (especially on resume), and
                 # service completed jobs even during a long run of decide skips.
@@ -482,7 +567,7 @@ def ordered_extractions(rows, api, osv, used, clones, fixes, seed, checkpoint, e
                 checkpoint.progress("stopped", reason=stopped)
 
 
-def publish(journal, assigned, seed):
+def publish(journal, assigned, seed, *, destination=None):
     """Idempotent publication from completed journal data, never inside the checkout."""
     public, private = [], []
     for row in assigned:
@@ -492,7 +577,7 @@ def publish(journal, assigned, seed):
             private.append(row)
             public.append({"id": row["id"], "sha256": private_digest(row), "slice": row["slice"], "private": True})
     for name, rows in (("private-draft-p1.toml", private), ("draft-p1.toml", public)):
-        path = journal.path / name
+        path = (destination or journal.path) / name
         data = manifest(rows, seed).encode()
         if path.exists():
             if path.read_bytes() != data:
@@ -516,6 +601,7 @@ def run(
     extract_workers=None,
     pool_size=300,
     slices=3,
+    bank: CorpusBank | None = None,
 ) -> dict:
     validate_pool(pool_size, slices)
     workers = extract_workers if extract_workers is not None else getattr(clones, "extract_workers", 6)
@@ -530,13 +616,25 @@ def run(
     report["parse_deadline_seconds"] = getattr(clones, "parse_deadline_seconds", None)
     counts, rejected, ordinary_counts = Counter(), Counter(), Counter()
     checkpoint = None
+    scratch = ExitStack()
     try:
+        decided = bank.decided() if bank is not None else {}
+        accepted, reusable = split_decided(decided, contract=EXTRACTION_CONTRACT)
+        decided = {key: value for key, value in decided.items() if key in reusable}
         known_empty = set(known_empty or ())
         used.report(known_empty)
         cache = getattr(clones, "cache", root.parent / (root.name + "-cache"))
         path = external(root, journal_path or cache / "journal")
+        journal_directory = path
+        if bank is not None:
+            # Local records are a disposable cursor, never a cross-run authority.
+            path.mkdir(parents=True, exist_ok=True, mode=0o700)
+            journal_directory = Path(scratch.enter_context(tempfile.TemporaryDirectory(prefix="cursor-", dir=path)))
         checkpoint = Journal(
-            path, max_hours=max_hours, clock=clock, rate_limit=lambda: getattr(getattr(github, "transport", None), "rate_limit", {})
+            journal_directory,
+            max_hours=max_hours,
+            clock=clock,
+            rate_limit=lambda: getattr(getattr(github, "transport", None), "rate_limit", {}),
         )
         with checkpoint.open(inputs(used, seed, known_empty, clones, pool_size=pool_size, slices=slices)):
             checkpoint.boundary()
@@ -544,7 +642,26 @@ def run(
             used = copy.deepcopy(used)  # canonicalization must not mutate the resume input
             eligibility.canonicalize_used(used, api)
             report["used_set"] = used.report(known_empty)
-            rows = enumerate_advisories(api, checkpoint)
+            try:
+                rows = enumerate_advisories(api, checkpoint)
+            except InstrumentFailure as exc:
+                if str(exc) != "empty_advisories" or not accepted:
+                    raise
+                rows = []
+            if bank is not None:
+                # Retain accepted entries even if their advisory disappeared upstream.
+                present = {row["ghsa_id"] for row in rows}
+                for entry in accepted:
+                    if entry["advisory"] not in present:
+                        rows.append(
+                            {
+                                "ghsa_id": entry["advisory"],
+                                "published_at": "2026-06-02" if entry["post_cutoff"] else "2026-06-01",
+                                "vulnerabilities": [{"package": {"ecosystem": entry["ecosystem"]}}],
+                                "references": [f"https://github.com/{entry['repository']}/commit/{entry['fix']}"],
+                            }
+                        )
+                        present.add(entry["advisory"])
             report["advisories"] = len(rows)
             fixes_by_repo = advisory_index(rows, api)
             selected_networks, entries = set(), []
@@ -561,6 +678,8 @@ def run(
                 entries,
                 workers,
                 pool_size,
+                bank=bank,
+                decided=decided,
             ) as outcomes:
                 for row, decision, result in outcomes:
                     counts[source.ecosystem(row)] += 1
@@ -575,7 +694,9 @@ def run(
                         ordinary_counts.update(result["ordinary_exclusions"])
                         if "rejected" in result:
                             rejected[result["rejected"]] += 1
-                            instrument_failures += int(result["rejected"].startswith("extract_"))
+                            instrument_failures += int(
+                                result["rejected"].startswith("extract_") or result["rejected"] == "decide_http_failure"
+                            )
                         else:
                             selected_networks.add(decision["network"])
                             entries.append(result["entry"])
@@ -605,7 +726,7 @@ def run(
             elif checkpoint.rows["completion"]["all"] != completion:
                 raise ValueError("journal_completion_mismatch")
             checkpoint.boundary()
-            publish(checkpoint, assigned, seed)
+            publish(checkpoint, assigned, seed, destination=path if bank is not None else None)
             report.update(
                 {
                     "status": "draft",
@@ -629,6 +750,7 @@ def run(
         report.update({"status": "instrument_failure", "error_type": type(exc).__name__})
         return report
     finally:
+        scratch.close()
         report.update({"candidates": dict(counts), "rejections": dict(rejected), "ordinary_exclusions": dict(ordinary_counts)})
         report["instrument"] = dict(clones.counts)
         report["wall_seconds"] = round(time.monotonic() - started, 3)
@@ -658,6 +780,7 @@ def main(argv: list[str] | None = None) -> int:
     parser.add_argument("--pool-size", type=int, default=300, help="Repositories to accept (default: 300)")
     parser.add_argument("--slices", type=int, default=3, help="Equal-sized slices (default: 3)")
     parser.add_argument("--seed", type=int, default=20260601)
+    parser.add_argument("--bank", nargs="?", const="unseen", default="", help="Corpus bucket prefix; enables durable decisions")
     parser.add_argument("--local-store")
     parser.add_argument("--s3-store", default="s3://")
     parser.add_argument("--pointer-manifest", type=Path, action="append", default=[])
@@ -686,6 +809,7 @@ def main(argv: list[str] | None = None) -> int:
             "s3": memory.open_store(args.s3_store, read_only=True),
         }
         used = eligibility.build_used(args.root, stores=stores, pointer_manifests=args.pointer_manifest)
+        bank = CorpusBank(CorpusObjects(**corpus_settings()), seed=args.seed, prefix=args.bank) if args.bank else None
         report = run(
             args.root,
             github=source.GitHub(os.environ.get("GH_TOKEN", "")),
@@ -698,6 +822,7 @@ def main(argv: list[str] | None = None) -> int:
             known_empty=set(args.known_empty),
             journal_path=clones.cache / "journal",
             max_hours=args.max_hours,
+            bank=bank,
         )
     except Exception as exc:
         report = {"status": "instrument_failure", "error_type": type(exc).__name__}
diff --git a/benchmarks/unseen/extract.py b/benchmarks/unseen/extract.py
index 6b51800..7e16449 100644
--- a/benchmarks/unseen/extract.py
+++ b/benchmarks/unseen/extract.py
@@ -19,6 +19,9 @@ from pathlib import Path
 
 from .source import Candidate, Rejected
 
+# Bump only when accept/reject outcomes or accepted entry bytes change.
+EXTRACTION_CONTRACT = "v1"
+
 LANGUAGES = {".py", ".js", ".jsx", ".mjs", ".cjs", ".ts", ".tsx", ".php", ".java"}
 HUNK = re.compile(r"^@@ -(\d+)(?:,(\d+))? \+(\d+)(?:,(\d+))? @@", re.M)
 SHA = re.compile(r"[a-f0-9]{40}")
diff --git a/tests/test_unseen_bank.py b/tests/test_unseen_bank.py
new file mode 100644
index 0000000..13f9f02
--- /dev/null
+++ b/tests/test_unseen_bank.py
@@ -0,0 +1,216 @@
+"""Offline decision-bank contract: durability, identity and plain object transport."""
+
+import hashlib
+import io
+import json
+import sys
+from datetime import datetime
+from types import SimpleNamespace
+
+import pytest
+
+from benchmarks.unseen.bank import CorpusBank, CorpusObjects, corpus_settings, split_decided
+
+
+class FakeObjects:
+    def __init__(self):
+        self.objects = {}
+        self.labels = {}
+        self.calls = []
+        self.failures = {}
+
+    def call(self, operation):
+        self.calls.append(operation)
+        if self.failures.get(operation, 0):
+            self.failures[operation] -= 1
+            raise OSError("offline failure")
+
+    def get(self, key):
+        self.call("get")
+        return (self.objects[key], "version") if key in self.objects else None
+
+    def put(self, key, data, labels):
+        self.call("put")
+        self.objects[key] = data
+        self.labels[key] = labels
+
+    def keys(self, prefix):
+        return [key for key in reversed(self.objects) if key.startswith(prefix)]
+
+
+def settings_env():
+    return {
+        "CORPUS_S3_ENDPOINT": "https://objects.invalid",
+        "CORPUS_S3_BUCKET": "ousast-corpus",
+        "CORPUS_AWS_ACCESS_KEY_ID": "private-access",
+        "CORPUS_AWS_SECRET_ACCESS_KEY": "private-secret",
+    }
+
+
+@pytest.mark.parametrize("missing", list(settings_env()))
+def test_settings_names_missing_key_without_values(missing):
+    env = settings_env()
+    del env[missing]
+    with pytest.raises(ValueError) as error:
+        corpus_settings(env)
+    assert missing in str(error.value)
+    assert all(value not in str(error.value) for value in env.values())
+
+
+def test_settings_and_optional_region():
+    env = settings_env()
+    assert corpus_settings(env) == {
+        "endpoint": env["CORPUS_S3_ENDPOINT"],
+        "bucket": "ousast-corpus",
+        "access_key": "private-access",
+        "secret_key": "private-secret",
+    }
+    assert corpus_settings({**env, "CORPUS_S3_REGION": "region-1"})["region"] == "region-1"
+
+
+def test_bank_roundtrip_and_idempotent_bytes():
+    objects = FakeObjects()
+    bank = CorpusBank(objects, seed=42)
+    entry = {"repository": "org/a", "fix": "abc", "advisory": "GHSA-a", "changes": [{"code": "text"}]}
+    result = {"entry": entry, "ordinary_exclusions": {"merge": 2}, "counts": {"eligible": 13}}
+    key = bank.key_for("org/a", "abc")
+    assert key == hashlib.sha256(b"org/a\nabc").hexdigest()
+    bank.bank("org/a", "abc", result, contract="v1")
+    original = objects.objects.copy()
+    bank.bank("org/a", "abc", result, contract="v1")
+    assert objects.objects == original
+    assert list(objects.objects) == [f"unseen/42/decisions/{key}.json"]
+    row = bank.decided()[key]
+    assert row == {
+        "repository": "org/a",
+        "fix": "abc",
+        "decision": "accept",
+        "reason": None,
+        "entry": entry,
+        "ordinary_exclusions": {"merge": 2},
+        "counts": {"eligible": 13},
+        "contract": "v1",
+        "seed": 42,
+        "ts": row["ts"],
+    }
+    assert datetime.fromisoformat(row["ts"]).utcoffset().total_seconds() == 0
+    assert objects.labels[next(iter(objects.labels))] == {"decision": "accept", "contract": "v1"}
+
+
+def test_rejection_contract_update_and_split():
+    objects = FakeObjects()
+    bank = CorpusBank(objects, seed=3, prefix="custom")
+    for repo, advisory in (("z", "GHSA-z"), ("a", "GHSA-a")):
+        bank.bank(repo, "fix", {"entry": {"repository": repo, "fix": "fix", "advisory": advisory}}, contract="old")
+    bank.bank("no", "fix", {"rejected": "reason"}, contract="v1")
+    bank.bank("stale", "fix", {"rejected": "reason"}, contract="old")
+    accepted, keys = split_decided(bank.decided(), contract="v1")
+    assert [entry["repository"] for entry in accepted] == ["a", "z"]
+    assert keys == {bank.key_for(repo, "fix") for repo in ("a", "z", "no")}
+    row = bank.decided()[bank.key_for("no", "fix")]
+    assert row["reason"] == "reason" and row["decision"] == "reject"
+    assert row["entry"] is None and row["counts"] == row["ordinary_exclusions"] == {}
+    bank.bank("stale", "fix", {"rejected": "different"}, contract="v1")
+    assert len(objects.objects) == 4
+    assert bank.decided()[bank.key_for("stale", "fix")]["contract"] == "v1"
+
+
+@pytest.mark.parametrize("operation", ["get", "put"])
+@pytest.mark.parametrize("failures", [1, 2])
+def test_bank_retries_once_then_surfaces_failure(operation, failures):
+    objects = FakeObjects()
+    objects.failures[operation] = failures
+    bank = CorpusBank(objects, seed=1)
+    if failures == 1:
+        bank.bank("repo", "fix", {"rejected": "reason"}, contract="v1")
+        assert len(objects.objects) == 1
+    else:
+        with pytest.raises(OSError, match="offline failure"):
+            bank.bank("repo", "fix", {"rejected": "reason"}, contract="v1")
+    assert objects.calls.count(operation) == 2
+
+
+def test_decided_retries_get_and_fails_on_missing_listed_object():
+    objects = FakeObjects()
+    bank = CorpusBank(objects, seed=1)
+    bank.bank("repo", "fix", {"rejected": "reason"}, contract="v1")
+    objects.failures["get"] = 1
+    assert len(bank.decided()) == 1
+    objects.get = lambda key: None
+    with pytest.raises(ValueError, match="missing"):
+        bank.decided()
+
+
+def test_plain_s3_adapter_without_bucket_probes(monkeypatch):
+    calls = []
+
+    class Missing(Exception):
+        response = {"Error": {"Code": "NoSuchKey"}}
+
+    class S3:
+        def put_object(self, **kwargs):
+            calls.append(("put", kwargs))
+
+        def get_object(self, **kwargs):
+            calls.append(("get", kwargs))
+            if kwargs["Key"] == "missing":
+                raise Missing()
+            return {"Body": io.BytesIO(b"data"), "ETag": "tag"}
+
+        def get_paginator(self, name):
+            assert name == "list_objects_v2"
+            return SimpleNamespace(paginate=self.pages)
+
+        def pages(self, **kwargs):
+            calls.append(("list", kwargs))
+            return [{"Contents": [{"Key": "p/a"}]}, {}, {"Contents": [{"Key": "p/b"}]}]
+
+    def client(service, **kwargs):
+        calls.append((service, kwargs))
+        return S3()
+
+    monkeypatch.setitem(sys.modules, "boto3", SimpleNamespace(client=client))
+    monkeypatch.setitem(sys.modules, "botocore.config", SimpleNamespace(Config=lambda **kwargs: SimpleNamespace(**kwargs)))
+    adapter = CorpusObjects(**corpus_settings(settings_env()))
+    adapter.put("p/a", b"data", {"decision": "accept", "contract": "v1"})
+    assert adapter.get("p/a") == (b"data", "tag")
+    assert adapter.get("missing") is None
+    assert adapter.keys("p/") == ["p/a", "p/b"]
+    assert calls[0][0] == "s3"
+    assert calls[0][1]["endpoint_url"] == "https://objects.invalid"
+    assert calls[0][1]["config"].retries == {"total_max_attempts": 1}
+    assert calls[1][1]["Bucket"] == "ousast-corpus"
+    assert calls[1][1]["Body"] == b"data"
+    assert calls[-1] == ("list", {"Bucket": "ousast-corpus", "Prefix": "p/"})
+
+
+def test_decided_rejects_invalid_identity():
+    objects = FakeObjects()
+    bank = CorpusBank(objects, seed=1)
+    bank.bank("repo", "fix", {"rejected": "reason"}, contract="v1")
+    key = next(iter(objects.objects))
+    row = json.loads(objects.objects[key])
+    row["repository"] = "other"
+    objects.objects[key] = json.dumps(row).encode()
+    with pytest.raises(ValueError, match="identity"):
+        bank.decided()
+
+
+@pytest.mark.parametrize("endpoint", ["missing-scheme-private", "https://private[", "http://private／secret"])
+def test_invalid_endpoint_does_not_expose_value(endpoint):
+    with pytest.raises(ValueError) as error:
+        corpus_settings({**settings_env(), "CORPUS_S3_ENDPOINT": endpoint})
+    assert "CORPUS_S3_ENDPOINT" in str(error.value)
+    assert endpoint not in str(error.value)
+
+
+def test_import_does_not_require_boto3(monkeypatch):
+    import importlib.util
+
+    from benchmarks.unseen import bank
+
+    monkeypatch.setitem(sys.modules, "boto3", None)
+    spec = importlib.util.spec_from_file_location("offline_bank", bank.__file__)
+    module = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(module)
+    assert module.CorpusBank.key_for("a", "b") == CorpusBank.key_for("a", "b")
diff --git a/tests/test_unseen_draft.py b/tests/test_unseen_draft.py
index f29d063..975d9fd 100644
--- a/tests/test_unseen_draft.py
+++ b/tests/test_unseen_draft.py
@@ -1519,3 +1519,301 @@ def test_pool_configuration_change_refuses_resume_before_io(tmp_path, changed):
     )
     assert report["status"] == "resume_refused" and report["changed_parameters"] == list(changed)
     assert api.calls == 0 and not clones.counts
+
+
+class CorpusFakeObjects:
+    def __init__(self):
+        self.objects = {}
+        self.coordinator = os.getpid()
+
+    def get(self, key):
+        assert os.getpid() == self.coordinator
+        return (self.objects[key], "v1") if key in self.objects else None
+
+    def put(self, key, data, labels):
+        assert os.getpid() == self.coordinator
+        self.objects[key] = data
+
+    def keys(self, prefix):
+        assert os.getpid() == self.coordinator
+        return list(reversed([key for key in self.objects if key.startswith(prefix)]))
+
+
+@pytest.mark.parametrize("workers", [1, 4])
+@pytest.mark.parametrize("short_refs", [False, True])
+def test_bank_resume_stream_contract_seed_order_and_forks(tmp_path, monkeypatch, workers, short_refs):
+    from benchmarks.unseen.bank import CorpusBank
+
+    monkeypatch.setattr(importlib.import_module("benchmarks.unseen.journal").os, "fsync", lambda fd: None)
+    ordered = s.ordered_advisories(list(FakeAPI(10).advisories()), 7)
+    names = [next(iter(s.fix_links(row)))[0] for row in ordered]
+    ranks = {name: i for i, name in enumerate(names)}
+    called = multiprocessing.get_context("fork").Array("i", 10)
+    changes = entries()[0]["changes"]
+    selected = []
+    original_assign = d.assign_slices
+
+    class API(FakeAPI):
+        def advisories(self):
+            for row in super().advisories():
+                if short_refs:
+                    row["references"] = [row["references"][0][:-33]]
+                yield row
+
+        def get_commit(self, name, sha):
+            return super().get_commit(name, "a" * 40)
+
+        def get_repo(self, name):
+            result = super().get_repo(name)
+            if name == names[3]:
+                result["source"] = {"full_name": names[1]}
+            return result
+
+    def extract_changes(git, candidate, fixes, *, seed):
+        rank = ranks[candidate.repository]
+        called[rank] += 1
+        if rank == 0:
+            raise s.Rejected("no_ordinary")
+        return copy.deepcopy(changes), {"eligible": 40}, {"bytes": 12, "files": 1}
+
+    def assign(rows, **kwargs):
+        selected.append([row["repository"] for row in rows])
+        return original_assign(rows, **kwargs)
+
+    monkeypatch.setattr(d, "repository_changes", extract_changes)
+    monkeypatch.setattr(d, "assign_slices", assign)
+
+    def run(path, bank=None):
+        used = e.UsedSet()
+        return d.run(
+            tmp_path / "repo",
+            github=API(10),
+            osv=FakeOSV(),
+            clones=FakeClones(),
+            used=used,
+            seed=7,
+            known_empty=set(used.sources),
+            journal_path=path,
+            extract_workers=workers,
+            pool_size=4,
+            slices=1,
+            bank=bank,
+        )
+
+    full_objects = CorpusFakeObjects()
+    full_bank = CorpusBank(full_objects, seed=7)
+    full = run(tmp_path / "full", full_bank)
+    assert full["status"] == "draft", full
+    decisions = full_bank.decided()
+    assert len(decisions) == sum(called)
+    assert {obj["decision"] for obj in decisions.values()} == {"accept", "reject"}
+    resumed_objects = CorpusFakeObjects()
+    resumed_bank = CorpusBank(resumed_objects, seed=7)
+    # Partial completion can be out of seed order, including a fork that loses
+    # to an earlier fresh result. Rejections alone are contract sensitive.
+    for obj in decisions.values():
+        rank = ranks[obj["repository"]]
+        if rank in {0, 2, 3}:
+            result = {"entry": obj["entry"]} if obj["decision"] == "accept" else {"rejected": obj["reason"]}
+            result.update(ordinary_exclusions=obj["ordinary_exclusions"], counts=obj["counts"])
+            resumed_bank.bank(
+                obj["repository"], obj["fix"], result, contract=d.EXTRACTION_CONTRACT if rank == 0 else "old-accepted-contract"
+            )
+    resumed_bank.bank(names[1], "a" * 40, {"rejected": "old_failure"}, contract="old")
+    before = list(called)
+    resumed = run(tmp_path / "resume", resumed_bank)
+    assert resumed["status"] == "draft", resumed
+    assert selected == [[names[i] for i in (1, 2, 4, 5)]] * 2
+    assert resumed["manifest_sha256"] == full["manifest_sha256"]
+    assert all(called[i] == before[i] for i in (0, 2, 3))
+    assert called[1] == before[1] + 1
+    for filename in ("draft-p1.toml", "private-draft-p1.toml"):
+        assert (tmp_path / "resume" / filename).read_bytes() == (tmp_path / "full" / filename).read_bytes()
+    # A corrupt/stale local journal and code fingerprint must not be cross-run truth.
+    (tmp_path / "resume" / "inputs.json").write_text('{"design_draft":"old"}')
+    (tmp_path / "resume" / "extraction.jsonl").write_text("torn")
+    before = list(called)
+    again = run(tmp_path / "resume", resumed_bank)
+    assert again["manifest_sha256"] == full["manifest_sha256"]
+    assert list(called) == before
+
+
+@pytest.mark.parametrize("failure", ["crash", "persistent_put"])
+def test_bank_crash_resume_and_durability_failure(tmp_path, monkeypatch, failure):
+    from benchmarks.unseen.bank import CorpusBank
+
+    monkeypatch.setattr(importlib.import_module("benchmarks.unseen.journal").os, "fsync", lambda fd: None)
+    changes = entries()[0]["changes"]
+    monkeypatch.setattr(d, "repository_changes", lambda *a, **kw: (copy.deepcopy(changes), {}, {"bytes": 1, "files": 1}))
+
+    class Objects(CorpusFakeObjects):
+        interrupted = False
+        puts = 0
+
+        def put(self, key, data, labels):
+            self.puts += 1
+            if failure == "persistent_put" and not self.interrupted:
+                raise OSError("offline simulated bank outage")
+            super().put(key, data, labels)
+            if not self.interrupted:
+                self.interrupted = True
+                raise KeyboardInterrupt
+
+    objects = Objects()
+    bank = CorpusBank(objects, seed=7)
+
+    def run(path, bank):
+        used = e.UsedSet()
+        return d.run(
+            tmp_path / "repo",
+            github=FakeAPI(8),
+            osv=FakeOSV(),
+            clones=FakeClones(),
+            used=used,
+            seed=7,
+            known_empty=set(used.sources),
+            journal_path=path,
+            extract_workers=1,
+            pool_size=3,
+            slices=1,
+            bank=bank,
+        )
+
+    if failure == "crash":
+        with pytest.raises(KeyboardInterrupt):
+            run(tmp_path / "resume", bank)
+        assert len(bank.decided()) == 1
+    else:
+        report = run(tmp_path / "resume", bank)
+        assert report["status"] == "instrument_failure"
+        assert objects.puts == 2
+        assert not objects.objects
+        assert not (tmp_path / "resume" / "draft-p1.toml").exists()
+        objects.interrupted = True
+    resumed = run(tmp_path / "resume", bank)
+    full = run(tmp_path / "full", None)
+    assert resumed["status"] == full["status"] == "draft"
+    assert resumed["manifest_sha256"] == full["manifest_sha256"]
+
+
+@pytest.mark.parametrize("bank_args,prefix", [([], None), (["--bank"], "unseen"), (["--bank", "custom"], "custom")])
+def test_cli_corpus_bank_is_opt_in(tmp_path, monkeypatch, capsys, bank_args, prefix):
+    from openultrasast import config
+    from openultrasast.plane import memory
+
+    objects = CorpusFakeObjects()
+    monkeypatch.setattr(config, "load_dotenv", lambda *a: None)
+    monkeypatch.setattr(memory, "open_store", lambda *a, **kw: object())
+    monkeypatch.setattr(d.eligibility, "build_used", lambda *a, **kw: e.UsedSet())
+    monkeypatch.setattr(d.source, "GitHub", lambda *a: FakeAPI(0))
+    monkeypatch.setattr(d.source, "OSV", FakeOSV)
+    settings_calls = []
+    monkeypatch.setattr(d, "corpus_settings", lambda: settings_calls.append(True) or {"bucket": "ousast-corpus"})
+
+    def make_objects(**kwargs):
+        assert kwargs == {"bucket": "ousast-corpus"}
+        return objects
+
+    def run(*args, **kwargs):
+        bank = kwargs["bank"]
+        if prefix is None:
+            assert bank is None
+        else:
+            assert bank.client is objects and bank.decisions_prefix == f"{prefix}/7/decisions/"
+        return {"status": "draft"}
+
+    monkeypatch.setattr(d, "CorpusObjects", make_objects)
+    monkeypatch.setattr(d, "run", run)
+    assert d.main(["--root", str(tmp_path / "repo"), "--cache", str(tmp_path / "cache"), "--seed", "7", *bank_args]) == 0
+    assert settings_calls == ([] if prefix is None else [True])
+
+
+def test_bank_accepts_survive_missing_advisories_and_obey_used_networks(tmp_path, monkeypatch):
+    from benchmarks.unseen.bank import CorpusBank
+
+    objects = CorpusFakeObjects()
+    bank = CorpusBank(objects, seed=7)
+    rows = s.ordered_advisories(list(FakeAPI(4).advisories()), 7)
+    names = [next(iter(s.fix_links(row)))[0] for row in rows]
+    for row in rows:
+        candidate = s.candidate(row, FakeAPI(), FakeOSV())
+        entry = {**d.asdict(candidate), "changes": entries()[0]["changes"], "instrument": {"bytes": 12, "files": 1}}
+        bank.bank(candidate.repository, candidate.fix, {"entry": entry}, contract="older")
+
+    class API(FakeAPI):
+        def get_repo(self, name):
+            result = super().get_repo(name)
+            if name == names[2]:
+                result["source"] = {"full_name": names[1]}
+            return result
+
+        def get_commit(self, *args):
+            pytest.fail("banked accepts must not be re-decided")
+
+    used = e.UsedSet()
+    used.add("pairs", {names[0]}, size=len(names[0]))
+    selected = []
+    original = d.assign_slices
+
+    def assign(rows, **kwargs):
+        selected.extend(row["repository"] for row in rows)
+        return original(rows, **kwargs)
+
+    monkeypatch.setattr(d, "assign_slices", assign)
+    report = d.run(
+        tmp_path / "repo",
+        github=API(0),
+        osv=FakeOSV(),
+        clones=FakeClones(),
+        used=used,
+        seed=7,
+        known_empty={key for key, names in used.sources.items() if not names},
+        journal_path=tmp_path / "journal",
+        pool_size=2,
+        slices=1,
+        bank=bank,
+    )
+    assert report["status"] == "draft", report
+    assert selected == [names[1], names[3]]
+    assert report["rejections"]["fork_network"] == 1
+    assert len(bank.decided()) == 4
+
+
+@pytest.mark.parametrize("workers", [1, 4])
+def test_bank_duplicate_advisory_cannot_overwrite_pair_decision(tmp_path, monkeypatch, workers):
+    from benchmarks.unseen.bank import CorpusBank
+
+    rows = s.ordered_advisories(list(FakeAPI(6).advisories()), 7)
+    rows[1]["references"] = rows[0]["references"][:]
+    rows[1]["cwes"] = []  # Would reject if re-decided under this later advisory.
+    repository, fix = next(iter(s.fix_links(rows[0])))
+
+    class API(FakeAPI):
+        def advisories(self):
+            return iter(copy.deepcopy(rows))
+
+    changes = entries()[0]["changes"]
+    monkeypatch.setattr(d, "repository_changes", lambda *a, **kw: (copy.deepcopy(changes), {}, {"bytes": 12, "files": 1}))
+    bank = CorpusBank(CorpusFakeObjects(), seed=7)
+    reports = []
+    for name in ("first", "resumed"):
+        used = e.UsedSet()
+        reports.append(
+            d.run(
+                tmp_path / "repo",
+                github=API(),
+                osv=FakeOSV(),
+                clones=FakeClones(),
+                used=used,
+                known_empty=set(used.sources),
+                seed=7,
+                pool_size=3,
+                slices=1,
+                extract_workers=workers,
+                journal_path=tmp_path / name,
+                bank=bank,
+            )
+        )
+    assert all(report["status"] == "draft" for report in reports)
+    assert reports[0]["manifest_sha256"] == reports[1]["manifest_sha256"]
+    assert bank.decided()[bank.key_for(repository, fix)]["decision"] == "accept"