diff --git a/CHANGELOG.md b/CHANGELOG.md
index db94c67f..69703325 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -58,6 +58,7 @@
 
 ### Added
 
+- An upload says when it expires (#1047, API contract 1.86.0, additive). #1045 deletes an upload once it is older than a multi-user deployment's retention period, and its owner had no way to see that coming: the metadata carried `created_at` and the period is a server setting. `POST /uploads` and `GET /uploads/{upload_id}` now carry `expires_at` — `created_at` plus the period in force, the same boundary the clean-up uses — and `null` when nothing will delete the upload (a single-user deployment, or retention turned off).
 - A build can say which run it retries (#1042, decided in kpubdata#812, API contract 1.85.0, additive). A `run_id` is one attempt and is not reused once it ended, so a retry is a new run: `retry_of` on `POST /build` and `POST /builds` names the earlier one, and it is shown on the job (`BuildJob.retry_of`, also after a restart) and written to the manifest. The named run must be one the caller may read — otherwise the answer is the one reading it would give — and cannot be the run itself. The refusal of a run id that already ended now carries `code: run_id_ended`.
 - Per-user upload limits in a multi-user deployment (#1045, decided in kpubdata#812, API contract 1.84.0). Nothing bounded what one account could upload, and an upload was kept until its owner deleted it. Each owner may now hold 50 files and 1 GiB in total — an upload past either is refused with 409 `upload_quota_exceeded`, saying which limit and what is in use — and an upload older than 30 days is deleted, when the service starts and when its owner next uploads. `KPUBDATA_BUILDER_UPLOAD_MAX_FILES`, `KPUBDATA_BUILDER_UPLOAD_MAX_TOTAL_BYTES` and `KPUBDATA_BUILDER_UPLOAD_RETENTION_DAYS` override them; `0` turns one off. A single-user deployment applies none. **Retention deletes data:** a saved spec that names an upload past 30 days no longer builds until the file is uploaded again.
 - The publish recovery routes are in the contract (#994, API contract 1.81.0, additive): `GET` and `DELETE /builds/{run_id}/publish/receipt`, `POST /builds/{run_id}/publish/reconcile` and `GET /builds/{run_id}/publish/audit` have answered since contract 1.19.0 and 1.20.0 but were described only in the contract's prose, so a client had no schema for them and the route tests did not know them. They are now declared with `PublishReceipt`, `PublishReconcileRequest`, `PublishReconcileResponse`, `PublishReceiptReset` and `PublishAuditLog`, and their responses are checked against those schemas. Nothing on the wire changed.
diff --git a/contract/builder-api.yaml b/contract/builder-api.yaml
index 1475f4ba..be5bbd3d 100644
--- a/contract/builder-api.yaml
+++ b/contract/builder-api.yaml
@@ -1,7 +1,7 @@
 openapi: 3.1.0
 info:
   title: KPubData Builder Service API
-  version: "1.85.0"
+  version: "1.86.0"
   description: >-
     KPubData Builder(패키지 `kpubdata-builder`) 서비스 계약. BuildSpec 검증, preview, build 실행, artifact 조회,
     계약 버전 조회를 제공한다. CLI와 HTTP service mode(#36)가 동일한 도메인 계약을
@@ -20,6 +20,7 @@ info:
     추가한다(#504, additive). v1.8.0은 stable principal별 encrypted Provider
     credential CRUD와 Provider status/test API를 추가한다(#492, additive). v1.9.0은
     `/query` 응답에 child startup과 Polars engine 실행 시간을 추가한다(#523, additive).
+    v1.86.0 says when an upload expires (#1047, additive): `UploadMetadata.expires_at`, `created_at` plus the retention period in force, or `null` when nothing will delete the upload.
     v1.85.0 lets a build point at the run it retries (#1042, additive): `retry_of` on `POST /build` and `POST /builds`, shown on `BuildJob.retry_of` and in the manifest. The refusal of a run id that already ended carries `code: run_id_ended`, and both routes name it as an example.
     v1.84.0 adds per-user upload limits in a multi-user deployment (#1045, additive): `POST /uploads` answers 409 `upload_quota_exceeded` when the owner's file count or total size would pass the limit, and uploads past the retention period are deleted.
     v1.83.0 makes a `run_id` one attempt (#1042, kpubdata#812): the id of a run that ended without a manifest — one a restart interrupted — is refused to its own submitter too — with 409 on `POST /builds`, as a completed run's id is, and with 400 on `POST /build`, whose 409 is a build response with a different body.
@@ -549,6 +550,7 @@ paths:
                     size_bytes: 1024
                     original_filename: trades.csv
                     created_at: "2026-08-16T09:00:00+00:00"
+                    expires_at: "2026-09-15T09:00:00+00:00"
         "400":
           description: 빈 body, 손상된 content, 지원하지 않는 format, 또는 크기 초과
           content:
@@ -6362,6 +6364,14 @@ components:
         created_at:
           type: string
           format: date-time
+        expires_at:
+          type: [string, "null"]
+          format: date-time
+          description: >-
+            When the upload will be deleted (#1047): `created_at` plus the deployment's
+            retention period (#1045). After it the upload is gone and a spec that names
+            it no longer builds until the file is uploaded again. `null` when nothing
+            will delete it — a single-user deployment, or retention turned off.
 
     UploadDeleteResponse:
       type: object
diff --git a/contract/fixtures/responses.json b/contract/fixtures/responses.json
index 1f7bb1b5..e7e80928 100644
--- a/contract/fixtures/responses.json
+++ b/contract/fixtures/responses.json
@@ -1,6 +1,6 @@
 {
   "fixture_format": 1,
-  "contract_version": "1.85.0",
+  "contract_version": "1.86.0",
   "probe_field": "future_optional_field",
   "rules": "A response may gain optional fields in any minor version; a client ignores fields it does not know. A required field keeps its name and type until the next major version; a client rejects a body whose required field is missing or mistyped.",
   "fixtures": [
@@ -533,7 +533,8 @@
         "encoding": "utf-8",
         "size_bytes": 1024,
         "original_filename": "trades.csv",
-        "created_at": "2026-08-16T09:00:00+00:00"
+        "created_at": "2026-08-16T09:00:00+00:00",
+        "expires_at": "2026-09-15T09:00:00+00:00"
       },
       "with_additive_fields": {
         "upload_id": "upl_0123456789abcdef0123456789abcdef",
@@ -542,6 +543,7 @@
         "size_bytes": 1024,
         "original_filename": "trades.csv",
         "created_at": "2026-08-16T09:00:00+00:00",
+        "expires_at": "2026-09-15T09:00:00+00:00",
         "future_optional_field": "added by a later minor contract version"
       },
       "additive_paths": [
@@ -553,7 +555,8 @@
         "encoding": "utf-8",
         "size_bytes": 1024,
         "original_filename": "trades.csv",
-        "created_at": "2026-08-16T09:00:00+00:00"
+        "created_at": "2026-08-16T09:00:00+00:00",
+        "expires_at": "2026-09-15T09:00:00+00:00"
       },
       "broken_path": "$.upload_id"
     },
diff --git a/src/kpubdata_builder/service/app.py b/src/kpubdata_builder/service/app.py
index 83295775..081aaa34 100644
--- a/src/kpubdata_builder/service/app.py
+++ b/src/kpubdata_builder/service/app.py
@@ -417,7 +417,9 @@ def _enforce_ownership() -> bool:
 #   may answer 409 upload_quota_exceeded (#1045, additive).
 # 1.84.0 -> 1.85.0: retry_of on both build routes, on BuildJob and in the manifest; the
 #   used-run-id refusal carries code run_id_ended (#1042, additive).
-API_CONTRACT_VERSION = "1.85.0"
+# 1.85.0 -> 1.86.0: UploadMetadata.expires_at — when the retention period deletes the
+#   upload, or null (#1047, additive).
+API_CONTRACT_VERSION = "1.86.0"
 
 #: How long a synchronous ``POST /build`` waits for a build slot before it answers
 #: ``build_queue_full`` (#1040). Long enough to ride out a short build ahead of it, short
diff --git a/src/kpubdata_builder/service/uploads_service.py b/src/kpubdata_builder/service/uploads_service.py
index f0b2fb68..567e985e 100644
--- a/src/kpubdata_builder/service/uploads_service.py
+++ b/src/kpubdata_builder/service/uploads_service.py
@@ -15,6 +15,7 @@
 import io
 import threading
 from collections.abc import Callable
+from datetime import datetime, timedelta, timezone
 
 from kpubdata_builder.ingestion import IngestionError
 from kpubdata_builder.ingestion.tabular_ingest import iter_tabular_batches
@@ -28,7 +29,27 @@
 RepositoryProvider = Callable[[], UploadRepository]
 
 
-def upload_metadata_body(metadata: UploadMetadata) -> dict[str, JsonValue]:
+def upload_expires_at(metadata: UploadMetadata, limits: UploadLimits | None) -> str | None:
+    """When the upload will be deleted (#1047), or None when nothing will delete it.
+
+    ``created_at`` plus the retention period in force — the same boundary the purge
+    uses (``UploadLimits.cutoff``). None in a single-user deployment and when retention
+    is off. Read at answer time: an operator who changes the period changes the date.
+    """
+    if limits is None or limits.retention_days is None:
+        return None
+    try:
+        created = datetime.fromisoformat(metadata.created_at)
+    except ValueError:
+        return None
+    if created.tzinfo is None:
+        created = created.replace(tzinfo=timezone.utc)
+    return (created + timedelta(days=limits.retention_days)).isoformat(timespec="seconds")
+
+
+def upload_metadata_body(
+    metadata: UploadMetadata, limits: UploadLimits | None = None
+) -> dict[str, JsonValue]:
     """Convert UploadMetadata to wire JSON (#498). Content is never included."""
     return {
         "upload_id": metadata.upload_id,
@@ -37,6 +58,9 @@ def upload_metadata_body(metadata: UploadMetadata) -> dict[str, JsonValue]:
         "size_bytes": metadata.size_bytes,
         "original_filename": metadata.original_filename,
         "created_at": metadata.created_at,
+        # So the owner can see the end coming (#1047): past it the upload is deleted and
+        # a spec that names it no longer builds.
+        "expires_at": upload_expires_at(metadata, limits),
     }
 
 
@@ -133,7 +157,7 @@ def create_upload(
                 )
             except ValueError as exc:
                 return ServiceResponse(400, {"error": str(exc)})
-        return ServiceResponse(200, upload_metadata_body(metadata))
+        return ServiceResponse(200, upload_metadata_body(metadata, limits))
 
     def purge_expired(self) -> int:
         """Delete every owner's uploads that are past retention; how many went (#1045)."""
@@ -150,7 +174,7 @@ def get_upload(self, upload_id: str, *, principal: Principal) -> ServiceResponse
         metadata = self._repository().get_metadata(principal.owner_id, upload_id)
         if metadata is None:
             return ServiceResponse(404, {"error": f"upload not found: {upload_id}"})
-        return ServiceResponse(200, upload_metadata_body(metadata))
+        return ServiceResponse(200, upload_metadata_body(metadata, self._limits()))
 
     def delete_upload(self, upload_id: str, *, principal: Principal) -> ServiceResponse:
         """Delete only uploads owned by current principal."""
diff --git a/tests/unit/test_upload_limits.py b/tests/unit/test_upload_limits.py
index 35263afb..28b3db04 100644
--- a/tests/unit/test_upload_limits.py
+++ b/tests/unit/test_upload_limits.py
@@ -290,3 +290,82 @@ def test_a_single_user_deployment_is_unchanged(
     found = dispatch(service, "GET", f"/uploads/{first}", None)
     assert isinstance(found, ServiceResponse)
     assert found.status_code == 200
+
+
+# --- expires_at: the owner can see the end coming (#1047) ---
+
+
+def _get_upload(service: BuilderService, upload_id: str) -> ServiceResponse:
+    response = dispatch(service, "GET", f"/uploads/{upload_id}", None)
+    assert isinstance(response, ServiceResponse)
+    return response
+
+
+def test_an_upload_says_when_it_expires(
+    multi_user: None, service: BuilderService, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    _as(monkeypatch, _ALICE)
+
+    created = _upload(service)
+
+    body = created.body
+    expires = datetime.fromisoformat(str(body["expires_at"]))
+    assert expires - datetime.fromisoformat(str(body["created_at"])) == timedelta(days=30)
+    # Reading it back says the same.
+    assert _get_upload(service, str(body["upload_id"])).body["expires_at"] == body["expires_at"]
+
+
+def test_the_date_follows_the_retention_period_in_force(
+    multi_user: None, service: BuilderService, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    monkeypatch.setenv(RETENTION_DAYS_ENV, "7")
+    _as(monkeypatch, _ALICE)
+
+    body = _upload(service).body
+
+    expires = datetime.fromisoformat(str(body["expires_at"]))
+    assert expires - datetime.fromisoformat(str(body["created_at"])) == timedelta(days=7)
+
+
+def test_the_date_is_the_moment_the_purge_takes_the_upload(
+    multi_user: None, service: BuilderService, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    """What the field promises and what the purge does are the same boundary."""
+    _as(monkeypatch, _ALICE)
+    upload_id = str(_upload(service).body["upload_id"])
+
+    _age(service, upload_id, days=29)
+    still_there = _get_upload(service, upload_id)
+    assert still_there.status_code == 200
+    assert datetime.fromisoformat(str(still_there.body["expires_at"])) > datetime.now(timezone.utc)
+    assert service.purge_expired_uploads() == 0
+
+    _age(service, upload_id, days=31)
+    past = _get_upload(service, upload_id)
+    assert datetime.fromisoformat(str(past.body["expires_at"])) < datetime.now(timezone.utc)
+    assert service.purge_expired_uploads() == 1
+    assert _get_upload(service, upload_id).status_code == 404
+
+
+def test_nothing_expires_when_retention_is_off(
+    multi_user: None, service: BuilderService, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    monkeypatch.setenv(RETENTION_DAYS_ENV, "0")
+    _as(monkeypatch, _ALICE)
+
+    body = _upload(service).body
+
+    assert "expires_at" in body
+    assert body["expires_at"] is None
+
+
+def test_nothing_expires_in_a_single_user_deployment(
+    service: BuilderService, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    monkeypatch.delenv("ENFORCE_OWNERSHIP", raising=False)
+    monkeypatch.delenv("OIDC_ISSUER", raising=False)
+
+    body = _upload(service).body
+
+    assert body["expires_at"] is None
+    assert _get_upload(service, str(body["upload_id"])).body["expires_at"] is None