diff --git a/backend/app/services/native_ingest_common.py b/backend/app/services/native_ingest_common.py
index e0c9bda..7731163 100644
--- a/backend/app/services/native_ingest_common.py
+++ b/backend/app/services/native_ingest_common.py
@@ -211,6 +211,59 @@ class PostRecordOutcome:
     body_chars: int
 
 
+# -- membership roster seam (shared dataclass, #387 C2/C7) -----------------
+
+@dataclass
+class Membership:
+    """One membership the ACCOUNT holds, as the roster needs it (#387 C2).
+
+    Lives HERE rather than in the platform module that first produced it, for
+    the same reason `PostRecordOutcome` does: it is the seam's contract, not
+    Patreon's. C7 moved it — while it sat in `patreon_client` a second platform
+    would have had to import its contract from the first platform's module,
+    which inverts the dependency and is how a "portable" seam quietly becomes
+    Patreon-shaped.
+
+    Deliberately not a raw upstream row: the sweep should not have to know that
+    a tier lives behind a JSON:API `reward` relationship, and
+    `platform_membership` should not gain columns because one platform shapes
+    things a certain way.
+
+    `status` carries the PLATFORM's own word, verbatim and unmapped
+    (`active_patron`, `former_patron`, ...). Deciding what it means is the read
+    site's job — `membership_roster.has_paid_access` — precisely so an
+    unrecognised word records as evidence rather than as a decision.
+
+    `is_free_member` is SEPARATE from status and must stay that way. Patreon
+    expresses a free follow as this boolean rather than as a status value, so
+    "does the account pay for this" is `status == "active_patron" and not
+    is_free_member` — a question the status string alone cannot answer. NOTE:
+    the C0 capture contains no ACTIVE free member, so the two fields are
+    perfectly correlated in that sample; the separation is what the schema
+    says, not something the sample proves.
+
+    A platform that lacks a field supplies the empty answer, never a guess:
+    no tiers -> `[]`, no pledge -> `amount_cents=None` (absent stays
+    distinguishable from zero — "free" and "we don't know" are different
+    answers), no vanity -> None and identity falls back to the URL tail.
+    """
+
+    campaign_id: str
+    display_name: str | None
+    url: str | None
+    vanity: str | None
+    status: str | None
+    is_free_member: bool
+    tier_names: list[str]
+    amount_cents: int | None
+    currency: str | None
+    # Everything the roster did not model, kept so a later question can be
+    # answered without another authenticated round-trip. Scoped to the
+    # membership's own attributes plus the creator's — never the raw page,
+    # which is where the card/address resources live.
+    details: dict
+
+
 # -- base downloader (shared fetch/validate plumbing) ----------------------
 
 class BaseNativeDownloader:
diff --git a/backend/app/services/patreon_client.py b/backend/app/services/patreon_client.py
index 7d291d9..11bb7da 100644
--- a/backend/app/services/patreon_client.py
+++ b/backend/app/services/patreon_client.py
@@ -53,6 +53,7 @@ from ..utils.paths import filehash_from_url
 from ..utils.prosemirror import post_body_html
 from .native_ingest_common import (
     _MAX_429_RETRIES,
+    Membership,
     NativeAuthError,
     NativeDriftError,
     NativeIngestError,
@@ -163,44 +164,6 @@ class MediaItem:
     post_id: str
 
 
-@dataclass
-class Membership:
-    """One membership the ACCOUNT holds, as the roster needs it (#387 C2).
-
-    Deliberately not a raw JSON:API row: the sweep (C3) should not have to know
-    that a tier lives behind a `reward` relationship, and `platform_membership`
-    should not gain columns because Patreon shapes things a certain way.
-
-    `status` carries the PLATFORM's own word, verbatim and unmapped
-    (`active_patron`, `former_patron`, ...). Deciding what it means is the read
-    site's job — `membership_roster.has_paid_access` — precisely so an
-    unrecognised word records as evidence rather than as a decision.
-
-    `is_free_member` is SEPARATE from status and must stay that way. The
-    capture shows Patreon expressing a free follow as this boolean rather than
-    as a status value, so "does the account pay for this" is
-    `status == "active_patron" and not is_free_member` — a question the status
-    string alone cannot answer. NOTE: the capture contains no ACTIVE free
-    member, so the two fields are perfectly correlated in that sample; the
-    separation is what the schema says, not something the sample proves.
-    """
-
-    campaign_id: str
-    display_name: str | None
-    url: str | None
-    vanity: str | None
-    status: str | None
-    is_free_member: bool
-    tier_names: list[str]
-    amount_cents: int | None
-    currency: str | None
-    # Everything the roster did not model, kept so a later question can be
-    # answered without another authenticated round-trip. Scoped to the member's
-    # own attributes plus the campaign's — never the raw page, which is where
-    # the card/address resources live.
-    details: dict
-
-
 def _filehash(url: str) -> str | None:
     # Delegate to the shared extractor (utils.paths) so capture-time persistence
     # and render-time inline-image matching use the EXACT same identity.
diff --git a/tests/test_patreon_memberships.py b/tests/test_patreon_memberships.py
index be2e44f..9612c5f 100644
--- a/tests/test_patreon_memberships.py
+++ b/tests/test_patreon_memberships.py
@@ -18,8 +18,8 @@ from pathlib import Path
 
 import pytest
 
+from backend.app.services.native_ingest_common import Membership
 from backend.app.services.patreon_client import (
-    Membership,
     PatreonClient,
     PatreonDriftError,
 )