diff --git a/src/ingestion/connectors/ai/claude-team/connector.yaml b/src/ingestion/connectors/ai/claude-team/connector.yaml
index b4c156310..d56389e3b 100644
--- a/src/ingestion/connectors/ai/claude-team/connector.yaml
+++ b/src/ingestion/connectors/ai/claude-team/connector.yaml
@@ -255,9 +255,18 @@ streams:
           - type: AddedFieldDefinition
             path: [source_id]
             value: "{{ config['insight_source_id'] }}"
+          # The month belongs in the key. This endpoint reports the billing
+          # month in progress and carries no history, so a month exists only in
+          # the rows read during it. Keyed on the seat alone, Bronze kept one
+          # row per seat — its latest state — and every closed month became
+          # unreproducible: a `dbt --full-refresh` (dispatched by a MAJOR
+          # descriptor bump) rebuilt Silver from that residue and silently
+          # dropped the history. Keyed on seat-and-month, Bronze retains the
+          # closing state of each month, which is the grain Silver already
+          # keeps, and a rebuild reproduces it.
           - type: AddedFieldDefinition
             path: [unique_key]
-            value: "{{ config['insight_tenant_id'] }}-{{ config['insight_source_id'] }}-{{ record['account_uuid'] }}"
+            value: "{{ config['insight_tenant_id'] }}-{{ config['insight_source_id'] }}-{{ record['account_uuid'] }}-{{ now_utc().strftime('%Y-%m') }}"
           - type: AddedFieldDefinition
             path: [collected_at]
             value: "{{ now_utc().strftime('%Y-%m-%dT%H:%M:%SZ') }}"
diff --git a/src/ingestion/connectors/ai/claude-team/dbt/claude_team__ai_overage.sql b/src/ingestion/connectors/ai/claude-team/dbt/claude_team__ai_overage.sql
index 57d0e69a5..749451003 100644
--- a/src/ingestion/connectors/ai/claude-team/dbt/claude_team__ai_overage.sql
+++ b/src/ingestion/connectors/ai/claude-team/dbt/claude_team__ai_overage.sql
@@ -40,9 +40,10 @@
 ) }}
 
 WITH latest_per_seat_month AS (
-    -- Bronze is full-refresh+append: every sync re-emits all seats with the
-    -- same unique_key (no date). Collapse to the latest snapshot per seat per
-    -- calendar month so each (seat, month) keeps its freshest spend reading.
+    -- Bronze is full-refresh+append and its unique_key carries the extraction
+    -- month, so it keeps each seat's closing state per month. Collapsing here
+    -- is still required: repeated syncs within a month re-emit the seat, and
+    -- rows written before the key carried a month have no month in theirs.
     SELECT *
     FROM {{ source('bronze_claude_team', 'claude_team_overage_spend') }}
     WHERE account_uuid IS NOT NULL
@@ -60,9 +61,11 @@ WITH latest_per_seat_month AS (
 SELECT
     tenant_id                                           AS insight_tenant_id,
     source_id,
-    -- Silver dedup key: tenant-source-seat-month. The month component (absent
-    -- from the Bronze unique_key) preserves monthly history and gives intra-
-    -- month idempotency (latest snapshot wins via _version, same key).
+    -- Silver dedup key: tenant-source-seat-month, the same grain Bronze now
+    -- keys on. Derived here from the extraction timestamp rather than copied,
+    -- so rows written under the older key still land in the right month. The
+    -- month preserves history and gives intra-month idempotency (latest
+    -- snapshot wins via _version, same key).
     CAST(concat(
         coalesce(tenant_id, ''), '-',
         coalesce(source_id, ''), '-',
diff --git a/src/ingestion/connectors/ai/claude-team/descriptor.yaml b/src/ingestion/connectors/ai/claude-team/descriptor.yaml
index 4013a873a..8520d15ec 100644
--- a/src/ingestion/connectors/ai/claude-team/descriptor.yaml
+++ b/src/ingestion/connectors/ai/claude-team/descriptor.yaml
@@ -15,7 +15,14 @@ name: claude-team
 #   conversation_count and declares tool_label — MAJOR per ADR-0015:
 #   pre-existing rows must re-materialize from Bronze to populate the new
 #   columns (one-shot scoped full refresh).
-version: "2.0.0"
+# 2.1.0: claude_team_overage_spend's unique_key gains the extraction month, so
+#   Bronze retains one row per seat per billing month instead of one per seat.
+#   MINOR per ADR-0015 — additive: existing rows keep their keys and stay valid,
+#   nothing has to re-materialize. Deliberately NOT major: a major bump
+#   dispatches a one-shot `dbt --full-refresh` (reconcile-connectors), which
+#   rebuilds Silver from Bronze — the very operation this change exists to make
+#   safe, and the one that cost the June history.
+version: "2.1.0"
 # Daily at 04:00 UTC — off-peak vs other connectors. The customer's
 # proxy runs a single browser instance, so we avoid scheduling
 # claude-team next to anything else that may also hit it.