diff --git a/decnet/clustering/impl/connected_components.py b/decnet/clustering/impl/connected_components.py
index eb95fb63..03306d87 100644
--- a/decnet/clustering/impl/connected_components.py
+++ b/decnet/clustering/impl/connected_components.py
@@ -41,6 +41,7 @@ from decnet.clustering.impl.similarity import (
     combined_edge_weight,
 )
 from decnet.logging import get_logger
+from decnet.profiler.identity_rollup import extract_fp_summaries
 from decnet.web.db.repository import BaseRepository
 
 log = get_logger("clustering.connected_components")
@@ -217,6 +218,9 @@ class ConnectedComponentsClusterer(Clusterer):
                         "identity_uuid": identity_uuid,
                         "observation_uuids": linked,
                     })
+                await _roll_up_fingerprints(
+                    repo, identity_uuid, [row_by_id[m] for m in member_ids],
+                )
                 continue
 
             # Deterministic winner so two clusterer runs produce the
@@ -250,6 +254,14 @@ class ConnectedComponentsClusterer(Clusterer):
                         "observation_uuid": obs_id,
                     })
 
+            # Re-roll the winner's fingerprint summary across every
+            # observation now in this component (including the loser
+            # side — the merge unifies their evidence even though the
+            # loser's identity row stays FK'd via merged_into_uuid).
+            await _roll_up_fingerprints(
+                repo, winner_uuid, [row_by_id[m] for m in member_ids],
+            )
+
         # Pass 2 — revocable-merge undo. For each currently-merged-out
         # identity, check whether its observations still cluster with
         # the winner's. If not, the merge is contradicted by new
@@ -341,6 +353,25 @@ async def _link(
         return False
 
 
+async def _roll_up_fingerprints(
+    repo: BaseRepository,
+    identity_uuid: str,
+    member_rows: list[dict[str, Any]],
+) -> None:
+    """Project member observations' fingerprint blobs onto the identity's
+    summary columns. Best-effort: a write failure is logged but never
+    breaks the clusterer tick — the columns just stay stale until the
+    next pass."""
+    summaries = extract_fp_summaries(member_rows)
+    try:
+        await repo.update_identity_fingerprints(identity_uuid, **summaries)
+    except Exception:  # noqa: BLE001
+        log.exception(
+            "clusterer: failed to roll up fingerprints for identity=%s",
+            identity_uuid,
+        )
+
+
 __all__ = [
     "ConnectedComponentsClusterer",
     "cluster_observations",
diff --git a/decnet/profiler/identity_rollup.py b/decnet/profiler/identity_rollup.py
new file mode 100644
index 00000000..41b14f27
--- /dev/null
+++ b/decnet/profiler/identity_rollup.py
@@ -0,0 +1,109 @@
+"""Identity-level fingerprint rollup.
+
+The clusterer mints :class:`AttackerIdentity` rows (and merges them) from
+union-find over per-IP :class:`Attacker` observations. Each ``Attacker``
+row already carries a ``fingerprints`` JSON list — the output of the
+profiler's ``_build_record`` flatten of every ``bounty_type='fingerprint'``
+bounty seen for that IP. This module distils that per-observation list
+into the cross-observation summary columns on ``AttackerIdentity``:
+
+* ``ja3_hashes``        — TLS ClientHello fingerprints
+* ``hassh_hashes``      — SSH KEX fingerprints
+* ``tls_cert_sha256``   — leaf cert SHA-256s presented by attacker-run
+                          TLS servers (active-prober capture)
+
+These are JSON-serialised ``list[str]`` columns shaped for federation
+gossip — same wire format the campaign clusterer reads. The values are
+deduplicated and sorted so two clusterer runs over the same input produce
+byte-identical column writes.
+"""
+
+from __future__ import annotations
+
+import json
+from typing import Any, Iterable, Optional
+
+
+# Bounty payload key per fingerprint family. Only fingerprints whose
+# payload carries a stable scalar identifier roll up cleanly here —
+# tcpfp / http_quirks / ja4l etc. don't fit the "list of hashes" shape
+# and stay out of the rollup until they get their own columns.
+_PAYLOAD_KEY_BY_FP_TYPE: dict[str, str] = {
+    "ja3":             "ja3",
+    "hassh_server":    "hash",
+    "tls_certificate": "cert_sha256",
+}
+
+_COLUMN_BY_FP_TYPE: dict[str, str] = {
+    "ja3":             "ja3_hashes",
+    "hassh_server":    "hassh_hashes",
+    "tls_certificate": "tls_cert_sha256",
+}
+
+
+def _payload_of(entry: Any) -> dict[str, Any]:
+    """Return the payload dict from a fingerprint bounty entry."""
+    if not isinstance(entry, dict):
+        return {}
+    p = entry.get("payload")
+    if isinstance(p, dict):
+        return p
+    if isinstance(p, str):
+        try:
+            parsed = json.loads(p)
+        except (TypeError, ValueError):
+            return {}
+        return parsed if isinstance(parsed, dict) else {}
+    # Some legacy callers may have flattened the payload onto the entry.
+    return entry
+
+
+def _parse_fingerprints(raw: Any) -> list[dict[str, Any]]:
+    """Best-effort parse of an Attacker.fingerprints column value."""
+    if raw is None:
+        return []
+    if isinstance(raw, list):
+        return [e for e in raw if isinstance(e, dict)]
+    if isinstance(raw, str):
+        try:
+            decoded = json.loads(raw)
+        except (TypeError, ValueError):
+            return []
+        return [e for e in decoded if isinstance(e, dict)] if isinstance(decoded, list) else []
+    return []
+
+
+def extract_fp_summaries(
+    member_rows: Iterable[dict[str, Any]],
+) -> dict[str, Optional[str]]:
+    """Aggregate fingerprint hashes across the given Attacker rows.
+
+    Returns a dict with keys ``ja3_hashes``, ``hassh_hashes``,
+    ``tls_cert_sha256`` — each value is either a JSON-encoded
+    ``list[str]`` (deduped, sorted) or ``None`` when no signal is
+    present. ``None`` is preferred over ``"[]"`` so the column stays
+    NULL and downstream readers can distinguish "no data yet" from
+    "actively known to be empty".
+
+    Pure: no DB, no clock, no I/O. The clusterer drives the call.
+    """
+    buckets: dict[str, set[str]] = {col: set() for col in _COLUMN_BY_FP_TYPE.values()}
+
+    for row in member_rows:
+        for entry in _parse_fingerprints(row.get("fingerprints")):
+            payload = _payload_of(entry)
+            fp_type = payload.get("fingerprint_type")
+            if not isinstance(fp_type, str):
+                continue
+            payload_key = _PAYLOAD_KEY_BY_FP_TYPE.get(fp_type)
+            column = _COLUMN_BY_FP_TYPE.get(fp_type)
+            if payload_key is None or column is None:
+                continue
+            value = payload.get(payload_key)
+            if isinstance(value, str) and value:
+                buckets[column].add(value)
+
+    return {
+        column: (json.dumps(sorted(values)) if values else None)
+        for column, values in buckets.items()
+    }
diff --git a/decnet/web/db/repository.py b/decnet/web/db/repository.py
index bd0df366..aac20518 100644
--- a/decnet/web/db/repository.py
+++ b/decnet/web/db/repository.py
@@ -474,6 +474,26 @@ class BaseRepository(ABC):
         """
         pass
 
+    @abstractmethod
+    async def update_identity_fingerprints(
+        self,
+        identity_uuid: str,
+        *,
+        ja3_hashes: Optional[str] = None,
+        hassh_hashes: Optional[str] = None,
+        tls_cert_sha256: Optional[str] = None,
+    ) -> None:
+        """Set the fingerprint summary columns on one ``AttackerIdentity``.
+
+        Each argument is a JSON-encoded ``list[str]`` (the federation
+        wire shape) or ``None`` to leave the corresponding column at
+        ``NULL``. Always overwrites — the rollup writer is the source
+        of truth for these columns, computed deterministically from
+        the identity's member observations every clusterer tick. Also
+        bumps ``updated_at`` so cache subscribers can invalidate.
+        """
+        pass
+
     # ─── Campaign clustering reads ────────────────────────────────────────
     # Layer above identity resolution: campaigns group identities into
     # operations. Populated by ``decnet campaign-clusterer``. The
diff --git a/decnet/web/db/sqlmodel_repo.py b/decnet/web/db/sqlmodel_repo.py
index 5fc56d4f..b2b8aa05 100644
--- a/decnet/web/db/sqlmodel_repo.py
+++ b/decnet/web/db/sqlmodel_repo.py
@@ -1545,6 +1545,28 @@ class SQLModelRepository(BaseRepository):
             await session.execute(statement)
             await session.commit()
 
+    async def update_identity_fingerprints(
+        self,
+        identity_uuid: str,
+        *,
+        ja3_hashes: Optional[str] = None,
+        hassh_hashes: Optional[str] = None,
+        tls_cert_sha256: Optional[str] = None,
+    ) -> None:
+        statement = (
+            update(AttackerIdentity)
+            .where(AttackerIdentity.uuid == identity_uuid)
+            .values(
+                ja3_hashes=ja3_hashes,
+                hassh_hashes=hassh_hashes,
+                tls_cert_sha256=tls_cert_sha256,
+                updated_at=datetime.now(timezone.utc),
+            )
+        )
+        async with self._session() as session:
+            await session.execute(statement)
+            await session.commit()
+
     # ─── Campaign clustering reads ────────────────────────────────────────
 
     async def get_campaign_by_uuid(self, uuid: str) -> Optional[dict[str, Any]]:
diff --git a/tests/clustering/test_connected_components.py b/tests/clustering/test_connected_components.py
index f298e896..96ba3a6b 100644
--- a/tests/clustering/test_connected_components.py
+++ b/tests/clustering/test_connected_components.py
@@ -140,14 +140,41 @@ async def repo(tmp_path):
 
 async def _seed_attacker(
     repo, ip: str, *,
-    ja3: str | None = None, hassh: str | None = None, asn: int | None = None,
+    ja3: str | None = None,
+    hassh: str | None = None,
+    asn: int | None = None,
+    cert_sha256: str | None = None,
 ) -> str:
     now = datetime.now(timezone.utc)
-    fingerprints = []
+    # Two-shape fingerprint payload:
+    #   - the "kind" entries feed the clusterer's from_attacker_row
+    #     (test-fixture shape, line ~115 of connected_components.py)
+    #   - the "bounty_type/payload" entries feed identity_rollup's
+    #     extract_fp_summaries (production shape, written by the
+    #     profiler from real bounty rows). Both shapes coexist in
+    #     the same JSON list so the same seed exercises clustering
+    #     AND the identity-column rollup.
+    fingerprints: list[dict] = []
     if ja3:
         fingerprints.append({"kind": "ja3", "hash": ja3})
+        fingerprints.append({
+            "bounty_type": "fingerprint",
+            "payload": {"fingerprint_type": "ja3", "ja3": ja3},
+        })
     if hassh:
         fingerprints.append({"kind": "hassh", "hash": hassh})
+        fingerprints.append({
+            "bounty_type": "fingerprint",
+            "payload": {"fingerprint_type": "hassh_server", "hash": hassh},
+        })
+    if cert_sha256:
+        fingerprints.append({
+            "bounty_type": "fingerprint",
+            "payload": {
+                "fingerprint_type": "tls_certificate",
+                "cert_sha256": cert_sha256,
+            },
+        })
     return await repo.upsert_attacker({
         "ip": ip,
         "first_seen": now,
@@ -377,6 +404,70 @@ async def test_tick_links_new_observation_to_existing_identity(repo):
     assert d in linked_uuids
 
 
+# ─── identity fingerprint rollup ───────────────────────────────────────────
+
+
+@pytest.mark.anyio
+async def test_tick_rolls_up_fingerprint_columns_on_create(repo):
+    """A fresh-component tick must populate ja3_hashes / hassh_hashes /
+    tls_cert_sha256 on the newly-minted identity row, deduplicated and
+    sorted across all member observations."""
+    await _seed_attacker(
+        repo, "1.1.1.1", ja3="ja3-x", hassh="hassh-y", cert_sha256="ab" * 32,
+    )
+    await _seed_attacker(
+        repo, "2.2.2.2", ja3="ja3-x", hassh="hassh-y", cert_sha256="cd" * 32,
+    )
+    c = ConnectedComponentsClusterer()
+    result = await c.tick(repo)
+    assert len(result.identities_formed) == 1
+    identity_uuid = result.identities_formed[0]["identity_uuid"]
+
+    rows = {i["uuid"]: i for i in await repo.list_all_identities()}
+    identity = rows[identity_uuid]
+    assert json.loads(identity["ja3_hashes"]) == ["ja3-x"]
+    assert json.loads(identity["hassh_hashes"]) == ["hassh-y"]
+    assert json.loads(identity["tls_cert_sha256"]) == sorted(["ab" * 32, "cd" * 32])
+
+
+@pytest.mark.anyio
+async def test_tick_rolls_up_fingerprints_on_link(repo):
+    """When a new observation links into an existing identity, the
+    rollup must reflect any new cert SHA-256 it brings."""
+    await _seed_attacker(
+        repo, "1.1.1.1", ja3="ja3-x", cert_sha256="ab" * 32,
+    )
+    c = ConnectedComponentsClusterer()
+    first = await c.tick(repo)
+    identity_uuid = first.identities_formed[0]["identity_uuid"]
+
+    # New observation, same JA3, fresh cert.
+    await _seed_attacker(
+        repo, "2.2.2.2", ja3="ja3-x", cert_sha256="cd" * 32,
+    )
+    await c.tick(repo)
+
+    rows = {i["uuid"]: i for i in await repo.list_all_identities()}
+    identity = rows[identity_uuid]
+    assert json.loads(identity["tls_cert_sha256"]) == sorted(["ab" * 32, "cd" * 32])
+
+
+@pytest.mark.anyio
+async def test_tick_leaves_columns_null_when_no_fingerprints(repo):
+    """Two attackers with NO fingerprint signal cluster as separate
+    singletons; their identity rows must keep all rollup columns NULL
+    (not "[]" — NULL distinguishes 'no signal yet' from 'known empty')."""
+    await _seed_attacker(repo, "1.1.1.1")
+    await _seed_attacker(repo, "2.2.2.2")
+    c = ConnectedComponentsClusterer()
+    await c.tick(repo)
+
+    for identity in await repo.list_all_identities():
+        assert identity["ja3_hashes"] is None
+        assert identity["hassh_hashes"] is None
+        assert identity["tls_cert_sha256"] is None
+
+
 # ─── fixture-bound assertions (in-memory) ──────────────────────────────────
 
 
diff --git a/tests/profiler/test_identity_rollup.py b/tests/profiler/test_identity_rollup.py
new file mode 100644
index 00000000..0036f0fd
--- /dev/null
+++ b/tests/profiler/test_identity_rollup.py
@@ -0,0 +1,141 @@
+"""Tests for ``decnet.profiler.identity_rollup.extract_fp_summaries``.
+
+Pure unit tests against the production bounty shape that
+``decnet.profiler.worker._build_record`` writes into
+``Attacker.fingerprints`` — a list of ``{bounty_type, payload, ...}``
+dicts where the meaningful data lives under ``payload.fingerprint_type``.
+"""
+
+from __future__ import annotations
+
+import json
+
+from decnet.profiler.identity_rollup import extract_fp_summaries
+
+
+def _bounty(fp_type: str, **payload_extras) -> dict:
+    """Build a bounty dict shaped the way the profiler writes it."""
+    return {
+        "bounty_type": "fingerprint",
+        "payload": {"fingerprint_type": fp_type, **payload_extras},
+    }
+
+
+def _row_with(*entries) -> dict:
+    return {"fingerprints": json.dumps(list(entries))}
+
+
+class TestExtractFpSummaries:
+
+    def test_empty_input_returns_all_none(self):
+        result = extract_fp_summaries([])
+        assert result == {
+            "ja3_hashes": None,
+            "hassh_hashes": None,
+            "tls_cert_sha256": None,
+        }
+
+    def test_single_row_single_cert(self):
+        row = _row_with(_bounty("tls_certificate", cert_sha256="ab" * 32))
+        result = extract_fp_summaries([row])
+        assert result["ja3_hashes"] is None
+        assert result["hassh_hashes"] is None
+        assert json.loads(result["tls_cert_sha256"]) == ["ab" * 32]
+
+    def test_dedupe_across_rows(self):
+        sha = "ab" * 32
+        a = _row_with(_bounty("tls_certificate", cert_sha256=sha))
+        b = _row_with(_bounty("tls_certificate", cert_sha256=sha))
+        result = extract_fp_summaries([a, b])
+        assert json.loads(result["tls_cert_sha256"]) == [sha]
+
+    def test_sorted_output_is_deterministic(self):
+        a = _row_with(
+            _bounty("tls_certificate", cert_sha256="ff" * 32),
+            _bounty("tls_certificate", cert_sha256="11" * 32),
+            _bounty("tls_certificate", cert_sha256="aa" * 32),
+        )
+        result = extract_fp_summaries([a])
+        # Same input twice must produce byte-identical output.
+        assert result == extract_fp_summaries([a])
+        assert json.loads(result["tls_cert_sha256"]) == sorted(
+            ["ff" * 32, "11" * 32, "aa" * 32]
+        )
+
+    def test_all_three_families_at_once(self):
+        row = _row_with(
+            _bounty("ja3", ja3="ja3-abc"),
+            _bounty("hassh_server", hash="hassh-def"),
+            _bounty("tls_certificate", cert_sha256="ab" * 32),
+        )
+        result = extract_fp_summaries([row])
+        assert json.loads(result["ja3_hashes"]) == ["ja3-abc"]
+        assert json.loads(result["hassh_hashes"]) == ["hassh-def"]
+        assert json.loads(result["tls_cert_sha256"]) == ["ab" * 32]
+
+    def test_unknown_fingerprint_type_ignored(self):
+        # tcpfp / ja4l / http_quirks have no rollup column yet; they
+        # must not pollute the three families that do.
+        row = _row_with(
+            _bounty("tcpfp", hash="tcpfp-x"),
+            _bounty("ja4l", ja4l="ja4l-y"),
+            _bounty("http_quirks", quirks="..."),
+        )
+        result = extract_fp_summaries([row])
+        assert result["ja3_hashes"] is None
+        assert result["hassh_hashes"] is None
+        assert result["tls_cert_sha256"] is None
+
+    def test_missing_payload_key_skipped(self):
+        # tls_certificate bounty shaped like a sniffer-only payload
+        # (no cert_sha256). Must not crash, must not record an entry.
+        row = _row_with({
+            "bounty_type": "fingerprint",
+            "payload": {"fingerprint_type": "tls_certificate", "subject_cn": "x"},
+        })
+        result = extract_fp_summaries([row])
+        assert result["tls_cert_sha256"] is None
+
+    def test_malformed_fingerprints_json_returns_all_none(self):
+        result = extract_fp_summaries([{"fingerprints": "not json"}])
+        assert all(v is None for v in result.values())
+
+    def test_missing_fingerprints_field_returns_all_none(self):
+        result = extract_fp_summaries([{"some_other_field": True}])
+        assert all(v is None for v in result.values())
+
+    def test_payload_as_string_is_json_decoded(self):
+        # Defensive: some legacy storage may have nested-stringified payloads.
+        row = {
+            "fingerprints": json.dumps([{
+                "bounty_type": "fingerprint",
+                "payload": json.dumps({
+                    "fingerprint_type": "tls_certificate",
+                    "cert_sha256": "cd" * 32,
+                }),
+            }]),
+        }
+        result = extract_fp_summaries([row])
+        assert json.loads(result["tls_cert_sha256"]) == ["cd" * 32]
+
+    def test_non_string_hash_values_skipped(self):
+        row = _row_with({
+            "bounty_type": "fingerprint",
+            "payload": {"fingerprint_type": "tls_certificate", "cert_sha256": 12345},
+        })
+        result = extract_fp_summaries([row])
+        assert result["tls_cert_sha256"] is None
+
+    def test_dedup_across_many_rows_with_overlap(self):
+        rows = [
+            _row_with(_bounty("ja3", ja3="ja3-shared")),
+            _row_with(
+                _bounty("ja3", ja3="ja3-shared"),
+                _bounty("ja3", ja3="ja3-second"),
+            ),
+            _row_with(_bounty("ja3", ja3="ja3-third")),
+        ]
+        result = extract_fp_summaries(rows)
+        assert json.loads(result["ja3_hashes"]) == sorted(
+            ["ja3-shared", "ja3-second", "ja3-third"]
+        )