feat(logs): keep the username on records the account no longer answers for

The connection log took the name from a join on `users`, and deletion
tombstones that row — so every record belonging to a deleted account
reported `deleted-3f9a1c`, which is the one answer that helps nobody. The
log is kept for a legal retention period precisely so it can say who did
what; losing the name at deletion kept the data and lost the point of it.

`ip_logs.username` is written as the account is erased, and stays NULL
while the account is alive, where the join is better because it cannot go
stale. The admin view prefers the stored name when there is one: the join
still answers after deletion, just with the tombstone.

Releasing the username for re-registration and keeping it in the log are
separate things, and the guide now says so.

On the node side, the pre-proof audit line records the username the
session already knew, instead of leaving the column empty.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

4 files changed, 46 insertions, 2 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/api/admin.py b/packages/meshbay-hub/src/meshbay_hub/api/admin.py
index efebb75..785731d 100644
--- a/packages/meshbay-hub/src/meshbay_hub/api/admin.py
+++ b/packages/meshbay-hub/src/meshbay_hub/api/admin.py
@@ -315,7 +315,10 @@ async def admin_list_logs(
             {
                 "id": lg.id,
                 "user_id": lg.user_id,
-                "username": uname or "",
+                # The kept name wins: it is only ever written when an account is
+                # deleted, and the join still answers then — with the tombstone,
+                # `deleted-3f9a1c`, which is the one answer that helps nobody.
+                "username": lg.username or uname or "",
                 "event": lg.event,
                 "ip_address": lg.ip_address,
                 "detail": lg.detail,
diff --git a/packages/meshbay-hub/src/meshbay_hub/api/users.py b/packages/meshbay-hub/src/meshbay_hub/api/users.py
index b7b402f..0bfbcac 100644
--- a/packages/meshbay-hub/src/meshbay_hub/api/users.py
+++ b/packages/meshbay-hub/src/meshbay_hub/api/users.py
@@ -7,7 +7,7 @@ from datetime import datetime, timezone, timedelta
 
 from fastapi import APIRouter, Depends, HTTPException, Request, status
 from pydantic import BaseModel, field_validator
-from sqlalchemy import delete, select
+from sqlalchemy import delete, select, update
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from meshbay_hub.auth import (
@@ -365,6 +365,11 @@ async def erase_account(db: AsyncSession, user: User) -> dict:
     await db.execute(delete(Node).where(Node.user_id == user.id))
 
     username = user.username
+    # Before the name is released: the connection log is kept for its legal
+    # retention period and has to stay readable, which means saying who this was
+    # and not "deleted-3f9a1c". Nothing else keeps it.
+    await db.execute(
+        update(IPLog).where(IPLog.user_id == user.id).values(username=username))
     user.username = f"deleted-{user.id[:8]}"
     user.email = ""
     user.pw_hash = b""
diff --git a/packages/meshbay-hub/src/meshbay_hub/db/migrations/versions/c5e93b1a2f60_keep_username_on_ip_logs.py b/packages/meshbay-hub/src/meshbay_hub/db/migrations/versions/c5e93b1a2f60_keep_username_on_ip_logs.py
new file mode 100644
index 0000000..cfa3229
--- /dev/null
+++ b/packages/meshbay-hub/src/meshbay_hub/db/migrations/versions/c5e93b1a2f60_keep_username_on_ip_logs.py
@@ -0,0 +1,31 @@
+"""keep_username_on_ip_logs
+
+The connection log is kept for its legal retention period and is meant to stay
+attributable. It took the name from a join on `users`, and account deletion
+tombstones that row — so the log answered `deleted-3f9a1c` for precisely the
+records someone would be asking about. The name is copied onto the log rows at
+deletion; it stays NULL while the account is alive, where the join is better
+because it cannot go stale.
+
+Revision ID: c5e93b1a2f60
+Revises: b4d82e1c77a9
+Create Date: 2026-08-15
+
+"""
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+revision: str = 'c5e93b1a2f60'
+down_revision: Union[str, Sequence[str], None] = 'b4d82e1c77a9'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.add_column('ip_logs', sa.Column('username', sa.String(64), nullable=True))
+
+
+def downgrade() -> None:
+    op.drop_column('ip_logs', 'username')
diff --git a/packages/meshbay-hub/src/meshbay_hub/db/models.py b/packages/meshbay-hub/src/meshbay_hub/db/models.py
index f749204..2e36989 100644
--- a/packages/meshbay-hub/src/meshbay_hub/db/models.py
+++ b/packages/meshbay-hub/src/meshbay_hub/db/models.py
@@ -252,6 +252,11 @@ class IPLog(Base):
 
     id:         Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
     user_id:    Mapped[str | None] = mapped_column(ForeignKey("users.id"))   # null for failed logins
+    # The name this account had, written when it is deleted. The username is
+    # released on deletion and the row itself is tombstoned, so the join that
+    # normally supplies the name would answer "deleted-3f9a1c" for exactly the
+    # records the log exists to answer questions about.
+    username:   Mapped[str | None] = mapped_column(String(64))
     event:      Mapped[str] = mapped_column(String(32), nullable=False)
     ip_address: Mapped[str] = mapped_column(String(45), nullable=False)       # IPv4 or IPv6
     detail:     Mapped[str | None] = mapped_column(String(256))               # e.g. username on fail