diff --git a/TOOLING.md b/TOOLING.md
index 7e3c353..49e18f4 100644
--- a/TOOLING.md
+++ b/TOOLING.md
@@ -67,6 +67,51 @@ Long runs: `setsid nohup ~/gdl/run-profiles.sh >/dev/null 2>&1 &` (or `run-full-
 Nothing reaches the archive until a run finishes, so killing one midway is
 safe.
 
+## 2026-09-14 — a tracked account renamed on Instagram: 0ct0ber19 → heejin
+
+HeeJin's handle changed and the old one is now fully dead — `instagram.com/
+0ct0ber19/` returns "Sorry, this page isn't available", no redirect. Verified
+`@heejin` is her (verified badge, ARTMS affiliation, followed by
+`official_artms`, same profile picture) before touching anything.
+
+Directory naming is forced from **our own tracked profile name**, not derived
+from Instagram's live username (see `gdl_command()` in `gdl-sync.py`) — so
+updating the URL alone would have started a brand-new `heejin/` directory
+tree alongside the existing `0ct0ber19/` one, splitting one person into two
+profiles. Fixed by migrating the existing archive instead of leaving it
+stale:
+
+- `0ct0ber19` → `heejin`, `0ct0ber19 - reels` → `heejin - reels`,
+  `story - 0ct0ber19` → `story - heejin`, and both her highlight directories
+  — 3,353 files total, done directly on the NAS (`ana-nas.lan.1qaz.ca`,
+  `/volume1/rslsync/sync/Instagram-archive/archives`), not via `gdl-sync.py`.
+- Only files whose embedded `{username}` token was **exactly** `0ct0ber19`
+  were renamed — matched as `_0ct0ber19 - ` (dated stem) or `^0ct0ber19 - `
+  (the older undated highlight naming) or the bare `0ct0ber19.<ext>` profile
+  picture, never a substring match. 7 files inside her own directories were
+  correctly left untouched: real collab posts (`chuuo3o`, `findyourmapp`)
+  physically stored there but truly owned by someone else — see "Where a
+  shared reel lands" above for why that happens at all.
+- Verified by content after each `rename()`, not exit code — this volume can
+  report a rename as failed when it actually succeeded (see
+  `instaarchive-deployment` in project memory). Every directory came back
+  with zero missing targets and zero leftover old names.
+- `docs/artms-instagram-accounts.txt` and `~/gdl/artms_account_links.txt`
+  updated to the new URL. The live site picked up the rename immediately, no
+  cache-bust needed — the archive index invalidates on directory mtime, which
+  a rename changes.
+- **Not changed:** the skip-archive DB (`artms.db`) keys purely on
+  `instagram_<media_id>`, no username involved, so it needed nothing. The
+  per-source `state.json` timestamps *are* keyed by URL, though, so `heejin`'s
+  entries look "never seeded" to `gdl-sync.py` now — the next run against her
+  will do one seeding listing pass to catch up, same as any newly added
+  profile. Cheap, and expected.
+
+If this happens again for another tracked account: confirm the new handle is
+really the same person before touching anything (verified badge + a mutual
+signal like "Followed by official_artms" + matching profile picture is
+usually enough), then this section is the template.
+
 ## Safety net: a global gallery-dl config
 
 `~/.config/gallery-dl/config.json` on `mattellite` exists so that a **plain
diff --git a/docs/artms-instagram-accounts.txt b/docs/artms-instagram-accounts.txt
index 148e8a4..c489cf5 100644
--- a/docs/artms-instagram-accounts.txt
+++ b/docs/artms-instagram-accounts.txt
@@ -1,4 +1,4 @@
-https://www.instagram.com/0ct0ber19/
+https://www.instagram.com/heejin/
 https://www.instagram.com/kimxxlip/
 https://www.instagram.com/withaseul/
 https://www.instagram.com/cher_ryppo/