diff --git a/TUBCO_SETUP.md b/TUBCO_SETUP.md
index ce7501f..059acb0 100644
--- a/TUBCO_SETUP.md
+++ b/TUBCO_SETUP.md
@@ -2,6 +2,9 @@
 
 Use this runbook when you want to set up or rebuild the TUBCO customer deployment from scratch.
 
+Maintenance policy reference:
+- [docs/TUBCO_MAINTENANCE_POLICY.md](/Users/bostame/Documents/workdock-platform/docs/TUBCO_MAINTENANCE_POLICY.md)
+
 This is the customer-specific path. Normal product work still happens on:
 - `develop`
 - `main`
@@ -171,6 +174,13 @@ For TUBCO:
   - security updates
   - UI improvements
 
+Important:
+- keep TUBCO on the old TUBCO database schema
+- do not solve customer drift by importing the newer product schema into TUBCO
+- if a deployed TUBCO environment starts failing on unknown non-null columns, verify DB/schema alignment first
+- for the full maintenance rules, use:
+  - [docs/TUBCO_MAINTENANCE_POLICY.md](/Users/bostame/Documents/workdock-platform/docs/TUBCO_MAINTENANCE_POLICY.md)
+
 Do not deploy TUBCO from:
 - `develop`
 - `main`
diff --git a/docs/TUBCO_MAINTENANCE_POLICY.md b/docs/TUBCO_MAINTENANCE_POLICY.md
new file mode 100644
index 0000000..13ff08a
--- /dev/null
+++ b/docs/TUBCO_MAINTENANCE_POLICY.md
@@ -0,0 +1,136 @@
+# TUBCO Maintenance Policy
+
+Use this document whenever we maintain the TUBCO customer line.
+
+This is the rulebook for TUBCO. It is intentionally stricter than normal product work.
+
+## Goal
+
+TUBCO stays on its own older customer baseline.
+
+That means:
+- keep the older TUBCO application behavior
+- keep the older TUBCO database schema
+- only cherry-pick approved fixes
+- do not quietly turn TUBCO into the newer product
+
+## Source of truth
+
+TUBCO delivery happens from:
+- `release/tubco-v1`
+
+Normal product work happens on:
+- `develop`
+- `main`
+
+Do not deploy TUBCO from:
+- `develop`
+- `main`
+
+## Core maintenance rules
+
+For TUBCO, we may backport only:
+- bug fixes
+- security fixes
+- carefully approved UX improvements
+- required operational fixes for the customer environment
+
+For TUBCO, we do not backport by default:
+- new product workflows
+- new approval/account-rule systems
+- schema expansions from the newer product
+- general feature growth unless explicitly approved
+
+## Database rule
+
+TUBCO must use the old TUBCO schema.
+
+This is the most important rule.
+
+If the code stays old but the database is newer, old TUBCO flows can fail with database errors such as:
+- missing values for newer non-null columns
+- forms saving rows that the old code does not know how to populate
+
+If we see errors like:
+- `null value in column ... violates not-null constraint`
+
+then first verify whether the TUBCO environment is still using the old schema.
+
+Do not solve this by default with:
+- broad schema compatibility backports
+- importing the newer product data model into TUBCO
+
+That would move TUBCO toward the new product instead of preserving the customer baseline.
+
+## LAN server rule
+
+TUBCO is hosted on our local LAN server.
+
+Before deploying any TUBCO fix, verify:
+- the server is running `release/tubco-v1`
+- the environment points to the intended old TUBCO database
+- no newer product migrations were applied there by mistake
+
+If the LAN server is connected to a newer migrated database, code-only fixes may not be enough.
+
+In that case, the correct options are:
+1. repoint TUBCO to the old TUBCO database
+2. or restore the database to the old TUBCO schema
+
+## Safe TUBCO release workflow
+
+1. start from:
+   - `release/tubco-v1`
+2. implement only the approved fix
+3. keep the database model old unless there is explicit customer approval to change it
+4. test the affected flow
+5. deploy only to the LAN-hosted TUBCO environment
+6. do not run newer product migrations on that environment
+
+## Cherry-pick rule
+
+When a fix exists on another branch:
+- inspect the commit carefully
+- cherry-pick only if it does not pull in newer product behavior or newer schema assumptions
+
+If a fix depends on the newer schema:
+- stop
+- rework it as a TUBCO-only fix
+- or do not ship it
+
+## Operational checklist before deploying a TUBCO fix
+
+Check all of these:
+- branch is `release/tubco-v1`
+- worktree is clean
+- fix is limited to the approved TUBCO scope
+- no new-product migrations are included
+- no new-product workflows are included
+- LAN server target is the intended TUBCO environment
+- database is the old TUBCO schema
+
+## Example warning signs
+
+Pause and verify immediately if you see:
+- approval-related fields appearing in old TUBCO flows
+- new account-rule behavior on TUBCO
+- migration files copied from the product branch
+- database errors mentioning columns unknown to the old branch
+
+Those usually indicate code/schema drift.
+
+## Decision rule
+
+If there is a conflict between:
+- shipping a quick fix
+- and keeping TUBCO on the old customer baseline
+
+choose the old customer baseline first.
+
+We only widen the TUBCO schema or behavior if that change is explicitly intended for TUBCO.
+
+## Related documents
+
+- [TUBCO_SETUP.md](/Users/bostame/Documents/workdock-platform/TUBCO_SETUP.md)
+- [DEPLOYMENT.md](/Users/bostame/Documents/workdock-platform/DEPLOYMENT.md)
+- [CONTRIBUTING.md](/Users/bostame/Documents/workdock-platform/CONTRIBUTING.md)