diff --git a/src/objects/contract-version.hook.ts b/src/objects/contract-version.hook.ts
new file mode 100644
index 0000000..9077b3e
--- /dev/null
+++ b/src/objects/contract-version.hook.ts
@@ -0,0 +1,87 @@
+import type { Hook, HookContext } from '@objectstack/spec/data';
+import type { HookApi } from './_hook-api.js';
+
+/**
+ * At most one current version per contract (DESIGN.md §03 `clm_contract_version`,
+ * ruled 1A + 2A on #96).
+ *
+ * `is_current` is "the version negotiation is currently on" — singular, and
+ * what the `approved → signing` guard in `contract.hook.ts` reads. A new
+ * version is current by default (`defaultValue: true` on the field), so this
+ * hook is what keeps the flag exclusive, on every door alike — the version
+ * form, REST, flows, MCP:
+ *
+ * - a row that is current after the write un-marks every other current row of
+ *   the same contract;
+ * - a `final_signed` row does not take the flag from a negotiation version: it
+ *   keeps `is_current: true` only while it is the contract's ONLY version (the
+ *   F16 backfill files exactly that), and is otherwise stored `false`, leaving
+ *   its siblings alone. That is what keeps `signing → approved` re-enterable
+ *   after a failed signing round: the clean version stays current whoever
+ *   files the executed copy — F7 writes it `false` explicitly, and a records
+ *   clerk adding one through the version form gets the same answer.
+ *
+ * Nothing is promoted when a row is un-ticked: "no current version" is a state
+ * the signing guard already refuses with its own message.
+ *
+ * `afterInsert` / `afterUpdate`, so the caller's own write is judged first and
+ * a refused write never un-marks anything; the decision is taken on the
+ * COMMITTED row, re-read here. `runAs: 'system'`: requesters and records hold
+ * create but not edit on versions (DESIGN.md §04), so un-marking a sibling — or
+ * storing `false` on the row just created — must be a system write. Same
+ * precedent as `deviation_gate` in `contract.hook.ts`. The hook's own writes
+ * set `is_current: false` and therefore return at the first check, so it does
+ * not recurse.
+ *
+ * As in `contract.hook.ts`, everything the handler uses lives inside it: the
+ * build lowers the body into a sandbox with no module scope.
+ */
+const contractVersionCurrent: Hook = {
+  name: 'contract_version_current',
+  object: 'clm_contract_version',
+  events: ['afterInsert', 'afterUpdate'],
+  priority: 300,
+  runAs: 'system',
+  description: 'Keep at most one current version per contract: a version that becomes current un-marks the others; a final signed copy keeps the flag only when it is the contract\'s only version.',
+  handler: async (ctx: HookContext) => {
+    const { event, input } = ctx;
+    const previous = ctx.previous ?? {};
+    // An update that touches none of the three inputs cannot change who is
+    // current; skip the reads.
+    if (event === 'afterUpdate' && input.is_current === undefined && input.kind === undefined && input.contract === undefined) return;
+
+    const result = (ctx.result ?? {}) as Record<string, unknown>;
+    const id = event === 'afterInsert' ? result.id : previous.id;
+    if (typeof id !== 'string' || !id) return;
+    const api = ctx.api as HookApi | undefined;
+    if (!api) return;
+
+    const row = await api.object('clm_contract_version').findOne({
+      where: { id },
+      fields: ['id', 'contract', 'kind', 'is_current'],
+    });
+    if (!row || row.is_current !== true) return;
+    const contractId = row.contract;
+    if (typeof contractId !== 'string' || !contractId) return;
+
+    if (row.kind === 'final_signed') {
+      const versions = await api.object('clm_contract_version').count({ where: { contract: contractId } });
+      if (versions > 1) {
+        await api.object('clm_contract_version').update({ id, is_current: false }, { where: { id } });
+      }
+      return;
+    }
+
+    const others = await api.object('clm_contract_version').find({
+      where: { contract: contractId, is_current: true, id: { $ne: id } },
+      fields: ['id'],
+      top: 200,
+    });
+    for (const other of others) {
+      if (typeof other.id !== 'string' || other.id === id) continue;
+      await api.object('clm_contract_version').update({ id: other.id, is_current: false }, { where: { id: other.id } });
+    }
+  },
+};
+
+export default [contractVersionCurrent];
diff --git a/src/objects/contract-version.object.ts b/src/objects/contract-version.object.ts
index b570b5f..290c655 100644
--- a/src/objects/contract-version.object.ts
+++ b/src/objects/contract-version.object.ts
@@ -9,7 +9,8 @@ import { ObjectSchema, Field } from '@objectstack/spec/data';
  *
  * Two versions gate the contract's state machine: `approved → signing` needs
  * a current `clean` version, and `signing → active` needs a `final_signed`
- * one (`contract.hook.ts`). `display_name` is a stored mirror ("v<n> · <kind>")
+ * one (`contract.hook.ts`). At most one version of a contract is current
+ * (`contract-version.hook.ts`). `display_name` is a stored mirror ("v<n> · <kind>")
  * stamped by `mirror.hook.ts` — a stored title, never a formula, so the record
  * is searchable and pickable.
  */
@@ -83,8 +84,11 @@ export const ContractVersion = ObjectSchema.create({
     is_current: Field.boolean({
       label: 'Current',
       group: 'version',
-      defaultValue: false,
-      // The approved → signing guard in contract.hook.ts reads this flag.
+      // A new version is current by default; `contract-version.hook.ts` keeps
+      // the flag to one row per contract and never moves it onto a
+      // `final_signed` copy while other versions exist. The approved → signing
+      // guard in contract.hook.ts reads this flag.
+      defaultValue: true,
       description: 'The version negotiation is currently on. A contract can go to signing only once its current version is a clean copy.',
     }),
 
diff --git a/src/objects/hooks.ts b/src/objects/hooks.ts
index e152841..f208b69 100644
--- a/src/objects/hooks.ts
+++ b/src/objects/hooks.ts
@@ -1,6 +1,7 @@
 import type { Hook } from '@objectstack/spec/data';
 
 import contractHooks from './contract.hook.js';
+import contractVersionHooks from './contract-version.hook.js';
 import mirrorHooks from './mirror.hook.js';
 
 /**
@@ -8,4 +9,4 @@ import mirrorHooks from './mirror.hook.js';
  * apart from `index.ts` on purpose: that barrel is spread into `objects` via
  * `Object.values()`, and a hook array in it would be registered as an object.
  */
-export const allHooks: Hook[] = [...contractHooks, ...mirrorHooks];
+export const allHooks: Hook[] = [...contractHooks, ...contractVersionHooks, ...mirrorHooks];