diff --git a/src/lib/proxyEgress.ts b/src/lib/proxyEgress.ts
index c67243f60d..aa2f3a4ea1 100644
--- a/src/lib/proxyEgress.ts
+++ b/src/lib/proxyEgress.ts
@@ -316,3 +316,73 @@ export async function validateProxyPool(deps?: {
 
   return report;
 }
+
+export interface DistributionPlan {
+  assignments: Array<{ connectionId: string; account: string; proxyId: string }>;
+  unassigned: Array<{ connectionId: string; account: string }>;
+  sharingRisk: boolean;
+  note: string;
+}
+
+/**
+ * PURE: plan a 1-proxy-per-connection assignment so no two accounts of the same
+ * rotation group share an egress IP (the codex anomaly trigger). Default is
+ * strict 1:1 — extras are left UNASSIGNED (better unrouted than sharing an IP).
+ * allowSharing=true round-robins instead, flagging sharingRisk.
+ */
+export function planProxyDistribution(
+  connections: Array<{ id: string; account?: string }>,
+  liveProxyIds: string[],
+  opts: { allowSharing?: boolean } = {}
+): DistributionPlan {
+  const assignments: DistributionPlan["assignments"] = [];
+  const unassigned: DistributionPlan["unassigned"] = [];
+  let sharingRisk = false;
+
+  connections.forEach((c, i) => {
+    const account = c.account || c.id.slice(0, 8);
+    if (liveProxyIds.length === 0) {
+      unassigned.push({ connectionId: c.id, account });
+      return;
+    }
+    if (opts.allowSharing) {
+      assignments.push({ connectionId: c.id, account, proxyId: liveProxyIds[i % liveProxyIds.length] });
+    } else if (i < liveProxyIds.length) {
+      assignments.push({ connectionId: c.id, account, proxyId: liveProxyIds[i] });
+    } else {
+      unassigned.push({ connectionId: c.id, account });
+    }
+  });
+
+  if (opts.allowSharing && liveProxyIds.length < connections.length) sharingRisk = true;
+
+  const note =
+    liveProxyIds.length === 0
+      ? "No live proxies available — add working proxies before distributing."
+      : liveProxyIds.length < connections.length && !opts.allowSharing
+        ? `Only ${liveProxyIds.length} live proxies for ${connections.length} accounts — ${unassigned.length} left unassigned (avoid shared-IP anomaly).`
+        : "1 distinct proxy per account.";
+
+  return { assignments, unassigned, sharingRisk, note };
+}
+
+/**
+ * Apply a distribution plan: assign each proxy to its connection (account scope).
+ */
+export async function applyProxyDistribution(
+  plan: DistributionPlan,
+  deps?: { assign?: (connectionId: string, proxyId: string) => Promise<void> }
+): Promise<{ applied: number }> {
+  const assign =
+    deps?.assign ??
+    (async (connectionId: string, proxyId: string) => {
+      const { assignProxyToScope } = await import("./db/proxies");
+      await assignProxyToScope("account", connectionId, proxyId);
+    });
+  let applied = 0;
+  for (const a of plan.assignments) {
+    await assign(a.connectionId, a.proxyId);
+    applied++;
+  }
+  return { applied };
+}
diff --git a/tests/unit/proxy-egress-visibility.test.ts b/tests/unit/proxy-egress-visibility.test.ts
index 7ed83550fa..86d11905e0 100644
--- a/tests/unit/proxy-egress-visibility.test.ts
+++ b/tests/unit/proxy-egress-visibility.test.ts
@@ -24,7 +24,7 @@ const {
   _setEgressProbeForTests: (fn: any) => void;
   clearEgressCache: () => void;
 };
-const { validateProxyPool } = egress as any;
+const { validateProxyPool, planProxyDistribution, applyProxyDistribution } = egress as any;
 
 test("resolveEgressIp returns the probed IP and caches by proxy URL", async () => {
   clearEgressCache();
@@ -133,3 +133,58 @@ test("validateProxyPool marks live proxies active and dead proxies error", async
 
   _setEgressProbeForTests(null);
 });
+
+test("planProxyDistribution: strict 1:1, extras left unassigned (no shared IP)", () => {
+  const plan = planProxyDistribution(
+    [{ id: "c1", account: "a1" }, { id: "c2", account: "a2" }, { id: "c3", account: "a3" }],
+    ["p1", "p2"]
+  );
+  assert.equal(plan.assignments.length, 2);
+  assert.deepEqual(plan.assignments.map((a: any) => a.proxyId), ["p1", "p2"]);
+  assert.equal(plan.unassigned.length, 1, "c3 has no proxy → unassigned, not sharing");
+  assert.equal(plan.unassigned[0].connectionId, "c3");
+  assert.equal(plan.sharingRisk, false);
+});
+
+test("planProxyDistribution: enough proxies → 1 distinct per account", () => {
+  const plan = planProxyDistribution(
+    [{ id: "c1", account: "a1" }, { id: "c2", account: "a2" }],
+    ["p1", "p2", "p3"]
+  );
+  assert.equal(plan.assignments.length, 2);
+  assert.equal(plan.unassigned.length, 0);
+  assert.match(plan.note, /1 distinct proxy/);
+});
+
+test("planProxyDistribution: allowSharing round-robins and flags sharingRisk", () => {
+  const plan = planProxyDistribution(
+    [{ id: "c1", account: "a1" }, { id: "c2", account: "a2" }, { id: "c3", account: "a3" }],
+    ["p1", "p2"],
+    { allowSharing: true }
+  );
+  assert.equal(plan.assignments.length, 3);
+  assert.deepEqual(plan.assignments.map((a: any) => a.proxyId), ["p1", "p2", "p1"]);
+  assert.equal(plan.sharingRisk, true);
+});
+
+test("planProxyDistribution: no live proxies → all unassigned with guidance", () => {
+  const plan = planProxyDistribution([{ id: "c1", account: "a1" }], []);
+  assert.equal(plan.assignments.length, 0);
+  assert.equal(plan.unassigned.length, 1);
+  assert.match(plan.note, /No live proxies/);
+});
+
+test("applyProxyDistribution assigns each proxy to its connection", async () => {
+  const calls: Array<[string, string]> = [];
+  const plan = planProxyDistribution(
+    [{ id: "c1", account: "a1" }, { id: "c2", account: "a2" }],
+    ["p1", "p2"]
+  );
+  const res = await applyProxyDistribution(plan, {
+    assign: async (connectionId: string, proxyId: string) => {
+      calls.push([connectionId, proxyId]);
+    },
+  });
+  assert.equal(res.applied, 2);
+  assert.deepEqual(calls, [["c1", "p1"], ["c2", "p2"]]);
+});