diff --git a/desktop/src/features/agents/ui/usePersonaActions.test.mjs b/desktop/src/features/agents/ui/usePersonaActions.test.mjs
new file mode 100644
index 0000000000..2a93e23bf3
--- /dev/null
+++ b/desktop/src/features/agents/ui/usePersonaActions.test.mjs
@@ -0,0 +1,192 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+import { toast } from "sonner";
+import { resolveLatestPersonaToEdit } from "./usePersonaActions.ts";
+import { runAgentSaveCoordinator } from "./agentSaveCoordinator.ts";
+
+// ── P1-2 seam: Agents-library edit route must rebind ctx to the latest persona ─
+//
+// Thufir's IMPORTANT finding: the drift guard lives in the coordinator, but on
+// the Agents-library route `ctx.definition` was fed the open-time snapshot, so
+// a same-ID refresh never reached the guard and the clobber stayed reachable.
+// `resolveLatestPersonaToEdit` closes that seam by re-deriving the live entity
+// by ID. These tests exercise the REAL rebind wired into the REAL coordinator:
+// reverting the rebind (returning the stored snapshot) makes the newer
+// `updatedAt` invisible, the guard sees equality, and the write proceeds —
+// which fails the abort assertions below.
+
+function makeDefinition(overrides = {}) {
+  return {
+    id: "def-1",
+    displayName: "Alice",
+    avatarUrl: "",
+    systemPrompt: "Be helpful.",
+    runtime: "goose",
+    model: "gpt-4o",
+    provider: null,
+    isBuiltIn: false,
+    isActive: true,
+    namePool: [],
+    envVars: {},
+    respondTo: null,
+    respondToAllowlist: [],
+    parallelism: null,
+    createdAt: "2025-01-01T00:00:00Z",
+    updatedAt: "2025-01-01T00:00:00Z",
+    ...overrides,
+  };
+}
+
+function makePersonaInput(overrides = {}) {
+  return {
+    id: "def-1",
+    displayName: "Alice-edited",
+    systemPrompt: "Be helpful.",
+    avatarUrl: "",
+    runtime: "goose",
+    model: "gpt-4o",
+    provider: undefined,
+    namePool: [],
+    envVars: {},
+    ...overrides,
+  };
+}
+
+function captureToasts() {
+  const captured = [];
+  const original = {
+    success: toast.success,
+    warning: toast.warning,
+    error: toast.error,
+  };
+  for (const kind of ["success", "warning", "error"]) {
+    toast[kind] = (message) => captured.push({ kind, message });
+  }
+  return { captured, restore: () => Object.assign(toast, original) };
+}
+
+test("test_resolve_latest_persona_rebinds_to_refreshed_entity_by_id", () => {
+  const snapshot = makeDefinition({ updatedAt: "2025-01-01T00:00:00Z" });
+  const refreshed = makeDefinition({
+    updatedAt: "2025-06-01T00:00:00Z",
+    systemPrompt: "Concurrently revised.",
+  });
+
+  const resolved = resolveLatestPersonaToEdit(snapshot, [refreshed]);
+  assert.equal(
+    resolved.updatedAt,
+    "2025-06-01T00:00:00Z",
+    "must rebind to the live entity so ctx advances with the store",
+  );
+});
+
+test("test_resolve_latest_persona_falls_back_to_snapshot_when_deleted", () => {
+  const snapshot = makeDefinition();
+  // Persona vanished from query data (deleted while editing).
+  assert.equal(
+    resolveLatestPersonaToEdit(snapshot, []),
+    snapshot,
+    "must fall back to the stored snapshot when the id is gone",
+  );
+  assert.equal(resolveLatestPersonaToEdit(null, [makeDefinition()]), null);
+});
+
+test("test_agents_route_concurrent_definition_edit_aborts_before_any_write", async () => {
+  // The full seam: user opens Alice from the Agents library (snapshot at T0,
+  // captured as the seed-time updatedAt). A concurrent writer revises the same
+  // definition to T1; personasQuery refreshes. The dialog rebinds ctx via
+  // resolveLatestPersonaToEdit, then the user submits a definition edit.
+  const cap = captureToasts();
+  try {
+    const snapshot = makeDefinition({ updatedAt: "2025-01-01T00:00:00Z" });
+    const seededUpdatedAt = snapshot.updatedAt; // captured at seed time
+
+    const refreshed = makeDefinition({ updatedAt: "2025-06-01T00:00:00Z" });
+    const ctxDefinition = resolveLatestPersonaToEdit(snapshot, [refreshed]);
+
+    let definitionWrites = 0;
+    const result = await runAgentSaveCoordinator({
+      ctx: { kind: "definition-only", definition: ctxDefinition },
+      personaInput: makePersonaInput(),
+      agentInput: null,
+      policySets: [],
+      expectedDefinitionUpdatedAt: seededUpdatedAt,
+      updatePersona: async () => {
+        definitionWrites++;
+      },
+      updatePersonaAndPublish: async () => {
+        definitionWrites++;
+        return { publicationStatus: "published" };
+      },
+      updateManagedAgent: async () => ({ agent: null, profileSyncError: null }),
+      setAutoRestart: async () => {},
+      setStartOnAppLaunch: async () => {},
+      refetchStores: async () => ({ persona: refreshed, agent: null }),
+      onDone: () => {},
+    });
+
+    assert.equal(
+      result,
+      false,
+      "drift must abort the save (dialog stays open)",
+    );
+    assert.equal(
+      definitionWrites,
+      0,
+      "ZERO definition writes when ctx rebinds to a newer revision than the seed",
+    );
+    const errors = cap.captured.filter((c) => c.kind === "error");
+    assert.equal(errors.length, 1, "one concurrent-edit error toast");
+    assert.match(
+      errors[0].message,
+      /changed while you were editing/i,
+      "must surface concurrent-edit messaging",
+    );
+  } finally {
+    cap.restore();
+  }
+});
+
+test("test_agents_route_no_concurrent_edit_proceeds_to_write", async () => {
+  // No concurrent revision: the refreshed entity matches the seed revision, so
+  // the guard does not fire and the definition write proceeds.
+  const cap = captureToasts();
+  try {
+    const snapshot = makeDefinition({ updatedAt: "2025-01-01T00:00:00Z" });
+    const ctxDefinition = resolveLatestPersonaToEdit(snapshot, [snapshot]);
+
+    let definitionWrites = 0;
+    const result = await runAgentSaveCoordinator({
+      ctx: { kind: "definition-only", definition: ctxDefinition },
+      personaInput: makePersonaInput({ displayName: "Alice-edited" }),
+      agentInput: null,
+      policySets: [],
+      expectedDefinitionUpdatedAt: snapshot.updatedAt,
+      updatePersona: async () => {
+        definitionWrites++;
+      },
+      updatePersonaAndPublish: async () => {
+        definitionWrites++;
+        return { publicationStatus: "published" };
+      },
+      updateManagedAgent: async () => ({ agent: null, profileSyncError: null }),
+      setAutoRestart: async () => {},
+      setStartOnAppLaunch: async () => {},
+      refetchStores: async () => ({
+        persona: makeDefinition({ displayName: "Alice-edited" }),
+        agent: null,
+      }),
+      onDone: () => {},
+    });
+
+    assert.equal(result, true, "no drift → save succeeds");
+    assert.equal(
+      definitionWrites,
+      1,
+      "definition write proceeds when no concurrent revision",
+    );
+  } finally {
+    cap.restore();
+  }
+});
diff --git a/desktop/src/features/agents/ui/usePersonaActions.ts b/desktop/src/features/agents/ui/usePersonaActions.ts
index 0693895742..05f4c3b4f7 100644
--- a/desktop/src/features/agents/ui/usePersonaActions.ts
+++ b/desktop/src/features/agents/ui/usePersonaActions.ts
@@ -65,6 +65,31 @@ import {
 
 type PersonaFeedbackSurface = "catalog" | "library";
 
+/**
+ * Resolve the persona to edit against the latest query data.
+ *
+ * `personaToEdit` stores the snapshot clicked at open time. A same-ID
+ * `personasQuery` refresh (a concurrent writer revising the definition) never
+ * rebinds that stored object, so passing it straight to the edit dialog as
+ * `ctx.definition` lets the stale full-replacement input clobber the newer
+ * writer's untouched fields. Re-derive the live entity by ID so `ctx` always
+ * advances with the store while the dialog's seed-time ref stays pinned — which
+ * is exactly what makes the coordinator's drift guard trip.
+ *
+ * Deleted-while-editing: when the ID vanishes from query data, fall back to the
+ * stored snapshot. Editing then still drift-guards (the snapshot's own
+ * `updatedAt` matches the seed ref, so a definition write proceeds against the
+ * last-known state) and closing/deleting stays reachable — less surprising than
+ * abruptly closing the dialog mid-edit.
+ */
+export function resolveLatestPersonaToEdit(
+  selected: AgentPersona | null,
+  personas: readonly AgentPersona[],
+): AgentPersona | null {
+  if (!selected) return null;
+  return personas.find((p) => p.id === selected.id) ?? selected;
+}
+
 export function usePersonaActions() {
   const queryClient = useQueryClient();
   const { activeCommunity } = useCommunities();
@@ -167,6 +192,15 @@ export function usePersonaActions() {
     [personas],
   );
 
+  // Re-derive the edited persona from the latest query data by ID so the edit
+  // dialog's `ctx.definition` advances when a concurrent writer revises the
+  // same definition. Without this, `personaToEdit` holds the open-time snapshot
+  // and the drift guard never trips on the Agents-library route.
+  const resolvedPersonaToEdit = React.useMemo(
+    () => resolveLatestPersonaToEdit(personaToEdit, personas),
+    [personaToEdit, personas],
+  );
+
   function clearFeedback(
     surface: PersonaFeedbackSurface = personaFeedbackSurface,
   ) {
@@ -585,7 +619,7 @@ export function usePersonaActions() {
     isPending,
     personaDialogState,
     setPersonaDialogState,
-    personaToEdit,
+    personaToEdit: resolvedPersonaToEdit,
     setPersonaToEdit,
     personaToDelete,
     setPersonaToDelete,