diff --git a/src/app/api/v1/quotes/[id]/assistant/run/route.test.ts b/src/app/api/v1/quotes/[id]/assistant/run/route.test.ts
index 452948c..b24c9dc 100644
--- a/src/app/api/v1/quotes/[id]/assistant/run/route.test.ts
+++ b/src/app/api/v1/quotes/[id]/assistant/run/route.test.ts
@@ -6,6 +6,7 @@ vi.mock("@/lib/server/quote-assistant-service", () => ({
   fillQuote: (...a: unknown[]) => fillQuote(...a),
   QUOTE_NOT_OPEN_ERROR_PREFIX: "quote is not open",
   AI_DISABLED_ERROR: "AI is disabled in settings",
+  NOT_SET_UP_ERROR: "Quote assistant is not set up yet",
 }));
 
 const getBrowserSessionUser = vi.fn();
@@ -83,6 +84,16 @@ describe("POST /api/v1/quotes/[id]/assistant/run", () => {
     expect(await res.json()).toEqual({ error: "AI is disabled in settings" });
   });
 
+  it("409s when the migration hasn't run yet", async () => {
+    fillQuote.mockResolvedValue({
+      quoteId: "q1", filled: 0, unmatched: 0, skipped: 0,
+      error: "Quote assistant is not set up yet",
+    });
+    const res = await POST(makeReq(), ctx);
+    expect(res.status).toBe(409);
+    expect(await res.json()).toEqual({ error: "Quote assistant is not set up yet" });
+  });
+
   it("returns 200 with the result when the AI call failed", async () => {
     const result = { quoteId: "q1", filled: 0, unmatched: 0, skipped: 0, error: "AI call failed: timeout" };
     fillQuote.mockResolvedValue(result);
diff --git a/src/app/api/v1/quotes/[id]/assistant/run/route.ts b/src/app/api/v1/quotes/[id]/assistant/run/route.ts
index c80e344..5712136 100644
--- a/src/app/api/v1/quotes/[id]/assistant/run/route.ts
+++ b/src/app/api/v1/quotes/[id]/assistant/run/route.ts
@@ -3,6 +3,7 @@ import { getBrowserSessionUser } from "@/lib/server/browser-session";
 import {
   AI_DISABLED_ERROR,
   fillQuote,
+  NOT_SET_UP_ERROR,
   QUOTE_NOT_OPEN_ERROR_PREFIX,
 } from "@/lib/server/quote-assistant-service";
 
@@ -15,8 +16,8 @@ import {
  *
  * Auth: browser session (PB token forwarded in `Authorization`).
  *
- * Response: the `FillQuoteResult`. 409 when the quote isn't open or the AI
- * is switched off. An AI-call failure is not an HTTP error: it comes back
+ * Response: the `FillQuoteResult`. 409 when the quote isn't open, the AI
+ * is switched off, or the quote-assistant migration hasn't run yet. An AI-call failure is not an HTTP error: it comes back
  * as 200 with `error` set and the failed lines marked on the quote.
  */
 export const runtime = "nodejs";
@@ -37,7 +38,8 @@ export async function POST(
 
     if (
       result.error.startsWith(QUOTE_NOT_OPEN_ERROR_PREFIX) ||
-      result.error === AI_DISABLED_ERROR
+      result.error === AI_DISABLED_ERROR ||
+      result.error === NOT_SET_UP_ERROR
     ) {
       return NextResponse.json({ error: result.error }, { status: 409 });
     }
diff --git a/src/lib/server/quote-assistant-service.test.ts b/src/lib/server/quote-assistant-service.test.ts
index 3c78314..6124053 100644
--- a/src/lib/server/quote-assistant-service.test.ts
+++ b/src/lib/server/quote-assistant-service.test.ts
@@ -9,6 +9,8 @@ const store = {
   updates: [] as { id: string; patch: Record<string, unknown> }[],
   failUpdateFor: new Set<string>(),
   supplierLoads: 0,
+  /** Field names PB reports for `quote_items` (the migration adds ai_fill). */
+  quoteItemFields: ["description", "ai_fill"],
 };
 const events: string[] = [];
 const actors: { name?: string; source?: string; ignoreRequestUser?: boolean }[] = [];
@@ -35,6 +37,12 @@ function listItems(opts: { filter?: string; sort?: string; expand?: string }) {
 }
 
 const pb = {
+  collections: {
+    getOne: async (name: string) => ({
+      name,
+      fields: store.quoteItemFields.map((f) => ({ name: f })),
+    }),
+  },
   collection(name: string) {
     if (name === "quotes") {
       return {
@@ -107,7 +115,9 @@ import {
   boundRunErrors,
   fillQuote,
   getAssistantCounts,
+  NOT_SET_UP_ERROR,
   QUOTE_NOT_OPEN_ERROR_PREFIX,
+  resetAiFillFieldCheck,
   QUOTE_MAX_LINES,
   runAssistantTick,
   TICK_MAX_LINES,
@@ -204,6 +214,8 @@ beforeEach(() => {
   store.updates = [];
   store.failUpdateFor.clear();
   store.supplierLoads = 0;
+  store.quoteItemFields = ["description", "ai_fill"];
+  resetAiFillFieldCheck();
   events.length = 0;
   actors.length = 0;
   seq = 0;
@@ -219,6 +231,20 @@ beforeEach(() => {
 });
 
 describe("fillQuote", () => {
+  it("refuses to write anything until the migration has added quote_items.ai_fill", async () => {
+    store.quoteItemFields = ["description"];
+    addQuote("q1");
+    addItem("q1", { id: "a" });
+    const { deps, decide } = makeDeps();
+
+    const r = await fillQuote("q1", { deps });
+
+    expect(r.error).toBe(NOT_SET_UP_ERROR);
+    expect(decide).not.toHaveBeenCalled();
+    expect(store.updates).toEqual([]);
+    expect(store.items.get("a")!.cost_price).toBe(0);
+  });
+
   it("fills a matched line and records no_match for an unmatched one", async () => {
     addQuote("q1");
     const a = addItem("q1", { id: "a" });
diff --git a/src/lib/server/quote-assistant-service.ts b/src/lib/server/quote-assistant-service.ts
index 49a61c8..f0950e7 100644
--- a/src/lib/server/quote-assistant-service.ts
+++ b/src/lib/server/quote-assistant-service.ts
@@ -41,6 +41,7 @@ import { escapeForPbString } from "@/lib/server/price-list-match";
 import { loadSuppliersById } from "@/lib/server/item-intel-service";
 import { isAiFillPending } from "@/lib/quote-assistant-review";
 import type { Quote, QuoteAssistantRunSummary, QuoteItem } from "@/lib/types";
+import type { AdminPb } from "@/lib/server/quote-assistant-shortlist";
 
 export interface AssistantDeps {
   decide?: (input: DecideInput) => Promise<DecideResult>;
@@ -73,8 +74,35 @@ const MAX_SUMMARY_ERROR_CHARS = 300;
 export const QUOTE_NOT_OPEN_ERROR_PREFIX = "quote is not open";
 /** `FillQuoteResult.error` when the global AI switch is off (409). */
 export const AI_DISABLED_ERROR = "AI is disabled in settings";
+/** `FillQuoteResult.error` when the live PB has no `quote_items.ai_fill` yet (409). */
+export const NOT_SET_UP_ERROR =
+  "Quote assistant is not set up yet: run `npm run pb:migrate:quote-assistant` against PocketBase first";
 const COUNT_CHUNK = 50;
 
+let aiFillFieldConfirmed = false;
+
+/**
+ * PocketBase silently drops unknown fields on update. Without the
+ * `quote_items.ai_fill` field (added by the migration) the AI's prices would
+ * land with no purple marker and no notes, so refuse to write until it exists.
+ * A positive answer is cached for the life of the process.
+ */
+async function hasAiFillField(pb: AdminPb): Promise<boolean> {
+  if (aiFillFieldConfirmed) return true;
+  const collection = (await pb.collections.getOne("quote_items")) as {
+    fields?: Array<{ name: string }>;
+    schema?: Array<{ name: string }>;
+  };
+  const fields = collection.fields ?? collection.schema ?? [];
+  aiFillFieldConfirmed = fields.some((f) => f.name === "ai_fill");
+  return aiFillFieldConfirmed;
+}
+
+/** Test hook: forget the cached schema check. */
+export function resetAiFillFieldCheck(): void {
+  aiFillFieldConfirmed = false;
+}
+
 /** Lines the AI may ever look at: nothing priced, edited or processed. */
 const OPEN_LINE_FILTER =
   'is_processed = false && cost_price = 0 && selling_price = 0 && user_edited = false && (pricing_source = "" || pricing_source = "ai_email") && moved_to_quote = ""';
@@ -121,6 +149,10 @@ export async function fillQuote(
   // token, which the audit hook would otherwise credit instead of the AI.
   return runWithAuditActor({ name: actorName, source: "agent", ignoreRequestUser: true }, async () => {
     const pb = await getAdminPocketBase();
+    if (!(await hasAiFillField(pb))) {
+      result.error = NOT_SET_UP_ERROR;
+      return result;
+    }
     const quote = await pb.collection("quotes").getOne<Quote>(quoteId);
     if (quote.is_template) {
       result.error = `${QUOTE_NOT_OPEN_ERROR_PREFIX} (template)`;