From bbc2843fdfaefc35d4fc187a177c06016241803a Mon Sep 17 00:00:00 2001
From: Daniel Roth <daniel_roth@hotmail.co.uk>
Date: Thu, 23 Jul 2026 12:38:39 +0000
Subject: [PATCH] =?UTF-8?q?feat(ara-projects):=20work-orders=20API=20?=
 =?UTF-8?q?=E2=80=94=20filters,=20keyset=20pagination,=20shared=20derivati?=
 =?UTF-8?q?ons=20(#419)?=
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GET /api/projects/[projectId]/work-orders serves one page of the admin
work-orders table: workstream / contractor / stage / overdue-only /
missing-required-evidence filters, keyset-paginated by work_order.id so a
cursor stays meaningful under any filter combination.

The rules stay in one place. Every derived filter is split at its AND, the
way #418's dashboard repository splits it, and the TypeScript half crosses
into SQL as data rather than as a re-implemented predicate:

  - overdue: buildStageLadders classifies the project's stages in JS and
    stageIdsByProgress("complete") hands the terminal ids to the query;
    SQL only counts forecast_end < asOf.
  - missing evidence: requiredEvidenceRequirementIds decides which
    requirement applies at which stage and hands over an explicit
    (stage_id, requirement_id) list.

Row badges come from toWorkOrderRow, which calls isOverdue /
progressOfWorkOrder / evidenceCompleteness directly, so the table and the
dashboard reconcile by construction.

Authz is canManageProject (internal + client-org). A contractor gets 403
rather than the whole programme; row scoping is a later issue.

Tests mock @/app/db/db and open no connection.
---
 .../[projectId]/work-orders/authorize.ts      |  63 +++
 .../[projectId]/work-orders/filters.test.ts   | 150 +++++++
 .../[projectId]/work-orders/filters.ts        | 204 +++++++++
 .../[projectId]/work-orders/queries.test.ts   | 209 +++++++++
 .../[projectId]/work-orders/queries.ts        | 421 ++++++++++++++++++
 .../[projectId]/work-orders/route.test.ts     | 194 ++++++++
 .../projects/[projectId]/work-orders/route.ts |  44 ++
 .../[projectId]/work-orders/rows.test.ts      | 150 +++++++
 .../projects/[projectId]/work-orders/rows.ts  | 135 ++++++
 9 files changed, 1570 insertions(+)
 create mode 100644 src/app/api/projects/[projectId]/work-orders/authorize.ts
 create mode 100644 src/app/api/projects/[projectId]/work-orders/filters.test.ts
 create mode 100644 src/app/api/projects/[projectId]/work-orders/filters.ts
 create mode 100644 src/app/api/projects/[projectId]/work-orders/queries.test.ts
 create mode 100644 src/app/api/projects/[projectId]/work-orders/queries.ts
 create mode 100644 src/app/api/projects/[projectId]/work-orders/route.test.ts
 create mode 100644 src/app/api/projects/[projectId]/work-orders/route.ts
 create mode 100644 src/app/api/projects/[projectId]/work-orders/rows.test.ts
 create mode 100644 src/app/api/projects/[projectId]/work-orders/rows.ts

diff --git a/src/app/api/projects/[projectId]/work-orders/authorize.ts b/src/app/api/projects/[projectId]/work-orders/authorize.ts
new file mode 100644
index 00000000..29f5ead4
--- /dev/null
+++ b/src/app/api/projects/[projectId]/work-orders/authorize.ts
@@ -0,0 +1,63 @@
+/**
+ * Request authorization for the work-orders endpoint (issue #419).
+ *
+ * Wiring only, mirroring `../workstreams/authorize.ts`: the session comes from
+ * NextAuth, the facts from the projects authz repository, and every *decision*
+ * from `@/lib/projects/authz` (#408). No permission rule is re-implemented here.
+ *
+ * A project the caller cannot see is reported as 404, never 403, so project
+ * existence does not leak outside its organisation.
+ *
+ * Scoping note: this endpoint is the **admin** table — internal and client-org
+ * members, per the issue's acceptance criteria — so it requires
+ * `canManageProject`. A contractor resolves a role on the project and would
+ * pass `canViewProject`, but must not see other contractors' work orders;
+ * narrowing the rows to their own assignments is a later issue, and until it
+ * lands the honest answer for a contractor is 403 rather than a table showing
+ * them the whole programme.
+ */
+import { getServerSession } from "next-auth";
+import { AuthOptions } from "@/app/api/auth/[...nextauth]/authOptions";
+import {
+  loadAuthzUser,
+  loadProjectAuthzFacts,
+} from "@/app/repositories/projects/authzRepository";
+import { canManageProject, canViewProject } from "@/lib/projects/authz";
+
+export type AuthorizeFailure = { error: string; status: 400 | 401 | 403 | 404 };
+
+export type AuthorizeResult =
+  | { ok: true; projectId: bigint }
+  | ({ ok: false } & AuthorizeFailure);
+
+/** Resolve the caller's standing on `projectIdParam` for the admin table. */
+export async function authorizeWorkOrdersRequest(
+  projectIdParam: string,
+): Promise<AuthorizeResult> {
+  const session = await getServerSession(AuthOptions);
+  if (!session?.user?.dbId) {
+    return { ok: false, error: "Unauthorised", status: 401 };
+  }
+
+  if (!/^\d+$/.test(projectIdParam)) {
+    return { ok: false, error: "Invalid project", status: 400 };
+  }
+  const projectId = BigInt(projectIdParam);
+
+  const [user, project] = await Promise.all([
+    loadAuthzUser(BigInt(session.user.dbId)),
+    loadProjectAuthzFacts(projectId),
+  ]);
+
+  if (!user) return { ok: false, error: "Unauthorised", status: 401 };
+  if (!project) return { ok: false, error: "Project not found", status: 404 };
+
+  if (!canViewProject(user, project)) {
+    return { ok: false, error: "Project not found", status: 404 };
+  }
+  if (!canManageProject(user, project)) {
+    return { ok: false, error: "Forbidden", status: 403 };
+  }
+
+  return { ok: true, projectId };
+}
diff --git a/src/app/api/projects/[projectId]/work-orders/filters.test.ts b/src/app/api/projects/[projectId]/work-orders/filters.test.ts
new file mode 100644
index 00000000..144a1741
--- /dev/null
+++ b/src/app/api/projects/[projectId]/work-orders/filters.test.ts
@@ -0,0 +1,150 @@
+/**
+ * The work-orders query string (issue #419).
+ *
+ * Pure module, pure test: no database, no network. The round trip matters most
+ * — the client builds the params and the server parses them, so anything that
+ * survives `workOrderSearchParams` must come back out of `parseWorkOrderQuery`
+ * unchanged, or the table and its filter bar silently disagree.
+ */
+import { describe, expect, it } from "vitest";
+import {
+  DEFAULT_PAGE_SIZE,
+  MAX_PAGE_SIZE,
+  NO_FILTERS,
+  hasActiveFilters,
+  parseWorkOrderQuery,
+  workOrderSearchParams,
+  type WorkOrderFilterSelection,
+} from "./filters";
+
+const CONTRACTOR = "22222222-2222-2222-2222-222222222222";
+
+const parse = (query: string) => parseWorkOrderQuery(new URLSearchParams(query));
+
+describe("parseWorkOrderQuery", () => {
+  it("treats an empty query string as no filters and the default page size", () => {
+    const result = parse("");
+    expect(result).toEqual({
+      ok: true,
+      query: {
+        workstreamId: null,
+        contractorOrganisationId: null,
+        stageId: null,
+        overdueOnly: false,
+        missingEvidence: false,
+        cursor: null,
+        limit: DEFAULT_PAGE_SIZE,
+      },
+    });
+  });
+
+  it("parses every filter at once — they compose rather than override", () => {
+    const result = parse(
+      `workstreamId=10&stageId=102&contractorOrganisationId=${CONTRACTOR}` +
+        "&overdue=true&missingEvidence=true&cursor=812&limit=25",
+    );
+    expect(result).toEqual({
+      ok: true,
+      query: {
+        workstreamId: 10n,
+        contractorOrganisationId: CONTRACTOR,
+        stageId: 102n,
+        overdueOnly: true,
+        missingEvidence: true,
+        cursor: 812n,
+        limit: 25,
+      },
+    });
+  });
+
+  it("rejects a non-numeric id rather than silently dropping the filter", () => {
+    // A dropped filter shows a table that does not match the controls above it.
+    expect(parse("workstreamId=windows")).toEqual({
+      ok: false,
+      error: "Invalid workstreamId",
+    });
+    expect(parse("stageId=-1")).toEqual({ ok: false, error: "Invalid stageId" });
+    expect(parse("cursor=0")).toEqual({ ok: false, error: "Invalid cursor" });
+  });
+
+  it("rejects a contractor id that is not a uuid", () => {
+    expect(parse("contractorOrganisationId=42")).toEqual({
+      ok: false,
+      error: "Invalid contractorOrganisationId",
+    });
+  });
+
+  it("rejects a boolean it does not recognise, to catch a typo'd flag", () => {
+    expect(parse("overdue=yes")).toEqual({ ok: false, error: "Invalid overdue" });
+    expect(parse("missingEvidence=on")).toEqual({
+      ok: false,
+      error: "Invalid missingEvidence",
+    });
+  });
+
+  it("accepts the falsey spellings of a flag", () => {
+    expect(parse("overdue=false")).toMatchObject({
+      ok: true,
+      query: { overdueOnly: false },
+    });
+    expect(parse("overdue=1")).toMatchObject({
+      ok: true,
+      query: { overdueOnly: true },
+    });
+  });
+
+  it("refuses to stream the whole programme in one response", () => {
+    expect(parse(`limit=${MAX_PAGE_SIZE}`)).toMatchObject({ ok: true });
+    expect(parse(`limit=${MAX_PAGE_SIZE + 1}`)).toEqual({
+      ok: false,
+      error: "Invalid limit",
+    });
+    expect(parse("limit=0")).toEqual({ ok: false, error: "Invalid limit" });
+  });
+
+  it("rejects a SQL fragment in an id parameter", () => {
+    expect(parse("workstreamId=1%3B+DROP+TABLE+work_order")).toEqual({
+      ok: false,
+      error: "Invalid workstreamId",
+    });
+  });
+});
+
+describe("workOrderSearchParams", () => {
+  const selection: WorkOrderFilterSelection = {
+    workstreamId: "10",
+    contractorOrganisationId: CONTRACTOR,
+    stageId: "102",
+    overdueOnly: true,
+    missingEvidence: true,
+  };
+
+  it("round-trips a full selection back through the parser", () => {
+    const params = workOrderSearchParams(selection, { cursor: "812", limit: 25 });
+    expect(parseWorkOrderQuery(params)).toEqual({
+      ok: true,
+      query: {
+        workstreamId: 10n,
+        contractorOrganisationId: CONTRACTOR,
+        stageId: 102n,
+        overdueOnly: true,
+        missingEvidence: true,
+        cursor: 812n,
+        limit: 25,
+      },
+    });
+  });
+
+  it("omits everything falsey, so the unfiltered page has a stable cache key", () => {
+    expect(workOrderSearchParams(NO_FILTERS).toString()).toBe("");
+    expect(workOrderSearchParams(NO_FILTERS, { cursor: null }).toString()).toBe("");
+  });
+});
+
+describe("hasActiveFilters", () => {
+  it("is false only when nothing at all is narrowed", () => {
+    expect(hasActiveFilters(NO_FILTERS)).toBe(false);
+    expect(hasActiveFilters({ ...NO_FILTERS, overdueOnly: true })).toBe(true);
+    expect(hasActiveFilters({ ...NO_FILTERS, stageId: "1" })).toBe(true);
+  });
+});
diff --git a/src/app/api/projects/[projectId]/work-orders/filters.ts b/src/app/api/projects/[projectId]/work-orders/filters.ts
new file mode 100644
index 00000000..a012c88a
--- /dev/null
+++ b/src/app/api/projects/[projectId]/work-orders/filters.ts
@@ -0,0 +1,204 @@
+/**
+ * The work-orders table's query string, in one place (issue #419).
+ *
+ * The filter bar, the `useQuery` key, the fetch URL and the route handler all
+ * have to agree on exactly what `?overdue=true&cursor=812` means. They agree
+ * because they all go through this module: the client *builds* the search
+ * params with `workOrderSearchParams`, the handler *parses* them back with
+ * `parseWorkOrderQuery`, and neither reads a raw parameter name of its own.
+ *
+ * Pure by construction — no database client, no React — so it is safe to import
+ * from a client component and it unit-tests without a connection.
+ *
+ * ## Two representations, deliberately
+ *
+ * - **Selection** (`WorkOrderFilterSelection`) is what the UI holds: ids as
+ *   strings, because bigint ids do not survive JSON and a `<select>` value is a
+ *   string anyway.
+ * - **Query** (`WorkOrderQuery`) is what the server acts on: ids parsed to
+ *   `bigint`, ready for Drizzle. Parsing is the boundary where a junk id
+ *   becomes a 400 rather than a database error.
+ */
+
+/** `project_workstream.id` / `project_workstream_stage.id` as a wire string. */
+const NUMERIC_ID = /^\d+$/;
+
+/** `organisation.id` is a uuid; anything else is not a contractor. */
+const UUID =
+  /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i;
+
+/** Rows per page when the caller does not ask for a size. */
+export const DEFAULT_PAGE_SIZE = 50;
+
+/**
+ * The most rows one request may ask for. A programme runs to thousands of work
+ * orders, so an unbounded `limit` is a way to ask the server to stream the
+ * whole table into one response.
+ */
+export const MAX_PAGE_SIZE = 200;
+
+/** The filter bar's state: what the user has narrowed the table to. */
+export interface WorkOrderFilterSelection {
+  /** `project_workstream.id` — the Project Workstream, not the catalogue row. */
+  workstreamId: string | null;
+  /** `organisation.id` of the contractor. */
+  contractorOrganisationId: string | null;
+  /** `project_workstream_stage.id`. */
+  stageId: string | null;
+  /** Only work orders that are overdue by the shared derivation rule. */
+  overdueOnly: boolean;
+  /** Only work orders with at least one applicable required document missing. */
+  missingEvidence: boolean;
+}
+
+/** No filters at all — the table's opening state. */
+export const NO_FILTERS: WorkOrderFilterSelection = {
+  workstreamId: null,
+  contractorOrganisationId: null,
+  stageId: null,
+  overdueOnly: false,
+  missingEvidence: false,
+};
+
+/** True when nothing is narrowed, so the UI can label the empty state honestly. */
+export function hasActiveFilters(selection: WorkOrderFilterSelection): boolean {
+  return (
+    selection.workstreamId !== null ||
+    selection.contractorOrganisationId !== null ||
+    selection.stageId !== null ||
+    selection.overdueOnly ||
+    selection.missingEvidence
+  );
+}
+
+/** The parsed, server-side form of one page request. */
+export interface WorkOrderQuery {
+  workstreamId: bigint | null;
+  contractorOrganisationId: string | null;
+  stageId: bigint | null;
+  overdueOnly: boolean;
+  missingEvidence: boolean;
+  /**
+   * Keyset cursor: the `work_order.id` of the last row of the previous page.
+   * Null asks for the first page. Rows are ordered by `work_order.id`, so a
+   * cursor stays meaningful under any combination of filters — the whole point
+   * of paginating by key rather than by offset.
+   */
+  cursor: bigint | null;
+  limit: number;
+}
+
+/** The query a request with no parameters at all asks for. */
+export const DEFAULT_QUERY: WorkOrderQuery = {
+  workstreamId: null,
+  contractorOrganisationId: null,
+  stageId: null,
+  overdueOnly: false,
+  missingEvidence: false,
+  cursor: null,
+  limit: DEFAULT_PAGE_SIZE,
+};
+
+export type ParsedQuery =
+  | { ok: true; query: WorkOrderQuery }
+  | { ok: false; error: string };
+
+/**
+ * Parse a request's search params into a `WorkOrderQuery`.
+ *
+ * Every failure is reported rather than silently defaulted: a filter the server
+ * quietly dropped shows the user a table that does not match the controls above
+ * it, which is worse than an error. An *absent* parameter is not a failure — it
+ * simply means "not filtered".
+ */
+export function parseWorkOrderQuery(params: URLSearchParams): ParsedQuery {
+  const workstreamId = parseId(params.get("workstreamId"));
+  if (workstreamId === INVALID) {
+    return { ok: false, error: "Invalid workstreamId" };
+  }
+
+  const stageId = parseId(params.get("stageId"));
+  if (stageId === INVALID) return { ok: false, error: "Invalid stageId" };
+
+  const cursor = parseId(params.get("cursor"));
+  if (cursor === INVALID) return { ok: false, error: "Invalid cursor" };
+
+  const contractor = params.get("contractorOrganisationId");
+  if (contractor !== null && !UUID.test(contractor)) {
+    return { ok: false, error: "Invalid contractorOrganisationId" };
+  }
+
+  const overdueOnly = parseBoolean(params.get("overdue"));
+  if (overdueOnly === INVALID) return { ok: false, error: "Invalid overdue" };
+
+  const missingEvidence = parseBoolean(params.get("missingEvidence"));
+  if (missingEvidence === INVALID) {
+    return { ok: false, error: "Invalid missingEvidence" };
+  }
+
+  const limit = parseLimit(params.get("limit"));
+  if (limit === INVALID) return { ok: false, error: "Invalid limit" };
+
+  return {
+    ok: true,
+    query: {
+      workstreamId,
+      contractorOrganisationId: contractor,
+      stageId,
+      overdueOnly,
+      missingEvidence,
+      cursor,
+      limit,
+    },
+  };
+}
+
+/**
+ * Build the search params for one page request — the exact inverse of
+ * `parseWorkOrderQuery`, and the only place the client names a parameter.
+ *
+ * Falsey filters are omitted rather than serialised as `false`/empty, so the
+ * unfiltered first page has a stable, empty query string and therefore a stable
+ * React Query cache key.
+ */
+export function workOrderSearchParams(
+  selection: WorkOrderFilterSelection,
+  page: { cursor?: string | null; limit?: number } = {},
+): URLSearchParams {
+  const params = new URLSearchParams();
+  if (selection.workstreamId) params.set("workstreamId", selection.workstreamId);
+  if (selection.contractorOrganisationId) {
+    params.set("contractorOrganisationId", selection.contractorOrganisationId);
+  }
+  if (selection.stageId) params.set("stageId", selection.stageId);
+  if (selection.overdueOnly) params.set("overdue", "true");
+  if (selection.missingEvidence) params.set("missingEvidence", "true");
+  if (page.cursor) params.set("cursor", page.cursor);
+  if (page.limit !== undefined) params.set("limit", String(page.limit));
+  return params;
+}
+
+/** Sentinel distinguishing "not supplied" (null) from "supplied but wrong". */
+const INVALID = Symbol("invalid");
+
+function parseId(raw: string | null): bigint | null | typeof INVALID {
+  if (raw === null) return null;
+  if (!NUMERIC_ID.test(raw)) return INVALID;
+  const parsed = BigInt(raw);
+  return parsed > 0n ? parsed : INVALID;
+}
+
+function parseBoolean(raw: string | null): boolean | typeof INVALID {
+  if (raw === null) return false;
+  if (raw === "true" || raw === "1") return true;
+  if (raw === "false" || raw === "0") return false;
+  return INVALID;
+}
+
+function parseLimit(raw: string | null): number | typeof INVALID {
+  if (raw === null) return DEFAULT_PAGE_SIZE;
+  if (!NUMERIC_ID.test(raw)) return INVALID;
+  const parsed = Number(raw);
+  if (parsed < 1 || parsed > MAX_PAGE_SIZE) return INVALID;
+  return parsed;
+}
diff --git a/src/app/api/projects/[projectId]/work-orders/queries.test.ts b/src/app/api/projects/[projectId]/work-orders/queries.test.ts
new file mode 100644
index 00000000..1f484f87
--- /dev/null
+++ b/src/app/api/projects/[projectId]/work-orders/queries.test.ts
@@ -0,0 +1,209 @@
+/**
+ * Query construction for the work-orders table (issue #419).
+ *
+ * The db module is stubbed *before* it is imported, so no `pg.Pool` is ever
+ * constructed and this suite cannot open a connection. What is under test is
+ * the SQL these builders emit, not its execution — in particular that the
+ * derived filters cross into SQL as *data* (terminal stage ids, applicable
+ * requirement pairs) rather than as re-implemented rules.
+ */
+import { describe, expect, it, vi } from "vitest";
+import { PgDialect } from "drizzle-orm/pg-core";
+
+vi.mock("@/app/db/db", () => ({
+  db: {
+    execute: () => {
+      throw new Error("queries.test must not execute queries");
+    },
+  },
+  pool: {},
+}));
+
+import { buildWorkOrderCountQuery, buildWorkOrderPageQuery } from "./queries";
+import { DEFAULT_QUERY, type WorkOrderQuery } from "./filters";
+
+const dialect = new PgDialect();
+const render = (query: ReturnType<typeof buildWorkOrderPageQuery>) =>
+  dialect.sqlToQuery(query);
+
+const ASOF = new Date("2026-07-23T09:30:00Z");
+const CONTRACTOR = "22222222-2222-2222-2222-222222222222";
+const TERMINAL = [103n, 203n];
+
+const query = (overrides: Partial<WorkOrderQuery> = {}): WorkOrderQuery => ({
+  ...DEFAULT_QUERY,
+  ...overrides,
+});
+
+const page = (q: Partial<WorkOrderQuery> = {}, terminal = TERMINAL) =>
+  render(buildWorkOrderPageQuery(7n, query(q), ASOF, [], terminal));
+
+describe("buildWorkOrderPageQuery", () => {
+  it("scopes to the project and binds the id as a parameter", () => {
+    const { sql, params } = page();
+    expect(sql).toContain("pw.project_id =");
+    expect(params).toContain(7n);
+  });
+
+  it("asks for one row more than the page size, to detect a next page", () => {
+    const { params } = page({ limit: 50 });
+    expect(params).toContain(51);
+  });
+
+  it("orders by work_order id so a cursor survives any filter combination", () => {
+    expect(page().sql).toContain("ORDER BY id ASC");
+  });
+
+  it("applies the cursor as a keyset comparison, not an offset", () => {
+    const { sql, params } = page({ cursor: 812n });
+    expect(sql).toContain("id >");
+    expect(sql).not.toContain("OFFSET");
+    expect(params).toContain(812n);
+  });
+
+  it("emits no WHERE over the aggregate when nothing needs one", () => {
+    expect(page().sql).not.toContain("satisfied_count <");
+  });
+
+  describe("filters", () => {
+    it("narrows to a Project Workstream", () => {
+      const { sql, params } = page({ workstreamId: 10n });
+      expect(sql).toContain("pw.id =");
+      expect(params).toContain(10n);
+    });
+
+    it("narrows to a stage", () => {
+      const { sql, params } = page({ stageId: 102n });
+      expect(sql).toContain("wo.project_workstream_stage_id =");
+      expect(params).toContain(102n);
+    });
+
+    it("narrows to a contractor organisation, cast to uuid", () => {
+      const { sql, params } = page({ contractorOrganisationId: CONTRACTOR });
+      expect(sql).toContain("pwc.organisation_id =");
+      expect(sql).toContain("::uuid");
+      expect(params).toContain(CONTRACTOR);
+    });
+
+    it("composes several filters rather than replacing one with another", () => {
+      const { sql, params } = page({
+        workstreamId: 10n,
+        stageId: 102n,
+        contractorOrganisationId: CONTRACTOR,
+        overdueOnly: true,
+        missingEvidence: true,
+      });
+      expect(sql).toContain("pw.id =");
+      expect(sql).toContain("wo.project_workstream_stage_id =");
+      expect(sql).toContain("pwc.organisation_id =");
+      expect(sql).toContain("wo.forecast_end <");
+      expect(sql).toContain("satisfied_count < required_count");
+      expect(params).toEqual(
+        expect.arrayContaining([7n, 10n, 102n, CONTRACTOR, "2026-07-23"]),
+      );
+    });
+  });
+
+  describe("overdue", () => {
+    it("binds the caller's day rather than trusting the database clock", () => {
+      const { sql, params } = page({ overdueOnly: true });
+      expect(params).toContain("2026-07-23");
+      expect(sql).not.toContain("CURRENT_DATE");
+    });
+
+    it("excludes terminal stages using ids the ladders classified in JS", () => {
+      const { sql } = page({ overdueOnly: true });
+      expect(sql).toContain(
+        "wo.project_workstream_stage_id NOT IN (103, 203)",
+      );
+      // Terminal-ness is a ladder question; the query must not attempt it.
+      expect(sql).not.toMatch(/max\s*\(\s*"?order"?\s*\)/i);
+    });
+
+    it("omits the exclusion when no stage is terminal, rather than emitting NOT IN ()", () => {
+      const { sql } = page({ overdueOnly: true }, []);
+      expect(sql).toContain("wo.forecast_end <");
+      expect(sql).not.toContain("NOT IN ()");
+    });
+
+    it("does not touch forecast_end at all when the filter is off", () => {
+      expect(page().sql).not.toContain("wo.forecast_end <");
+    });
+  });
+
+  describe("evidence", () => {
+    it("filters missing evidence before LIMIT, so pagination stays stable", () => {
+      const { sql } = page({ missingEvidence: true });
+      const whereAt = sql.indexOf("satisfied_count < required_count");
+      const limitAt = sql.lastIndexOf("LIMIT");
+      expect(whereAt).toBeGreaterThan(-1);
+      expect(whereAt).toBeLessThan(limitAt);
+    });
+
+    it("counts against the applicable pairs the derivations module supplied", () => {
+      const { sql } = render(
+        buildWorkOrderPageQuery(
+          7n,
+          query(),
+          ASOF,
+          [
+            { stageId: 102n, requirementId: 7n },
+            { stageId: 103n, requirementId: 8n },
+          ],
+          TERMINAL,
+        ),
+      );
+      expect(sql).toContain("(102::bigint, 7::bigint)");
+      expect(sql).toContain("(103::bigint, 8::bigint)");
+      expect(sql).toContain("AS v(stage_id, requirement_id)");
+    });
+
+    it("emits a well-typed empty CTE when nothing is required, not empty VALUES", () => {
+      const { sql } = page();
+      expect(sql).toContain("WHERE false");
+      expect(sql).not.toMatch(/VALUES\s*\)/);
+    });
+
+    it("only counts Projects-sourced files as Evidence", () => {
+      expect(page().sql).toContain("uf.file_source = 'projects'");
+    });
+  });
+
+  it("left-joins the contractor assignment so an unassigned order still appears", () => {
+    expect(page().sql).toContain("LEFT JOIN project_workstream_contractor");
+  });
+
+  it("reads the stage and workstream names live, never from the work order", () => {
+    const { sql } = page();
+    expect(sql).toContain("pws.name");
+    expect(sql).toContain("w.name");
+  });
+
+  it("rejects an invalid asOf rather than issuing a query with a null date", () => {
+    expect(() =>
+      buildWorkOrderPageQuery(7n, query(), new Date("nope"), [], TERMINAL),
+    ).toThrow();
+  });
+});
+
+describe("buildWorkOrderCountQuery", () => {
+  const count = (q: Partial<WorkOrderQuery> = {}) =>
+    render(buildWorkOrderCountQuery(7n, query(q), ASOF, [], TERMINAL));
+
+  it("counts the filtered set", () => {
+    const { sql } = count({ overdueOnly: true });
+    expect(sql).toContain("count(*)::int");
+    expect(sql).toContain("wo.forecast_end <");
+  });
+
+  it("ignores the cursor — the footer counts matches, not what is left", () => {
+    const { sql } = count({ cursor: 812n });
+    expect(sql).not.toContain("id >");
+  });
+
+  it("still applies the evidence filter", () => {
+    expect(count({ missingEvidence: true }).sql).toContain(
+      "satisfied_count < required_count",
+    );
+  });
+});
diff --git a/src/app/api/projects/[projectId]/work-orders/queries.ts b/src/app/api/projects/[projectId]/work-orders/queries.ts
new file mode 100644
index 00000000..826ec121
--- /dev/null
+++ b/src/app/api/projects/[projectId]/work-orders/queries.ts
@@ -0,0 +1,421 @@
+/**
+ * Persistence for the admin work-orders table (issue #419).
+ *
+ * The rule for this file is the one `@/app/repositories/projects/dashboardRepository`
+ * set for the dashboard: **SQL counts facts, TypeScript makes judgements.**
+ * A programme runs to thousands of work orders, so filtering and pagination
+ * must happen in the database — but no rule may be restated here in SQL, or the
+ * table's badges and the dashboard's KPIs will eventually disagree.
+ *
+ * So each derived filter is split at its `AND`, exactly as the dashboard splits
+ * it, and the TypeScript half crosses into SQL **as data**:
+ *
+ *   - **overdue** — `buildStageLadders` classifies the project's few dozen
+ *     stages in JS; `stageIdsByProgress("complete")` hands the terminal ids to
+ *     the query, which then counts `forecast_end < asOf AND stage NOT IN
+ *     (terminal)`. SQL is never asked what "terminal" means.
+ *   - **missing required evidence** — `requiredEvidenceRequirementIds` decides
+ *     which requirement applies at which stage and hands over an explicit
+ *     `(stage_id, requirement_id)` list. The query counts against that list.
+ *     `evidenceCompleteness` clamps `satisfied` into `[0, required]`, so
+ *     `isMissingRequiredEvidence` is exactly `satisfied_count < required_count`
+ *     — the predicate the outer `WHERE` uses to filter *before* `LIMIT`, which
+ *     is the one thing a JS-side filter could not do correctly.
+ *
+ * Every row the query returns still gets its badges from `toWorkOrderRow`, so
+ * what the user sees is always the pure module's answer.
+ *
+ * Read-only: this module issues `SELECT`s and nothing else.
+ */
+import { db } from "@/app/db/db";
+import { and, asc, eq, sql, type SQL } from "drizzle-orm";
+import {
+  projectWorkstream,
+  projectWorkstreamContractor,
+  projectWorkstreamStage,
+  workstream,
+} from "@/app/db/schema/projects/projects";
+import { organisation } from "@/app/db/schema/organisation";
+import { buildStageLadders, toCalendarDay } from "@/lib/projects/derivations";
+import {
+  buildApplicableEvidencePairs,
+  loadEvidenceRequirements,
+  loadStageLadderEntries,
+  type ApplicableEvidencePair,
+} from "@/app/repositories/projects/dashboardRepository";
+import type { WorkOrderQuery } from "./filters";
+import { toWorkOrderRow, type RawWorkOrderRow, type WorkOrderPage } from "./rows";
+
+/** The choices the filter bar offers, all read live from the project's setup. */
+export interface WorkOrderFilterOptions {
+  /** Project Workstreams, named from the `workstream` reference data. */
+  workstreams: { id: string; name: string }[];
+  /** Every organisation assigned as contractor to any of the project's workstreams. */
+  contractors: { organisationId: string; name: string }[];
+  /** Every stage of every workstream, so the stage filter can narrow to one workstream. */
+  stages: { id: string; name: string; workstreamId: string; order: number }[];
+}
+
+/**
+ * Load one page of the table.
+ *
+ * The stage ladders and evidence requirements are read first because the
+ * filters that depend on them (`overdue`, `missingEvidence`) can only be pushed
+ * into SQL once the pure module has been asked its questions. `asOf` is bound
+ * as a date parameter and reused for the row badges, never `CURRENT_DATE`.
+ */
+export async function loadWorkOrderPage(
+  projectId: bigint,
+  query: WorkOrderQuery,
+  asOf: Date,
+): Promise<WorkOrderPage> {
+  const [stages, requirements] = await Promise.all([
+    loadStageLadderEntries(projectId),
+    loadEvidenceRequirements(projectId),
+  ]);
+
+  const ladders = buildStageLadders(stages);
+  const applicableEvidence = buildApplicableEvidencePairs(
+    ladders,
+    stages,
+    requirements,
+  );
+  const terminalStageIds = ladders.stageIdsByProgress("complete");
+
+  const [pageRows, totalRows] = await Promise.all([
+    db.execute<WorkOrderQueryRow>(
+      buildWorkOrderPageQuery(
+        projectId,
+        query,
+        asOf,
+        applicableEvidence,
+        terminalStageIds,
+      ),
+    ),
+    db.execute<{ total: number }>(
+      buildWorkOrderCountQuery(
+        projectId,
+        query,
+        asOf,
+        applicableEvidence,
+        terminalStageIds,
+      ),
+    ),
+  ]);
+
+  // One row over the page size was requested: its presence — not a count
+  // comparison — is what proves another page exists.
+  const rows = pageRows.rows.map(toRawWorkOrderRow);
+  const hasMore = rows.length > query.limit;
+  const page = hasMore ? rows.slice(0, query.limit) : rows;
+
+  return {
+    workOrders: page.map((raw) => toWorkOrderRow(ladders, raw, asOf)),
+    nextCursor: hasMore ? page[page.length - 1].id.toString() : null,
+    total: Number(totalRows.rows[0]?.total ?? 0),
+  };
+}
+
+/** The choices for the three dropdowns, in one round trip each. */
+export async function loadFilterOptions(
+  projectId: bigint,
+): Promise<WorkOrderFilterOptions> {
+  const [workstreams, contractors, stages] = await Promise.all([
+    db
+      .select({ id: projectWorkstream.id, name: workstream.name })
+      .from(projectWorkstream)
+      .innerJoin(workstream, eq(projectWorkstream.workstreamId, workstream.id))
+      .where(eq(projectWorkstream.projectId, projectId))
+      .orderBy(workstream.name),
+
+    db
+      .selectDistinct({
+        organisationId: projectWorkstreamContractor.organisationId,
+        name: organisation.name,
+      })
+      .from(projectWorkstreamContractor)
+      .innerJoin(
+        projectWorkstream,
+        eq(projectWorkstreamContractor.projectWorkstreamId, projectWorkstream.id),
+      )
+      .innerJoin(
+        organisation,
+        eq(organisation.id, projectWorkstreamContractor.organisationId),
+      )
+      .where(eq(projectWorkstream.projectId, projectId))
+      .orderBy(organisation.name),
+
+    db
+      .select({
+        id: projectWorkstreamStage.id,
+        name: projectWorkstreamStage.name,
+        workstreamId: projectWorkstreamStage.projectWorkstreamId,
+        order: projectWorkstreamStage.order,
+      })
+      .from(projectWorkstreamStage)
+      .innerJoin(
+        projectWorkstream,
+        eq(projectWorkstreamStage.projectWorkstreamId, projectWorkstream.id),
+      )
+      .where(eq(projectWorkstream.projectId, projectId))
+      .orderBy(
+        asc(projectWorkstreamStage.projectWorkstreamId),
+        asc(projectWorkstreamStage.order),
+      ),
+  ]);
+
+  return {
+    workstreams: workstreams.map((row) => ({
+      id: row.id.toString(),
+      name: row.name,
+    })),
+    // `organisation.name` is nullable; a contractor with no name still has to
+    // be selectable, so it is labelled by its id rather than dropped.
+    contractors: contractors.map((row) => ({
+      organisationId: row.organisationId,
+      name: row.name ?? `Organisation ${row.organisationId}`,
+    })),
+    stages: stages.map((row) => ({
+      id: row.id.toString(),
+      name: row.name,
+      workstreamId: row.workstreamId.toString(),
+      order: row.order,
+    })),
+  };
+}
+
+/** The raw column shape the page query returns. Postgres counts arrive as strings. */
+interface WorkOrderQueryRow extends Record<string, unknown> {
+  id: string;
+  reference: string;
+  landlord_property_id: string | null;
+  address: string | null;
+  postcode: string | null;
+  workstream_id: string;
+  workstream_name: string;
+  contractor_organisation_id: string | null;
+  contractor_name: string | null;
+  stage_id: string;
+  stage_name: string;
+  forecast_end: string | null;
+  required_count: string | number;
+  satisfied_count: string | number;
+}
+
+function toRawWorkOrderRow(row: WorkOrderQueryRow): RawWorkOrderRow {
+  return {
+    id: BigInt(row.id),
+    reference: row.reference,
+    landlordPropertyId: row.landlord_property_id,
+    address: row.address,
+    postcode: row.postcode,
+    workstreamId: BigInt(row.workstream_id),
+    workstreamName: row.workstream_name,
+    contractorOrganisationId: row.contractor_organisation_id,
+    contractorName: row.contractor_name,
+    stageId: BigInt(row.stage_id),
+    stageName: row.stage_name,
+    // A `date` column arrives as `YYYY-MM-DD`; take the day part defensively so
+    // a driver that ever hands back a timestamp cannot leak a time into the UI.
+    forecastEnd: toCalendarDay(row.forecast_end),
+    requiredEvidence: Number(row.required_count),
+    satisfiedEvidence: Number(row.satisfied_count),
+  };
+}
+
+/**
+ * Build the page query, separately from running it, so a unit test can render
+ * and assert on the SQL without opening a connection.
+ *
+ * `limit + 1` rows are requested: see `loadWorkOrderPage`.
+ */
+export function buildWorkOrderPageQuery(
+  projectId: bigint,
+  query: WorkOrderQuery,
+  asOf: Date,
+  applicableEvidence: readonly ApplicableEvidencePair[],
+  terminalStageIds: readonly bigint[],
+) {
+  const scope = workOrderScope(
+    projectId,
+    query,
+    asOf,
+    applicableEvidence,
+    terminalStageIds,
+  );
+  return sql`${scope} SELECT * FROM per_order ${outerWhere(
+    query,
+    true,
+  )} ORDER BY id ASC LIMIT ${query.limit + 1}`;
+}
+
+/**
+ * The same filtered set, counted. The cursor is deliberately *not* applied —
+ * the footer says how many work orders match the filters, not how many are left
+ * after the page the user is on.
+ */
+export function buildWorkOrderCountQuery(
+  projectId: bigint,
+  query: WorkOrderQuery,
+  asOf: Date,
+  applicableEvidence: readonly ApplicableEvidencePair[],
+  terminalStageIds: readonly bigint[],
+) {
+  const scope = workOrderScope(
+    projectId,
+    query,
+    asOf,
+    applicableEvidence,
+    terminalStageIds,
+  );
+  return sql`${scope} SELECT count(*)::int AS total FROM per_order ${outerWhere(
+    query,
+    false,
+  )}`;
+}
+
+/**
+ * The `WITH applicable … per_order` prelude both queries share: the joins, the
+ * filters that can be pushed down, and the per-work-order evidence counts.
+ *
+ * The evidence counts are aggregated per work order here rather than in the
+ * outer query so the `missingEvidence` filter can be a plain `WHERE` over
+ * `per_order` — and therefore run *before* `LIMIT`, which is what makes
+ * pagination stable under that filter.
+ */
+function workOrderScope(
+  projectId: bigint,
+  query: WorkOrderQuery,
+  asOf: Date,
+  applicableEvidence: readonly ApplicableEvidencePair[],
+  terminalStageIds: readonly bigint[],
+) {
+  const asOfDay = toCalendarDay(asOf);
+  if (asOfDay === null) throw new Error("loadWorkOrderPage: invalid asOf date");
+
+  // Ids are interpolated as bigint literals, never as user text: they come from
+  // rows this process just read, and `asBigIntLiteral` re-checks each one.
+  const pairsSql = applicableEvidence.length
+    ? sql.raw(
+        applicableEvidence
+          .map(
+            (pair) =>
+              `(${asBigIntLiteral(pair.stageId)}::bigint, ${asBigIntLiteral(
+                pair.requirementId,
+              )}::bigint)`,
+          )
+          .join(", "),
+      )
+    : null;
+
+  // `VALUES` with no rows is not legal SQL, so an empty applicable set still
+  // needs a well-typed, empty CTE.
+  const applicableCte = pairsSql
+    ? sql`SELECT * FROM (VALUES ${pairsSql}) AS v(stage_id, requirement_id)`
+    : sql`SELECT NULL::bigint AS stage_id, NULL::bigint AS requirement_id WHERE false`;
+
+  const conditions = [sql`pw.project_id = ${projectId}`];
+
+  if (query.workstreamId !== null) {
+    conditions.push(sql`pw.id = ${query.workstreamId}`);
+  }
+  if (query.stageId !== null) {
+    conditions.push(sql`wo.project_workstream_stage_id = ${query.stageId}`);
+  }
+  if (query.contractorOrganisationId !== null) {
+    conditions.push(
+      sql`pwc.organisation_id = ${query.contractorOrganisationId}::uuid`,
+    );
+  }
+  if (query.overdueOnly) {
+    // The SQL half of `isOverdue`. A work order with no forecast end is never
+    // overdue, and `NULL < date` is NULL, so it drops out without a special case.
+    conditions.push(sql`wo.forecast_end < ${asOfDay}::date`);
+    // The TypeScript half, pushed down as data: complete work orders are never
+    // overdue however late they finished. An empty ladder set means no stage is
+    // terminal, so there is nothing to exclude.
+    if (terminalStageIds.length > 0) {
+      conditions.push(
+        sql`wo.project_workstream_stage_id NOT IN (${sql.raw(
+          terminalStageIds.map(asBigIntLiteral).join(", "),
+        )})`,
+      );
+    }
+  }
+
+  return sql`
+    WITH applicable AS (${applicableCte}),
+    per_order AS (
+      SELECT
+        wo.id,
+        wo.reference,
+        wo.forecast_end,
+        wo.project_workstream_stage_id AS stage_id,
+        pws.name                       AS stage_name,
+        pw.id                          AS workstream_id,
+        w.name                         AS workstream_name,
+        p.landlord_property_id,
+        p.address,
+        p.postcode,
+        pwc.organisation_id            AS contractor_organisation_id,
+        org.name                       AS contractor_name,
+        (
+          SELECT count(*) FROM applicable a
+          WHERE a.stage_id = wo.project_workstream_stage_id
+        ) AS required_count,
+        count(DISTINCT uf.project_workstream_evidence_requirement_id)
+          AS satisfied_count
+      FROM work_order wo
+      JOIN project_workstream_stage pws
+        ON pws.id = wo.project_workstream_stage_id
+      JOIN project_workstream pw
+        ON pw.id = pws.project_workstream_id
+      JOIN workstream w
+        ON w.id = pw.workstream_id
+      JOIN property p
+        ON p.id = wo.property_id
+      LEFT JOIN project_workstream_contractor pwc
+        ON pwc.id = wo.project_workstream_contractor_id
+      LEFT JOIN organisation org
+        ON org.id = pwc.organisation_id
+      LEFT JOIN uploaded_files uf
+        ON uf.work_order_id = wo.id
+       AND uf.file_source = 'projects'
+       AND EXISTS (
+             SELECT 1 FROM applicable a
+             WHERE a.stage_id = wo.project_workstream_stage_id
+               AND a.requirement_id = uf.project_workstream_evidence_requirement_id
+           )
+      WHERE ${and(...conditions)}
+      GROUP BY wo.id, wo.reference, wo.forecast_end,
+               wo.project_workstream_stage_id, pws.name, pw.id, w.name,
+               p.landlord_property_id, p.address, p.postcode,
+               pwc.organisation_id, org.name
+    )
+  `;
+}
+
+/**
+ * The conditions that can only be applied once the per-work-order evidence
+ * counts exist, plus the keyset cursor.
+ */
+function outerWhere(query: WorkOrderQuery, withCursor: boolean) {
+  const conditions: SQL[] = [];
+  if (query.missingEvidence) {
+    // `isMissingRequiredEvidence(evidenceCompleteness(required, satisfied))`,
+    // expressed over the counted columns — see the module header.
+    conditions.push(sql`satisfied_count < required_count`);
+  }
+  if (withCursor && query.cursor !== null) {
+    conditions.push(sql`id > ${query.cursor}`);
+  }
+  return conditions.length ? sql` WHERE ${and(...conditions)}` : sql``;
+}
+
+/** Render a bigint as a SQL literal, rejecting anything that is not one. */
+function asBigIntLiteral(value: bigint): string {
+  if (typeof value !== "bigint") {
+    throw new Error("asBigIntLiteral: expected a bigint id");
+  }
+  return value.toString();
+}
diff --git a/src/app/api/projects/[projectId]/work-orders/route.test.ts b/src/app/api/projects/[projectId]/work-orders/route.test.ts
new file mode 100644
index 00000000..ebb7f19c
--- /dev/null
+++ b/src/app/api/projects/[projectId]/work-orders/route.test.ts
@@ -0,0 +1,194 @@
+/**
+ * GET `/api/projects/[projectId]/work-orders` (issue #419).
+ *
+ * The database is mocked at the module boundary (`./queries` and the authz
+ * repository); no connection is opened. The authorization *decisions* are the
+ * real ones from `@/lib/projects/authz` — only the facts they read are faked.
+ */
+import { describe, expect, it, beforeEach, vi } from "vitest";
+import { NextRequest } from "next/server";
+
+const {
+  mockGetServerSession,
+  mockLoadAuthzUser,
+  mockLoadProjectAuthzFacts,
+  mockLoadWorkOrderPage,
+} = vi.hoisted(() => ({
+  mockGetServerSession: vi.fn(),
+  mockLoadAuthzUser: vi.fn(),
+  mockLoadProjectAuthzFacts: vi.fn(),
+  mockLoadWorkOrderPage: vi.fn(),
+}));
+
+vi.mock("next-auth", () => ({ getServerSession: mockGetServerSession }));
+vi.mock("@/app/api/auth/[...nextauth]/authOptions", () => ({ AuthOptions: {} }));
+vi.mock("@/app/repositories/projects/authzRepository", () => ({
+  loadAuthzUser: mockLoadAuthzUser,
+  loadProjectAuthzFacts: mockLoadProjectAuthzFacts,
+}));
+vi.mock("./queries", () => ({ loadWorkOrderPage: mockLoadWorkOrderPage }));
+
+import { GET } from "./route";
+import { DEFAULT_PAGE_SIZE } from "./filters";
+
+const CLIENT_ORG = "11111111-1111-1111-1111-111111111111";
+const CONTRACTOR_ORG = "22222222-2222-2222-2222-222222222222";
+const OTHER_ORG = "33333333-3333-3333-3333-333333333333";
+
+const EMPTY_PAGE = { workOrders: [], nextCursor: null, total: 0 };
+
+function signedInAs(organisationIds: string[], email = "someone@landlord.example") {
+  mockGetServerSession.mockResolvedValue({ user: { dbId: "7" } });
+  mockLoadAuthzUser.mockResolvedValue({ id: 7n, email, organisationIds });
+}
+
+function projectExists() {
+  mockLoadProjectAuthzFacts.mockResolvedValue({
+    id: 5n,
+    organisationId: CLIENT_ORG,
+    domnaAdminAccess: false,
+    contractorOrganisationIds: [CONTRACTOR_ORG],
+  });
+}
+
+const params = (projectId = "5") => ({ params: Promise.resolve({ projectId }) });
+
+const request = (search = "", projectId = "5") =>
+  new NextRequest(
+    `http://localhost/api/projects/${projectId}/work-orders${search}`,
+  );
+
+beforeEach(() => {
+  vi.clearAllMocks();
+  mockLoadWorkOrderPage.mockResolvedValue(EMPTY_PAGE);
+});
+
+describe("GET", () => {
+  it("401s without a session", async () => {
+    mockGetServerSession.mockResolvedValue(null);
+    const res = await GET(request(), params());
+    expect(res.status).toBe(401);
+    expect(await res.json()).toEqual({ error: "Unauthorised" });
+  });
+
+  it("400s on a non-numeric project id", async () => {
+    signedInAs([CLIENT_ORG]);
+    const res = await GET(request("", "abc"), params("abc"));
+    expect(res.status).toBe(400);
+    expect(await res.json()).toEqual({ error: "Invalid project" });
+  });
+
+  it("404s when the project does not exist", async () => {
+    signedInAs([CLIENT_ORG]);
+    mockLoadProjectAuthzFacts.mockResolvedValue(null);
+    const res = await GET(request(), params());
+    expect(res.status).toBe(404);
+  });
+
+  it("404s rather than 403s for a user outside the project", async () => {
+    signedInAs([OTHER_ORG]);
+    projectExists();
+    const res = await GET(request(), params());
+    expect(res.status).toBe(404);
+    expect(mockLoadWorkOrderPage).not.toHaveBeenCalled();
+  });
+
+  it("403s a contractor: this is the admin table, and row scoping is a later issue", async () => {
+    signedInAs([CONTRACTOR_ORG]);
+    projectExists();
+    const res = await GET(request(), params());
+    expect(res.status).toBe(403);
+    expect(await res.json()).toEqual({ error: "Forbidden" });
+    expect(mockLoadWorkOrderPage).not.toHaveBeenCalled();
+  });
+
+  it("serves a client-org member the unfiltered first page", async () => {
+    signedInAs([CLIENT_ORG]);
+    projectExists();
+    const res = await GET(request(), params());
+    expect(res.status).toBe(200);
+    expect(await res.json()).toEqual(EMPTY_PAGE);
+    expect(mockLoadWorkOrderPage).toHaveBeenCalledWith(
+      5n,
+      expect.objectContaining({
+        workstreamId: null,
+        overdueOnly: false,
+        cursor: null,
+        limit: DEFAULT_PAGE_SIZE,
+      }),
+      expect.any(Date),
+    );
+  });
+
+  it("serves an internal user on an admin-access project", async () => {
+    signedInAs([], "someone@domna.homes");
+    mockLoadProjectAuthzFacts.mockResolvedValue({
+      id: 5n,
+      organisationId: CLIENT_ORG,
+      domnaAdminAccess: true,
+      contractorOrganisationIds: [],
+    });
+    const res = await GET(request(), params());
+    expect(res.status).toBe(200);
+  });
+
+  it("passes the parsed filters and cursor through to the query", async () => {
+    signedInAs([CLIENT_ORG]);
+    projectExists();
+    const res = await GET(
+      request(
+        `?workstreamId=10&stageId=102&contractorOrganisationId=${CONTRACTOR_ORG}` +
+          "&overdue=true&missingEvidence=true&cursor=812&limit=25",
+      ),
+      params(),
+    );
+    expect(res.status).toBe(200);
+    expect(mockLoadWorkOrderPage).toHaveBeenCalledWith(
+      5n,
+      {
+        workstreamId: 10n,
+        contractorOrganisationId: CONTRACTOR_ORG,
+        stageId: 102n,
+        overdueOnly: true,
+        missingEvidence: true,
+        cursor: 812n,
+        limit: 25,
+      },
+      expect.any(Date),
+    );
+  });
+
+  it("400s a malformed filter instead of quietly ignoring it", async () => {
+    signedInAs([CLIENT_ORG]);
+    projectExists();
+    const res = await GET(request("?overdue=yes"), params());
+    expect(res.status).toBe(400);
+    expect(await res.json()).toEqual({ error: "Invalid overdue" });
+    expect(mockLoadWorkOrderPage).not.toHaveBeenCalled();
+  });
+
+  it("returns the page's cursor and total untouched", async () => {
+    signedInAs([CLIENT_ORG]);
+    projectExists();
+    mockLoadWorkOrderPage.mockResolvedValue({
+      workOrders: [{ id: "812", reference: "WO-23881" }],
+      nextCursor: "812",
+      total: 1231,
+    });
+    const res = await GET(request(), params());
+    expect(await res.json()).toMatchObject({ nextCursor: "812", total: 1231 });
+  });
+
+  it("500s without leaking the driver error", async () => {
+    signedInAs([CLIENT_ORG]);
+    projectExists();
+    const consoleError = vi.spyOn(console, "error").mockImplementation(() => {});
+    mockLoadWorkOrderPage.mockRejectedValue(new Error("connection reset"));
+    const res = await GET(request(), params());
+    expect(res.status).toBe(500);
+    expect(await res.json()).toEqual({
+      error: "Couldn't load the work orders",
+    });
+    consoleError.mockRestore();
+  });
+});
diff --git a/src/app/api/projects/[projectId]/work-orders/route.ts b/src/app/api/projects/[projectId]/work-orders/route.ts
new file mode 100644
index 00000000..b4cdec61
--- /dev/null
+++ b/src/app/api/projects/[projectId]/work-orders/route.ts
@@ -0,0 +1,44 @@
+/**
+ * `GET /api/projects/[projectId]/work-orders` (issue #419).
+ *
+ * One page of the admin work-orders table, filtered and keyset-paginated in the
+ * database. The client calls this on every filter change and page step through
+ * TanStack Query; the page itself server-renders the first page from the same
+ * `loadWorkOrderPage`, so the first paint and every refetch afterwards are
+ * produced by identical code.
+ *
+ * Read-only — this route issues `SELECT`s and nothing else.
+ */
+import { NextRequest, NextResponse } from "next/server";
+import { authorizeWorkOrdersRequest } from "./authorize";
+import { parseWorkOrderQuery } from "./filters";
+import { loadWorkOrderPage } from "./queries";
+
+type Params = { params: Promise<{ projectId: string }> };
+
+export async function GET(req: NextRequest, props: Params) {
+  const { projectId } = await props.params;
+  const auth = await authorizeWorkOrdersRequest(projectId);
+  if (!auth.ok) {
+    return NextResponse.json({ error: auth.error }, { status: auth.status });
+  }
+
+  const parsed = parseWorkOrderQuery(req.nextUrl.searchParams);
+  if (!parsed.ok) {
+    return NextResponse.json({ error: parsed.error }, { status: 400 });
+  }
+
+  try {
+    // One `asOf` per request, passed to both the SQL filter and the row badges,
+    // so a request that straddles midnight cannot classify a work order as
+    // overdue in the WHERE clause and not-overdue in its badge.
+    const page = await loadWorkOrderPage(auth.projectId, parsed.query, new Date());
+    return NextResponse.json(page);
+  } catch (err) {
+    console.error("GET /api/projects/[projectId]/work-orders failed:", err);
+    return NextResponse.json(
+      { error: "Couldn't load the work orders" },
+      { status: 500 },
+    );
+  }
+}
diff --git a/src/app/api/projects/[projectId]/work-orders/rows.test.ts b/src/app/api/projects/[projectId]/work-orders/rows.test.ts
new file mode 100644
index 00000000..a7507b42
--- /dev/null
+++ b/src/app/api/projects/[projectId]/work-orders/rows.test.ts
@@ -0,0 +1,150 @@
+/**
+ * Row derivation for the work-orders table (issue #419).
+ *
+ * The point of these tests is not to re-test `@/lib/projects/derivations` —
+ * #418 owns that — but to prove this table *asks* it rather than deciding for
+ * itself: a complete work order past its forecast day is not overdue, the
+ * evidence counts are clamped, and an unknown stage degrades honestly.
+ *
+ * In-memory fixtures throughout; no database is imported.
+ */
+import { describe, expect, it } from "vitest";
+import { buildStageLadders, type StageLadderEntry } from "@/lib/projects/derivations";
+import { toWorkOrderRow, type RawWorkOrderRow } from "./rows";
+
+const WINDOWS = 10n;
+const STAGES: StageLadderEntry[] = [
+  { id: 101n, projectWorkstreamId: WINDOWS, order: 1 }, // not started
+  { id: 102n, projectWorkstreamId: WINDOWS, order: 2 }, // in progress
+  { id: 103n, projectWorkstreamId: WINDOWS, order: 3 }, // terminal
+];
+const LADDERS = buildStageLadders(STAGES);
+const ASOF = new Date("2026-07-23T09:30:00Z");
+
+function raw(overrides: Partial<RawWorkOrderRow> = {}): RawWorkOrderRow {
+  return {
+    id: 812n,
+    reference: "WO-23881",
+    landlordPropertyId: "100245",
+    address: "12 High St",
+    postcode: "M1 2AB",
+    workstreamId: WINDOWS,
+    workstreamName: "Windows",
+    contractorOrganisationId: "22222222-2222-2222-2222-222222222222",
+    contractorName: "Contractor A",
+    stageId: 102n,
+    stageName: "In progress",
+    forecastEnd: "2026-07-30",
+    requiredEvidence: 4,
+    satisfiedEvidence: 2,
+    ...overrides,
+  };
+}
+
+describe("toWorkOrderRow", () => {
+  it("serialises every bigint id, which would not survive JSON", () => {
+    const row = toWorkOrderRow(LADDERS, raw(), ASOF);
+    expect(row.id).toBe("812");
+    expect(row.workstreamId).toBe("10");
+    expect(row.stageId).toBe("102");
+  });
+
+  it("keeps the forecast end in YYYY-MM-DD — the table does the formatting", () => {
+    expect(toWorkOrderRow(LADDERS, raw(), ASOF).forecastEnd).toBe("2026-07-30");
+  });
+
+  it("derives progress from the ladder, not from the stage name", () => {
+    expect(toWorkOrderRow(LADDERS, raw({ stageId: 101n }), ASOF).progress).toBe(
+      "not_started",
+    );
+    expect(toWorkOrderRow(LADDERS, raw({ stageId: 102n }), ASOF).progress).toBe(
+      "in_progress",
+    );
+    expect(toWorkOrderRow(LADDERS, raw({ stageId: 103n }), ASOF).progress).toBe(
+      "complete",
+    );
+  });
+
+  it("marks a work order past its forecast day overdue", () => {
+    const row = toWorkOrderRow(LADDERS, raw({ forecastEnd: "2026-07-22" }), ASOF);
+    expect(row.overdue).toBe(true);
+  });
+
+  it("never marks a completed work order overdue, however late it finished", () => {
+    const row = toWorkOrderRow(
+      LADDERS,
+      raw({ stageId: 103n, forecastEnd: "2026-01-01" }),
+      ASOF,
+    );
+    expect(row.overdue).toBe(false);
+  });
+
+  it("does not treat due-today as overdue", () => {
+    expect(
+      toWorkOrderRow(LADDERS, raw({ forecastEnd: "2026-07-23" }), ASOF).overdue,
+    ).toBe(false);
+  });
+
+  it("treats a missing forecast end as never overdue", () => {
+    expect(
+      toWorkOrderRow(LADDERS, raw({ forecastEnd: null }), ASOF).overdue,
+    ).toBe(false);
+  });
+
+  it("reports advisory evidence counts, flagging a shortfall", () => {
+    const row = toWorkOrderRow(LADDERS, raw(), ASOF);
+    expect(row.evidence).toEqual({
+      required: 4,
+      satisfied: 2,
+      missing: 2,
+      ratio: 0.5,
+    });
+    expect(row.missingRequiredEvidence).toBe(true);
+  });
+
+  it("distinguishes 'nothing required' from '0% of requirements met'", () => {
+    const row = toWorkOrderRow(
+      LADDERS,
+      raw({ requiredEvidence: 0, satisfiedEvidence: 0 }),
+      ASOF,
+    );
+    expect(row.evidence.ratio).toBeNull();
+    expect(row.missingRequiredEvidence).toBe(false);
+  });
+
+  it("cannot report over 100% from a stray duplicate submission", () => {
+    const row = toWorkOrderRow(
+      LADDERS,
+      raw({ requiredEvidence: 2, satisfiedEvidence: 5 }),
+      ASOF,
+    );
+    expect(row.evidence).toEqual({
+      required: 2,
+      satisfied: 2,
+      missing: 0,
+      ratio: 1,
+    });
+    expect(row.missingRequiredEvidence).toBe(false);
+  });
+
+  it("degrades honestly on a stage outside the loaded ladders", () => {
+    // Not complete, so still eligible to be overdue — the derivations module's
+    // documented edge case, reached rather than re-decided here.
+    const row = toWorkOrderRow(
+      LADDERS,
+      raw({ stageId: 999n, forecastEnd: "2026-07-01" }),
+      ASOF,
+    );
+    expect(row.progress).toBeNull();
+    expect(row.overdue).toBe(true);
+  });
+
+  it("carries the live stage name through, so a rename propagates", () => {
+    const row = toWorkOrderRow(
+      LADDERS,
+      raw({ stageName: "Awaiting authorisation" }),
+      ASOF,
+    );
+    expect(row.stageName).toBe("Awaiting authorisation");
+  });
+});
diff --git a/src/app/api/projects/[projectId]/work-orders/rows.ts b/src/app/api/projects/[projectId]/work-orders/rows.ts
new file mode 100644
index 00000000..91288ba7
--- /dev/null
+++ b/src/app/api/projects/[projectId]/work-orders/rows.ts
@@ -0,0 +1,135 @@
+/**
+ * Turning a `work_order` row into a table row (issue #419).
+ *
+ * This is where the shared derivations from `@/lib/projects/derivations` (#418)
+ * are applied to a single work order. Nothing here decides what *overdue*,
+ * *complete* or *evidence completeness* mean — every one of those is a call
+ * into that module, so a badge in this table and a KPI on the programme
+ * dashboard cannot drift apart.
+ *
+ * Pure, like the module it wraps: no database client, no React. The query in
+ * `./queries` produces `RawWorkOrderRow` (facts, no judgement); this produces
+ * `WorkOrderRow` (facts plus the derived flags the table renders); the client
+ * component only ever sees the latter.
+ *
+ * Ids are serialised to strings on the way out because `bigint` does not
+ * survive `JSON.stringify` — the same convention the workstreams endpoints use.
+ */
+import {
+  evidenceCompleteness,
+  isMissingRequiredEvidence,
+  isOverdue,
+  progressOfWorkOrder,
+  type EvidenceCompleteness,
+  type StageLadders,
+  type WorkOrderProgress,
+} from "@/lib/projects/derivations";
+
+/**
+ * One work order as the SQL returns it: joined-up facts, pre-judgement.
+ *
+ * `requiredEvidence` / `satisfiedEvidence` are counted against the applicable
+ * `(stage, requirement)` pairs that `requiredEvidenceRequirementIds` produced —
+ * the query never decides applicability itself.
+ */
+export interface RawWorkOrderRow {
+  id: bigint;
+  reference: string;
+  /** `property.landlord_property_id` — the landlord's own asset reference. */
+  landlordPropertyId: string | null;
+  address: string | null;
+  postcode: string | null;
+  /** `project_workstream.id`. */
+  workstreamId: bigint;
+  /** `workstream.name` — reference data, so a rename propagates. */
+  workstreamName: string;
+  contractorOrganisationId: string | null;
+  contractorName: string | null;
+  stageId: bigint;
+  /**
+   * `project_workstream_stage.name`, read live through the work order's stage
+   * FK. The name is never denormalised onto the work order, so a stage rename
+   * shows up here on the next read — an acceptance criterion of #419.
+   */
+  stageName: string;
+  /** `work_order.forecast_end` as Drizzle hands back a `date`: `YYYY-MM-DD`. */
+  forecastEnd: string | null;
+  requiredEvidence: number;
+  satisfiedEvidence: number;
+}
+
+/** One rendered row of the work-orders table. */
+export interface WorkOrderRow {
+  id: string;
+  reference: string;
+  landlordPropertyId: string | null;
+  address: string | null;
+  postcode: string | null;
+  workstreamId: string;
+  workstreamName: string;
+  contractorOrganisationId: string | null;
+  contractorName: string | null;
+  stageId: string;
+  stageName: string;
+  /** `YYYY-MM-DD`, the only date format that crosses this boundary. The table formats it. */
+  forecastEnd: string | null;
+  /** Null when the row's stage was not loaded into the ladders — see derivations. */
+  progress: WorkOrderProgress | null;
+  overdue: boolean;
+  /** Advisory only (CONTEXT.md): counts and badges, never a gate. */
+  evidence: EvidenceCompleteness;
+  missingRequiredEvidence: boolean;
+}
+
+/**
+ * Apply the shared rules to one row.
+ *
+ * `asOf` is the day the caller is measuring against — the *same* day the SQL
+ * filter binds, so a request that straddles midnight cannot classify a row as
+ * overdue in the WHERE clause and not-overdue in the badge.
+ */
+export function toWorkOrderRow(
+  ladders: StageLadders,
+  raw: RawWorkOrderRow,
+  asOf: Date,
+): WorkOrderRow {
+  const derivationInput = {
+    projectWorkstreamStageId: raw.stageId,
+    forecastEnd: raw.forecastEnd,
+  };
+  const evidence = evidenceCompleteness(
+    raw.requiredEvidence,
+    raw.satisfiedEvidence,
+  );
+
+  return {
+    id: raw.id.toString(),
+    reference: raw.reference,
+    landlordPropertyId: raw.landlordPropertyId,
+    address: raw.address,
+    postcode: raw.postcode,
+    workstreamId: raw.workstreamId.toString(),
+    workstreamName: raw.workstreamName,
+    contractorOrganisationId: raw.contractorOrganisationId,
+    contractorName: raw.contractorName,
+    stageId: raw.stageId.toString(),
+    stageName: raw.stageName,
+    forecastEnd: raw.forecastEnd,
+    progress: progressOfWorkOrder(ladders, derivationInput),
+    overdue: isOverdue(ladders, derivationInput, asOf),
+    evidence,
+    missingRequiredEvidence: isMissingRequiredEvidence(evidence),
+  };
+}
+
+/** One page of the table, as the route handler returns it. */
+export interface WorkOrderPage {
+  workOrders: WorkOrderRow[];
+  /**
+   * The cursor that fetches the following page, or null on the last page.
+   * Its presence is how the client knows there is a next page at all.
+   */
+  nextCursor: string | null;
+  /** Work orders matching the filters, ignoring pagination. */
+  total: number;
+}