diff --git a/packages/core/src/__tests__/postgres/open-revert-task-lanes.pg.test.ts b/packages/core/src/__tests__/postgres/open-revert-task-lanes.pg.test.ts
new file mode 100644
index 0000000000..be8858a40d
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+++ b/packages/core/src/__tests__/postgres/open-revert-task-lanes.pg.test.ts
@@ -0,0 +1,123 @@
+/*
+FNXC:WorkflowResolvedColumns 2026-07-31-22:50:
+THE OPEN-UNDO QUERY, on a RENAMED board.
+
+`findOpenRevertTaskForSource` answers "is there an OPEN undo task for this source?" — the question
+behind the dashboard's Undo affordance. It answers it by EXCLUDING the finished lanes, so a prior
+undo attempt that already landed does not keep rendering as open.
+
+WHY THIS FILE EXISTS. That exclusion was converted to
+`resolveProjectColumnsForRoles(this, ["complete", "archived"])`, and blinding it back to
+`ne(column,"archived"), ne(column,"done")` left the whole 16-file lane-detector set green — no test
+in `packages/core` reaches this method at all. The dashboard-side twin (`taskRevert.ts`, #3129) has
+tests; the store-side query behind it did not.
+
+WHAT BREAKS WITHOUT THE CONVERSION. On a board whose complete lane is `shipped`, neither literal
+matches, so a DONE undo task is never excluded and `findOpenRevertTaskForSource` keeps returning it.
+The card shows an undo already in flight forever, and the real affordance is unreachable. Nothing
+errors — the button is just permanently wrong.
+
+DIFFERENTIAL. The same seeded rows are queried under two vocabularies whose traits are identical and
+only the ids differ; `shipped` collides with no legacy id, so a surviving `'done'` cannot pass by
+luck. The default-vocabulary cases are the control: they pass with or without the conversion.
+*/
+
+import { afterAll, afterEach, beforeAll, beforeEach, expect, it } from "vitest";
+import { sql } from "drizzle-orm";
+import {
+  createSharedPgTaskStoreTestHarness,
+  pgDescribe,
+  type SharedPgTaskStoreHarness,
+} from "../../__test-utils__/pg-test-harness.js";
+import { BUILTIN_CODING_WORKFLOW_IR } from "../../builtin-coding-workflow-ir.js";
+
+const AT = "2026-06-15T12:00:00.000Z";
+
+pgDescribe("findOpenRevertTaskForSource under a renamed board vocabulary", () => {
+  const h: SharedPgTaskStoreHarness = createSharedPgTaskStoreTestHarness({
+    prefix: "fusion_open_revert_lanes",
+  });
+
+  beforeAll(h.beforeAll);
+  beforeEach(h.beforeEach);
+  afterEach(h.afterEach);
+  afterAll(h.afterAll);
+
+  /** The builtin workflow with only its column ids renamed; traits are untouched. */
+  async function seedRenamedWorkflow(): Promise<void> {
+    const RENAME: Record<string, string> = {
+      todo: "drafting",
+      "in-progress": "building",
+      "in-review": "checking",
+      done: "shipped",
+      archived: "vaulted",
+    };
+    const rename = (id: string | undefined) => (id && RENAME[id]) ?? id;
+    const ir = JSON.parse(JSON.stringify(BUILTIN_CODING_WORKFLOW_IR)) as {
+      id: string;
+      nodes?: { column?: string }[];
+      columns?: { id: string }[];
+    };
+    ir.id = "custom:renamed-open-revert";
+    for (const node of ir.nodes ?? []) node.column = rename(node.column);
+    for (const column of ir.columns ?? []) column.id = rename(column.id) as string;
+
+    const ids = (ir.columns ?? []).map((column) => column.id);
+    expect(ids).toContain("shipped");
+    expect(ids).not.toContain("done");
+
+    await h.store().createWorkflowDefinition({ name: "Renamed", kind: "workflow", ir } as never);
+  }
+
+  /** A source task plus an undo task pointing at it, parked in `revertLane`. */
+  async function seedRevertPair(revertLane: string): Promise<void> {
+    const store = h.store();
+    const adminDb = h.adminDb();
+    for (const id of ["KB-SRC", "KB-REV"]) {
+      await store.createTaskWithReservedId(
+        { description: id, column: "todo" },
+        { taskId: id, createdAt: AT, updatedAt: AT, applyDefaultWorkflowSteps: false },
+      );
+    }
+    /* Seeded directly: `sourceMetadata.revertOf` is the join this query reads, and moveTask would
+       reject a target column the default workflow does not declare. */
+    await adminDb.execute(sql`
+      UPDATE project.tasks
+         SET "column" = ${revertLane}, source_metadata = ${JSON.stringify({ revertOf: "KB-SRC" })}::jsonb
+       WHERE id = 'KB-REV'`);
+    store.taskCache.delete("KB-REV");
+  }
+
+  it("default vocabulary: a FINISHED undo task is not reported as open", async () => {
+    await seedRevertPair("done");
+
+    expect(await h.store().findOpenRevertTaskForSource("KB-SRC")).toBeNull();
+  });
+
+  it("renamed vocabulary: an undo task in the RENAMED complete lane is not reported as open", async () => {
+    await seedRenamedWorkflow();
+    await seedRevertPair("shipped");
+
+    expect(await h.store().findOpenRevertTaskForSource("KB-SRC")).toBeNull();
+  });
+
+  it("renamed vocabulary: an undo task in the RENAMED archived lane is not reported as open", async () => {
+    await seedRenamedWorkflow();
+    await seedRevertPair("vaulted");
+
+    expect(await h.store().findOpenRevertTaskForSource("KB-SRC")).toBeNull();
+  });
+
+  /*
+  The paired positive. Excluding the finished lanes must not degrade into excluding everything — an
+  undo that really IS open still has to be found, or the affordance breaks in the other direction
+  and no undo is ever reported in flight.
+  */
+  it("renamed vocabulary: an undo task still in a WORKING lane IS reported as open", async () => {
+    await seedRenamedWorkflow();
+    await seedRevertPair("building");
+
+    const open = await h.store().findOpenRevertTaskForSource("KB-SRC");
+    expect(open?.id).toBe("KB-REV");
+  });
+});