The all-sessions coverage GET dies: the per-session block is the coverage surface

Extraction-UX close-out interlude (master dispatch 2026-09-24, off UI's
ff1ec7a confirmation): nothing client-side consumes GET /api/graph/coverage
— the sidebar block and the chat-bar ring both read GET /api/chats/[id]'s
coverage block. The dead route (app/api/graph/coverage/route.ts) is
deleted; the manual-extract front door (POST /api/graph/coverage/extract)
stays by design.

No server helper was orphaned — the route was composition-only over
shared seams (chatStore, extractionStatuses, stores, coverageOf). The
sessionCoverage doc + the chats/[id] route comment now point at the
per-session block as THE coverage surface.

Pin (tests/coverage.test.ts): the route file's absence (prompt-overrides'
structural-pin precedent) + the Extract POST's survival — a merge cannot
resurrect the dead surface silently.

tests/coverage.test.ts

@@ -1,5 +1,6 @@
 import assert from "node:assert/strict";
 import { describe, it } from "node:test";
+import * as fs from "node:fs";
 import type { UIMessage } from "ai";
 
 import {
@@ -156,4 +157,16 @@ describe("batchTag — deterministic, ref-stable, mutation-sensitive", () => {
 		const mutated = coverageSlots([user("m1", "aaaa!"), user("m2", "bbbb")]);
 		assert.notEqual(batchTag(slots), batchTag(mutated));
 	});
-});
+});
+describe("the all-sessions coverage GET is dead (extraction-UX close-out, 2026-09-24)", () => {
+	it("the route file is gone — the only coverage endpoint is the Extract POST", () => {
+		// UI confirmation (ff1ec7a): nothing client-side consumes the
+		// all-sessions list anymore — the sidebar block and the ring both
+		// read GET /api/chats/[id]'s coverage block. This pin guards against
+		// a merge resurrecting the dead surface.
+		assert.equal(fs.existsSync("app/api/graph/coverage/route.ts"), false, "the all-sessions GET route is deleted");
+		// stays by design: the manual-extract front door (sidebar block's
+		// Extract affordance) lives on.
+		assert.equal(fs.existsSync("app/api/graph/coverage/extract/route.ts"), true, "the Extract POST survives");
+	});
+});