diff --git a/packages/coding-agent/test/internal-urls/registry-helpers.test.ts b/packages/coding-agent/test/internal-urls/registry-helpers.test.ts
new file mode 100644
index 000000000..b4fc9290d
--- /dev/null
+++ b/packages/coding-agent/test/internal-urls/registry-helpers.test.ts
@@ -0,0 +1,121 @@
+/**
+ * Contract: `hasResolvableTranscript` mirrors the availability half of
+ * `HistoryProtocolHandler.resolve` — it must return true exactly when a
+ * `history://<id>` link would serve a transcript (live session, verified
+ * retained session file, or on-disk `.jsonl` under a known artifacts dir),
+ * and false otherwise, without ever throwing. Follow-up hints in
+ * `task/index.ts` gate their `history://` links on it.
+ */
+import { afterEach, beforeEach, describe, expect, it } from "bun:test";
+import * as fs from "node:fs/promises";
+import * as os from "node:os";
+import * as path from "node:path";
+import {
+	hasResolvableTranscript,
+	registerArtifactsDir,
+	resetRegisteredArtifactDirsForTests,
+} from "@oh-my-pi/pi-coding-agent/internal-urls/registry-helpers";
+import { AgentRegistry } from "@oh-my-pi/pi-coding-agent/registry/agent-registry";
+import type { AgentSession } from "@oh-my-pi/pi-coding-agent/session/agent-session";
+import { removeWithRetries } from "@oh-my-pi/pi-utils";
+
+function fakeLiveSession(): AgentSession {
+	return { messages: [] } as unknown as AgentSession;
+}
+
+describe("hasResolvableTranscript", () => {
+	beforeEach(() => {
+		AgentRegistry.resetGlobalForTests();
+		resetRegisteredArtifactDirsForTests();
+	});
+	afterEach(() => {
+		AgentRegistry.resetGlobalForTests();
+		resetRegisteredArtifactDirsForTests();
+	});
+
+	it("returns false for an unknown agent with nothing on disk", async () => {
+		expect(await hasResolvableTranscript("Ghost")).toBe(false);
+	});
+
+	it("returns true for a live session, case-insensitively", async () => {
+		AgentRegistry.global().register({
+			id: "Live",
+			displayName: "task",
+			kind: "sub",
+			session: fakeLiveSession(),
+			status: "idle",
+		});
+		expect(await hasResolvableTranscript("Live")).toBe(true);
+		expect(await hasResolvableTranscript("live")).toBe(true);
+	});
+
+	it("returns false for an aborted ref with no retained session file", async () => {
+		AgentRegistry.global().register({
+			id: "Aborted",
+			displayName: "task",
+			kind: "sub",
+			session: null,
+			sessionFile: null,
+			status: "aborted",
+		});
+		expect(await hasResolvableTranscript("Aborted")).toBe(false);
+	});
+
+	it("returns false when the retained session file no longer exists on disk", async () => {
+		AgentRegistry.global().register({
+			id: "Stale",
+			displayName: "task",
+			kind: "sub",
+			session: null,
+			sessionFile: "/nonexistent/definitely/gone.jsonl",
+			status: "aborted",
+		});
+		expect(await hasResolvableTranscript("Stale")).toBe(false);
+	});
+
+	it("returns true for a parked ref whose session file exists", async () => {
+		const dir = await fs.mkdtemp(path.join(os.tmpdir(), "registry-helpers-"));
+		try {
+			const sessionFile = path.join(dir, "parked.jsonl");
+			await Bun.write(sessionFile, "{}\n");
+			AgentRegistry.global().register({
+				id: "Parked",
+				displayName: "task",
+				kind: "sub",
+				session: null,
+				sessionFile,
+				status: "parked",
+			});
+			expect(await hasResolvableTranscript("Parked")).toBe(true);
+		} finally {
+			await removeWithRetries(dir);
+		}
+	});
+
+	it("falls back to the artifacts-dir disk scan for unregistered agents", async () => {
+		const dir = await fs.mkdtemp(path.join(os.tmpdir(), "registry-helpers-"));
+		try {
+			await Bun.write(path.join(dir, "DiskOnly.jsonl"), "{}\n");
+			const cleanup = registerArtifactsDir(dir);
+			try {
+				expect(await hasResolvableTranscript("DiskOnly")).toBe(true);
+				expect(await hasResolvableTranscript("diskonly")).toBe(true);
+			} finally {
+				cleanup();
+			}
+		} finally {
+			await removeWithRetries(dir);
+		}
+	});
+
+	it("excludes advisor refs, matching history:// visibility", async () => {
+		AgentRegistry.global().register({
+			id: "__advisor1",
+			displayName: "advisor",
+			kind: "advisor",
+			session: fakeLiveSession(),
+			status: "running",
+		});
+		expect(await hasResolvableTranscript("__advisor1")).toBe(false);
+	});
+});