fix(session): report daemon reachability in session list JSON

.changeset/session-list-daemon-status.md

@@ -0,0 +1,5 @@
+---
+"hunkdiff": patch
+---
+
+Report whether the session daemon is reachable in `hunk session list --json` so callers can tell a down daemon from an empty session set.

src/session/agent/commands.daemon.test.ts

@@ -56,7 +56,7 @@ describe("resolveDaemonAvailability with no daemon listening", () => {
       action: "list",
       output: "json",
     } satisfies SessionCommandInput);
-    expect(JSON.parse(output)).toEqual({ sessions: [] });
+    expect(JSON.parse(output)).toEqual({ sessions: [], daemon: { available: false } });
   });
 
   probeTest(

src/session/agent/commands.test.ts

@@ -951,6 +951,50 @@ describe("session command compatibility checks", () => {
     expect(output).toBe("No active Hunk sessions.\n");
   });
 
+  // Intent: the JSON list value must distinguish a down daemon (available: false) from a healthy
+  // daemon with zero sessions (available: true). Text output stays unchanged in both states.
+  test("list reports daemon unavailable in JSON when no daemon is present", async () => {
+    setSessionCommandTestHooks({
+      createClient: () => {
+        throw new Error("list should not create a client without a daemon");
+      },
+      resolveDaemonAvailability: async () => false,
+    });
+
+    const output = await runSessionCommand({
+      kind: "session",
+      action: "list",
+      output: "json",
+    } satisfies SessionCommandInput);
+
+    expect(JSON.parse(output)).toEqual({
+      sessions: [],
+      daemon: { available: false },
+    });
+  });
+
+  test("list reports daemon available in JSON when a daemon is present", async () => {
+    setSessionCommandTestHooks({
+      createClient: () =>
+        createClient({
+          listSessions: async () => [createTestListedSession("session-1")],
+        }),
+      resolveDaemonAvailability: async () => true,
+    });
+
+    const output = await runSessionCommand({
+      kind: "session",
+      action: "list",
+      output: "json",
+    } satisfies SessionCommandInput);
+
+    const parsed = JSON.parse(output);
+    expect(parsed.daemon).toEqual({ available: true });
+    expect(parsed).toMatchObject({
+      sessions: [{ sessionId: "session-1" }],
+    });
+  });
+
   // Intent: remaining command branches dispatch to the daemon and keep text output stable.
   test("routes remaining session actions through the daemon and formats text output", async () => {
     const selector: SessionSelectorInput = { sessionId: "session-1" };

src/session/agent/commands.ts

@@ -176,7 +176,11 @@ export async function runSessionCommand(input: SessionCommandInput) {
     input.action,
   ) ?? resolveDaemonAvailability(input.action));
   if (!daemonAvailable && input.action === "list") {
-    return renderOutput(input.output, { sessions: [] }, () => formatListOutput([]));
+    // Report daemon reachability in the JSON value so callers can tell a down daemon from a
+    // healthy daemon with zero sessions — both otherwise render an empty session list.
+    return renderOutput(input.output, { sessions: [], daemon: { available: false } }, () =>
+      formatListOutput([]),
+    );
   }
 
   const normalizedSelector = "selector" in input ? normalizeSessionSelector(input.selector) : null;
@@ -188,7 +192,9 @@ export async function runSessionCommand(input: SessionCommandInput) {
   switch (input.action) {
     case "list": {
       const sessions = await client.listSessions();
-      return renderOutput(input.output, { sessions }, () => formatListOutput(sessions));
+      return renderOutput(input.output, { sessions, daemon: { available: true } }, () =>
+        formatListOutput(sessions),
+      );
     }
     case "get": {
       const session = await client.getSession(normalizedSelector!);