diff --git a/.changeset/daemon-health-positive-pid.md b/.changeset/daemon-health-positive-pid.md
new file mode 100644
index 000000000..0ad93117e
--- /dev/null
+++ b/.changeset/daemon-health-positive-pid.md
@@ -0,0 +1,5 @@
+---
+"hunkdiff": patch
+---
+
+Reject session daemon health responses that advertise a zero PID.
diff --git a/packages/hunk/src/session/broker/brokerLauncher.test.ts b/packages/hunk/src/session/broker/brokerLauncher.test.ts
index c597e9609..9b6bcba41 100644
--- a/packages/hunk/src/session/broker/brokerLauncher.test.ts
+++ b/packages/hunk/src/session/broker/brokerLauncher.test.ts
@@ -129,7 +129,17 @@ describe("session daemon launcher", () => {
         paths: { health: "/health", socket: "/session" },
       }),
     ).toMatchObject({ ok: true, pid: 123, sessions: 1 });
-    for (const value of [null, [], { ok: "yes" }, { ok: true, pid: 1.5 }, { ok: true, extra: 1 }]) {
+    for (const value of [
+      null,
+      [],
+      { ok: "yes" },
+      { ok: true, pid: 0 },
+      { ok: true, pid: -1 },
+      { ok: true, pid: 1.5 },
+      { ok: true, pid: "123" },
+      { ok: true, pid: Number.MAX_SAFE_INTEGER + 1 },
+      { ok: true, extra: 1 },
+    ]) {
       expect(parseSessionBrokerHealth(value)).toBeNull();
     }
   });
diff --git a/packages/hunk/src/session/broker/brokerLauncher.ts b/packages/hunk/src/session/broker/brokerLauncher.ts
index aabf50fc4..1e734d021 100644
--- a/packages/hunk/src/session/broker/brokerLauncher.ts
+++ b/packages/hunk/src/session/broker/brokerLauncher.ts
@@ -497,13 +497,8 @@ export function parseSessionBrokerHealth(value: unknown): SessionBrokerHealth |
     );
     if (record.ok !== true) return null;
     const parsed: SessionBrokerHealth = { ok: true };
-    for (const key of [
-      "pid",
-      "sessions",
-      "pendingCommands",
-      "uptimeMs",
-      "staleSessionTtlMs",
-    ] as const) {
+    if (record.pid !== undefined) parsed.pid = parseBrokerSafeInteger(record.pid, { minimum: 1 });
+    for (const key of ["sessions", "pendingCommands", "uptimeMs", "staleSessionTtlMs"] as const) {
       if (record[key] !== undefined) parsed[key] = parseBrokerSafeInteger(record[key]);
     }
     for (const key of [