diff --git a/implementations/Crafter.Debug.Cli-Client.cpp b/implementations/Crafter.Debug.Cli-Client.cpp
index f52a180..3cbb467 100644
--- a/implementations/Crafter.Debug.Cli-Client.cpp
+++ b/implementations/Crafter.Debug.Cli-Client.cpp
@@ -360,10 +360,15 @@ namespace {
             const bool alive = std::ranges::any_of(env.list(), [&](const Instance& candidate) { return candidate.record.instanceId == instance->record.instanceId; });
             if (!alive) {
                 Err() << std::format("crafter-debug: {} has exited\n", instance->record.name);
-            } else {
-                Err() << std::format("crafter-debug: cannot reach {} on port {}: {}\n", instance->record.name, instance->record.port, why);
+                return exitNoInstance;
             }
-            return exitNoInstance;
+            // Its lock says it lives, yet not even the handshake is
+            // answered: the whole process is stopped, by a debugger most
+            // likely, or its network threads are stuck.
+            Err() << std::format("crafter-debug: {} is alive but not answering on port {} ({}): stopped in a debugger, or hung.\n",
+                                 instance->record.name, instance->record.port, why);
+            PrintAttach(true);
+            return exitTimeout;
         }
 
         // A request that got no reply. The app may be gone, stopped in a
@@ -398,7 +403,8 @@ namespace {
         void PrintAttach(bool toErr) {
             std::ostream& stream = toErr ? Err() : Out();
             const InstanceRecord& record = instance->record;
-            const std::string debugger = env.haveLldb && env.haveLldb() ? "lldb" : "gdb";
+            const std::string lldb = env.lldb ? env.lldb() : std::string();
+            const std::string debugger = lldb.empty() ? std::string("gdb") : lldb;
             if (!record.flatpakInstance.empty()) {
                 stream << std::format("  attach (on the host): flatpak enter {} {} -p {}\n", record.flatpakInstance, debugger, record.pid);
                 stream << std::format("  check whether a debugger holds it: flatpak enter {} grep State /proc/{}/status   (t = stopped by a tracer)\n", record.flatpakInstance, record.pid);
diff --git a/implementations/main.cpp b/implementations/main.cpp
index fb59d17..d0e4f57 100644
--- a/implementations/main.cpp
+++ b/implementations/main.cpp
@@ -17,7 +17,12 @@ int main(int argc, char** argv) {
     {
         Cli::Environment environment;
         environment.connect = Cli::ConnectQuic;
-        environment.haveLldb = [] { return std::filesystem::exists("/app/bin/lldb") || std::filesystem::exists("/usr/bin/lldb"); };
+        environment.lldb = [] {
+            for (const char* path : { "/app/bin/lldb", "/usr/bin/lldb" }) {
+                if (std::filesystem::exists(path)) return std::string(path);
+            }
+            return std::string();
+        };
         // Run closes its connections before it returns.
         code = Cli::Run(args, environment);
     }
diff --git a/interfaces/Crafter.Debug.Cli-Client.cppm b/interfaces/Crafter.Debug.Cli-Client.cppm
index 5d8dd09..02d56d4 100644
--- a/interfaces/Crafter.Debug.Cli-Client.cppm
+++ b/interfaces/Crafter.Debug.Cli-Client.cppm
@@ -58,8 +58,10 @@ export namespace Crafter::Debug::Cli {
         std::ostream* err = &std::cerr;
         // Where a screenshot without -o goes, relative paths included.
         std::filesystem::path cwd = std::filesystem::current_path();
-        // Whether `lldb` exists here, for the attach command `debugger` prints.
-        std::function<bool()> haveLldb;
+        // Where lldb is here, for the attach command `debugger` prints: its
+        // absolute path, since `flatpak enter` runs a command without the
+        // sandbox's PATH, which /app/bin is on. Empty for none: gdb then.
+        std::function<std::string()> lldb;
     };
 
     std::int32_t Run(std::span<const std::string_view> args, Environment& environment);
diff --git a/tests/ShouldRunClientCommands/main.cpp b/tests/ShouldRunClientCommands/main.cpp
index 28451e3..2817e04 100644
--- a/tests/ShouldRunClientCommands/main.cpp
+++ b/tests/ShouldRunClientCommands/main.cpp
@@ -85,7 +85,7 @@ namespace {
         environment.out = &out;
         environment.err = &err;
         environment.cwd = fs::temp_directory_path() / "crafter-debug-ShouldRunClientCommands";
-        environment.haveLldb = [] { return false; };
+        environment.lldb = [] { return std::string(); };
         const std::int32_t code = Cli::Run(args, environment);
         return { code, out.str(), err.str() };
     }
diff --git a/tests/ShouldServeOverQuic/main.cpp b/tests/ShouldServeOverQuic/main.cpp
index e9d6096..9b39170 100644
--- a/tests/ShouldServeOverQuic/main.cpp
+++ b/tests/ShouldServeOverQuic/main.cpp
@@ -14,7 +14,9 @@
 //    connections, each get their own reply;
 //  - destroying the Session answers a waiting follower and closes promptly
 //    with a client still connected, and a client then finds the port dead
-//    within seconds.
+//    within seconds;
+//  - an instance alive by its lock but silent at its port, as one a
+//    debugger holds, is reported as such with how to attach, not as gone.
 #include <stdio.h>
 #include <stdlib.h>
 import std;
@@ -58,7 +60,7 @@ namespace {
         environment.connect = Cli::ConnectQuic;
         environment.out = &out;
         environment.err = &err;
-        environment.haveLldb = [] { return false; };
+        environment.lldb = [] { return std::string(); };
         const std::int32_t code = Cli::Run(args, environment);
         return { code, out.str(), err.str() };
     }
@@ -259,6 +261,15 @@ int main() {
     Check(!reply && reply.error().kind == Cli::CallError::Kind::Unreachable && deadTook < 5s,
           std::format("a client finds the port dead in {} ms", std::chrono::duration_cast<std::chrono::milliseconds>(deadTook).count()));
 
+    // Alive by its lock, with nothing answering at its port: what a client
+    // sees of an app a debugger holds.
+    {
+        const Registration stopped(InstanceRecord{ .name = "held", .port = record.port, .token = "t", .protocol = protocolVersion, .sourceId = std::string(Detail::SourceId()) });
+        const Ran held = Run({ "status" });
+        Check(held.code == 5 && Has(held.err, "alive but not answering") && Has(held.err, "attach"),
+              std::format("an app alive but silent is reported as held, with how to attach (exit {}: {})", held.code, held.err));
+    }
+
     std::fflush(stdout);
     std::_Exit(failures == 0 ? 0 : 1);
 }