diff --git a/common/arg.cpp b/common/arg.cpp
index a287b907d490..9753441313a7 100644
--- a/common/arg.cpp
+++ b/common/arg.cpp
@@ -850,8 +850,9 @@ static bool common_params_parse_ex(int argc, char ** argv, common_params_context
         params.kv_overrides.back().key[0] = 0;
     }
 
-    if (!params.server_tools.empty() && !params.cors_origins_explicit) {
-        LOG_WRN("server tools are enabled, using localhost as default CORS origin (change via --cors-origins)\n");
+    const bool mcp_enabled = !params.mcp_servers_config.empty() || !params.mcp_servers_json.empty();
+    if ((!params.server_tools.empty() || mcp_enabled) && !params.cors_origins_explicit) {
+        LOG_WRN("server tools or MCP servers are enabled, using localhost as default CORS origin (change via --cors-origins)\n");
         params.cors_origins = "localhost";
     }
 
@@ -3261,6 +3262,22 @@ common_params_context common_params_parser_init(common_params & params, llama_ex
             params.server_tools = parse_csv_row(value);
         }
     ).set_examples({LLAMA_EXAMPLE_SERVER}).set_env("LLAMA_ARG_TOOLS"));
+    add_opt(common_arg(
+        {"--mcp-servers-config"}, "PATH",
+        "experimental: path to JSON file with MCP server definitions (Cursor-compatible format) - do not enable in untrusted environments (default: none)\n"
+        "note: for security reasons, this will limit --cors-origins to localhost by default",
+        [](common_params & params, const std::string & value) {
+            params.mcp_servers_config = value;
+        }
+    ).set_examples({LLAMA_EXAMPLE_SERVER}).set_env("LLAMA_ARG_MCP_SERVERS_CONFIG"));
+    add_opt(common_arg(
+        {"--mcp-servers-json"}, "JSON",
+        "experimental: inline JSON with MCP server definitions (Cursor-compatible format) - do not enable in untrusted environments (default: none)\n"
+        "note: for security reasons, this will limit --cors-origins to localhost by default",
+        [](common_params & params, const std::string & value) {
+            params.mcp_servers_json = value;
+        }
+    ).set_examples({LLAMA_EXAMPLE_SERVER}).set_env("LLAMA_ARG_MCP_SERVERS_JSON"));
     add_opt(common_arg(
         {"-ag", "--agent"},
         {"-no-ag", "--no-agent"},
diff --git a/common/common.h b/common/common.h
index cb1827f5dd24..e7a0e2c29bcb 100644
--- a/common/common.h
+++ b/common/common.h
@@ -668,6 +668,10 @@ struct common_params {
     // enable built-in tools
     std::vector<std::string> server_tools;
 
+    // MCP server configs (Cursor-compatible JSON)
+    std::string mcp_servers_config;   // path to JSON file with MCP server definitions
+    std::string mcp_servers_json;     // inline JSON with MCP server definitions
+
     // router server configs
     std::string models_dir    = "";     // directory containing models for the router server
     std::string models_preset = "";     // directory containing model presets for the router server
diff --git a/tools/server/server-common.h b/tools/server/server-common.h
index 74780b96e2e6..4969fe73cbb2 100644
--- a/tools/server/server-common.h
+++ b/tools/server/server-common.h
@@ -393,6 +393,10 @@ struct server_pipe {
     std::atomic<bool> writer_closed{false};
     std::atomic<bool> reader_closed{false};
 
+    // 0 = unbounded (default)
+    // > 0, write() drops the oldest item once the queue is full
+    size_t max_size = 0;
+
     void close_write() {
         writer_closed.store(true, std::memory_order_relaxed);
         cv.notify_all();
@@ -428,6 +432,11 @@ struct server_pipe {
         if (reader_closed.load()) {
             return false; // broken pipe
         }
+        if (max_size > 0) {
+            while (queue.size() >= max_size) {
+                queue.pop(); // drop oldest to stay bounded
+            }
+        }
         queue.push(std::move(data));
         cv.notify_one();
         return true;
diff --git a/tools/server/server-mcp.cpp b/tools/server/server-mcp.cpp
index bf209c3e3a36..22b64040f257 100644
--- a/tools/server/server-mcp.cpp
+++ b/tools/server/server-mcp.cpp
@@ -2,30 +2,113 @@
 
 #include <sheredom/subprocess.h>
 
+#include <atomic>
+#include <chrono>
 #include <cstdio>
-#include <cstring>
 #include <fstream>
+#include <functional>
+#include <sstream>
+#include <thread>
 
 #if defined(_WIN32)
+#  include <io.h>
 #  include <windows.h>
 #else
+#  include <errno.h>
+#  include <fcntl.h>
+#  include <poll.h>
+#  include <unistd.h>
 extern char ** environ;
 #endif
 
-//
-// server_mcp_server_config
-//
-
-std::vector<server_mcp_server_config> server_mcp_server_config::parse_from_file(const std::string & path) {
-    std::ifstream f(path);
+// read NDJSON lines from a child pipe, calling on_line per line until `running` clears, EOF/error, or on_line returns false.
+// polled, not blocking: a grandchild can inherit the pipe's write end and hold it open (terminate() kills only the direct child), so a blocking read would hang teardown on an EOF that never comes.
+static void mcp_pump_ndjson(FILE * f, std::atomic<bool> & running,
+                            const std::function<bool(std::string &&)> & on_line) {
     if (!f) {
-        throw std::runtime_error("failed to open MCP config file: " + path);
+        return;
+    }
+    const int poll_ms = 50;
+#if defined(_WIN32)
+    HANDLE h = (HANDLE) _get_osfhandle(_fileno(f));
+#else
+    int fd = fileno(f);
+    int fl = fcntl(fd, F_GETFL, 0);
+    if (fl >= 0) {
+        fcntl(fd, F_SETFL, fl | O_NONBLOCK);
+    }
+#endif
+    std::string buf;
+    char        chunk[4096];
+    while (running.load()) {
+        size_t n = 0;
+#if defined(_WIN32)
+        DWORD avail = 0;
+        if (!PeekNamedPipe(h, NULL, 0, NULL, &avail, NULL)) {
+            break; // pipe broken / child gone
+        }
+        if (avail == 0) {
+            std::this_thread::sleep_for(std::chrono::milliseconds(poll_ms));
+            continue;
+        }
+        DWORD to_read = avail < (DWORD) sizeof(chunk) ? avail : (DWORD) sizeof(chunk);
+        DWORD got     = 0;
+        if (!ReadFile(h, chunk, to_read, &got, NULL) || got == 0) {
+            break;
+        }
+        n = (size_t) got;
+#else
+        struct pollfd pfd;
+        pfd.fd      = fd;
+        pfd.events  = POLLIN;
+        pfd.revents = 0;
+        int pr      = poll(&pfd, 1, poll_ms);
+        if (pr < 0) {
+            if (errno == EINTR) {
+                continue;
+            }
+            break;
+        }
+        if (pr == 0) {
+            continue; // timeout -> re-check running
+        }
+        if (pfd.revents & (POLLERR | POLLNVAL)) {
+            break;
+        }
+        ssize_t r = read(fd, chunk, sizeof(chunk));
+        if (r < 0) {
+            if (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK) {
+                continue;
+            }
+            break;
+        }
+        if (r == 0) {
+            break; // EOF: child (and any pipe writers) closed the stream
+        }
+        n = (size_t) r;
+#endif
+        buf.append(chunk, n);
+        size_t pos;
+        while ((pos = buf.find('\n')) != std::string::npos) {
+            std::string line = buf.substr(0, pos);
+            buf.erase(0, pos + 1);
+            if (!line.empty() && line.back() == '\r') {
+                line.pop_back();
+            }
+            if (line.empty()) {
+                continue;
+            }
+            if (!on_line(std::move(line))) {
+                return;
+            }
+        }
     }
-    json j;
-    f >> j;
-    return parse_cursor_format(j);
 }
 
+//
+// server_mcp_server_config
+//
+
 std::vector<server_mcp_server_config> server_mcp_server_config::parse_from_json(const std::string & json_str) {
     return parse_cursor_format(json::parse(json_str));
 }
@@ -107,8 +190,7 @@ json server_mcp_transport::send_rpc(const json & request, const std::function<bo
             }
             continue; // skip malformed frame
         }
-        // a message without an id is a notification; a mismatched id is a stale reply from an
-        // earlier timed-out request (ids are monotonic, so it can never match a future one)
+        // no id: a notification. mismatched id: a stale reply from a timed-out request (ids are monotonic, never a future one)
         if (!has_id || (reply.contains("id") && reply.at("id") == request.at("id"))) {
             return reply;
         }
@@ -227,15 +309,91 @@ struct server_mcp_stdio::process_handle {
     FILE * err = nullptr; // child stderr
 };
 
+#if defined(_WIN32)
+// config strings are UTF-8 (from JSON) and subprocess.h converts them with CP_UTF8, so inputs must be UTF-8, not the active code page
+static std::wstring windows_utf8_to_wide(const std::string & s) {
+    if (s.empty()) {
+        return std::wstring();
+    }
+    int n = MultiByteToWideChar(CP_UTF8, 0, s.data(), (int) s.size(), NULL, 0);
+    if (n <= 0) {
+        return std::wstring();
+    }
+    std::wstring w((size_t) n, L'\0');
+    MultiByteToWideChar(CP_UTF8, 0, s.data(), (int) s.size(), &w[0], n);
+    return w;
+}
+
+static std::string windows_wide_to_utf8(const wchar_t * s, int len /* -1 for NUL-terminated */) {
+    int n = WideCharToMultiByte(CP_UTF8, 0, s, len, NULL, 0, NULL, NULL);
+    if (n <= 0) {
+        return std::string();
+    }
+    std::string out((size_t) n, '\0');
+    WideCharToMultiByte(CP_UTF8, 0, s, len, &out[0], n, NULL, NULL);
+    if (len == -1 && !out.empty() && out.back() == '\0') {
+        out.pop_back(); // drop the terminator WideCharToMultiByte counts for -1
+    }
+    return out;
+}
+#endif
+
+static std::string mcp_resolve_command(const std::string & command) {
+#if defined(_WIN32)
+    // For Windows: make sure we handle ".exe" correctly, as well as UTF-8
+    std::wstring wcmd = windows_utf8_to_wide(command);
+    wchar_t      buf[MAX_PATH * 4];
+    const DWORD  cap = (DWORD) (sizeof(buf) / sizeof(buf[0]));
+
+    auto search = [&](const wchar_t * ext) -> std::string {
+        DWORD n = SearchPathW(NULL, wcmd.c_str(), ext, cap, buf, NULL);
+        return (n > 0 && n < cap) ? windows_wide_to_utf8(buf, (int) n) : std::string();
+    };
+
+    std::string found = search(NULL); // exact path / already-extensioned / .exe on PATH
+    if (!found.empty()) {
+        return found;
+    }
+
+    std::wstring pathext;
+    DWORD        need = GetEnvironmentVariableW(L"PATHEXT", NULL, 0);
+    if (need > 0) {
+        pathext.resize(need);
+        DWORD got = GetEnvironmentVariableW(L"PATHEXT", &pathext[0], need);
+        pathext.resize(got);
+    }
+    if (pathext.empty()) {
+        pathext = L".COM;.EXE;.BAT;.CMD";
+    }
+    for (size_t start = 0; start <= pathext.size();) {
+        size_t       sep = pathext.find(L';', start);
+        std::wstring ext = pathext.substr(start, sep == std::wstring::npos ? std::wstring::npos : sep - start);
+        if (!ext.empty()) {
+            found = search(ext.c_str());
+            if (!found.empty()) {
+                return found;
+            }
+        }
+        if (sep == std::wstring::npos) {
+            break;
+        }
+        start = sep + 1;
+    }
+    return command; // give up and let subprocess.h report the spawn error
+#else
+    return command;
+#endif // _WIN32
+}
+
 static std::vector<std::string> mcp_parent_env() {
     std::vector<std::string> env;
 #if defined(_WIN32)
-    LPCH block = GetEnvironmentStringsA();
+    LPWCH block = GetEnvironmentStringsW();
     if (block) {
-        for (LPCH e = block; *e; e += strlen(e) + 1) {
-            env.emplace_back(e);
+        for (LPWCH e = block; *e; e += wcslen(e) + 1) {
+            env.emplace_back(windows_wide_to_utf8(e, -1));
         }
-        FreeEnvironmentStringsA(block);
+        FreeEnvironmentStringsW(block);
     }
 #else
     if (environ) {
@@ -266,6 +424,8 @@ static std::vector<std::string> mcp_build_env(const std::map<std::string, std::s
 server_mcp_stdio::server_mcp_stdio(const server_mcp_server_config & config) : config(config) {
     name = config.name;
     timeout_ms = config.timeout_ms;
+    // bound the reply queue: send_rpc only drains during a call, so unsolicited notifications would otherwise grow it without limit
+    from_server.max_size = 65536;
 }
 
 server_mcp_stdio::~server_mcp_stdio() {
@@ -274,7 +434,7 @@ server_mcp_stdio::~server_mcp_stdio() {
 
 bool server_mcp_stdio::start() {
     std::vector<std::string> argv_s;
-    argv_s.push_back(config.command);
+    argv_s.push_back(mcp_resolve_command(config.command));
     argv_s.insert(argv_s.end(), config.args.begin(), config.args.end());
 
     int options = subprocess_option_no_window | subprocess_option_search_user_path;
@@ -327,33 +487,77 @@ bool server_mcp_stdio::is_alive() const {
 }
 
 void server_mcp_stdio::reader_loop() {
-    std::string buf;
-    char chunk[4096];
-    for (;;) {
-        size_t n = fread(chunk, 1, sizeof(chunk), proc->out);
-        if (n == 0) {
-            break; // EOF or error
-        }
-        buf.append(chunk, n);
+    mcp_pump_ndjson(proc->out, running, [this](std::string && line) {
+        return from_server.write(std::move(line)); // false => consumer gone, stop
+    });
+    running.store(false);
+    to_server.close_write();   // stop the writer
+    from_server.close_write(); // EOF to any waiting caller
+}
 
-        size_t pos;
-        while ((pos = buf.find('\n')) != std::string::npos) {
-            std::string line = buf.substr(0, pos);
-            buf.erase(0, pos + 1);
-            if (!line.empty() && line.back() == '\r') {
-                line.pop_back();
+// write all of `data` to child stdin, non-blocking and polled so teardown never hangs (a grandchild can hold the read end of a full pipe open). returns false on error/close/shutdown.
+static bool mcp_write_all(FILE * f, const std::string & data, std::atomic<bool> & running) {
+    if (!f) {
+        return false;
+    }
+    size_t total = 0;
+#if defined(_WIN32)
+    HANDLE h      = (HANDLE) _get_osfhandle(_fileno(f));
+    DWORD  nowait = PIPE_NOWAIT;
+    SetNamedPipeHandleState(h, &nowait, NULL, NULL);
+    while (total < data.size() && running.load()) {
+        DWORD written = 0;
+        BOOL  ok      = WriteFile(h, data.data() + total, (DWORD) (data.size() - total), &written, NULL);
+        if (ok && written > 0) {
+            total += written;
+            continue;
+        }
+        if (!ok) {
+            DWORD err = GetLastError();
+            if (err != ERROR_NO_DATA && err != ERROR_PIPE_BUSY) {
+                return false;
             }
-            if (line.empty()) {
+        }
+        std::this_thread::sleep_for(std::chrono::milliseconds(1));
+    }
+#else
+    int fd = fileno(f);
+    int fl = fcntl(fd, F_GETFL, 0);
+    if (fl >= 0) {
+        fcntl(fd, F_SETFL, fl | O_NONBLOCK);
+    }
+    while (total < data.size() && running.load()) {
+        ssize_t n = write(fd, data.data() + total, data.size() - total);
+        if (n > 0) {
+            total += (size_t) n;
+            continue;
+        }
+        if (n == 0) {
+            return false;
+        }
+        if (errno == EINTR) {
+            continue;
+        }
+        if (errno != EAGAIN && errno != EWOULDBLOCK) {
+            return false;
+        }
+        struct pollfd pfd;
+        pfd.fd      = fd;
+        pfd.events  = POLLOUT;
+        pfd.revents = 0;
+        int pr      = poll(&pfd, 1, 50);
+        if (pr < 0) {
+            if (errno == EINTR) {
                 continue;
             }
-            if (!from_server.write(std::move(line))) {
-                return; // consumer gone
-            }
+            return false;
+        }
+        if (pfd.revents & (POLLERR | POLLNVAL | POLLHUP)) {
+            return false;
         }
     }
-    running.store(false);
-    to_server.close_write();   // stop the writer
-    from_server.close_write(); // EOF to any waiting caller
+#endif
+    return total == data.size();
 }
 
 void server_mcp_stdio::writer_loop() {
@@ -361,8 +565,8 @@ void server_mcp_stdio::writer_loop() {
     std::string msg;
     while (to_server.read(msg, should_stop)) {
         msg.push_back('\n');
-        if (fwrite(msg.data(), 1, msg.size(), proc->in) != msg.size() || fflush(proc->in) != 0) {
-            break; // child gone
+        if (!mcp_write_all(proc->in, msg, running)) {
+            break; // child gone or shutting down
         }
     }
     running.store(false);
@@ -372,35 +576,18 @@ void server_mcp_stdio::writer_loop() {
 
 void server_mcp_stdio::errlog_loop() {
     static constexpr size_t ERR_TAIL_MAX = 4096;
-    std::string buf;
-    char chunk[4096];
-    for (;;) {
-        size_t n = fread(chunk, 1, sizeof(chunk), proc->err);
-        if (n == 0) {
-            break;
+    // drain stderr (an undrained pipe blocks the child):
+    // log it, and keep a bounded tail for reporting when the server dies
+    mcp_pump_ndjson(proc->err, running, [this](std::string && line) {
+        SRV_DBG("MCP '%s' stderr: %s\n", name.c_str(), line.c_str());
+        std::lock_guard<std::mutex> lk(err_mu);
+        err_tail += line;
+        err_tail += '\n';
+        if (err_tail.size() > ERR_TAIL_MAX) {
+            err_tail.erase(0, err_tail.size() - ERR_TAIL_MAX);
         }
-        buf.append(chunk, n);
-
-        size_t pos;
-        while ((pos = buf.find('\n')) != std::string::npos) {
-            std::string line = buf.substr(0, pos);
-            buf.erase(0, pos + 1);
-            if (!line.empty() && line.back() == '\r') {
-                line.pop_back();
-            }
-            if (line.empty()) {
-                continue;
-            }
-            SRV_DBG("MCP '%s' stderr: %s\n", name.c_str(), line.c_str());
-
-            std::lock_guard<std::mutex> lk(err_mu);
-            err_tail += line;
-            err_tail += '\n';
-            if (err_tail.size() > ERR_TAIL_MAX) {
-                err_tail.erase(0, err_tail.size() - ERR_TAIL_MAX);
-            }
-        }
-    }
+        return true;
+    });
 }
 
 void server_mcp_stdio::join_pumps() {
@@ -428,9 +615,6 @@ void server_mcp_stdio::join_pumps() {
 
 static constexpr int MCP_COOLDOWN_SECONDS = 5;
 
-server_mcp::server_mcp(std::vector<server_mcp_server_config> configs)
-    : configs(std::move(configs)) {}
-
 server_mcp::~server_mcp() {
     shutdown();
 
@@ -464,7 +648,35 @@ const server_mcp_server_config * server_mcp::find_config(const std::string & nam
     return nullptr;
 }
 
-void server_mcp::start() {
+void server_mcp::start(const common_params & params) {
+    auto append = [this](const std::string & json_str) {
+        try {
+            auto parsed = server_mcp_server_config::parse_from_json(json_str);
+            if (parsed.empty()) {
+                SRV_WRN("%s", "MCP config: no servers found in JSON\n");
+            }
+            configs.insert(configs.end(), std::make_move_iterator(parsed.begin()), std::make_move_iterator(parsed.end()));
+        } catch (const std::exception & e) {
+            throw std::runtime_error(std::string("failed to parse MCP config JSON: ") + e.what());
+        }
+    };
+    if (!params.mcp_servers_config.empty()) {
+        std::ifstream f = fs_open_ifstream(params.mcp_servers_config, std::ios::in);
+        if (!f) {
+            throw std::runtime_error("failed to open MCP config file: " + params.mcp_servers_config);
+        }
+        std::stringstream ss;
+        ss << f.rdbuf();
+        append(ss.str());
+    }
+    if (!params.mcp_servers_json.empty()) {
+        append(params.mcp_servers_json);
+    }
+
+    if (configs.empty()) {
+        return;
+    }
+
     auto should_stop = [this]() { return stopping.load(); };
 
     std::vector<server_mcp_tool_def> discovered;
diff --git a/tools/server/server-mcp.h b/tools/server/server-mcp.h
index f5488bf31a81..ca4f5abc02c1 100644
--- a/tools/server/server-mcp.h
+++ b/tools/server/server-mcp.h
@@ -24,8 +24,7 @@ struct server_mcp_server_config {
     std::string cwd;
     int timeout_ms = 30000; // per-tool-call timeout
 
-    // from_file/from_json throw on I/O or parse errors; a missing "mcpServers" yields an empty list, and entries without a "command" are skipped
-    static std::vector<server_mcp_server_config> parse_from_file(const std::string & path);
+    // throw on parse errors; missing "mcpServers" yields an empty list; entries without a "command" are skipped
     static std::vector<server_mcp_server_config> parse_from_json(const std::string & json_str);
     static std::vector<server_mcp_server_config> parse_cursor_format(const json & j);
 };
@@ -44,8 +43,8 @@ struct server_mcp_tool_def {
 //   caller --send_rpc--> to_server   --[writer]--> framing --> server
 //   caller <--send_rpc-- from_server <--[reader]-- framing <-- server
 //
-// Each queue item is one complete serialized JSON message
-// A subclass owns the byte I/O and framing (stdio: NDJSON); the base owns json (parse/dump) and the JSON-RPC session (handshake, id correlation).
+// each queue item is one complete serialized JSON message.
+// subclass owns byte I/O and framing; base owns JSON and the JSON-RPC session (handshake, id correlation).
 //
 
 struct server_mcp_transport {
@@ -70,7 +69,7 @@ struct server_mcp_transport {
                    const std::function<bool()> & should_stop);
 
 protected:
-    // per-transport, not shared: send_rpc() holds it across the wait for a reply, so a shared lock would stall every server behind one slow call all members below are touched only under it
+    // per-transport: send_rpc() holds it across the reply wait, so sharing it would stall every server behind one slow call. guards all members below.
     std::mutex rpc_mutex;
     uint64_t next_id = 1; // reset to 1 per (re)spawn
     bool initialized = false;
@@ -79,11 +78,11 @@ struct server_mcp_transport {
 
     // both assume rpc_mutex is already held by the public caller
     bool ensure_init(const std::function<bool()> & should_stop); // initialize handshake, once
-    json send_rpc(const json & request, const std::function<bool()> & should_stop); // returns the reply, or an {"error": ...} object
+    json send_rpc(const json & request, const std::function<bool()> & should_stop); // returns the reply or an {"error": ...}
 };
 
 //
-// server_mcp_stdio: child process, NDJSON JSON-RPC over stdio (stderr inherited)
+// server_mcp_stdio: child process, NDJSON JSON-RPC over stdio (stderr drained to the debug log)
 //
 
 struct server_mcp_stdio : server_mcp_transport {
@@ -120,32 +119,40 @@ struct server_mcp_stdio : server_mcp_transport {
 
 //
 // server_mcp
-// manager lives inside main_server(); declare it before the HTTP context so it outlives every /tools handler.
+// declare before the HTTP context so it outlives every /tools handler.
 //
 
 class server_mcp {
 public:
-    explicit server_mcp(std::vector<server_mcp_server_config> configs);
+    server_mcp() = default;
     ~server_mcp();
 
-    // spawn each server once, list its tools, shut it down. failures are logged, not fatal.
-    void start();
+    // parse the MCP config from params (file and/or inline JSON),
+    // then spawn each server once,  list its tools, and shut it down
+    // throws on config parse errors; spawn failures are logged.
+    void start(const common_params & params);
+
+    // true until start() has parsed at least one server from the config
+    bool empty() const { return configs.empty(); }
 
     std::vector<server_mcp_tool_def> list_tools() const;
 
-    // lazily (re)spawns the transport. returns the MCP result or an {"error": ...} object. should_stop is OR-ed with the manager's cancel flag.
+    // lazily (re)spawns the transport. returns the MCP result or an {"error": ...}. should_stop is OR-ed with the manager's cancel flag.
     json call_tool(const std::string & server_name,
                    const std::string & tool_name,
                    const json & arguments,
                    const std::function<bool()> & should_stop = nullptr);
 
     // flip the cancel flag so in-flight calls return; blocking teardown is in the destructor. call before the HTTP server drains.
+    // note: multiple calls are idempotent
     void shutdown();
 
 private:
     std::vector<server_mcp_server_config> configs;
 
     mutable std::mutex mutex; // guards transports, dead_servers, registry
+
+    // shared_ptr: call_tool() hands a transport to the caller and drops the lock for the blocking RPC, so a concurrent evict/respawn must not destroy it mid-call
     std::map<std::string, std::shared_ptr<server_mcp_transport>> transports;
     std::map<std::string, std::chrono::steady_clock::time_point> dead_servers; // spawn-failure cooldown
     std::vector<server_mcp_tool_def> registry;
diff --git a/tools/server/server-tools.cpp b/tools/server/server-tools.cpp
index 9eb57abaea15..f5de1735fd11 100644
--- a/tools/server/server-tools.cpp
+++ b/tools/server/server-tools.cpp
@@ -9,10 +9,10 @@
 #include <chrono>
 #include <atomic>
 #include <cstring>
-#include <climits>
 #include <algorithm>
 #include <unordered_set>
 #include <functional>
+#include <memory>
 
 namespace fs = std::filesystem;
 
@@ -24,7 +24,7 @@ json server_tool::to_json() const {
     return {
         {"display_name", display_name},
         {"tool", name},
-        {"type", "builtin"},
+        {"type", type()},
         {"permissions", json{
             {"write", permission_write}
         }},
@@ -1102,6 +1102,54 @@ struct server_tools_res : server_http_res {
     }
 };
 
+//
+// server_mcp_tool: exposes one tool from a running MCP server as a server_tool.
+//
+struct server_mcp_tool : server_tool {
+    std::string server_name;
+    std::string tool_name;
+    server_mcp_tool_def def;
+    server_mcp & mcp_mgr;
+
+    server_mcp_tool(server_mcp_tool_def d, server_mcp & mgr)
+        : server_name(d.server_name)
+        , tool_name(d.name)
+        , def(std::move(d))
+        , mcp_mgr(mgr)
+    {
+        name = server_name + "_" + tool_name;
+        display_name = name;
+        permission_write = false;
+        support_stream = false;
+    }
+
+    std::string type() const override { return "mcp"; }
+
+    json get_definition() const override {
+        json schema = def.input_schema;
+        if (schema.is_null() || !schema.is_object()) {
+            schema = json::object();
+        }
+        return {
+            {"type", "function"},
+            {"function", {
+                {"name", name},
+                {"description", def.description},
+                {"parameters", schema},
+            }},
+        };
+    }
+
+    json invoke(json params, server_tool::stream * st) const override {
+        // pass the caller's liveness through so a disconnect cancels the in-flight RPC
+        std::function<bool()> should_stop = nullptr;
+        if (st) {
+            should_stop = [st]() { return !st->alive(); };
+        }
+        return mcp_mgr.call_tool(server_name, tool_name, params, should_stop);
+    }
+};
+
 static server_tool & find_tool(std::vector<std::unique_ptr<server_tool>> & tools, const std::string & name, bool require_stream) {
     for (auto & t : tools) {
         if (t->name == name) {
@@ -1130,7 +1178,8 @@ static std::vector<std::unique_ptr<server_tool>> build_tools() {
     return tools;
 }
 
-void server_tools::setup(const std::vector<std::string> & enabled_tools) {
+void server_tools::setup(const std::vector<std::string> & enabled_tools,
+                         server_mcp & mcp_mgr) {
     if (!enabled_tools.empty()) {
         std::unordered_set<std::string> enabled_set(enabled_tools.begin(), enabled_tools.end());
         auto all_tools = build_tools();
@@ -1161,6 +1210,29 @@ void server_tools::setup(const std::vector<std::string> & enabled_tools) {
         }
     }
 
+    // append MCP tools, skipping any that collide with a built-in or another MCP tool of the same "<server>_<tool>" name
+    if (!mcp_mgr.empty()) {
+        std::unordered_set<std::string> seen_names;
+        for (auto & t : tools) {
+            seen_names.insert(t->name);
+        }
+        size_t n_added = 0;
+        for (const auto & def : mcp_mgr.list_tools()) {
+            std::string mcp_name = def.server_name + "_" + def.name;
+            if (seen_names.count(mcp_name)) {
+                SRV_WRN("MCP tool \"%s\" from server \"%s\" collides with an existing tool, skipping\n",
+                    mcp_name.c_str(), def.server_name.c_str());
+                continue;
+            }
+            seen_names.insert(mcp_name);
+            tools.push_back(std::make_unique<server_mcp_tool>(def, mcp_mgr));
+            n_added++;
+        }
+        if (n_added > 0) {
+            SRV_INF("Added %zu MCP tools\n", n_added);
+        }
+    }
+
     handle_get = [this](const server_http_req &) -> server_http_res_ptr {
         auto res = std::make_unique<server_http_res>();
         try {
diff --git a/tools/server/server-tools.h b/tools/server/server-tools.h
index 6f6528f484f8..601399ee9392 100644
--- a/tools/server/server-tools.h
+++ b/tools/server/server-tools.h
@@ -3,9 +3,11 @@
 #include "server-common.h"
 #include "server-http.h"
 #include "server-queue.h"
+#include "server-mcp.h"
 
 #include <atomic>
 #include <functional>
+#include <memory>
 
 struct server_tool {
     std::string name;
@@ -15,6 +17,7 @@ struct server_tool {
 
     virtual ~server_tool() = default;
     virtual json get_definition() const = 0;
+    virtual std::string type() const { return "builtin"; }
 
     struct stream {
         server_response & qr;
@@ -34,7 +37,8 @@ struct server_tools {
     server_response queue_res;
     std::atomic<int> res_id{0};
 
-    void setup(const std::vector<std::string> & enabled_tools);
+    void setup(const std::vector<std::string> & enabled_tools,
+               server_mcp & mcp_mgr);
 
     server_http_context::handler_t handle_get;
     server_http_context::handler_t handle_post;
diff --git a/tools/server/server.cpp b/tools/server/server.cpp
index 20effbb14851..b6fef99e8747 100644
--- a/tools/server/server.cpp
+++ b/tools/server/server.cpp
@@ -88,6 +88,11 @@ static server_http_context::handler_t ex_wrapper(server_http_context::handler_t
 int llama_server(int argc, char ** argv) {
     std::setlocale(LC_NUMERIC, "C");
 
+#ifndef _WIN32
+    // Ignore SIGPIPE so the server does not crash if an MCP child exits while we are writing to its stdin
+    signal(SIGPIPE, SIG_IGN);
+#endif
+
     // own arguments required by this example
     common_params params;
 
@@ -157,6 +162,9 @@ int llama_server(common_params & params, int argc, char ** argv) {
         params.model_alias.insert(model_name);
     }
 
+    // note: this is guaranteed to out-live ctx_http and tools
+    server_mcp mcp_mgr;
+
     // struct that contains llama context and inference
     server_context ctx_server;
 
@@ -326,17 +334,28 @@ int llama_server(common_params & params, int argc, char ** argv) {
         ctx_http.post("/cors-proxy",      ex_wrapper(res_403));
     }
 
-    // EXPERIMENTAL built-in tools
-    if (!params.server_tools.empty()) {
+    try {
+        mcp_mgr.start(params);
+    } catch (const std::exception & e) {
+        SRV_ERR("MCP starting failed: %s\n", e.what());
+        return 1;
+    }
+
+    if (!params.server_tools.empty() || !mcp_mgr.empty()) {
         try {
-            tools.setup(params.server_tools);
+            tools.setup(params.server_tools, mcp_mgr);
         } catch (const std::exception & e) {
             SRV_ERR("tools setup failed: %s\n", e.what());
             return 1;
         }
         ctx_http.get ("/tools",           ex_wrapper(tools.handle_get));
         ctx_http.post("/tools",           ex_wrapper(tools.handle_post));
-        warn_names.push_back("built-in tools (experimental)");
+        if (!params.server_tools.empty()) {
+            warn_names.push_back("built-in tools (experimental)");
+        }
+        if (!mcp_mgr.empty()) {
+            warn_names.push_back("MCP servers (experimental)");
+        }
     } else {
         ctx_http.get ("/tools",           ex_wrapper(res_403));
         ctx_http.post("/tools",           ex_wrapper(res_403));
@@ -378,7 +397,7 @@ int llama_server(common_params & params, int argc, char ** argv) {
     if (is_router_server) {
         SRV_INF("%s", "starting server in router mode. models will be automatically loaded on-demand\n");
 
-        clean_up = [&models_routes]() {
+        clean_up = [&models_routes, &mcp_mgr]() {
             SRV_INF("%s: cleaning up before exit...\n", __func__);
             // stop the session GC first, it finalizes live sessions and wakes pending readers
             server_stream_session_manager_stop();
@@ -386,6 +405,7 @@ int llama_server(common_params & params, int argc, char ** argv) {
                 models_routes->stopping.store(true); // maybe redundant, but just to be safe
                 models_routes->models.unload_all();
             }
+            mcp_mgr.shutdown();
             llama_backend_free();
         };
 
@@ -401,17 +421,19 @@ int llama_server(common_params & params, int argc, char ** argv) {
                 // important to disconnect any SSE clients
                 models_routes->stopping.store(true);
             }
+            mcp_mgr.shutdown();
             ctx_http.stop();
         };
 
     } else {
         // setup clean up function, to be called before exit
-        clean_up = [&ctx_http, &ctx_server]() {
+        clean_up = [&ctx_http, &ctx_server, &mcp_mgr]() {
             SRV_INF("%s: cleaning up before exit...\n", __func__);
             // stop the session GC first, it finalizes live sessions and wakes pending readers
             server_stream_session_manager_stop();
             ctx_http.stop();
             ctx_server.terminate();
+            mcp_mgr.shutdown();
             llama_backend_free();
         };
 
@@ -444,6 +466,7 @@ int llama_server(common_params & params, int argc, char ** argv) {
         SRV_INF("%s", "model loaded\n");
 
         shutdown_handler = [&](int) {
+            mcp_mgr.shutdown();
             // this will unblock start_loop()
             ctx_server.terminate();
         };
diff --git a/tools/server/tests/fixtures/mcp_burst_server.py b/tools/server/tests/fixtures/mcp_burst_server.py
new file mode 100644
index 000000000000..fd66b6973713
--- /dev/null
+++ b/tools/server/tests/fixtures/mcp_burst_server.py
@@ -0,0 +1,124 @@
+#!/usr/bin/env python3
+"""
+Minimal MCP server that writes notification + response in a single write() with no flush.
+This reproduces the buffering bug where read_message() can strand the response.
+"""
+import json
+import sys
+import os
+
+TOOLS = [
+    {
+        "name": "echo",
+        "description": "Echo back the input message",
+        "inputSchema": {
+            "type": "object",
+            "properties": {
+                "message": {"type": "string"}
+            },
+            "required": ["message"]
+        }
+    }
+]
+
+def handle_initialize(params, req_id):
+    return {
+        "jsonrpc": "2.0",
+        "id": req_id,
+        "result": {
+            "protocolVersion": "2024-11-05",
+            "capabilities": {"tools": {}},
+            "serverInfo": {"name": "burst-test", "version": "1.0"}
+        }
+    }
+
+def handle_tools_list(params, req_id):
+    return {
+        "jsonrpc": "2.0",
+        "id": req_id,
+        "result": {"tools": TOOLS}
+    }
+
+def handle_tools_call(params, req_id):
+    tool_name = params.get("name")
+    arguments = params.get("arguments", {})
+
+    if tool_name == "echo":
+        message = arguments.get("message", "")
+        notif = {
+            "jsonrpc": "2.0",
+            "method": "notifications/progress",
+            "params": {"progress": 50, "total": 100}
+        }
+        response = {
+            "jsonrpc": "2.0",
+            "id": req_id,
+            "result": {
+                "content": [{"type": "text", "text": f"echo: {message}"}]
+            }
+        }
+        # Single os.write() call: both lines land in one pipe packet atomically.
+        # This is the key difference from mcp_malformed_server.py which flushes between writes.
+        data = (json.dumps(notif) + "\n" + json.dumps(response) + "\n").encode("utf-8")
+        os.write(sys.stdout.fileno(), data)
+        return None  # already written
+    else:
+        response = {
+            "jsonrpc": "2.0",
+            "id": req_id,
+            "error": {"code": -32601, "message": f"Unknown tool: {tool_name}"}
+        }
+        return response
+
+HANDLERS = {
+    "initialize": handle_initialize,
+    "tools/list": handle_tools_list,
+    "tools/call": handle_tools_call,
+}
+
+# notifications have no id and don't expect a response
+NOTIFICATION_HANDLERS = {
+    "notifications/initialized": lambda params, req_id: None,
+}
+
+def main():
+    # Use line-buffered text mode for regular responses, but the burst write
+    # uses os.write() directly to guarantee a single kernel write().
+    sys.stdout = os.fdopen(sys.stdout.fileno(), "w", buffering=1)
+    sys.stderr = os.fdopen(sys.stderr.fileno(), "w", buffering=1)
+
+    for line in sys.stdin:
+        line = line.strip()
+        if not line:
+            continue
+        try:
+            request = json.loads(line)
+        except json.JSONDecodeError:
+            continue
+
+        method = request.get("method")
+        req_id = request.get("id")
+        params = request.get("params", {})
+
+        # Check notification handlers first (no response expected)
+        if not req_id and method in NOTIFICATION_HANDLERS:
+            NOTIFICATION_HANDLERS[method](params, req_id)
+            continue
+
+        handler = HANDLERS.get(method)
+        if handler:
+            response = handler(params, req_id)
+            if response is not None:
+                sys.stdout.write(json.dumps(response) + "\n")
+                sys.stdout.flush()
+        else:
+            response = {
+                "jsonrpc": "2.0",
+                "id": req_id,
+                "error": {"code": -32601, "message": f"Method not found: {method}"}
+            }
+            sys.stdout.write(json.dumps(response) + "\n")
+            sys.stdout.flush()
+
+if __name__ == "__main__":
+    main()
diff --git a/tools/server/tests/fixtures/mcp_crash_server.py b/tools/server/tests/fixtures/mcp_crash_server.py
new file mode 100644
index 000000000000..7f389c6bc0a3
--- /dev/null
+++ b/tools/server/tests/fixtures/mcp_crash_server.py
@@ -0,0 +1,114 @@
+#!/usr/bin/env python3
+"""
+MCP server that crashes after receiving a specific tool call.
+"""
+import json
+import sys
+import os
+
+def handle_initialize(params, req_id):
+    return {
+        "jsonrpc": "2.0",
+        "id": req_id,
+        "result": {
+            "protocolVersion": "2024-11-05",
+            "capabilities": {"tools": {}},
+            "serverInfo": {"name": "crash-test", "version": "1.0"}
+        }
+    }
+
+def handle_tools_list(params, req_id):
+    return {
+        "jsonrpc": "2.0",
+        "id": req_id,
+        "result": {
+            "tools": [
+                {
+                    "name": "echo",
+                    "description": "Echo back the input message",
+                    "inputSchema": {
+                        "type": "object",
+                        "properties": {
+                            "message": {"type": "string"}
+                        }
+                    }
+                },
+                {
+                    "name": "crash",
+                    "description": "Crash the server",
+                    "inputSchema": {
+                        "type": "object",
+                        "properties": {}
+                    }
+                }
+            ]
+        }
+    }
+
+def handle_tools_call(params, req_id):
+    tool_name = params.get("name")
+    arguments = params.get("arguments", {})
+
+    if tool_name == "echo":
+        message = arguments.get("message", "")
+        return {
+            "jsonrpc": "2.0",
+            "id": req_id,
+            "result": {
+                "content": [{"type": "text", "text": f"echo: {message}"}]
+            }
+        }
+    elif tool_name == "crash":
+        # Send a partial response then exit
+        sys.stdout.write(json.dumps({"jsonrpc": "2.0", "id": req_id, "result": {"content": [{"type": "text", "text": "crashing..."}]}}) + "\n")
+        sys.stdout.flush()
+        os._exit(1)
+    else:
+        return {
+            "jsonrpc": "2.0",
+            "id": req_id,
+            "error": {"code": -32601, "message": f"Unknown tool: {tool_name}"}
+        }
+
+HANDLERS = {
+    "initialize": handle_initialize,
+    "tools/list": handle_tools_list,
+    "tools/call": handle_tools_call,
+}
+
+def main():
+    sys.stdout = os.fdopen(sys.stdout.fileno(), "w", buffering=1)
+    sys.stderr = os.fdopen(sys.stderr.fileno(), "w", buffering=1)
+
+    for line in sys.stdin:
+        line = line.strip()
+        if not line:
+            continue
+        try:
+            request = json.loads(line)
+        except json.JSONDecodeError:
+            continue
+
+        method = request.get("method")
+        req_id = request.get("id")
+        params = request.get("params", {})
+
+        # JSON-RPC 2.0: a message without an id is a notification and must not receive a response
+        if req_id is None:
+            continue
+
+        handler = HANDLERS.get(method)
+        if handler:
+            response = handler(params, req_id)
+        else:
+            response = {
+                "jsonrpc": "2.0",
+                "id": req_id,
+                "error": {"code": -32601, "message": f"Method not found: {method}"}
+            }
+
+        sys.stdout.write(json.dumps(response) + "\n")
+        sys.stdout.flush()
+
+if __name__ == "__main__":
+    main()
diff --git a/tools/server/tests/fixtures/mcp_echo_server.py b/tools/server/tests/fixtures/mcp_echo_server.py
new file mode 100755
index 000000000000..7acfb358881a
--- /dev/null
+++ b/tools/server/tests/fixtures/mcp_echo_server.py
@@ -0,0 +1,164 @@
+#!/usr/bin/env python3
+"""
+Minimal MCP server for testing.
+Implements JSON-RPC 2.0 over stdio (line-delimited JSON).
+"""
+import json
+import sys
+import os
+
+# Ensure we use python3 from the current environment
+if sys.platform == "win32":
+    # On Windows, we need to use the same python interpreter
+    pass
+
+TOOLS = [
+    {
+        "name": "echo",
+        "description": "Echo back the input message",
+        "inputSchema": {
+            "type": "object",
+            "properties": {
+                "message": {"type": "string", "description": "Message to echo"}
+            },
+            "required": ["message"]
+        }
+    },
+    {
+        "name": "add",
+        "description": "Add two numbers",
+        "inputSchema": {
+            "type": "object",
+            "properties": {
+                "a": {"type": "number"},
+                "b": {"type": "number"}
+            },
+            "required": ["a", "b"]
+        }
+    },
+    {
+        "name": "fail_once",
+        "description": "Fails on first call, succeeds on subsequent calls",
+        "inputSchema": {
+            "type": "object",
+            "properties": {}
+        }
+    }
+]
+
+_state = {"fail_once_called": False}
+
+def handle_initialize(params, req_id):
+    return {
+        "jsonrpc": "2.0",
+        "id": req_id,
+        "result": {
+            "protocolVersion": "2024-11-05",
+            "capabilities": {"tools": {}},
+            "serverInfo": {"name": "echo-test", "version": "1.0"}
+        }
+    }
+
+def handle_tools_list(params, req_id):
+    return {
+        "jsonrpc": "2.0",
+        "id": req_id,
+        "result": {"tools": TOOLS}
+    }
+
+def handle_tools_call(params, req_id):
+    tool_name = params.get("name")
+    arguments = params.get("arguments", {})
+
+    if tool_name == "echo":
+        message = arguments.get("message", "")
+        return {
+            "jsonrpc": "2.0",
+            "id": req_id,
+            "result": {
+                "content": [{"type": "text", "text": f"echo: {message}"}]
+            }
+        }
+    elif tool_name == "add":
+        a = arguments.get("a", 0)
+        b = arguments.get("b", 0)
+        return {
+            "jsonrpc": "2.0",
+            "id": req_id,
+            "result": {
+                "content": [{"type": "text", "text": str(a + b)}]
+            }
+        }
+    elif tool_name == "fail_once":
+        if not _state["fail_once_called"]:
+            _state["fail_once_called"] = True
+            return {
+                "jsonrpc": "2.0",
+                "id": req_id,
+                "error": {"code": -32000, "message": "transient error"}
+            }
+        return {
+            "jsonrpc": "2.0",
+            "id": req_id,
+            "result": {
+                "content": [{"type": "text", "text": "ok"}]
+            }
+        }
+    else:
+        return {
+            "jsonrpc": "2.0",
+            "id": req_id,
+            "error": {"code": -32602, "message": f"Unknown tool: {tool_name}"}
+        }
+
+def handle_ping(params, req_id):
+    return {
+        "jsonrpc": "2.0",
+        "id": req_id,
+        "result": {}
+    }
+
+HANDLERS = {
+    "initialize": handle_initialize,
+    "tools/list": handle_tools_list,
+    "tools/call": handle_tools_call,
+    "ping": handle_ping,
+}
+
+def main():
+    # Use unbuffered output
+    sys.stdout = os.fdopen(sys.stdout.fileno(), "w", buffering=1)
+    sys.stderr = os.fdopen(sys.stderr.fileno(), "w", buffering=1)
+
+    for line in sys.stdin:
+        line = line.strip()
+        if not line:
+            continue
+        try:
+            request = json.loads(line)
+        except json.JSONDecodeError:
+            continue
+
+        method = request.get("method")
+        req_id = request.get("id")
+        params = request.get("params", {})
+
+        # JSON-RPC 2.0: a message without an id is a notification and must not receive a response
+        if req_id is None:
+            continue
+
+        handler = HANDLERS.get(method)
+        if handler:
+            response = handler(params, req_id)
+        else:
+            response = {
+                "jsonrpc": "2.0",
+                "id": req_id,
+                "error": {"code": -32601, "message": f"Method not found: {method}"}
+            }
+
+        sys.stdout.write(json.dumps(response) + "\n")
+        sys.stdout.flush()
+
+if __name__ == "__main__":
+    main()
diff --git a/tools/server/tests/fixtures/mcp_grandchild_server.py b/tools/server/tests/fixtures/mcp_grandchild_server.py
new file mode 100644
index 000000000000..9defa904d61f
--- /dev/null
+++ b/tools/server/tests/fixtures/mcp_grandchild_server.py
@@ -0,0 +1,100 @@
+#!/usr/bin/env python3
+"""
+MCP server (NDJSON JSON-RPC over stdio) that spawns a long-lived grandchild which inherits
+this process's stdin/stdout/stderr and keeps them open.
+
+This reproduces the reader-teardown deadlock: killing the direct MCP child (SIGKILL, which is
+all subprocess_terminate() does) does NOT close the stdout/stderr pipe write ends, because the
+grandchild still holds them. A server that reads those pipes with a blocking read would then
+wait forever for an EOF that never arrives, hanging teardown (both warmup shutdown at startup
+and process shutdown). The polled, running-aware reader must exit regardless.
+"""
+import json
+import os
+import subprocess
+import sys
+
+# Spawn a grandchild that inherits our std handles (fds 0/1/2 = the MCP pipes) and lives well
+# past any teardown in the tests. We do NOT redirect its stdio, so it keeps the pipe write ends
+# open even after this process is killed.
+subprocess.Popen([sys.executable, "-c", "import time; time.sleep(30)"])
+
+TOOLS = [
+    {
+        "name": "echo",
+        "description": "Echo back the input message",
+        "inputSchema": {
+            "type": "object",
+            "properties": {"message": {"type": "string", "description": "Message to echo"}},
+            "required": ["message"],
+        },
+    }
+]
+
+
+def handle_initialize(params, req_id):
+    return {
+        "jsonrpc": "2.0",
+        "id": req_id,
+        "result": {
+            "protocolVersion": "2024-11-05",
+            "capabilities": {"tools": {}},
+            "serverInfo": {"name": "grandchild-test", "version": "1.0"},
+        },
+    }
+
+
+def handle_tools_list(params, req_id):
+    return {"jsonrpc": "2.0", "id": req_id, "result": {"tools": TOOLS}}
+
+
+def handle_tools_call(params, req_id):
+    if params.get("name") == "echo":
+        message = params.get("arguments", {}).get("message", "")
+        return {
+            "jsonrpc": "2.0",
+            "id": req_id,
+            "result": {"content": [{"type": "text", "text": f"echo: {message}"}]},
+        }
+    return {"jsonrpc": "2.0", "id": req_id, "error": {"code": -32601, "message": "Unknown tool"}}
+
+
+HANDLERS = {
+    "initialize": handle_initialize,
+    "tools/list": handle_tools_list,
+    "tools/call": handle_tools_call,
+}
+
+
+def main():
+    sys.stdout = os.fdopen(sys.stdout.fileno(), "w", buffering=1)
+    sys.stderr = os.fdopen(sys.stderr.fileno(), "w", buffering=1)
+
+    for line in sys.stdin:
+        line = line.strip()
+        if not line:
+            continue
+        try:
+            request = json.loads(line)
+        except json.JSONDecodeError:
+            continue
+
+        method = request.get("method")
+        req_id = request.get("id")
+        params = request.get("params", {})
+
+        if req_id is None:
+            continue  # notification, no response
+
+        handler = HANDLERS.get(method)
+        if handler:
+            response = handler(params, req_id)
+        else:
+            response = {"jsonrpc": "2.0", "id": req_id, "error": {"code": -32601, "message": f"Method not found: {method}"}}
+
+        sys.stdout.write(json.dumps(response) + "\n")
+        sys.stdout.flush()
+
+
+if __name__ == "__main__":
+    main()
diff --git a/tools/server/tests/fixtures/mcp_malformed_server.py b/tools/server/tests/fixtures/mcp_malformed_server.py
new file mode 100644
index 000000000000..365595867b86
--- /dev/null
+++ b/tools/server/tests/fixtures/mcp_malformed_server.py
@@ -0,0 +1,109 @@
+#!/usr/bin/env python3
+"""
+MCP server that sends malformed responses and notifications during requests.
+"""
+import json
+import sys
+import os
+
+def handle_initialize(params, req_id):
+    return {
+        "jsonrpc": "2.0",
+        "id": req_id,
+        "result": {
+            "protocolVersion": "2024-11-05",
+            "capabilities": {"tools": {}},
+            "serverInfo": {"name": "malformed-test", "version": "1.0"}
+        }
+    }
+
+def handle_tools_list(params, req_id):
+    return {
+        "jsonrpc": "2.0",
+        "id": req_id,
+        "result": {
+            "tools": [
+                {
+                    "name": "echo",
+                    "description": "Echo back the input message",
+                    "inputSchema": {
+                        "type": "object",
+                        "properties": {
+                            "message": {"type": "string"}
+                        }
+                    }
+                }
+            ]
+        }
+    }
+
+def handle_tools_call(params, req_id):
+    tool_name = params.get("name")
+    arguments = params.get("arguments", {})
+
+    if tool_name == "echo":
+        message = arguments.get("message", "")
+        # Send a notification first (no id field)
+        notif = {
+            "jsonrpc": "2.0",
+            "method": "notifications/progress",
+            "params": {"progress": 50, "total": 100}
+        }
+        sys.stdout.write(json.dumps(notif) + "\n")
+        sys.stdout.flush()
+        # Then send the actual response
+        return {
+            "jsonrpc": "2.0",
+            "id": req_id,
+            "result": {
+                "content": [{"type": "text", "text": f"echo: {message}"}]
+            }
+        }
+    else:
+        return {
+            "jsonrpc": "2.0",
+            "id": req_id,
+            "error": {"code": -32601, "message": f"Unknown tool: {tool_name}"}
+        }
+
+HANDLERS = {
+    "initialize": handle_initialize,
+    "tools/list": handle_tools_list,
+    "tools/call": handle_tools_call,
+}
+
+def main():
+    sys.stdout = os.fdopen(sys.stdout.fileno(), "w", buffering=1)
+    sys.stderr = os.fdopen(sys.stderr.fileno(), "w", buffering=1)
+
+    for line in sys.stdin:
+        line = line.strip()
+        if not line:
+            continue
+        try:
+            request = json.loads(line)
+        except json.JSONDecodeError:
+            # Send malformed JSON response
+            sys.stdout.write("THIS IS NOT JSON\n")
+            sys.stdout.flush()
+            continue
+
+        method = request.get("method")
+        req_id = request.get("id")
+        params = request.get("params", {})
+
+        handler = HANDLERS.get(method)
+        if handler:
+            response = handler(params, req_id)
+        else:
+            response = {
+                "jsonrpc": "2.0",
+                "id": req_id,
+                "error": {"code": -32601, "message": f"Method not found: {method}"}
+            }
+
+        sys.stdout.write(json.dumps(response) + "\n")
+        sys.stdout.flush()
+
+if __name__ == "__main__":
+    main()
diff --git a/tools/server/tests/fixtures/mcp_slow_server.py b/tools/server/tests/fixtures/mcp_slow_server.py
new file mode 100644
index 000000000000..6b7f7184e527
--- /dev/null
+++ b/tools/server/tests/fixtures/mcp_slow_server.py
@@ -0,0 +1,132 @@
+#!/usr/bin/env python3
+"""
+MCP server that sleeps before responding, for timeout testing.
+"""
+import json
+import sys
+import os
+import time
+import argparse
+
+TOOLS = [
+    {
+        "name": "sleep",
+        "description": "Sleep for a given number of seconds",
+        "inputSchema": {
+            "type": "object",
+            "properties": {
+                "seconds": {"type": "number", "description": "Seconds to sleep"}
+            },
+            "required": ["seconds"]
+        }
+    }
+]
+
+def handle_initialize(params, req_id):
+    return {
+        "jsonrpc": "2.0",
+        "id": req_id,
+        "result": {
+            "protocolVersion": "2024-11-05",
+            "capabilities": {"tools": {}},
+            "serverInfo": {"name": "slow-test", "version": "1.0"}
+        }
+    }
+
+def handle_tools_list(params, req_id):
+    return {
+        "jsonrpc": "2.0",
+        "id": req_id,
+        "result": {"tools": TOOLS}
+    }
+
+def handle_tools_call(params, req_id):
+    tool_name = params.get("name")
+    arguments = params.get("arguments", {})
+
+    if tool_name == "sleep":
+        seconds = arguments.get("seconds", 1)
+        time.sleep(seconds)
+        return {
+            "jsonrpc": "2.0",
+            "id": req_id,
+            "result": {
+                "content": [{"type": "text", "text": f"slept {seconds}s"}]
+            }
+        }
+    else:
+        return {
+            "jsonrpc": "2.0",
+            "id": req_id,
+            "error": {"code": -32601, "message": f"Unknown tool: {tool_name}"}
+        }
+
+HANDLERS = {
+    "initialize": handle_initialize,
+    "tools/list": handle_tools_list,
+    "tools/call": handle_tools_call,
+}
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--delay", type=float, default=5.0, help="Delay in seconds for sleep tool")
+    args = parser.parse_args()
+
+    # Override the sleep duration
+    global handle_tools_call
+    def handle_tools_call(params, req_id):
+        tool_name = params.get("name")
+        arguments = params.get("arguments", {})
+
+        if tool_name == "sleep":
+            seconds = arguments.get("seconds", args.delay)
+            time.sleep(seconds)
+            return {
+                "jsonrpc": "2.0",
+                "id": req_id,
+                "result": {
+                    "content": [{"type": "text", "text": f"slept {seconds}s"}]
+                }
+            }
+        else:
+            return {
+                "jsonrpc": "2.0",
+                "id": req_id,
+                "error": {"code": -32601, "message": f"Unknown tool: {tool_name}"}
+            }
+
+    sys.stdout = os.fdopen(sys.stdout.fileno(), "w", buffering=1)
+    sys.stderr = os.fdopen(sys.stderr.fileno(), "w", buffering=1)
+
+    for line in sys.stdin:
+        line = line.strip()
+        if not line:
+            continue
+        try:
+            request = json.loads(line)
+        except json.JSONDecodeError:
+            continue
+
+        method = request.get("method")
+        req_id = request.get("id")
+        params = request.get("params", {})
+
+        # JSON-RPC 2.0: a message without an id is a notification and must not receive a response
+        if req_id is None:
+            continue
+
+        handler = HANDLERS.get(method)
+        if handler:
+            response = handler(params, req_id)
+        else:
+            response = {
+                "jsonrpc": "2.0",
+                "id": req_id,
+                "error": {"code": -32601, "message": f"Method not found: {method}"}
+            }
+
+        sys.stdout.write(json.dumps(response) + "\n")
+        sys.stdout.flush()
+
+if __name__ == "__main__":
+    main()
diff --git a/tools/server/tests/unit/test_mcp_servers.py b/tools/server/tests/unit/test_mcp_servers.py
new file mode 100644
index 000000000000..de4aa36bcf47
--- /dev/null
+++ b/tools/server/tests/unit/test_mcp_servers.py
@@ -0,0 +1,718 @@
+#!/usr/bin/env python3
+"""
+Tests for MCP server integration via the /tools endpoint.
+
+Invariants verified:
+1. MCP tools appear in /tools listing when configured
+2. MCP tools use <server>:<tool> naming
+3. MCP tools can be invoked and return correct results
+4. Misconfigured MCP servers do not crash the server
+5. Multiple MCP servers can be configured simultaneously
+6. Warmup populates the tool list at startup
+"""
+import json
+import os
+import sys
+import tempfile
+import time
+
+import pytest
+
+from utils import *
+
+# Path to the test MCP server fixture
+FIXTURES_DIR = os.path.join(os.path.dirname(os.path.abspath(__file__)), "..", "fixtures")
+MCP_ECHO_SERVER = os.path.join(FIXTURES_DIR, "mcp_echo_server.py")
+
+server: ServerProcess
+
+
+def _mcp_config_json(servers: dict) -> str:
+    """Create a JSON config string for --mcp-servers-json."""
+    return json.dumps({"mcpServers": servers})
+
+
+def _start_server_with_mcp(mcp_json: str, **kwargs) -> ServerProcess:
+    """Helper to start a router server with MCP config."""
+    srv = ServerPreset.router()
+    srv.server_tools = "all"
+    srv.no_ui = True
+    srv.server_port = 8085  # avoid conflict with load_all() which uses 8080
+    srv.mcp_servers_json = mcp_json
+    for k, v in kwargs.items():
+        setattr(srv, k, v)
+    srv.start()
+    return srv
+
+
+def test_mcp_tools_listed_in_tools_endpoint():
+    """MCP tools should appear in GET /tools with server:tool naming."""
+    global server
+    mcp_json = _mcp_config_json({
+        "echo": {
+            "command": sys.executable,
+            "args": [MCP_ECHO_SERVER],
+        }
+    })
+    server = _start_server_with_mcp(mcp_json)
+
+    try:
+        res = server.make_request("GET", "/tools")
+        assert res.status_code == 200, res.body
+
+        tools = res.body
+        assert isinstance(tools, list), f"Expected list, got {type(tools)}"
+
+        # Find MCP tools - name is in "tool" field or definition.function.name
+        def get_tool_name(t):
+            return t.get("tool", "") or t.get("definition", {}).get("function", {}).get("name", "")
+
+        mcp_tools = [t for t in tools if get_tool_name(t).startswith("echo_")]
+        assert len(mcp_tools) >= 2, f"Expected at least 2 echo_ tools, got {len(mcp_tools)}: {mcp_tools}"
+
+        tool_names = {get_tool_name(t) for t in mcp_tools}
+        assert "echo_echo" in tool_names
+        assert "echo_add" in tool_names
+
+        # Verify tool structure
+        echo_tool = next(t for t in mcp_tools if get_tool_name(t) == "echo_echo")
+        assert "description" in echo_tool or "definition" in echo_tool
+    finally:
+        server.stop()
+
+
+def test_mcp_tool_invocation():
+    """MCP tools should be callable via POST /tools and return correct results."""
+    global server
+    mcp_json = _mcp_config_json({
+        "echo": {
+            "command": sys.executable,
+            "args": [MCP_ECHO_SERVER],
+        }
+    })
+    server = _start_server_with_mcp(mcp_json)
+
+    try:
+        # Call echo_echo
+        res = server.make_request("POST", "/tools", data={
+            "tool": "echo_echo",
+            "params": {"message": "hello world"}
+        })
+        assert res.status_code == 200, res.body
+        body = res.body
+        assert "error" not in body, body
+        # The result format depends on the tool implementation
+        # For MCP tools, it should contain the tool result
+        assert "plain_text_response" in body or "result" in body or "content" in body, body
+
+        # Call echo_add
+        res = server.make_request("POST", "/tools", data={
+            "tool": "echo_add",
+            "params": {"a": 3, "b": 5}
+        })
+        assert res.status_code == 200, res.body
+        body = res.body
+        assert "error" not in body, body
+    finally:
+        server.stop()
+
+
+def test_mcp_bad_command_does_not_crash():
+    """A misconfigured MCP server should not crash the llama-server."""
+    global server
+    mcp_json = _mcp_config_json({
+        "nonexistent": {
+            "command": "this_executable_does_not_exist_12345",
+            "args": [],
+        }
+    })
+    server = _start_server_with_mcp(mcp_json)
+
+    try:
+        # Server should still be healthy
+        res = server.make_request("GET", "/health")
+        assert res.status_code == 200, res.body
+
+        # Builtin tools should still work
+        res = server.make_request("GET", "/tools")
+        assert res.status_code == 200, res.body
+        tools = res.body
+        # Should have builtin tools but no MCP tools from the bad server
+        mcp_tools = [t for t in tools if t.get("name", "").startswith("nonexistent_")]
+        assert len(mcp_tools) == 0, f"Expected no nonexistent_ tools, got {mcp_tools}"
+    finally:
+        server.stop()
+
+
+def test_mcp_multiple_servers():
+    """Multiple MCP servers can be configured simultaneously."""
+    global server
+    mcp_json = _mcp_config_json({
+        "echo": {
+            "command": sys.executable,
+            "args": [MCP_ECHO_SERVER],
+        },
+        "echo2": {
+            "command": sys.executable,
+            "args": [MCP_ECHO_SERVER],
+        }
+    })
+    server = _start_server_with_mcp(mcp_json)
+
+    try:
+        res = server.make_request("GET", "/tools")
+        assert res.status_code == 200, res.body
+
+        tools = res.body
+
+        def get_tool_name(t):
+            return t.get("tool", "") or t.get("definition", {}).get("function", {}).get("name", "")
+
+        echo_tools = [t for t in tools if get_tool_name(t).startswith("echo_")]
+        echo2_tools = [t for t in tools if get_tool_name(t).startswith("echo2_")]
+
+        assert len(echo_tools) >= 2, f"Expected echo_ tools, got {echo_tools}"
+        assert len(echo2_tools) >= 2, f"Expected echo2_ tools, got {echo2_tools}"
+    finally:
+        server.stop()
+
+
+def test_mcp_tools_not_listed_when_not_configured():
+    """Without MCP config, no MCP tools should appear."""
+    global server
+    server = ServerPreset.router()
+    server.server_tools = "all"
+    server.no_ui = True
+    server.server_port = 8085
+    server.start()
+
+    try:
+        res = server.make_request("GET", "/tools")
+        assert res.status_code == 200, res.body
+
+        tools = res.body
+
+        def get_tool_name(t):
+            return t.get("tool", "") or t.get("definition", {}).get("function", {}).get("name", "")
+
+        # Should only have builtin tools, no server: prefixed tools
+        mcp_tools = [t for t in tools if ":" in get_tool_name(t)]
+        assert len(mcp_tools) == 0, f"Expected no MCP tools, got {mcp_tools}"
+    finally:
+        server.stop()
+
+
+def test_mcp_fail_once_tool_eventual_success():
+    """Test that a tool that fails once eventually succeeds (tests instance respawn)."""
+    global server
+    mcp_json = _mcp_config_json({
+        "echo": {
+            "command": sys.executable,
+            "args": [MCP_ECHO_SERVER],
+        }
+    })
+    server = _start_server_with_mcp(mcp_json)
+
+    try:
+        # First call should succeed (warmup already spawned and shut down the instance,
+        # but the first actual tool call will spawn a fresh instance)
+        res = server.make_request("POST", "/tools", data={
+            "tool": "echo_fail_once",
+            "params": {}
+        })
+        # It might fail on first call if the warmup instance was shut down
+        # and a new instance is spawned. The fail_once state is per-process,
+        # so a fresh process will fail once then succeed.
+        # Actually, warmup spawns, lists, then shuts down. So the first tool call
+        # spawns a new process which will fail once.
+        assert res.status_code in (200, 500), res.body
+    finally:
+        server.stop()
+
+
+def test_mcp_tools_via_json_config_file():
+    """Test that --mcp-servers-config (file) works as well as --mcp-servers-json."""
+    global server
+    config = {
+        "mcpServers": {
+            "echo": {
+                "command": sys.executable,
+                "args": [MCP_ECHO_SERVER],
+            }
+        }
+    }
+
+    with tempfile.NamedTemporaryFile(mode="w", suffix=".json", delete=False) as f:
+        json.dump(config, f)
+        config_path = f.name
+
+    try:
+        server = ServerPreset.router()
+        server.server_tools = "all"
+        server.no_ui = True
+        server.server_port = 8085
+        server.mcp_servers_config = config_path
+        server.start()
+
+        res = server.make_request("GET", "/tools")
+        assert res.status_code == 200, res.body
+
+        tools = res.body
+
+        def get_tool_name(t):
+            return t.get("tool", "") or t.get("definition", {}).get("function", {}).get("name", "")
+
+        mcp_tools = [t for t in tools if get_tool_name(t).startswith("echo_")]
+        assert len(mcp_tools) >= 2, f"Expected echo_ tools, got {mcp_tools}"
+    finally:
+        os.unlink(config_path)
+        server.stop()
+
+
+def test_mcp_tools_slot_independent():
+    """MCP tools should work without any slot concept; /tools is slot-independent."""
+    global server
+    mcp_json = _mcp_config_json({
+        "echo": {
+            "command": sys.executable,
+            "args": [MCP_ECHO_SERVER],
+        }
+    })
+    server = _start_server_with_mcp(mcp_json)
+
+    try:
+        # Call /tools without any slot binding - should succeed
+        res = server.make_request("POST", "/tools", data={
+            "tool": "echo_echo",
+            "params": {"message": "hello"}
+        })
+        assert res.status_code == 200, res.body
+        body = res.body
+        assert "error" not in body, body
+    finally:
+        server.stop()
+
+
+def test_mcp_concurrent_tool_calls():
+    """Concurrent POST /tools to same MCP server should all succeed."""
+    global server
+    mcp_json = _mcp_config_json({
+        "echo": {
+            "command": sys.executable,
+            "args": [MCP_ECHO_SERVER],
+        }
+    })
+    server = _start_server_with_mcp(mcp_json)
+
+    try:
+        def call_tool():
+            return server.make_request("POST", "/tools", data={
+                "tool": "echo_echo",
+                "params": {"message": "hi"}
+            })
+
+        with ThreadPoolExecutor(max_workers=10) as executor:
+            futures = [executor.submit(call_tool) for _ in range(10)]
+            results = [f.result() for f in futures]
+
+        for res in results:
+            assert res.status_code == 200, res.body
+            assert "error" not in res.body, res.body
+    finally:
+        server.stop()
+
+
+def test_mcp_tool_timeout():
+    """Tool call should timeout if MCP server is too slow."""
+    global server
+    MCP_SLOW_SERVER = os.path.join(FIXTURES_DIR, "mcp_slow_server.py")
+    mcp_json = _mcp_config_json({
+        "slow": {
+            "command": sys.executable,
+            "args": [MCP_SLOW_SERVER, "--delay", "5"],
+            "timeout_ms": 500
+        }
+    })
+    server = _start_server_with_mcp(mcp_json)
+
+    try:
+        res = server.make_request("POST", "/tools", data={
+            "tool": "slow_sleep",
+            "params": {"seconds": 5}
+        })
+        assert res.status_code == 200, res.body
+        body = res.body
+        assert "error" in body, body
+    finally:
+        server.stop()
+
+
+def test_mcp_warmup_partial_failure():
+    """Good server's tools should appear even if bad server fails warmup."""
+    global server
+    mcp_json = _mcp_config_json({
+        "good": {
+            "command": sys.executable,
+            "args": [MCP_ECHO_SERVER],
+        },
+        "bad": {
+            "command": "nonexistent",
+            "args": []
+        }
+    })
+    server = _start_server_with_mcp(mcp_json)
+
+    try:
+        res = server.make_request("GET", "/tools")
+        assert res.status_code == 200, res.body
+        tools = res.body
+
+        def get_tool_name(t):
+            return t.get("tool", "") or t.get("definition", {}).get("function", {}).get("name", "")
+
+        # good server tools should be present
+        assert any("good_" in get_tool_name(t) for t in tools), f"Expected good: tools in {tools}"
+    finally:
+        server.stop()
+
+
+def test_mcp_notification_during_request():
+    """Notification during request should not be returned as response."""
+    global server
+    MCP_MALFORMED_SERVER = os.path.join(FIXTURES_DIR, "mcp_malformed_server.py")
+    mcp_json = _mcp_config_json({
+        "notifying": {
+            "command": sys.executable,
+            "args": [MCP_MALFORMED_SERVER],
+        }
+    })
+    server = _start_server_with_mcp(mcp_json)
+
+    try:
+        res = server.make_request("POST", "/tools", data={
+            "tool": "notifying_echo",
+            "params": {"message": "hi"}
+        })
+        assert res.status_code == 200, res.body
+        body = res.body
+        assert "error" not in body, body
+    finally:
+        server.stop()
+
+
+def test_mcp_instance_respawn_after_crash():
+    """Tool call after process crash should respawn and succeed."""
+    global server
+    MCP_CRASH_SERVER = os.path.join(FIXTURES_DIR, "mcp_crash_server.py")
+    mcp_json = _mcp_config_json({
+        "crash": {
+            "command": sys.executable,
+            "args": [MCP_CRASH_SERVER],
+        }
+    })
+    server = _start_server_with_mcp(mcp_json)
+
+    try:
+        # First call succeeds
+        res1 = server.make_request("POST", "/tools", data={
+            "tool": "crash_echo",
+            "params": {"message": "hi"}
+        })
+        assert res1.status_code == 200, res1.body
+        assert "error" not in res1.body, res1.body
+
+        # Second call should also succeed (respawned instance)
+        res2 = server.make_request("POST", "/tools", data={
+            "tool": "crash_echo",
+            "params": {"message": "hi2"}
+        })
+        assert res2.status_code == 200, res2.body
+        assert "error" not in res2.body, res2.body
+    finally:
+        server.stop()
+
+
+
+
+def test_mcp_fail_once_eventual_success_verified():
+    """Verify that fail_once tool eventually succeeds after respawn."""
+    global server
+    mcp_json = _mcp_config_json({
+        "echo": {
+            "command": sys.executable,
+            "args": [MCP_ECHO_SERVER],
+        }
+    })
+    server = _start_server_with_mcp(mcp_json)
+
+    try:
+        # First call may fail (fresh process)
+        res1 = server.make_request("POST", "/tools", data={
+            "tool": "echo_fail_once",
+            "params": {}
+        })
+        # Second call should succeed
+        res2 = server.make_request("POST", "/tools", data={
+            "tool": "echo_fail_once",
+            "params": {}
+        })
+        assert res2.status_code == 200, res2.body
+        assert "error" not in res2.body, res2.body
+    finally:
+        server.stop()
+
+
+def test_mcp_config_file_errors():
+    """Invalid JSON config and missing file should cause server to fail to start."""
+    # Invalid JSON - server should fail to start
+    server = ServerPreset.router()
+    server.server_tools = "all"
+    server.no_ui = True
+    server.server_port = 8085
+    server.mcp_servers_json = "not valid json"
+    try:
+        server.start()
+        assert False, "Server should not have started with invalid MCP JSON config"
+    except RuntimeError:
+        pass  # Expected: server process dies due to bad config
+
+    # Missing file - server should fail to start
+    server = ServerPreset.router()
+    server.server_tools = "all"
+    server.no_ui = True
+    server.server_port = 8085
+    server.mcp_servers_config = "/nonexistent/path.json"
+    try:
+        server.start()
+        assert False, "Server should not have started with missing config file"
+    except RuntimeError:
+        pass  # Expected: server process dies due to missing config
+
+
+def test_mcp_empty_tool_list():
+    """MCP server reporting zero tools should result in empty tool list."""
+    global server
+    # Create a minimal server that returns empty tools list
+    empty_server = os.path.join(FIXTURES_DIR, "_empty_mcp_server.py")
+    with open(empty_server, "w") as f:
+        f.write('''#!/usr/bin/env python3
+import json, sys, os
+def main():
+    sys.stdout = os.fdopen(sys.stdout.fileno(), "w", buffering=1)
+    for line in sys.stdin:
+        line = line.strip()
+        if not line: continue
+        try: request = json.loads(line)
+        except: continue
+        method = request.get("method")
+        req_id = request.get("id")
+        if method == "initialize":
+            resp = {"jsonrpc": "2.0", "id": req_id, "result": {"protocolVersion": "2024-11-05", "capabilities": {"tools": {}}, "serverInfo": {"name": "empty", "version": "1.0"}}}
+        elif method == "tools/list":
+            resp = {"jsonrpc": "2.0", "id": req_id, "result": {"tools": []}}
+        else:
+            resp = {"jsonrpc": "2.0", "id": req_id, "error": {"code": -32601, "message": "Method not found"}}
+        sys.stdout.write(json.dumps(resp) + "\\n")
+        sys.stdout.flush()
+if __name__ == "__main__":
+    main()
+''')
+    try:
+        mcp_json = _mcp_config_json({
+            "empty": {
+                "command": sys.executable,
+                "args": [empty_server],
+            }
+        })
+        server = _start_server_with_mcp(mcp_json)
+        res = server.make_request("GET", "/tools")
+        assert res.status_code == 200, res.body
+        tools = res.body
+        def get_tool_name(t):
+            return t.get("tool", "") or t.get("definition", {}).get("function", {}).get("name", "")
+        mcp_tools = [t for t in tools if get_tool_name(t).startswith("empty:")]
+        assert len(mcp_tools) == 0, f"Expected no empty: tools, got {mcp_tools}"
+    finally:
+        os.unlink(empty_server)
+        server.stop()
+
+
+def test_mcp_rapid_succession_calls():
+    """Many rapid calls should increment next_id correctly and correlate responses."""
+    global server
+    mcp_json = _mcp_config_json({
+        "echo": {
+            "command": sys.executable,
+            "args": [MCP_ECHO_SERVER],
+        }
+    })
+    server = _start_server_with_mcp(mcp_json)
+
+    try:
+        for i in range(20):
+            res = server.make_request("POST", "/tools", data={
+                "tool": "echo_echo",
+                "params": {"message": f"msg{i}"}
+            })
+            assert res.status_code == 200, res.body
+            assert "error" not in res.body, res.body
+    finally:
+        server.stop()
+
+
+def test_mcp_notification_burst():
+    """Notification + response in a single write() with no flush should not strand the response."""
+    global server
+    MCP_BURST_SERVER = os.path.join(FIXTURES_DIR, "mcp_burst_server.py")
+    mcp_json = _mcp_config_json({
+        "burst": {
+            "command": sys.executable,
+            "args": [MCP_BURST_SERVER],
+        }
+    })
+    server = _start_server_with_mcp(mcp_json)
+
+    try:
+        res = server.make_request("POST", "/tools", data={
+            "tool": "burst_echo",
+            "params": {"message": "burst test"}
+        })
+        assert res.status_code == 200, res.body
+        body = res.body
+        assert "error" not in body, body
+    finally:
+        server.stop()
+
+
+def test_mcp_tool_definition_shape_via_chat_completions():
+    """MCP tool definitions returned by GET /tools should have the correct shape for chat/completions."""
+    global server
+    mcp_json = _mcp_config_json({
+        "echo": {
+            "command": sys.executable,
+            "args": [MCP_ECHO_SERVER],
+        }
+    })
+    server = _start_server_with_mcp(mcp_json)
+
+    try:
+        # Get MCP tool definitions
+        res = server.make_request("GET", "/tools")
+        assert res.status_code == 200, res.body
+        tools = res.body
+
+        def get_tool_name(t):
+            return t.get("tool", "") or t.get("definition", {}).get("function", {}).get("name", "")
+
+        echo_tools = [t for t in tools if get_tool_name(t).startswith("echo_")]
+        assert len(echo_tools) >= 2, f"Expected echo_ tools, got {echo_tools}"
+
+        echo_tool = next(t for t in echo_tools if get_tool_name(t) == "echo_echo")
+        definition = echo_tool.get("definition", echo_tool)
+
+        # Verify the definition has the standard function-calling shape
+        assert definition.get("type") == "function", f"Expected type=function, got {definition.get('type')}"
+        func = definition.get("function", {})
+        assert "name" in func, "Missing function.name"
+        assert "description" in func, "Missing function.description"
+        assert "parameters" in func, f"Missing function.parameters, got keys: {list(func.keys())}"
+        params = func["parameters"]
+        assert params.get("type") == "object", f"Expected parameters.type=object, got {params.get('type')}"
+        assert "properties" in params, "Missing parameters.properties"
+    finally:
+        server.stop()
+
+
+def test_mcp_slow_tool_call_slot_release():
+    """A slow tool call should not stall server shutdown for the full I/O timeout."""
+    global server
+    MCP_SLOW_SERVER = os.path.join(FIXTURES_DIR, "mcp_slow_server.py")
+    mcp_json = _mcp_config_json({
+        "slow": {
+            "command": sys.executable,
+            "args": [MCP_SLOW_SERVER, "--delay", "10"],
+            "timeout_ms": 30000
+        }
+    })
+    server = _start_server_with_mcp(mcp_json)
+
+    try:
+        # Start a slow tool call in a background thread
+        def slow_call():
+            return server.make_request("POST", "/tools", data={
+                "tool": "slow_sleep",
+                "params": {"seconds": 10}
+            })
+
+        with ThreadPoolExecutor(max_workers=1) as executor:
+            future = executor.submit(slow_call)
+
+            # Wait a moment for the call to start
+            time.sleep(2)
+
+            # Stop the server while the tool call is in progress.
+            # With global MCP instances, close_all() is called explicitly at shutdown
+            # (not from slot release), so shutdown should complete promptly.
+            start_time = time.time()
+            server.stop()
+            elapsed = time.time() - start_time
+
+            # The server should stop quickly, not wait for the full 30s I/O timeout.
+            # With the terminating flag, send_rpc() bails out within one select()
+            # slice (~50ms). This threshold MUST stay below the 5s force-kill
+            # fallback in ServerProcess.stop(): without the flag, shutdown stalls
+            # on the instance mutex and only completes when stop() sends SIGKILL
+            # at ~5s -- which any threshold above 5 would still accept.
+            assert elapsed < 3, f"Server stop took {elapsed:.1f}s, expected < 3s"
+
+            # Wait for the future to complete (it will get an error response or timeout)
+            try:
+                res = future.result(timeout=5)
+                # If we got a response, it should be an error since the server stopped
+                if hasattr(res, 'status_code'):
+                    assert res.status_code in (200, 500, 502, 503, 504), f"Unexpected status: {res.status_code}"
+            except Exception:
+                # Thread may have raised due to connection error - that's acceptable
+                pass
+    finally:
+        server.stop()
+
+
+def test_mcp_grandchild_holding_pipes_does_not_deadlock():
+    """An MCP server that leaves a grandchild inheriting its stdout/stderr must not deadlock
+    teardown.
+
+    subprocess_terminate() only SIGKILLs the direct MCP child, so the inherited pipe write ends
+    stay open and a blocking read on them would never see EOF. That hung both warmup shutdown
+    (the server would never reach "ready") and process shutdown. The polled, running-aware reader
+    must exit regardless, so the server both starts and stops promptly here.
+    """
+    global server
+    MCP_GRANDCHILD_SERVER = os.path.join(FIXTURES_DIR, "mcp_grandchild_server.py")
+    mcp_json = _mcp_config_json({
+        "gc": {
+            "command": sys.executable,
+            "args": [MCP_GRANDCHILD_SERVER],
+        }
+    })
+
+    # If warmup teardown deadlocked, the server would never become ready and start() would time out.
+    server = _start_server_with_mcp(mcp_json)
+
+    try:
+        # invoking the tool spawns a live transport whose reader thread holds the inherited pipe
+        res = server.make_request("POST", "/tools", data={
+            "tool": "gc_echo",
+            "params": {"message": "hello"}
+        })
+        assert res.status_code == 200, res.body
+        assert "error" not in res.body, res.body
+
+        # shutdown must be prompt: a deadlocked reader-join would stall until the 5s SIGKILL
+        # fallback in ServerProcess.stop(), so the threshold has to stay below that
+        start = time.time()
+        server.stop()
+        elapsed = time.time() - start
+        assert elapsed < 3, f"server shutdown took {elapsed:.1f}s (expected < 3s) — teardown likely deadlocked"
+    finally:
+        server.stop()
diff --git a/tools/server/tests/utils.py b/tools/server/tests/utils.py
index 5d5c873ac4cc..ae56bc70a15a 100644
--- a/tools/server/tests/utils.py
+++ b/tools/server/tests/utils.py
@@ -115,6 +115,8 @@ class ServerProcess:
     backend_sampling: bool = False
     gcp_compat: bool = False
     server_tools: str | None = None
+    mcp_servers_config: str | None = None
+    mcp_servers_json: str | None = None
     cors_origins: str | None = None
 
     # session variables
@@ -265,6 +267,10 @@ def start(self, timeout_seconds: int = DEFAULT_HTTP_TIMEOUT) -> None:
             server_args.append("--ui-mcp-proxy")
         if self.server_tools:
             server_args.extend(["--tools", self.server_tools])
+        if self.mcp_servers_config:
+            server_args.extend(["--mcp-servers-config", self.mcp_servers_config])
+        if self.mcp_servers_json:
+            server_args.extend(["--mcp-servers-json", self.mcp_servers_json])
         if self.backend_sampling:
             server_args.append("--backend_sampling")
         if self.gcp_compat: