From 01ea7e98c70c67a4196af0478202f1ba67cf8ae2 Mon Sep 17 00:00:00 2001
From: Graffioh <bregliascuola2002@gmail.com>
Date: Mon, 20 Jul 2026 18:57:24 +0200
Subject: [PATCH] fix(server): avoid parsing shadowed max-token aliases

---
 server/src/server/http_server.cpp | 17 ++++++++++++++---
 server/src/server/http_server.h   |  4 ++++
 server/test/test_server_unit.cpp  | 13 +++++++++++++
 3 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/server/src/server/http_server.cpp b/server/src/server/http_server.cpp
index 515af7ba0..1549cc339 100644
--- a/server/src/server/http_server.cpp
+++ b/server/src/server/http_server.cpp
@@ -378,6 +378,19 @@ static size_t json_array_size(const json & value) {
     return value.is_array() ? value.size() : 0;
 }
 
+int resolve_max_output_tokens(const json & body, int default_max_tokens) {
+    if (body.contains("max_tokens")) {
+        return body.at("max_tokens").get<int>();
+    }
+    if (body.contains("max_output_tokens")) {
+        return body.at("max_output_tokens").get<int>();
+    }
+    if (body.contains("max_completion_tokens")) {
+        return body.at("max_completion_tokens").get<int>();
+    }
+    return default_max_tokens;
+}
+
 static bool env_flag_enabled(const char * name) {
     const char * raw = std::getenv(name);
     if (!raw || !*raw) return false;
@@ -1409,9 +1422,7 @@ bool HttpServer::route_request(int fd, const HttpRequest & hr) {
         // default protects thinking-budget requests that omit max_tokens
         // from being capped at 4096 — thinking alone can consume that,
         // leaving no headroom for the visible reply.
-        req.max_output = body.value("max_tokens",
-                         body.value("max_output_tokens",
-                         body.value("max_completion_tokens", config_.default_max_tokens)));
+        req.max_output = resolve_max_output_tokens(body, config_.default_max_tokens);
         // Spec §4.4: clamp request max_tokens to --default-max-tokens.
         if (req.max_output > config_.default_max_tokens) {
             std::fprintf(stderr,
diff --git a/server/src/server/http_server.h b/server/src/server/http_server.h
index 957741b4d..0ea7e2213 100644
--- a/server/src/server/http_server.h
+++ b/server/src/server/http_server.h
@@ -228,6 +228,10 @@ struct ParsedRequest {
     DiskPrefixCachePolicy     disk_cache_policy;
 };
 
+// Resolve the supported output-token aliases in precedence order. Only the
+// selected field is parsed, so malformed lower-priority aliases are ignored.
+int resolve_max_output_tokens(const json & body, int default_max_tokens);
+
 // Build the /props response body. Exposed (non-static) so unit tests
 // can assert on its shape without spinning up a real socket. See
 // docs/specs/props-endpoint.md for the wire contract.
diff --git a/server/test/test_server_unit.cpp b/server/test/test_server_unit.cpp
index 7a5455b44..55876e8ce 100644
--- a/server/test/test_server_unit.cpp
+++ b/server/test/test_server_unit.cpp
@@ -1562,6 +1562,18 @@ static void test_pflash_raw_body_preserved() {
     TEST_ASSERT(req.raw_body["temperature"].get<float>() > 0.6f);
 }
 
+static void test_max_output_alias_precedence_ignores_shadowed_invalid_value() {
+    const json body = {
+        {"max_tokens", 100},
+        {"max_output_tokens", 200},
+        {"max_completion_tokens", "invalid"},
+    };
+
+    TEST_ASSERT(resolve_max_output_tokens(body, 400) == 100);
+    TEST_ASSERT(resolve_max_output_tokens({{"max_output_tokens", 200}}, 400) == 200);
+    TEST_ASSERT(resolve_max_output_tokens(json::object(), 400) == 400);
+}
+
 static void test_pflash_placement_same_backend_local() {
     DevicePlacement target;
     target.backend = compiled_placement_backend();
@@ -4555,6 +4567,7 @@ int main() {
     RUN_TEST(test_pflash_curve_empty_uses_flat);
     RUN_TEST(test_pflash_upstream_proxy_config);
     RUN_TEST(test_pflash_raw_body_preserved);
+    RUN_TEST(test_max_output_alias_precedence_ignores_shadowed_invalid_value);
     RUN_TEST(test_pflash_placement_same_backend_local);
     RUN_TEST(test_pflash_placement_mixed_backend_remote);
     RUN_TEST(test_pflash_placement_auto_draft_follows_target);