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fix(mcp): log the server/discover connect probe as info, not an error #2556

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Merged
DeusData merged 2 commits into from
Oct 20, 2026
Merged

fix(mcp): log the server/discover connect probe as info, not an error #2556

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6bc7ade
fix(mcp): log the server/discover connect probe as info, not an error
mvanhorn Oct 6, 2026
8af291d
Merge branch 'main' into fix/2433-server-discover-probe-log
DeusData Oct 20, 2026
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4 changes: 3 additions & 1 deletion src/mcp/mcp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -21029,7 +21029,9 @@ char *cbm_mcp_server_handle(cbm_mcp_server_t *srv, const char *line) {
cbm_clock_gettime(CLOCK_MONOTONIC, &t1);
long long dur_us = ((long long)(t1.tv_sec - req_t0.tv_sec) * MCP_S_TO_US) +
((long long)(t1.tv_nsec - req_t0.tv_nsec) / MCP_MS_TO_US);
cbm_log_mcp_request(req.method, NULL, true, dur_us);
/* server/discover is the modern connect probe. -32601 stays so the
* client falls back to initialize; that miss is not an error (#2433). */
cbm_log_mcp_request(req.method, NULL, strcmp(req.method, "server/discover") != 0, dur_us);
cbm_mcp_server_request_scope_end(srv);
cbm_jsonrpc_request_free(&req);
return err;
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54 changes: 54 additions & 0 deletions tests/test_mcp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2463,6 +2463,59 @@ TEST(server_handle_unknown_method) {
PASS();
}

/* Issue #2433: a modern client probes server/discover before initialize.
* The -32601 stays so it falls back; only that probe is logged as info. */
TEST(server_handle_discover_probe_logs_info) {
mcp_log_buf[0] = '\0';
CBMLogLevel prev_level = cbm_log_get_level();
cbm_log_set_level(CBM_LOG_DEBUG);
cbm_log_set_format(CBM_LOG_FORMAT_TEXT);
cbm_log_set_sink_ex(mcp_capture_log, CBM_LOG_SINK_REPLACE);

cbm_mcp_server_t *srv = cbm_mcp_server_new(NULL);

char *resp =
cbm_mcp_server_handle(srv, "{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"server/discover\"}");
ASSERT_NOT_NULL(resp);
ASSERT_NOT_NULL(strstr(resp, "\"code\":-32601"));
ASSERT_NOT_NULL(strstr(resp, "Method not found"));
ASSERT_NOT_NULL(strstr(mcp_log_buf, "method=server/discover"));
ASSERT_NOT_NULL(strstr(mcp_log_buf, "level=info"));
ASSERT_NOT_NULL(strstr(mcp_log_buf, "status=ok"));
ASSERT_NULL(strstr(mcp_log_buf, "level=warn"));
ASSERT_NULL(strstr(mcp_log_buf, "status=error"));
free(resp);

mcp_log_buf[0] = '\0';
resp =
cbm_mcp_server_handle(srv, "{\"jsonrpc\":\"2.0\",\"id\":3,\"method\":\"unknown/method\"}");
ASSERT_NOT_NULL(resp);
ASSERT_NOT_NULL(strstr(resp, "-32601"));
ASSERT_NOT_NULL(strstr(mcp_log_buf, "method=unknown/method"));
ASSERT_NOT_NULL(strstr(mcp_log_buf, "level=warn"));
ASSERT_NOT_NULL(strstr(mcp_log_buf, "status=error"));
free(resp);

resp = cbm_mcp_server_handle(srv, "{\"jsonrpc\":\"2.0\",\"id\":4,\"method\":\"initialize\","
"\"params\":{\"protocolVersion\":\"2026-07-28\"}}");
ASSERT_NOT_NULL(resp);
ASSERT_NOT_NULL(strstr(resp, "2025-11-25"));
ASSERT_NULL(strstr(resp, "2026-07-28"));
free(resp);

resp =
cbm_mcp_server_handle(srv, "{\"jsonrpc\":\"2.0\",\"id\":5,\"method\":\"resources/list\"}");
ASSERT_NOT_NULL(resp);
ASSERT_NOT_NULL(strstr(resp, "\"resources\":[]"));
ASSERT_NULL(strstr(resp, "-32601"));
free(resp);

cbm_mcp_server_free(srv);
cbm_log_set_sink(NULL);
cbm_log_set_level(prev_level);
PASS();
}

/* ══════════════════════════════════════════════════════════════════
* TOOL HANDLERS (via server_handle)
* ══════════════════════════════════════════════════════════════════ */
Expand Down Expand Up @@ -25013,6 +25066,7 @@ SUITE(mcp) {
RUN_TEST(server_handle_prompts_get_validates_arguments);
RUN_TEST(server_handle_logs_request_without_params);
RUN_TEST(server_handle_unknown_method);
RUN_TEST(server_handle_discover_probe_logs_info);

/* Server handle — edge cases */
RUN_TEST(server_handle_invalid_json);
Expand Down
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