feat(mcp): get zone stats for a single thread

get_all_zone_stats mixes every thread, so the main-thread cost of a
zone could not be separated from worker threads. get_thread_zone_stats
returns the same per-name stats for the zones recorded on one thread,
and its per-thread sums match get_all_zone_stats exactly.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01L3DnWkXakGRgz9C8BaLM47

extra/mcp/eval_guide.md

@@ -19,6 +19,9 @@ data surface. Common entry points:
 - Frames: `get_frame_count()`, `get_frame_times()`, `get_frame_times_named(name)`,
   `get_frame_boundaries()`, `get_zones_in_frame(...)`
 - Threads: `get_threads()`, `get_thread_name(tid)`, `get_thread_context_switches(tid)`
+  `get_thread_zone_stats(tid)` is `get_all_zone_stats()` restricted to one thread's zones,
+  so a main-thread cost is not mixed with worker threads. A zone name used at several
+  source locations appears once in both, for its last location.
 - Messages / plots / locks / memory / callstacks: `get_messages()`, `get_plots()`,
   `get_locks()`, `get_memory_events()`, `get_callstack_frames(...)`
 - Plot samples: `get_plot_samples(name, start_ns=0, end_ns=max, max_samples=100000)` returns

extra/mcp/test_thread_zone_stats.py

@@ -0,0 +1,37 @@
+"""Needs a saved trace:
+    TRACY_TEST_TRACE=/path/to.tracy python -m pytest extra/mcp/test_thread_zone_stats.py
+"""
+import os
+import time
+
+import pytest
+
+import tracy_mcp
+
+TRACE = os.environ.get("TRACY_TEST_TRACE")
+pytestmark = pytest.mark.skipif(not TRACE, reason="TRACY_TEST_TRACE not set")
+
+
+@pytest.fixture(scope="module")
+def worker():
+    server = tracy_mcp.tracy_server
+    w = server.create_worker_from_file(server.open_file(TRACE))
+    while not w.is_background_done():
+        time.sleep(0.1)
+    yield w
+    w.shutdown()
+
+
+def test_threads_partition_the_global_stats(worker):
+    counts, totals = {}, {}
+    for thread in worker.get_threads():
+        for name, stats in worker.get_thread_zone_stats(thread["id"]).items():
+            counts[name] = counts.get(name, 0) + stats.count
+            totals[name] = totals.get(name, 0) + stats.total
+    for name, stats in worker.get_all_zone_stats().items():
+        assert counts.get(name, 0) == stats.count
+        assert totals.get(name, 0) == stats.total
+
+
+def test_unknown_thread_is_empty(worker):
+    assert worker.get_thread_zone_stats(2**40) == {}

python/bindings/ServerModule.cpp

@@ -323,6 +323,42 @@ PYBIND11_MODULE( TracyServerBindings, m )
         return result;
     } ) )
 
+        .def( "get_thread_zone_stats", locked( +[]( const Worker& w, uint64_t threadId ) {
+            // Same shape and name handling as get_all_zone_stats(), counting only zones recorded on one thread
+        py::dict result;
+#ifndef TRACY_NO_STATISTICS
+        std::unordered_map<std::string, int16_t> chosen;
+        for( const auto& kv : w.GetSourceLocationZones() )
+        {
+            if( kv.second.zones.size() == 0 ) continue;
+            chosen[w.GetZoneName( w.GetSourceLocation( kv.first ) )] = kv.first;
+        }
+        for( const auto& kv : w.GetSourceLocationZones() )
+        {
+            const std::string name = w.GetZoneName( w.GetSourceLocation( kv.first ) );
+            const auto it = chosen.find( name );
+            if( it == chosen.end() || it->second != kv.first ) continue;
+            int64_t min = INT64_MAX, max = INT64_MIN, total = 0;
+            double sumSq = 0;
+            size_t count = 0;
+            for( const auto& ztd : kv.second.zones )
+            {
+                if( w.DecompressThread( ztd.Thread() ) != threadId ) continue;
+                const auto* z = ztd.Zone();
+                if( !z || !z->IsEndValid() ) continue;
+                const int64_t dur = z->End() - z->Start();
+                total += dur;
+                sumSq += (double)dur * dur;
+                count++;
+                if( dur < min ) min = dur;
+                if( dur > max ) max = dur;
+            }
+            if( count ) result[name.c_str()] = ZoneStats{ min, max, total, sumSq, count, (double)total / count };
+        }
+#endif
+        return result;
+    } ), "thread_id"_a )
+
         // --- Per-occurrence zone data (for temporal correlation / distribution) ---
         .def( "get_zone_durations", locked( +[]( const Worker& w, const std::string& name, size_t maxSamples ) {
             // Accumulates across ALL srclocs with this name (same name can appear at multiple srclocs)