diff --git a/src/philosophy_bench/providers.py b/src/philosophy_bench/providers.py
index bb1001e..c2a237f 100644
--- a/src/philosophy_bench/providers.py
+++ b/src/philosophy_bench/providers.py
@@ -720,18 +720,23 @@ async def call_gemini(
                 )
             )
 
+    # Always opt into thought summaries. Without `include_thoughts=True` the
+    # Gemini API will reason internally but return zero thought parts to the
+    # caller — silently producing an empty thinking trace in the transcript
+    # even though the model is using its thinking budget. `thinking_level` is
+    # optional (Gemini 2.5 lacks the param; passing None preserves the model's
+    # auto/dynamic budget).
     thinking_level = spec.thinking_config.get("thinking_level")
+    thinking_config_kwargs: dict = {"include_thoughts": True}
+    if thinking_level:
+        thinking_config_kwargs["thinking_level"] = thinking_level
     config_kwargs = dict(
         system_instruction=system,
         max_output_tokens=8192,
         temperature=spec.temperature,
         tools=_gemini_tools(tools),
+        thinking_config=genai_types.ThinkingConfig(**thinking_config_kwargs),
     )
-    if thinking_level:
-        config_kwargs["thinking_config"] = genai_types.ThinkingConfig(
-            thinking_level=thinking_level,
-            include_thoughts=True,
-        )
     config = genai_types.GenerateContentConfig(**config_kwargs)
 
     def _call():
diff --git a/tests/test_providers_gemini.py b/tests/test_providers_gemini.py
new file mode 100644
index 0000000..ae3cd7a
--- /dev/null
+++ b/tests/test_providers_gemini.py
@@ -0,0 +1,87 @@
+"""Regression test: Gemini calls always opt into thought summaries.
+
+If `include_thoughts` isn't set on `ThinkingConfig`, Gemini reasons
+internally but returns zero thought parts to the caller, silently producing
+empty thinking traces in the bench transcripts.
+"""
+
+from __future__ import annotations
+
+
+def _build_thinking_config(spec):
+    """Mirror the assembly in providers.call_gemini() without making an API
+    call. Importing the real path under a mocked `google.genai.types` would
+    require pulling the SDK in; instead, instantiate the fields directly."""
+
+    # Stand-in for genai_types.ThinkingConfig — captures kwargs.
+    class _StubTC:
+        def __init__(self, **kw):
+            self.kwargs = kw
+
+    class _StubTypes:
+        ThinkingConfig = _StubTC
+
+    # Re-execute the relevant block from call_gemini against the stub.
+    thinking_level = spec.thinking_config.get("thinking_level")
+    thinking_config_kwargs = {"include_thoughts": True}
+    if thinking_level:
+        thinking_config_kwargs["thinking_level"] = thinking_level
+    return _StubTypes.ThinkingConfig(**thinking_config_kwargs)
+
+
+def _spec(**thinking_config):
+    """Tiny fake ModelSpec exposing only `thinking_config`."""
+    from types import SimpleNamespace
+
+    return SimpleNamespace(thinking_config=dict(thinking_config))
+
+
+def test_thinking_config_includes_thoughts_for_gemini_25():
+    """Gemini 2.5 specs have empty thinking_config — bug was that
+    `include_thoughts=True` only got set when `thinking_level` was present."""
+    cfg = _build_thinking_config(_spec())
+    assert cfg.kwargs.get("include_thoughts") is True
+    assert "thinking_level" not in cfg.kwargs
+
+
+def test_thinking_config_includes_thoughts_for_gemini_3x():
+    """Gemini 3.x specs set thinking_level=MEDIUM. Both fields should land
+    on the config."""
+    cfg = _build_thinking_config(_spec(thinking_level="MEDIUM"))
+    assert cfg.kwargs.get("include_thoughts") is True
+    assert cfg.kwargs.get("thinking_level") == "MEDIUM"
+
+
+def test_real_provider_module_assembly_uses_include_thoughts():
+    """Smoke test: scan providers.py source to confirm the regression
+    isn't reintroduced by an editor merging the include_thoughts back into
+    a conditional branch."""
+    from pathlib import Path
+
+    src = Path(__file__).resolve().parents[1] / "src" / "philosophy_bench" / "providers.py"
+    text = src.read_text()
+    # The fix sets include_thoughts=True unconditionally inside call_gemini.
+    # If a future change re-introduces a conditional gating include_thoughts,
+    # this test will catch it.
+    gemini_block_start = text.index("async def call_gemini")
+    gemini_block_end = text.index("async def ", gemini_block_start + 1)
+    block = text[gemini_block_start:gemini_block_end]
+    assert "include_thoughts=True" in block, (
+        "call_gemini must always pass include_thoughts=True; otherwise "
+        "Gemini 2.5 family produces empty thinking traces."
+    )
+    # Also: make sure include_thoughts is NOT inside an `if thinking_level:`
+    # conditional anymore.
+    if_block_start = block.find("if thinking_level:")
+    if if_block_start != -1:
+        # If there's still a conditional, include_thoughts must NOT be
+        # gated by it. We check this by ensuring the if-block doesn't
+        # contain include_thoughts=True.
+        if_block_end = block.find("\n    ", if_block_start + 1)
+        if if_block_end == -1:
+            if_block_end = len(block)
+        if_block = block[if_block_start:if_block_end]
+        assert "include_thoughts=True" not in if_block, (
+            "include_thoughts=True is gated behind `if thinking_level:` — "
+            "this reintroduces the Gemini 2.5 empty-thought-trace bug."
+        )