fix: normalize Gemma 4 thought-channel output (#2224)

tests/test_chat_helpers.py

@@ -1,5 +1,5 @@
 import pytest
-from routes.chat_helpers import needs_auto_name
+from routes.chat_helpers import clean_thinking_for_save, needs_auto_name
 
 
 @pytest.mark.parametrize("name,expected", [
@@ -27,3 +27,44 @@ from routes.chat_helpers import needs_auto_name
 ])
 def test_needs_auto_name(name, expected):
     assert needs_auto_name(name) == expected, f"needs_auto_name({name!r}) should be {expected}"
+
+
+def test_clean_thinking_for_save_extracts_gemma4_thought_channel():
+    content, metadata = clean_thinking_for_save(
+        "<|channel>thought\ninternal reasoning<channel|>Final answer.",
+        {"model": "google/gemma-4-31B-it"},
+    )
+
+    assert content == "Final answer."
+    assert metadata["thinking"] == "internal reasoning"
+    assert metadata["model"] == "google/gemma-4-31B-it"
+
+
+def test_clean_thinking_for_save_strips_empty_gemma4_thought_channel():
+    content, metadata = clean_thinking_for_save(
+        "<|channel>thought\n<channel|>Final answer.",
+        {"model": "google/gemma-4-31B-it"},
+    )
+
+    assert content == "Final answer."
+    assert "thinking" not in metadata
+
+
+def test_clean_thinking_for_save_unwraps_gemma4_response_channel():
+    content, metadata = clean_thinking_for_save(
+        "<|channel>thought\ninternal reasoning<channel|><|channel>response\nFinal answer.<channel|>",
+        {"model": "google/gemma-4-31B-it"},
+    )
+
+    assert content == "Final answer."
+    assert metadata["thinking"] == "internal reasoning"
+
+
+def test_clean_thinking_for_save_extracts_thought_tag():
+    content, metadata = clean_thinking_for_save(
+        "<thought>internal reasoning</thought>Final answer.",
+        {},
+    )
+
+    assert content == "Final answer."
+    assert metadata["thinking"] == "internal reasoning"

tests/test_markdown_rendering_js.py

@@ -18,7 +18,7 @@ def node_available():
         pytest.skip("node binary not on PATH")
 
 
-def _run_markdown_case(markdown: str) -> str:
+def _run_markdown_case(markdown: str, render_expr: str = "mod.mdToHtml(input)"):
     script = textwrap.dedent(
         r"""
         import fs from 'node:fs';
@@ -54,9 +54,9 @@ def _run_markdown_case(markdown: str) -> str:
         const moduleUrl = 'data:text/javascript;base64,' + Buffer.from(source).toString('base64');
         const mod = await import(moduleUrl);
         const input = JSON.parse(process.argv[1]);
-        console.log(JSON.stringify({ html: mod.mdToHtml(input) }));
+        console.log(JSON.stringify({ html: __RENDER_EXPR__ }));
         """
-    )
+    ).replace("__RENDER_EXPR__", render_expr)
     result = subprocess.run(
         ["node", "--input-type=module", "-e", script, json.dumps(markdown)],
         cwd=_REPO,
@@ -99,3 +99,51 @@ def test_table_separator_row_not_rendered_as_data(node_available):
     assert "<th" in html
     assert "<td" in html
     assert "---" not in html
+
+
+def test_process_with_thinking_handles_gemma4_thought_channel(node_available):
+    html = _run_markdown_case(
+        "<|channel>thought\ninternal reasoning<channel|>Final answer.",
+        "mod.processWithThinking(input)",
+    )
+
+    assert "thinking-section" in html
+    assert "internal reasoning" in html
+    assert "Final answer." in html
+    assert "&lt;|channel&gt;" not in html
+    assert "<|channel>" not in html
+
+
+def test_process_with_thinking_strips_empty_gemma4_thought_channel(node_available):
+    html = _run_markdown_case(
+        "<|channel>thought\n<channel|>Final answer.",
+        "mod.processWithThinking(input)",
+    )
+
+    assert "thinking-section" not in html
+    assert "Final answer." in html
+    assert "&lt;|channel&gt;" not in html
+    assert "<|channel>" not in html
+
+
+def test_process_with_thinking_unwraps_gemma4_response_channel(node_available):
+    html = _run_markdown_case(
+        "<|channel>thought\ninternal reasoning<channel|><|channel>response\nFinal answer.<channel|>",
+        "mod.processWithThinking(input)",
+    )
+
+    assert "thinking-section" in html
+    assert "internal reasoning" in html
+    assert "Final answer." in html
+    assert "&lt;|channel&gt;" not in html
+    assert "<|channel>" not in html
+
+
+def test_extract_thinking_blocks_handles_thought_tag(node_available):
+    result = _run_markdown_case(
+        "<thought>internal reasoning</thought>Final answer.",
+        "mod.extractThinkingBlocks(input)",
+    )
+
+    assert result["thinkingBlocks"] == ["internal reasoning"]
+    assert result["content"] == "Final answer."

tests/test_strip_think.py

@@ -23,3 +23,22 @@ def test_strip_think_cases():
     
     # 6. Multiple blocks (closed + unclosed)
     assert strip_think("Hello! <think> closed </think> Here is the answer. <think> unclosed") == "Hello! Here is the answer."
+
+
+def test_strip_think_handles_thought_tags():
+    assert strip_think("<thought>internal reasoning</thought>Final answer.") == "Final answer."
+
+
+def test_strip_think_handles_gemma4_thought_channel():
+    text = "<|channel>thought\ninternal reasoning<channel|>Final answer."
+    assert strip_think(text) == "Final answer."
+
+
+def test_strip_think_handles_empty_gemma4_thought_channel():
+    text = "<|channel>thought\n<channel|>Final answer."
+    assert strip_think(text) == "Final answer."
+
+
+def test_strip_think_unwraps_gemma4_response_channel():
+    text = "<|channel>thought\ninternal reasoning<channel|><|channel>response\nFinal answer.<channel|>"
+    assert strip_think(text) == "Final answer."