test(langgraph): 4 conformance fixtures (text, tool, reasoning, multi-step)

Registers LangGraph-specific conformance fixtures with the shared harness
conformance runner. Documents the AGX1-377 behavior (tool requests are Full
events, not Start+Done). Span derivation is deterministic for all 4 fixtures.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: declan-scale

tests/lib/core/harness/conformance/test_langgraph_conformance.py

@@ -0,0 +1,206 @@
+"""LangGraph conformance fixtures for the cross-channel span-derivation test.
+
+Registers 4 LangGraph event sequences as conformance fixtures:
+- text-only: a plain text response (no tool calls)
+- single-tool: one tool call + response
+- reasoning: a reasoning block + text
+- multi-step: two turns with tool calls
+
+AGX1-377 note: LangGraph emits tool requests as ``StreamTaskMessageFull``
+(from "updates" events), NOT Start+Delta+Done like pydantic-ai. The SpanDeriver
+does not produce tool spans from Full events today; that gap is tracked in
+AGX1-373. The fixtures here document the current behavior and will be updated
+when AGX1-373 resolves.
+"""
+
+from __future__ import annotations
+
+import pytest
+
+from agentex.types.text_content import TextContent
+from agentex.types.reasoning_content import ReasoningContent
+from agentex.types.task_message_delta import TextDelta
+from agentex.types.task_message_update import (
+    StreamTaskMessageDone,
+    StreamTaskMessageFull,
+    StreamTaskMessageDelta,
+    StreamTaskMessageStart,
+)
+from agentex.types.tool_request_content import ToolRequestContent
+from agentex.types.tool_response_content import ToolResponseContent
+from agentex.types.reasoning_content_delta import ReasoningContentDelta
+
+from .runner import Fixture, register, derive_all
+
+# ---------------------------------------------------------------------------
+# Fixtures
+# ---------------------------------------------------------------------------
+
+_TEXT_ONLY = Fixture(
+    name="langgraph-text-only",
+    events=[
+        StreamTaskMessageStart(
+            type="start",
+            index=0,
+            content=TextContent(type="text", author="agent", content=""),
+        ),
+        StreamTaskMessageDelta(
+            type="delta",
+            index=0,
+            delta=TextDelta(type="text", text_delta="Hello from LangGraph!"),
+        ),
+        StreamTaskMessageDone(type="done", index=0),
+    ],
+)
+
+_SINGLE_TOOL = Fixture(
+    name="langgraph-single-tool",
+    events=[
+        # LangGraph tool request is a Full event (AGX1-377)
+        StreamTaskMessageFull(
+            type="full",
+            index=0,
+            content=ToolRequestContent(
+                type="tool_request",
+                author="agent",
+                tool_call_id="call_1",
+                name="get_weather",
+                arguments={"city": "Paris"},
+            ),
+        ),
+        StreamTaskMessageFull(
+            type="full",
+            index=1,
+            content=ToolResponseContent(
+                type="tool_response",
+                author="agent",
+                tool_call_id="call_1",
+                name="get_weather",
+                content="Sunny, 72F",
+            ),
+        ),
+        StreamTaskMessageStart(
+            type="start",
+            index=2,
+            content=TextContent(type="text", author="agent", content=""),
+        ),
+        StreamTaskMessageDelta(
+            type="delta",
+            index=2,
+            delta=TextDelta(type="text", text_delta="The weather in Paris is sunny, 72F."),
+        ),
+        StreamTaskMessageDone(type="done", index=2),
+    ],
+)
+
+_REASONING = Fixture(
+    name="langgraph-reasoning",
+    events=[
+        StreamTaskMessageStart(
+            type="start",
+            index=0,
+            content=ReasoningContent(
+                type="reasoning",
+                author="agent",
+                summary=[],
+                content=[],
+                style="active",
+            ),
+        ),
+        StreamTaskMessageDelta(
+            type="delta",
+            index=0,
+            delta=ReasoningContentDelta(
+                type="reasoning_content",
+                content_index=0,
+                content_delta="Thinking about this...",
+            ),
+        ),
+        StreamTaskMessageDone(type="done", index=0),
+        StreamTaskMessageStart(
+            type="start",
+            index=1,
+            content=TextContent(type="text", author="agent", content=""),
+        ),
+        StreamTaskMessageDelta(
+            type="delta",
+            index=1,
+            delta=TextDelta(type="text", text_delta="The answer is 42."),
+        ),
+        StreamTaskMessageDone(type="done", index=1),
+    ],
+)
+
+_MULTI_STEP = Fixture(
+    name="langgraph-multi-step",
+    events=[
+        # Turn 1: text + tool call
+        StreamTaskMessageStart(
+            type="start",
+            index=0,
+            content=TextContent(type="text", author="agent", content=""),
+        ),
+        StreamTaskMessageDelta(
+            type="delta",
+            index=0,
+            delta=TextDelta(type="text", text_delta="Let me search for that."),
+        ),
+        StreamTaskMessageDone(type="done", index=0),
+        # Tool request (Full — AGX1-377)
+        StreamTaskMessageFull(
+            type="full",
+            index=1,
+            content=ToolRequestContent(
+                type="tool_request",
+                author="agent",
+                tool_call_id="call_2",
+                name="search",
+                arguments={"query": "langgraph"},
+            ),
+        ),
+        StreamTaskMessageFull(
+            type="full",
+            index=2,
+            content=ToolResponseContent(
+                type="tool_response",
+                author="agent",
+                tool_call_id="call_2",
+                name="search",
+                content="LangGraph is a framework for...",
+            ),
+        ),
+        # Turn 2: final text
+        StreamTaskMessageStart(
+            type="start",
+            index=3,
+            content=TextContent(type="text", author="agent", content=""),
+        ),
+        StreamTaskMessageDelta(
+            type="delta",
+            index=3,
+            delta=TextDelta(type="text", text_delta="Based on my research, LangGraph is..."),
+        ),
+        StreamTaskMessageDone(type="done", index=3),
+    ],
+)
+
+_LANGGRAPH_FIXTURES = [_TEXT_ONLY, _SINGLE_TOOL, _REASONING, _MULTI_STEP]
+
+for _fixture in _LANGGRAPH_FIXTURES:
+    register(_fixture)
+
+
+# ---------------------------------------------------------------------------
+# Tests
+# ---------------------------------------------------------------------------
+
+
+@pytest.mark.parametrize("fixture", _LANGGRAPH_FIXTURES, ids=lambda f: f.name)
+def test_langgraph_span_derivation_is_deterministic(fixture: Fixture):
+    """Exercises the cross-channel guarantee: yield and auto-send observe the
+    same event stream, so span derivation must be deterministic/idempotent.
+
+    Deriving twice over the same events yields identical signals (the property
+    that makes yield vs auto-send equivalent, since both observe the same stream).
+    """
+    assert derive_all(fixture.events) == derive_all(fixture.events)