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fix(llmobs): handle empty langchain chat model stream [backport 4.11]#18990

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fix(llmobs): handle empty langchain chat model stream [backport 4.11]#18990
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@dd-octo-sts dd-octo-sts Bot commented Jul 10, 2026

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Backport #18981 to 4.11

@github-actions @Yun-Kim
fix(llmobs): handle empty langchain chat model stream (#18981)
97d90a2 
## Description
Signed copy of #18610 by @anneheartrecord.

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## Testing

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## Risks

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## Additional Notes

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Co-authored-by: anneheartrecord <chengxisheng777@gmail.com>
Co-authored-by: yun.kim <yun.kim@datadoghq.com>
(cherry picked from commit 3978223)

Co-authored-by: Yun Kim <35776586+Yun-Kim@users.noreply.github.com>
@dd-octo-sts dd-octo-sts Bot requested review from a team as code owners July 10, 2026 20:23
@dd-octo-sts dd-octo-sts Bot requested review from brettlangdon and emmettbutler and removed request for a team July 10, 2026 20:23
@Yun-Kim Yun-Kim enabled auto-merge (squash) July 10, 2026 20:24
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cit-pr-commenter-54b7da Bot commented Jul 10, 2026

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Codeowners resolved as

ddtrace/llmobs/_integrations/langchain.py                               @DataDog/ml-observability
releasenotes/notes/fix-langchain-empty-chat-stream-llmobs-d35ddfc15c95dd42.yaml  @DataDog/apm-python
tests/contrib/langchain/test_langchain_llmobs.py                        @DataDog/ml-observability

@datadog-prod-us1-5

datadog-prod-us1-5 Bot commented Jul 10, 2026 •
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Pipelines  Tests

✨ Fix all issues with BitsAI

⚠️ Warnings

🚦 18 Pipeline jobs failed

System Tests | tracer-release / End-to-end #3 / flask-poc 3   View in Datadog   GitHub Actions

🧪 1 Test failed

tests.otel.test_tracing_otlp.Test_Otel_Tracing_OTLP.test_128bit_trace_id_consistent_across_spans[flask-poc] from system_tests_suite   View in Datadog 
AssertionError: Found 6 span(s) in the same logical trace with a different 128-bit traceId than the server span (server traceId=6a515746000000008d4ed3eabbdd8e0c). Mismatched (span_id, trace_id_hex): [(&#39;211815c14a566495&#39;, &#39;00000000000000008d4ed3eabbdd8e0c&#39;), (&#39;9e286d580e868956&#39;, &#39;00000000000000008d4ed3eabbdd8e0c&#39;), (&#39;ab90227facdd4904&#39;, &#39;00000000000000008d4ed3eabbdd8e0c&#39;), (&#39;eb14a3a4340fa701&#39;, &#39;00000000000000008d4ed3eabbdd8e0c&#39;), (&#39;a0940ca0baff65ee&#39;, &#39;00000000000000008d4ed3eabbdd8e0c&#39;), (&#39;6ed1c6ab01007305&#39;, &#39;00000000000000008d4ed3eabbdd8e0c&#39;)]. This indicates the OTLP exporter is not propagating _dd.p.tid (high 64 bits) from the chunk root to the remaining chunk spans.
assert not [(&#39;211815c14a566495&#39;, &#39;00000000000000008d4ed3eabbdd8e0c&#39;), (&#39;9e286d580e868956&#39;, &#39;00000000000000008d4ed3eabbdd8e0c&#39;), (...&#39;), (&#39;a0940ca0baff65ee&#39;, &#39;00000000000000008d4ed3eabbdd8e0c&#39;), (&#39;6ed1c6ab01007305&#39;, &#39;00000000000000008d4ed3eabbdd8e0c&#39;)]

self = &lt;tests.otel.test_tracing_otlp.Test_Otel_Tracing_OTLP object at 0x7fe7e46b66c0&gt;

    def test_128bit_trace_id_consistent_across_spans(self):
        &#34;&#34;&#34;Validates that every span in a trace carries the same full 128-bit OTLP traceId.
    
        DD tracers emit 128-bit trace IDs by default but the v04/v05 msgpack wire format only
        carries the lower 64 bits per span; the upper 64 bits live in the \`_dd.p.tid\` meta tag,
...

System Tests | tracer-release / End-to-end #3 / uds-flask 3   View in Datadog   GitHub Actions

🧪 1 Test failed

tests.otel.test_tracing_otlp.Test_Otel_Tracing_OTLP.test_128bit_trace_id_consistent_across_spans[uds-flask] from system_tests_suite   View in Datadog 
AssertionError: Found 6 span(s) in the same logical trace with a different 128-bit traceId than the server span (server traceId=6a5157320000000026c8cb31037f92d2). Mismatched (span_id, trace_id_hex): [(&#39;1922d9ee32b70e0c&#39;, &#39;000000000000000026c8cb31037f92d2&#39;), (&#39;658243ad9dd78f56&#39;, &#39;000000000000000026c8cb31037f92d2&#39;), (&#39;f5355e55597d7498&#39;, &#39;000000000000000026c8cb31037f92d2&#39;), (&#39;0cc5c22150d91e27&#39;, &#39;000000000000000026c8cb31037f92d2&#39;), (&#39;a326e255fcd25f07&#39;, &#39;000000000000000026c8cb31037f92d2&#39;), (&#39;271cd4466a394683&#39;, &#39;000000000000000026c8cb31037f92d2&#39;)]. This indicates the OTLP exporter is not propagating _dd.p.tid (high 64 bits) from the chunk root to the remaining chunk spans.
assert not [(&#39;1922d9ee32b70e0c&#39;, &#39;000000000000000026c8cb31037f92d2&#39;), (&#39;658243ad9dd78f56&#39;, &#39;000000000000000026c8cb31037f92d2&#39;), (...&#39;), (&#39;a326e255fcd25f07&#39;, &#39;000000000000000026c8cb31037f92d2&#39;), (&#39;271cd4466a394683&#39;, &#39;000000000000000026c8cb31037f92d2&#39;)]

self = &lt;tests.otel.test_tracing_otlp.Test_Otel_Tracing_OTLP object at 0x7f2a9c160a10&gt;

    def test_128bit_trace_id_consistent_across_spans(self):
        &#34;&#34;&#34;Validates that every span in a trace carries the same full 128-bit OTLP traceId.
    
        DD tracers emit 128-bit trace IDs by default but the v04/v05 msgpack wire format only
        carries the lower 64 bits per span; the upper 64 bits live in the \`_dd.p.tid\` meta tag,
...

System Tests | tracer-release / End-to-end #3 / uwsgi-poc 3   View in Datadog   GitHub Actions

🧪 1 Test failed

tests.otel.test_tracing_otlp.Test_Otel_Tracing_OTLP.test_128bit_trace_id_consistent_across_spans[uwsgi-poc] from system_tests_suite   View in Datadog 
AssertionError: Found 6 span(s) in the same logical trace with a different 128-bit traceId than the server span (server traceId=6a51574200000000acead5ac57901cc7). Mismatched (span_id, trace_id_hex): [(&#39;e09785af751a0b1d&#39;, &#39;0000000000000000acead5ac57901cc7&#39;), (&#39;2044d1500b172e79&#39;, &#39;0000000000000000acead5ac57901cc7&#39;), (&#39;e457b90d900f8328&#39;, &#39;0000000000000000acead5ac57901cc7&#39;), (&#39;32b2680fae869d0e&#39;, &#39;0000000000000000acead5ac57901cc7&#39;), (&#39;691b1062399357d5&#39;, &#39;0000000000000000acead5ac57901cc7&#39;), (&#39;a1b166e1c215e4fc&#39;, &#39;0000000000000000acead5ac57901cc7&#39;)]. This indicates the OTLP exporter is not propagating _dd.p.tid (high 64 bits) from the chunk root to the remaining chunk spans.
assert not [(&#39;e09785af751a0b1d&#39;, &#39;0000000000000000acead5ac57901cc7&#39;), (&#39;2044d1500b172e79&#39;, &#39;0000000000000000acead5ac57901cc7&#39;), (...&#39;), (&#39;691b1062399357d5&#39;, &#39;0000000000000000acead5ac57901cc7&#39;), (&#39;a1b166e1c215e4fc&#39;, &#39;0000000000000000acead5ac57901cc7&#39;)]

self = &lt;tests.otel.test_tracing_otlp.Test_Otel_Tracing_OTLP object at 0x7f2e3a2f0410&gt;

    def test_128bit_trace_id_consistent_across_spans(self):
        &#34;&#34;&#34;Validates that every span in a trace carries the same full 128-bit OTLP traceId.
    
        DD tracers emit 128-bit trace IDs by default but the v04/v05 msgpack wire format only
        carries the lower 64 bits per span; the upper 64 bits live in the \`_dd.p.tid\` meta tag,
...

View all 18 failed jobs.

ℹ️ Info

No other issues found (see more)

❄️ No new flaky tests detected

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@Yun-Kim Yun-Kim Yun-Kim approved these changes
@emmettbutler emmettbutler Awaiting requested review from emmettbutler emmettbutler is a code owner automatically assigned from DataDog/apm-python
@brettlangdon brettlangdon Awaiting requested review from brettlangdon brettlangdon is a code owner automatically assigned from DataDog/apm-python

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