feat(together): add finish_reason attribute to spans

[raghavenderreddygrudhanti]

What

Adds gen_ai.response.finish_reason attribute to Together AI spans.

Why

Other instrumentations (OpenAI, Anthropic, Groq) already capture this attribute. It's useful for monitoring stop reasons (eos, length, stop) and alerting on unexpected truncations.

Changes

• Added finish_reason extraction in span_utils.py
• Added test assertion in test_chat.py

Summary by CodeRabbit

• Bug Fixes

  • Telemetry now records the AI response completion reason in observability spans (captures finish reason or null).

• Tests

  • Added/updated tests to validate response completion reason attributes in instrumentation tests.

• Documentation

  • Improved docstrings for span-attribute helper functions to clarify their behavior.

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 01b047bd-813e-4b0f-babd-dfd520a35bda

📥 Commits

Reviewing files that changed from the base of the PR and between 7f4ea5a and 278dcf3.

📒 Files selected for processing (1)

• packages/opentelemetry-instrumentation-together/opentelemetry/instrumentation/together/span_utils.py

🚧 Files skipped from review as they are similar to previous changes (1)

• packages/opentelemetry-instrumentation-together/opentelemetry/instrumentation/together/span_utils.py

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📝 Walkthrough

Walkthrough

The PR captures the model response finish reason into the span as gen_ai.response.finish_reason (from the first response choice) and adds a test assertion that it equals "eos".

Changes

Response finish reason tracking

Layer / File(s)	Summary
Set response finish reason span attribute packages/opentelemetry-instrumentation-together/opentelemetry/instrumentation/together/span_utils.py	Docstrings added for span helpers; set_model_completion_attributes sets SpanAttributes.GEN_AI_RESPONSE_FINISH_REASON from response.choices[0].finish_reason when choices exist, otherwise None.
Validate finish reason in tests packages/opentelemetry-instrumentation-together/tests/test_chat.py	Test assertion added to verify together_span.attributes["gen_ai.response.finish_reason"] == "eos".

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 I sniff the span, a tiny clue,
A finish reason peeks right through,
From choice one’s whisper, "eos" in tow,
I hop and trace the telemetry glow.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'feat(together): add finish_reason attribute to spans' directly and clearly summarizes the main change: adding the finish_reason attribute to Together AI spans.
Docstring Coverage	✅ Passed	Docstring coverage is 83.33% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[raghavenderreddygrudhanti]

Looks good overall. The GEN_AI_RESPONSE_FINISH_REASON attribute is being set safely with a fallback when response.choices is unavailable. I reviewed the implementation and validation layer.

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