fix(langchain): remove orphaned context_api.attach() in on_chain_end

[dvirski]

Fixes #3526.

The SUPPRESS_LANGUAGE_MODEL_INSTRUMENTATION_KEY=False attach at the end
of on_chain_end() was redundant — _end_span() already detaches the
suppression token via SpanHolder. The orphaned attach was corrupting
the OTel context stack on every root chain completion.

Summary by CodeRabbit

• Bug Fixes
  • Prevented a context leak so suppression state is not left behind after a top-level chain ends, improving instrumentation correctness.
• Tests
  • Added regression tests to ensure suppression state remains absent after root chains and repeated root runs do not accumulate leaked context.

[CLAassistant]

All committers have signed the CLA.

[coderabbitai]

Caution

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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: 51907c7f-be2d-444e-8581-4750f6da5c65

📥 Commits

Reviewing files that changed from the base of the PR and between 11b718c and 226d5dd.

⛔ Files ignored due to path filters (1)

• packages/traceloop-sdk/uv.lock is excluded by !**/*.lock

📒 Files selected for processing (2)

• packages/opentelemetry-instrumentation-langchain/opentelemetry/instrumentation/langchain/callback_handler.py
• packages/opentelemetry-instrumentation-langchain/tests/test_context_token_lifecycle.py

💤 Files with no reviewable changes (1)

• packages/opentelemetry-instrumentation-langchain/opentelemetry/instrumentation/langchain/callback_handler.py

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

• packages/opentelemetry-instrumentation-langchain/tests/test_context_token_lifecycle.py

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📝 Walkthrough

Walkthrough

The PR removes an orphaned context_api.attach() in TraceloopCallbackHandler.on_chain_end that previously set SUPPRESS_LANGUAGE_MODEL_INSTRUMENTATION_KEY without detaching. It adds two regression tests ensuring the suppression context key is not left attached or accumulated across root chains.

Changes

Context Stack Corruption Fix

Layer / File(s)	Summary
Context Attachment Removal packages/opentelemetry-instrumentation-langchain/opentelemetry/instrumentation/langchain/callback_handler.py	Removed top-level-only context_api.attach(...) that set SUPPRESS_LANGUAGE_MODEL_INSTRUMENTATION_KEY=False without detaching; span end/status/output emission remains unchanged.
Regression tests for context token lifecycle packages/opentelemetry-instrumentation-langchain/tests/test_context_token_lifecycle.py	Adds test_on_chain_end_does_not_leak_context_frame and test_on_chain_end_context_stack_does_not_accumulate to assert the suppression key remains absent (None) after root chain completion and does not accumulate across repeated root chains.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Suggested reviewers

• galzilber
• nina-kollman
• max-deygin-traceloop
• netanel-tl
• doronkopit5

Poem

🐰 A stray attach I spied one day,
I nudged it gently far away,
Chains finish, spans sleep tight,
The context stack stays right,
Hops of traces homeward sway.

🚥 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 clearly and specifically describes the main change: removing an orphaned context_api.attach() call from on_chain_end to fix context stack corruption.
Linked Issues check	✅ Passed	The PR directly addresses issue #3526 by removing the orphaned context_api.attach() in on_chain_end that was leaving orphaned contexts on the OpenTelemetry stack, preventing corruption of context and restoring correct active-span behavior.
Out of Scope Changes check	✅ Passed	The changes are narrowly scoped to fixing the on_chain_end orphaned attach issue. Test changes focus on validating the fix and updating existing tests to match the revised code path, both directly related to the stated objective.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch dr/fix(langchain)-remove-orphaned-context_api.attach()-in-on_chain_end

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[doronkopit5]

can yuu add some reproduce test for this, a test that fails without your code

[dvirski]

recheck