fix(bedrock): don't count a missing guardrailAction as an activation

[AnoshanJ]

Fixes #4471.

is_guardrail_activated() ended with:

return response.get("amazon-bedrock-guardrailAction") != "NONE"

Bedrock omits amazon-bedrock-guardrailAction when no guardrail is configured, so .get() returns None and None != "NONE" is True. Every ordinary response was counted as a guardrail activation, incrementing gen_ai.bedrock.guardrail.activation on every Bedrock call.

Defaulting the key to "NONE" restores the intended meaning. The two checks above it already cover the real activation paths (CONTENT_FILTERED in results, and stopReason == "guardrail_intervened").

Added unit tests covering a response with no guardrail key, a configured guardrail that did not fire, and the three activation paths. The first case fails without this change.

The existing guardrail cassettes are unaffected: all eight signal activation explicitly, either via guardrail_intervened or amazon-bedrock-guardrailAction: INTERVENED, so none of them relied on the fallthrough.

---

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• If adding a new instrumentation or changing an existing one, I've added screenshots from some observability platform showing the change.
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Summary by CodeRabbit

• Bug Fixes

  • Corrected guardrail activation detection when Bedrock responses omit the guardrail action; responses without an activation signal are no longer reported as activations.
  • Guardrail interventions are recognized through supported action, stop-reason, and completion-reason signals, including in streaming responses.
  • Guardrail details remain available when metrics are disabled, without attempting to record unavailable metrics.

• Tests

  • Added coverage for missing actions, inactive guardrails, intervention scenarios, and synchronous and asynchronous streaming.

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• packages/opentelemetry-instrumentation-bedrock/opentelemetry/instrumentation/bedrock/__init__.py

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📝 Walkthrough

Walkthrough

Bedrock guardrail instrumentation now treats missing guardrail actions as inactive and skips metric measurements when their instruments are absent. Converse stream handlers pass the retained message stop reason with metadata to guardrail handling. Tests cover activation detection, metrics-disabled spans, and synchronous and asynchronous streams.

Changes

Bedrock guardrail activation

Layer / File(s)	Summary
Guardrail detection and metric handling packages/opentelemetry-instrumentation-bedrock/opentelemetry/instrumentation/bedrock/guardrail.py, packages/opentelemetry-instrumentation-bedrock/tests/test_guardrail_activation.py	The helper defaults a missing amazon-bedrock-guardrailAction value to "NONE". Guardrail measurements are added only when the corresponding metric instruments are present. Tests cover activation detection and span attributes when metrics are disabled.
Converse stream stop reason handling packages/opentelemetry-instrumentation-bedrock/opentelemetry/instrumentation/bedrock/__init__.py, packages/opentelemetry-instrumentation-bedrock/tests/test_guardrail_activation.py	Synchronous and asynchronous stream handlers pass the retained messageStop.stopReason with metadata to guardrail handling. Tests check activation counts for intervention and end-turn reasons, and span completion with metrics disabled.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix · Severity of issue fixed: Medium

Merge Risk: ⚪ Minimal · up to da654

Missing guardrail actions are treated as inactive, unavailable metric instruments are skipped, and both stream paths pass the stop reason into activation detection. No concrete merge-blocking risk is established; normal checks remain appropriate.

Architecture Summary

Architecture risk: 🔵 Low · up to da654

The change affects 1 system.

Changed systems: packages/opentelemetry-instrumentation-bedrock

Architecture concerns
No architecture-level concerns identified.

Review details

Systems and components

• observed — packages/opentelemetry-instrumentation-bedrock (library) was modified; 3 changed files map to changed impact.

Before / after behavior

• observed — Modified behavior in packages/opentelemetry-instrumentation-bedrock/opentelemetry/instrumentation/bedrock/guardrail.py: is_guardrail_activated now defaults a missing amazon-bedrock-guardrailAction value to "NONE"; missing-action responses therefore return False instead of treating None as an activated guardrail.
• observed — Modified behavior in packages/opentelemetry-instrumentation-bedrock/opentelemetry/instrumentation/bedrock/guardrail.py: handle_invoke_metrics now records latency and coverage only when their respective metric instruments are present; previously it called each instrument unconditionally when the corresponding response data existed.
• observed — Modified behavior in packages/opentelemetry-instrumentation-bedrock/opentelemetry/instrumentation/bedrock/guardrail.py: handle_sensitive now adds PII and regex measurements only when guardrail_sensitive_info is present. It still collects the corresponding PII types and regex names.
• observed — Modified behavior in packages/opentelemetry-instrumentation-bedrock/opentelemetry/instrumentation/bedrock/guardrail.py: handle_topic now adds topic measurements only when guardrail_topic is present; it still collects blocked topic names.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 3.57% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 28 functions across 3 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: missing guardrailAction values no longer count as guardrail activations.
Linked Issues check	✅ Passed	The PR satisfies the coding requirements in issue #4471. is_guardrail_activated defaults a missing amazon-bedrock-guardrailAction to "NONE". Activation metric updates now check for absent instru…
Out of Scope Changes check	✅ Passed	The changes stay within issue #4471. Stream stopReason propagation supports correct activation detection. Metric guards and span-attribute tests address the reported metrics-disabled failure. No unr…

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Inline comments:
In
`@packages/opentelemetry-instrumentation-bedrock/tests/test_guardrail_activation.py`:
- Around line 4-19: Add a regression test for the instrumented Converse path
that uses a response without amazon-bedrock-guardrailAction and asserts the
guardrail_activation metric remains zero. Reuse the existing Converse
instrumentation and metrics setup, preserving current activation assertions for
responses that explicitly indicate intervention.

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• packages/opentelemetry-instrumentation-bedrock/opentelemetry/instrumentation/bedrock/guardrail.py
• packages/opentelemetry-instrumentation-bedrock/tests/test_guardrail_activation.py

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[Santoshkumarpuppala]

This turns test_guardrail_converse_stream red: converse_stream no longer records activation when the stream reports guardrail_intervened on messageStop.

Ran at 6f9be7a: pytest tests/traces/test_guardrails.py gives 1 failed, 3 passed. The KeyError on gen_ai.bedrock.guardrail.input_filter (test_guardrails.py:299) is because span attributes are only set when activation is true (guardrail.py:178-180). Reverting only guardrail.py:34 gives 4 passed. A one-off script replaying the metrics cassettes shows guardrail.activation per converse_stream call is 0 here, 1 on main; converse is 1 on both. CI hasn't run (action_required).

The description says none of the eight cassettes relied on the fallthrough. The two converse_stream ones did. The regression is guardrail.py:34, but the stream path depended on the fallthrough because packages/opentelemetry-instrumentation-bedrock/opentelemetry/instrumentation/bedrock/__init__.py:798 and :886 pass only event["metadata"] (read). In both cassettes that frame has no stopReason or amazon-bedrock-guardrailAction; stopReason is on messageStop. Called on the metadata frame, guardrail_converse gives 0 here, 1 on main, and 1 here once stopReason is added. Main also counted a stream whose metadata had no guardrail trace.

Fix: carry stopReason from messageStop to the metadata event (a per-event local today; nonlocal or span_state works) and pass it in. That restores activation for both stream cassettes. Happy to push it with a stream test, or leave it to you.

[linhongyu510]

This correctly fixes the false-positive activation. One thing worth folding in while you're here: issue #4471 also reports a second, related crash that this PR doesn't cover yet.

When metrics are disabled (TRACELOOP_METRICS_ENABLED=false), _instrument() sets guardrail_activation (and the other counters) to None, but both call sites dereference it unconditionally on a genuine activation:

# guardrail.py, guardrail_converse (~L179) and guardrail_handling (~L208)
if is_guardrail_activated(response):
    metric_params.guardrail_activation.add(1, attrs)   # AttributeError: 'NoneType' ...
    set_guardrail_attributes(span, input_filters, output_filters)

Reproducible offline:

mp = MagicMock(); mp.guardrail_activation = None
guardrail_converse(span, {"stopReason": "guardrail_intervened"}, "aws", "m", mp)
# -> AttributeError: 'NoneType' object has no attribute 'add'

A minimal guard at both sites (keeping set_guardrail_attributes unconditional, since span attributes are independent of the metrics toggle) closes it:

if metric_params.guardrail_activation is not None:
    metric_params.guardrail_activation.add(1, attrs)

I had a separate PR (#4487) covering both halves, but yours predates it on the activation fix, so I'm closing mine in favour of this one — just flagging the second half so #4471 can be fully closed here.

[Santoshkumarpuppala]

Re-checked at e1c8586: ee81454 fixes the converse_stream regression from my earlier comment. test_guardrail_converse_stream passes again, and so do the new sync and async stream tests in test_guardrail_activation.py.

Ran locally (Python 3.10): pytest tests in the bedrock package gives 388 passed. As a control, the same tree with only __init__.py taken from 6becfb6 gives 3 failed, 385 passed: test_guardrail_converse_stream (the same KeyError on gen_ai.bedrock.guardrail.input_filter, test_guardrails.py:299) and the guardrail_intervened case of both new stream tests. So the new tests catch it if the carry is ever dropped. CI is still action_required (run 36125545457), so the test suite hasn't run on GitHub yet.

One leftover: the description still says all eight cassettes signal activation explicitly, "so none of them relied on the fallthrough". The two converse_stream ones did: their metadata frames carry neither stopReason nor amazon-bedrock-guardrailAction, which is why __init__.py:805 and :898 now carry stopReason into the metadata call at :799 and :890. Worth a one-line edit so the description matches the diff. I didn't look closely at the metrics-disabled change in e1c8586 beyond the test run.