google-genai: instrument_generate_content() unconditionally sets OTEL_INSTRUMENTATION_GENAI_EMIT_EVENT=true, overriding config and user setting

Package

opentelemetry-instrumentation-google-genai 1.0b0 (with opentelemetry-util-genai 1.0b0)

What happens

instrument_generate_content() unconditionally mutates a global process environment variable when instrumenting:

def instrument_generate_content(
    telemetry_handler: TelemetryHandler,
    generate_content_config_key_allowlist: AllowList,
) -> object:
    os.environ["OTEL_INSTRUMENTATION_GENAI_EMIT_EVENT"] = "true"
    ...

This has a few problems:

1. It overrides the documented default behavior. opentelemetry.util.genai.utils.should_emit_event() is documented to default based on OTEL_INSTRUMENTATION_GENAI_CAPTURE_MESSAGE_CONTENT:

   • NO_CONTENT or SPAN_ONLY → events default off
   • EVENT_ONLY or SPAN_AND_EVENT → events default on

   Because instrumenting force-sets OTEL_INSTRUMENTATION_GENAI_EMIT_EVENT=true (which should_emit_event() treats as highest priority), the gen_ai.client.inference.operation.details event is emitted for every request even in NO_CONTENT / SPAN_ONLY mode. In those modes the event carries no message content, so it just duplicates the span's attributes — redundant telemetry the user did not ask for.

2. It overrides an explicit user setting. A user who sets OTEL_INSTRUMENTATION_GENAI_EMIT_EVENT=false to disable the event has their choice silently overwritten by instrument().

3. It mutates global process state as a side effect of instrumenting. Writing to os.environ affects the whole process (and any other GenAI instrumentation reading the same variable), is order-dependent, and is not thread-safe.

Minimal reproduction

import os

os.environ["OTEL_INSTRUMENTATION_GENAI_CAPTURE_MESSAGE_CONTENT"] = "SPAN_ONLY"
os.environ["OTEL_INSTRUMENTATION_GENAI_EMIT_EVENT"] = "false"  # explicitly disable the event

from opentelemetry.instrumentation.google_genai import GoogleGenAiSdkInstrumentor

GoogleGenAiSdkInstrumentor().instrument()

print(os.environ["OTEL_INSTRUMENTATION_GENAI_EMIT_EVENT"])
# -> "true"   (the user's "false" was overwritten)

After this, a generate_content call emits a gen_ai.client.inference.operation.details event even though the user asked for SPAN_ONLY capture and explicitly set EMIT_EVENT=false.

Expected

instrument() should not write to os.environ. Whether the event is emitted should be decided by should_emit_event() from the (unmodified) configuration:

• default off for NO_CONTENT / SPAN_ONLY,
• default on for EVENT_ONLY / SPAN_AND_EVENT,
• and an explicit OTEL_INSTRUMENTATION_GENAI_EMIT_EVENT from the user always respected.

If there is a reason the event must be emitted regardless of capture mode, it would be clearer to pass that intent into the TelemetryHandler / invocation directly rather than mutating a global environment variable.

Context

Found while integrating this instrumentation into Pydantic Logfire. As a downstream workaround we snapshot OTEL_INSTRUMENTATION_GENAI_EMIT_EVENT before calling instrument() and restore it afterwards, but that only works because should_emit_event() reads the variable per request rather than at instrument time.

Start in instrumentation/opentelemetry-instrumentation-google-genai/src/opentelemetry/instrumentation/google_genai/generate_content.py at instrument_generate_content(), then trace how should_emit_event() reads configuration. Run the existing Google GenAI instrumentation tests and add coverage for explicit false and SPAN_ONLY or NO_CONTENT settings. Done means instrument() leaves os.environ unchanged and event emission follows the documented configuration.