feat: keep prompts only in s3 bucket aws

[Harshit28j]

Relevant issues

LIT-1899

Pre-Submission checklist

• I have Added testing in the tests/litellm/ directory, Adding at least 1 test is a hard requirement
• My PR passes all unit tests on make test-unit
• My PR's scope is as isolated as possible, it only solves 1 specific problem

CI (LiteLLM team)

• Branch creation CI run
  Link:

• CI run for the last commit
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• Merge / cherry-pick CI run
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Type

🆕 New Feature
✅ Test

Changes

• Add s3_log_prompts_only behavior to store only prompt messages (no response/metadata) in S3 logs.
• Add regression tests for prompts-only payloads in both s3_v2 and legacy s3 loggers.

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Project	Deployment	Actions	Updated (UTC)
litellm	Ready	Preview, Comment	Feb 10, 2026 4:34pm

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Greptile Overview

Greptile Summary

This PR adds an s3_log_prompts_only option to both the legacy litellm/integrations/s3.py logger and the newer litellm/integrations/s3_v2.py batch logger. When enabled, the payload written to S3 is reduced to just { "messages": [...] }, omitting the response and other metadata.

The feature is exercised by new/updated tests: a new legacy S3 test that asserts only prompt messages are uploaded, and a new s3_v2 test that asserts create_s3_batch_logging_element() produces the prompts-only payload.

Main issue to address before merge: in the legacy S3Logger, the new flag is only read from litellm.s3_callback_params and is forced to False otherwise, so passing s3_log_prompts_only=True directly to the constructor has no effect (unlike s3_v2, which supports the constructor arg).

Confidence Score: 4/5

• Mostly safe to merge, but fix the legacy S3Logger flag wiring first.
• Changes are localized and covered by tests for both s3 implementations. The main correctness gap is that the legacy S3Logger ignores s3_log_prompts_only when passed as a constructor argument, which will surprise direct instantiations and makes behavior inconsistent across s3 vs s3_v2.
• litellm/integrations/s3.py

Important Files Changed

Filename	Overview
litellm/integrations/s3.py	Adds s3_log_prompts_only flag and strips S3 payload down to messages when enabled; however the flag is only read from litellm.s3_callback_params and is ignored for direct constructor usage.
litellm/integrations/s3_v2.py	Plumbs s3_log_prompts_only through init params and create_s3_batch_logging_element() to log only messages to S3; also refactors s3_verify/s3_use_ssl param handling and minor formatting.
tests/test_litellm/integrations/test_s3.py	New unit test verifies legacy s3 logger writes only {messages: ...} to S3 when s3_log_prompts_only is enabled via litellm.s3_callback_params.
tests/test_litellm/integrations/test_s3_v2.py	Adds prompts-only payload test for s3_v2 logger and various formatting tweaks; existing tests still rely on patching asyncio.create_task to avoid background flush tasks.

Sequence Diagram

sequenceDiagram
    participant App as LiteLLM
    participant S3 as S3Logger (legacy)
    participant S3v2 as S3Logger (v2)
    participant AWS as S3-compatible endpoint

    App->>S3: log_event(kwargs, start_time, end_time)
    S3->>S3: read litellm.s3_callback_params
    alt s3_log_prompts_only enabled
        S3->>S3: payload_dict = {messages}
    else disabled
        S3->>S3: payload_dict = full StandardLoggingPayload
    end
    S3->>AWS: put_object(Body=safe_dumps(payload_dict))

    App->>S3v2: async_log_success_event(kwargs, start_time, end_time)
    S3v2->>S3v2: _init_s3_params() (reads callback params + ctor args)
    S3v2->>S3v2: create_s3_batch_logging_element()
    alt s3_log_prompts_only enabled
        S3v2->>S3v2: element.payload = {messages}
    else disabled
        S3v2->>S3v2: element.payload = full StandardLoggingPayload
    end
    S3v2->>S3v2: queue element for batch flush
    S3v2->>AWS: PUT signed request (async_upload_data_to_s3)

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Additional Comments (1)

litellm/integrations/s3.py
Flag ignored for direct init

S3Logger.__init__() only reads s3_log_prompts_only from litellm.s3_callback_params and forces it to False otherwise, so passing S3Logger(s3_log_prompts_only=True) has no effect. This makes the new behavior unusable for callers who construct the logger directly (and is inconsistent with s3_v2.S3Logger, which supports the constructor arg). Consider wiring the kwarg through (or at least not overriding it to False) so the flag works outside global config.