Greptile Summary

This PR fixes a correctness bug where system and developer role messages inside the Responses API input array were silently dropped for Anthropic, Bedrock, and Vertex providers. They are now folded into each provider's native system prompt field, matching what OpenAI already does. A shared convert_utils module eliminates the per-provider duplication of text-extraction helpers.

• Core fix (3 providers): convert_responses_input_to_messages / _bedrock_messages / _vertex now accumulate system/developer message text into system_parts and merge it with the top-level instructions via join_system_parts* helpers, instead of continue-ing and losing the content entirely.
• New shared module: src/providers/convert_utils.rs exports easy_content_text and input_content_text, replacing what would have been three sets of duplicate helpers.
• Azure OpenAI unrelated fix: strip_gateway_fields() is now called in the Azure adapter, mirroring the existing OpenAI adapter path to prevent internal gateway fields from leaking to the upstream endpoint.

Confidence Score: 5/5

Safe to merge — the change is a straightforward correctness fix that promotes previously-dropped content into the system prompt, all three provider paths are symmetric and unit-tested.

All three provider converters follow the same well-tested pattern. The text-extraction helpers in convert_utils are simple and correct. No existing behavior is removed — only silent data loss is eliminated. The Azure strip_gateway_fields addition mirrors an already-proven pattern from the OpenAI adapter.

No files require special attention.

Important Files Changed

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["convert_responses_input_to_messages(input, instructions)"] --> B["Seed system_parts with instructions"]
    B --> C{input present?}
    C -- No --> Z["join_system_parts(system_parts)"]
    C -- Yes --> D{input variant}
    D -- Text --> E["Push single user message"] --> Z
    D -- Items --> F["Iterate items"]
    F --> G{item type}
    G -- "EasyMessage(System|Developer)" --> H["easy_content_text()"] --> I["Push to system_parts"] --> F
    G -- "MessageItem(System|Developer)" --> J["input_content_text()"] --> K["Push to system_parts"] --> F
    G -- "EasyMessage(User|Assistant)" --> L["Push to messages list"] --> F
    G -- "MessageItem(User)" --> M["Push to messages list"] --> F
    G -- other --> F
    Z --> N["Return (Option<SystemPrompt>, Vec<Message>)"]
    E --> N

    subgraph "convert_utils.rs"
        H
        J
    end

_{Reviews (4): Last reviewed commit: "Merge branch 'main' into fix/native-syst..." | Re-trigger Greptile}

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