Greptile Summary

This PR implements two December 2025 Threads API updates:

December 16, 2025 Changes:

• Added is_verified and profile_picture_url fields to the Post struct
• Updated PostExtendedFields and ReplyFields constants to include the new fields
• These fields are available for replies and mentions (for conversations, only on direct replies)

December 22, 2025 Changes:

• Added ErrCodeLinkLimitExceeded constant for the THREADS_API__LINK_LIMIT_EXCEEDED error code
• Added comprehensive integration tests for link count validation scenarios

The changes properly integrate with the existing link validation logic in validation.go (which already enforces the 5-link limit). The new error code constant provides better error handling when the API rejects posts exceeding the link limit.

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• All changes are straightforward API updates that align with the Threads API changelog. The new Post fields are properly documented with clear availability constraints, the constants are correctly formatted and well-documented, and the integration tests comprehensively cover the link validation scenarios including edge cases (duplicate link attachments). The changes integrate cleanly with existing validation logic without requiring modifications.
• No files require special attention

Important Files Changed

Sequence Diagram

sequenceDiagram
    participant Client
    participant ThreadsAPI
    participant Validator
    participant PostStruct

    Note over Client,PostStruct: December 16, 2025 Update: New Post Fields
    
    Client->>ThreadsAPI: Request Post/Reply/Mention
    ThreadsAPI-->>PostStruct: Return Post with is_verified & profile_picture_url
    Note over PostStruct: Fields available for replies/mentions<br/>(conversations: direct replies only)
    
    Note over Client,PostStruct: December 22, 2025 Update: Link Limit Validation
    
    Client->>Validator: CreateTextPost(content with links)
    Validator->>Validator: ValidateLinkCount(text, linkAttachment)
    alt > 5 unique links
        Validator-->>Client: ValidationError
        Note over Client: Too many links error
    else <= 5 unique links
        Validator->>ThreadsAPI: POST /{threads-user-id}/threads
        alt API validation fails
            ThreadsAPI-->>Client: THREADS_API__LINK_LIMIT_EXCEEDED
        else Success
            ThreadsAPI-->>Client: Post created successfully
        end
    end

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