fix(kb): force kb uploads to use serve route

[waleedlatif1]

Summary

force kb uploads to use serve route instead of direct uploads/GETs since those caused sporadic failures with forbidden errors

Type of Change

• Bug fix

Testing

Tested manually.

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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Project	Deployment	Preview	Comments	Updated (UTC)
sim	Ready	Preview	Comment	Oct 6, 2025 0:50am

1 Skipped Deployment

Project	Deployment	Preview	Comments	Updated (UTC)
docs	Skipped			Oct 6, 2025 0:50am

[greptile-apps]

Greptile Overview

Summary

This PR fixes sporadic forbidden errors for knowledge base file uploads by modifying the file serving logic in the presigned URL route. The change removes 'knowledge-base' from the condition that determines whether files should use direct S3 URLs or go through the application's serve route.

Previously, knowledge base files were served using direct S3 URLs (https://{bucket}.s3.{region}.amazonaws.com/{key}), which could fail with forbidden errors due to restrictive bucket policies or IAM permissions. Now, knowledge base files will use the /api/files/serve/s3/ endpoint instead, which provides proper authentication and authorization handling.

This change aligns knowledge base file serving with how other file types (except chat and profile pictures) are handled in the system. The serve route, as documented in the codebase context, implements robust error handling, logging, and supports both local and cloud storage with proper access controls. By routing knowledge base files through this endpoint, the application ensures consistent file access regardless of external S3 configuration issues.

Changed Files

Filename	Score	Overview
apps/sim/app/api/files/presigned/route.ts	4/5	Removed 'knowledge-base' from direct S3 URL condition, forcing KB files through serve route

Confidence score: 4/5

• This PR is safe to merge with minimal risk as it addresses a specific access issue without breaking existing functionality
• Score reflects a targeted fix that improves reliability by using established serve route infrastructure for knowledge base files
• No files require special attention beyond the single modified route handler

Sequence Diagram

sequenceDiagram
    participant User
    participant API as "/api/files/presigned"
    participant Auth as "Auth Service"
    participant Validation as "Validation Layer"
    participant Storage as "Storage Service"
    participant S3 as "AWS S3"
    participant Blob as "Azure Blob"

    User->>API: "POST /api/files/presigned"
    API->>Auth: "getSession()"
    Auth-->>API: "session data"
    
    alt User not authenticated
        API-->>User: "401 Unauthorized"
    else User authenticated
        API->>API: "Parse request JSON"
        
        alt Invalid JSON
            API-->>User: "400 ValidationError"
        else Valid JSON
            API->>Validation: "validateFileType(fileName, contentType, fileSize)"
            Validation-->>API: "validation result"
            
            alt Validation fails
                API-->>User: "400 ValidationError"
            else Validation passes
                API->>Storage: "getStorageProvider()"
                Storage-->>API: "storage provider type"
                
                alt Storage provider is S3
                    API->>S3: "handleS3PresignedUrl()"
                    S3->>S3: "Generate presigned URL"
                    S3-->>API: "presigned URL + file info"
                    API-->>User: "200 OK with presigned URL"
                else Storage provider is Blob
                    API->>Blob: "handleBlobPresignedUrl()"
                    Blob->>Blob: "Generate SAS token"
                    Blob-->>API: "presigned URL + file info"
                    API-->>User: "200 OK with presigned URL"
                else Unknown provider
                    API-->>User: "500 StorageConfigError"
                end
            end
        end
    end

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