fix(posthog): replace proxy rewrite with route handler for reliable body streaming

[waleedlatif1]

Summary

• Replaced NextResponse.rewrite() PostHog proxy with a dedicated route handler at /ingest/[[...path]]
• Uses fetch() with duplex: 'half' for reliable request body streaming (fixes ECONNRESET errors on large payloads like session recordings)
• Excluded /ingest from proxy matcher to prevent Next.js 16 body buffering interference

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)

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Skipped		Feb 11, 2026 3:49am

[greptile-apps]

Greptile Overview

Greptile Summary

Replaced the PostHog proxy implementation from NextResponse.rewrite() in middleware to a dedicated route handler at /ingest/[[...path]]. The new implementation uses fetch() with duplex: 'half' to properly stream request bodies, which resolves ECONNRESET errors that occurred with large payloads like session recordings. The middleware matcher now excludes /ingest to prevent Next.js 16 from buffering request bodies, which was interfering with the proxy functionality.

Key changes:

• Created new route handler with proper header forwarding (x-forwarded-for for geolocation, strips cookies/connection headers)
• Routes /ingest/static/* to us-assets.i.posthog.com, other paths to us.i.posthog.com
• Includes error handling with structured logging and 502 status on failures
• Removed duplicate PostHog logic from proxy.ts middleware

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• The change is a well-implemented bug fix that moves PostHog proxying to a more appropriate location. The code follows best practices with proper error handling, logging, and header management. The implementation correctly uses duplex: 'half' to enable request body streaming, which is the documented solution for this use case.
• No files require special attention

Important Files Changed

Filename	Overview
apps/sim/app/ingest/[[...path]]/route.ts	New route handler for PostHog proxy using fetch() with duplex: 'half' to reliably stream request bodies and avoid ECONNRESET errors. Well-structured with proper error handling and logging.
apps/sim/proxy.ts	Removed PostHog proxy logic from middleware (previously using NextResponse.rewrite()). Added ingest to exclusion pattern in matcher to prevent middleware from intercepting the new route handler.

Sequence Diagram

sequenceDiagram
    participant Client
    participant NextMiddleware as Next.js Middleware (proxy.ts)
    participant RouteHandler as Route Handler (/ingest/[[...path]])
    participant PostHogAPI as PostHog API (us.i.posthog.com)
    participant PostHogAssets as PostHog Assets (us-assets.i.posthog.com)

    Note over Client,PostHogAssets: Before: Used NextResponse.rewrite() in middleware
    Note over Client,PostHogAssets: After: Dedicated route handler with fetch()

    Client->>NextMiddleware: POST /ingest/... (large payload)
    Note over NextMiddleware: Excluded from matcher<br/>(prevents body buffering)
    NextMiddleware->>RouteHandler: Pass through
    
    alt Static asset request (/ingest/static/*)
        RouteHandler->>PostHogAssets: fetch() with duplex: 'half'
        PostHogAssets-->>RouteHandler: Asset response
    else API request
        RouteHandler->>PostHogAPI: fetch() with duplex: 'half'<br/>(streams body without buffering)
        PostHogAPI-->>RouteHandler: API response
    end
    
    RouteHandler-->>Client: Streamed response

Loading

[greptile-apps]

_{2 files reviewed, no comments}

_{Edit Code Review Agent Settings | Greptile}

[waleedlatif1]

@cursor review

[cursor]

✅ Bugbot reviewed your changes and found no new issues!

Comment @cursor review or bugbot run to trigger another review on this PR