## Thinking Path
> - Paperclip orchestrates AI agents for zero-human companies
> - Agents can run inside sandboxed environments like E2B, which are
isolated from the host network
> - Sandboxed agents need to call back to the Paperclip API to report
progress, post comments, and update issue status
> - But sandbox environments cannot reach the Paperclip server directly
because they run in isolated network namespaces
> - This PR adds a callback bridge that proxies API requests from the
sandbox to the Paperclip server, running as a local HTTP server on the
host that forwards authenticated requests
> - The bridge is started automatically when an adapter launches a
sandbox execution, and torn down when the run completes
> - The benefit is sandboxed agents can interact with the Paperclip API
without requiring network-level access to the host, enabling E2B and
similar providers to work end-to-end
## What Changed
- Added `sandbox-callback-bridge.ts` in `packages/adapter-utils/` — a
lightweight HTTP bridge server that accepts requests from sandbox
environments and proxies them to the Paperclip API with authentication
- Added request validation and security policy: the bridge only forwards
requests to the configured API URL, validates content types, enforces
size limits, and rejects non-API paths
- Wired the bridge into all remote adapter execute paths (claude, codex,
cursor, gemini, pi) — the bridge starts before the agent process and the
bridge URL is passed via environment variables
- Updated `environment-execution-target.ts` to prefer the explicit API
URL from environment lease metadata for sandbox callback routing
- Fixed Claude sandbox runtime setup to work with the bridge
configuration
- Added comprehensive test coverage for bridge request handling, policy
enforcement, and sandbox execution integration
- Fixed browser bundling — the bridge module is excluded from the
frontend bundle via the adapter-utils index export
## Verification
- `pnpm test` — all existing and new tests pass, including bridge unit
tests and sandbox execution integration tests
- `pnpm typecheck` — clean
- Manual: configure an E2B environment, run an agent task, verify the
agent can post comments and update issue status through the bridge
## Risks
- Medium. This is a new network-facing component (HTTP server on
localhost). The security policy restricts forwarding to the configured
API URL only and validates all requests, but any proxy introduces attack
surface. The bridge binds to localhost only and is scoped to the
lifetime of a single agent run.
## Model Used
Codex GPT 5.4 high via Paperclip.
## Checklist
- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [ ] If this change affects the UI, I have included before/after
screenshots
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge
Devin Foley
a4ac6ff133