## Thinking Path
> - Paperclip is a control plane for AI-agent companies.
> - External adapters can provide UI parser code that the board loads
dynamically for run transcript rendering.
> - Running adapter-provided parser code directly in the board page
gives that parser access to same-origin browser state.
> - This PR narrows that surface by evaluating dynamically loaded
external adapter UI parser code in a dedicated browser Web Worker with a
constrained postMessage protocol.
> - The worker here is a frontend isolation boundary for adapter UI
parser JavaScript; it is not Paperclip's server plugin-worker system and
it is not a server-side job runner.
## What Changed
- Runs dynamically loaded external adapter UI parsers inside a dedicated
Web Worker instead of importing/evaluating them directly in the board
page.
- Adds a narrow postMessage protocol for parser initialization and line
parsing.
- Caches completed async parse results and notifies the adapter registry
so transcript recomputation can synchronously drain the final parsed
line.
- Disables common worker network, persistence, child worker, Blob/object
URL, and WebRTC escape APIs inside the parser worker bootstrap.
- Handles worker error messages after initialization and drains pending
callbacks on worker termination or mid-session worker error.
- Adds focused regression coverage for the parser worker lockdown and
unused protocol removal.
## Verification
- `pnpm exec vitest run --config ui/vitest.config.ts
ui/src/adapters/sandboxed-parser-worker.test.ts`
- `pnpm exec tsc --noEmit --target es2021 --moduleResolution bundler
--module esnext --jsx react-jsx --lib dom,es2021 --skipLibCheck
ui/src/adapters/dynamic-loader.ts
ui/src/adapters/sandboxed-parser-worker.ts
ui/src/adapters/sandboxed-parser-worker.test.ts`
- `pnpm --filter @paperclipai/ui typecheck` was attempted; it reached
existing unrelated failures in HeartbeatRun test/storybook fixtures and
missing Storybook type resolution, with no adapter-module errors
surfaced.
- PR #4225 checks on current head `34c9da00`: `policy`, `e2e`, `verify`,
`security/snyk`, and `Greptile Review` are all `SUCCESS`.
- Greptile Review on current head `34c9da00` reached 5/5.
## Risks
- Medium risk: parser execution is now asynchronous through a worker
while the existing parser interface is synchronous, so transcript
updates should be watched with external adapters.
- Some adapter parser bundles may rely on direct ESM `export` syntax or
browser APIs that are no longer available inside the worker lockdown.
- The worker lockdown is a hardening layer around external parser code,
not a complete browser security sandbox for arbitrary untrusted
applications.
> For core feature work, check [`ROADMAP.md`](ROADMAP.md) first and
discuss it in `#dev` before opening the PR. Feature PRs that overlap
with planned core work may need to be redirected — check the roadmap
first. See `CONTRIBUTING.md`.
## Model Used
- OpenAI Codex, GPT-5-based coding agent runtime, shell/git tool use
enabled. Exact hosted model build and context window are not exposed in
this Paperclip heartbeat environment.
## 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
- [x] 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
- Plugin loader: install/reload/remove/reinstall external adapters
from npm packages or local directories
- Plugin store persisted at ~/.paperclip/adapter-plugins.json
- Self-healing UI parser resolution with version caching
- UI: Adapter Manager page, dynamic loader, display registry
with humanized names for unknown adapter types
- Dev watch: exclude adapter-plugins dir from tsx watcher
to prevent mid-request server restarts during reinstall
- All consumer fallbacks use getAdapterLabel() for consistent display
- AdapterTypeDropdown uses controlled open state for proper close behavior
- Remove hermes-local from built-in UI (externalized to plugin)
- Add docs for external adapters and UI parser contract
