## Thinking Path
> - Paperclip is the open source app people use to manage AI agents for
work
> - The adapter utilities provide sandbox transport paths for agent
execution
> - The retired `duplex_v1` path remains in host, gateway, and test code
after `http2_v1` replaced it
> - Retired transport code adds maintenance cost and leaves an unsafe
fallback for unknown gateway modes
> - This pull request removes the retired path, moves shared `http2_v1`
contracts to a leaf module, and closes mode dispatch to a fixed
allowlist
> - The benefit is a smaller transport surface and explicit failure for
unsupported modes
## Linked Issues or Issue Description
Refs #12120
The `http2_v1` transport replaced `duplex_v1`, but the retired broker,
gateway, constants, and tests remain in the adapter utilities. An
unknown bridge mode can also fall through to the queue gateway when a
queue directory exists. This change removes the retired code and rejects
unsupported modes before gateway selection.
## What Changed
- Delete the host `duplex_v1` broker and its transport-only tests.
- Delete the in-sandbox duplex gateway and retired mode constants.
- Move shared `http2_v1` symbols into `bridge-transport-contract.ts`.
- Update the remaining importers and repair their focused tests.
- Validate bridge modes against `http2_v1` and `queue_v1` before queue
lookup.
- Keep `queue_v1`, `duplex-frame-codec.ts`, and duplex telemetry
dimensions unchanged.
## Verification
- [x] `npx tsc --noEmit -p packages/adapter-utils` passes.
- [x] `npx vitest run packages/adapter-utils/src` passes: 48 files and
968 tests pass, with 4 pre-existing platform skips.
- [x] Full CI is green on this pull request.
- [x] Greptile review is complete and every finding is resolved.
## Risks
The change removes an internal transport that no host path selects. The
main risk is an overlooked import or test dependency. Targeted typecheck
and tests cover the adapter utility package. Full CI must confirm
workspace-wide compatibility.
## Model Used
Anthropic Claude Sonnet 5 assisted with the implementation, as recorded
in the commit. The commit does not record a context-window size or
reasoning mode.
## 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 searched GitHub for duplicate or related PRs and linked
them above
- [x] I have either (a) linked existing issues with `Fixes: #` / `Closes
#` / `Refs #` OR (b) described the issue in-PR following the relevant
issue template
- [x] I have not referenced internal/instance-local Paperclip issues or
links (only public GitHub `#NNN` / `github.com/paperclipai/paperclip`
URLs)
- [x] My branch name describes the change (e.g. `docs/...`, `fix/...`)
and contains no internal Paperclip ticket id or instance-derived details
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] All Paperclip CI gates are green
- [x] Greptile is 5/5 with no open P2s, recommendations, or follow-ups
- [x] I will address all Greptile and reviewer comments before
requesting merge
Co-authored-by: Paperclip <noreply@paperclip.ing>
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