## Thinking Path
> - Paperclip is the open source app people use to manage AI agents for
work
> - Adapter utilities transfer files between the host and an agent
environment
> - A sandbox target already provides the security boundary for inbound
files
> - The generic fallback adds a temporary file and a rename that do not
add protection inside that boundary
> - This pull request writes a mode-constrained inbound file directly to
its target and applies the mode after the write
> - The benefit is a simpler transfer path while host targets keep the
strict pre-write mode rule
## Linked Issues or Issue Description
**What existing behavior does this improve?**
The inbound file-sync fallback for a mode-constrained file stages the
file under a temporary name, applies the mode, and renames the file into
place.
**Subsystem affected**
`packages/adapter-utils` and `packages/plugins`.
**Current behavior**
A sandbox target uses a temporary path before it receives the file. The
host then changes the mode and renames the file to the target path.
**Proposed behavior**
A sandbox target receives the file at its target path. The host applies
the mode after the write. A host target still applies the mode before
the first byte.
**Reason and benefit**
The sandbox boundary already protects the target. The direct write
removes an unnecessary staging path and rename.
**Breaking changes**
None. The directory path and outbound transfer path keep their existing
behavior.
## What Changed
- Write a mode-constrained single-file inbound transfer directly to the
sandbox target.
- Apply the mode after the direct write and keep the confinement check
before post-upload commands.
- Scope the protocol comment by transfer direction and preserve the
strict host-target rule.
- Keep directory inbound transfers and outbound transfers unchanged.
## Verification
- Run the targeted unit suite for the changed package.
- Verify the suite covers direct target writes, post-write mode
application, and confinement rejection.
- Run `tsc --noEmit` for both changed packages.
- Review the full GitHub Actions check set after the PR opens.
## Risks
- A sandbox provider that assumes a temporary inbound path could expose
a behavior mismatch.
- The confinement check remains before post-upload commands, which
limits escape risk.
- Host targets keep the pre-write mode rule, so host permission behavior
does not change.
## Model Used
OpenAI GPT-5. This model assisted with Git operations, PR preparation,
review coordination, and tool use. Context window size and reasoning
mode are not exposed by the runtime.
## 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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