## Thinking Path
> - Paperclip is the open source app people use to manage AI agents for
work
> - Sandbox providers (Daytona, Kubernetes) sync run results back to the
host with a sandbox-authored tarball
> - Before extraction, a confinement check parses the host `tar -tvf`
listing and fails closed on unparseable lines
> - The parser only understands the GNU tar listing dialect; macOS ships
bsdtar, whose ls-style listing never matches
> - Every sandbox syncOut on a macOS host therefore aborts with
"refusing tarball with an unparseable entry listing", and the run fails
at copy-back
> - This pull request teaches the parser both dialects while keeping the
fail-closed and traversal guarantees
> - The benefit is that Daytona and Kubernetes sandbox runs work on
macOS hosts, with no behavior change on Linux
## Linked Issues or Issue Description
No existing issue. Bug description:
**What happened?**
On a macOS host, every Daytona sandbox run fails at syncOut. The adapter
reports: `Daytona syncOut refusing tarball with an unparseable entry
listing: -rw-r--r-- 0 daytona daytona 7560 Aug 11 21:43 AGENTS.md`. The
Kubernetes provider has the same parser and fails the same way.
**Expected behavior**
The confinement check accepts a well-formed listing from the host tar,
whichever dialect the host tar emits. It still rejects members that
escape the extraction directory, and it still fails closed on lines it
cannot parse.
**Steps to reproduce**
1. Run Paperclip on macOS (system tar is bsdtar).
2. Configure an agent with the Daytona sandbox provider.
3. Trigger any run that syncs files back from the sandbox.
4. The run fails at syncOut with the unparseable-entry-listing error,
because bsdtar prints `<perms> <links> <user> <group> <size> <Mon> <day>
<time|year> <name>` while the parser expects the GNU `<perms>
<owner>/<group> <size> <date> <time> <name>` shape.
**Operating system**
macOS (bsdtar 3.5.3). Linux hosts with GNU tar are unaffected.
## What Changed
- Extracted the listing-line parse in both providers' `file-sync.ts`
into an exported `parseTarVerboseListingLine` that accepts the
GNU/busybox dialect and the bsdtar (libarchive) dialect.
- The GNU shape now requires the slash-joined `<owner>/<group>` field.
This keeps the two shapes mutually exclusive. Without it, a bsdtar line
with numeric uid/gid satisfies the loose GNU pattern shifted by one
field, which would hide a leading `../` from the traversal check.
- Unparseable lines still fail closed. This includes device-node
entries, whose size column is `major,minor` in both dialects.
- Made the path-traversal fixture in the Daytona suite portable: GNU
spells member renaming `--transform`, bsdtar spells it `-s`.
- Added a Daytona test that refuses a sandbox-authored tarball carrying
a symlink whose target escapes the extraction dir.
- Added parser unit tests for both dialects (file, dir, symlink,
hardlink, numeric owner, year-form dates, fail-closed lines) to both
providers' suites.
## Verification
- `pnpm test` in `packages/plugins/sandbox-providers/daytona`: 136/136
pass on a macOS host. On unpatched `master` the round-trip test fails
there with the unparseable-entry-listing error.
- `pnpm test` in `packages/plugins/sandbox-providers/kubernetes`: the
new parser tests pass; no new failures against the `master` baseline on
the same host.
- `pnpm typecheck` passes in both packages.
- CI runs the same suites on Linux/GNU tar and proves the GNU path is
unchanged.
## Risks
- Low risk. The GNU pattern is one token stricter (`<owner>/<group>`
must contain `/`). GNU and busybox tar always print the slash-joined
owner field, so accepted GNU listings are unchanged.
- The bsdtar branch only widens acceptance on hosts that were failing
100% of syncOuts before, so no working deployment changes behavior.
- The check still fails closed on anything neither pattern matches.
## Model Used
Claude Fable 5 (`claude-fable-5`, Claude Code CLI, extended thinking +
tool use).
## 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
- [ ] All Paperclip CI gates are green
- [ ] Greptile is 5/5 with no open P2s, recommendations, or follow-ups
- [x] I will address all Greptile and reviewer comments before
requesting merge
## Thinking Path
> - Paperclip is the control plane for autonomous AI companies, so
runtime handoffs have to preserve the exact behavior an agent asked for.
> - The sandbox-provider layer is where uploaded files and follow-up
commands become a real in-sandbox operation.
> - The provider-delegable sync-in seam already exists from the prior
PR; without this follow-up, native providers can still accept
command-bearing uploads and silently drop the commands.
> - That is a fail-open gap for native sandbox providers, because the
file transfer succeeds while the intended post-upload work never runs.
> - This pull request teaches Daytona and Kubernetes to execute
`postUploadCommands` in order, inside the sandbox, after the files land.
> - The benefit is consistent and safer sync semantics: native providers
either run the commands as requested or fail fast instead of pretending
the operation completed fully.
## Linked Issues or Issue Description
This PR builds on the previously merged provider-delegable sync-in seam
and closes the remaining gap for native providers that still dropped
`postUploadCommands`.
Problem:
- A sync operation could include ordered `postUploadCommands`, but a
native provider could finish the file upload and skip the commands
entirely.
- That creates fail-open behavior for command-bearing uploads,
especially when the caller relies on the provider to execute the
follow-up action in the sandbox.
Proposed fix:
- Execute `postUploadCommands` inside the sandbox after file placement.
- Preserve the provided command order.
- Fail fast on the first non-zero exit or timeout.
- Keep command execution verbatim and confine any provided `cwd` under
the workspace root.
Related public PR:
- Refs: #10340
## What Changed
- Daytona `performSyncIn` now executes ordered `postUploadCommands`
through the existing `executeCommand` seam.
- Kubernetes `performSyncIn` now executes ordered `postUploadCommands`
through its streaming pod exec path.
- Added workspace confinement for provided `cwd` values and defaulted
missing `cwd` to the remote root.
- Added tests covering the new post-upload command execution behavior in
both provider packages.
## Verification
- Latest validation recorded on the handoff branch:
`@paperclipai/plugin-sdk` and `@paperclipai/plugin-kubernetes`
typechecks passed.
- Daytona Vitest: `63/63` passing in `plugin.test.ts`.
- Kubernetes Vitest: `195/195` passing, including `file-sync.test.ts`.
- `git log --oneline origin/master..HEAD` showed a single expected
commit on the branch.
## Risks
- Command execution semantics are stricter now, so malformed commands or
a bad `cwd` will fail the sync instead of being ignored.
- The change makes provider behavior more explicit, which can surface
previously hidden failures in callers that assumed commands were
optional.
- Timeout behavior may differ slightly between providers, so the failure
mode is intentionally fail-fast.
## Model Used
OpenAI Codex, GPT-5-based coding agent with tool use enabled.
## 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>
## Thinking Path
> - Paperclip is the open source app people use to manage AI agents for
work
> - AI agents run in sandboxed execution environments (Kubernetes pods,
Daytona workspaces, etc.) and need to sync files between the host and
those environments — for workspace setup, asset delivery, and output
retrieval
> - The existing sync path for Kubernetes uses a base64-over-exec chunk
loop: each ~4 MB chunk requires its own `execInPod` round-trip, so large
syncs balloon into many exec calls with corresponding overhead
> - `execInPod` supports piped stdin/stdout, meaning the full transfer
can be done as a single exec that streams a raw `tar` archive over the
data channel — one round-trip regardless of file size, with nothing
base64-encoded and nothing buffered whole in memory on either side
> - PR-1 (#10013, merged) added the
`onEnvironmentSyncIn`/`onEnvironmentSyncOut` opt-in hook API to the
sandbox provider interface and documented the protocol; PR-2 (#10028,
merged) implemented these hooks for the Daytona provider
> - This pull request implements the same two lifecycle hooks in the
Kubernetes sandbox provider, so workspace/asset file sync streams
through one `execInPod` per operation instead of the chunk loop
> - The benefit is significantly fewer exec round-trips for large syncs
and flat memory use on both host and pod, with security properties
preserved: atomic replace, secret-mode enforcement, path confinement,
TOCTOU-safe snapshot, and member-confinement on host-assembled archives
from sandbox-authored tar output
## Linked Issues or Issue Description
This is the third and final PR in a sequential series:
- Refs #10013 — PR-1: opt-in sync hook API + provider docs (merged)
- Refs #10028 — PR-2: native file-sync lifecycle hooks for Daytona
provider (merged)
**Feature:** Native single-exec file-sync lifecycle hooks for the
Kubernetes sandbox provider.
*Motivation:* The existing Kubernetes sync path encodes files as base64
and loops over `execInPod` one chunk at a time (~4 MB per exec). For
large workspaces or asset sets this is slow and resource-intensive. The
Kubernetes `execInPod` API supports piped stdin/stdout, enabling a
raw-`tar` streaming transfer that needs only one exec regardless of file
count or size and never buffers the whole payload in memory.
*Proposed solution:* Implement `onEnvironmentSyncIn` and
`onEnvironmentSyncOut` in the Kubernetes provider using a streaming
`execInPod` with a tar pipeline — for syncIn the host builds the archive
on disk and streams its raw bytes into the pod's stdin (`head -c
<exact-size> | tar -x`, no base64); for syncOut in-pod `tar` writes to
the exec's stdout and the host streams those bytes straight to a file.
Path confinement, atomic replace, secret-mode enforcement, TOCTOU
protection, and a streamed-bytes fail-closed guard are all enforced.
## What Changed
- **New `src/file-sync.ts`** in
`packages/plugins/sandbox-providers/kubernetes/` — `performSyncIn` and
`performSyncOut` over an injected pod-exec closure, keeping transfer
logic hermetically unit-testable
- **New `execInPodStreaming` in `src/pod-exec.ts`** — a streaming exec
primitive that binds a caller-supplied stdin readable and a stdout
writable to the exec WebSocket data channel, added alongside the
existing `execInPod` (which is unchanged). This lets a transfer stream
raw bytes to/from disk instead of buffering the payload as a single
string
- **Updated `src/plugin.ts`** — registers
`onEnvironmentSyncIn`/`onEnvironmentSyncOut`; resolves the `sandbox-cr`
pod exactly like `onEnvironmentExecute` and delegates; `job` backend
rejects file-sync calls explicitly (out of scope)
- **syncIn path:** host builds the tarball to a temp file → streams its
raw bytes over exec stdin, bounded in-pod by `head -c
<exact-archive-size> | tar -x` (no base64 anywhere) → extract into a
`/proc/self/fd`-pinned reserved `0700` staging dir → `chmod`-before-`mv
-f` atomic replace per file (directory mappings use
`followSymlinks`→`-h`)
- **syncOut path:** in-pod validate + realpath-snapshot each source
(closes the validation→copy TOCTOU window) → single-exec `tar -c`
streamed over exec stdout → host streams that stdout straight to a temp
file through a byte-counting transform → member-confined extraction of
the sandbox-authored archive
- **Security properties:** secret files land at requested mode with no
widened window; every interpolated path is shell-quoted and confined
lexically plus via in-pod `realpath`; the outbound stream is bounded by
a **streamed-bytes disk guard** (`MAX_SYNC_OUTPUT_BYTES`, 8 GiB default,
per-call overridable) that fails the transfer closed — writing no target
file — if an untrusted pod emits more bytes than allowed. Neither host
nor pod buffers the whole payload, so there is no in-memory size cap on
the transfer
- **No changes** to `execInPod`, `wrapCommandWithEnv`, or
`FastUploadInterceptor` (the `environmentExecute` path is untouched)
- **No dependency or lockfile changes**
- **New tests** in `test/unit/file-sync.test.ts` (atomic-replace, `0600`
secret mode, symlink preserve/deref, dir-mapping, exclude,
path-confinement rejection, streamed-output guard fail-closed) and
`test/unit/pod-exec.test.ts` (streaming stdin/stdout, caller-sink error
fail-closed), plus extended `test/unit/plugin.test.ts`
## Follow-up: Legacy Job-Lease Base64 Fallback Fix
Addresses the Greptile 4/5 blocking finding ("Handle existing job
leases", `server/src/services/environment-runtime.ts`).
Job leases provisioned before the `nativeFileSyncUnsupported` metadata
flag existed carry `backend: "job"` but no flag, so `supportsSync()`
treated them as native-capable and routed their sync to the pod-exec
hook — which the job backend rejects (it has no exec channel) instead of
using the byte-identical base64 fallback. The fix adds a
belt-and-suspenders gate on the persisted `backend === "job"` field
alongside the existing `nativeFileSyncUnsupported` flag check, so
pre-existing job leases continue syncing via the base64 fallback after
deployment. No behaviour change for `sandbox-cr` leases.
## Verification
- `pnpm --filter @paperclipai/sandbox-provider-kubernetes test` — 19
files / 182 tests green, including the existing `upload-interceptor` and
`pod-exec` suites
- `tsc --noEmit` in the kubernetes package — 0 errors
- The sync hooks are opt-in; existing `environmentExecute` behaviour is
unaffected and tested by the unchanged existing suites
## Risks
- **Opt-in only:** `onEnvironmentSyncIn`/`onEnvironmentSyncOut` are
registered conditionally; providers that do not register them fall back
to the existing chunk loop. No regression risk on the existing path.
- **Shell-injection surface:** all path interpolation uses
shell-quoting; paths are additionally confined lexically and via in-pod
`realpath` before use.
- **TOCTOU on syncOut:** the in-pod snapshot validates and records file
metadata before the tar call, closing the window between validation and
copy.
- **Archive member confinement:** host-side reassembly rejects any tar
member whose resolved path escapes the target directory, preventing a
malicious in-pod tar from writing outside the intended destination.
- **Untrusted-output volume:** an over-large outbound stream trips the
streamed-bytes disk guard and fails closed (no target written and the
temp sink is swept) rather than filling host disk or memory; the guard
bounds disk unconditionally and bounds memory insofar as WebSocket
write-backpressure holds.
## Model Used
Anthropic Claude Sonnet 4.6 (`claude-sonnet-4-6`) — produced by a
Claude-based AI agent using agentic tool use and multi-step code
generation. 200K context window, extended reasoning, code execution and
verification capabilities.
## 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: Harold Kim <harold@paperclip.ing>
Co-authored-by: Paperclip <noreply@paperclip.ing>
Devin Foley
Nicky Leach