## Thinking Path
> - Paperclip is the open source app people use to manage AI agents for
work
> - The previous pull request added server-side chunked resumable import
transfers; without clients, large imports still ride the single fragile
upload
> - The Import page and the CLI need to slice large packages, upload
parts with retry and progress, resume after interruptions, and preview
before applying
> - Preview is the missing server piece: the browser flow is
preview-then-import, so a completed spool must be previewable without
re-uploading
> - This pull request adds the transfer preview endpoint, switches the
Import page to the chunked path for zips over 48 MB, and teaches the CLI
the same for oversized local imports
> - The benefit is that large imports get progress, per-part retry, and
resume in both clients, while small imports keep the exact single-shot
path they have today
## Linked Issues or Issue Description
**What happened?**
With only the server transfer routes in place, users still upload large
company packages as one request from the Import page and the CLI: no
progress indication, no retry below the whole file, and no resume after
a dropped connection or refresh. The preview-then-import flow also
cannot run against an uploaded transfer, forcing a second full upload.
**Expected behavior**
A large package uploads once as verified parts with visible progress;
preview and import both run against the uploaded spool; an interrupted
upload resumes with only the missing parts re-sent; packages at or below
48 MB behave exactly as before.
**Steps to reproduce**
1. Select a 500 MB zip on the Import page over an unreliable connection.
2. Watch the single upload fail near the end and restart from zero,
twice — once for preview, once for import.
3. Same story headless via the CLI.
## What Changed
- Server: `POST /import/transfers/:id/preview` runs the existing preview
logic against the completed spool (shared assembly + whole-file
verification helper with apply); preview neither completes the run nor
deletes the spool, so the subsequent apply reuses it. Missing parts
respond with the missing list.
- UI: zips over 48 MB take the chunked path in both preview and import —
the file is sliced into 32 MB parts hashed with WebCrypto (single
ArrayBuffer, no second copy), the transfer is created or resumed (the
create response's missing-parts list drives what uploads), parts upload
sequentially with three attempts each and visible progress, then
transfer preview/apply replace the multipart calls. The existing preview
pane, collision handling, adapter overrides, and async job polling are
unchanged; ≤ 48 MB keeps the single-shot path.
- CLI: oversized local `.zip` or folder imports zip/slice/hash with node
crypto, upload with resume and per-part retry and progress lines, and
use transfer preview/apply. Small packages keep the inline path
byte-identical.
- Failure honesty: adapters/API errors fail open to existing behavior; a
part failing all attempts surfaces a durable error panel with resume
intact.
## Verification
- Server: preview-then-apply on one spool (run stays open, spool intact,
then apply completes), preview with missing parts rejected — added to
the transfer route suite (embedded Postgres).
- UI suite: large file takes the chunked path (manifest shape, part
uploads, progress, apply on a resumed transfer, single-shot endpoints
never called), small file stays single-shot, part failure after three
attempts surfaces the error panel without running preview, resume
re-uploads only the missing part.
- CLI: manifest slicing/hashing, threshold behavior for zip and folder
sources, folder-zip round-trip through the real zip reader, upload
resume/retry/exhaustion/already-completed, full-command chunked and
small-zip inline flows.
- Server, ui, cli typechecks clean. Exact counts in the PR checks.
## Risks
- The 48 MB threshold only routes between two verified paths; behavior
below it is untouched.
- Chunked CLI imports use the board-scoped transfer routes, so oversized
CLI imports need board credentials (agent tokens keep the agent-safe
small-file path). No privilege change — board actors already had the
generic routes — but the two size regimes differ semantically; called
out for review.
- A CLI dry-run over the threshold uploads parts before previewing; the
spool persists (24 h sweep) and a later apply resumes without re-upload
— inherent to preview-against-spool.
Stacked on #11223 — merge that first; this PR then shows only the
preview endpoint and client changes.
## Model Used
- Claude Fable 5 (`claude-fable-5`) via Claude Code CLI, with extended
thinking and tool use (multi-agent implementation with independent
verification).
## 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
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