Phase 3 of the delta-sync plan — the inverse direction, so a future
client app holding an older local version can fetch only what changed:
- GET /api/files/{id}/manifest returns the file's chunk recipe
({file_hash, total_size, chunks}). Owner-scoped like the rest of the
delta surface (Read permission through the authz engine first, then
the chunk layer's possession standard; shared files use the regular
download endpoints). A manifest is immutable for a given file_hash,
so it is served with ETag = file_hash and If-None-Match answers 304 —
polling sync clients pay one header round-trip per unchanged file.
Legacy pre-CDC blobs are presented as a single-chunk manifest of
themselves, so clients need no special case.
- POST /api/files/delta/download streams the requested chunks as
[u32 BE length][bytes] frames in request order — the same wire format
the upload direction uses. Entitlement is the same possession rule as
negotiate/commit (chunks reachable through the caller's own files);
anything else returns 404 {not_available} — deliberately
indistinguishable from "never existed" — with a
delta_download.rejected audit event. Batches are bounded by the
chunk_max_bytes budget; Content-Length is exact (sizes come from the
dedup index) and peak RAM is one backend read frame.
Both endpoints share the delta rate limiter. New DedupService
primitives: manifest_chunk_list (with legacy fallback), chunk_sizes,
chunk_stream. OpenAPI regenerated; protocol doc gains the download
section; types.js maps the new wire shapes (plus the delta-upload
typedefs that a container reset had silently dropped from a previous
commit).
Verified end-to-end against PostgreSQL 16 with a simulated two-device
sync: device A uploaded 24 MB by bytes and delta-updated it (2 edits →
2 chunks); device B diffed the manifest against its WASM-chunked local
copy, needed 2/79 chunks, fetched 970 KB instead of 24 MB (96.1%
saved) and rebuilt the file byte-identical with the BLAKE3 verifying.
If-None-Match revalidation returned 304; a second user got 404 on both
the manifest and the chunk batch (with the not_available list and
audit lines); an unknown hash was indistinguishable from a denied one;
an empty hash list returned 400.
https://claude.ai/code/session_01WdNenpnujNR2sc32XVvwfS
Phase 1 of the delta-sync plan, server side. The CDC store already shares
unchanged chunks between file versions after the bytes arrive; these three
stateless endpoints move that detection to the client, so editing a few
bytes of a large file uploads ~1 MiB instead of the whole file:
- POST /api/files/delta/negotiate — given the file's chunk hashes, answer
which ones the caller must upload. User-scoped and purely advisory.
- PUT /api/files/delta/chunks — missing chunks as [u32 BE len][bytes]
frames (streaming parse, ≤1 MiB per frame, chunk_max_bytes per request).
Every hash is recomputed server-side; chunks land as ref_count=0 orphans
that a commit pins or the periodic GC sweeps — no session table.
- POST /api/files/delta/commit — pin one reference per distinct chunk with
a single UPDATE…RETURNING restricted to chunks the caller is entitled
to (reachable through their own non-trashed files, or unreferenced
orphans); anything else returns 409 {still_missing} for the client to
upload and retry. The pinned sequence is then RE-READ and the whole-file
BLAKE3 recomputed before any manifest exists — a declared file_hash is
never trusted, because a forged manifest would poison future whole-file
dedup hits for other users. The manifest accounting is shared with the
byte path (attach_manifest, extracted from store_from_stream); the file
row is created (201) or its content swapped by file_id (200). Owners of
the exact file_hash short-circuit to a pure reference bump.
Supporting pieces: GIN index on chunk_manifests.chunk_hashes (containment
probes were sequential scans), claimable/pin/release/store-loose/verify
primitives on DedupService, update-by-id with Update-permission AuthZ on
FileUploadService, per-caller rate limiter (240/min), audit events with
stable reasons (rate_limited, chunk_verification_failed,
file_hash_mismatch), OpenAPI + docs/delta-upload-protocol.md, framing
parser unit tests and a PG-gated integration suite covering the
entitlement matrix (owned/foreign/orphan/unknown), orphan registration
and the verification read.
Verified end-to-end against PostgreSQL 16 with a node client hashing via
the vendored WASM: a 24 MB file delta-committed in 96 fixed-size chunks;
a 3-byte edit then negotiated missing 1/96 and synced with 278 KB on the
wire vs 24 MB (98.9% saved), downloading byte-identical. A second user
probing the same chunks got nothing (negotiate: all missing; commit: 409
with all 96 still withheld); a forged file_hash returned 400 plus the
audit line; a commit referencing one never-uploaded chunk returned 409
naming exactly that hash; the GIN index serves containment probes
(Bitmap Index Scan) once the planner favors it.
https://claude.ai/code/session_01WdNenpnujNR2sc32XVvwfS
Claude