Char-count guards on value/id can still let multibyte or escape-heavy
inputs blow past MAX_ENCODED_CURSOR_LENGTH once UTF-8 + escape expansion
+ base64url runs. A 512-character name of 'é' (2 bytes UTF-8) or '<'
(serializes to the 6-byte '<' escape) passes the char check, mints
a ~1500-byte cursor, then 400s when handed back on the next request.
Compute the final encoded form and reject it before returning if it
exceeds the wire cap. Adds regression tests for both inflation paths.
Six fact-checked findings from the multi-model review pass:
- Encoder/decoder length asymmetry: encode_cursor now rejects empty id,
oversized id (>128), oversized value (>512), and invalid order tokens
symmetrically with decode_cursor. Prevents the same server from minting
a cursor it then 400s on the next request (e.g. a filesystem-scanned
asset name >512 chars). The bad-order path now raises InvalidCursorError
(still subclasses ValueError) so route-layer handling stays uniform.
- Raw U+2028/U+2029 in cursor.py source: ripgrep treated those lines as
line-terminators, confirming the bytes were the actual separators. Any
editor save / autoformat / git tooling that normalizes invisibles would
silently break the encoder. Replaced with explicit /
Python escape sequences.
- set(seen) == set(names) hid ordering regressions: a cursor walk that
dropped a row at a page boundary or returned duplicates could pass.
Reworked the assertion to (1) reject duplicates, (2) require full
coverage, and (3) assert strict positional order for size sort, the
only field with a clock-independent ordering.
- Flaky time.sleep(0.05) between inserts: Windows CI clock resolution is
~15ms, so back-to-back inserts under load could collide and exercise
the tiebreaker instead of the documented path. Removed the sleep and
let the strengthened assertion above carry coverage / no-duplicates,
with size sort carrying strict order.
- Cursor error envelope diverged from the rest of routes.py: cursor 400s
emitted {error: {code, message}} while every other 400 in the file
emits {error: {code, message, details}} via _build_error_response.
Switched to _build_error_response and added the details field to the
AssetsApiError schema in openapi.yaml.
- "Byte-identity fixtures" only checked substring containment, defeating
the test class's stated purpose of pinning the wire format. Switched
to exact-bytes equality against an inline expected payload string per
fixture, so any whitespace / key-order / escape drift fails loudly.
Also dropped Go / json.Marshal references from docstrings — the byte
format is the contract, not the runtime that mints it.
Strip prose references to sibling Go implementations and external
ticket IDs from cursor.py, the cursor tests, the keyset integration
tests, asset_management's sort-field comment, and the legacy
prompt_id alias comment. Pure docstring/comment scrub — no behavior
or wire-format changes. x-runtime: [cloud] field annotations in
openapi.yaml are unchanged; those are the spec's structural
cross-runtime convention, not internal references.
Cursor pagination hasn't shipped on either runtime yet — this PR is
still draft and cloud's mirror is just behind it — so there are no
legacy no-o cursors in the wild. Make o mandatory from day one
rather than landing permissive and tightening later.
decode_cursor now rejects any payload without o (or with a non-string
o) as malformed. CursorPayload.order becomes a required str. Tests
that constructed CursorPayload directly now pass order="desc";
test_legacy_cursor_without_order_accepted flips to
test_cursor_without_order_rejected.
Address three needs-judgment items from the cursor-review judge synthesis:
1. Cursor wire format now includes an "o" key carrying the sort
direction ("asc" / "desc") it was minted under. A request that
replays the cursor with a flipped `order` parameter is rejected
with 400 INVALID_CURSOR instead of silently walking the wrong
direction. Legacy cursors without "o" still decode (the binding
is best-effort until cloud mirrors the field — follow-up filed
separately).
2. JSON serialization now escapes `<`, `>`, `&`, U+2028, U+2029
to mirror Go's default `json.Marshal` behavior. Without this, an
asset name containing those characters produced different bytes on
Python vs cloud Go. The escaped form is what both runtimes emit.
3. Add direct query-layer tests for the keyset tiebreaker — the secondary
ORDER BY id branch was previously unexercised. Two scenarios: all
rows share a primary sort value, and mixed ties straddle page
boundaries. Both assert no row is dropped or duplicated across the
walk.
Wire-format note: Python cursors now differ from current cloud cursors
by exactly the "o" key. Cloud follow-up will bring the two back into
byte alignment.
- Mint next_cursor on every cursor-supported sort, not only when 'after'
was supplied. A first request (no 'after') previously returned
next_cursor=None, leaving cursor mode unreachable from a clean start.
- Over-fetch limit+1 so an exactly-full terminal page doesn't mint a
spurious cursor pointing at a phantom next page.
- Map crafted out-of-range microsecond cursors (OverflowError / OSError
in datetime construction) to 400 INVALID_CURSOR instead of leaking 500.
- Bump MAX_CURSOR_VALUE_LENGTH 256 -> 512 to match the AssetReference
name column max; without this, a long-named asset minted a cursor the
same server then refused on the next request. Cross-runtime byte
identity with cloud is unaffected because no cloud cursor ever carries
a value > 256 (cloud schema doesn't permit it).
- Return None from _encode_next_cursor when the boundary row carries a
NULL sort value (e.g. an Asset without size_bytes backfilled), instead
of silently encoding 0 and mis-positioning the keyset.
- Fix schemas_in.py comment so it matches actual handler behavior
(last_access_time + 'after' raises 400, does not fall back).
- Add AssetsApiError schema + 400 response to GET /api/assets in
openapi.yaml so generated clients know the INVALID_CURSOR envelope.
- Extend integration coverage: first-page mint, exact-multiple terminal
page, cursor walks for created_at/updated_at/size sorts, datetime
overflow surfaces as 400 not 500.
- Add unit coverage for datetime overflow and 512-char round-trip.
Port of cloud common/pagination/cursor.go. Wire format is base64url of
{"s", "v", "id"} JSON; times are Unix microseconds UTC to match
PostgreSQL timestamp precision.
Includes a byte-identity fixture pinned against the cloud Go wire
format so cross-runtime FE pagination can't silently drift.
