[thekevinbot]

Fixes #1139. Part of #1072.

event_to_value in packages/rust/src/cli/serialize.rs was the third
hand-written RowEvent flattening: an arm-for-arm match repeating the
lowercase action strings, the Update new_row/old_row split, and the Error
variant's nullable table and to_string_lossy path. #1131 moved those
decisions into dirsql::flatten_row_event and cut both bindings over; this is
the missed call site.

The SSE shape is not the flat struct — the error arm omits row/old_row
entirely and the row arms carry no error key — so the serializer consumes
flatten_row_event and adds only that transport detail: a presence check on
flat.error. row_to_json still does the cell marshaling, blob-to-hex
included.

Key order is unchanged because serde_json::Map is a BTreeMap here
(cargo tree -p dirsql -i serde_json -e features | grep -c preserve_order →
0), so the hand-built map renders alphabetically exactly as the json!
literals did.

Two assertions were added, neither weakening an existing one: the insert test
now asserts no error key, and a new test covers the error arm's table: null
plus the absence of row/old_row.

PARITY.md gains a line noting the SSE serializer shares the same source.
This restores parity rather than introducing drift; no SDK API or CLI flag
changed.

Byte-identical SSE proof

Built the CLI twice from the same worktree — once at origin/main, once with
the change — and ran the identical scenario against the same fixture path
(insert, update, error, delete) with curl -sN http://localhost:7139/events.

Fixture (/tmp/dirsql-1139-fixture): a posts table over posts/*/*.json
whose on-file hook emits basename/size, and prints non-JSON for any file
named bad* so the error arm fires. Driven by:

printf '{"a":1}'     > posts/alice/Brand-New.json   # insert
printf '{"a":22222}' > posts/alice/Brand-New.json   # update
printf '{}'          > posts/alice/bad-one.json     # error
rm                     posts/alice/Brand-New.json   # delete

Both binaries produced, byte for byte:

data: {}
data: {"action":"insert","file_path":"posts/alice/Brand-New.json","old_row":null,"row":{"basename":"Brand-New.json","size":7},"table":"posts"}
data: {"action":"update","file_path":"posts/alice/Brand-New.json","old_row":{"basename":"Brand-New.json","size":7},"row":{"basename":"Brand-New.json","size":11},"table":"posts"}
data: {"action":"error","error":"on-file output was not a JSON array of rows: invalid JSON: expected ident at line 1 column 2","file_path":"posts/alice/bad-one.json","table":"posts"}
data: {"action":"delete","file_path":"posts/alice/Brand-New.json","old_row":null,"row":{"basename":"Brand-New.json","size":11},"table":"posts"}

$ diff <(grep '^data:' main.sse) <(grep '^data:' new.sse); echo $?
0

(The captures also contain a duplicate error line from the hook running twice
on the create+write pair; it is present identically in both.)

Coverage

cargo +nightly llvm-cov --lib --features cli --branch in packages/rust:
regions 93.67%, functions 93.16%, lines 94.54%, branch 79.49% — all above the
[rust.coverage] floors (lines 92 / functions 91 / regions 91 / branch 72).
No floor moved. unit mutation (rust): 1 mutant tested, 0 survivors.

E2E Verification

• Ran e2e suites locally for every affected SDK
• Python SDK e2e: pass
• TypeScript SDK e2e: pass
• Rust core e2e (if applicable): pass
• packages/python/e2e-attestations/<branch>.json receipt written if packages/python changed (just e2e-attest-python)
• packages/ts/e2e-attestations/<branch>.json receipt written if packages/ts changed (just e2e-attest-ts)
• Command(s) run: cargo test --workspace --features cli; just e2e-attest-python; just e2e-attest-ts; just preflight
• Result summary: rust workspace green (887 lib tests + integration/e2e suites, 0 failed); python e2e 37 passed; ts e2e 17 passed across 5 files; just preflight → 0 failing pair(s), 3 skipped.

Changelog / Migrations

• Changelog fragment added under <root>/<pkg>/changelog.d/ for each changed package (or: skip-changelog trailer on a commit with reason)
• Migration fragment added under <root>/<pkg>/migrations.d/ (or: not required -- additive/bugfix only)

Changelog: packages/rust/changelog.d/2026-09-18-sse-shares-flatten-row-event.md
(Changed). No migration fragment: the refactor is behavior-preserving and
the wire body is unchanged.