## Summary
Brings the Keboola connector to feature parity with the legacy internal data-analyst's per-table sync strategies. Closes the four documented gaps from the spec branch (`zs/keboola-connector-specs`):
- **Typed parquet** in the legacy SDK extraction path — column types from Keboola Storage metadata (provider cascade `user > ai-metadata-enrichment > keboola.snowflake-transformation`) survive the CSV → parquet roundtrip; invalid date strings (`'0000-00-00'`) and invalid numeric strings (`'Non-Manager'`) become NULL while keeping the column's typed schema. Pre-fix everything was VARCHAR.
- **Incremental sync** via Storage API `changedSince` — opt-in per table; pulls only delta rows, merges into the existing parquet by `primary_key` (drop_duplicates with keep='last'). Cuts daily extraction from O(full table) to O(delta).
- **Partitioned sync** — flat per-partition layout `data/<table>/<key>.parquet` (e.g. `2026_05.parquet`), per-affected-partition merge for daily updates, chunked initial load with 1-day overlap and 2-empty-chunk stop heuristic.
- **`where_filters`** — server-side row filter with date placeholders (`{{today}}`, `{{last_3_months}}`, `{{start_of_3_months_ago}}`, etc.) resolved at sync time. Force the SDK path; reject `incremental + where_filters` combination at API layer (changedSince already filters temporally).
## Architecture
- **Schema migration v25 → v26**: 7 new columns on `table_registry`. Existing `sync_strategy` column reused (pre-v26 it was inert catalog metadata; post-v26 the extractor dispatches off it).
- **Per-table dispatcher** in `extractor.run()` routes to one of `_extract_via_extension` (full_refresh + extension), `_extract_via_legacy` (full_refresh + filters or extension fallback), `extract_incremental`, or `extract_partitioned`.
- **API conflict policy**: `incremental + where_filters` → 422; `partitioned + query_mode='remote'` → 422; `partitioned ⇒ partition_by required`.
- **Admin UI**: third "Direct extract (Storage API)" radio in the Keboola Register / Edit modals, alongside existing "Whole table (extension)" and "Custom SQL". When selected, exposes a v26 sync-strategy panel with conditional fields per strategy.
## Test plan
- [x] **Unit + module** — 134 v26 tests covering migration, repo, parquet_io, where_filters, incremental (compute_changed_since + merge_parquet + extract_incremental E2E), partitioned (key derivation + merge_partition + chunked windows + extract_partitioned E2E), extractor dispatcher, admin API validators, PUT field clearing, registry-shape → dispatcher bridge
- [x] **HTML form structure** — all v26 inputs + visibility classes + JS payload fields verified in rendered template
- [x] **Real Keboola roundtrip** — registered a small test table as `sync_strategy='incremental'` against a test Storage project, triggered two syncs:
- Sync 1: `changedSince=None` → full pull → 9 rows typed parquet
- Sync 2: `changedSince=last_sync - 1d window` → 9 delta rows merged with 9 existing → 9 after dedup on primary_key (PK merge confirmed)
- [x] **Browser UX** — agent-browser session against a local uvicorn: login → admin/tables → register modal → switch radios → verify field visibility per strategy → submit → edit existing row → switch to Direct/Incremental → save → confirm DB persistence
- [x] **Regression** — no regressions in the broader 3252-test suite (3 pre-v26 tests updated for the deprecation-marker removal + schema-version bump; 2 pre-existing environment-sensitive test failures unrelated to this change)
## Bugs caught + fixed during E2E
The browser + real-Keboola roundtrip exposed four bugs the unit tests missed:
1. **JS visibility race** — two competing `forEach` loops set `display=''` then `display='none'` on form elements sharing `kb-strategy-incremental kb-strategy-partitioned` classes (window_days + max_history_days are reused across strategies). Fix: single-pass selector with class-based visibility resolver.
2. **PUT cannot clear field** — pre-v26 `updates = {k: v ... if v is not None}` collapsed "omitted from body" and "sent as null" into the same case, so admin couldn't switch a partitioned row back to full_refresh and have stale `partition_by` clear. Fix: `model_dump(exclude_unset=True)`.
3. **Subprocess DB lock conflict** — `_read_last_sync` reopened `system.duckdb` while the parent server held the write lock (subprocess contract at `app/api/sync.py:_run_sync` line 260). Fix: parent injects `__last_sync__` into table_config before subprocess spawn.
4. **Wrong KBC table_id** — `extract_incremental` / `extract_partitioned` built the Storage API table_id from the registry row's slugified `id` (`circle_inc`) instead of `bucket.source_table` (`in.c-finance.circle`), producing 404s. Fix: prefer `bucket+source_table`; fall back to `id` only when bucket empty.
## Operator notes
- Existing tables stay on `full_refresh` after migration; admins opt individual tables in via `agnes admin register-table --sync-strategy ...`, the Keboola Edit modal, or `POST/PUT /api/admin/registry`.
- `merge_parquet` and `merge_partition` use `pd.concat + drop_duplicates`, loading both existing and delta into pandas RAM. For tables in the multi-million-row range this may OOM — switch to `partitioned` strategy for those (per-partition merge keeps memory bounded). Documented in `### Internal` of the changelog entry.
- Date placeholders are resolved at **sync time**, not register time — a typo'd `{{lasst_week}}` is accepted at register and surfaces only when the next sync runs. By design (rolling windows need late-binding).
## Spec source
The four corresponding plans on the `zs/keboola-connector-specs` branch under `docs/superpowers/plans/2026-05-07-0[1-4]-*.md` capture the design rationale and link back to internal repo references for each subsystem.
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