ask tool silently returns zero citations (dead 'citations' SSE handler)

[arnav2]

Summary

The ask tool returns no citations, always. _stream_answer in src/ks_mcp/tools/ask.py handles a citations SSE event that the backend never emits, so the citations list stays empty and AskResult.citations == [] for every answer (asserted, unknowingly, by tests/test_schema.py).

Root cause

ask.py is SSE-only — it opens the thread stream, accumulates text_deltas, and expects a citations SSE event to carry citations:

# src/ks_mcp/tools/ask.py (~line 131)
elif event == "citations":
    for raw in payload.get("citations") or []:
        citations.append(_to_ask_citation(raw))

But on the backend:

• the citations SSE event was never wired — ThreadStreamEvent.CITATIONS / CitationsPayload had zero producers and have now been removed (ks-backend PR #474);
• even had it fired, its payload was a bare Citation (chunk_id, quote, offsets) — not the enriched shape _to_ask_citation expects (document_id, document_name, materialized_path).

The backend contract is: citations live on the persisted message, not on the wire. The frontend gets them by refetching the message after the stream (content.citations, enriched with document ancestry + permission-filtered). ks-mcp never refetches, so it gets nothing.

Fix

After the stream ends (message_end / [DONE]), do a REST GET of the message ks-mcp already tracks (it captures message_id from the message_start event) and populate citations from content.citations:

• GET /v1/threads/{thread_id}/messages/{message_id} (or list) via ksapi
• read content.citations — already enriched (document_id, document_name, materialized_path) and permission-filtered by the read API
• map into AskCitation (the shape already matches the enriched content.citations)

with_details=false is enough: ks-backend PR #474 decoupled citation enrichment from with_details, so a light request now still returns enriched citations — one small request, no step-timeline payload.

Then remove the dead elif event == "citations" branch from _stream_answer.

Refs

• ks-backend PR #474 (removed the dead citations SSE event; decoupled enrichment from with_details)
• src/ks_mcp/tools/ask.py _stream_answer / _to_ask_citation
• tests/test_schema.py (assert result.citations == [] — update once fixed)