pi streams AssistantMessages with NO id (verified against a captured
live stream and pi-ai's AssistantMessage type): the id exists only once
the server's persistTurn stamps the record. applyWireEvent minted a
FRESH c_ id per event, so message_start appended, every message_update
found no match and APPENDED another full copy, and message_end appended
again - the tail grew one message per chunk. projectView's step
separators + thinking blocks then filled the transcript with dividers
and thinking indicators mid-stream (with fresh React keys remounting
the whole subtree per chunk), cleaned up only by the settle sync's
setMessages(record).
The fix: the in-flight assistant message is tracked by SLOT -
message_start mints and remembers one client id; message_update and
message_end REPLACE that same tail entry (pi guarantees exactly one
streaming message at a time via its strict start-updates-end ordering;
the reattach replay replays the same sequence). An explicit
message.id on the wire still wins; the slot clears at message_end,
stop(), and setMessages().
Tests: all streaming fixtures rewritten to pi's real shape (no
message.id) - the old ones encoded the wrong assumption - plus a
regression pin asserting N id-less updates leave exactly ONE assistant
message in the tail with a stable slot id.
Verified live mid-stream (DOM sampled every 500ms during a teaching
turn): 0 separators throughout, thinking blocks 1-2 (one per step, not
per chunk), text growing smoothly.
Live-driven via the owner's dev server (browser tools), reproduced on
/chat/new: send fires, optimistic appends, POST never happens, and the
page shows the frozen empty state. Three compounding defects:
1. session-core: default fetch stored UNBOUND — the browser's native
fetch requires this === Window, so every call threw 'Illegal
invocation' and the POST /api/chat never fired. Node's undici has no
receiver discipline, which is why 994/994 tests passed while the app
was dead. Now defaulted through a receiver-preserving wrapper; pinned
by a strict-this regression test (the browser's semantics simulated.
2. session.ts: state memo keyed on [model, forceRender] — the reducer
dispatch is STABLE by contract, so the memo computed once per mount:
no optimistic bubble, no stream events, no error banner. The view was
frozen at first render. Rekeyed on a version counter bumped by the
model's onChange.
3. view.ts: turn_end carries the clean 'Question posed' placeholder as
a toolResult message (details: null) — applyResult flipped the quiz
part to output-available with a null output and AnsweredCard crashed
on answer.dismissed (killed the whole page render). Fork 2 now holds
on the message-attachment path too: clean question results with null
details are ignored; the AnsweredCard renders only the learner's real
answer. Regression pin extended in session-core.test.ts.
Verified live end to end: new session → text send → probe questions in
the dock → ask answer → graded ✓ quiz card with explanation → reload
renders the full transcript from the native record with the pending
question intact.
EOF
)
Server: ui-stream.ts is verbatim pi AgentEvent passthrough (SSE data
lines + [DONE]); only app-level events are the loop-level error and
turn-settled terminal; onError carries raw provider text (owner ruling).
Client: useChat + the AI-SDK transport replaced by components/session-core.ts
(SessionModel: 409 identity-retry, optimistic c_ appends, absorbed()
adoption, needsContinuation, shared consume for POST + reattach) and the
session.ts hook; the golden-master grouping canon moved client-side into
core/view.ts (projectView); scanners read the native record (phaseAt3Lh,
danglingQuestionOf, graph toolParts, plan-blocks, runner, extraction).
Coverage: the native message is the unit (fork 3) with the call+result
inseparability bond rule; view-line-less messages (markers, error
results) are invisible to coverage and never checkpointed.
Deletes: chat-transport, projection, ui-message, their tests (ported to
tests/session-core.test.ts), and the ai + @ai-sdk/react dependencies —
the Vercel SDK is fully out of the tree. Wire pins in chat-flow rewritten
onto the AgentEvent dialect (eventsOf parser).
Gates: tsc clean, 994/994 tests, eslint clean, build green; live smoke
on PORT=3004 (verbatim wire → native record).
amosblomqvist