Delete checkpoints before removing business fields. Suppress only an
explicit CheckpointNotFoundError; propagate storage failures and
cancellation so the endpoint cannot report false success. Prefer async
checkpoint deletion and fail clearly when cleanup is unsupported.
Classify SSE error events as 401 for authentication, 429 for rate limits,
and 500 for other failures, using the same fixed messages as non-stream
responses. Errors terminate the stream without a success done event or
provider exception text in the response.
Validation: 286 offline tests passed (19 added), including failed-delete
HTTP retry with preserved business/checkpoint state, explicit missing
threads, cancellation, missing cleanup capability, and HTTP SSE errors
before and after text output.
- Validate stage prefixes before forwarding model tokens. Invalid prefixes
may use the existing repair budget; once output starts, validation failure
aborts the turn without appending a regenerated reply. Bound the token
queue and close inner streams when consumption stops.
- Replace delete-time lock eviction with reference-counted session locks
covering holders and waiters. Serialize set/get with chat/stream/delete
and release cancelled waiters without replacing a live lock.
- Store person synonyms under workflow-native driver keys and expose
consistent alias views to single/group reads and graph prompt injection.
- Separate committed field patches from public formUpdate visibility.
Commit callbacks keep repository fields synchronized even when updates
are hidden or the consumer closes after graph completion.
- Disable OpenAI SDK automatic retries. Own bounded retry attempts in the
application, use 1/2/4 second backoff, retry streams only before text is
emitted, enforce attempt timeouts, and close upstream/client resources.
- Translate FastGPT SDK max_retries (total attempts) from the configured
extra-retry count, and verify the real SDK loop uses four attempts.
- Document the per-LLM budget and streaming failure semantics without
claiming the whole multi-call HTTP turn has the same timeout.
Validation: 267 offline tests passed, including actual SDK requests through
MockTransport, stream repair/abort, timeout/close, lock races, aliases and
formUpdate visibility; existing four dependency deprecation warnings.
FastGPT serializes requests per chatId server-side; the LangGraph
backend held all state in memory with no locking, so two concurrent
requests on one session could interleave (checkpoint write races,
garbled no_reply/turn bookkeeping).
- AccidentAppService holds per-session asyncio locks; chat(), stream()
and delete_session() execute under the session lock (LLM call
included - same-session turns are strictly serialized, different
sessions never contend)
- set_info/get_info stay synchronous and lock-free: repository
load/apply_update are atomic dict operations with no mixed
intermediate state; a racing set vs chat yields one complete value
- delete pops the lock entry after cleanup; a chat that arrived
concurrently executes afterwards against the fresh (deleted)
session - matching FastGPT's delete-then-chat new-conversation
semantics
- tests: same-session concurrent chats serialize (interval pairing
probe), different sessions run parallel, delete waits for in-flight
chat, chat-vs-set interleave leaves no torn values
Verified: 219 unit tests (4 new concurrency tests)
- fields_registry: FORM_TO_BUSINESS_KEY bidirectional mapping between
the graph's six form keys (has_injury...) and the acd business keys
(ywrysw...); bjrjs/ywmtc have no form source (set_info only);
business_patch_from_form maps graph diffs to whitelisted business keys
and filters internal/unknown keys
- app_service: chat injection now maps repository business keys back to
form keys; both complete() and stream() write back field diffs
(FormUpdate events captured in stream, closing the skeleton gap);
form keys never leak into the business repository
- docs/assignment6-compat.md: mapping table documented, stream write-back
backlog item resolved
- tests: mapping coverage, write-back mapping end-to-end, reverse
mapping injection (bjrjs/ywmtc excluded), stream FormUpdate write-back
Verified: 205 unit tests
- fields_registry: 24 business keys in acd/human1/human2 groups with
value_type, writable and SensitiveLevel metadata; strict bool/int
parsing (no bool('0') trap); INTERNAL_FIELD_KEYS protection list
- repository: SessionRepository protocol + InMemorySessionRepository
(idempotent delete; PostgreSQL swap-in is assignment 7)
- AccidentAppService: chat/set_info/get_info/delete_session share one
business state - chat injects latest repository fields into the graph
and writes back validated field diffs; set/get/delete make zero LLM
calls and zero helper conversations (includeInputInfo accepted but
unused); unknown get keys keep the '' JSON-empty-string contract,
unknown set keys are rejected by whitelist
- ChatInput.injected_fields neutral contract extension; LangGraphBackend
merges injected fields into graph input (set_info visible next chat)
- endpoints: thin layer - langgraph mode routes business state through
the app service (fastgpt mode keeps the legacy path); delete cleans
repository + graph checkpoint, idempotent
- tests: registry completeness (sfzmwh/sjwh/csbw included), app service
combos with LLM-call spy, HTTP acceptance flow (set -> get -> chat ->
groups -> delete -> no leak, idempotent re-delete)
- docs/assignment6-compat.md: behavior diff list vs FastGPT status quo
and the audit backlog (arbitrary set_info key usage, stream formUpdate
write-back, sensitive-field display boundary)
Verified: 200 unit tests (172 existing + 28 new)
Eric Wang