Two independent fastapi divergences from the green north-star kept this red:
1. Missing chunkSize:9999 on the 8 tool-call fixtures. Under aimock's global
8-byte chunking the large tool-call args failed to JSON-parse in one piece,
so the AAPL->MSFT reasoning chain stopped at leg 1 (turns 1 & 2). Byte-align
to LGP (and the green mastra/langgraph-typescript siblings carry the same
pattern).
2. Fixture-pool shadowing broke turn 3. aimock pools all d4+d6 fixtures for a
context and matches by userMessage substring, first-match-wins in load order
(d4 before d6). fastapi had broad keys LGP doesn't:
- d4/chat.json: 'weather' -> 'weather in San Francisco', 'flights from SFO
to JFK' -> 'Find flights from SFO to JFK.' (period-terminated so it stops
being a substring of turn 3's 'Find flights from SFO to JFK and show me
the weather there.').
- tool-rendering-{custom,default}-catchall.json: bare 'Find flights' ->
'Find flights from SFO to JFK.' (now matches LGP's exact key).
Also byte-align the backend agent to LGP: scriptable get_stock_price signature,
the detailed chaining system prompt, model gpt-5.4, reasoning summary detailed.
D6 tool-rendering-reasoning-chain green (two real ~21s runs). Shared-fixture
regression all green: agentic-chat, tool-rendering, tool-rendering-custom-catchall,
tool-rendering-default-catchall, headless-complete (Tokyo-weather consumer).
gen-ui-agent had no dedicated backend graph: langgraph.json lacked a
gen_ui_agent entry and route.ts routed the name through the neutral-assistant
loop to sample_agent, which has no steps state or set_steps tool, so the
progress card never mounted (agent hit the default recursion limit of 25).
- Port LGP's gen_ui_agent.py (byte-identical) and register it in langgraph.json.
- route.ts: bind gen-ui-agent to createAgent("gen_ui_agent") and bake
assistantConfig.recursion_limit (default 100) into every LangGraphAgent —
the graph's Python with_config isn't visible to the server runs API, so the
multi-step set_steps walk overran 25. Mirrors langgraph-python.
- aimock: regenerate d6/gen-ui-agent.json from LGP (adds chunkSize:9999 on the
24 tool-call fixtures) and narrow the over-broad d4 chat.json "summarize" key
to "Summarize the sales pipeline" so it stops substring-shadowing the
competitor set_steps chain (and other summarize prompts). Matches LGP.
D6 langgraph-fastapi:gen-ui-agent now green (two real ~14s runs);
agent-config re-verified green (no regression).
Move monolithic d5-all.json + feature-parity.json + smoke.json into
per-integration directories under d4/<slug>/, d6/<slug>/, and shared/.
Every fixture file is now context-scoped to enable server-side aimock
routing via match.context. Migrated 12 HITL fixtures from main's
d5-all.json additions into shared/_migrated-from-d5-all-hitl.json
for follow-up distribution into per-integration files.
Mark