[ADR-0057] P4 follow-ups — live handoff verification + context-carrying upgrade (cloud#817)

[os-zhuang]

Self-contained follow-up work order for ADR-0057 P4 (ask→build explicit handoff). Written for an agent with no prior context. Rolls up to epic #2409.

Background (already shipped — do NOT rebuild)

ADR-0057 P4 landed the explicit "Open in Builder →" handoff across two repos:

• cloud — @objectstack/service-ai-studio gained a suggest_builder signal tool + an ask-only builder_handoff skill; the ask agent's instructions now call it to decline-and-redirect an authoring request (ADR-0063). Handler echoes { status: 'build_handoff', handoff: 'build', prompt, packageId? }. Merged: objectstack-ai/cloud#818.
• objectui — plugin-chatbot detectBuilderHandoff lifts that result onto the tool invocation; ChatbotEnhanced renders the "Open in Builder →" card (onOpenBuilder prop). app-shell wires the full-page AiChatPage (ask) + the FAB to navigate to /ai/build?package=…&handoffPrompt=…; the build surface seeds that prompt as its first message. Merged: feat(console-ai): explicit "Open in Builder →" ask→build handoff (ADR-0057 P4) #2439.

Both sides are unit-tested and CI-green. Read: docs/adr/0057-console-ai-chat-one-conversation-docked.md, cloud ADR-0063 (two agents, surface-bound), ADR-0013 (durable turns).

Tasks

1 · Live end-to-end verification (ADR-0054 browser proof)

The one step not verified at merge time: the ask agent actually choosing to call suggest_builder. It was blocked in the authoring session only by that environment's egress policy denying ai-gateway.vercel.sh (403 CONNECT) — not by code or key.

In an environment where the Vercel AI Gateway is reachable (a valid AI_GATEWAY_API_KEY + AI_GATEWAY_MODEL, e.g. a real openai/gpt-4o-mini):

• Boot the local stack (cloud/scripts/dev-local/run-stack.sh --with-ui --seed --keep, OBJECTUI_ROOT=<objectui>); put the key in cloud/scripts/dev-local/.env.local (gitignored).
• Headless check first: POST /api/v1/ai/agents/ask/chat with a build-shaped message (e.g. "add a priority field to the tasks object") → the stream must contain a suggest_builder tool call whose result carries status: 'build_handoff'.
• UI proof: in ask, send that request → the "Open in Builder →" card renders → click → lands on /ai/build?package=…&handoffPrompt=… and the seeded prompt auto-sends. Attach the screenshot(s).

2 · cloud#817 — context-carrying handoff (upgrade v1)

Today v1 carries only { prompt, packageId? }. Upgrade the handoff to carry the ask thread's conversation context into the Builder (durable-turn reference, ADR-0013), so build resumes with what the user already discussed — not just a one-line prompt.

• cloud: extend the suggest_builder contract (or add a handoff-context endpoint) to reference the source conversation/turn; define what transfers.
• objectui: consume it in the onOpenBuilder path (generalize assistant/assistantBus.ts per the ADR) instead of only the URL handoffPrompt; seed the Builder from the carried context.
• Keep the ADR-0063 invariant: explicit, user-initiated switch — never a silent re-route.

3 · FAB dismissal polish (minor)

When "Open in Builder →" is clicked from the console FAB (ConsoleFloatingChatbot), the floating overlay does not auto-close — FloatingChatbot/FloatingChatbotProvider expose no external close control today. Add one so the FAB dismisses when it hands off to the full-page Builder (the full-page AiChatPage handoff already replaces the view, so only the FAB needs this).

References

Epic #2409 · work order #2412 · ADR docs/adr/0057-console-ai-chat-one-conversation-docked.md · merged P4: objectstack-ai/cloud#818 + #2439 · cloud#817 (context-handoff, task 2).