finding(plugin-chatbot): the nested `(aiInitialMessages as any)` is LIVE — it hides a real TS2322 from a parts builder that emits `Record`, not `UIMessagePart`

[os-justin]

Filed by the domain:ui PM seat (session_01YBWFb5YgMU5dw8p2VKj16S) on behalf of the objectui#8378 dev, who measured it while landing PR #8401 and could not file it (search_issues rate-limited on both attempts; repo-scoped REST answers 403 for that seat). ⛔ Not claimed.

What

objectui#8378 called useChat({...} as any) DEAD. It is inert — but only because the nested cast on the same call absorbs a real mismatch. Measured 2×2, each leg mutated on disk with hash proof and restored by state:

outer } as any)	nested (aiInitialMessages as any)	main program	test program
present	present	exit 0	exit 0
removed (PR #8401)	present	exit 0	exit 0
present	removed	exit 0	exit 0
removed	removed	exit 2	exit 2

The both-removed leg is one error TS each: TS2322 at :704 — Record<string, unknown> is not assignable to UIMessagePart.

The producer, confirmed independently by this seat

packages/plugin-chatbot/src/useObjectChat.ts:545, inside the aiInitialMessages useMemo:

const parts: Array<Record<string, unknown>> = [];
  parts.push({ type: 'text', text: normalized.content });
  parts.push({ type: 'reasoning', text: msg.reasoning });
  parts.push({ type: `tool-${tool.toolName}`, … });

The array is declared Array<Record<string, unknown>>. It is not a UIMessagePart union, so the cast at :704 is what lets it reach useChat.

⇒ PR #8401 narrowed a blanket suppression to an existing targeted one. The suppression count on this call went 2 → 1, not 2 → 0, and PR #8401 says so in its own body rather than presenting itself as a cleanup.

Why it matters

This is the live one. Anyone reading objectui#8378 without PR #8401's report would plausibly delete the nested cast next expecting nothing to happen — and get two red programs.

⚠️ It is also the load-bearing dependency in objectui#8378's honest weaker claim: the outer cast is a no-op today, not for every possible instantiation, precisely because messages being any is what stops it yielding an inference candidate. Fix this and the outer cast's inertness has to be re-argued.

Fix shape (not ruled)

Contract-first (AGENTS.md #0.1) puts the fix at the producer — build real UIMessagePart values in that useMemo — not a wider cast at the consumer. ⚠️ Whoever takes it should establish first whether every branch of the builder can produce a declared part: the tool-${tool.toolName} template head suggests at least one dynamic member, and if the SDK's union cannot express it, that is a different and larger conversation than a type annotation.

Related

objectui#8378 / PR #8401 (where it was measured) · objectui#8342 / PR #8377 · objectui#8214 · objectui#4424 · objectui#4399

Dedup

search_issues over open issues for aiInitialMessages / UIMessagePart / useObjectChat — 4 hits, all read: objectui#8378 (the outer cast, now landed), objectui#5605 and objectui#5919 (both maxToolRoundtrips), objectui#2443 (ADR-0057 handoff). None names the nested cast or the parts builder.

[os-justin]

Claim: session session_01YBWFb5YgMU5dw8p2VKj16S · branch claude/issue-8426-uimessage-parts-builder

PM dispatch (domain:ui seat). The assignee and this comment are set by the PM on the dev's behalf — the dev inherits both, posts no second claim, and never writes the assignee field.

Unblocked: objectui#8378 / PR #8401 has landed (verified by content — the outer } as any); is gone from useObjectChat.ts), so the file is free and the nested cast is now the only suppression on that call. ⚠️ Re-derive every line.

⛔ The fix is at the PRODUCER, not the consumer (AGENTS.md #0.1): build real UIMessagePart values in the useMemo, do not widen the cast.

⚠️ Establish first whether every branch of the builder can produce a declared part. The tool-${tool.toolName} template head is at least one dynamic member — if the SDK's part union cannot express it, that is a different and much larger conversation than a type annotation, and it is a product ruling: report the options costed and stop rather than reaching for a narrower cast in a new place.

⚠️ This card is load-bearing for objectui#8378's honest weaker claim. PR #8401 could only argue the outer cast was inert today — not for every instantiation — precisely because messages being any is what stops it yielding an inference candidate. Fixing this re-opens that question, so your report should say what the outer cast's status becomes once the builder is typed. If removing the nested cast makes the (already-removed) outer one load-bearing again, that is a finding worth stating loudly.

Instrument: type-check on both projects (tsc --noEmit && tsc -p tsconfig.test.json) — vitest transpiles types away. Prove your files are in the program you quote (--listFiles | grep -c) with a lit control. Dependents run downstream: pnpm --filter '...@object-ui/plugin-chatbot' type-check, scope line and per-package verdicts reported.

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[os-justin]

os-dev-report

Dispatch report for objectui#8426 — domain:ui dev seat, branch claude/issue-8426-uimessage-parts-builder, base ca3942729.

Outcome: needs_decision. No PR. The card's premise is CONFIRMED by measurement; the fix shape it names is blocked on a product ruling that is NOT the one the dispatch anticipated. Three things in the brief are contradicted below, two of them in the good direction.

1. Can every builder branch produce a declared part? NO — 7 of 10 authored tool states, not 10

Measured in packages/plugin-chatbot with the pinned ai@7.0.65 / @ai-sdk/react@4.0.68, one tsc --noEmit per push, part array declared as the derived SdkChatMessage['parts']:

builder branch	verdict
{ type: 'text', text } (:558)	builds
{ type: 'reasoning', text } (:561)	builds
tool part, state in input-streaming / input-available / output-available / output-error	builds
tool part, state in approval-requested / approval-responded / output-denied	TS2345 — not constructible
msg.parts passthrough (:548-553)	builds, once InitialMessage.parts is tightened — see 4

The three failures are one cause: those three arms of the SDK's UIToolInvocation require an approval envelope ({ id }, plus approved: boolean on approval-responded and approved: false on output-denied). ObjectUI's ChatToolInvocation — authoring (packages/types/src/complex.ts:921) and runtime (ChatbotEnhanced.tsx:218) — declares no such member, and normalizeMessages (:422) passes invocations through untouched, so the hook does not hold the data at any point.

Compiler transcript, the three failing pushes:

error TS2345: Argument of type '{ state: "approval-requested"; input: unknown; type: `tool-${string}`; toolCallId: string; }'
  is not assignable to parameter of type 'UIMessagePart(UIDataTypes, UITools)'.
error TS2345: ... '{ state: "approval-responded"; ... }' ...
error TS2345: ... '{ state: "output-denied"; ... }' ...

These three states are LIVE, not theoretical: packages/app-shell/src/console/ai/AiChatPage.tsx:147-152 (partToolState, declared :136) returns each of them verbatim from server-persisted parts, and that value reaches this builder through hydratedMessagesToChatMessages -> useObjectChat({ initialMessages }) on the console AI page. output-denied surviving that hop is pinned by AiChatPage.hydration.test.ts:44,49.

Every route around them is a shape the dispatch forbids: fabricate an approval.id (invented contract data, AGENTS.md #0.1), collapse the three onto a nearby expressible state (a visible chip regression — ChatbotEnhanced.tsx:1536-1540 gives each its own label, :2128 gates the Approve/Reject affordance on approval-requested), or park a narrower cast at the tool branch. So: options costed, stopping. See 7.

2. CONTRADICTED, good direction: the tool-${tool.toolName} template head is NOT the blocker

The issue and the claim comment both flag the dynamic member as the thing that might make this "a different and much larger conversation". Measured false. ToolUIPart parameterised by TOOLS maps over keyof TOOLS & string; with TOOLS = UITools = a Record from string to UITool, that key set is string, so the mapped type collapses to an index signature and the part's type is the template tool-${string}. This push compiles clean:

p.push({ type: `tool-${name}`, toolCallId: 'c', state: 'output-available', input: args, output: result });

with declare const name: string. A dynamic tool name is fully expressible. The blocker is the approval envelope, one member over.

Second thing neither the issue nor the brief names: toolName: tool.toolName (:567) is an excess property on a tool-* part — error TS2353: ... 'toolName' does not exist in type .... Only DynamicToolUIPart declares it. It is also dead on this path: the round-trip reader derives the name from type (mapMessages.ts:644-648) and reads p.toolName only for type === 'dynamic-tool'. So the fix must drop it, and dropping it is behaviour-preserving.

3. CONTRADICTED, good direction: typing the builder does NOT re-arm the removed outer cast

The brief asks this loudly, so here is the measurement rather than an argument. Four configurations of the real call shape (transport built exactly as useObjectChat builds it — new DefaultChatTransport({ ... }), no explicit type argument), each forced to print the inferred type by assigning .messages to 0:

config	inferred UI_MESSAGE
C1 messages is any (today's nested cast)	UIMessage(unknown, UIDataTypes, UITools)
C2 messages: SdkChatMessage[] (builder typed)	UIMessage(unknown, UIDataTypes, UITools)
C3 C2 plus the outer as any re-added	UIMessage(unknown, UIDataTypes, UITools)
C4 no messages at all	UIMessage(unknown, UIDataTypes, UITools)

Identical in all four, for messages and for setMessages. messages being any is not what makes the outer cast inert — transport typed as DefaultChatTransport parameterised by UIMessage(unknown, UIDataTypes, UITools) already pins UI_MESSAGE on its own, and the candidate messages would contribute once typed is that same type. So objectui#8378's claim is measurably STRONGER than it claimed: the outer cast's inference leg is inert independent of the builder, and typing the builder does not re-open it. What the outer cast really switched off — checking of transport, onError and excess properties, as the comment at :704-711 says — is unaffected either way and stays a good reason not to bring it back.

4. The passthrough branch: a second, unreported source of the same TS2322

The issue names only the synthesized parts array (:556). The msg.parts passthrough at :548-553 is an independent source of the identical error: InitialMessage.parts is declared as an Array of Record(string, unknown) at :240.

It is typeable at the PRODUCER with zero in-repo breakage. Tightening :240 to the derived parts?: SdkChatMessage['parts'] left the main program with only the two tool-state errors — the passthrough branch itself went silent. Neither in-repo producer breaks, because neither ever sets parts: renderer.tsx:79,268,406 passes schema.messages and the authoring ChatMessage declares no parts; AiChatPage.tsx:1608-1610 passes hydratedMessagesToChatMessages(...), whose return literal (:226-232) is { id, role, content, toolInvocations?, buildProgress? }. So the passthrough branch is unreachable from every in-repo call site and is fed only by external hosts through the published UseObjectChatOptions.

5. Instruments

Both type-check projects, packages/plugin-chatbot, baseline on ca3942729:

pnpm exec tsc --noEmit                 -> exit 0
pnpm exec tsc -p tsconfig.test.json    -> exit 0

Program membership, --listFiles with a lit control on each side (grep counts):

pattern	main program (1619 files)	test program (1877 files)
src/useObjectChat.ts	1	1
src/mapMessages.ts (positive control)	1	—
useObjectChat.honestMessages.test.tsx	0	1

The 0 in the main program is a real absence, not a broken pattern: the same pattern returns 1 against the test program's file list. useObjectChat.ts is in BOTH programs, so both quoted verdicts are about the file under discussion — objectui#8342's "red only in the test program" trap does not apply here.

Premise verification (ablation of the suppression, not of a fix — there is no fix to ablate). On the pristine HEAD file, mutation and restore both by state:

H0 (HEAD blob)            = 0c3c0da6259ba6725ccb6540a1185428d16a0372
H1 (nested cast removed)  = a257fab852ff9baaa88f47f6646fad91ef67d26a     MUTATION LANDED
  grep '(aiInitialMessages as any)'          -> 0   (was 1)
  grep 'aiInitialMessages : undefined,'      -> 1

Both programs turned red, one diagnostic each, named:

src/useObjectChat.ts(712,5): error TS2322: Type '{ id: string; role: "user" | "assistant" | "system"; parts: Record(string, unknown)[]; }[] | undefined'
  is not assignable to type 'UIMessage(unknown, UIDataTypes, UITools)[] | undefined'.
  ...
    Type 'Record(string, unknown)' is not assignable to type 'UIMessagePart(UIDataTypes, UITools)'.

Restore verified by state, never by an exit code: git hash-object back to 0c3c0da6259ba6725ccb6540a1185428d16a0372, git diff HEAD empty, git status --porcelain empty. Trap on EXIT INT TERM with absolute paths throughout; the two exploratory probe files were removed and the same three checks re-run clean.

Line numbers re-derived on ca3942729. The issue's :704 is now :712 (post-PR #8401); :545 (the useMemo) still holds; the synthesized array is :556, the tool push :564-572, InitialMessage.parts :240. Whole-file as any count is 5 and is NOT a reading: :368 and :704-711 are prose (one of them naming the already-removed chatResult as any), leaving two real casts — :712 (this card) and :816 (aiMessages[idx] as any, untouched, out of scope).

6. Other verdicts

• Dependents, downstream — pnpm --workspace-concurrency=2 --filter '...@object-ui/plugin-chatbot' type-check. Scope line: Scope: 7 of 47 workspace projects; the seven are @object-ui/plugin-chatbot, @object-ui/app-shell, @object-ui/console, @object-ui/site, @object-ui/example-schema-catalog, @object-ui/example-console-starter, @object-ui/example-byo-backend-console. All seven pass on the rebuilt closure — VERDICT command-exit 0 · held the lock 173s · waited 524s, zero error TS, zero Failed:

packages/plugin-chatbot          type-check: Done
examples/schema-catalog          type-check: Done
packages/app-shell               type-check: Done
apps/site                        type-check: Done
examples/console-starter         type-check: Done
apps/console                     type-check: Done
examples/byo-backend-console     type-check: Done

⚠ The FIRST run of this was a stale-dist false red exactly as the brief warned, and the warning was not wide enough to prevent it: --filter '@object-ui/plugin-chatbot^...' build builds only THIS package's closure, but the dependent set drags in @object-ui/layout, @object-ui/fields, plugin-dashboard, plugin-charts and eight more plugins that are not in it. examples/schema-catalog came back with 21 TS2882/TS2307 across untouched files. The closure that makes this readable is the union of the seven projects' own ^... closures (Scope: 36 of 47, all built clean).

• Changeset — not applicable: this run changes no file. Forward-looking, and worth ruling on WITH the options in 7: two of them narrow UseObjectChatOptions.initialMessages, a published input type, which is a type-level breaking change. The brief states this repo forbids major; that constraint should be settled before the fix is dispatched, not after it is written.
• Lint — not run: no changed file to lint.
• Tests — not run beyond type-check. vitest cannot see any of this (types are transpiled away), which is why every verdict above is tsc.
• Governed surface — no file touched, so nothing to classify.

7. The ruling this needs

⚠ The dispatch did not carry the four-axis decision frame, so per standing rules the options are costed below WITHOUT a per-axis analysis; please supply the frame (or rule directly).

The question: what should useObjectChat do with a tool invocation whose state is one of the AI SDK's three approval states, given ObjectUI's chat contract carries no approval envelope? Nothing else in this card is open.

• Option A — carry the envelope (recommended, and the only one that is contract-first). Add an optional approval to ChatToolInvocation in @object-ui/types (plus its Zod mirror and the parity test), mirror it on ChatbotEnhanced.ChatToolInvocation, lift it in mapMessages.extractToolInvocations and stop dropping it in hydratedMessagesToChatMessages (filed separately as objectui#8442), then build the discriminated arms and delete the cast. Cost: three packages, a published authoring-contract addition, a changeset. Evidence it is the right direction rather than an invention: partToolState already returns approval-responded and output-denied from server-persisted parts, which means the backend is producing SDK approval lifecycle states — so the envelope almost certainly exists in the payload ObjectUI is discarding, and the console AI page loses it on every reload today. Residual to rule on: a schema-AUTHORED invocation may still declare approval-requested with no envelope, so either the authoring state union sheds the three runtime-only states (ADR-0049 flavour) or the builder needs a documented answer for that case.
• Option B — derive the SDK state from the data instead of transliterating it (errorText -> output-error, output present -> output-available, else input-available), and let the round trip re-derive approval-requested from the result envelope, which mapMessages.ts:684-686 already does. Cost: one file, no contract change, no cross-package work — and a visible regression. approval-responded and output-denied would render as Completed instead of their own chips (ChatbotEnhanced.tsx:1536-1540) after a reload of the console AI page. It is also a consumer-side coercion, i.e. exactly the shape AGENTS.md #0.1 forbids, applied to work around a producer that drops data.
• Option C — close objectui#8426 as blocked-on-A. Zero cost, and the suppression stays live with the measurement recorded on the card. Honest, but it leaves a cast whose comment now understates the problem.
• Option D — a narrower cast at the tool branch only. Explicitly forbidden by the dispatch, listed only so the ruling is complete. It would also be the third time this call site's suppression is narrowed rather than removed (objectui#8342, objectui#8378, this).

Recommendation: A, sequenced behind objectui#8442, with the authoring-union residual ruled at the same time. If the residual is contentious, A minus the authoring narrowing still unblocks the console path and leaves only schema-authored approval states undecided.

8. Out-of-scope findings filed

• objectui#8442 — hydratedMessagesToChatMessages keeps the three SDK approval states but drops the approval envelope and pendingActionId that make them actionable. This is the direct blocker on this card, and independently a HITL gap: a rehydrated pending approval is not indexed by useHitlInChat (useHitlInChat.ts:157-167 skips invocations with no pendingActionId; the live path lifts it at mapMessages.ts:694). Reported at reading confidence, not browser-verified.
• objectui#8443 — the same useMemo casts an authored role: 'tool' to the SDK's three roles at :551 and :576, so in API mode a 'tool' role reaches the useChat store unfolded, while the package's own toRuntimeRole (the objectui#4399 decision) folds it at the render seam. Same defect class as this card, different member; filed rather than folded in because fixing it changes behaviour on the API-mode leg.

⚠ Two line citations inside objectui#8442's body are one to two lines stale (partToolState is declared at :136, not :135; the three approval cases are :147-152, not :146-151). The function names in that body are exact, so the references resolve; correcting them was not worth another API call. Corrected values are the ones in this report.

Neither is fixed here. Dedup: two targeted search_issues calls, both non-empty (so the channel answered), 7 hits total, all read, none naming either finding.

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[os-justin]

PM review — escalating to the maintainer, not ruling. No PR, and that is the correct outcome.

Why I am not ruling this one

Option A is the right shape and your evidence for it is strong: partToolState (AiChatPage.tsx:147-152) already returns approval-requested / approval-responded / output-denied verbatim from server-persisted parts, so the backend is producing SDK approval lifecycle states and the envelope almost certainly exists in the payload ObjectUI discards on every reload. That makes A a repair, not an invention.

But you flagged the thing that puts it above my line: A narrows UseObjectChatOptions.initialMessages, a published input type — a type-level breaking change — under a repo rule that forbids major. How this repo ships a breaking narrowing of a published input is a maintainer question, not a PM one, and it has to be settled before A is dispatched rather than discovered inside it. Into the decision box with the costs as you wrote them.

B is rejected independently of that: it is consumer-side coercion (AGENTS.md #0.1) and it carries a visible regression — approval-responded and output-denied would render as Completed instead of their own chips after a console AI page reload. D was forbidden by the dispatch and stays forbidden: a third narrowing of this call site's suppression is not its removal.

Two things you found that neither the card nor my brief named

• toolName at :567 is an excess property on a tool-* part (TS2353) and dead — mapMessages.ts:644-648 derives the name from type.
• The msg.parts passthrough at :548-553 is a second, independent source of the same TS2322, typeable at the producer with zero in-repo breakage.

⚠️ I considered carving these out as an unblocked partial and decided not to: the parts half is the same published-input narrowing that A is blocked on, so shipping it now would settle by stealth the question I am escalating. The toolName deletion alone is clean but not worth a PR on its own — it rides A.

You answered my loud question, and my prediction was wrong in the better direction

I asked what the removed outer cast's status becomes once the builder is typed, and predicted it might become load-bearing again. Measured: no. Four configurations of the real call shape all infer the same UI_MESSAGE, because transport pins it on its own — messages being any was never what made the outer cast inert, and a typed messages would contribute that same type as its candidate.

⇒ objectui#8378's weaker claim is measurably stronger than it claimed. I am recording that on objectui#8378 so the card can stay closed however this one is ruled.

And my other worry is also false: tool-${tool.toolName} is expressible — ToolUIPart over UITools collapses to an index signature whose part type is tool-${string} — so no product ruling is needed there. That removes one of the two escalation triggers my brief set up; the one that fired is the one I did not anticipate.

Process — my fault, twice now

You are right that this dispatch again carried no decision frame. That is the second time today and I said I would fix it after the first. Standing correction, effective now: any dispatch whose escalation fence I expect to fire ships with an explicit decision frame, or states that measured cost is the whole basis. For this card, measured cost was the whole basis and your costing is what I am forwarding.

Your two filed cards

objectui#8442 (the dropped approval envelope and pendingActionId — the direct blocker here, and independently a HITL gap) and objectui#8443 (an authored role: 'tool' reaching the store unfolded in API mode) are both labelled and queued. objectui#8442 is the sequencing dependency for A and is noted as such.

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