fix(ai): routed llama.cpp parallel tool calls by item.call_id

llama.cpp's /v1/responses emits function_call `output_item.added` with
only `item.call_id` (no `item.id`, no `output_index`); the matching
`function_call_arguments.delta` carries `item_id: "fc_<call_id>"`.
`processResponsesStream` keyed its lookup map by `item.id` only, so
the registry stayed empty and every delta fell back to `lastOpenItem`
— the most recently added block. With N parallel calls, N-1 of them
finalized with arguments `{}` and the agent rejected them with
`path: Invalid input: expected string, received undefined`, while the
trailing call hoarded every delta.

Register function-call and custom-tool-call items under `item.call_id`
as a secondary key alongside `item.id`/`output_index`, and look up by
the same fallback in `output_item.done`. Real OpenAI is unaffected
(distinct keys, both populated). Regression test pins the exact
llama.cpp emission shape.

Fixes #2015

packages/ai/CHANGELOG.md

@@ -17,6 +17,7 @@
 ### Fixed
 
 - Fixed Anthropic-compatible reasoning endpoints losing prior-turn reasoning on continuation requests when they emit unsigned `thinking` blocks. `convertAnthropicMessages` treated unknown endpoints as signature-enforcing and demoted unsigned reasoning to `type: "text"`, which destabilized tool-call argument serialization on the next turn — the upstream symptom behind the `args?.ops?.map is not a function` crash reported against the `todo` tool. Official `api.anthropic.com` keeps the conservative text fallback; non-official `anthropic-messages` reasoning models now replay unsigned reasoning as native `type: "thinking"` ([#2005](https://github.com/can1357/oh-my-pi/issues/2005)).
+- Fixed parallel `function_call` items losing arguments against llama.cpp's OpenAI Responses endpoint (`/v1/responses`), where every call but the last finalized with `{}` and the agent rejected them with `path: Invalid input: expected string, received undefined`. llama.cpp's `to_json_oaicompat_resp` emits `output_item.added` with only `item.call_id` (no `item.id`, no `output_index`) while the matching `function_call_arguments.delta` carries `item_id: "fc_<call_id>"`. `processResponsesStream` now registers function-call and custom-tool-call items under `item.call_id` as a secondary lookup key (alongside `item.id`/`output_index`) so identifier-deviant hosts route deltas and done events to the right block. ([#2015](https://github.com/can1357/oh-my-pi/issues/2015))
 
 ## [15.9.67] - 2026-06-06
 

packages/ai/src/providers/openai-responses-shared.ts

@@ -459,6 +459,13 @@ export async function processResponsesStream<TApi extends Api>(
 	// see https://github.com/can1357/oh-my-pi/issues/1880 — llama.cpp emits parallel
 	// function_call deltas interleaved, and a singleton `current` reference would
 	// fold them into the wrong block and drop arguments on every call but the last.
+	//
+	// llama.cpp's `to_json_oaicompat_resp` (issue #2015) compounds this: `output_item.added`
+	// for function_call/custom_tool_call carries `item.call_id` but no `item.id` and no
+	// `output_index`, while the matching `function_call_arguments.delta` carries
+	// `item_id = "fc_<call_id>"`. Registering function-call items by `call_id` as a
+	// secondary key lets the delta lookup find the right block on hosts that emit one
+	// identifier but not the other.
 	const openItemsByOutputIndex = new Map<number, StreamingItem>();
 	const openItemsByItemId = new Map<string, StreamingItem>();
 	let lastOpenItem: StreamingItem | null = null;
@@ -468,9 +475,11 @@ export async function processResponsesStream<TApi extends Api>(
 		outputIndex: number | undefined,
 		itemId: string | undefined,
 		entry: StreamingItem,
+		alternateItemKey?: string,
 	): void => {
 		if (typeof outputIndex === "number") openItemsByOutputIndex.set(outputIndex, entry);
 		if (itemId) openItemsByItemId.set(itemId, entry);
+		if (alternateItemKey && alternateItemKey !== itemId) openItemsByItemId.set(alternateItemKey, entry);
 		openItemsInOrder.push(entry);
 		lastOpenItem = entry;
 	};
@@ -508,9 +517,11 @@ export async function processResponsesStream<TApi extends Api>(
 		outputIndex: number | undefined,
 		itemId: string | undefined,
 		entry: StreamingItem | undefined,
+		alternateItemKey?: string,
 	): void => {
 		if (typeof outputIndex === "number") openItemsByOutputIndex.delete(outputIndex);
 		if (itemId) openItemsByItemId.delete(itemId);
+		if (alternateItemKey && alternateItemKey !== itemId) openItemsByItemId.delete(alternateItemKey);
 		if (entry) {
 			const index = openItemsInOrder.indexOf(entry);
 			if (index >= 0) openItemsInOrder.splice(index, 1);
@@ -550,7 +561,7 @@ export async function processResponsesStream<TApi extends Api>(
 					partialJson: item.arguments || "",
 				};
 				output.content.push(block);
-				registerOpenItem(event.output_index, item.id, { item, block });
+				registerOpenItem(event.output_index, item.id, { item, block }, item.call_id);
 				stream.push({ type: "toolcall_start", contentIndex: contentIndexOf(block), partial: output });
 			} else if (item.type === "custom_tool_call") {
 				const block: StreamingToolCallBlock = {
@@ -568,7 +579,7 @@ export async function processResponsesStream<TApi extends Api>(
 					partialJson: item.input ?? "",
 				};
 				output.content.push(block);
-				registerOpenItem(event.output_index, item.id, { item, block });
+				registerOpenItem(event.output_index, item.id, { item, block }, item.call_id);
 				stream.push({ type: "toolcall_start", contentIndex: contentIndexOf(block), partial: output });
 			}
 		} else if (event.type === "response.reasoning_summary_part.added") {
@@ -709,7 +720,10 @@ export async function processResponsesStream<TApi extends Api>(
 		} else if (event.type === "response.output_item.done") {
 			const item = structuredCloneJSON(event.item);
 			options?.onOutputItemDone?.(item);
-			const entry = lookupOpenItem({ output_index: event.output_index, item_id: item.id });
+			const entry =
+				item.type === "function_call" || item.type === "custom_tool_call"
+					? lookupOpenItem({ output_index: event.output_index, item_id: item.id ?? item.call_id })
+					: lookupOpenItem({ output_index: event.output_index, item_id: item.id });
 			if (item.type === "reasoning") {
 				const thinking =
 					item.summary?.length > 0
@@ -768,7 +782,7 @@ export async function processResponsesStream<TApi extends Api>(
 					delete (block as { argumentsDone?: boolean }).argumentsDone;
 				}
 				const contentIndex = block ? contentIndexOf(block) : output.content.length - 1;
-				closeOpenItem(event.output_index, item.id, entry);
+				closeOpenItem(event.output_index, item.id, entry, item.call_id);
 				stream.push({ type: "toolcall_end", contentIndex, toolCall, partial: output });
 			} else if (item.type === "custom_tool_call") {
 				const block = entry?.block.type === "toolCall" ? entry.block : undefined;
@@ -781,7 +795,7 @@ export async function processResponsesStream<TApi extends Api>(
 					customWireName: item.name,
 				};
 				const contentIndex = block ? contentIndexOf(block) : output.content.length - 1;
-				closeOpenItem(event.output_index, item.id, entry);
+				closeOpenItem(event.output_index, item.id, entry, item.call_id);
 				stream.push({ type: "toolcall_end", contentIndex, toolCall, partial: output });
 			}
 		} else if (event.type === "response.completed") {

packages/ai/test/openai-responses-parallel-tool-calls.test.ts

@@ -260,4 +260,79 @@ describe("processResponsesStream: parallel function_call items", () => {
 		expect(byCallId.get("call_a")?.toolCall.arguments).toEqual({ command: "printf a" });
 		expect(byCallId.get("call_b")?.toolCall.arguments).toEqual({ command: "printf b" });
 	});
+
+	test("routes deltas by item.call_id when llama.cpp omits item.id and output_index (issue #2015)", async () => {
+		// llama.cpp's `to_json_oaicompat_resp` (tools/server/server-task.cpp) emits a
+		// function_call's `output_item.added` with only `item.call_id` — no `item.id`,
+		// no `output_index`. The matching `function_call_arguments.delta` then carries
+		// `item_id: "fc_<call_id>"` and again no `output_index`. Without secondary
+		// indexing on `call_id`, `processResponsesStream`'s lookup map stays empty and
+		// every delta lands on the trailing block, leaving earlier calls with empty
+		// arguments (= `{}`) — the read tool then rejects them with
+		// `path: Invalid input: expected string, received undefined`.
+		const output = makeOutput();
+		const emitted: EmittedEvent[] = [];
+		const stream = { push: (e: unknown) => emitted.push(e as EmittedEvent), end: () => {} } as never;
+
+		const argsA = JSON.stringify({ path: "a.txt" });
+		const argsB = JSON.stringify({ path: "b.txt" });
+		const argsC = JSON.stringify({ path: "c.txt" });
+
+		await processResponsesStream(
+			makeStream([
+				{
+					type: "response.output_item.added",
+					item: { type: "function_call", call_id: "fc_a", name: "read", arguments: "" },
+				},
+				{
+					type: "response.output_item.added",
+					item: { type: "function_call", call_id: "fc_b", name: "read", arguments: "" },
+				},
+				{
+					type: "response.output_item.added",
+					item: { type: "function_call", call_id: "fc_c", name: "read", arguments: "" },
+				},
+				{ type: "response.function_call_arguments.delta", item_id: "fc_a", delta: argsA },
+				{ type: "response.function_call_arguments.delta", item_id: "fc_b", delta: argsB },
+				{ type: "response.function_call_arguments.delta", item_id: "fc_c", delta: argsC },
+				{
+					type: "response.output_item.done",
+					item: { type: "function_call", call_id: "fc_a", name: "read", arguments: argsA },
+				},
+				{
+					type: "response.output_item.done",
+					item: { type: "function_call", call_id: "fc_b", name: "read", arguments: argsB },
+				},
+				{
+					type: "response.output_item.done",
+					item: { type: "function_call", call_id: "fc_c", name: "read", arguments: argsC },
+				},
+			]),
+			output,
+			stream,
+			makeModel(),
+		);
+
+		expect(output.content).toHaveLength(3);
+		const [a, b, c] = output.content;
+		if (a?.type !== "toolCall" || b?.type !== "toolCall" || c?.type !== "toolCall") {
+			throw new Error("expected toolCalls");
+		}
+		expect(a.arguments).toEqual({ path: "a.txt" });
+		expect(b.arguments).toEqual({ path: "b.txt" });
+		expect(c.arguments).toEqual({ path: "c.txt" });
+
+		const ends = emitted.filter(e => e.type === "toolcall_end") as Array<{
+			toolCall: { id: string; arguments: Record<string, unknown> };
+			contentIndex: number;
+		}>;
+		expect(ends).toHaveLength(3);
+		const byCallId = new Map(ends.map(e => [e.toolCall.id.split("|")[0], e]));
+		expect(byCallId.get("fc_a")?.toolCall.arguments).toEqual({ path: "a.txt" });
+		expect(byCallId.get("fc_b")?.toolCall.arguments).toEqual({ path: "b.txt" });
+		expect(byCallId.get("fc_c")?.toolCall.arguments).toEqual({ path: "c.txt" });
+		expect(byCallId.get("fc_a")?.contentIndex).toBe(0);
+		expect(byCallId.get("fc_b")?.contentIndex).toBe(1);
+		expect(byCallId.get("fc_c")?.contentIndex).toBe(2);
+	});
 });