[pcbeingused333]

Why: The Workers AI streaming instrumentation (accumulateStreamingToolCalls) keyed every tool-call delta by toolCall.index ?? 0. OpenAI-compatible endpoints that omit index and send each parallel call whole in its own chunk therefore ended up as a single call: the first call's id and name, with the arguments of every call concatenated, and the other calls missing from gen_ai.response.tool_calls and gen_ai.output.messages. Same situation #25622 fixed for the OpenAI instrumentation.

Tool calls with a numeric index are grouped by it exactly as before. A delta without a usable index (missing or null) is kept in a separate list, in arrival order, so it can never collide with a real index: a delta whose id is already known continues that call, a new id (or a function name without an id) starts a new call, and anything else, such as an arguments fragment with neither, continues the latest one. Native and indexed streams (including the top-level name/arguments shape) behave as before.

How to review: getUnindexedToolCall and the ToolCallAccumulator split in packages/server-utils/src/ai/workers-ai/streaming.ts; the three new cases in workers-ai-streaming.test.ts (two parallel calls without an index stay separate, argument fragments of one unindexed call are merged, an unindexed call does not merge into an indexed call at index: 0). The first and third fail without the change; the whole test/ai/lib/tracing folder passes.

Unsure about: whether an unindexed delta with neither id nor name should continue the latest call (chosen here, mirrors #25622) or be dropped.

Closes: no linked issue; same class of bug as #25622.

This change was prepared with the assistance of an AI coding agent (Claude).

[JosephDoUrden]

read b403a7a against #25622 and ran instrumentWorkersAiStream from a copy with stubbed sentry imports, head vs develop, 8 delta shapes. no index and index: null parallel calls: 2 calls, develop gave 1. normal indexed stream unchanged. repo suite not run.

one gap at streaming.ts:71, it does not fully match #25622. index: 0 on every call with new ids still merges into 1 call. {index: 0, id, name} then an args fragment with no index or id now gives 2 calls, nameless one holds the args, develop gave 1. no index then indexed comes out reversed.

worth fixing before merge.

[pcbeingused333]

Thanks @JosephDoUrden, good catch. Pushed 2725da7, which ports the same accumulator the OpenAI integration uses (getToolCallKey in #25622), so Workers AI streams now behave the same way:

• index: 0 with a new id starts a new tool call instead of merging into the previous one.
• An argument fragment with no index/id is appended to the call it belongs to, so the name is no longer empty with the args split off.
• Calls are emitted in stream order.

I added tests for the three cases; they failed before the change and pass now.

This comment was drafted with Claude Code.

[pcbeingused333]

Thanks @JosephDoUrden, good catch. Pushed a follow-up that ports the accumulator logic from the OpenAI integration (#25622) to the Workers AI streaming path:

• {index: 0} with a new id now starts a new tool call instead of merging into the previous one.
• An argument fragment with no index/id is appended to the call currently being built, so the name and arguments stay together.
• Calls keep the order in which they arrived.

I added tests for these three cases; the suite passes locally.

This comment was drafted with Claude Code.