fix(server-utils): Keep Workers AI streamed tool calls that have no index by pcbeingused333 · Pull Request #25835 · getsentry/sentry-javascript

pcbeingused333 · 2026-10-28T15:41:56Z

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).

…ndex Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

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.

…dling Reuse the id/index grouping of the OpenAI streaming accumulator: a new id on a taken index opens a new call, argument fragments without index or id continue the latest call, and calls keep their arrival order. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

pcbeingused333 · 2026-11-07T14:06:45Z

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 · 2026-11-07T14:07:48Z

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.

RulaKhaled

Thank you for working on this! A few comments to look at.

also, which model sends tool calls without index? cloudflare's own workers-ai-provider keys them by index ?? 0 and its docs show index on every chunk that carries a name or arguments, so I'd like to see a captured stream before we handle more no-index shapes.
if there isn't one, this is a guard for openai-compatible routes rather than a workers ai fix and the PR description should say so. the description also still mentions getUnindexedToolCall and "three new cases", both out of date.

RulaKhaled · 2026-11-11T10:23:52Z

+    return undefined;
+  };
+
+  if (typeof toolCall.index === 'number') {


m: the reverse order still splits: {id:'c1',...} then {index:0,id:'c1',function:{arguments:'1}'}} records two c1 entries, develop merged them. checking findById before opening a new index-N key fixes the id case. #25622 has the same gap so worth fixing in both if you extract the helper.

RulaKhaled · 2026-11-11T10:23:54Z

-      accumulator[index] = {
-        index,
+      accumulator.calls.set(key, {
+        index: toolCall.index ?? accumulator.calls.size,


m: index: toolCall.index ?? calls.size still writes an index the provider never sent. with mixed streams it collides, e.g. unindexed cb then indexed ca both record index: 0. I'd keep whatever the provider sent, like #25622 does. the first new test will need updating since it expects index: 0 and index: 1.

RulaKhaled · 2026-11-11T10:23:55Z

+
+  it('does not merge a tool call without an index into one that has the same index number', async () => {
+    const { span, attributes } = createMockSpan();
+    const chunks = [


m: the new tests still only check gen_ai.response.tool_calls. can one of them assert gen_ai.output.messages too, since that's what the product reads? also missing index: null and an id that continues a call without an index. #25622's tests port over almost as is.

RulaKhaled · 2026-11-11T10:23:56Z

+ * Some providers omit the index and send each parallel call whole: a known `id` continues that call, a new `id` (or
+ * a name without an id) starts a new call, and anything else continues the latest one.
+ */
+function getToolCallKey(


h: this is now getToolCallKey from openai/streaming.ts almost verbatim. can it move to ai/core and be shared? it only needs the calls map, keyByIndex and the last key, which openai's state already has, so each caller just passes in the normalized name.

RulaKhaled · 2026-11-11T10:23:57Z

+      return known;
+    }
+  }
+  if (toolCall.id || name || accumulator.lastKey === undefined) {


m: one more limit worth naming in the description: with no index and no id, {name:'a',arguments:'{"x":'} then {name:'a',arguments:'1}'} records two calls with half the args each. same for a nameless opener whose id arrives later. develop gave one call for both, by accident since it merged everything into index 0, so these shapes do get worse. #25622 behaves the same and I wouldn't add a heuristic unless a model actually streams like this.

pcbeingused333 · 2026-11-11T14:00:43Z

The key selection now lives in ai/core and is shared by Workers AI and OpenAI. A known id is resolved before a numeric index opens a new call, and Workers AI preserves the original index instead of synthesizing one. Tests cover the unindexed-to-indexed transition, null indices, a returning id after another call opens, and gen_ai.output.messages. The description also names the ambiguous shapes without adding heuristics.

This comment was drafted with Claude Code.

fix(server-utils): Keep Workers AI streamed tool calls that have no i…

b403a7a

…ndex Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

pcbeingused333 requested a review from a team as a code owner October 28, 2026 15:41

pcbeingused333 requested review from isaacs and mydea and removed request for a team October 28, 2026 15:41

github-actions Bot added the external PR from an external contributor label Oct 28, 2026

RulaKhaled self-requested a review October 29, 2026 13:33

JosephDoUrden reviewed Nov 7, 2026

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RulaKhaled reviewed Nov 11, 2026

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fix(server-utils): share streamed tool call identity handling

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pcbeingused333 requested a review from a team November 11, 2026 13:58

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fix(server-utils): Keep Workers AI streamed tool calls that have no index - #25835

fix(server-utils): Keep Workers AI streamed tool calls that have no index#25835
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