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fix(voice): preserve toolsets during LLM tool sync #1752

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fix(voice): preserve toolsets during LLM tool sync #1752

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5 changes: 5 additions & 0 deletions .changeset/steady-toolsets-handoff.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
'@livekit/agents': patch
---

Preserve toolset grouping when syncing LLM-mutated tools during voice generation.
32 changes: 32 additions & 0 deletions agents/src/llm/tool_context.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -439,13 +439,23 @@ export class ToolContext<UserData = UnknownUserData> {
}

updateTools(tools: readonly ToolContextEntry<UserData>[]): void {
this._updateTools(tools);
}

private _updateTools(
tools: readonly ToolContextEntry<UserData>[],
exclude: readonly Tool[] = [],
): void {
this._tools = [...tools];
this._functionToolsMap = new Map();
this._providerTools = [];
this._toolsets = [];
const excludedTools = new Set(exclude);

// eslint-disable-next-line @typescript-eslint/no-explicit-any -- accepts any tool shape
const addTool = (tool: any): void => {
if (excludedTools.has(tool)) return;

if (isToolset(tool)) {
for (const inner of tool.tools) {
addTool(inner);
Expand Down Expand Up @@ -479,6 +489,28 @@ export class ToolContext<UserData = UnknownUserData> {
}
}

/**
* Apply in-place edits of a flattened tool list while preserving Toolset grouping.
*
* Added tools become top-level entries; removed Toolset members stay owned by their toolset
* for lifecycle purposes, but are excluded from this context's callable/provider lookups.
*
* @internal
*/
_syncFlattened(
tools: readonly Tool[],
structuredTools: readonly ToolContextEntry<UserData>[] = this._tools,
): void {
const current = new ToolContext<UserData>(structuredTools).flatten();
const currentTools = new Set(current);
const nextTools = new Set(tools);
const added = tools.filter((tool) => !currentTools.has(tool));
const removed = current.filter((tool) => !nextTools.has(tool));

const structured = structuredTools.filter((tool) => !removed.some((r) => tool === r));
this._updateTools([...structured, ...(added as ToolContextEntry<UserData>[])], removed);
}
Comment on lines +500 to +512

@devin-ai-integration devin-ai-integration Bot Jun 11, 2026

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🚩 _tools inconsistency with _functionToolsMap after exclusion-based sync

After _syncFlattened excludes Toolset members (the removal scenario), _tools still contains Toolsets whose .tools arrays include the excluded members, but _functionToolsMap does not. This means new ToolContext(toolCtx.tools) would re-include excluded tools and new ToolContext(toolCtx.tools).equals(toolCtx) would return false. This inconsistency is explicitly documented in the _syncFlattened docstring ("removed Toolset members stay owned by their toolset for lifecycle purposes, but are excluded from this context's callable/provider lookups"). However, it could interact with onToolsetToolsChanged at agents/src/voice/agent_activity.ts:4210 — that method creates new ToolContext(current.tools) and checks .equals(current), so it would detect a difference and call updateTools(current.tools), potentially re-adding tools that were intentionally excluded. This is only triggered when a dynamic Toolset pushes new tools, which is unlikely to happen during active LLM inference, but worth being aware of.

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Comment on lines +500 to +512

@devin-ai-integration devin-ai-integration Bot Jun 11, 2026

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🚩 No test coverage for _syncFlattened

The new _syncFlattened method has no unit tests in tool_context.test.ts. The method handles non-trivial logic (identity-based diff, Toolset preservation, exclusion mechanism) and would benefit from test cases covering: (1) no-op when tools unchanged, (2) tool added by LLM node, (3) tool removed from a Toolset, (4) top-level tool removed, (5) tool replaced with different instance same name. The existing test suite thoroughly covers ToolContext and Toolset behavior but doesn't exercise _syncFlattened or the exclude parameter of _updateTools.

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copy(): ToolContext<UserData> {
return new ToolContext<UserData>([...this._tools]);
}
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3 changes: 3 additions & 0 deletions agents/src/voice/generation.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -503,7 +503,9 @@ export function performLLMInference(
let firstTokenReceived = false;

try {
const structuredTools = toolCtx.tools;
llmStream = await node(chatCtx, toolCtx, modelSettings);
toolCtx._syncFlattened(toolCtx.flatten(), structuredTools);
if (llmStream === null) {
await textWriter.close();
return;
Expand Down Expand Up @@ -540,6 +542,7 @@ export function performLLMInference(
}

if (chunk.delta.toolCalls) {
toolCtx._syncFlattened(toolCtx.flatten(), structuredTools);
for (const tool of chunk.delta.toolCalls) {
if (tool.type !== 'function_call') continue;

Expand Down