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fix(core): skip skill context when locating invoking turns #68

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Merged
K-Mistele merged 1 commit into from
Aug 15, 2026
Merged

fix(core): skip skill context when locating invoking turns #68

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16 changes: 14 additions & 2 deletions packages/agentlayer-core/src/tools/subagent-fork.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -16,13 +16,24 @@ function invokesToolCall(message: ModelMessage, toolCallId: string): boolean {
)
}

function isInjectedSkillMessage(message: ModelMessage): boolean {
if (message.role !== 'user' || typeof message.content !== 'string') return false
const content = message.content.trim()
return /^<skill(?:\s|>)/.test(content) && content.endsWith('</skill>')
}

function isUserTurnBoundary(message: ModelMessage): boolean {
return message.role === 'user' && !isInjectedSkillMessage(message)
}

function removeInvokingTurn(messages: ReadonlyArray<ModelMessage>, toolCallId: string): ModelMessage[] {
const invokingAssistantIndex = messages.findIndex((message) => invokesToolCall(message, toolCallId))
if (invokingAssistantIndex < 0) return [...messages]

let triggeringUserIndex = -1
for (let index = invokingAssistantIndex - 1; index >= 0; index--) {
if (messages[index]?.role === 'user') {
const message = messages[index]
if (message && isUserTurnBoundary(message)) {
triggeringUserIndex = index
break
}
Expand All @@ -46,7 +57,8 @@ function isEligibleForkMessage(message: ModelMessage): boolean {
function selectRecentTurns(messages: ModelMessage[], turns: number): ModelMessage[] {
let userTurns = 0
for (let index = messages.length - 1; index >= 0; index--) {
if (messages[index]?.role !== 'user') continue
const message = messages[index]
if (!message || !isUserTurnBoundary(message)) continue
userTurns += 1
if (userTurns === turns) return messages.slice(index)
}
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27 changes: 27 additions & 0 deletions packages/agentlayer-core/test/subagent-tool.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -823,6 +823,33 @@ describe('forking subagent tool', () => {
expect(projectForkMessages(messages, 'none', 'spawn-call')).toEqual([])
})

test('does not treat an injected skill message as the invoking user turn boundary', () => {
const messages: ModelMessage[] = [
{ role: 'user', content: 'old request' },
{ role: 'assistant', content: [{ type: 'text', text: 'old answer' }] },
{ role: 'user', content: 'actual triggering request' },
{
role: 'user',
content: '<skill name="investigate" baseDir="/skills/investigate">\nInvestigate carefully.\n</skill>',
},
{
role: 'assistant',
content: [
{ type: 'tool-call', toolCallId: 'spawn-call', toolName: 'subagent', input: { prompt: 'work' } },
],
},
]

expect(projectForkMessages(messages, 'all', 'spawn-call')).toEqual([
{ role: 'user', content: 'old request' },
{ role: 'assistant', content: [{ type: 'text', text: 'old answer' }] },
])
expect(projectForkMessages(messages, 1, 'spawn-call')).toEqual([
{ role: 'user', content: 'old request' },
{ role: 'assistant', content: [{ type: 'text', text: 'old answer' }] },
])
})

test('constructs isolated fork state without caller tool, pending, child, or context state', () => {
const caller: AgentState = {
messages: [{ role: 'user', content: { nested: ['original'] } } as any],
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