fix(hooks): merge surfaces the WINNING decision's reason, not only deny's

mergeHookOutputs collected reasons only from rank-3 (deny/block) hooks, so an
ask-winning outcome lost its reason — a bridge mapping an `ask` decision to a
PreToolDecision had no reason to attach. Collect reasons per rank and emit the
ones explaining the winning decision: a deny-winning fold shows deny reasons, an
ask-winning fold shows ask reasons, allow contributes none. Found while building
the hooks-claude bridge's PreToolUse `ask` path.
This commit is contained in:
Tianyi Cui
2026-07-01 02:20:12 +08:00
parent c658f4d155
commit c28d6b837b
2 changed files with 29 additions and 4 deletions

View File

@@ -74,7 +74,11 @@ function decisionForRank(maxRank: number): MergedDecision {
*/
export function mergeHookOutputs(outputs: HookOutput[]): MergedHookOutcome {
let maxRank = 0
const reasons: string[] = []
// Reasons collected PER RANK, so the merged reason can be the one explaining
// the WINNING decision (a deny-winning outcome surfaces deny reasons; an
// ask-winning outcome surfaces ask reasons). An `allow`'s reason is never an
// objection the model needs, so rank 1 collects none.
const reasonsByRank = new Map<number, string[]>()
let stop = false
let stopReason: string | undefined
const additionalContext: string[] = []
@@ -83,9 +87,11 @@ export function mergeHookOutputs(outputs: HookOutput[]): MergedHookOutcome {
for (const out of outputs) {
const r = rank(out.decision)
if (r > maxRank) maxRank = r
// Collect a reason only from a blocking/denying hook (rank 3) — an allow's
// "reason" is not an objection the model needs to see.
if (r === 3 && out.reason !== undefined && out.reason.length > 0) reasons.push(out.reason)
if ((r === 3 || r === 2) && out.reason !== undefined && out.reason.length > 0) {
const list = reasonsByRank.get(r) ?? []
list.push(out.reason)
reasonsByRank.set(r, list)
}
if (out.continue === false && !stop) {
stop = true
if (out.stopReason !== undefined) stopReason = out.stopReason
@@ -98,6 +104,7 @@ export function mergeHookOutputs(outputs: HookOutput[]): MergedHookOutcome {
}
}
const reasons = reasonsByRank.get(maxRank) ?? []
return {
decision: decisionForRank(maxRank),
...reasons.length > 0 ? { reason: reasons.join('\n\n') } : {},

View File

@@ -47,6 +47,24 @@ describe('mergeHookOutputs — reasons, stop, context, systemMessages accumulate
expect(mergeHookOutputs([out({ decision: 'allow' })]).reason).toBeUndefined()
})
it('surfaces the reason of the WINNING decision: an ask-winning outcome shows the ask reason', () => {
const m = mergeHookOutputs([
out({ decision: 'allow', reason: 'allow reason — not surfaced' }),
out({ decision: 'ask', reason: 'needs approval' }),
])
expect(m.decision).toBe('ask')
expect(m.reason).toBe('needs approval')
})
it('when deny wins over ask, the ask reasons are dropped (only the winning rank\'s reasons)', () => {
const m = mergeHookOutputs([
out({ decision: 'ask', reason: 'ask reason — not surfaced once deny wins' }),
out({ decision: 'deny', reason: 'the real objection' }),
])
expect(m.decision).toBe('deny')
expect(m.reason).toBe('the real objection')
})
it('stop is sticky on the first continue:false, capturing its stopReason', () => {
const m = mergeHookOutputs([
out({ continue: true }),