From 287041e39e93b368646f0fe8298b65feab692acc Mon Sep 17 00:00:00 2001
From: Tianyi Cui <53024+tianyicui@users.noreply.github.com>
Date: Tue, 14 Jul 2026 12:35:25 +0800
Subject: [PATCH] fix: preserve malformed snapshot fixtures

---
 packages/support/acp-snapshot/src/suite.ts | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/packages/support/acp-snapshot/src/suite.ts b/packages/support/acp-snapshot/src/suite.ts
index 4d87093c8a..906521c42d 100644
--- a/packages/support/acp-snapshot/src/suite.ts
+++ b/packages/support/acp-snapshot/src/suite.ts
@@ -486,8 +486,10 @@ export function defineAcpSnapshotSuite(options: SnapshotSuiteOptions): void {
             const entries = await readdir(dir, { withFileTypes: true })
             await Promise.all(entries
               .filter(entry => entry.isFile()
-                && entry.name.startsWith('session.')
-                && entry.name.endsWith('.jsonl')
+                // Only valid numbered children are record-owned stale output.
+                // Malformed session-like names stay for the inventory guard to
+                // reject instead of being silently deleted during mutation.
+                && /^session\.[1-9]\d*\.jsonl$/.test(entry.name)
                 && !outputNames.has(entry.name))
               .map(entry => rm(join(dir, entry.name))))
             fixtureFiles = outputFixtureFiles