diff --git a/packages/test-support/session-snapshot/src/suite.ts b/packages/test-support/session-snapshot/src/suite.ts
index 9c0679ecf2..fc951e1118 100644
--- a/packages/test-support/session-snapshot/src/suite.ts
+++ b/packages/test-support/session-snapshot/src/suite.ts
@@ -22,6 +22,7 @@ import { readFile, readdir, writeFile } from 'node:fs/promises'
 import { existsSync } from 'node:fs'
 import { join } from 'node:path'
 import { isSurfaceEligibleType } from '@deepseek-ai/dsh-session/surface'
+import { SESSION_FORMAT_VERSION } from '@deepseek-ai/dsh-session'
 import { describe, expect, it } from 'vitest'
 import { type AgentUnderTest, type HarvestedLog, type InputScript, runScenario } from './harness.ts'
 import {
@@ -1146,19 +1147,24 @@ export function stabilizeRefreshLog(
 }
 
 /**
- * Check the selected generation of every parent and child fixture against storage policy.
+ * Check every selected role for tool/path defects and current generations for canonical prompt/identity storage.
+ * Historical roles retain their released bytes, including roles retired by the current writer.
  * @param dir Scenario directory containing canonical Session fixtures.
  * @param scenarioName Scenario name used in failure diagnostics.
  * @returns Resolves when all selected fixtures satisfy the storage checks.
  */
 export async function assertSessionFixtureStorage(dir: string, scenarioName: string): Promise<void> {
   const files = await sessionFixtures(dir)
+  const currentFixtures: string[] = []
   for (const file of files) {
     const fixture = await readFile(join(dir, file), 'utf8')
+    const version = assertSessionFixtureVersion(file, fixture)
     expect(unknownToolCallIds(fixture), `${scenarioName}/${file} contains UNKNOWN_TOOL`)
       .toEqual([])
     expect(fixture, `${scenarioName}/${file} carries a non-canonical macOS cwd token`)
       .not.toContain('/private{{cwd}}')
+    if (version !== SESSION_FORMAT_VERSION) continue
+    currentFixtures.push(fixture)
     expect(scrubSystemPrompts(fixture), `${scenarioName}/${file} carries an unscrubbed system prompt`)
       .toEqual(fixture)
     expect(scrubToolSchemas(fixture), `${scenarioName}/${file} carries unscrubbed tool schemas`)
@@ -1166,8 +1172,7 @@ export async function assertSessionFixtureStorage(dir: string, scenarioName: str
     expect(systemPromptPrecedesRequests(fixture), `${scenarioName}/${file} has a request/header with no preceding system/message`)
       .toBe(true)
   }
-  const fixtures = await Promise.all(files.map(file => readFile(join(dir, file), 'utf8')))
-  expect(redactSessionSnapshotIds(fixtures), `${scenarioName}: identity redaction fixed point`).toEqual(fixtures)
+  expect(redactSessionSnapshotIds(currentFixtures), `${scenarioName}: identity redaction fixed point`).toEqual(currentFixtures)
 }
 
 /**
diff --git a/packages/test-support/session-snapshot/tests/fixtures/record-suite/rec-child/session.1.v3.jsonl b/packages/test-support/session-snapshot/tests/fixtures/record-suite/rec-child/session.1.v3.jsonl
new file mode 100644
index 0000000000..eb7d5afea1
--- /dev/null
+++ b/packages/test-support/session-snapshot/tests/fixtures/record-suite/rec-child/session.1.v3.jsonl
@@ -0,0 +1,6 @@
+{"type":"session","version":3,"id":"{{session:2}}","createdAt":800,"cwd":"{{cwd}}","parentSession":"{{session:1}}","isSeeded":false,"delegationDepth":1}
+{"type":"turn/start","data":{"turn":1}}
+{"type":"step/start","data":{"turn":1,"step":1}}
+{"type":"system/message","data":{"turn":1,"step":1,"message":{"id":"{{message:1}}","role":"system","content":[{"type":"text","text":"{{system}}"}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt"}}},"surfaceOp":"append"}
+{"type":"request/header","data":{"header":{"config":{"provider":"fake","model":"fake"},"tools":"{{tools}}"},"reason":"initial"}}
+{"type":"user/message","data":{"role":"user","content":[{"type":"text","text":"same inherited message"}],"source":{"kind":"user"},"id":"{{message:2}}"},"surfaceOp":"append"}
diff --git a/packages/test-support/session-snapshot/tests/fixtures/record-suite/rec-child/session.v3.jsonl b/packages/test-support/session-snapshot/tests/fixtures/record-suite/rec-child/session.v3.jsonl
new file mode 100644
index 0000000000..30c34d6f29
--- /dev/null
+++ b/packages/test-support/session-snapshot/tests/fixtures/record-suite/rec-child/session.v3.jsonl
@@ -0,0 +1,6 @@
+{"type":"session","version":3,"id":"{{session:1}}","createdAt":700,"cwd":"{{cwd}}","isSeeded":false,"delegationDepth":0}
+{"type":"turn/start","data":{"turn":1}}
+{"type":"step/start","data":{"turn":1,"step":1}}
+{"type":"system/message","data":{"turn":1,"step":1,"message":{"id":"{{message:1}}","role":"system","content":[{"type":"text","text":"{{system}}"}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt"}}},"surfaceOp":"append"}
+{"type":"request/header","data":{"header":{"config":{"provider":"fake","model":"fake"},"tools":"{{tools}}"},"reason":"initial"}}
+{"type":"user/message","data":{"role":"user","content":[{"type":"text","text":"same inherited message"}],"source":{"kind":"user"},"id":"{{message:2}}"},"surfaceOp":"append"}
diff --git a/packages/test-support/session-snapshot/tests/storage-policy.spec.ts b/packages/test-support/session-snapshot/tests/storage-policy.spec.ts
index 326f5bc1e1..f579607e3c 100644
--- a/packages/test-support/session-snapshot/tests/storage-policy.spec.ts
+++ b/packages/test-support/session-snapshot/tests/storage-policy.spec.ts
@@ -1,7 +1,9 @@
-import { mkdtempSync, mkdirSync, rmSync, writeFileSync } from 'node:fs'
+import { mkdtempSync, mkdirSync, readFileSync, readdirSync, rmSync, writeFileSync } from 'node:fs'
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
 import { afterEach, expect, test } from 'vitest'
+import { SESSION_FORMAT_VERSION } from '@deepseek-ai/dsh-session'
+import { sessionFixtureName } from '../src/session-files.ts'
 import { assertSessionFixtureStorage } from '../src/suite.ts'
 
 const roots: string[] = []
@@ -13,28 +15,57 @@ const system = { type: 'system/message', data: { message: {
   role: 'system', content: [{ type: 'text', text: '{{system}}' }],
 } } }
 const request = { type: 'request/header', data: { header: { tools: '{{tools}}' } } }
+const historicalRequest = { type: 'request/header', data: { header: { system: '{{system}}', tools: '{{tools}}' } } }
 
 function fixture(id: number, version: number, events: unknown[]): string {
   return [{ type: 'session', version, id: `{{session:${id}}}`, createdAt: 0, delegationDepth: id - 1 }, ...events]
     .map(record => JSON.stringify(record)).join('\n') + '\n'
 }
 
-function registerGuard(childEvents: unknown[]): () => Promise<void> {
+function registerGuard(childEvents: unknown[], historicalEvents?: unknown[]): () => Promise<void> {
   const root = mkdtempSync(join(tmpdir(), 'snapshot-storage-policy-'))
   roots.push(root)
   const dir = join(root, 'pin')
   mkdirSync(dir)
-  writeFileSync(join(dir, 'session.v2.jsonl'), fixture(1, 2, [system, request]))
-  // Each role selects its highest generation; the older child deliberately violates the policy.
+  writeFileSync(join(dir, sessionFixtureName(0, SESSION_FORMAT_VERSION)), fixture(1, SESSION_FORMAT_VERSION, [system, request]))
+  // Each role selects its highest generation; the older child predates system/message.
   writeFileSync(join(dir, 'session.1.v1.jsonl'), fixture(2, 1, [request]))
-  writeFileSync(join(dir, 'session.1.v2.jsonl'), fixture(2, 2, childEvents))
-  return () => assertSessionFixtureStorage(dir, 'pin')
+  writeFileSync(join(dir, sessionFixtureName(1, SESSION_FORMAT_VERSION)), fixture(2, SESSION_FORMAT_VERSION, childEvents))
+  if (historicalEvents !== undefined) {
+    writeFileSync(join(dir, 'session.2.jsonl'), [
+      JSON.stringify({ type: 'session', id: 'aaaaaaaa-aaaa-4aaa-8aaa-aaaaaaaaaaaa', createdAt: 0 }),
+      ...historicalEvents.map(event => JSON.stringify(event)),
+      '',
+    ].join('\n'))
+  }
+  const contents = (): string[] => readdirSync(dir).sort().map(file => readFileSync(join(dir, file), 'utf8'))
+  const before = contents()
+  return async () => {
+    await assertSessionFixtureStorage(dir, 'pin')
+    expect(contents()).toEqual(before)
+  }
 }
 
 test('checks only the highest generation of every parent and child role', async () => {
   await expect(registerGuard([system, request])()).resolves.toBeUndefined()
 })
 
+test('preserves a selected historical child without imposing current prompt or identity storage', async () => {
+  await expect(registerGuard([system, request], [historicalRequest])()).resolves.toBeUndefined()
+})
+
+test.each([
+  ['unknown tool', { type: 'tool/result', data: { error: { code: 'UNKNOWN_TOOL' } } }, 'contains UNKNOWN_TOOL'],
+  ['noncanonical cwd', { type: 'user/message', data: { text: '/private{{cwd}}/file' } }, 'carries a non-canonical macOS cwd token'],
+] as const)('rejects a selected historical child with %s', async (_name, event, message) => {
+  await expect(registerGuard([system, request], [historicalRequest, event])()).rejects.toThrow(`pin/session.2.jsonl ${message}`)
+})
+
+test('rejects an unredacted identity in a selected current child beside historical residue', async () => {
+  const unredacted = { ...system, data: { message: { ...system.data.message, id: 'bbbbbbbb-bbbb-4bbb-8bbb-bbbbbbbbbbbb' } } }
+  await expect(registerGuard([unredacted, request], [historicalRequest])()).rejects.toThrow('identity redaction fixed point')
+})
+
 test.each([
   ['missing prompt', [request], 'has a request/header with no preceding system/message'],
   ['unscrubbed prompt', [{ ...system, data: { message: {
@@ -42,5 +73,5 @@ test.each([
   } } }, request], 'carries an unscrubbed system prompt'],
   ['unscrubbed tools', [system, { type: 'request/header', data: { header: { tools: [] } } }], 'carries unscrubbed tool schemas'],
 ] as const)('rejects a selected child with %s', async (_name, events, message) => {
-  await expect(registerGuard([...events])()).rejects.toThrow(`pin/session.1.v2.jsonl ${message}`)
+  await expect(registerGuard([...events])()).rejects.toThrow(`pin/${sessionFixtureName(1, SESSION_FORMAT_VERSION)} ${message}`)
 })
diff --git a/packages/test-support/session-snapshot/tests/suite.spec.ts b/packages/test-support/session-snapshot/tests/suite.spec.ts
index ebeb91e17f..f27c70e52b 100644
--- a/packages/test-support/session-snapshot/tests/suite.spec.ts
+++ b/packages/test-support/session-snapshot/tests/suite.spec.ts
@@ -128,13 +128,14 @@ const RECORD_SCENARIOS: Scenario[] = [
 // committed record fixtures and expected outputs in place.
 const BOOTSTRAP = process.env.ACP_SNAPSHOT_SPEC_BOOTSTRAP === '1'
 const recordDir = BOOTSTRAP ? RECORD_SRC : mkdtempSync(join(tmpdir(), 'acp-snap-record-suite-'))
-const retiredChildFixture = readFileSync(join(RECORD_SRC, 'rec-child', 'session.1.jsonl'), 'utf8')
+const retiredChildFixture = readFileSync(join(RECORD_SRC, 'rec-child', 'session.1.v3.jsonl'), 'utf8')
 if (!BOOTSTRAP) {
   cpSync(RECORD_SRC, recordDir, { recursive: true })
   // Record mode owns its output inventory: a new scenario has no primary yet,
   // while a changed child count can leave old numbered fixtures behind.
   rmSync(join(recordDir, 'rec-pin', 'session.jsonl'))
-  writeFileSync(join(recordDir, 'rec-child', 'session.2.jsonl'), retiredChildFixture)
+  rmSync(join(recordDir, 'rec-pin', 'session.v3.jsonl'))
+  writeFileSync(join(recordDir, 'rec-child', 'session.2.v3.jsonl'), retiredChildFixture)
 }
 const refreshDir = mkdtempSync(join(tmpdir(), 'acp-snap-refresh-suite-'))
 cpSync(REPLAY_DIR, refreshDir, { recursive: true })
@@ -244,7 +245,7 @@ describe('defineAcpSnapshotSuite: record inventory write-back', () => {
     expect(fixture).toContain('"type":"session"')
     expect(fixture).toContain('"cwd":"{{cwd}}"')
     if (!BOOTSTRAP) {
-      expect(readFileSync(join(recordDir, 'rec-child', 'session.2.jsonl'), 'utf8')).toBe(retiredChildFixture)
+      expect(readFileSync(join(recordDir, 'rec-child', 'session.2.v3.jsonl'), 'utf8')).toBe(retiredChildFixture)
     }
     expect(readFileSync(join(recordDir, 'rec-child', 'tool-schemas.1.expected.json'), 'utf8'))
       .toContain('"name": "t1"')