fix: stabilize spill snapshot path budget

packages/support/acp-snapshot/src/harness.ts

@@ -180,6 +180,9 @@ export interface RunOptions {
 export async function runScenario(input: InputScript, opts: RunOptions): Promise<RunResult> {
   const cwd = await mkdtemp(join(tmpdir(), 'acp-snap-cwd-'))
   const sessionsRoot = await mkdtemp(join(tmpdir(), 'acp-snap-sessions-'))
+  // Fixed path length: spill-policy budgets the preview against the REAL path
+  // before stdout normalization, so tmpdir() length differences churn goldens.
+  const spillRoot = '/tmp/dsh-acp-snapshot-spill'
   // Everything past the temp-dir creation runs under a try/finally that always
   // removes both dirs — so a failure in workspace seeding, spawn, or any step
   // never leaks them (the "e2e tests own their resources" rule).
@@ -201,6 +204,7 @@ export async function runScenario(input: InputScript, opts: RunOptions): Promise
       DSH_SNAPSHOT: opts.mode,
       DSH_SNAPSHOT_FILE: opts.fixtureFile,
       DSH_SNAPSHOT_SESSIONS_ROOT: sessionsRoot,
+      DSH_SNAPSHOT_SPILL_ROOT: spillRoot,
       ...opts.overrideFile !== undefined ? { DSH_SNAPSHOT_OVERRIDE: opts.overrideFile } : {},
       ...opts.childFiles !== undefined && opts.childFiles.length > 0
         ? { DSH_SNAPSHOT_CHILD_FILES: opts.childFiles.join(delimiter) }
@@ -310,6 +314,7 @@ export async function runScenario(input: InputScript, opts: RunOptions): Promise
     }
     await rm(cwd, { recursive: true, force: true })
     await rm(sessionsRoot, { recursive: true, force: true })
+    await rm(spillRoot, { recursive: true, force: true })
   }
 
   return {

packages/support/acp-snapshot/src/normalize.ts

@@ -38,6 +38,11 @@ const LOCAL_SPILL_PATH_RE = new RegExp(
   + String.raw`(?=\. Use read with offset/limit|[\s)]|$)`,
   'g',
 )
+const SNAPSHOT_SPILL_PATH_RE = new RegExp(
+  String.raw`/tmp/dsh-acp-snapshot-spill/session-[0-9a-f]{12}/[0-9a-f]{12}-([A-Za-z0-9._~-]+?)`
+  + String.raw`(?=\. Use read with offset/limit|[\s)]|$)`,
+  'g',
+)
 
 /** Inputs the normalizers need to recognize a run's volatile values. */
 export interface NormalizeContext {
@@ -55,6 +60,7 @@ function scrubString(value: string, ctx: NormalizeContext): string {
   out = out.split(ctx.cwd).join(CWD)
   out = out.split(`/private${CWD}`).join(CWD)
   out = out.replace(LOCAL_SPILL_PATH_RE, (_match, name: string) => `{{spillPath:${name}}}`)
+  out = out.replace(SNAPSHOT_SPILL_PATH_RE, (_match, name: string) => `{{spillPath:${name}}}`)
   for (const id of ctx.sessionIds) out = out.split(id).join(SESSION_ID)
   out = out.replace(UUID_RE, SESSION_ID)
   return out

packages/support/acp-snapshot/tests/normalize.spec.ts

@@ -117,6 +117,21 @@ describe('normalizeSessionLog', () => {
     expect(out).not.toContain('/private{{spillPath')
   })
 
+  it('scrubs fixed snapshot spill paths', () => {
+    const ev = JSON.stringify({
+      type: 'tool/result', seq: 2, time: 5,
+      data: {
+        content: [{
+          type: 'text',
+          text: 'Full formatted result saved to: /tmp/dsh-acp-snapshot-spill/session-c22bc3f1d2af/8a7b6c5d4e3f-bash.txt. Use read with offset/limit to inspect it.',
+        }],
+      },
+    })
+    const out = normalizeSessionLog(`${header({ cwd: ctx.cwd })}\n${ev}\n`, ctx)
+    expect(out).toContain('{{spillPath:bash.txt}}')
+    expect(out).not.toContain('/tmp/dsh-acp-snapshot-spill')
+  })
+
   it('scrubs the session id in the header', () => {
     const out = normalizeSessionLog(`${header({ id: ctx.sessionIds[0] })}\n`, ctx)
     expect(out).toContain('{{sessionId}}')