feat(cps): scan @imported files for volatile cached-prefix content (v5.10 B6) [skip-docs]

CPS originally inspected only files discovery classifies as claude-md, but a
CLAUDE.md can pull arbitrary files into the cached prefix via @import — and
those targets (e.g. @shared/conventions.md) are usually not claude-md in
discovery, so their inlined content was never scanned. Neither TOK Pattern A
(top-30 of cascade files) nor the in-file CPS scan reaches past the importing
file, so volatility inside an imported file was invisible.

B6 closes the gap: for each @import whose import site sits within the
cached-prefix window (imp.line <= CACHED_PREFIX_LINES), CPS resolves the path
(resolveImportPath, mirroring import-resolver/token-hotspots semantics), reads
the target, and runs findVolatileLines over its first 150 lines. A hit emits a
distinct medium finding — "Volatile content in @imported file breaks cached
prefix" — keyed on the resolved file, evidence naming the importer.

Scope boundaries (deliberate):
- One hop only; imports-of-imports stay with IMP (deep-chain owner).
- No lines-1-30 skip for imported content — that exclusion is root-file-specific
  to avoid Pattern A overlap, which never reaches imported files.
- No double-reporting: an import resolving to a discovered claude-md is skipped
  (own iteration); a reportedImports set dedupes a target imported by several
  CLAUDE.md files.

Dropped from B6 (per plan verdict): confident behavioral cache-buster detection
(opusplan/model-switch is runtime, not static config) and jq-transcript
automation. "No overstated behavioral finding ships" — even the permitted
opusplan info-advisory was left out; the @import extension is the whole of B6.

Byte-stability: the in-file finding keeps the same condition + byte-identical
evidence/description (continue-skip refactored to if-emit, behaviour-preserving);
new findings fire only on a volatile import, which no frozen v5.0.0 fixture has.
docs: README + scanner-internals CPS rows + full B6 note; CLAUDE.md kept lean
([skip-docs]). Suite 1254 -> 1257 green; snapshots + SC-5 untouched.
Version/badges/CHANGELOG wait for the v5.10 release cut.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Kjell Tore Guttormsen 2026-06-23 20:45:12 +02:00
commit fa1ddd963a
8 changed files with 183 additions and 26 deletions

View file

@ -15,9 +15,12 @@
* Zero external dependencies.
*/
import { resolve, dirname } from 'node:path';
import { tmpdir } from 'node:os';
import { readTextFile } from './lib/file-discovery.mjs';
import { finding, scannerResult } from './lib/output.mjs';
import { SEVERITY } from './lib/severity.mjs';
import { findImports } from './lib/yaml-parser.mjs';
const SCANNER = 'CPS';
@ -41,6 +44,22 @@ const VOLATILE_PATTERNS = [
{ rx: /\$\{[A-Z_][A-Z0-9_]*\}/, label: '${VAR} substitution' },
];
/**
* Resolve an @import path relative to the file that declares it.
* Mirrors import-resolver.mjs / token-hotspots.mjs path semantics.
* @param {string} importPath
* @param {string} containingFile
* @returns {string} absolute resolved path
*/
function resolveImportPath(importPath, containingFile) {
if (importPath.startsWith('~')) {
const home = process.env.HOME || process.env.USERPROFILE || tmpdir();
return resolve(importPath.replace(/^~/, home));
}
if (importPath.startsWith('/')) return importPath;
return resolve(dirname(containingFile), importPath);
}
/**
* Scan content for volatile lines within the cached prefix window.
* Returns array of {line, label, snippet}.
@ -75,40 +94,90 @@ export async function scan(targetPath, discovery) {
const findings = [];
let filesScanned = 0;
// Files already scanned in-file below — an @import resolving to one of these
// is reported by its own iteration, not duplicated as an import finding.
const discoveredClaudeMd = new Set(
discovery.files.filter(f => f.type === 'claude-md').map(f => f.absPath));
// @imported files reported once, even when several CLAUDE.md files import them.
const reportedImports = new Set();
for (const f of discovery.files) {
if (f.type !== 'claude-md') continue;
filesScanned++;
const content = await readTextFile(f.absPath);
if (!content) continue;
const volatile = findVolatileLines(content);
if (volatile.length === 0) continue;
// --- In-file volatility (unchanged behavior) ---
const volatile = findVolatileLines(content);
// Skip volatility that's already covered by TOK Pattern A (lines 130) —
// CPS' value is in the 31150 range. Pattern A handles 130.
const beyondTopThirty = volatile.filter(v => v.line > 30);
if (beyondTopThirty.length === 0) continue;
if (beyondTopThirty.length > 0) {
const evidence =
beyondTopThirty.slice(0, 5)
.map(v => `line ${v.line} (${v.label}): ${v.snippet}`)
.join('; ');
findings.push(finding({
scanner: SCANNER,
severity: SEVERITY.medium,
title: 'Volatile content inside cached prefix breaks reuse',
description:
`${f.relPath || f.absPath} contains ${beyondTopThirty.length} volatile ` +
`entr${beyondTopThirty.length === 1 ? 'y' : 'ies'} between lines 31 and ` +
`${CACHED_PREFIX_LINES}. The prompt cache covers the file's prefix; ` +
'any volatility forces a fresh cache write from that line down on every turn.',
file: f.absPath,
evidence,
recommendation:
'Move volatile sections (timestamps, !shell-exec, ${VAR} substitutions, dated logs) ' +
`below line ${CACHED_PREFIX_LINES} or extract them to an @import-ed file outside the ` +
'cached prefix. Stable content above, volatile content below.',
category: 'token-efficiency',
}));
}
const evidence =
beyondTopThirty.slice(0, 5)
.map(v => `line ${v.line} (${v.label}): ${v.snippet}`)
.join('; ');
findings.push(finding({
scanner: SCANNER,
severity: SEVERITY.medium,
title: 'Volatile content inside cached prefix breaks reuse',
description:
`${f.relPath || f.absPath} contains ${beyondTopThirty.length} volatile ` +
`entr${beyondTopThirty.length === 1 ? 'y' : 'ies'} between lines 31 and ` +
`${CACHED_PREFIX_LINES}. The prompt cache covers the file's prefix; ` +
'any volatility forces a fresh cache write from that line down on every turn.',
file: f.absPath,
evidence,
recommendation:
'Move volatile sections (timestamps, !shell-exec, ${VAR} substitutions, dated logs) ' +
`below line ${CACHED_PREFIX_LINES} or extract them to an @import-ed file outside the ` +
'cached prefix. Stable content above, volatile content below.',
category: 'token-efficiency',
}));
// --- v5.10 B6: volatility inside @imported files ---
// @import-ed content is inlined into the cached prefix at the import site.
// TOK Pattern A and the in-file scan above never look past the importing
// file, so volatility in an imported file is otherwise invisible. We scan
// direct imports only (one hop); IMP owns deep-chain analysis. The whole
// imported-file prefix counts (no lines-130 skip — that exclusion is
// root-file-specific to avoid Pattern A overlap, which does not reach here).
for (const imp of findImports(content)) {
if (imp.line > CACHED_PREFIX_LINES) continue; // import site outside prefix
const resolved = resolveImportPath(imp.path, f.absPath);
if (discoveredClaudeMd.has(resolved)) continue; // scanned in its own iteration
if (reportedImports.has(resolved)) continue;
reportedImports.add(resolved);
const importedContent = await readTextFile(resolved);
if (!importedContent) continue;
const importedVolatile = findVolatileLines(importedContent);
if (importedVolatile.length === 0) continue;
const importEvidence =
`imported by ${f.relPath || f.absPath} (@${imp.path} at line ${imp.line}); ` +
importedVolatile.slice(0, 5)
.map(v => `line ${v.line} (${v.label}): ${v.snippet}`)
.join('; ');
findings.push(finding({
scanner: SCANNER,
severity: SEVERITY.medium,
title: 'Volatile content in @imported file breaks cached prefix',
description:
`@${imp.path} (imported by ${f.relPath || f.absPath} at line ${imp.line}) contains ` +
`${importedVolatile.length} volatile entr${importedVolatile.length === 1 ? 'y' : 'ies'} ` +
`within its first ${CACHED_PREFIX_LINES} lines. @import-ed content is inlined into the ` +
'prompt-cache prefix, so volatility there forces a fresh cache write every turn — even ' +
'when the importing CLAUDE.md is itself byte-stable.',
file: resolved,
evidence: importEvidence,
recommendation:
'Move volatile content (timestamps, !shell-exec, ${VAR} substitutions, dated logs) out ' +
'of the @imported file, or import it below the cached-prefix window. Keep imported config ' +
'byte-stable so the importing file\'s cache survives.',
category: 'token-efficiency',
}));
}
}
return scannerResult(SCANNER, 'ok', findings, filesScanned, Date.now() - start);