diff --git a/.changeset/noble-geese-climb.md b/.changeset/noble-geese-climb.md
new file mode 100644
index 000000000..fab016957
--- /dev/null
+++ b/.changeset/noble-geese-climb.md
@@ -0,0 +1,5 @@
+---
+type: Fixed
+pr: 4364
+---
+**`/gsd-update --reapply` no longer reports no_baseline when a hash-matching gsd-pristine/ snapshot is stored without the gsd-core/ prefix** — the verifier and the installer now resolve the baseline by the recorded SHA-256 and relocate the orphaned snapshot to its canonical path on the next update, so the correct baseline is finally consumed instead of sitting unusable forever. (#4145)
diff --git a/.gitignore b/.gitignore
index ea044ca1c..62eb22987 100644
--- a/.gitignore
+++ b/.gitignore
@@ -138,6 +138,8 @@ build/
 /gsd-core/bin/lib/ui-consideration-probe.cjs
 /gsd-core/bin/lib/config-types.cjs
 /gsd-core/bin/lib/cli-exit.cjs
+# #4145: emitted artifact of src/pristine-baseline.cts — never edited.
+/gsd-core/bin/lib/pristine-baseline.cjs
 /gsd-core/bin/lib/code-review-flags.cjs
 /gsd-core/bin/lib/code-review-depth.cjs
 /gsd-core/bin/lib/context-utilization.cjs
diff --git a/bin/install.js b/bin/install.js
index 7d8233317..4951e8221 100755
--- a/bin/install.js
+++ b/bin/install.js
@@ -544,6 +544,13 @@ const {
   RUNTIME_PROFILE_MAP: GSD_RUNTIME_PROFILE_MAP,
   isAnthropicFlavoredModel: gsdIsAnthropicFlavoredModel,
 } = require(path.join(_gsdLibDir, 'model-catalog.cjs'));
+// #4145: shared hash-first recovery for gsd-pristine/ baselines stored at an
+// unexpected path (e.g. without the gsd-core/ prefix an earlier release's
+// writer dropped). Same module the reapply verifier uses, so the two readers
+// cannot drift apart again.
+const {
+  findPristineByHash: gsdFindPristineByHash,
+} = require(path.join(_gsdLibDir, 'pristine-baseline.cjs'));
 // #2875 Part 2: MODEL_PROFILES + resolveTierEntry are now consumed only by
 // install-model-override-resolver.cjs's readGsdRuntimeProfileResolver
 // (required below) — this installer no longer needs its own bindings.
@@ -10153,6 +10160,63 @@ function populatePristineDir({ packageSrc, pristineDir, modified, runtime, pathP
   return written;
 }
 
+/**
+ * #4145: recover a pristine baseline from a hash-matching orphan stored at an
+ * unexpected path under gsd-pristine/ (e.g. without the gsd-core/ prefix an
+ * earlier release's writer dropped).
+ *
+ * The preserve-check's strict join (pristineDir + manifest-keyed relPath)
+ * misses such snapshots, so they were pushed into regeneration from the
+ * incoming release — and when the file changed upstream, the candidate's hash
+ * could never satisfy the recorded outgoing hash, leaving the correct
+ * baseline permanently unconsumed and unpruned (the self-perpetuating state
+ * #4145 reports). Hash equality with pristine_hashes is the same authority
+ * the #3657 drift guard trusts, so an exact match cannot be the wrong
+ * baseline no matter where under gsd-pristine/ it lives.
+ *
+ * Recovery = relocation: copy the orphan to the canonical manifest-keyed path
+ * (hash-verified after the copy) and remove the orphan only once the
+ * canonical copy is verified in place. Returns true when the canonical path
+ * ended up holding recorded-hash bytes. Never deletes anything it cannot
+ * vouch for by hash, and never consumes a path that is the canonical path of
+ * ANY manifest file (see canonicalSkip below) — only genuine orphans, which
+ * no strict-join reader ever consults, are eligible for removal.
+ */
+function recoverOrphanedPristine(pristineDir, relPath, recordedHash, canonicalSkip) {
+  if (!recordedHash) return false;
+  let orphanRel;
+  try {
+    // canonicalSkip = the normalized manifest keys: a file already sitting at
+    // any canonical path can never be (re-)adopted through the scan. Without
+    // this, two modified files sharing byte-identical outgoing content would
+    // repeatedly "rescue" each other's canonical away (relocate + delete at
+    // its home path) in alternating updates — bytes identical, state unstable.
+    // It also keeps drift (#3657) / stale (#3407) territory with the caller.
+    orphanRel = gsdFindPristineByHash(pristineDir, recordedHash, canonicalSkip);
+  } catch {
+    return false;
+  }
+  if (!orphanRel) return false;
+  const outRef = resolveInstallRelativePath(pristineDir, relPath);
+  if (!outRef) return false;
+  try {
+    fs.mkdirSync(path.dirname(outRef.fullPath), { recursive: true });
+    fs.copyFileSync(path.join(pristineDir, orphanRel), outRef.fullPath);
+    // Verify the relocated copy before removing the orphan — only a
+    // hash-matching canonical counts as recovered.
+    if (fileHash(outRef.fullPath) !== recordedHash) {
+      try { fs.rmSync(outRef.fullPath, { force: true }); } catch { /* best-effort */ }
+      return false;
+    }
+    // Orphan removal is best-effort: the canonical copy is already verified,
+    // so a failed unlink leaves a harmless duplicate, never data loss.
+    try { fs.rmSync(path.join(pristineDir, orphanRel), { force: true }); } catch { /* best-effort */ }
+    return true;
+  } catch {
+    return false;
+  }
+}
+
 /**
  * Detect user-modified GSD files by comparing against install manifest.
  * Backs up modified files to gsd-local-patches/ for reapply after update.
@@ -10299,6 +10363,15 @@ function saveLocalPatches(configDir, pristineCtx) {
       const stalePaths = new Set();
       // Track which relPaths were successfully regenerated (from either missing or stale).
       const regeneratedPaths = new Set();
+      // #4145: track which relPaths were recovered by relocating a hash-matching
+      // orphan (stored at an unexpected path, e.g. without the gsd-core/ prefix).
+      const rescuedPaths = new Set();
+      // #4145: the set of paths that are SOME file's canonical pristine path
+      // (every normalized manifest key). The orphan scan must never consume
+      // these — see recoverOrphanedPristine.
+      const canonicalSkip = new Set(
+        Object.keys(manifest.files || {}).map((k) => normalizeInstallRelativePath(k)).filter(Boolean),
+      );
       const missingPaths = [];
       for (const relPath of modified) {
         const outRef = resolveInstallRelativePath(pristineDir, relPath);
@@ -10320,6 +10393,17 @@ function saveLocalPatches(configDir, pristineCtx) {
             stalePaths.add(relPath);
           }
         }
+        // #4145: canonical absent (or just removed as stale) — before falling
+        // into regeneration, try to recover the baseline from a hash-matching
+        // orphan elsewhere under gsd-pristine/ and relocate it to the canonical
+        // path. This is the self-heal for snapshots an earlier release stored
+        // without the gsd-core/ prefix: without it the state repeats forever
+        // (regeneration candidates from the incoming release can never satisfy
+        // the recorded outgoing hash when upstream changed the file).
+        if (recoverOrphanedPristine(pristineDir, relPath, pristineHashes[relPath], canonicalSkip)) {
+          rescuedPaths.add(relPath);
+          continue;
+        }
         // File absent from gsd-pristine/ (or just removed above as stale):
         // attempt hash-validated regeneration from new-release source.
         missingPaths.push(relPath);
@@ -10362,13 +10446,21 @@ function saveLocalPatches(configDir, pristineCtx) {
       }
       // `regenerated` = total files successfully regenerated (from missing OR stale).
       const regenerated = regeneratedPaths.size;
+      // `rescued` = files recovered by relocating a hash-matching orphan to its
+      // canonical path (#4145) — distinct from preservation (canonical already
+      // correct) and regeneration (bytes re-derived from new-release source).
+      const rescued = rescuedPaths.size;
       // `removed` = stale entries that were deleted and NOT subsequently regenerated.
       // Entries that were stale-deleted but then successfully regenerated are counted
-      // only in `regenerated` — the counts are non-overlapping.
-      const removed = [...stalePaths].filter(p => !regeneratedPaths.has(p)).length;
+      // only in `regenerated`; stale-deleted-then-orphan-rescued entries are counted
+      // only in `rescued` — the counts are non-overlapping.
+      const removed = [...stalePaths].filter(p => !regeneratedPaths.has(p) && !rescuedPaths.has(p)).length;
       if (preserved > 0) {
         console.log('  ' + green + '✓' + reset + '  Preserved ' + cyan + 'gsd-pristine/' + reset + ' (' + preserved + ' file(s)) for three-way merge');
       }
+      if (rescued > 0) {
+        console.log('  ' + green + '✓' + reset + '  Recovered ' + cyan + 'gsd-pristine/' + reset + ' (' + rescued + ' file(s)) by recorded hash from a legacy-path snapshot and relocated them (#4145)');
+      }
       if (regenerated > 0) {
         console.log('  ' + green + '✓' + reset + '  Regenerated ' + cyan + 'gsd-pristine/' + reset + ' (' + regenerated + ' file(s)) via hash-validated new-release source');
       }
diff --git a/docs/INVENTORY-MANIFEST.json b/docs/INVENTORY-MANIFEST.json
index 755c28de7..8d46675fd 100644
--- a/docs/INVENTORY-MANIFEST.json
+++ b/docs/INVENTORY-MANIFEST.json
@@ -475,6 +475,7 @@
       "planning-scope.cjs",
       "planning-snapshot.cjs",
       "planning-workspace.cjs",
+      "pristine-baseline.cjs",
       "probe-core.cjs",
       "profile-output.cjs",
       "profile-pipeline-command-router.cjs",
diff --git a/docs/INVENTORY.md b/docs/INVENTORY.md
index 09baf64ef..f1e418d65 100644
--- a/docs/INVENTORY.md
+++ b/docs/INVENTORY.md
@@ -603,6 +603,7 @@ Full listing: `gsd-core/bin/lib/*.cjs`.
 | `planning-scope.cjs` | Frozen `SCOPE` discriminator (`COMPLETE`/`TRUNCATED`/`UNSCOPED`/`UNREADABLE`) distinguishing a genuinely-empty derivation from one computed over a truncated or unscoped input, so callers can branch on the difference instead of reading a plausible zero (ADR-3180) |
 | `planning-snapshot.cjs` | Parsed projection of `.planning/` composed exclusively from the ADR-3180 §7 owners (milestone identity, phase enumeration, phase completion, plan/summary counting, STATE.md current-phase) — exposes only scope-carrying parsed values, never raw document text, so a diagnostic rule cannot re-derive a field's location (ADR-3180 §8.1) |
 | `planning-workspace.cjs` | Planning path/workstream seam (`planningDir`, `planningPaths`, active-workstream routing, `.planning/.lock` orchestration) |
+| `pristine-baseline.cjs` | Hash-first recovery for `gsd-pristine/` baselines stored at an unexpected path (compiled from `src/pristine-baseline.cts`, gitignored; #4145) — `findPristineByHash(pristineDir, recordedHash, skip?)` walks `gsd-pristine/` in deterministic sorted order, skips symlinks, and returns the first file whose SHA-256 equals the recorded `backup-meta.json.pristine_hashes` entry (the same authority the #3657 drift guard trusts); the `skip` set excludes canonical manifest-keyed paths so a relocation never consumes another file's canonical baseline. Shared by `verify-reapply-patches.cjs`'s `verifyFile` (read-only adoption when the strict join misses) and `install.js`'s `saveLocalPatches` (orphan relocation self-heal) so the two readers cannot drift apart again |
 | `project-root.cjs` | Resolves a project root from a starting directory using four heuristics (own `.planning/` guard, `sub_repos` config, `multiRepo` flag, `.git` heuristic) |
 | `profile-output.cjs` | Profile rendering, USER-PROFILE.md and dev-preferences.md generation |
 | `profile-pipeline-command-router.cjs` | ADR-959 capability command router for the profile-pipeline command family — dispatches scan-sessions, extract-messages, profile-sample (pipeline phase) and write-profile, profile-questionnaire, generate-dev-preferences, generate-claude-profile, generate-claude-md (output phase); phase 6 cutover |
diff --git a/eslint.config.mjs b/eslint.config.mjs
index 0b6bb13f1..a017ad849 100644
--- a/eslint.config.mjs
+++ b/eslint.config.mjs
@@ -126,6 +126,8 @@ export default tseslint.config(
       'gsd-core/bin/lib/prohibition-enforcement.cjs',
       // #3770: tsc-generated runtime artifact — lint the src/tdd-red-evidence.cts source.
       'gsd-core/bin/lib/tdd-red-evidence.cjs',
+      // #4145: tsc-generated runtime artifact — lint the src/pristine-baseline.cts source.
+      'gsd-core/bin/lib/pristine-baseline.cjs',
       'gsd-core/bin/lib/ui-consideration-probe.cjs',
       'gsd-core/bin/lib/code-review-flags.cjs',
       'gsd-core/bin/lib/code-review-depth.cjs',
diff --git a/gsd-core/bin/verify-reapply-patches.cjs b/gsd-core/bin/verify-reapply-patches.cjs
index 08170a0c1..c052fc3ec 100755
--- a/gsd-core/bin/verify-reapply-patches.cjs
+++ b/gsd-core/bin/verify-reapply-patches.cjs
@@ -33,6 +33,11 @@ const fs = require('node:fs');
 const path = require('node:path');
 const crypto = require('node:crypto');
 const { ExitError, runMain } = require('./lib/cli-exit.cjs');
+// #4145: shared hash-first recovery for baselines stored at an unexpected
+// path under gsd-pristine/ (e.g. without the gsd-core/ prefix an earlier
+// release's writer dropped). Same module the installer's preserve-check uses,
+// so the two readers cannot drift apart again.
+const { findPristineByHash } = require('./lib/pristine-baseline.cjs');
 
 const SIGNIFICANT_MIN_CHARS = 12;
 const GSD_HOOK_VERSION_LINE_RE = /^(?:\/\/|#)\s*gsd-hook-version:\s*\S+\s*$/i;
@@ -344,8 +349,29 @@ function verifyFile({ relPath, patchesDir, configDir, pristineDir, pristineHashe
       // pristinePathExists stays false.
     }
 
-    // Bug #934: recordedHash is present (modern installer) but the pristine
-    // path does not exist on disk at all (stat threw above).  This means
+    // Bug #4145: the canonical join missed, but the recorded hash is the
+    // baseline authority the #3657 drift guard already trusts. Before
+    // reporting OK_NO_BASELINE, scan gsd-pristine/ for byte-identical content
+    // (an earlier release may have stored the snapshot without the gsd-core/
+    // prefix). An exact sha-256 match cannot be the wrong baseline, and
+    // gsd-pristine/ holds only backed-up files, so the scan is small. The
+    // canonical path itself is excluded — a mismatching file at the joined
+    // path is drift (#3657), never re-adopted through the scan.
+    if (!pristinePathExists && recordedHash) {
+      try {
+        const recoveredRel = findPristineByHash(pristineDir, recordedHash, hashKey);
+        if (recoveredRel) {
+          pristineContent = fs.readFileSync(path.join(pristineDir, recoveredRel), 'utf8');
+          pristinePathExists = true;
+        }
+      } catch {
+        // scan or read failure — fall through to the OK_NO_BASELINE posture
+      }
+    }
+
+    // Bug #934: recordedHash is present (modern installer) but no hash-matching
+    // pristine exists anywhere under gsd-pristine/ (stat threw above AND the
+    // #4145 scan found nothing).  This means
     // saveLocalPatches recorded a hash but could not write the corresponding
     // gsd-pristine/ file (the only candidate was discarded because it was from
     // a newer release).  Falling to over-broad mode here would treat every
@@ -353,8 +379,9 @@ function verifyFile({ relPath, patchesDir, configDir, pristineDir, pristineHashe
     // false FAIL_USER_LINES_MISSING for each upstream removal.  Since we
     // cannot reason correctly without a baseline, the safe answer is advisory/
     // non-blocking: return OK_NO_BASELINE and let the caller decide.
-    // NOTE: this guard fires ONLY when stat threw (path absent), not when the
-    // path is present but non-file — in that case over-broad mode is safer.
+    // NOTE: this guard fires ONLY when the baseline path is absent (stat threw
+    // and nothing matched by hash), not when the path is present but non-file —
+    // in that case over-broad mode is safer.
     if (!pristinePathExists && recordedHash) {
       result.reason = REASON.OK_NO_BASELINE;
       return result;
diff --git a/gsd-core/workflows/reapply-patches.md b/gsd-core/workflows/reapply-patches.md
index b4e6a493a..0b95f333f 100644
--- a/gsd-core/workflows/reapply-patches.md
+++ b/gsd-core/workflows/reapply-patches.md
@@ -169,7 +169,7 @@ Check if a `gsd-pristine/` directory exists alongside `gsd-local-patches/`:
 ```bash
 PRISTINE_DIR="$CONFIG_DIR/gsd-pristine"
 ```
-If it exists, the installer saved pristine copies at install time. Use these as the baseline.
+If it exists, the installer saved pristine copies at install time. Use these as the baseline. Both the deterministic verifier and the installer's preserve-check resolve each file's snapshot at its canonical path first and, when that misses, by the SHA-256 recorded in `pristine_hashes` — so a snapshot stored at a legacy path (for example, without the `gsd-core/` prefix an earlier release dropped) is still found and, on the next update, relocated to its canonical path (#4145).
 
 ### Option C: No baseline available (two-way fallback)
 If neither git history nor pristine snapshots are available, fall back to two-way comparison — but with **strengthened heuristics** (see Step 3).
diff --git a/src/pristine-baseline.cts b/src/pristine-baseline.cts
new file mode 100644
index 000000000..1bc5c40e6
--- /dev/null
+++ b/src/pristine-baseline.cts
@@ -0,0 +1,94 @@
+/**
+ * #4145: hash-first recovery for gsd-pristine/ baselines stored at an
+ * unexpected path.
+ *
+ * Some installs hold a pristine snapshot whose SHA-256 equals the hash recorded
+ * in backup-meta.json.pristine_hashes for a manifest-keyed file, but at a path
+ * that is not `path.join(pristineDir, relPath)` — e.g. stored without the
+ * `gsd-core/` top-level segment by an earlier release's writer. Both readers
+ * (verify-reapply-patches.cjs verifyFile and install.js saveLocalPatches)
+ * resolved strictly by that join, missed the snapshot, and reported
+ * ok_no_baseline / fell into regeneration that can never satisfy the recorded
+ * outgoing hash — a self-perpetuating gap.
+ *
+ * Hash equality with the recorded pristine_hashes entry is the same authority
+ * the #3657 drift guard already trusts, so a match cannot be the wrong
+ * baseline regardless of which release wrote it or where under gsd-pristine/
+ * it lives. This module owns the shared scan so the two readers cannot drift
+ * apart again (two private strict joins drifting is exactly the bug class).
+ *
+ * ADR-457: runtime module in src/*.cts, compiled to
+ * gsd-core/bin/lib/pristine-baseline.cjs.
+ */
+
+import fs from 'node:fs';
+import path from 'node:path';
+import crypto from 'node:crypto';
+
+/**
+ * SHA-256 hex digest of a file's raw bytes. Byte-for-byte the same digest
+ * install.js fileHash() records into manifests and backup-meta.json.
+ */
+export function sha256File(absPath: string): string {
+  return crypto.createHash('sha256').update(fs.readFileSync(absPath)).digest('hex');
+}
+
+function walkSorted(dir: string, relPrefix: string, results: string[]): void {
+  let entries: fs.Dirent[];
+  try {
+    entries = fs.readdirSync(dir, { withFileTypes: true });
+  } catch {
+    return; // absent or unreadable — nothing to scan here
+  }
+  entries.sort((a, b) => (a.name < b.name ? -1 : a.name > b.name ? 1 : 0));
+  for (const entry of entries) {
+    // Never follow symlinks: gsd-pristine/ is installer-authored plain files;
+    // a link here is not a baseline and must not redirect the walk out of the
+    // tree (same posture as migration 004's walker).
+    if (entry.isSymbolicLink()) continue;
+    const rel = relPrefix ? `${relPrefix}/${entry.name}` : entry.name;
+    if (entry.isDirectory()) {
+      walkSorted(path.join(dir, entry.name), rel, results);
+    } else if (entry.isFile()) {
+      results.push(rel);
+    }
+  }
+}
+
+/**
+ * Find the first file under `pristineDir` (deterministic sorted walk) whose
+ * SHA-256 equals `recordedHash`, as a pristineDir-relative POSIX path.
+ *
+ * - `skip` is never returned — a single POSIX relPath string or a Set of them.
+ *   Callers pass the canonical path(s) they (or other files in the same run)
+ *   already own, so a file sitting at a canonical path is never adopted
+ *   through the scan. For the installer's relocation this is what prevents a
+ *   byte-identical canonical belonging to ANOTHER modified file from being
+ *   "rescued" away (relocated and deleted at its home path).
+ * - Multiple matches are byte-identical by sha-256 authority; sorted order
+ *   makes the choice deterministic.
+ * - Returns null when pristineDir is absent/unreadable or nothing matches.
+ */
+export function findPristineByHash(
+  pristineDir: string,
+  recordedHash: string,
+  skip?: string | ReadonlySet<string>,
+): string | null {
+  if (!pristineDir || typeof recordedHash !== 'string' || recordedHash.length === 0) {
+    return null;
+  }
+  const skipSet = skip instanceof Set ? skip : new Set(skip !== undefined ? [skip] : []);
+  const rels: string[] = [];
+  walkSorted(pristineDir, '', rels);
+  for (const rel of rels) {
+    if (skipSet.has(rel)) continue;
+    try {
+      if (sha256File(path.join(pristineDir, rel)) === recordedHash) {
+        return rel;
+      }
+    } catch {
+      // unreadable candidate — keep scanning
+    }
+  }
+  return null;
+}
diff --git a/tests/install-write-confinement.test.cjs b/tests/install-write-confinement.test.cjs
index 4d16689e6..b4ceaece6 100644
--- a/tests/install-write-confinement.test.cjs
+++ b/tests/install-write-confinement.test.cjs
@@ -4013,3 +4013,227 @@ describe('Bug #4086: saveLocalPatches resolves skills/ manifest keys at the runt
 });
   });
 }
+
+
+// ────────────────────────────────────────────────────────────────────────
+// Folded regression block — #4145 (self-heal side). saveLocalPatches'
+// preserve-check resolved gsd-pristine/ entries strictly by the manifest-keyed
+// path, so a hash-matching snapshot stored without the gsd-core/ prefix was
+// pushed into regeneration from the incoming release; when upstream changed
+// the file, the candidate hash-mismatched and was discarded. The correct
+// baseline was never consumed and never pruned — the state repeated on every
+// future update. The fix rescues exact-recorded-hash orphans by relocating
+// them to the canonical path.
+// ────────────────────────────────────────────────────────────────────────
+{
+  const { describe: __foldDescribe } = require('node:test');
+  __foldDescribe('folded:bug-4145-saveLocalPatches-orphan-rescue', () => {
+'use strict';
+
+process.env.GSD_TEST_MODE = '1';
+
+const { test, describe, beforeEach } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+const os = require('node:os');
+const crypto = require('node:crypto');
+
+const ROOT = path.join(__dirname, '..');
+const INSTALL = require(path.join(ROOT, 'bin', 'install.js'));
+const { cleanup } = require('./helpers.cjs');
+
+const MANIFEST_NAME = 'gsd-file-manifest.json';
+
+function sha256(content) {
+  return crypto.createHash('sha256').update(content).digest('hex');
+}
+
+describe('Bug #4145: saveLocalPatches rescues hash-matching orphaned pristine snapshots', () => {
+  let tmpDir;
+  let configDir;
+  let newSrcDir;
+  let pristineDir;
+
+  const FILE = 'gsd-core/bin/lib/frontmatter.cjs';
+  const OLD_PRISTINE = '# Old Release Content\nThis is the outgoing pristine.\n';
+  const NEW_RELEASE = '# New Release Content\nUpstream rewrote this file wholesale in v2.\n';
+  const USER_MODIFIED = OLD_PRISTINE + '## User addition\nUser customization here.\n';
+
+  beforeEach((t) => {
+    tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'gsd-4145-slp-'));
+    configDir = path.join(tmpDir, 'config');
+    newSrcDir = path.join(tmpDir, 'new-release-src');
+    pristineDir = path.join(configDir, 'gsd-pristine');
+    fs.mkdirSync(configDir, { recursive: true });
+    fs.mkdirSync(newSrcDir, { recursive: true });
+    t.after(() => {
+      cleanup(tmpDir);
+    });
+  });
+
+  function seedFixture({ orphanRel, orphanContent, canonicalContent, newReleaseContent }) {
+    fs.mkdirSync(path.dirname(path.join(configDir, FILE)), { recursive: true });
+    fs.writeFileSync(path.join(configDir, FILE), USER_MODIFIED);
+    fs.writeFileSync(
+      path.join(configDir, MANIFEST_NAME),
+      JSON.stringify({ version: '1.0.0', files: { [FILE]: sha256(OLD_PRISTINE) } }, null, 2),
+    );
+    if (canonicalContent !== undefined) {
+      fs.mkdirSync(path.dirname(path.join(pristineDir, FILE)), { recursive: true });
+      fs.writeFileSync(path.join(pristineDir, FILE), canonicalContent);
+    }
+    if (orphanRel !== undefined) {
+      fs.mkdirSync(path.dirname(path.join(pristineDir, orphanRel)), { recursive: true });
+      fs.writeFileSync(path.join(pristineDir, orphanRel), orphanContent);
+    }
+    fs.mkdirSync(path.dirname(path.join(newSrcDir, FILE)), { recursive: true });
+    fs.writeFileSync(path.join(newSrcDir, FILE), newReleaseContent);
+  }
+
+  /**
+   * Core regression (self-heal): the hash-matching snapshot sits at
+   * bin/lib/frontmatter.cjs — without the gsd-core/ segment. The new release
+   * changed the file upstream, so regeneration candidates are discarded.
+   * After the fix the orphan is relocated to the canonical manifest-keyed
+   * path and the unprefixed copy no longer lingers.
+   */
+  test('#4145: saveLocalPatches relocates a hash-matching unprefixed orphan to the canonical pristine path', () => {
+    const orphanRel = 'bin/lib/frontmatter.cjs';
+    seedFixture({ orphanRel, orphanContent: OLD_PRISTINE, newReleaseContent: NEW_RELEASE });
+
+    INSTALL.saveLocalPatches(configDir, {
+      packageSrc: newSrcDir, runtime: 'claude', pathPrefix: '$HOME/.claude/', isGlobal: true,
+    });
+
+    const canonical = path.join(pristineDir, FILE);
+    assert.ok(fs.existsSync(canonical), 'canonical prefixed pristine must exist after the update');
+    assert.equal(sha256(fs.readFileSync(canonical, 'utf8')), sha256(OLD_PRISTINE),
+      'relocated baseline must carry the outgoing (recorded-hash) bytes, not new-release bytes');
+    assert.equal(fs.existsSync(path.join(pristineDir, orphanRel)), false,
+      'the unprefixed orphan must not linger once relocated');
+  });
+
+  /**
+   * Stale canonical (new-release bytes) + hash-matching orphan elsewhere:
+   * the stale entry is removed by the #3407 path and then rescued from the
+   * orphan — the file must not end in no-baseline limbo.
+   */
+  test('#4145: rescues after stale-canonical removal when a hash-matching orphan exists', () => {
+    seedFixture({
+      orphanRel: 'legacy/frontmatter.cjs',
+      orphanContent: OLD_PRISTINE,
+      canonicalContent: NEW_RELEASE, // stale — hash mismatch
+      newReleaseContent: NEW_RELEASE,
+    });
+
+    INSTALL.saveLocalPatches(configDir, {
+      packageSrc: newSrcDir, runtime: 'claude', pathPrefix: '$HOME/.claude/', isGlobal: true,
+    });
+
+    const canonical = path.join(pristineDir, FILE);
+    assert.ok(fs.existsSync(canonical), 'canonical pristine must exist after stale removal + rescue');
+    assert.equal(sha256(fs.readFileSync(canonical, 'utf8')), sha256(OLD_PRISTINE),
+      'rescued baseline must carry the recorded-hash bytes');
+    assert.equal(fs.existsSync(path.join(pristineDir, 'legacy', 'frontmatter.cjs')), false,
+      'the orphan must be consumed by the relocation');
+  });
+
+  /** Negative space: no orphan, upstream changed — regeneration discard (#3407) is unchanged. */
+  test('#4145: leaves the baseline absent when no orphan exists and upstream changed', () => {
+    seedFixture({ newReleaseContent: NEW_RELEASE });
+
+    INSTALL.saveLocalPatches(configDir, {
+      packageSrc: newSrcDir, runtime: 'claude', pathPrefix: '$HOME/.claude/', isGlobal: true,
+    });
+
+    assert.equal(fs.existsSync(path.join(pristineDir, FILE)), false,
+      'no hash-matching source exists — the baseline must stay absent (over-broad/no-baseline fallback)');
+  });
+
+  /** Negative space: a mismatching orphan is neither adopted nor deleted. */
+  test('#4145: never adopts nor deletes a hash-mismatching orphan', () => {
+    const orphanRel = 'bin/lib/frontmatter.cjs';
+    seedFixture({ orphanRel, orphanContent: NEW_RELEASE, newReleaseContent: NEW_RELEASE });
+
+    INSTALL.saveLocalPatches(configDir, {
+      packageSrc: newSrcDir, runtime: 'claude', pathPrefix: '$HOME/.claude/', isGlobal: true,
+    });
+
+    assert.equal(fs.existsSync(path.join(pristineDir, FILE)), false,
+      'mismatching bytes must not be written to the canonical pristine path');
+    assert.equal(fs.existsSync(path.join(pristineDir, orphanRel)), true,
+      'pruning files the recorded hashes do not vouch for is not this fix\'s job');
+  });
+
+  /**
+   * Review finding (fix follow-up): two modified files sharing byte-identical
+   * outgoing content. The orphan scan must never consume a path that is
+   * another manifest file's canonical pristine path — otherwise the rescue
+   * would relocate a correct canonical away from its owner and the two files
+   * would ping-pong it between updates. Only genuine non-canonical orphans
+   * are eligible.
+   */
+  test('#4145: does not steal a byte-identical canonical belonging to another modified file', () => {
+    const FILE_B = 'gsd-core/bin/lib/other-file.cjs';
+    const SHARED_OLD = '# Shared Old Content\nByte-identical across two manifest files.\n';
+    // A and B are both user-modified on top of byte-identical outgoing stock,
+    // so both manifest records carry the SAME pristine hash.
+    fs.mkdirSync(path.dirname(path.join(configDir, FILE_B)), { recursive: true });
+    fs.writeFileSync(path.join(configDir, FILE), SHARED_OLD + '## User addition A\nCustom A.\n');
+    fs.writeFileSync(path.join(configDir, FILE_B), SHARED_OLD + '## User addition B\nCustom B.\n');
+    fs.writeFileSync(
+      path.join(configDir, MANIFEST_NAME),
+      JSON.stringify({
+        version: '1.0.0',
+        files: { [FILE]: sha256(SHARED_OLD), [FILE_B]: sha256(SHARED_OLD) },
+      }, null, 2),
+    );
+    // A (processed first) has the ALREADY-correct canonical holding the shared
+    // old bytes. B has no canonical and no orphan — B's only possible hash
+    // match is A's canonical. Without the canonical skip set, B's rescue would
+    // copy A's canonical to B's path and then DELETE A's canonical.
+    fs.mkdirSync(path.dirname(path.join(pristineDir, FILE)), { recursive: true });
+    fs.writeFileSync(path.join(pristineDir, FILE), SHARED_OLD);
+    fs.mkdirSync(path.dirname(path.join(newSrcDir, FILE)), { recursive: true });
+    fs.writeFileSync(path.join(newSrcDir, FILE), NEW_RELEASE);
+    fs.mkdirSync(path.dirname(path.join(newSrcDir, FILE_B)), { recursive: true });
+    fs.writeFileSync(path.join(newSrcDir, FILE_B), NEW_RELEASE);
+
+    INSTALL.saveLocalPatches(configDir, {
+      packageSrc: newSrcDir, runtime: 'claude', pathPrefix: '$HOME/.claude/', isGlobal: true,
+    });
+
+    // A's canonical must survive untouched — never stolen to become B's.
+    assert.ok(fs.existsSync(path.join(pristineDir, FILE)),
+      'the byte-identical canonical of the earlier-processed file must survive');
+    assert.equal(sha256(fs.readFileSync(path.join(pristineDir, FILE), 'utf8')), sha256(SHARED_OLD));
+    // B gains no baseline from A's canonical (falls to regeneration instead).
+    assert.equal(fs.existsSync(path.join(pristineDir, FILE_B)), false,
+      'a canonical path of another file must never be relocated as the rescue source');
+  });
+
+  /** Preserve-path lock: an already-correct canonical stays put; the preserve loop ignores the orphan. */
+  test('#4145: preserves an already-correct canonical and leaves a coexisting identical orphan in place', () => {
+    const orphanRel = 'bin/lib/frontmatter.cjs';
+    seedFixture({
+      orphanRel,
+      orphanContent: OLD_PRISTINE,
+      canonicalContent: OLD_PRISTINE, // already correct
+      newReleaseContent: NEW_RELEASE,
+    });
+
+    INSTALL.saveLocalPatches(configDir, {
+      packageSrc: newSrcDir, runtime: 'claude', pathPrefix: '$HOME/.claude/', isGlobal: true,
+    });
+
+    const canonical = path.join(pristineDir, FILE);
+    assert.ok(fs.existsSync(canonical));
+    assert.equal(sha256(fs.readFileSync(canonical, 'utf8')), sha256(OLD_PRISTINE),
+      'preserved canonical must be byte-identical to before the run');
+    assert.equal(fs.existsSync(path.join(pristineDir, orphanRel)), true,
+      'the preserve path must not disturb unrelated files');
+  });
+});
+  });
+}
diff --git a/tests/reapply-verify-hunks.test.cjs b/tests/reapply-verify-hunks.test.cjs
index 748e56ad5..67c719ab1 100644
--- a/tests/reapply-verify-hunks.test.cjs
+++ b/tests/reapply-verify-hunks.test.cjs
@@ -1170,3 +1170,272 @@ describe('Bug #4086: verifyFile resolves skills entries at the runtime skills ro
 });
   });
 }
+
+
+// ────────────────────────────────────────────────────────────────────────
+// Folded regression block — #4145 (a hash-matching gsd-pristine/ baseline
+// stored without the gsd-core/ prefix is never resolved). verifyFile() joined
+// the manifest-keyed path strictly; when stat missed and a hash was recorded
+// it reported OK_NO_BASELINE even though byte-correct content sat elsewhere
+// under gsd-pristine/. The fix consults the recorded pristine_hashes — the
+// same authority the #3657 drift guard trusts — and adopts an exact-hash
+// match found anywhere in the tree.
+// ────────────────────────────────────────────────────────────────────────
+{
+  const { describe: __foldDescribe } = require('node:test');
+  __foldDescribe('folded:bug-4145-pristine-prefix-resolution', () => {
+'use strict';
+
+process.env.GSD_TEST_MODE = '1';
+
+const { test, describe, before, after } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const os = require('node:os');
+const path = require('node:path');
+const crypto = require('node:crypto');
+const { cleanup } = require('./helpers.cjs');
+const { runNode } = require('./helpers/process-seam.cjs');
+
+const ROOT = path.join(__dirname, '..');
+const SCRIPT = path.join(ROOT, 'gsd-core', 'bin', 'verify-reapply-patches.cjs');
+const { REASON } = require(SCRIPT);
+const { findPristineByHash } = require(
+  path.join(ROOT, 'gsd-core', 'bin', 'lib', 'pristine-baseline.cjs'),
+);
+
+let tmpRoot;
+let patchesDir;
+let configDir;
+let pristineDir;
+
+function sha256(content) {
+  return crypto.createHash('sha256').update(content).digest('hex');
+}
+
+function writeFile(absPath, content) {
+  fs.mkdirSync(path.dirname(absPath), { recursive: true });
+  fs.writeFileSync(absPath, content);
+}
+
+function writeBackupMeta(pristine_hashes) {
+  writeFile(path.join(patchesDir, 'backup-meta.json'), JSON.stringify({ pristine_hashes }, null, 2));
+}
+
+function resetFixture() {
+  for (const dir of [patchesDir, configDir, pristineDir]) {
+    cleanup(dir);
+  }
+  fs.mkdirSync(patchesDir);
+  fs.mkdirSync(configDir);
+  fs.mkdirSync(pristineDir);
+}
+
+function runVerifier() {
+  const r = runNode([
+    SCRIPT,
+    '--patches-dir', patchesDir,
+    '--config-dir',  configDir,
+    '--pristine-dir', pristineDir,
+    '--json',
+  ], { timeoutMs: 30_000 });
+  return {
+    status: r.exitCode,
+    report: r.stdout && r.stdout.length ? JSON.parse(r.stdout) : null,
+  };
+}
+
+before(() => {
+  tmpRoot = fs.mkdtempSync(path.join(os.tmpdir(), 'gsd-4145-'));
+  patchesDir = path.join(tmpRoot, 'patches');
+  configDir = path.join(tmpRoot, 'installed');
+  pristineDir = path.join(tmpRoot, 'pristine');
+  resetFixture();
+});
+
+after(() => {
+  cleanup(tmpRoot);
+});
+
+describe('Bug #4145: hash-matching prefix-less pristine baseline is resolved', () => {
+  /**
+   * Core regression. The manifest key is `gsd-core/bin/lib/frontmatter.cjs`
+   * but the snapshot sits at `bin/lib/frontmatter.cjs` — one segment away
+   * from the joined path. Its SHA-256 equals the recorded pristine_hashes
+   * entry. The upstream release replaced the file wholesale and only the
+   * user's line survived the merge, so a verifier that recovered the
+   * baseline computes exactly one user-added line (present → exit 0,
+   * no_baseline 0), while the pre-fix run reported ok_no_baseline.
+   */
+  test('#4145: resolves a hash-matching prefix-less pristine baseline instead of reporting ok_no_baseline', () => {
+    resetFixture();
+    const FILE = 'gsd-core/bin/lib/frontmatter.cjs';
+    const OLD_PRISTINE =
+      'outgoing pristine stock line one with substantial content\n' +
+      'outgoing pristine stock line two also substantial content\n';
+    const USER_LINE = 'user customization line that must survive the reapply merge';
+    const backupContent = OLD_PRISTINE + USER_LINE + '\n';
+    const installedContent =
+      'incoming upstream replacement line with substantial content\n' + USER_LINE + '\n';
+
+    writeBackupMeta({ [FILE]: sha256(OLD_PRISTINE) });
+    writeFile(path.join(patchesDir, FILE), backupContent);
+    writeFile(path.join(configDir, FILE), installedContent);
+    // The orphan: same bytes, stored WITHOUT the gsd-core/ prefix.
+    writeFile(path.join(pristineDir, 'bin', 'lib', 'frontmatter.cjs'), OLD_PRISTINE);
+
+    const { status, report } = runVerifier();
+
+    assert.equal(status, 0, `expected exit 0; report=${JSON.stringify(report)}`);
+    assert.equal(report.no_baseline, 0, 'a hash-matching baseline was on disk — it must be resolved');
+    assert.deepEqual(report.no_baseline_files, []);
+    assert.equal(report.failures, 0);
+    const r0 = report.results[0];
+    assert.equal(r0.status, 'ok');
+    assert.notEqual(r0.reason, REASON.OK_NO_BASELINE);
+  });
+
+  /** Negative space: nothing anywhere under gsd-pristine/ matches the record. */
+  test('#4145: still reports ok_no_baseline when the recorded hash matches nothing under gsd-pristine', () => {
+    resetFixture();
+    const FILE = 'gsd-core/bin/lib/frontmatter.cjs';
+    const backupContent =
+      'upstream line present in the backup of the outgoing release\n' +
+      'model: sonnet — the user customisation line in the backup file\n';
+    const installedContent =
+      'replacement upstream line in the newer release version\n' +
+      'model: sonnet — the user customisation line in the backup file\n';
+
+    writeBackupMeta({ [FILE]: 'deadbeef00000000000000000000000000000000000000000000000000000001' });
+    writeFile(path.join(patchesDir, FILE), backupContent);
+    writeFile(path.join(configDir, FILE), installedContent);
+    // No pristine file anywhere.
+
+    const { status, report } = runVerifier();
+
+    assert.equal(status, 0, 'no-baseline is advisory, never a failure');
+    assert.equal(report.no_baseline, 1);
+    assert.equal(report.results[0].reason, REASON.OK_NO_BASELINE);
+  });
+
+  /**
+   * Negative space: an orphan whose bytes do NOT hash to the record is never
+   * adopted — only exact recorded-hash matches are accepted.
+   */
+  test('#4145: never adopts a hash-mismatching orphan — only exact recorded-hash matches', () => {
+    resetFixture();
+    const FILE = 'gsd-core/bin/lib/frontmatter.cjs';
+    const OLD_PRISTINE = 'outgoing pristine bytes that the record hashes\n';
+    const OTHER_CONTENT = 'some other release snapshot with different bytes\n';
+
+    writeBackupMeta({ [FILE]: sha256(OLD_PRISTINE) });
+    writeFile(path.join(patchesDir, FILE), 'outgoing pristine bytes that the record hashes\nuser line\n');
+    writeFile(path.join(configDir, FILE), 'user line\n');
+    // Orphan exists but hashes to something else.
+    writeFile(path.join(pristineDir, 'bin', 'lib', 'frontmatter.cjs'), OTHER_CONTENT);
+
+    const { status, report } = runVerifier();
+
+    assert.equal(status, 0);
+    assert.equal(report.no_baseline, 1, 'a mismatching orphan is not a baseline');
+    assert.equal(report.results[0].reason, REASON.OK_NO_BASELINE);
+  });
+
+  /**
+   * Precedence lock: the canonical prefixed path still resolves exactly as
+   * today even when an identical-content orphan also exists — the strict join
+   * stays first, and the verifier (read-only) leaves the orphan untouched.
+   */
+  test('#4145: prefixed canonical baseline resolves exactly as today when an identical orphan also exists', () => {
+    resetFixture();
+    const FILE = 'gsd-core/workflows/execute-phase.md';
+    const pristineContent = 'stock workflow line long enough to pass the significance threshold\n';
+    const droppedLine = 'user workflow customisation that was lost in the merge operation';
+    const backupContent = pristineContent + droppedLine + '\n';
+    const installedContent = pristineContent; // user line dropped — real failure
+
+    writeBackupMeta({ [FILE]: sha256(pristineContent) });
+    writeFile(path.join(patchesDir, FILE), backupContent);
+    writeFile(path.join(configDir, FILE), installedContent);
+    writeFile(path.join(pristineDir, FILE), pristineContent);
+    const orphanPath = path.join(pristineDir, 'workflows', 'execute-phase.md');
+    writeFile(orphanPath, pristineContent);
+
+    const { status, report } = runVerifier();
+
+    assert.equal(status, 1, 'the dropped user line must still be caught via the canonical baseline');
+    const r0 = report.results[0];
+    assert.equal(r0.status, 'fail');
+    assert.equal(r0.reason, REASON.FAIL_USER_LINES_MISSING);
+    assert.ok(r0.missing.includes(droppedLine));
+    // Read-only verifier: the orphan is never relocated or pruned by a verify run.
+    assert.equal(fs.existsSync(orphanPath), true, 'verifier must not mutate gsd-pristine/');
+  });
+
+  /**
+   * Drift-path lock: a hash-MISMATCHING canonical snapshot still reports
+   * OK_PRISTINE_DRIFT_DETECTED (#3657) — the recovery scan must not reach the
+   * drift case.
+   */
+  test('#4145: canonical-path drift still reports ok_pristine_drift_detected even when a hash-matching orphan exists', () => {
+    resetFixture();
+    const FILE = 'gsd-core/agents/gsd-executor.md';
+    const oldPristine = 'old pristine line that was present when backup was captured\n';
+    const newPristine = 'refreshed upstream line in the newer pristine snapshot\n';
+    const userLine = 'user customisation line that should be preserved across updates';
+
+    writeBackupMeta({ [FILE]: sha256(oldPristine) });
+    writeFile(path.join(patchesDir, FILE), oldPristine + userLine + '\n');
+    writeFile(path.join(configDir, FILE), newPristine + userLine + '\n');
+    writeFile(path.join(pristineDir, FILE), newPristine); // canonical drifted
+    // A hash-matching orphan exists elsewhere — drift must still win.
+    writeFile(path.join(pristineDir, 'agents', 'gsd-executor.md'), oldPristine);
+
+    const { status, report } = runVerifier();
+
+    assert.equal(status, 0);
+    const r0 = report.results[0];
+    assert.equal(r0.reason, REASON.OK_PRISTINE_DRIFT_DETECTED,
+      `expected the untouched #3657 drift posture; got ${r0.reason}`);
+    assert.equal(report.drifted, 1);
+  });
+
+  /** Module unit: deterministic sorted-first match, symlink skip, absent dir. */
+  test('#4145: findPristineByHash returns the sorted-first match, skips symlinks, and null on an absent dir', () => {
+    const root = fs.mkdtempSync(path.join(os.tmpdir(), 'gsd-4145-unit-'));
+    const symRoot = fs.mkdtempSync(path.join(os.tmpdir(), 'gsd-4145-sym-'));
+    const outsideRoot = fs.mkdtempSync(path.join(os.tmpdir(), 'gsd-4145-out-'));
+    try {
+      const contentA = 'identical bytes that two snapshots happen to share\n';
+      const hashA = sha256(contentA);
+      writeFile(path.join(root, 'zz-dir', 'late-match.md'), contentA);
+      writeFile(path.join(root, 'aa.txt'), contentA);
+
+      assert.equal(findPristineByHash(root, hashA), 'aa.txt',
+        'sorted-first match wins deterministically');
+      assert.equal(findPristineByHash(root, hashA, 'aa.txt'), 'zz-dir/late-match.md',
+        'skipRel is never returned');
+      assert.equal(findPristineByHash(root, hashA, new Set(['aa.txt', 'zz-dir/late-match.md'])), null,
+        'every member of a skip Set is excluded (canonical-path protection)');
+      assert.equal(findPristineByHash(root, sha256('no such content anywhere here\n')), null,
+        'no match resolves to null');
+      assert.equal(findPristineByHash(path.join(root, 'absent'), hashA), null,
+        'absent dir resolves to null');
+
+      // A symlink is never followed, even when its target would hash-match.
+      // The target lives OUTSIDE symRoot so the only hashable entry inside the
+      // scanned tree is the symlink itself.
+      const outsideTarget = path.join(outsideRoot, 'outside-target.md');
+      fs.writeFileSync(outsideTarget, contentA);
+      fs.symlinkSync(outsideTarget, path.join(symRoot, 'sym.md'));
+      assert.equal(findPristineByHash(symRoot, hashA), null,
+        'symlinked candidates are skipped, not followed');
+    } finally {
+      cleanup(root);
+      cleanup(symRoot);
+      cleanup(outsideRoot);
+    }
+  });
+});
+  });
+}