fix(sync): resolve versioned launcher symlinks

CHANGELOG.md

@@ -14,6 +14,9 @@
   SQLite value whether a real backup contains an active draft or legitimately
   contains none.
 
+- Made relocatable launchers resolve stable user-bin symlinks to their physical
+  versioned bundle before loading matching binaries and helpers.
+
 - Closed the native candidate warning gate with checked path and HTTP response
   bounds, strict GCC and Clang builds, full Clang ASan/UBSan validation, and a
   stable concurrent object-I/O MTP double. Rebuilt the desktop, current Android

docs/sync_rollout_readiness.md

@@ -26,6 +26,8 @@ the separately authorized rollout are complete.
    `trainlog-syncd`, the production generation MTP adapter and their matching
    Python codecs. User units must point only into one versioned bundle; they
    must not combine a packaged binary with helpers from a live checkout.
+   Stable user-bin symlinks are supported: each launcher resolves the link to
+   its physical bundle before locating `libexec` and `tools`.
 2. `assembleDebug` is development evidence only. Rollout requires the existing
    release signing identity, verification of its public certificate and a valid
    increasing `versionCode`. A bounded `TRAINLOG_ANDROID_VERSION_CODE` build

tests/test_sync_deployment_tools.py

@@ -66,6 +66,16 @@ class DeploymentToolsTest(unittest.TestCase):
             self.assertTrue((output / "bin/trainlog-sync-once").is_file())
             self.assertTrue((output / "bin/trainlog-syncd").is_file())
             self.assertTrue((output / "libexec/trainlog-sync-once").is_file())
+            stable_bin = Path(directory) / "stable-bin"
+            stable_bin.mkdir()
+            (stable_bin / "trainlog").symlink_to(output / "bin/trainlog")
+            linked = subprocess.run(
+                [str(stable_bin / "trainlog"), "--version"],
+                capture_output=True,
+                text=True,
+            )
+            self.assertEqual(linked.returncode, 0, linked.stderr)
+            self.assertIn("trainlog 0.1.2", linked.stdout)
             self.assertTrue(
                 any(
                     row["path"] == "tools/trainlog_syncd.py"

tools/package_sync_candidate.py

@@ -71,15 +71,15 @@ def main() -> int:
         shutil.copy2(source, args.output / "catalog" / source.name)
     launcher = args.output / "bin/trainlog"
     launcher.write_text(
-        '#!/bin/sh\nset -eu\nroot=$(CDPATH= cd -- "$(dirname -- "$0")/.." && pwd)\nexport TRAINLOG_SYNC_TOOLS_DIR="$root/tools"\nexport TRAINLOG_SYNC_MTP_ADAPTER="$root/libexec/trainlog-generation-mtp-adapter"\nexec "$root/libexec/trainlog" "$@"\n'
+        '#!/bin/sh\nset -eu\nscript=$(readlink -f -- "$0")\nroot=$(CDPATH= cd -- "$(dirname -- "$script")/.." && pwd)\nexport TRAINLOG_SYNC_TOOLS_DIR="$root/tools"\nexport TRAINLOG_SYNC_MTP_ADAPTER="$root/libexec/trainlog-generation-mtp-adapter"\nexec "$root/libexec/trainlog" "$@"\n'
     )
     sync_once_launcher = args.output / "bin/trainlog-sync-once"
     sync_once_launcher.write_text(
-        '#!/bin/sh\nset -eu\nroot=$(CDPATH= cd -- "$(dirname -- "$0")/.." && pwd)\nexec "$root/libexec/trainlog-sync-once" "$@"\n'
+        '#!/bin/sh\nset -eu\nscript=$(readlink -f -- "$0")\nroot=$(CDPATH= cd -- "$(dirname -- "$script")/.." && pwd)\nexec "$root/libexec/trainlog-sync-once" "$@"\n'
     )
     syncd_launcher = args.output / "bin/trainlog-syncd"
     syncd_launcher.write_text(
-        '#!/bin/sh\nset -eu\nroot=$(CDPATH= cd -- "$(dirname -- "$0")/.." && pwd)\nexec python3 "$root/tools/trainlog_syncd.py" --sync-once "$root/bin/trainlog-sync-once" "$@"\n'
+        '#!/bin/sh\nset -eu\nscript=$(readlink -f -- "$0")\nroot=$(CDPATH= cd -- "$(dirname -- "$script")/.." && pwd)\nexec python3 "$root/tools/trainlog_syncd.py" --sync-once "$root/bin/trainlog-sync-once" "$@"\n'
     )
     files = sorted(path for path in args.output.rglob("*") if path.is_file())
     inventory = {
@@ -114,6 +114,7 @@ def main() -> int:
             "libudev",
             "libmtp",
             "notcurses",
+            "coreutils-readlink",
         ],
         "files": [
             {