fix(cli/runtime): key dependency-staleness on corePath, not only the pyproject hash

apps/openant-cli/internal/python/runtime.go

@@ -201,8 +201,7 @@ func CheckOpenantInstalled(pythonPath string) error {
 	}
 
 	// Save dependency hash so CheckDepsStale knows this is the baseline.
-	pyprojectPath := filepath.Join(corePath, "pyproject.toml")
-	if h, err := hashFile(pyprojectPath); err == nil {
+	if h, err := depsHash(corePath); err == nil {
 		if err := writeStoredHash(h); err != nil {
 			fmt.Fprintf(os.Stderr,
 				"warning: could not save dependency hash at %s: %v (next run may reinstall)\n",
@@ -285,13 +284,26 @@ func readStoredHash() string { return readHashAt(depsHashPath()) }
 // writeStoredHash saves the dependency hash to the venv marker file.
 func writeStoredHash(hash string) error { return writeHashAt(depsHashPath(), hash) }
 
+// depsHash keys the dependency stamp on BOTH pyproject.toml contents AND corePath (the
+// editable-install source). The managed venv is a single global path shared across worktrees;
+// without corePath in the key, two worktrees with identical pyproject.toml share one editable
+// install and a binary built in one silently imports the other's source. Including corePath forces
+// a reinstall (re-pointing the editable install) when the active source changes.
+func depsHash(corePath string) (string, error) {
+	pyproject, err := os.ReadFile(filepath.Join(corePath, "pyproject.toml"))
+	if err != nil {
+		return "", err
+	}
+	sum := sha256.Sum256(append([]byte(corePath+"\x00"), pyproject...))
+	return hex.EncodeToString(sum[:]), nil
+}
+
 // depsStalenessAt inspects pyproject.toml at corePath and the hash stored at
 // hashPath, and reports whether a reinstall is needed. The boolean is true
 // when deps are stale (i.e. the hash differs and a reinstall is warranted).
 // The caller is expected to skip the check on any error.
 func depsStalenessAt(corePath, hashPath string) (stale bool, currentHash string, err error) {
-	pyprojectPath := filepath.Join(corePath, "pyproject.toml")
-	currentHash, err = hashFile(pyprojectPath)
+	currentHash, err = depsHash(corePath)
 	if err != nil {
 		return false, "", err
 	}

apps/openant-cli/internal/python/runtime_corepath_test.go

@@ -0,0 +1,53 @@
+package python
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+// Regression test: the dependency-staleness check keyed only on
+// pyproject.toml content, blind to corePath. The managed venv is a single global path shared across
+// all worktrees; with two worktrees whose pyproject.toml is identical, the staleness check reports
+// "not stale" even though the venv's editable install (`pip install -e <corePath>`) points at the
+// OTHER worktree's source — so a binary built in worktree B silently imports worktree A's Python.
+// Fix: key staleness on corePath as well, so switching the editable-install source is detected.
+func TestDepsStalenessDetectsCorePathChange(t *testing.T) {
+	const pyproject = "[project]\nname = \"openant\"\nversion = \"1.0.0\"\n"
+
+	coreA := t.TempDir()
+	coreB := t.TempDir()
+	if err := os.WriteFile(filepath.Join(coreA, "pyproject.toml"), []byte(pyproject), 0644); err != nil {
+		t.Fatal(err)
+	}
+	// coreB has BYTE-IDENTICAL pyproject.toml — only the corePath differs.
+	if err := os.WriteFile(filepath.Join(coreB, "pyproject.toml"), []byte(pyproject), 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	hashPath := filepath.Join(t.TempDir(), ".deps-hash")
+
+	// Baseline: install was done from coreA -> stamp coreA's hash.
+	_, hashA, err := depsStalenessAt(coreA, hashPath)
+	if err != nil {
+		t.Fatalf("depsStalenessAt(coreA): %v", err)
+	}
+	if err := writeHashAt(hashPath, hashA); err != nil {
+		t.Fatalf("writeHashAt: %v", err)
+	}
+
+	// Same corePath -> not stale.
+	if staleA, _, _ := depsStalenessAt(coreA, hashPath); staleA {
+		t.Fatalf("same corePath reported stale (should be up-to-date)")
+	}
+
+	// Different corePath, identical pyproject -> MUST be stale: otherwise the two worktrees share
+	// one editable install and the binary imports the wrong source.
+	staleB, _, err := depsStalenessAt(coreB, hashPath)
+	if err != nil {
+		t.Fatalf("depsStalenessAt(coreB): %v", err)
+	}
+	if !staleB {
+		t.Fatalf("corePath change (identical pyproject) not detected as stale -> worktrees share the editable install")
+	}
+}