From ab69ea113061c57676a1241ee39e332246b4078f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Franti=C5=A1ek=20Boh=C3=A1=C4=8Dek?=
 <frantisek.bohacek@braiinsforge.com>
Date: Tue, 20 Oct 2026 18:04:02 +0200
Subject: [PATCH] Check shared dirs: link, target, manifest, and removal on
 undeclare

---
 checks/default.nix | 59 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)

diff --git a/checks/default.nix b/checks/default.nix
index 87cd52c082230470f77435693803f9180aa7e6be..39fd386a8731773d6b4d25ef023e85c159fbb7be 100644
--- a/checks/default.nix
+++ b/checks/default.nix
@@ -265,6 +265,49 @@ in
     [ "$(cat $s/CLAUDE.md)" = edited ] || fail "user file modified"
   '';
 
+  # A shared directory is a managed link to the other launcher's copy. The copy
+  # is created on demand, so the link works whichever launcher starts first, and
+  # undeclaring the share removes the link but never the data behind it.
+  shared-dirs =
+    let
+      withShare = share: {
+        claude.enable = true;
+        launchers.claude-work.agent = "claude";
+        launchers.claude-pers = {
+          agent = "claude";
+          sharedDirs = share;
+        };
+      };
+      sharing = mkEnvironment {
+        inherit pkgs;
+        modules = [
+          stubs
+          (withShare { projects = "claude-work"; })
+        ];
+      };
+      alone = mkEnvironment {
+        inherit pkgs;
+        modules = [
+          stubs
+          (withShare { })
+        ];
+      };
+      work = "$HOME/.local/agent-environments/claude-work";
+      pers = "$HOME/.local/agent-environments/claude-pers";
+    in
+    runTest "shared-dirs" ''
+      ${sharing.launchers.claude-pers}/bin/claude-pers
+      [ -d ${work}/projects ] || fail "shared target not created"
+      [ "$(readlink ${pers}/projects)" = ${work}/projects ] || fail "link: $(readlink ${pers}/projects)"
+      grep -qx projects ${pers}/.agent-environments-managed || fail "link not in manifest"
+      echo data >${pers}/projects/session.jsonl
+      [ "$(cat ${work}/projects/session.jsonl)" = data ] || fail "write did not land in the shared dir"
+
+      ${alone.launchers.claude-pers}/bin/claude-pers
+      [ ! -L ${pers}/projects ] || fail "undeclared share still linked"
+      [ "$(cat ${work}/projects/session.jsonl)" = data ] || fail "shared data removed with the link"
+    '';
+
   # The launcher's own bookkeeping paths must not write through symlinks into
   # files or directories outside the state dir.
   no-writes-through-symlinks = runTest "no-writes-through-symlinks" ''
@@ -439,5 +482,21 @@ in
           src = skillSrc "x";
         }).drvPath
       ).success;
+    # A shared dir must name another, existing launcher and a safe path component.
+    assert lib.all (share: fails [
+      stubs
+      {
+        claude.enable = true;
+        launchers.x.agent = "claude";
+        launchers.y = {
+          agent = "claude";
+          sharedDirs = share;
+        };
+      }
+    ]) [
+      { projects = "nope"; }
+      { projects = "y"; }
+      { "../escape" = "x"; }
+    ];
     pkgs.runCommand "agent-environments-eval-errors" { } "touch $out";
 }