From 33260b4cb5856a62bf2442e8eac8521885c4c290 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] Add launchers.<cmd>.sharedDirs: share a state-dir directory
 between launchers

Launchers with different ids share nothing, which is right for logins but
not for Claude's projects (sessions and memory) or Codex's memories. A
shared dir is a managed symlink to the other launcher's copy, created on
demand so the link holds whichever launcher starts first, and removed with
the declaration while the data stays.
---
 README.md            |  1 +
 modules/launcher.nix | 29 ++++++++++++++++++++++++++++-
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index c50285371d85bf931a835e6faba0b57f9928e915..3f8ffc9df112e039b600db4bab43f2dfbbfddd6c 100644
--- a/README.md
+++ b/README.md
@@ -74,6 +74,7 @@ Runnable examples: [`examples/basic`](examples/basic) and
 | `packages` | Packages put on every launcher's `PATH`, e.g. tools that hooks in `claude.settings` call. |
 | `modules.skills.<name>.enable` | Declared by `mkSkillModule`; adds that skill. |
 | `launchers.<cmd>.{agent,id,stateDir}` | A command. `id` defaults to the command name; `stateDir` defaults to `~/.local/agent-environments/<id>`; it must be absolute or start with `~/`, and is taken literally. |
+| `launchers.<cmd>.sharedDirs.<dir>` | Share one directory of the state dir with another launcher, e.g. `projects = "claude-work"` for sessions and memory across logins. A managed symlink to that launcher's `<stateDir>/<dir>`, created if missing. |
 | `companions.enable` | Put every launcher of the environment on the agent's `PATH` (as companions, which cannot start companions themselves) and add a generated `companions` skill listing each one with its non-interactive call. Launchers export `AGENT_ENV_LAUNCHER` (their command name). |
 
 ## What a launcher does
diff --git a/modules/launcher.nix b/modules/launcher.nix
index 65ed8388e76db42cfb8234cf86d5fd5b38f44ea8..06947a67c39d311f4746dc7f826d55ca3b137ffa 100644
--- a/modules/launcher.nix
+++ b/modules/launcher.nix
@@ -41,6 +41,11 @@ let
     let
       agent = build.agents.${launcher.agent};
       links = managedLinks agent;
+      # Shared directories: relative path -> shell expression for the other
+      # launcher's copy, which may live under $HOME.
+      shared = lib.mapAttrs (
+        dir: other: "${stateDirShell config.launchers.${other}.stateDir}/${lib.escapeShellArg dir}"
+      ) launcher.sharedDirs;
       runtimePath = lib.makeBinPath (
         lib.optional (companionBin != null) companionBin ++ build.runtimeInputs
       );
@@ -65,6 +70,7 @@ let
         ${
           lib.concatStrings (
             lib.mapAttrsToList (p: target: "  [${lib.escapeShellArg p}]=${lib.escapeShellArg target}\n") links
+            ++ lib.mapAttrsToList (p: target: "  [${lib.escapeShellArg p}]=${target}\n") shared
           )
         })
         declare -A owned=()
@@ -92,6 +98,10 @@ let
           fi
         done
 
+        # A shared directory is created where it lives, so the link never dangles.
+        ${lib.concatStrings (
+          lib.mapAttrsToList (p: _: "${mkdir} -p \"\${wanted[${lib.escapeShellArg p}]}\"\n") shared
+        )}
         for p in "''${!wanted[@]}"; do
           # No -f: a unique temp name that already exists is an error, not something to delete.
           tmp="$state/$p.agent-env-tmp.$$"
@@ -141,6 +151,11 @@ in
               default = "~/.local/agent-environments/${config.id}";
               description = "State dir (CLAUDE_CONFIG_DIR / CODEX_HOME): an absolute path, or one starting with ~/ for $HOME. Taken literally.";
             };
+            sharedDirs = mkOption {
+              type = types.attrsOf types.str;
+              default = { };
+              description = "Directories of the state dir shared with another launcher: `<dir> = \"<launcher>\"` links <dir> to that launcher's <dir>, creating it if missing.";
+            };
           };
         }
       )
@@ -184,7 +199,19 @@ in
           assertion = config.build.agents ? ${l.agent};
           message = "launcher '${name}' uses ${l.agent}, but ${l.agent}.enable is false";
         }
-      ]) config.launchers
+      ]
+      ++ lib.concatLists (
+        lib.mapAttrsToList (dir: other: [
+          {
+            assertion = agentEnvLib.safeName dir;
+            message = "launcher '${name}': shared dir '${dir}' is not a safe path component";
+          }
+          {
+            assertion = other != name && config.launchers ? ${other};
+            message = "launcher '${name}': shared dir '${dir}' names '${other}', which is not another launcher";
+          }
+        ]) l.sharedDirs
+      )) config.launchers
     );
   };
 }