Shared app servers: the PreToolUse hook leaves a ticket naming the calling session, the MCP server takes it per call (middleware), so two sessions of one app on one Harbor server act as themselves; i_am checks instead of binding and is allowed under a stop

harbor/mcp_server.py

@@ -5,6 +5,7 @@ Run with the agent's identity fixed in its environment (it cannot be changed fro
 The project comes from $HARBOR_PROJECT or the .harbor.toml above the working directory. The human is refused.
 """
 import asyncio
+import contextvars
 import os
 import threading
 import time
@@ -14,8 +15,9 @@ os.environ.setdefault("FASTMCP_CHECK_FOR_UPDATES", "off")      # no network call
 os.environ.setdefault("FASTMCP_SHOW_SERVER_BANNER", "false")
 from fastmcp import FastMCP  # noqa: E402
 from fastmcp.exceptions import ToolError  # noqa: E402
+from fastmcp.server.middleware import Middleware  # noqa: E402
 
-from . import projects  # noqa: E402
+from . import projects, sessions  # noqa: E402
 from .core import OPEN_ITEM_STATES, Harbor, HarborError  # noqa: E402
 
 INSTRUCTIONS = """Harbor is the team's shared coordination store: messages in threads, acknowledgements, claims, a
@@ -55,6 +57,30 @@ ClaimKind = Literal["draft", "naming", "edit", "review", "band"]
 mcp = FastMCP("harbor", instructions=INSTRUCTIONS)
 _lock = threading.Lock()
 _state = {"seen": 0.0}
+_caller = contextvars.ContextVar("harbor_caller", default=None)    # the session behind the current tool call
+
+
+class SessionIdentity(Middleware):
+    """One app may share this server between several sessions (Codex and Codex2). The app's PreToolUse hook names
+    the calling session in a ticket; take it so this call runs as that agent (harbor.sessions)."""
+
+    async def on_call_tool(self, context, call_next):
+        agent = None
+        try:
+            message = context.message
+            with _lock:
+                agent = sessions.take(harbor(), os.environ.get("HARBOR_HOST", ""), message.name,
+                                      dict(message.arguments or {}))
+        except Exception:   # noqa: BLE001 - identity falls back to the server's own
+            agent = None
+        token = _caller.set(agent)
+        try:
+            return await call_next(context)
+        finally:
+            _caller.reset(token)
+
+
+mcp.add_middleware(SessionIdentity())
 
 
 def harbor():
@@ -67,9 +93,9 @@ def harbor():
 
 def me():
     h = harbor()
-    # a session bound with i_am, else the agent its working folder names (when it runs in the same app as the
-    # installed one: Codex and Codex2 share the Codex app), else the installed one
-    agent = _state.get("bound") or h.project.session_identity(os.environ.get("HARBOR_AGENT"), os.getcwd()) or ""
+    # the session its app's hook named for this call (several sessions can share this server), else the agent the
+    # server's working folder names when it runs in the same app as the installed one, else the installed one
+    agent = (_caller.get() or h.project.session_identity(os.environ.get("HARBOR_AGENT"), os.getcwd()) or "")
     if agent not in h.project.ai_names:
         raise HarborError(f"HARBOR_AGENT must be one of {', '.join(h.project.ai_names)} (set it in this server's MCP "
                           "config)")
@@ -125,22 +151,19 @@ def run(fn):
 
 @mcp.tool
 def i_am(agent: str) -> dict:
-    """Say which of the project's agents this session is, when one app runs several (Codex and Codex2). Call it once
-    at the start of the session if your instructions or your working folder name you; only an agent of the same
-    app is accepted, and a server already bound to another agent refuses."""
+    """Check which of the project's agents Harbor takes this session to be, when one app runs several (Codex and
+    Codex2). Call it at the start of the session with the name your instructions give you. Harbor knows the session
+    from its working folder (through the app's hooks); if the answer is not you, stop and tell the user."""
     def do(h):
-        pinned = os.environ.get("HARBOR_AGENT") or ""
         if agent not in h.project.ai_names:
             raise HarborError(f"{agent} is not one of {', '.join(h.project.ai_names)}")
-        if pinned and h.project.host_of(agent) != h.project.host_of(pinned):
-            raise HarborError(f"{agent} runs in another app ({h.project.host_of(agent) or 'unknown'}), not this one")
-        bound = _state.get("bound")
-        if bound and bound != agent:
-            raise HarborError(f"this Harbor server is already {bound}: the app shares one server between sessions, "
-                              "so give each session its own app profile instead")
-        _state["bound"] = agent
-        return {"you_are": agent, "working_folder": os.getcwd(),
-                "folder_says": h.project.identity_for(os.getcwd())}
+        seen = me()
+        out = {"you_are": seen, "matches": seen == agent}
+        if seen != agent:
+            out["fix"] = (f"Harbor sees this session as {seen}, not {agent}. Check that this session works in "
+                          f"{agent}'s own worktree and that the app's Harbor hooks are installed and trusted; do no "
+                          "work until it matches.")
+        return out
     return run(do)