diff --git a/docs/investigations/discovery-http-server.md b/docs/investigations/discovery-http-server.md
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+# Investigation: TypeScript `DiscoveryHttpServer` vs the Python SDK (#77)
+
+Checked against: Python `nitrostack-python-sdk` `develop` at `fb0faf8`;
+TypeScript `nitrocloudofficial/nitrostack` at `10859bef`. Date: 2026-11-03.
+
+## 1. What the TypeScript server does
+File: `typescript/packages/core/src/core/transports/discovery-http-server.ts`
+
+- Options (`:11-18`): `port`, `autoRetry`, `maxRetries`.
+- Defaults (`:53-67`): with an options object, `port` 3005, `autoRetry` true,
+  `maxRetries` 10. With the legacy numeric constructor, `autoRetry` false.
+- Retry (`:23-45`, `:97-109`): when `autoRetry` is on, `findAvailablePort` probes
+  `port`, `port+1`, ... up to `maxRetries` using a throwaway `net` server, then
+  listens on the first free port. It throws if none is free.
+- Without `autoRetry`, an `EADDRINUSE` error is logged with a hint to set
+  `OAUTH_DISCOVERY_PORT` and the start promise rejects (`:117-127`).
+- Reporting (`:93-95`): `getPort()` returns the port actually used.
+- Routing (`:72-87`): exact-match path handlers registered with `on(path, handler)`;
+  unknown paths return 404. Bind address is not passed to `listen`, so Node's default applies.
+
+## 2. Consumers in the TypeScript stack
+| Consumer | File:line | Use |
+|---|---|---|
+| `OAuthModule.start()` | `core/oauth-module.ts:560-569` | In stdio mode, creates the server with `autoRetry` (env `OAUTH_DISCOVERY_AUTO_RETRY`, default on, `:549`) and `maxRetries: 50` (`:554`), reads `getPort()`, then emits the port to the client. |
+| `OAuthModule.start()` fallback | `core/oauth-module.ts:610-617` | Starts the same server if the HTTP transport is missing in http/dual mode. |
+| `registerDiscoveryHandlers` | `core/oauth-module.ts:667-673` | Registers `/.well-known/oauth-authorization-server`, `/.well-known/oauth-protected-resource`, and `/oauth/v2/register` when client registration is enabled. |
+| `notifyClientAboutOAuth` | `core/oauth-module.ts:639-657` | Writes `[NITROSTACK_OAUTH]{...}[/NITROSTACK_OAUTH]` to stderr with the actual port and well-known URLs. |
+| CLI template docs | `packages/cli/templates/typescript-oauth/OAUTH_SETUP.md:97,210,350` | Documents port 3005 and the startup log line. |
+| Tests | `transport.http.test.ts:111-172`, `transports.test.ts:244-288`, `oauth.extended.test.ts:39-41` | Cover the retry and no-retry options (ports 34508/34509). |
+
+Within `typescript/packages`, outside tests and templates, the only consumer is
+`OAuthModule`. No other code in that tree (including the CLI sources) references it.
+**Not checked:** NitroStudio's source is not in this repository, so whether Studio
+parses the `[NITROSTACK_OAUTH]` marker could not be verified.
+
+## 3. Current Python behaviour
+| Concern | Location | Behaviour |
+|---|---|---|
+| Startup | `nitrostack/core/app.py:1958-1966` | `McpApplication.start()` calls `OAuthService.start_discovery_server()` only when an `OAuthService` is registered in the container. |
+| Bind | `nitrostack/auth/oauth.py:259-274` | A daemon thread builds `HTTPServer(("localhost", port), DiscoveryHandler)` once. No probing and no retry. |
+| Port setting | `nitrostack/auth/oauth.py:261` | `int(os.environ.get("OAUTH_DISCOVERY_PORT", self.discovery_port))`: the **environment variable wins** over the `for_root(discovery_port=...)` value. `oauth_module.py` contains no port logic. |
+| Failure | `nitrostack/auth/oauth.py:275-277` | Any exception is written to stderr and swallowed. The thread ends, `_server` stays `None`, and the app keeps running with no discovery server. |
+| Reporting | `nitrostack/auth/oauth.py:264-273` | Writes `[NITROSTACK_OAUTH]{port, resource_uri, authorization_servers}[/NITROSTACK_OAUTH]` to stderr. The TypeScript marker carries more fields: `type`, `scopesSupported` and `wellKnownEndpoints`. |
+| CLI ports | `nitrostack/cli/main.py` `_resolve_runtime_ports`, `_normalize_port` | Resolve the MCP and widget ports (`--port`, `--widget`, env, defaults 3000/3001). Unrelated to OAuth discovery; no retry. |
+
+### Probe: preferred port already in use
+`scripts/probe_discovery_port.py` reserves a port, then starts the Python discovery server on it.
+Output on Windows (Python 3.12):
+busy port: 58380
+Failed to start OAuth Discovery Server on port 58380: [WinError 10013] An attempt was made to access a socket in a way forbidden by its access permissions
+server object: None
+bound to: None
+GET failed: TimeoutError timed out
+
+The server does not start, no port is reported, and the application is not told.
+Note: Windows returned `WinError 10013` rather than the usual address-in-use error,
+which is how it reports binding to a port held by another socket here.
+
+## 4. Comparison
+| Capability | TypeScript | Python | Gap? |
+|---|---|---|---|
+| Separate discovery server | yes, stdio mode and as fallback | yes, always a background thread when OAuth is registered | no |
+| Preferred port | option, default 3005, env `OAUTH_DISCOVERY_PORT` | env or `discovery_port` | no |
+| Retry on busy port | `autoRetry`, `maxRetries` (50 in OAuthModule) | none | **yes** |
+| Actual port available to code | `getPort()` and `OAuthModule.discoveryInfo` | no | yes |
+| Port reported to the host tool | stderr marker with port and well-known URLs | stderr marker with port only | partial |
+| Behaviour on bind failure | start promise rejects | logged and swallowed; no server | yes |
+| Only started when OAuth is configured | yes | yes | no |
+
+## 5. Conclusion
+**Open an implementation issue; do not close this one.** The two servers match in
+purpose, endpoints and stderr marker. They differ in port conflicts: TypeScript tries
+up to 50 ports and reports the one it used, while Python makes one attempt and silently
+runs without discovery when the port is taken, as the probe shows. A client that reads
+the marker will then never receive a port.
+
+Proposed scope for the follow-up (link here once opened):
+- Retry on a busy port, controlled by `OAUTH_DISCOVERY_AUTO_RETRY` and a max-retries
+  limit, with the same defaults as TypeScript (on, 50).
+- Store the actual port on `OAuthService` and put it in the stderr marker.
+- Surface bind failures instead of swallowing them.
+- Tests: busy port with retry, retries exhausted, port reported.
+
+Out of scope: matching the TypeScript marker's extra fields, until it is known
+whether NitroStudio consumes them.
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diff --git a/scripts/probe_discovery_port.py b/scripts/probe_discovery_port.py
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index 0000000..d538740
--- /dev/null
+++ b/scripts/probe_discovery_port.py
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+"""Does the Python OAuth discovery server survive a busy preferred port?"""
+import os
+import socket
+import time
+import urllib.request
+
+from nitrostack.auth.oauth import OAuthModule, OAuthService
+from nitrostack.core.di import DIContainer
+
+
+def free_port() -> int:
+    with socket.socket() as s:
+        s.bind(("127.0.0.1", 0))
+        return s.getsockname()[1]
+
+
+port = free_port()
+os.environ.pop("OAUTH_DISCOVERY_PORT", None)  # test discovery_port alone
+
+blockers = []
+for host in ("127.0.0.1", "0.0.0.0"):
+    b = socket.socket()
+    try:
+        b.bind((host, port))
+        b.listen(1)
+        blockers.append(b)
+    except OSError as exc:
+        print(f"blocker could not bind {host}:{port}: {exc}")
+        b.close()
+print("busy port:", port)
+
+DIContainer.reset()
+OAuthModule.for_root(
+    resource_uri="https://api.example.com",
+    authorization_servers=["https://idp.example.com"],
+    scopes_supported=["read"],
+    discovery_port=port,
+)
+service = DIContainer.get_instance().resolve(OAuthService)
+try:
+    service.start_discovery_server()
+    time.sleep(1.0)  # in case it binds in a background thread
+    server = getattr(service, "_server", None)
+    print("server object:", server)
+    print("bound to:", getattr(server, "server_address", None))
+    try:
+        url = f"http://127.0.0.1:{port}/.well-known/oauth-protected-resource"
+        with urllib.request.urlopen(url, timeout=2) as resp:
+            print("GET", url, "->", resp.status)
+    except Exception as exc:
+        print("GET failed:", type(exc).__name__, exc)
+except OSError as exc:
+    print("FAILED on busy port:", type(exc).__name__, exc)
+finally:
+    try:
+        service.stop_discovery_server()
+    except Exception as exc:
+        print("stop skipped:", type(exc).__name__, exc)
+    for b in blockers:
+        b.close()
+    DIContainer.reset()
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