Merge nucleic/olive-jade-civet-rznt into dev

spikes/README.md

@@ -87,12 +87,16 @@ name**. That second construction is the whole point, and it is the last open que
 on: the compat SDK exposes a `Session` *constructor* and no attach, so does constructing over an
 existing name re-adopt it, or refuse?
 
-- **Refused** (`WSLC_E_SESSION_RESERVED`, `0x80040607`) — D13's premise is confirmed, and session
-  reattach genuinely requires `IWSLCSessionManager::OpenSessionByName` on the internal interface.
-- **Constructed** — which is what 2.9.4 actually does. That alone proves nothing (construction may
-  be lazy), so the probe then runs an **identity test**: terminate the FIRST session and read from
-  the SECOND. A read that worked before and fails after is one underlying session answering both
-  handles; a read that keeps working means two independent VMs were running.
+**Answered on 2.9.4: it cannot.** The constructor is lazy and always succeeds — judging by it is
+what made the first reading of this probe wrong. `Start()` is where the service is consulted, and
+a second `Start()` on a running name fails with `ERROR_ALREADY_EXISTS` (0x800700B7). Note it is
+*not* `WSLC_E_SESSION_RESERVED`, which exists in `wslc.idl` but evidently means something
+narrower — don't key on it.
+
+So the probe judges on `Start()`. If a future version lets the second `Start()` through, it then
+runs an **identity test**: terminate the FIRST session and read from the SECOND. A read that
+worked before and fails after is one underlying session answering both handles; a read that keeps
+working means two independent VMs.
 
 The identity test deliberately uses only the compat SDK. The obvious check would be
 `wslc session ls` — but **`wslc.exe` is not on PATH by default**, so a spike that depends on it

spikes/WslcApiDump/Program.cs

@@ -15,10 +15,11 @@ namespace WslcApiDump;
 ///
 /// It never mutates anything unless asked: the default run only reads type metadata. `--probe`
 /// additionally calls the two safe statics (`GetVersion`, `GetMissingComponents`). `--session`
-/// goes further and creates a real session, then creates a SECOND one with the same name — which
-/// is the open question D13 turns on: whether the compat SDK's constructor can re-adopt a session
-/// by name, or refuses with `WSLC_E_SESSION_RESERVED` and leaves reattach to the internal COM
-/// interface (docs/WINDOWS_PORT.md §13.1).
+/// goes further and creates a real session, then a SECOND one with the same name, to settle
+/// whether the compat SDK can re-adopt a running session. Answered on 2.9.4: it cannot. The
+/// constructor is lazy and always succeeds; `Start()` is where the service is consulted, and it
+/// refuses with `ERROR_ALREADY_EXISTS`. So reattach needs the internal COM interface, which is
+/// what D13 assumes (docs/WINDOWS_PORT.md §13.1).
 /// </summary>
 internal static class Program
 {
@@ -402,19 +403,39 @@ internal static class Program
         }
         else
         {
-            // Starting it is one more signal: re-adopting a RUNNING session should be a no-op,
-            // whereas a genuinely separate session would be booting a second VM here.
-            if (start is not null)
+            // The constructor is LAZY — it only captures settings, so its success says nothing.
+            // `Start()` is where the service is actually asked for the session, and therefore
+            // where exclusivity is enforced. Judge on that.
+            var secondStarted = false;
+            string? startFailure = null;
+            if (start is null)
             {
-                try { start.Invoke(second, null); Console.WriteLine("  second Start() ok"); }
-                catch (TargetInvocationException e)
+                Console.WriteLine("  (no Session.Start() — cannot judge)");
+            }
+            else
             {
-                    Console.WriteLine($"  second Start() threw {Describe(e.InnerException)}");
+                try { start.Invoke(second, null); secondStarted = true; }
+                catch (TargetInvocationException e) { startFailure = Describe(e.InnerException); }
             }
-            }
-            Console.WriteLine("  → CONSTRUCTED — the constructor did NOT refuse.");
+
+            if (secondStarted)
+            {
+                Console.WriteLine("  second Start() ok — it did NOT refuse, so it may have re-adopted");
                 IdentityTest(sessionType, first, second);
             }
+            else if (startFailure is not null)
+            {
+                Console.WriteLine($"  second Start() threw {startFailure}");
+                Console.WriteLine();
+                Console.WriteLine("  → REFUSED at Start(). The constructor succeeding meant nothing:");
+                Console.WriteLine("    it is lazy, and the service is only consulted by Start().");
+                Console.WriteLine("    So the compat SDK CANNOT re-adopt a running session, and D13");
+                Console.WriteLine("    holds — §2.3 reattach needs IWSLCSessionManager::OpenSessionByName");
+                Console.WriteLine("    (or EnterSession) on the internal COM interface.");
+                Console.WriteLine("    Note the code is ERROR_ALREADY_EXISTS, not WSLC_E_SESSION_RESERVED;");
+                Console.WriteLine("    the reserved code evidently means something narrower.");
+            }
+        }
         Console.WriteLine();
         if (keep)
         {
@@ -447,7 +468,8 @@ internal static class Program
         Console.WriteLine("  identity test: terminate the FIRST, then read from the SECOND");
         if (!Reads(getImages, second, out var before))
         {
-            Console.WriteLine($"    inconclusive — the second session already fails to read: {before}");
+            // Only reachable if Start() reported success but the session is unusable anyway.
+            Console.WriteLine($"    inconclusive — the second session reads fail already: {before}");
             return;
         }
         Console.WriteLine("    second reads ok before termination");
@@ -564,6 +586,9 @@ internal static class Program
         0x80070032 => "ERROR_NOT_SUPPORTED — the installed WSL does not implement this call "
             + "(almost always: WSL is older than the SDK)",
         0x80070005 => "E_ACCESSDENIED",
+        0x800700B7 => "ERROR_ALREADY_EXISTS — a session of that name is already running",
+        0x8000000E => "E_ILLEGAL_METHOD_CALL — the object is not in a state to serve this call "
+            + "(e.g. Session.Start() was never called, or failed)",
         0x80040601 => "WSLC_E_IMAGE_NOT_FOUND",
         0x80040603 => "WSLC_E_CONTAINER_NOT_FOUND",
         0x80040605 => "WSLC_E_CONTAINER_NOT_RUNNING",