# Phase C+9 — XamContentCreateEnumerator investigation

## Phase A oracle (predecessor C+8 baseline)

`canary tid=6 → ours tid=1` main chain, `tid_event_idx = 102197`:

```
canary: kernel.return XamContentCreateEnumerator return_value=1317  status=0x00000525  side_effects=[]
ours:   kernel.return XamContentCreateEnumerator return_value=0     status=0x00000000  side_effects=[]
```

`args` and `args_resolved` are empty per the current Phase A emitter
scope (kernel.call args are not yet wired for dword-only signatures).

## Framing verification (reading-error #28 — canary source supersedes
NT-doc semantics or value-name guesses)

**The plan's framing was wrong on the constant identity**:
`0x525 = 1317` is `X_ERROR_NO_SUCH_USER`, NOT `X_ERROR_NO_CONTENT`
(`xbox.h:113`):

```cpp
#define X_ERROR_NO_SUCH_USER X_RESULT_FROM_WIN32(0x00000525L)
```

`X_ERROR_NO_CONTENT` is not even defined in canary's xbox.h. Always
verify constants against canary source, never the plan's inline
annotations.

## Canary body (`xenia-canary/src/xenia/kernel/xam/xam_content.cc:129-220`)

```cpp
dword_result_t XamContentCreateEnumerator_entry(
    dword_t user_index, dword_t device_id, dword_t content_type,
    dword_t content_flags, dword_t items_per_enumerate,
    lpdword_t buffer_size_ptr, lpdword_t handle_out) {
  assert_not_null(handle_out);

  auto device_info = device_id == 0 ? nullptr : GetDummyDeviceInfo(device_id);
  if ((device_id && device_info == nullptr) || !handle_out) {
    if (buffer_size_ptr) *buffer_size_ptr = 0;
    return X_E_INVALIDARG;        // 0x80070057
  }

  if (buffer_size_ptr) {
    *buffer_size_ptr = sizeof(XCONTENT_DATA) * items_per_enumerate;
  }                                // sizeof(XCONTENT_DATA) = 0x134

  uint64_t xuid = 0;
  if (user_index != XUserIndexNone /* 0xFE */) {
    const auto& user = kernel_state()->xam_state()->GetUserProfile(user_index);
    if (!user) return X_ERROR_NO_SUCH_USER;    // 0x525  ← THIS BRANCH
    xuid = user->xuid();
  }

  // ... enumerator init, ListContent over HDD/ODD, fill items ...
  *handle_out = e->handle();
  return X_ERROR_SUCCESS;          // 0
}
```

Only ONE control-flow path returns `0x525`:

1. `user_index != 0xFE` (i.e. a specific signed-in user is being queried)
2. `XamState::GetUserProfile(user_index)` returns `nullptr` — i.e. no
   profile is installed at that slot.

Under canary's default `--mute=true` config (no `--profile_slot_*`
flags), `ProfileManager` has zero profiles, so `GetProfile(N)` returns
`nullptr` for every `N`.

## Side-effects check (rule out classification C)

Canary's `kernel.return` payload has `side_effects=[]`. Combined with
the body shape: the `*handle_out` write and the `*buffer_size_ptr`
write happen **inside the function** but are not handle-creation
side effects (no Phase A `handle.create` emit because no `XEnumerator`
was minted). The empty `side_effects` confirms canary reached the
`X_ERROR_NO_SUCH_USER` early-return at line 153-155, **before** the
`new ContentEnumerator(...)` allocation at line 160-161. So:

* No handle-table mutation to mirror.
* The `*buffer_size_ptr` write happens BEFORE the user check (line
  145-147), so it does fire on the 0x525 path. Ours must mirror.

## Classification

**Class A — Unconditional (under ours's state model).**

Ours has no profile manager; all `user_index < 4` queries return
"no such user". This is effectively unconditional from Sylpheed's
perspective. Mirror canary's early-return.

**NOT class B** (state-dependent over real disk content) — we don't
reach the `ListContent()` enumeration path, so we don't need a
filesystem scan. No escalation.

**NOT class C** (side-effect mismatch) — both engines have empty
`side_effects` for this idx (above).

**NOT class D** (Phase A coverage asymmetry) — both engines emit the
same 3-event sequence (import.call, kernel.call, kernel.return).

## Ours pre-fix state

`crates/xenia-kernel/src/xam.rs:59`:
```rust
state.register_export(Xam, 0x025C, "XamContentCreateEnumerator", stub_success);
```

`stub_success` sets `r3 = 0`. Hence `return_value=0`, `status=0x00000000`,
no buffer_size_ptr write, no handle_out write.

## Fix shape

Replace the `stub_success` registration with a dedicated handler that:

1. Reads r3..r9 (user_index, device_id, content_type, content_flags,
   items_per_enumerate, buffer_size_ptr, handle_out).
2. Returns `X_E_INVALIDARG` (0x80070057) when device_id is unknown
   (>2; canary's GetDummyDeviceInfo accepts HDD=1, ODD=2) or
   handle_out is NULL; writes `*buffer_size_ptr = 0` in that arm.
3. Otherwise writes `*buffer_size_ptr = 0x134 * items_per_enumerate`
   (the sizeof(XCONTENT_DATA) computation).
4. If `user_index != 0xFE`: return `X_ERROR_NO_SUCH_USER` (0x525) —
   ours has no profile manager.
5. Otherwise (user_index == 0xFE, XUserIndexNone): proceed to a
   stubbed enumerator-success path — write `*handle_out = 0` and
   return 0. Defensive; not exercised by current Phase A.

LOC: ~85 body + ~125 tests = ~210 additive in xam.rs only.

## Internal-consistency caveat (deferred)

Ours's `xam_user_get_signin_state` (xam.rs:380-384) returns 1 for
`user_index == 0`, claiming user 0 is signed in. This contradicts the
"no profile manager" model used by the C+9 fix. The conflict surfaces
at Phase A idx 107996 (canary returns 0 for `XamUserGetSigninState`)
and will be a separate fix in a future session. Single-fix discipline:
do not widen scope here.

## Internal-consistency caveat #2 (cosmetic)

The doc comment on `xam_user_get_signin_state` says "user0 signed in
locally" but canary returns 0 here. That's evidence of an older fix
that needs reconciliation. Out of scope for C+9.