diff --git a/docs/plans/2026-07-22-gamewindow-slice-8-checkpoint-i-ordered-composition.md b/docs/plans/2026-07-22-gamewindow-slice-8-checkpoint-i-ordered-composition.md
index 5a37c4e4..9da5b2ff 100644
--- a/docs/plans/2026-07-22-gamewindow-slice-8-checkpoint-i-ordered-composition.md
+++ b/docs/plans/2026-07-22-gamewindow-slice-8-checkpoint-i-ordered-composition.md
@@ -290,7 +290,9 @@ ledger only after the complete pipeline is live.
   spawn-claim DAT range memo has a focused owner. `GameWindow.cs` is 2,479 raw
   lines. App Release passes 3,420 tests / 3 skips; the complete Release suite
   passes 7,792 tests / 5 skips with the same 17 warnings tracked by #228. I.8
-  frame-root publication and terminal session start is the active cut.
+  frame-root publication and terminal session start is the active cut. Its
+  detailed session-binding, atomic-root, and terminal-start plan is
+  [`2026-07-22-gamewindow-slice-8-checkpoint-i8-frame-roots-session-start.md`](2026-07-22-gamewindow-slice-8-checkpoint-i8-frame-roots-session-start.md).
   Checkpoint I remains active until I.9 closes the complete nine-phase pipeline.
 
 ## 6. Automated acceptance
diff --git a/docs/plans/2026-07-22-gamewindow-slice-8-checkpoint-i8-frame-roots-session-start.md b/docs/plans/2026-07-22-gamewindow-slice-8-checkpoint-i8-frame-roots-session-start.md
new file mode 100644
index 00000000..b7aebf8d
--- /dev/null
+++ b/docs/plans/2026-07-22-gamewindow-slice-8-checkpoint-i8-frame-roots-session-start.md
@@ -0,0 +1,225 @@
+# GameWindow Slice 8 — Checkpoint I.8 Frame Roots and Session Start
+
+**Status:** Active
+
+**Parent:** `2026-07-22-gamewindow-slice-8-checkpoint-i-ordered-composition.md`
+
+**Scope:** Complete Phase 7's session-facing owners, then implement ordered
+composition Phases 8 and 9.
+
+## 1. Outcome
+
+Finish the production startup graph without changing accepted input, update,
+render, network, portal, or UI behavior:
+
+1. complete Phase 7 before any frame root is visible;
+2. construct update and render roots locally and publish the pair atomically;
+3. start the optional live session as the absolute final startup operation.
+
+The current ordering defect is structural: `GameWindow.OnLoad` publishes the
+frame pair before the combat/diagnostic command targets and sole gameplay input
+subscriber are attached. I.8 moves those pre-frame owners into the Phase-7
+result, so native callbacks can never observe an incomplete input/command
+graph.
+
+This is an ownership move. Retail algorithms and wire behavior remain
+unchanged, so no divergence-register row is added.
+
+## 2. I.8a — complete session/player composition
+
+### 2.1 Focused session runtime factory
+
+Add `LiveSessionRuntimeFactory` under `AcDream.App/Net`. It owns the existing
+domain-specific construction of:
+
+- `LiveSessionHostBindings`;
+- reset manifest bindings;
+- selection and entered-world callbacks;
+- event and command routers;
+- inventory, character, and social session bindings.
+
+The factory receives focused owners and state slots, never `GameWindow` and
+never a callback to a substantial window method. Move the existing reset and
+router bodies verbatim. Preserve the exact reset order and the existing
+retail citations around player-module identity/shortcut/component cleanup.
+
+Add `DesiredComponentSnapshotState` beside `ShortcutSnapshotState` so session
+routers mutate one focused state owner. `GameWindow.DesiredComponents` remains
+an ABI-compatible read-only projection over that owner. Existing
+`LocalPlayerIdentityState`, `LocalPlayerControllerSlot`, and
+`ShortcutSnapshotState` remain canonical; no mirrored values are introduced.
+
+### 2.2 Commands and sole gameplay subscriber
+
+At the tail of `SessionPlayerCompositionPhase`, after player mode and teleport
+exist but before result publication:
+
+1. create `LiveSessionHost` through the focused factory;
+2. create and bind `LiveCombatModeCommandController`;
+3. create and bind `RuntimeDiagnosticCommandController`;
+4. create `GameplayInputCommandController` and priority targets;
+5. create and attach the sole `GameplayInputActionRouter`.
+
+Add exact-owner `BindOwned` tokens to the combat and diagnostic command slots.
+The existing gameplay router already owns both subscriptions transactionally;
+Phase 7 scope-owns it immediately after construction and before `Attach`.
+
+Extend `SessionPlayerResult` and its publication seam with the exact
+`LiveSessionHost`, command owners, and optional gameplay router. Publication
+rejects replacement before changing any field. Failure before publication
+disposes the router, detaches command targets, and rolls back the existing
+Phase-7 suffix in reverse order.
+
+## 3. I.8b — atomic frame-root composition
+
+Add `FrameRootCompositionPhase` implementing the existing
+`IFrameRootCompositionPhase` contract. Its dependencies are focused App owners;
+prior phase results supply all resources created during startup.
+
+Preserve the exact current construction order:
+
+1. teleport/login/GL-state and render-live preparation;
+2. render resource begin/clear/live phases;
+3. weather, sky-PES, world environment, camera, visibility, settings preview,
+   root, animated-object, and building sources;
+4. terrain, PView, scene-pass, and world-scene diagnostics;
+5. optional lifecycle automation;
+6. retained/devtools/private presentation;
+7. render orchestrator;
+8. live-frame coordinator, camera frame, and update orchestrator;
+9. atomic update/render pair publication as the final Phase-8 action.
+
+Add `GameFrameGraphSlot.PublishOwned`. Its lease withdraws only the exact pair
+it published, is idempotent, and cannot withdraw a later replacement. Scope-own
+the lease immediately. A failure before publication leaves the slot empty; a
+failure after publication withdraws the exact pair unless result publication
+has transferred lifetime to the window shutdown owner.
+
+### 3.1 Automation and resource snapshots
+
+Add `WorldLifecycleResourceSnapshotSource` now rather than retaining
+`CaptureWorldLifecycleResourceSnapshot` on the window. It samples the same
+canonical world, live-runtime, effect, particle, light, script, mesh, texture,
+GPU-memory, managed-memory, render-diagnostic, and frame-profiler owners.
+
+This advances the owner-extraction portion of Checkpoint K; K still changes
+checkpoint timing, acknowledgement barriers, JSONL validation, and soak
+comparison. No checkpoint semantics change in I.8.
+
+`FrameRootRuntimeBindings` owns the optional automation late binding and any
+other Phase-8 external edge. It uses reverse, retryable, no-replay cleanup.
+Shutdown withdraws the frame graph first, then detaches these frame-owned
+bindings before borrowed session/presentation owners retire.
+
+### 3.2 Publication
+
+`FrameRootResult` contains:
+
+- exact update and render roots;
+- optional lifecycle automation owner;
+- Phase-8 runtime bindings;
+- the `LiveSessionHost` borrowed from Phase 7 for terminal start.
+
+`IGameWindowFrameRootPublication` stores only owners needed by steady-state or
+shutdown. Replacement is rejected atomically.
+
+## 4. I.8c — terminal start and window cutover
+
+Add `SessionStartCompositionPhase` implementing
+`ISessionStartCompositionPhase<FrameRootResult>`. It invokes only
+`LiveSessionHost.Start(RuntimeOptions)` and preserves the existing diagnostics
+for missing credentials and failed startup.
+
+`GameWindow.OnLoad` ends with:
+
+```text
+Phase 7 Compose
+Phase 8 Compose and atomic pair publication
+Phase 9 Start
+return
+```
+
+There is no callback attachment, binding, publication, diagnostics setup, or
+other work after Phase 9. Delete the old inline frame construction, session
+factory/reset/router methods, snapshot method, and terminal status switch.
+
+The existing typed nine-phase `GameWindowCompositionPipeline` remains the
+executable order/failure oracle. Production `OnLoad` uses the same phase
+interfaces and result chain explicitly because later-phase dependency records
+are assembled from earlier concrete results; it must not introduce a retained
+mega-context, service locator, or delegate façade around `GameWindow`.
+
+## 5. Ownership and rollback order
+
+Before frame publication, Phase-7 rollback is:
+
+1. gameplay router detach;
+2. diagnostic and combat command unbind;
+3. remaining session/player bindings;
+4. teleport, live session, and streamer teardown.
+
+After frame publication, Phase-8 rollback is:
+
+1. exact frame-pair withdrawal;
+2. automation/other frame binding detach;
+3. no disposal of resources borrowed from earlier successful phases.
+
+Normal shutdown retains the frozen barrier order:
+
+1. logical input/command quiescence;
+2. live-session convergence;
+3. physical input callback detach;
+4. frame-pair withdrawal;
+5. frame then session/player late-binding detach;
+6. remaining session, live-entity, effect, render, content, GL, and native
+   owners.
+
+## 6. Automated gates
+
+### Session/runtime
+
+- exact live-session host construction and reset trace;
+- no `GameWindow` field or delegate capture in the focused factory;
+- exact-owner combat/diagnostic bind, competing-owner rejection, idempotent
+  release, and rebind;
+- gameplay router attaches before frame publication and rolls back from either
+  partial subscription;
+- failed Phase-7 publication leaves no command/input/session target behind.
+
+### Frame roots
+
+- exact render/update leaf construction order;
+- frame slot is empty at every pre-publication fault;
+- exact pair publishes once and both native callbacks see the same generation;
+- rollback withdraws only the published pair and never a later replacement;
+- automation disabled path acquires nothing;
+- automation enabled path binds once, detaches exactly, and samples the same
+  resource values as the former window method;
+- frame result publication rejects replacement atomically.
+
+### Terminal start and structure
+
+- terminal start runs only after frame publication and every input/command
+  attachment;
+- missing credentials and failed starts preserve current diagnostics;
+- no operation follows `Start`;
+- `GameWindow` contains no live-session binding factory, frame-root
+  construction body, resource-snapshot algorithm, or direct frame-pair
+  publication;
+- no backend dependency enters Core and panels remain on UI abstractions;
+- App Release tests, clean solution Release build, and complete Release suite
+  pass;
+- behavior/order, architecture/ownership, and adversarial failure reviews are
+  clean.
+
+## 7. Commit sequence
+
+1. `docs(architecture): plan frame roots and terminal session start`
+2. `refactor(app): complete session startup composition`
+3. `refactor(app): compose atomic frame roots`
+4. `refactor(app): make session start terminal`
+
+Each implementation commit is independently buildable and preserves the
+protected pre-existing `TransitionTypes.cs`, `.test-out/`, and `logs/` changes.
+I.9 performs the complete Checkpoint-I corrected-diff review and documentation
+closeout after these cuts land.