diff --git a/investigation/windows-preview-devbox-qualification-plan.md b/investigation/windows-preview-devbox-qualification-plan.md
index a4e53ff4..c156ee25 100644
--- a/investigation/windows-preview-devbox-qualification-plan.md
+++ b/investigation/windows-preview-devbox-qualification-plan.md
@@ -320,11 +320,47 @@ the backend's normal flow outside chat and evidence.
 5. Record backend conversation ID and zmx session name; they must be distinct.
 6. Verify readable current pixels, expected markers, cursor/input, wrapping,
    resize, tab switching, stop, and reopen.
-7. Verify stop affects only the intended loop.
+7. Verify stop affects only the intended loop, using the Stop contract below.
 8. Stop immediately at two turns or the USD 5 ceiling.
 
 Do not record credentials, tokens, private prompts, or unrelated output.
 
+### Stop contract
+
+Stop is the reversible verb. It does not promise to end the loop's session.
+Before pressing Stop, record `zmx list` (names only) and create at least two
+owned sentinel sessions: one unprefixed, and one decoy named
+`graphcode-<another UUID>`. Then press **Stop loop** with native input.
+
+Stop passes only if all of these hold:
+
+- the intended loop's state becomes `stopped` and its Stop control disappears;
+- no other loop changes state;
+- the loop's memory log (`memory\<project>\<loop id>\LOG.txt` under the support
+  directory) records exactly one new stop entry, which takes exactly one of
+  the two paths below, and that path matches what you observe;
+- every other zmx session, including both sentinels, keeps the same PID, and no
+  sentinel receives input;
+- the shell and the production daemon stay responsive.
+
+The two daemon paths are:
+
+| Memory-log entry | Expected observation |
+| --- | --- |
+| `its session was asked to stop looping` | `graphcode-<loop UUID>` is still listed with the same PID. Its terminal shows the daemon's `[graphcode] Stop requested from the graph…` request, which tells the agent to stay in the session. The agent process may stay alive. |
+| `its session could not be reached, so it was killed` | `graphcode-<loop UUID>` is absent from `zmx list` within 15 seconds, and its agent process has exited. |
+
+Classify `TerminalSessionOwnership` and stop if:
+
+- the log claims a kill but the session survives (the beta9 Dev Box result);
+- the log claims a request was delivered but the request appears in no session,
+  or in a different one;
+- a different session dies;
+- the loop does not reach `stopped`.
+
+Do not require a reachable session to end, and do not use `zmx kill` or Restart
+to make Stop pass.
+
 ## Phase D8 — native reachability and input
 
 Run separate fixed-geometry profiles for 100% and 150%.
diff --git a/investigation/windows-preview-release-plan.md b/investigation/windows-preview-release-plan.md
index 04521e2b..ad16ae2f 100644
--- a/investigation/windows-preview-release-plan.md
+++ b/investigation/windows-preview-release-plan.md
@@ -71,7 +71,11 @@ The handoff `GraphCode-DevBox-Handoff-0.1.78-windows.beta9` has `hashes.sha256`
 SHA-256 `bd57e1e11c02fb3bc4644c8faf91137bf4e9272c2c01f8dbd0f629af9a108dce`;
 all **8/8** entries verified. Its Dev Box prompt adds a terminal readability and
 session-ownership gate after the Core-visibility gate, before any backend
-credits are spent.
+credits are spent. That prompt's requirement that Stop end the loop's session
+is superseded by the Stop contract in the
+[Dev Box plan](windows-preview-devbox-qualification-plan.md#stop-contract): a
+reachable session receives the daemon's stop request and stays alive, and only
+an unreachable session is killed.
 
 ### Historical beta8 candidate