diff --git a/apps/server/src/provider/Layers/OpenCodeAdapter.test.ts b/apps/server/src/provider/Layers/OpenCodeAdapter.test.ts
index baded8094ba65bdc9ca68eb9e5e30b5c2a27c013..40d034089ae95f23e89aee92bcc045f5c5d7cbbd 100644
--- a/apps/server/src/provider/Layers/OpenCodeAdapter.test.ts
+++ b/apps/server/src/provider/Layers/OpenCodeAdapter.test.ts
@@ -2,6 +2,7 @@ import * as NodeAssert from "node:assert/strict";
 import * as NodeServices from "@effect/platform-node/NodeServices";
 import { it } from "@effect/vitest";
 import * as Cause from "effect/Cause";
+import * as Clock from "effect/Clock";
 import * as Context from "effect/Context";
 import * as Crypto from "effect/Crypto";
 import * as Deferred from "effect/Deferred";
@@ -781,6 +782,56 @@ it.layer(OpenCodeAdapterTestLayer)("OpenCodeAdapterLive", (it) => {
     }),
   );
 
+  it.effect(
+    "stopSession completes after sendTurn is interrupted before the prompt is submitted",
+    () =>
+      Effect.gen(function* () {
+        const adapter = yield* OpenCodeAdapter;
+        const threadId = asThreadId("thread-opencode-interrupted-before-submit");
+        runtimeMock.state.createdSessionIds.push("ses_interrupted_before_submit");
+        yield* adapter.startSession({
+          provider: ProviderDriverKind.make("opencode"),
+          threadId,
+          runtimeMode: "full-access",
+        });
+
+        const baseClock = yield* Clock.clockWith(Effect.succeed);
+        const reached = yield* Deferred.make<void>();
+        const release = yield* Deferred.make<void>();
+        let calls = 0;
+        const gatedClock: Clock.Clock = {
+          ...baseClock,
+          currentTimeMillisUnsafe: () => baseClock.currentTimeMillisUnsafe(),
+          currentTimeMillis: Effect.suspend(() => {
+            calls += 1;
+            return calls === 2
+              ? Deferred.succeed(reached, undefined).pipe(
+                  Effect.andThen(Deferred.await(release)),
+                  Effect.andThen(baseClock.currentTimeMillis),
+                )
+              : baseClock.currentTimeMillis;
+          }),
+        };
+
+        const sendFiber = yield* adapter
+          .sendTurn({
+            threadId,
+            input: "This prompt must not be submitted",
+            modelSelection: createModelSelection(
+              ProviderInstanceId.make("opencode"),
+              "opencode/kimi-k3",
+            ),
+          })
+          .pipe(Effect.provideService(Clock.Clock, gatedClock), Effect.exit, Effect.forkChild);
+        yield* Deferred.await(reached);
+        yield* Fiber.interrupt(sendFiber);
+
+        const stopExit = yield* adapter.stopSession(threadId).pipe(Effect.exit);
+        NodeAssert.equal(Exit.isSuccess(stopExit), true);
+        NodeAssert.equal(yield* adapter.hasSession(threadId), false);
+      }),
+  );
+
   it.effect("aborts a held teardown request before closing the session scope", () =>
     Effect.gen(function* () {
       const adapter = yield* OpenCodeAdapter;
diff --git a/apps/server/src/provider/Layers/OpenCodeAdapter.ts b/apps/server/src/provider/Layers/OpenCodeAdapter.ts
index 04535edbd3afb22d1e54a66e5daf75a692dd6b34..34ebd1b544fb46dc3da13530bfd55da6e3f2785c 100644
--- a/apps/server/src/provider/Layers/OpenCodeAdapter.ts
+++ b/apps/server/src/provider/Layers/OpenCodeAdapter.ts
@@ -3531,7 +3531,18 @@ export function makeOpenCodeAdapter(
               ? { resumeCursor: context.session.resumeCursor }
               : {}),
           };
-        }),
+        }).pipe(
+          // stopSession waits on submissionSettled; an interrupted sendTurn
+          // must not leave it pending.
+          Effect.ensuring(
+            Effect.suspend(() => {
+              const admission = context.promptAdmission;
+              return admission
+                ? Deferred.succeed(admission.submissionSettled, undefined).pipe(Effect.ignore)
+                : Effect.void;
+            }),
+          ),
+        ),
       );
     });