diff --git a/apps/server/src/orchestration-v2/Adapters/OpenCode2AdapterV2.test.ts b/apps/server/src/orchestration-v2/Adapters/OpenCode2AdapterV2.test.ts
index b4c319e8e9a96..ecb05a5a02a15 100644
--- a/apps/server/src/orchestration-v2/Adapters/OpenCode2AdapterV2.test.ts
+++ b/apps/server/src/orchestration-v2/Adapters/OpenCode2AdapterV2.test.ts
@@ -3288,6 +3288,55 @@ it.layer(McpProviderSessions.layer)("OpenCode2 adapter", (it) => {
     }).pipe(Effect.scoped),
   );
 
+  it.effect("rejects unreadable rollback history before cutting the native session", () =>
+    Effect.gen(function* () {
+      const { runtime, thread } = yield* resumed([
+        out("message.list", { sessionID: SESSION, limit: "100", type: undefined }),
+        reply("message.list", {
+          data: [
+            { id: "msg_kept", time: { created: 1 }, text: "first", type: "user" },
+            {
+              id: "msg_compaction",
+              time: { created: 2 },
+              type: "compaction",
+              status: "completed",
+              reason: "auto",
+              summary: "First turn summary",
+            },
+            { id: "msg_dropped", time: { created: 3 }, text: "second", type: "user" },
+          ],
+          cursor: {},
+        }),
+      ]);
+      const now = yield* DateTime.now;
+      const turns = ["msg_kept", "msg_dropped"].map((nativeId, index) => ({
+        id: ProviderTurnId.make(`provider-turn:rollback-history:${index}`),
+        providerThreadId: thread.id,
+        nodeId: NodeId.make(`node:rollback-history:${index}`),
+        runAttemptId: RunAttemptId.make(`attempt:rollback-history:${index}`),
+        nativeTurnRef: { driver: OPENCODE_PROVIDER, nativeId, strength: "weak" as const },
+        ordinal: index + 1,
+        status: "completed" as const,
+        startedAt: now,
+        completedAt: now,
+      }));
+      const failure = yield* runtime
+        .rollbackThread({
+          providerThread: thread,
+          target: {
+            type: "provider_turn",
+            checkpointId: CheckpointId.make("checkpoint:rollback-history"),
+            appRunOrdinal: 1,
+            providerTurn: turns[0]!,
+          },
+          providerThreadTurns: turns,
+        })
+        .pipe(Effect.flip);
+      assert.equal(failure._tag, "ProviderAdapterRollbackThreadError");
+      assert.include(Cause.pretty(Cause.fail(failure)), '["recent"]');
+    }).pipe(Effect.scoped),
+  );
+
   it.effect("clears a staged revert whose commit failed, before the next prompt too", () =>
     Effect.gen(function* () {
       const kept = "msg_t3_turn_run-attempt:kept:1";
@@ -4075,8 +4124,22 @@ it.layer(McpProviderSessions.layer)("OpenCode2 adapter", (it) => {
     Effect.gen(function* () {
       const FORK = "ses_f1484db83ffeLGtrRCFimo1H0e";
       const { runtime, thread, first, second } = yield* continued([
-        out("message.list", "<any>"),
-        reply("message.list", continuedHistory),
+        out("message.list", { sessionID: SESSION, limit: "100", type: "user" }),
+        reply("message.list", { data: [continuedHistory.data[1]], cursor: {} }),
+        out("message.list", { sessionID: SESSION, limit: "100", type: "synthetic" }),
+        reply("message.list", {
+          data: [
+            { id: "msg_later_report", time: { created: 3 }, text: "later", type: "synthetic" },
+          ],
+          cursor: { next: "synthetic-page-2" },
+        }),
+        out("message.list", {
+          sessionID: SESSION,
+          limit: "100",
+          type: "synthetic",
+          cursor: "synthetic-page-2",
+        }),
+        reply("message.list", { data: [continuedHistory.data[0]], cursor: {} }),
         out("session.fork", { sessionID: SESSION, before: "msg_report" }),
         replyData("session.fork", sessionInfo({ id: FORK })),
         out("session.update", { sessionID: FORK, permissions: "<any>" }),
diff --git a/apps/server/src/orchestration-v2/testkit/fixtures/opencode2_fork/opencode_transcript.ndjson b/apps/server/src/orchestration-v2/testkit/fixtures/opencode2_fork/opencode_transcript.ndjson
index 57cbd14853460..a483f04813b31 100644
--- a/apps/server/src/orchestration-v2/testkit/fixtures/opencode2_fork/opencode_transcript.ndjson
+++ b/apps/server/src/orchestration-v2/testkit/fixtures/opencode2_fork/opencode_transcript.ndjson
@@ -41,10 +41,12 @@
 {"type": "emit_inbound", "label": "session.step.ended.2", "frame": {"type": "sdk.event", "event": {"id": "evt_0eb7b2461001qEeIO2dKdf1y1Y", "created": 1790657111137, "type": "session.step.ended", "location": {"directory": "<work>"}, "data": {"sessionID": "ses_f1484ea8affe5aTo8CcgbGIszj", "assistantMessageID": "msg_0eb7b1fb30011jHuDOQ5YiY6eH", "finish": "stop", "rawFinish": "stop", "cost": 0, "tokens": {"input": 16, "output": 3, "reasoning": 0, "cache": {"read": 9327, "write": 0}}, "snapshot": "99482b54df6361365fa0ed7363ccf07edaa7fc93", "files": []}, "durable": {"aggregateID": "ses_f1484ea8affe5aTo8CcgbGIszj", "seq": 20, "version": 1}}}}
 {"type": "emit_inbound", "label": "session.usage.updated.2", "frame": {"type": "sdk.event", "event": {"id": "evt_0eb7b2465001TtO12Ofsv2KZTq", "created": 1790657111141, "type": "session.usage.updated", "data": {"sessionID": "ses_f1484ea8affe5aTo8CcgbGIszj", "cost": 0, "tokens": {"input": 8759, "output": 4, "reasoning": 99, "cache": {"read": 9813, "write": 0}}}}}}
 {"type": "emit_inbound", "label": "session.execution.succeeded.2", "frame": {"type": "sdk.event", "event": {"id": "evt_0eb7b24660011TVz6Q64I8aAQ7", "created": 1790657111142, "type": "session.execution.succeeded", "data": {"sessionID": "ses_f1484ea8affe5aTo8CcgbGIszj"}, "durable": {"aggregateID": "ses_f1484ea8affe5aTo8CcgbGIszj", "seq": 21, "version": 1}}}}
-{"type": "expect_outbound", "label": "message.list", "frame": {"type": "message.list", "input": "<any>"}}
+{"type": "expect_outbound", "label": "message.list", "frame": {"type": "message.list", "input": {"sessionID": "ses_f1484ea8affe5aTo8CcgbGIszj", "limit": "100", "type": "user"}}}
 {"type": "emit_inbound", "label": "message.list.response", "frame": {"type": "sdk.response", "operation": "message.list", "data": {"data": [{"id": "msg_0eb7b1f9f001g95Bduh3bi8syS", "time": {"created": 1790657109932}, "text": "Reply exactly TWO.", "type": "user"}, {"id": "msg_0eb7b1597001e14VBV3nmQYdFS", "time": {"created": 1790657107378}, "text": "Reply exactly ONE.", "type": "user"}], "cursor": {"next": "cursor-after-first-page"}}}}
-{"type": "expect_outbound", "label": "message.list.2", "frame": {"type": "message.list", "input": "<any>"}}
+{"type": "expect_outbound", "label": "message.list.2", "frame": {"type": "message.list", "input": {"sessionID": "ses_f1484ea8affe5aTo8CcgbGIszj", "limit": "100", "type": "user", "cursor": "cursor-after-first-page"}}}
 {"type": "emit_inbound", "label": "message.list.response.2", "frame": {"type": "sdk.response", "operation": "message.list", "data": {"data": [], "cursor": {}}}}
+{"type": "expect_outbound", "label": "message.list.synthetic", "frame": {"type": "message.list", "input": {"sessionID": "ses_f1484ea8affe5aTo8CcgbGIszj", "limit": "100", "type": "synthetic"}}}
+{"type": "emit_inbound", "label": "message.list.synthetic.response", "frame": {"type": "sdk.response", "operation": "message.list", "data": {"data": [], "cursor": {}}}}
 {"type": "expect_outbound", "label": "session.fork", "frame": {"type": "session.fork", "input": {"sessionID": "ses_f1484ea8affe5aTo8CcgbGIszj", "before": "msg_0eb7b1f9f001g95Bduh3bi8syS"}}}
 {"type": "emit_inbound", "label": "session.fork.response", "frame": {"type": "sdk.response", "operation": "session.fork", "data": {"data": {"id": "ses_f1484db83ffeLGtrRCFimo1H0e", "fork": {"sessionID": "ses_f1484ea8affe5aTo8CcgbGIszj", "boundary": {"type": "before", "messageID": "msg_0eb7b1f9f001g95Bduh3bi8syS"}}, "projectID": "global", "model": {"id": "big-pickle", "providerID": "opencode", "variant": "default"}, "cost": 0, "tokens": {"input": 0, "output": 0, "reasoning": 0, "cache": {"read": 0, "write": 0}}, "time": {"created": 1790657111165, "updated": 1790657111165}, "title": "spike fork (fork #1)", "location": {"directory": "<work>"}, "permissions": [{"action": "*", "resource": "*", "effect": "allow"}, {"action": "subagent", "resource": "*", "effect": "deny"}]}}}}
 {"type": "expect_outbound", "label": "session.update", "frame": {"type": "session.update", "input": {"sessionID": "ses_f1484db83ffeLGtrRCFimo1H0e", "permissions": [{"action": "*", "resource": "*", "effect": "allow"}, {"action": "t3-code-*", "resource": "*", "effect": "deny"}, {"action": "t3-code-thread_opencode2-fork_target_*", "resource": "*", "effect": "allow"}]}}}
diff --git a/packages/provider-opencode/src/server/v2/adapter.ts b/packages/provider-opencode/src/server/v2/adapter.ts
index f49de61b24690..40fdb20ff4d8d 100644
--- a/packages/provider-opencode/src/server/v2/adapter.ts
+++ b/packages/provider-opencode/src/server/v2/adapter.ts
@@ -2925,12 +2925,19 @@ export const make = Effect.fn("OpenCode2Adapter.make")(function* (instanceId: Pr
       );
     });
 
-    // The API accepts one message type; boundaries require both user and synthetic messages.
-    const userMessages = (sessionId: string) =>
-      OpenCode2Client.paginate(
-        { sessionID: Session.ID.make(sessionId), limit: 100 },
-        client.message.list,
-      ).pipe(
+    // Rollback must validate full history before native mutation; forks only need prompts.
+    const userMessages = (sessionId: string, types?: ReadonlyArray<"user" | "synthetic">) =>
+      Stream.fromIterable(types ?? [undefined]).pipe(
+        Stream.flatMap((type) =>
+          OpenCode2Client.paginate(
+            {
+              sessionID: Session.ID.make(sessionId),
+              limit: 100,
+              ...(type === undefined ? {} : { type }),
+            },
+            client.message.list,
+          ),
+        ),
         Stream.runCollect,
         Effect.map(
           (messages) =>
@@ -4008,7 +4015,7 @@ export const make = Effect.fn("OpenCode2Adapter.make")(function* (instanceId: Pr
                   forkInput.sourceProviderTurns ?? [],
                   source.id,
                   selected,
-                  yield* userMessages(sourceId),
+                  yield* userMessages(sourceId, ["user", "synthetic"]),
                 );
           const forked = yield* client.session.fork({
             sessionID: Session.ID.make(sourceId),