diff --git a/scripts/host-adapter-contract-test.mjs b/scripts/host-adapter-contract-test.mjs
index 1263077e..dd808ea2 100644
--- a/scripts/host-adapter-contract-test.mjs
+++ b/scripts/host-adapter-contract-test.mjs
@@ -57,6 +57,7 @@ assert.equal(compactTuiCommandName("other"), undefined)
   assert.deepEqual(ordered.map((item) => item.info.id), ["a", "b", "c"])
 
   assert.equal(await activeRunCompletionFromMessages("/tmp", {}, "missing", { startedAt: 100 }), "unknown")
+  assert.equal(await activeRunCompletionFromMessages("/tmp", messagesClient([]), "empty-history", { startedAt: 100 }), "unknown")
   assert.equal(await activeRunCompletionFromMessages(
     "/tmp", messagesClient([{ info: { role: "assistant", time: { created: 50, completed: 90 } } }]), "old", { startedAt: 100 },
   ), "incomplete")
diff --git a/scripts/session-status-test.mjs b/scripts/session-status-test.mjs
index e26f3ff1..1637e2c6 100644
--- a/scripts/session-status-test.mjs
+++ b/scripts/session-status-test.mjs
@@ -231,6 +231,17 @@ try {
     track(sessionID)
     runtime.clearSessionStatus(sessionID)
     const active = { jobId: "job", job: {}, startedAt: clock - 100 }
+    completion = "unknown"
+    assert.equal(await runtime.canFinalizeActiveRun("/repo", {}, sessionID, active), true)
+
+    completion = "incomplete"
+    assert.equal(
+      await runtime.canFinalizeActiveRun("/repo", {}, sessionID, active),
+      false,
+      "a transient idle boundary must not finalize a Loop-owned run while the assistant turn is still incomplete",
+    )
+
+    completion = "completed"
     assert.equal(await runtime.canFinalizeActiveRun("/repo", {}, sessionID, active), true)
 
     markToolCallActive({ sessionID, callID: "tool-finalize" })
@@ -240,6 +251,7 @@ try {
     runtime.markSessionStatus(sessionID, "idle", clock + 1)
     const client = { session: { status: async () => { throw new Error("status unavailable") } } }
     assert.equal(await runtime.canFinalizeActiveRun("/repo", client, sessionID, active, { requireIdle: true }), true)
+    completion = "unknown"
   }
 
   {
diff --git a/src/index.js b/src/index.js
index 02ecc209..cd83dd08 100644
--- a/src/index.js
+++ b/src/index.js
@@ -819,6 +819,8 @@ async function activeRunCompletionFromMessages(directory, client, sessionID, act
   if (!messages)
     return "unknown";
   const ordered = orderedSessionMessages(messages);
+  if (ordered.length === 0)
+    return "unknown";
   const tail = ordered.at(-1);
   const info = tail?.info || tail;
   if (!info || info.role !== "assistant")
@@ -2994,8 +2996,10 @@ function createSessionStatusRuntime(options = {}) {
   async function canFinalizeActiveRun(directory, client, sessionID, active, options = {}) {
     if (hasActiveToolCalls(sessionID) || hasBusyDescendant(sessionID))
       return false;
-    if (!options.requireIdle && !options.forceStale)
-      return true;
+    if (!options.requireIdle && !options.forceStale) {
+      const completion = await activeRunCompletionFromMessages2(directory, client, sessionID, active);
+      return completion !== "incomplete";
+    }
     const completion = options.forceStale ? await activeRunCompletionFromMessages2(directory, client, sessionID, active) : undefined;
     if (settledAssistantCompletion(completion))
       return true;
diff --git a/src/server.js b/src/server.js
index 2423c5d2..30e9412a 100644
--- a/src/server.js
+++ b/src/server.js
@@ -819,6 +819,8 @@ async function activeRunCompletionFromMessages(directory, client, sessionID, act
   if (!messages)
     return "unknown";
   const ordered = orderedSessionMessages(messages);
+  if (ordered.length === 0)
+    return "unknown";
   const tail = ordered.at(-1);
   const info = tail?.info || tail;
   if (!info || info.role !== "assistant")
@@ -2994,8 +2996,10 @@ function createSessionStatusRuntime(options = {}) {
   async function canFinalizeActiveRun(directory, client, sessionID, active, options = {}) {
     if (hasActiveToolCalls(sessionID) || hasBusyDescendant(sessionID))
       return false;
-    if (!options.requireIdle && !options.forceStale)
-      return true;
+    if (!options.requireIdle && !options.forceStale) {
+      const completion = await activeRunCompletionFromMessages2(directory, client, sessionID, active);
+      return completion !== "incomplete";
+    }
     const completion = options.forceStale ? await activeRunCompletionFromMessages2(directory, client, sessionID, active) : undefined;
     if (settledAssistantCompletion(completion))
       return true;
diff --git a/src/source/opencode/host.js b/src/source/opencode/host.js
index 34330b74..f5aa5c79 100644
--- a/src/source/opencode/host.js
+++ b/src/source/opencode/host.js
@@ -69,6 +69,7 @@ export async function activeRunCompletionFromMessages(directory, client, session
   const messages = await readRecentSessionMessages(client, sessionID, directory)
   if (!messages) return "unknown"
   const ordered = orderedSessionMessages(messages)
+  if (ordered.length === 0) return "unknown"
   const tail = ordered.at(-1)
   const info = tail?.info || tail
   if (!info || info.role !== "assistant") return "incomplete"
diff --git a/src/source/runtime/session-status.js b/src/source/runtime/session-status.js
index a59d15c8..b0aa4da8 100644
--- a/src/source/runtime/session-status.js
+++ b/src/source/runtime/session-status.js
@@ -113,7 +113,17 @@ export function createSessionStatusRuntime(options = {}) {
 
   async function canFinalizeActiveRun(directory, client, sessionID, active, options = {}) {
     if (hasActiveToolCalls(sessionID) || hasBusyDescendant(sessionID)) return false
-    if (!options.requireIdle && !options.forceStale) return true
+
+    // OpenCode 1.x can emit transient session.idle boundaries between tool
+    // steps while the same assistant turn is still in progress. When the
+    // message API can prove that the current assistant message is incomplete,
+    // keep the Loop-owned run active instead of treating that transient idle
+    // as a completed turn. Preserve the historical fallback when message
+    // completion evidence is unavailable.
+    if (!options.requireIdle && !options.forceStale) {
+      const completion = await activeRunCompletionFromMessages(directory, client, sessionID, active)
+      return completion !== "incomplete"
+    }
 
     const completion = options.forceStale
       ? await activeRunCompletionFromMessages(directory, client, sessionID, active)