diff --git a/apps/server/src/orchestration-v2/Orchestrator.ts b/apps/server/src/orchestration-v2/Orchestrator.ts
index e27f32ef84420..14a18be8a56e7 100644
--- a/apps/server/src/orchestration-v2/Orchestrator.ts
+++ b/apps/server/src/orchestration-v2/Orchestrator.ts
@@ -2941,6 +2941,29 @@ const makeOrchestrator = Effect.fn("orchestrationV2.Orchestrator.layer")(functio
           cause: `Thread ${command.threadId} is no longer empty.`,
         });
     }
+    const targetProjectId =
+      command.type === "thread.metadata.update" && command.projectId !== thread.projectId
+        ? command.projectId
+        : undefined;
+    if (targetProjectId !== undefined) {
+      const project = yield* projects.get(targetProjectId).pipe(mapDispatchError(command));
+      const { subagents } = yield* projectionStore
+        .getThreadRecords(command.threadId, ["subagents"])
+        .pipe(mapDispatchError(command));
+      if (
+        Option.isNone(project) ||
+        project.value.deletedAt !== null ||
+        thread.settledAt === null ||
+        thread.lineage.relationshipToParent === "subagent" ||
+        subagents.some((task) => task.childThreadId !== null)
+      ) {
+        return yield* new OrchestratorDispatchError({
+          commandId: command.commandId,
+          commandType: command.type,
+          cause: `Only a settled top-level thread without child threads can move to an existing project.`,
+        });
+      }
+    }
     if (command.type === "thread.archive" && thread.archivedAt !== null) {
       return yield* new OrchestratorDispatchError({
         commandId: command.commandId,
@@ -3387,6 +3410,9 @@ const makeOrchestrator = Effect.fn("orchestrationV2.Orchestrator.layer")(functio
                 : {}),
             ...(command.branch === undefined ? {} : { branch: command.branch }),
             ...(command.worktreePath === undefined ? {} : { worktreePath: command.worktreePath }),
+            ...(targetProjectId === undefined
+              ? {}
+              : { projectId: targetProjectId, branch: null, worktreePath: null }),
             ...(command.linkedPullRequest === undefined
               ? {}
               : {
diff --git a/apps/server/src/orchestration-v2/runtimeLayer.test.ts b/apps/server/src/orchestration-v2/runtimeLayer.test.ts
index 025191f098823..cd668040aa186 100644
--- a/apps/server/src/orchestration-v2/runtimeLayer.test.ts
+++ b/apps/server/src/orchestration-v2/runtimeLayer.test.ts
@@ -1872,6 +1872,78 @@ it.layer(layerLegacyImportTest)("OrchestrationV2 legacy import", (it) => {
 });
 
 it.layer(layerTest)("OrchestrationV2LayerLive lifecycle", (it) => {
+  it.effect("moves a settled thread to another project", () =>
+    Effect.gen(function* () {
+      const orchestrator = yield* Orchestrator.OrchestratorV2;
+      const threadId = ThreadId.make("runtime-layer-move-thread");
+      const fromProjectId = ProjectId.make("runtime-layer-move-from");
+      const toProjectId = ProjectId.make("runtime-layer-move-to");
+      for (const projectId of [fromProjectId, toProjectId]) {
+        yield* seedProject({
+          projectId,
+          title: projectId,
+          workspaceRoot: `/workspace/${projectId}`,
+          defaultModelSelection: null,
+          createdAt: "2026-09-07T00:00:00.000Z",
+        });
+      }
+      yield* orchestrator.dispatch({
+        type: "thread.create",
+        createdBy: "user",
+        creationSource: "web",
+        commandId: CommandId.make("runtime-layer-move-create"),
+        threadId,
+        projectId: fromProjectId,
+        title: "Move me",
+        modelSelection,
+        runtimeMode: "full-access",
+        interactionMode: "default",
+        branch: "feature/move",
+        worktreePath: "/workspace/move-from-worktree",
+      });
+      yield* orchestrator.dispatch({
+        type: "thread.settle",
+        commandId: CommandId.make("runtime-layer-move-settle"),
+        threadId,
+      });
+      yield* orchestrator.dispatch({
+        type: "thread.metadata.update",
+        commandId: CommandId.make("runtime-layer-move-to"),
+        threadId,
+        projectId: toProjectId,
+      });
+      const moved = (yield* orchestrator.getThreadProjection(threadId)).thread;
+      assert.deepInclude(moved, { projectId: toProjectId, branch: null, worktreePath: null });
+      const shell = yield* orchestrator.getShellSnapshot();
+      assert.equal(
+        shell.threads.find((candidate) => candidate.id === threadId)?.projectId,
+        toProjectId,
+      );
+      yield* orchestrator.dispatch({
+        type: "message.dispatch",
+        createdBy: "user",
+        creationSource: "web",
+        commandId: CommandId.make("runtime-layer-move-message"),
+        threadId,
+        messageId: MessageId.make("runtime-layer-move-message"),
+        text: "Unsettle this thread.",
+        attachments: [],
+        modelSelection,
+        dispatchMode: { type: "start_immediately" },
+      });
+      assert.isNull((yield* orchestrator.getThreadProjection(threadId)).thread.settledAt);
+      const unsettled = yield* orchestrator
+        .dispatch({
+          type: "thread.metadata.update",
+          commandId: CommandId.make("runtime-layer-move-unsettled"),
+          threadId,
+          projectId: fromProjectId,
+        })
+        .pipe(Effect.flip);
+      assert.instanceOf(unsettled, Orchestrator.OrchestratorDispatchError);
+    }),
+  );
+
   it.effect("applies lifecycle commands idempotently and emits archive/removal shell deltas", () =>
     Effect.gen(function* () {
       const orchestrator = yield* Orchestrator.OrchestratorV2;
diff --git a/packages/contracts/src/orchestrationV2.ts b/packages/contracts/src/orchestrationV2.ts
index f4e8303972267..9c451bf783b6b 100644
--- a/packages/contracts/src/orchestrationV2.ts
+++ b/packages/contracts/src/orchestrationV2.ts
@@ -2893,6 +2893,7 @@ export const OrchestrationV2Command = Schema.Union([
     threadId: ThreadId,
     title: Schema.optional(TrimmedNonEmptyString),
     regenerateTitle: Schema.optional(Schema.Boolean),
+    projectId: Schema.optional(ProjectId),
     branch: Schema.optional(Schema.NullOr(TrimmedNonEmptyString)),
     worktreePath: Schema.optional(Schema.NullOr(TrimmedNonEmptyString)),
     expectedWorktreePath: Schema.optional(Schema.NullOr(TrimmedNonEmptyString)),