diff --git a/server/__tests__/lanes-api.test.js b/server/__tests__/lanes-api.test.js
index 740c1301..af5b286a 100644
--- a/server/__tests__/lanes-api.test.js
+++ b/server/__tests__/lanes-api.test.js
@@ -988,3 +988,23 @@ exit 1
     assert.equal(r.body.checks[0].name, "tests");
   });
 });
+
+describe("/api/lanes tool tests", () => {
+  it("POST /api/lanes/ensure stores the requested tool", async () => {
+    const res = await request("POST", "/api/lanes/ensure", {
+      cwd: "/tmp/codex-lane",
+      tool: "codex",
+    });
+    assert.equal(res.status, 201);
+    assert.equal(res.body.lane.tool, "codex");
+  });
+
+  it("POST /api/lanes/ensure rejects an unknown tool", async () => {
+    const res = await request("POST", "/api/lanes/ensure", {
+      cwd: "/tmp/bad-tool",
+      tool: "cursor",
+    });
+    assert.equal(res.status, 400);
+    assert.equal(res.body.error.code, "EBADTOOL");
+  });
+});
diff --git a/server/__tests__/run.test.js b/server/__tests__/run.test.js
index 952470a0..d18fa123 100644
--- a/server/__tests__/run.test.js
+++ b/server/__tests__/run.test.js
@@ -174,4 +174,15 @@ describe("/api/run", () => {
     assert.equal(status, 200);
     assert.ok(Array.isArray(body.items));
   });
+
+  it("GET /api/run/binary?tool=codex probes codex, not claude", async () => {
+    const res = await fetchJson("/api/run/binary?tool=codex");
+    assert.equal(res.status, 200);
+    assert.equal(typeof res.body.found, "boolean");
+  });
+
+  it("GET /api/run/binary rejects an unknown tool", async () => {
+    const res = await fetchJson("/api/run/binary?tool=rm");
+    assert.equal(res.status, 400);
+  });
 });
diff --git a/server/routes/lanes.js b/server/routes/lanes.js
index 592335bb..4231b252 100644
--- a/server/routes/lanes.js
+++ b/server/routes/lanes.js
@@ -260,6 +260,11 @@ router.post("/ensure", sameOriginGuard, (req, res) => {
   // path and lane uniqueness stays meaningful. Callers that do care pass one
   // through unchanged.
   const cwd = typeof body.cwd === "string" && body.cwd.trim() ? body.cwd.trim() : os.homedir();
+
+  if (body.tool !== undefined && !lanesLib.VALID_TOOLS.has(body.tool)) {
+    return res.status(400).json({ error: { code: "EBADTOOL", message: "unknown tool" } });
+  }
+
   const owner = lanesLib.resolveLaneByCwd(cwd);
   if (owner) {
     // First-write wins on the title: an ensure-with-title on an existing lane
@@ -276,11 +281,12 @@ router.post("/ensure", sameOriginGuard, (req, res) => {
       cwd,
       title: body.title || "",
       ...(body.pipeline ? { pipeline: body.pipeline } : {}),
+      ...(body.tool ? { tool: body.tool } : {}),
     });
     broadcastLane(lane.id);
     return res.status(201).json({ lane: payload(lane), created: true });
   } catch (err) {
-    if (err.code === "EBADCWD" || err.code === "EBADPIPELINE") {
+    if (err.code === "EBADCWD" || err.code === "EBADPIPELINE" || err.code === "EBADTOOL") {
       return res.status(400).json({ error: { code: err.code, message: err.message } });
     }
     // The cwd UNIQUE constraint is the arbiter: someone else won the race, so
@@ -641,6 +647,11 @@ router.get("/:id/ci/status", async (req, res) => {
  */
 router.post("/worktree", sameOriginGuard, async (req, res) => {
   const body = req.body || {};
+
+  if (body.tool !== undefined && !lanesLib.VALID_TOOLS.has(body.tool)) {
+    return res.status(400).json({ error: { code: "EBADTOOL", message: "unknown tool" } });
+  }
+
   const sourceRepo = body.sourceRepo;
   if (
     typeof sourceRepo !== "string" ||
@@ -706,6 +717,7 @@ router.post("/worktree", sameOriginGuard, async (req, res) => {
       base_branch: body.base || null,
       slug,
       ...(body.pipeline ? { pipeline: body.pipeline } : {}),
+      ...(body.tool ? { tool: body.tool } : {}),
     });
     lane = lanesLib.updateLane(lane.id, { status: "provisioning" });
   } catch (err) {
@@ -1230,9 +1242,16 @@ router.post("/:id/:action", sameOriginGuard, async (req, res) => {
             laneId: current.id,
             initialPrompt: body.prompt || "",
             cwd: current.cwd,
+            // The tool is the LANE's fact, never the request's: a client that
+            // asked for the other CLI would otherwise get a pane that doesn't
+            // match the lane's badge, its history, or its binary probe.
+            tool: current.tool || "claude",
             model: body.model,
             permissionMode: body.permissionMode,
             effort: body.effort,
+            sandbox: body.sandbox,
+            approval: body.approval,
+            resumeLast: body.resumeLast === true,
             resumeSessionId: body.resumeSessionId || (body.resume ? current.session_id : undefined),
           });
           lanesLib.updateLane(current.id, { run_id: handle.id, status: "running" });
diff --git a/server/routes/run.js b/server/routes/run.js
index d4dfeec6..0a63cb03 100644
--- a/server/routes/run.js
+++ b/server/routes/run.js
@@ -24,6 +24,7 @@ const fs = require("node:fs");
 const path = require("node:path");
 const runs = require("../lib/pty-run");
 const tmux = require("../lib/tmux");
+const lanesLib = require("../lib/lanes");
 
 const router = Router();
 
@@ -236,20 +237,22 @@ router.get("/files", (req, res) => {
   res.json({ items: results.slice(0, MAX_RESULTS) });
 });
 
-router.get("/binary", (_req, res) => {
-  // Surface whether `claude` is on PATH so the UI can show a helpful error
-  // before the user clicks Run. We don't actually invoke it — just let the
-  // user know the spawn will work.
+router.get("/binary", (req, res) => {
+  // Surface whether the lane's CLI is on PATH so the UI can show a helpful
+  // error before the user clicks Run. We don't actually invoke it. The name is
+  // taken from a fixed allowlist, never from the query string directly — this
+  // string reaches `which`.
+  const tool = req.query.tool === undefined ? "claude" : String(req.query.tool);
+  if (tool !== "claude" && tool !== "codex") {
+    return res.status(400).json({ error: { code: "EBADTOOL", message: "unknown tool" } });
+  }
   const which = require("node:child_process").spawnSync(
     process.platform === "win32" ? "where" : "which",
-    ["claude"],
+    [tool],
     { encoding: "utf8" }
   );
   const stdout = (which.stdout || "").trim();
-  res.json({
-    found: which.status === 0 && stdout.length > 0,
-    path: stdout || null,
-  });
+  res.json({ found: which.status === 0 && stdout.length > 0, path: stdout || null });
 });
 
 router.get("/tmux", (_req, res) => {
@@ -269,9 +272,11 @@ router.post("/", (req, res) => {
     return res.status(400).json({ error: { code: err.code, message: err.message } });
   }
   try {
+    const lane = lanesLib.getLane(laneId);
     const handle = runs.spawnRun({
       laneId,
       cwd,
+      tool: lane?.tool || "claude",
       model: typeof body.model === "string" && body.model ? body.model : null,
       permissionMode:
         typeof body.permissionMode === "string" && ALLOWED_PERMISSION_MODES.has(body.permissionMode)