diff --git a/src/tools/background-task/create-background-task.ts b/src/tools/background-task/create-background-task.ts
index dbda87948..9ed3624b9 100644
--- a/src/tools/background-task/create-background-task.ts
+++ b/src/tools/background-task/create-background-task.ts
@@ -94,6 +94,13 @@ export function createBackgroundTask(
           await delay(WAIT_FOR_SESSION_INTERVAL_MS)
         }
 
+        // Capture late-arriving sessionId between the wait-loop exit and
+        // metadata publish so the OpenCode TUI subagent entry has a navigable
+        // target (issue #4252).
+        if (!sessionId) {
+          sessionId = manager.getTask(task.id)?.sessionId
+        }
+
         const bgMeta = {
           title: args.description,
           metadata: {
diff --git a/src/tools/delegate-task/background-task.ts b/src/tools/delegate-task/background-task.ts
index 767bab764..f15211383 100644
--- a/src/tools/delegate-task/background-task.ts
+++ b/src/tools/delegate-task/background-task.ts
@@ -160,6 +160,15 @@ export async function executeBackgroundTask(
       return `Task failed to start (status: ${updatedTask.status}).\n\nTask ID: ${task.id}`
     }
 
+    // Capture late-arriving sessionId from the race window between wait-loop
+    // exit and metadata publish. Without this, a session that gets created
+    // moments after the wait loop returns leaves metadata.sessionId undefined,
+    // which makes the OpenCode TUI render the subagent entry as a perpetual
+    // spinner with no clickable navigation target (issue #4252).
+    if (!sessionId && updatedTask?.sessionId) {
+      sessionId = updatedTask.sessionId
+    }
+
     if (sessionId) {
       registerBackgroundSessionContext({
         sessionId,
diff --git a/src/tools/delegate-task/late-session-id-capture.test.ts b/src/tools/delegate-task/late-session-id-capture.test.ts
new file mode 100644
index 000000000..09edacb4f
--- /dev/null
+++ b/src/tools/delegate-task/late-session-id-capture.test.ts
@@ -0,0 +1,70 @@
+const { describe, test, expect } = require("bun:test")
+
+import type { DelegateTaskArgs, ToolContextWithMetadata } from "./types"
+import type { ParentContext } from "./executor-types"
+import { unsafeTestValue } from "../../../test-support/unsafe-test-value"
+
+const MODEL = { providerID: "anthropic", modelID: "claude-sonnet-4-6" }
+
+function makeMockCtx(): ToolContextWithMetadata & { captured: any[] } {
+  const captured: any[] = []
+  return {
+    sessionID: "ses_parent",
+    messageID: "msg_parent",
+    agent: "sisyphus",
+    abort: new AbortController().signal,
+    callID: "call_001",
+    metadata: async (input: any) => { captured.push(input) },
+    captured,
+  }
+}
+
+const parentContext: ParentContext = {
+  sessionID: "ses_parent",
+  messageID: "msg_parent",
+  agent: "sisyphus",
+  model: MODEL,
+}
+
+describe("background-task late sessionId capture (issue #4252)", () => {
+  test("#given launch returns no sessionId and getTask returns one #when publishing metadata #then sessionId is captured so TUI entry is clickable", async () => {
+    const { executeBackgroundTask } = require("./background-task")
+    const ctx = makeMockCtx()
+    const args: DelegateTaskArgs = {
+      description: "deferred task",
+      prompt: "do it",
+      load_skills: [],
+      run_in_background: true,
+      subagent_type: "explore",
+    }
+
+    // launch returns a pending task with no sessionId; getTask returns the
+    // same task with sessionId populated *after* the wait loop exits. This
+    // simulates the race where the subagent session is created moments after
+    // we stop polling, and is the exact condition that left the OpenCode TUI
+    // session entry stuck spinning with no click target on v4.2.3.
+    await executeBackgroundTask(args, ctx, unsafeTestValue({
+      manager: {
+        launch: async () => ({
+          id: "bg_late",
+          description: "deferred task",
+          agent: "explore",
+          status: "pending",
+        }),
+        getTask: () => ({
+          id: "bg_late",
+          description: "deferred task",
+          agent: "explore",
+          status: "running",
+          sessionId: "ses_late",
+        }),
+      },
+    }), parentContext, "explore", MODEL, undefined)
+
+    const meta = ctx.captured.find((m: any) => m.metadata?.sessionId)
+    expect(meta).toBeDefined()
+    expect(meta.metadata.sessionId).toBe("ses_late")
+    expect(meta.metadata.taskId).toBe("ses_late")
+    expect(meta.metadata.backgroundTaskId).toBe("bg_late")
+  })
+})