diff --git a/src/shared/tmux/constants.ts b/src/shared/tmux/constants.ts
index 5299d3964..71205a886 100644
--- a/src/shared/tmux/constants.ts
+++ b/src/shared/tmux/constants.ts
@@ -1,11 +1,15 @@
 // Polling interval for background session status checks
 export const POLL_INTERVAL_BACKGROUND_MS = 2000
 
-// Maximum idle time before session considered stale
-export const SESSION_TIMEOUT_MS = 10 * 60 * 1000  // 10 minutes
+// Long-running subagent work can legitimately stay open for a while.
+// The tmux-subagent stability fixes raised this guard from 10 minutes after
+// polling closed active panes during long tasks.
+export const SESSION_TIMEOUT_MS = 60 * 60 * 1000  // 60 minutes
 
-// Grace period for missing session before cleanup
-export const SESSION_MISSING_GRACE_MS = 6000  // 6 seconds
+// Status queries can transiently miss live sessions under load.
+// The tmux-subagent stability fixes raised this guard from 6 seconds after
+// false missing detections closed healthy panes.
+export const SESSION_MISSING_GRACE_MS = 30 * 1000  // 30 seconds
 
 // Session readiness polling config
 export const SESSION_READY_POLL_INTERVAL_MS = 500
diff --git a/src/shared/tmux/index.ts b/src/shared/tmux/index.ts
index a86723661..b523bf642 100644
--- a/src/shared/tmux/index.ts
+++ b/src/shared/tmux/index.ts
@@ -1,3 +1,4 @@
 export * from "./types"
 export * from "./constants"
+export * from "./runner"
 export * from "./tmux-utils"
diff --git a/src/shared/tmux/runner.test.ts b/src/shared/tmux/runner.test.ts
new file mode 100644
index 000000000..9832c99b2
--- /dev/null
+++ b/src/shared/tmux/runner.test.ts
@@ -0,0 +1,127 @@
+/// <reference types="bun-types" />
+
+import { afterAll, describe, expect, test } from "bun:test"
+import { randomUUID } from "node:crypto"
+import fs from "node:fs/promises"
+import os from "node:os"
+import path from "node:path"
+
+import { runTmuxCommand } from "./runner"
+
+const temporaryDirectories: string[] = []
+
+async function createTemporaryDirectory(): Promise<string> {
+	const directoryPath = await fs.mkdtemp(path.join(os.tmpdir(), "tmux-runner-"))
+	temporaryDirectories.push(directoryPath)
+	return directoryPath
+}
+
+async function readInvocationCount(counterFilePath: string): Promise<number> {
+	const count = await fs.readFile(counterFilePath, "utf8")
+	return Number.parseInt(count, 10)
+}
+
+afterAll(async () => {
+	for (const directoryPath of temporaryDirectories) {
+		await fs.rm(directoryPath, { recursive: true, force: true })
+	}
+})
+
+describe("runTmuxCommand", () => {
+	test("#given command exits 0 with stdout #when run #then success true, output and stdout equal trimmed value, stderr empty", async () => {
+		// given
+		const commandArguments = ["-c", "printf '%s\\n' '%42'"]
+
+		// when
+		const result = await runTmuxCommand("sh", commandArguments)
+
+		// then
+		expect(result).toEqual({
+			success: true,
+			output: "%42",
+			stdout: "%42",
+			stderr: "",
+			exitCode: 0,
+		})
+	})
+
+	test("#given command exits 1 with stderr #when run #then success false, stderr populated", async () => {
+		// given
+		const commandArguments = ["-c", "printf '%s\\n' 'some error' >&2; exit 1"]
+
+		// when
+		const result = await runTmuxCommand("sh", commandArguments)
+
+		// then
+		expect(result.success).toBe(false)
+		expect(result.stderr).toBe("some error")
+		expect(result.exitCode).toBe(1)
+	})
+
+	test("#given retry=2 and first exit nonzero #when run #then calls spawn twice before returning failure", async () => {
+		// given
+		const temporaryDirectory = await createTemporaryDirectory()
+		const counterFilePath = path.join(temporaryDirectory, `${randomUUID()}.count`)
+		const commandScript = `counter_file="$1"; count=0; if [ -f "$counter_file" ]; then count=$(cat "$counter_file"); fi; count=$((count + 1)); printf '%s' "$count" > "$counter_file"; printf '%s\\n' 'temporary error' >&2; exit 1`
+
+		// when
+		const result = await runTmuxCommand("sh", ["-c", commandScript, "sh", counterFilePath], { retry: 2 })
+
+		// then
+		expect(result.success).toBe(false)
+		expect(result.stderr).toBe("temporary error")
+		expect(await readInvocationCount(counterFilePath)).toBe(3)
+	})
+
+	test("#given retry=2 and stderr contains 'can't find pane' #when run #then does NOT retry", async () => {
+		// given
+		const temporaryDirectory = await createTemporaryDirectory()
+		const counterFilePath = path.join(temporaryDirectory, `${randomUUID()}.count`)
+		const commandScript = `counter_file="$1"; count=0; if [ -f "$counter_file" ]; then count=$(cat "$counter_file"); fi; count=$((count + 1)); printf '%s' "$count" > "$counter_file"; printf '%s\\n' "can't find pane: %1" >&2; exit 1`
+
+		// when
+		const result = await runTmuxCommand("sh", ["-c", commandScript, "sh", counterFilePath], { retry: 2 })
+
+		// then
+		expect(result.success).toBe(false)
+		expect(result.stderr).toContain("can't find pane")
+		expect(await readInvocationCount(counterFilePath)).toBe(1)
+	})
+
+	test("#given timeoutMs=50 and command sleeps 500ms #when run #then returns timeout failure", async () => {
+		// given
+		const commandArguments = ["-c", "sleep 0.5"]
+
+		// when
+		const result = await runTmuxCommand("sh", commandArguments, { timeoutMs: 50 })
+
+		// then
+		expect(result.success).toBe(false)
+		expect(result.exitCode).toBe(-1)
+		expect(result.stderr).toContain("timeout")
+	})
+
+	test("#given stdout contains trailing newline #when run #then output is trimmed", async () => {
+		// given
+		const commandArguments = ["-c", "printf '%s\\n\\n' '%7'"]
+
+		// when
+		const result = await runTmuxCommand("sh", commandArguments)
+
+		// then
+		expect(result.output).toBe("%7")
+		expect(result.stdout).toBe("%7")
+	})
+
+	test("#given backward-compat consumer destructures {success, output} #when result returned #then both fields present and correct", async () => {
+		// given
+		const commandArguments = ["-c", "printf '%s\\n' '%9'"]
+
+		// when
+		const { success, output } = await runTmuxCommand("sh", commandArguments)
+
+		// then
+		expect(success).toBe(true)
+		expect(output).toBe("%9")
+	})
+})
diff --git a/src/shared/tmux/runner.ts b/src/shared/tmux/runner.ts
new file mode 100644
index 000000000..0290a96aa
--- /dev/null
+++ b/src/shared/tmux/runner.ts
@@ -0,0 +1,107 @@
+import { spawn } from "bun"
+
+type RunTmuxOptions = {
+	retry?: number
+	timeoutMs?: number
+}
+
+export type TmuxCommandResult = {
+	success: boolean
+	output: string
+	stdout: string
+	stderr: string
+	exitCode: number
+}
+
+const TERMINAL_TMUX_ERROR_PATTERN = /can't find (pane|session)/i
+
+function createTmuxCommandResult(stdout: string, stderr: string, exitCode: number): TmuxCommandResult {
+	return {
+		success: exitCode === 0,
+		output: stdout,
+		stdout,
+		stderr,
+		exitCode,
+	}
+}
+
+function isTerminalTmuxError(stderr: string): boolean {
+	return TERMINAL_TMUX_ERROR_PATTERN.test(stderr)
+}
+
+/**
+ * Detect whether we are running inside cmux (cmux omo).
+ * When cmux-omo sets up the environment it injects a tmux shim and sets
+ * CMUX_SOCKET_PATH / TMUX. If detected, redirect tmux commands to
+ * `cmux __tmux-compat` so they become native cmux splits instead of
+ * failing because there is no real tmux server running.
+ */
+function resolveTmuxExecutable(tmuxPath: string): string[] {
+	const inCmux = Boolean(process.env.CMUX_SOCKET_PATH) ||
+		process.env.TMUX?.includes("cmuxterm") === true
+	if (inCmux) {
+		return ["cmux", "__tmux-compat"]
+	}
+	return [tmuxPath]
+}
+
+async function runTmuxCommandOnce(tmuxPath: string, args: Array<string>, timeoutMs?: number): Promise<TmuxCommandResult> {
+	const abortController = new AbortController()
+	const subprocess = spawn([...resolveTmuxExecutable(tmuxPath), ...args], {
+		stdout: "pipe",
+		stderr: "pipe",
+		signal: abortController.signal,
+	})
+	const stdoutPromise = new Response(subprocess.stdout).text()
+	const stderrPromise = new Response(subprocess.stderr).text()
+
+	let timeoutId: ReturnType<typeof setTimeout> | undefined
+
+	try {
+		const exitCodeOrTimeout = timeoutMs === undefined
+			? await subprocess.exited
+			: await Promise.race<number | "timeout">(([
+					subprocess.exited,
+					new Promise<"timeout">((resolve) => {
+						timeoutId = setTimeout(() => {
+							abortController.abort()
+							resolve("timeout")
+						}, timeoutMs)
+					}),
+				]))
+
+		if (exitCodeOrTimeout === "timeout") {
+			void subprocess.exited.catch(() => undefined)
+			void stdoutPromise.catch(() => "")
+			void stderrPromise.catch(() => "")
+			return createTmuxCommandResult("", "timeout", -1)
+		}
+
+		const [stdout, stderr] = await Promise.all([stdoutPromise, stderrPromise])
+		return createTmuxCommandResult(stdout.trim(), stderr.trim(), exitCodeOrTimeout)
+	} finally {
+		if (timeoutId !== undefined) {
+			clearTimeout(timeoutId)
+		}
+	}
+}
+
+export async function runTmuxCommand(tmuxPath: string, args: string[], options: RunTmuxOptions = {}): Promise<TmuxCommandResult> {
+	const retryCount = Math.max(0, options.retry ?? 0)
+	let lastResult = createTmuxCommandResult("", "", 1)
+
+	for (let attempt = 0; attempt <= retryCount; attempt += 1) {
+		const result = await runTmuxCommandOnce(tmuxPath, args, options.timeoutMs)
+		lastResult = result
+
+		if (result.exitCode === 0) {
+			return result
+		}
+
+		if (attempt === retryCount || isTerminalTmuxError(result.stderr)) {
+			return result
+		}
+	}
+
+	return lastResult
+}