diff --git a/CLI_AND_DAEMON.md b/CLI_AND_DAEMON.md
index 8ed61a4b0..f5f96f801 100644
--- a/CLI_AND_DAEMON.md
+++ b/CLI_AND_DAEMON.md
@@ -168,7 +168,7 @@ Daemon behavior is configured via flags or environment variables:
 |---------|------|--------------|---------|
 | Poll interval | `--poll-interval` | `MULTICA_DAEMON_POLL_INTERVAL` | `3s` |
 | Heartbeat interval | `--heartbeat-interval` | `MULTICA_DAEMON_HEARTBEAT_INTERVAL` | `15s` |
-| Agent timeout | `--agent-timeout` | `MULTICA_AGENT_TIMEOUT` | `2h` |
+| Agent timeout | `--agent-timeout` | `MULTICA_AGENT_TIMEOUT` | `0` (no cap; bounded by the watchdogs) |
 | Codex semantic inactivity timeout | `--codex-semantic-inactivity-timeout` | `MULTICA_CODEX_SEMANTIC_INACTIVITY_TIMEOUT` | `10m` |
 | Max concurrent tasks | `--max-concurrent-tasks` | `MULTICA_DAEMON_MAX_CONCURRENT_TASKS` | `20` |
 | Daemon ID | `--daemon-id` | `MULTICA_DAEMON_ID` | hostname |
diff --git a/apps/docs/content/docs/cli/reference.zh.mdx b/apps/docs/content/docs/cli/reference.zh.mdx
index 28bf22dfa..7bc069ba6 100644
--- a/apps/docs/content/docs/cli/reference.zh.mdx
+++ b/apps/docs/content/docs/cli/reference.zh.mdx
@@ -115,7 +115,7 @@ Daemon behavior is configured via flags or environment variables:
 |---------|------|--------------|---------|
 | Poll interval | `--poll-interval` | `MULTICA_DAEMON_POLL_INTERVAL` | `3s` |
 | Heartbeat interval | `--heartbeat-interval` | `MULTICA_DAEMON_HEARTBEAT_INTERVAL` | `15s` |
-| Agent timeout | `--agent-timeout` | `MULTICA_AGENT_TIMEOUT` | `2h` |
+| Agent timeout | `--agent-timeout` | `MULTICA_AGENT_TIMEOUT` | `0`（不限制，由看门狗兜底）|
 | Max concurrent tasks | `--max-concurrent-tasks` | `MULTICA_DAEMON_MAX_CONCURRENT_TASKS` | `20` |
 | Daemon ID | `--daemon-id` | `MULTICA_DAEMON_ID` | hostname |
 | Device name | `--device-name` | `MULTICA_DAEMON_DEVICE_NAME` | hostname |
diff --git a/apps/docs/content/docs/environment-variables.zh.mdx b/apps/docs/content/docs/environment-variables.zh.mdx
index ca4bc989f..d3f8c2c37 100644
--- a/apps/docs/content/docs/environment-variables.zh.mdx
+++ b/apps/docs/content/docs/environment-variables.zh.mdx
@@ -179,6 +179,9 @@ API 返回的 `download_url` 在未配置 CloudFront 签名时会指向 `GET /ap
 | `MULTICA_DAEMON_HEARTBEAT_INTERVAL` | `15s` | 心跳频率 |
 | `MULTICA_DAEMON_POLL_INTERVAL` | `3s` | 任务轮询频率 |
 | `MULTICA_DAEMON_MAX_CONCURRENT_TASKS` | `20` | 并发任务上限 |
+| `MULTICA_AGENT_TIMEOUT` | `0` | 单次任务的绝对墙钟上限；`0` = 不设上限，任务只受看门狗约束（活跃任务不会因为跑得久被杀）。想要硬性成本/资源天花板时再设一个正值 |
+| `MULTICA_AGENT_IDLE_WATCHDOG` | `30m` | 空闲看门狗：backend 持续静默（无消息、消息队列为空、且没有工具在途）这么久就 force-stop。`0` = 关闭整套看门狗 |
+| `MULTICA_AGENT_TOOL_WATCHDOG` | `2h` | 工具在途时的静默上限：某个工具调用发出后长时间无任何输出（疑似卡死的子进程）这么久就 force-stop。`0` = 关闭该兜底（在途工具永不被停）|
 | `MULTICA_<PROVIDER>_PATH` | 对应 CLI 名 | 各 AI 编程工具的可执行文件路径（如 `MULTICA_CLAUDE_PATH`）|
 | `MULTICA_<PROVIDER>_MODEL` | 空 | 各 AI 编程工具的默认模型 |
 
diff --git a/apps/docs/content/docs/tasks.zh.mdx b/apps/docs/content/docs/tasks.zh.mdx
index 4e30e554f..c0663e0f1 100644
--- a/apps/docs/content/docs/tasks.zh.mdx
+++ b/apps/docs/content/docs/tasks.zh.mdx
@@ -42,6 +42,8 @@ Multica 服务器每 30 秒扫描一次，有两种超时会触发失败：
 
 两种超时的失败原因都是 `timeout`，**会自动重试**（下一节）。关联的运行时失联判定见 [守护进程与运行时 → 运行时什么时候被判定为离线](/daemon-runtimes#运行时什么时候被判定为离线)。
 
+上面这层是**服务端的粗粒度兜底**——按任务启动时间算，不看任务是否还在活动。真正区分「卡死」和「正常的长任务」的是**本地守护进程**：它不再用固定墙钟时长砍任务（`MULTICA_AGENT_TIMEOUT` 默认 `0` = 不设上限），而是看活动——只要 agent 还在持续产出事件（消息、工具调用），守护进程就不会因为跑得久判它超时（服务端那条 2.5h 仍是外层上限）。只有真正静默卡死时才会被**空闲看门狗**（`MULTICA_AGENT_IDLE_WATCHDOG`，默认 30 分钟）终止；如果是某个工具调用发出后长时间无任何输出（疑似卡死的子进程），则由更大的**工具看门狗**预算（`MULTICA_AGENT_TOOL_WATCHDOG`，默认 2 小时）兜底。这类被看门狗终止的任务失败原因是 `idle_watchdog`，和墙钟 `timeout` 区分开。各参数见 [环境变量 → 守护进程的调节参数](/environment-variables#守护进程的调节参数)。
+
 ## 哪些失败会自动重试，哪些不会
 
 失败分两类：**可重试**和**不可重试**。
diff --git a/server/cmd/multica/cmd_daemon.go b/server/cmd/multica/cmd_daemon.go
index 984cb3193..96123b2b3 100644
--- a/server/cmd/multica/cmd_daemon.go
+++ b/server/cmd/multica/cmd_daemon.go
@@ -78,7 +78,7 @@ func init() {
 	f.String("runtime-name", "", "Runtime display name (env: MULTICA_AGENT_RUNTIME_NAME)")
 	f.Duration("poll-interval", 0, "Task poll interval (env: MULTICA_DAEMON_POLL_INTERVAL)")
 	f.Duration("heartbeat-interval", 0, "Heartbeat interval (env: MULTICA_DAEMON_HEARTBEAT_INTERVAL)")
-	f.Duration("agent-timeout", 0, "Per-task timeout (env: MULTICA_AGENT_TIMEOUT)")
+	f.Duration("agent-timeout", 0, "Absolute per-task wall-clock cap; 0 = no cap, rely on the watchdogs (env: MULTICA_AGENT_TIMEOUT)")
 	f.Duration("codex-semantic-inactivity-timeout", 0, "Codex semantic inactivity timeout (env: MULTICA_CODEX_SEMANTIC_INACTIVITY_TIMEOUT)")
 	f.Int("max-concurrent-tasks", 0, "Max tasks running in parallel (env: MULTICA_DAEMON_MAX_CONCURRENT_TASKS)")
 	f.Bool("no-auto-update", false, "Disable periodic CLI self-update (env: MULTICA_DAEMON_AUTO_UPDATE=false)")
@@ -97,7 +97,7 @@ func init() {
 	rf.String("runtime-name", "", "Runtime display name (env: MULTICA_AGENT_RUNTIME_NAME)")
 	rf.Duration("poll-interval", 0, "Task poll interval (env: MULTICA_DAEMON_POLL_INTERVAL)")
 	rf.Duration("heartbeat-interval", 0, "Heartbeat interval (env: MULTICA_DAEMON_HEARTBEAT_INTERVAL)")
-	rf.Duration("agent-timeout", 0, "Per-task timeout (env: MULTICA_AGENT_TIMEOUT)")
+	rf.Duration("agent-timeout", 0, "Absolute per-task wall-clock cap; 0 = no cap, rely on the watchdogs (env: MULTICA_AGENT_TIMEOUT)")
 	rf.Duration("codex-semantic-inactivity-timeout", 0, "Codex semantic inactivity timeout (env: MULTICA_CODEX_SEMANTIC_INACTIVITY_TIMEOUT)")
 	rf.Int("max-concurrent-tasks", 0, "Max tasks running in parallel (env: MULTICA_DAEMON_MAX_CONCURRENT_TASKS)")
 	rf.Bool("no-auto-update", false, "Disable periodic CLI self-update (env: MULTICA_DAEMON_AUTO_UPDATE=false)")
@@ -284,7 +284,10 @@ func buildDaemonStartArgs(cmd *cobra.Command) []string {
 	if d, _ := cmd.Flags().GetDuration("heartbeat-interval"); d > 0 {
 		args = append(args, "--heartbeat-interval", d.String())
 	}
-	if d, _ := cmd.Flags().GetDuration("agent-timeout"); d > 0 {
+	// Forward agent-timeout when explicitly set, including an explicit 0
+	// (= no cap), so it can override an environment MULTICA_AGENT_TIMEOUT.
+	if cmd.Flags().Changed("agent-timeout") {
+		d, _ := cmd.Flags().GetDuration("agent-timeout")
 		args = append(args, "--agent-timeout", d.String())
 	}
 	if d, _ := cmd.Flags().GetDuration("codex-semantic-inactivity-timeout"); d > 0 {
@@ -336,8 +339,11 @@ func runDaemonForeground(cmd *cobra.Command) error {
 	if d, _ := cmd.Flags().GetDuration("heartbeat-interval"); d > 0 {
 		overrides.HeartbeatInterval = d
 	}
-	if d, _ := cmd.Flags().GetDuration("agent-timeout"); d > 0 {
-		overrides.AgentTimeout = d
+	// Distinguish "flag not passed" from an explicit `--agent-timeout 0` so a
+	// user can turn off an env-configured cap from the CLI.
+	if cmd.Flags().Changed("agent-timeout") {
+		d, _ := cmd.Flags().GetDuration("agent-timeout")
+		overrides.AgentTimeout = &d
 	}
 	if d, _ := cmd.Flags().GetDuration("codex-semantic-inactivity-timeout"); d > 0 {
 		overrides.CodexSemanticInactivityTimeout = d
diff --git a/server/cmd/server/runtime_sweeper.go b/server/cmd/server/runtime_sweeper.go
index 282b16977..87b4b17c4 100644
--- a/server/cmd/server/runtime_sweeper.go
+++ b/server/cmd/server/runtime_sweeper.go
@@ -36,8 +36,12 @@ const (
 	// The dispatched→running transition should be near-instant, so 5 minutes
 	// means something went wrong (e.g. StartTask API call failed silently).
 	dispatchTimeoutSeconds = 300.0
-	// runningTimeoutSeconds fails tasks stuck in 'running' beyond this.
-	// The default agent timeout is 2h, so 2.5h gives a generous buffer.
+	// runningTimeoutSeconds fails tasks stuck in 'running' beyond this. It is a
+	// coarse server-side backstop keyed on started_at (it does NOT look at task
+	// activity) — mainly for runs whose daemon died without reporting. The
+	// daemon itself decides stuck-vs-long-running by activity (idle/tool
+	// watchdog), so this only needs to sit generously above any realistic single
+	// run rather than track a per-run wall-clock cap (MUL-3064).
 	runningTimeoutSeconds = 9000.0
 	// queuedTTLSeconds expires tasks that have been sitting in 'queued'
 	// for longer than this without ever being claimed. This is the cleanup
@@ -46,9 +50,8 @@ const (
 	// tasks already on the queue when a runtime drops off (or that lost
 	// the race against a runtime that went offline mid-tick) need a
 	// time-bounded exit. 2 hours is conservatively above any reasonable
-	// "queued behind a long-running task" window for an online runtime
-	// (default agent timeout is 2h, sweeper interval is 30s) so we don't
-	// expire legitimately-pending work, while still draining the historical
+	// "queued behind a long-running task" window for an online runtime, so we
+	// don't expire legitimately-pending work, while still draining the historical
 	// 87k autopilot backlog within ~24h once enabled.
 	queuedTTLSeconds = 2 * 3600.0
 	// queuedExpireBatchSize caps how many queued rows a single sweeper tick
diff --git a/server/internal/daemon/config.go b/server/internal/daemon/config.go
index 495a49fd4..084d94292 100644
--- a/server/internal/daemon/config.go
+++ b/server/internal/daemon/config.go
@@ -15,23 +15,39 @@ import (
 )
 
 const (
-	DefaultServerURL                      = "ws://localhost:8080/ws"
-	DefaultPollInterval                   = 30 * time.Second
-	DefaultHeartbeatInterval              = 15 * time.Second
-	DefaultAgentTimeout                   = 2 * time.Hour
+	DefaultServerURL         = "ws://localhost:8080/ws"
+	DefaultPollInterval      = 30 * time.Second
+	DefaultHeartbeatInterval = 15 * time.Second
+	// DefaultAgentTimeout is the optional absolute wall-clock cap on a single
+	// agent run. 0 = no cap: a run is bounded only by the inactivity watchdogs
+	// (DefaultAgentIdleWatchdog / DefaultAgentToolWatchdog), so a session that keeps emitting events is
+	// never killed merely for running long (MUL-3064). Operators who want a
+	// hard ceiling for cost/resource control can set MULTICA_AGENT_TIMEOUT.
+	DefaultAgentTimeout                   = 0
 	DefaultCodexSemanticInactivityTimeout = 10 * time.Minute
 	// DefaultAgentIdleWatchdog is the per-task safety net that force-stops a
 	// run when the backend has emitted no message for this long AND its
 	// message queue is empty. Backends like Claude Code can hang indefinitely
 	// on a stuck child process (e.g. `docker ps` against a frozen dockerd),
-	// in which case `cmd.Wait()` never returns and the task sits at "running"
-	// for its full DefaultAgentTimeout (2 h). The previous 5 min default
+	// in which case `cmd.Wait()` never returns. With no wall-clock cap
+	// (DefaultAgentTimeout = 0) such a run would otherwise sit at "running"
+	// forever, so this watchdog is its sole liveness net. The previous 5 min default
 	// killed legitimate long assistant outputs (e.g. RFC-length writeups)
 	// where the model streams a single message for many minutes without any
 	// daemon-visible activity — see MUL-2300. 30 min keeps the safety net for
 	// truly stuck runs (dockerd hang) while leaving headroom for long writes.
 	// Set MULTICA_AGENT_IDLE_WATCHDOG=0 to disable.
-	DefaultAgentIdleWatchdog       = 30 * time.Minute
+	DefaultAgentIdleWatchdog = 30 * time.Minute
+	// DefaultAgentToolWatchdog bounds how long a single tool call may stay in
+	// flight (tool_use emitted, no tool_result and no other message) before the
+	// idle watchdog force-stops the run. The idle watchdog ignores its normal
+	// window while a tool is in flight, because a real build/install/test
+	// legitimately runs silently for many minutes — but with no wall-clock cap
+	// (DefaultAgentTimeout = 0) a backend that emits tool_use and never the
+	// matching tool_result would otherwise run forever. This is the backstop for
+	// that stuck-tool case (MUL-3064). Set MULTICA_AGENT_TOOL_WATCHDOG=0 to
+	// disable, in which case an in-flight tool never force-stops the run.
+	DefaultAgentToolWatchdog       = 2 * time.Hour
 	DefaultRuntimeName             = "Local Agent"
 	DefaultWorkspaceSyncInterval   = 30 * time.Second
 	DefaultHealthPort              = 19514
@@ -79,6 +95,7 @@ type Config struct {
 	AgentTimeout                   time.Duration
 	CodexSemanticInactivityTimeout time.Duration
 	AgentIdleWatchdog              time.Duration // force-stop a run when the backend goes silent this long with an empty queue (0 = disabled)
+	AgentToolWatchdog              time.Duration // force-stop a run when a single tool call stays in flight (silent) this long (0 = disabled); backstop for hung tools now that there is no wall-clock cap
 	ClaudeArgs                     []string
 	CodexArgs                      []string
 }
@@ -86,11 +103,13 @@ type Config struct {
 // Overrides allows CLI flags to override environment variables and defaults.
 // Zero values are ignored and the env/default value is used instead.
 type Overrides struct {
-	ServerURL                      string
-	WorkspacesRoot                 string
-	PollInterval                   time.Duration
-	HeartbeatInterval              time.Duration
-	AgentTimeout                   time.Duration
+	ServerURL         string
+	WorkspacesRoot    string
+	PollInterval      time.Duration
+	HeartbeatInterval time.Duration
+	// AgentTimeout is a pointer so an explicit `--agent-timeout 0` (no cap) is
+	// distinguishable from "flag not passed". nil = use env/default.
+	AgentTimeout                   *time.Duration
 	CodexSemanticInactivityTimeout time.Duration
 	MaxConcurrentTasks             int
 	DaemonID                       string
@@ -260,8 +279,8 @@ func LoadConfig(overrides Overrides) (Config, error) {
 	if err != nil {
 		return Config{}, err
 	}
-	if overrides.AgentTimeout > 0 {
-		agentTimeout = overrides.AgentTimeout
+	if overrides.AgentTimeout != nil {
+		agentTimeout = *overrides.AgentTimeout
 	}
 
 	codexSemanticInactivityTimeout, err := durationFromEnv("MULTICA_CODEX_SEMANTIC_INACTIVITY_TIMEOUT", DefaultCodexSemanticInactivityTimeout)
@@ -280,6 +299,13 @@ func LoadConfig(overrides Overrides) (Config, error) {
 		return Config{}, err
 	}
 
+	// MULTICA_AGENT_TOOL_WATCHDOG=0 disables the in-flight-tool backstop; any
+	// positive duration overrides DefaultAgentToolWatchdog.
+	agentToolWatchdog, err := durationFromEnv("MULTICA_AGENT_TOOL_WATCHDOG", DefaultAgentToolWatchdog)
+	if err != nil {
+		return Config{}, err
+	}
+
 	maxConcurrentTasks, err := intFromEnv("MULTICA_DAEMON_MAX_CONCURRENT_TASKS", DefaultMaxConcurrentTasks)
 	if err != nil {
 		return Config{}, err
@@ -428,6 +454,7 @@ func LoadConfig(overrides Overrides) (Config, error) {
 		AgentTimeout:                   agentTimeout,
 		CodexSemanticInactivityTimeout: codexSemanticInactivityTimeout,
 		AgentIdleWatchdog:              agentIdleWatchdog,
+		AgentToolWatchdog:              agentToolWatchdog,
 		ClaudeArgs:                     claudeArgs,
 		CodexArgs:                      codexArgs,
 	}, nil
diff --git a/server/internal/daemon/daemon.go b/server/internal/daemon/daemon.go
index b9f54ec6d..64b90f152 100644
--- a/server/internal/daemon/daemon.go
+++ b/server/internal/daemon/daemon.go
@@ -3087,15 +3087,21 @@ func (d *Daemon) executeAndDrain(ctx context.Context, backend agent.Backend, pro
 	}
 	taskLog.Debug("backend started, draining messages")
 
-	// Create an independent drain deadline so we don't block forever if the
-	// backend's internal timeout fails to produce a Result (e.g. scanner
-	// stuck on a hung stdout pipe). The extra 30 s gives the backend time
-	// to clean up after its own timeout fires.
-	drainTimeout := opts.Timeout + 30*time.Second
-	if opts.Timeout == 0 {
-		drainTimeout = 21 * time.Minute
+	// Bound the drain loop only when there is a wall-clock cap. With a positive
+	// opts.Timeout, give the drain a slightly longer deadline than the backend
+	// so it can still collect the backend's own timeout Result if the scanner
+	// is stuck on a hung stdout pipe (the extra 30 s covers cleanup after the
+	// backend's own deadline fires). With no cap (opts.Timeout <= 0) the
+	// inactivity watchdog is the only liveness net, so the drain must NOT
+	// impose its own deadline either — otherwise an actively streaming long run
+	// would be cut off here regardless of progress (MUL-3064).
+	var drainCtx context.Context
+	var drainCancel context.CancelFunc
+	if opts.Timeout > 0 {
+		drainCtx, drainCancel = context.WithTimeout(agentCtx, opts.Timeout+30*time.Second)
+	} else {
+		drainCtx, drainCancel = context.WithCancel(agentCtx)
 	}
-	drainCtx, drainCancel := context.WithTimeout(agentCtx, drainTimeout)
 	defer drainCancel()
 
 	var toolCount atomic.Int32
@@ -3110,12 +3116,18 @@ func (d *Daemon) executeAndDrain(ctx context.Context, backend agent.Backend, pro
 	// with a matching tool_result. A non-zero count means the agent is
 	// legitimately waiting on a tool (e.g. `npm install`, `docker build`)
 	// that may run far longer than the idle window without emitting any
-	// message — so the watchdog must not interpret that silence as a hang.
+	// message — so while a tool is in flight the watchdog applies the larger
+	// AgentToolWatchdog budget instead of treating that silence as a hang.
 	var inFlightTools atomic.Int32
 	var idleWatchdogFired atomic.Bool
+	// idleWatchdogThreshold records (as nanos) which silence budget actually
+	// tripped the watchdog — the idle window or the larger in-flight-tool
+	// window — so the failure message reports the real duration.
+	var idleWatchdogThreshold atomic.Int64
+	idleWatchdogThreshold.Store(int64(d.cfg.AgentIdleWatchdog))
 	idleWindow := d.cfg.AgentIdleWatchdog
 	if idleWindow > 0 {
-		go d.runIdleWatchdog(agentCtx, idleWindow, &lastActivityAt, &inFlightTools, &idleWatchdogFired, agentCancel, session.Messages, taskLog, taskID)
+		go d.runIdleWatchdog(agentCtx, idleWindow, d.cfg.AgentToolWatchdog, &lastActivityAt, &inFlightTools, &idleWatchdogFired, &idleWatchdogThreshold, agentCancel, session.Messages, taskLog, taskID)
 	}
 
 	go func() {
@@ -3302,7 +3314,7 @@ func (d *Daemon) executeAndDrain(ctx context.Context, backend agent.Backend, pro
 			// generic "agent_error" bucket the aborted path falls into.
 			result.Status = "idle_watchdog"
 			if result.Error == "" {
-				result.Error = idleWatchdogReason(idleWindow)
+				result.Error = idleWatchdogReason(time.Duration(idleWatchdogThreshold.Load()))
 			}
 		}
 		return result, toolCount.Load(), nil
@@ -3314,7 +3326,7 @@ func (d *Daemon) executeAndDrain(ctx context.Context, backend agent.Backend, pro
 		if idleWatchdogFired.Load() {
 			return agent.Result{
 				Status: "idle_watchdog",
-				Error:  idleWatchdogReason(idleWindow),
+				Error:  idleWatchdogReason(time.Duration(idleWatchdogThreshold.Load())),
 			}, toolCount.Load(), nil
 		}
 		// Distinguish external cancellation (e.g. server-initiated cancel
@@ -3343,24 +3355,28 @@ func idleWatchdogReason(window time.Duration) string {
 }
 
 // runIdleWatchdog ticks until either agentCtx is cancelled or the backend has
-// been silent for at least window with no in-flight tool call. On firing, it
-// sets fired and calls cancel, which propagates to the agent subprocess (via
-// the ctx passed to backend.Execute) and to drainCtx. The check requires:
+// been silent past the applicable budget. On firing, it records the tripped
+// threshold, sets fired, and calls cancel, which propagates to the agent
+// subprocess (via the ctx passed to backend.Execute) and to drainCtx. The
+// silence budget depends on whether a tool call is in flight:
 //
-//  1. inFlightTools == 0 — the backend has emitted a tool_use whose
-//     matching tool_result hasn't arrived yet, meaning a real tool (e.g.
-//     `npm install`, `docker build`) is legitimately running. Long tool
-//     calls produce no messages between use and result; killing here would
-//     yank the agent mid-build. AND
-//  2. time since lastActivityAt exceeds window — the drain loop is single
-//     reader, so a stale stamp means no message has actually arrived; AND
-//  3. session.Messages buffer is empty — defensive against a hypothetical
-//     drain stall where unprocessed messages would still imply progress.
+//  1. No tool in flight — a silent backend is a hang after `window`.
+//  2. A tool in flight (tool_use with no matching tool_result yet) — a real
+//     tool (e.g. `npm install`, `docker build`) legitimately runs silently for
+//     many minutes, so the larger `toolWindow` applies instead. toolWindow <= 0
+//     keeps the historical behavior of never force-stopping while a tool is in
+//     flight. Without this in-flight budget a backend that emits tool_use and
+//     never the matching tool_result would run forever now that there is no
+//     wall-clock cap (MUL-3064).
+//
+// In both cases the watchdog also requires the session.Messages buffer to be
+// empty — a buffered-but-undrained message means the drain loop is behind, not
+// the backend.
 //
 // Tick interval is window/2 (floored at 30 s in production, but the floor only
 // kicks in for windows >= 1 min so tests can pass tiny windows like 50 ms and
 // see the watchdog fire within a few ticks).
-func (d *Daemon) runIdleWatchdog(agentCtx context.Context, window time.Duration, lastActivityAt *atomic.Int64, inFlightTools *atomic.Int32, fired *atomic.Bool, cancel context.CancelFunc, messages <-chan agent.Message, taskLog *slog.Logger, taskID string) {
+func (d *Daemon) runIdleWatchdog(agentCtx context.Context, window, toolWindow time.Duration, lastActivityAt *atomic.Int64, inFlightTools *atomic.Int32, fired *atomic.Bool, firedThreshold *atomic.Int64, cancel context.CancelFunc, messages <-chan agent.Message, taskLog *slog.Logger, taskID string) {
 	interval := window / 2
 	if window >= time.Minute && interval < 30*time.Second {
 		interval = 30 * time.Second
@@ -3375,16 +3391,21 @@ func (d *Daemon) runIdleWatchdog(agentCtx context.Context, window time.Duration,
 		case <-agentCtx.Done():
 			return
 		case <-ticker.C:
-			// In-flight tool call: the agent has emitted tool_use and
-			// the corresponding tool_result hasn't landed yet. A long
-			// build/install/test can sit here silently for many minutes
-			// — that is forward progress, not a hang.
-			if inFlightTools.Load() > 0 {
-				continue
+			// Pick the silence budget. A tool in flight is expected to be
+			// silent (a long build/install/test emits nothing between
+			// tool_use and tool_result), so it gets the larger toolWindow;
+			// toolWindow <= 0 disables the in-flight bound entirely.
+			threshold := window
+			toolInFlight := inFlightTools.Load() > 0
+			if toolInFlight {
+				if toolWindow <= 0 {
+					continue
+				}
+				threshold = toolWindow
 			}
 			last := time.Unix(0, lastActivityAt.Load())
 			idleFor := time.Since(last)
-			if idleFor < window {
+			if idleFor < threshold {
 				continue
 			}
 			// A buffered-but-undrained message means the drain loop is
@@ -3396,8 +3417,10 @@ func (d *Daemon) runIdleWatchdog(agentCtx context.Context, window time.Duration,
 			taskLog.Warn("idle watchdog firing: no agent activity, force-stopping run",
 				"task", shortID(taskID),
 				"idle_for", idleFor.Round(time.Second).String(),
-				"threshold", window.String(),
+				"threshold", threshold.String(),
+				"tool_in_flight", toolInFlight,
 			)
+			firedThreshold.Store(int64(threshold))
 			fired.Store(true)
 			cancel()
 			return
diff --git a/server/internal/daemon/daemon_test.go b/server/internal/daemon/daemon_test.go
index 7f7044787..e3dcb7da9 100644
--- a/server/internal/daemon/daemon_test.go
+++ b/server/internal/daemon/daemon_test.go
@@ -1096,8 +1096,9 @@ func TestExecuteAndDrain_ContextCancelled_ReportsCancelled(t *testing.T) {
 
 // idleWatchdogBackend simulates the MUL-2225 hang: emit one message to mark
 // activity, then go silent forever. With a short AgentIdleWatchdog, the
-// watchdog should fire and short-circuit executeAndDrain instead of waiting
-// for the full drainTimeout (which is ~21 minutes by default).
+// watchdog should fire and short-circuit executeAndDrain. With no wall-clock
+// cap (opts.Timeout = 0) the drain loop imposes no deadline of its own, so the
+// idle watchdog is the only thing that ends this otherwise-forever-silent run.
 type idleWatchdogBackend struct {
 	emitOne bool // when true, emit one message before going silent; when false, never emit anything
 }
@@ -1285,6 +1286,45 @@ func TestExecuteAndDrain_IdleWatchdog_DoesNotFireDuringInFlightToolCall(t *testi
 	}
 }
 
+// stuckInFlightToolBackend models a hung tool: it emits a tool_use and then
+// goes silent forever — the matching tool_result never arrives, so inFlightTools
+// stays at 1 (e.g. a child process that never returns). With no wall-clock cap
+// (the MUL-3064 default), AgentToolWatchdog is the only thing that ends it.
+type stuckInFlightToolBackend struct{}
+
+func (stuckInFlightToolBackend) Execute(_ context.Context, _ string, _ agent.ExecOptions) (*agent.Session, error) {
+	msgCh := make(chan agent.Message, 2)
+	resCh := make(chan agent.Result)
+	msgCh <- agent.Message{Type: agent.MessageToolUse, Tool: "Bash", CallID: "c1"}
+	// Deliberately leave msgCh open, never emit tool_result, never write resCh.
+	return &agent.Session{Messages: msgCh, Result: resCh}, nil
+}
+
+func TestExecuteAndDrain_IdleWatchdog_FiresOnStuckInFlightTool(t *testing.T) {
+	t.Parallel()
+
+	d := newTestDaemon(t)
+	// The normal idle window would be skipped while a tool is in flight; the
+	// AgentToolWatchdog budget is what must fire here.
+	d.cfg.AgentIdleWatchdog = 50 * time.Millisecond
+	d.cfg.AgentToolWatchdog = 50 * time.Millisecond
+
+	ctx, cancel := context.WithCancel(context.Background())
+	t.Cleanup(cancel)
+
+	start := time.Now()
+	result, _, err := d.executeAndDrain(ctx, stuckInFlightToolBackend{}, "p", agent.ExecOptions{}, slog.Default(), "t-stuck-tool")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if result.Status != "idle_watchdog" {
+		t.Fatalf("expected status=idle_watchdog for a hung in-flight tool, got %q (err=%q)", result.Status, result.Error)
+	}
+	if elapsed := time.Since(start); elapsed > 2*time.Second {
+		t.Fatalf("tool watchdog took too long to fire: %s (window=%s)", elapsed, d.cfg.AgentToolWatchdog)
+	}
+}
+
 // tailIdleAfterToolBackend exercises the boundary case: a tool call completes,
 // and THEN the backend goes silent without ever finishing. After the
 // tool_result lands, in-flight count returns to zero and lastActivityAt is
diff --git a/server/pkg/agent/agent.go b/server/pkg/agent/agent.go
index 0f0daa8b7..1f34c5812 100644
--- a/server/pkg/agent/agent.go
+++ b/server/pkg/agent/agent.go
@@ -47,6 +47,19 @@ type ExecOptions struct {
 	ThinkingLevel string
 }
 
+// runContext derives the execution context for an agent subprocess from the
+// configured per-run timeout. A positive timeout imposes a hard wall-clock
+// deadline; a zero (or negative) timeout imposes NO deadline, leaving liveness
+// entirely to the daemon's inactivity watchdog so a session that keeps emitting
+// events is never killed merely for running long (MUL-3064). The caller owns
+// the returned CancelFunc and must call it to release resources.
+func runContext(ctx context.Context, timeout time.Duration) (context.Context, context.CancelFunc) {
+	if timeout > 0 {
+		return context.WithTimeout(ctx, timeout)
+	}
+	return context.WithCancel(ctx)
+}
+
 // Session represents a running agent execution.
 type Session struct {
 	// Messages streams events as the agent works. The channel is closed
diff --git a/server/pkg/agent/agent_test.go b/server/pkg/agent/agent_test.go
index 32895ed76..a237d6174 100644
--- a/server/pkg/agent/agent_test.go
+++ b/server/pkg/agent/agent_test.go
@@ -3,6 +3,7 @@ package agent
 import (
 	"context"
 	"testing"
+	"time"
 )
 
 func TestNewReturnsClaudeBackend(t *testing.T) {
@@ -98,3 +99,37 @@ func TestLaunchHeaderReturnsEmptyForUnknownType(t *testing.T) {
 		t.Errorf("expected empty header for unknown type, got %q", header)
 	}
 }
+
+func TestRunContextZeroTimeoutHasNoDeadline(t *testing.T) {
+	t.Parallel()
+	// A zero (or negative) timeout must NOT impose a wall-clock deadline:
+	// liveness is delegated to the daemon's inactivity watchdog so an actively
+	// streaming long-running session is never killed merely for running long
+	// (MUL-3064).
+	for _, d := range []time.Duration{0, -time.Second} {
+		ctx, cancel := runContext(context.Background(), d)
+		if _, ok := ctx.Deadline(); ok {
+			cancel()
+			t.Fatalf("runContext(%s) imposed a deadline; want none", d)
+		}
+		cancel()
+		if ctx.Err() == nil {
+			t.Fatalf("runContext(%s): context should be cancelled after cancel()", d)
+		}
+	}
+}
+
+func TestRunContextPositiveTimeoutHasDeadline(t *testing.T) {
+	t.Parallel()
+	// A positive timeout keeps the hard wall-clock deadline (the opt-in
+	// absolute cap operators can still set via MULTICA_AGENT_TIMEOUT).
+	ctx, cancel := runContext(context.Background(), time.Hour)
+	defer cancel()
+	deadline, ok := ctx.Deadline()
+	if !ok {
+		t.Fatal("runContext(1h) should impose a deadline")
+	}
+	if remaining := time.Until(deadline); remaining <= 0 || remaining > time.Hour+time.Minute {
+		t.Fatalf("unexpected deadline remaining: %s", remaining)
+	}
+}
diff --git a/server/pkg/agent/antigravity.go b/server/pkg/agent/antigravity.go
index 9f1d7457b..3197bda97 100644
--- a/server/pkg/agent/antigravity.go
+++ b/server/pkg/agent/antigravity.go
@@ -39,10 +39,7 @@ func (b *antigravityBackend) Execute(ctx context.Context, prompt string, opts Ex
 	}
 
 	timeout := opts.Timeout
-	if timeout == 0 {
-		timeout = 20 * time.Minute
-	}
-	runCtx, cancel := context.WithTimeout(ctx, timeout)
+	runCtx, cancel := runContext(ctx, timeout)
 
 	logFile, err := os.CreateTemp("", "multica-agy-log-*.log")
 	if err != nil {
@@ -216,9 +213,16 @@ func buildAntigravityArgs(prompt, logPath string, timeout time.Duration, opts Ex
 	args := []string{
 		"-p", prompt,
 		"--dangerously-skip-permissions",
-		"--print-timeout", antigravityFormatTimeout(timeout),
-		"--log-file", logPath,
 	}
+	// Only pass --print-timeout when a positive wall-clock cap is configured.
+	// timeout <= 0 means "no cap" (MUL-3064): agy then runs without its own
+	// print-timeout guillotine, matching every other backend's runContext
+	// semantics. Passing antigravityFormatTimeout(0) would clamp to 1s and kill
+	// the run almost immediately — the opposite of "no cap".
+	if timeout > 0 {
+		args = append(args, "--print-timeout", antigravityFormatTimeout(timeout))
+	}
+	args = append(args, "--log-file", logPath)
 	if opts.ResumeSessionID != "" {
 		args = append(args, "--conversation", opts.ResumeSessionID)
 	}
diff --git a/server/pkg/agent/antigravity_test.go b/server/pkg/agent/antigravity_test.go
index 5144d9813..8877d063b 100644
--- a/server/pkg/agent/antigravity_test.go
+++ b/server/pkg/agent/antigravity_test.go
@@ -38,6 +38,34 @@ func TestBuildAntigravityArgsBasic(t *testing.T) {
 	}
 }
 
+func TestBuildAntigravityArgsNoTimeoutOmitsPrintTimeout(t *testing.T) {
+	t.Parallel()
+
+	// timeout <= 0 means "no wall-clock cap" (MUL-3064): agy must be launched
+	// WITHOUT --print-timeout, otherwise antigravityFormatTimeout(0) clamps to
+	// 1s and the run is killed almost immediately — the opposite of "no cap".
+	args := buildAntigravityArgs(
+		"hello",
+		"/tmp/agy.log",
+		0,
+		ExecOptions{Cwd: "/work"},
+		quietAntigravityLogger(),
+	)
+
+	want := []string{
+		"-p", "hello",
+		"--dangerously-skip-permissions",
+		"--log-file", "/tmp/agy.log",
+		"--add-dir", "/work",
+	}
+	if !slices.Equal(args, want) {
+		t.Fatalf("buildAntigravityArgs(timeout=0) mismatch\n got: %v\nwant: %v", args, want)
+	}
+	if slices.Contains(args, "--print-timeout") {
+		t.Fatalf("--print-timeout must be omitted when timeout <= 0; got %v", args)
+	}
+}
+
 func TestBuildAntigravityArgsResume(t *testing.T) {
 	t.Parallel()
 
diff --git a/server/pkg/agent/claude.go b/server/pkg/agent/claude.go
index b1dea4be0..033696a2b 100644
--- a/server/pkg/agent/claude.go
+++ b/server/pkg/agent/claude.go
@@ -30,10 +30,7 @@ func (b *claudeBackend) Execute(ctx context.Context, prompt string, opts ExecOpt
 	}
 
 	timeout := opts.Timeout
-	if timeout == 0 {
-		timeout = 20 * time.Minute
-	}
-	runCtx, cancel := context.WithTimeout(ctx, timeout)
+	runCtx, cancel := runContext(ctx, timeout)
 
 	args := buildClaudeArgs(opts, b.cfg.Logger)
 
diff --git a/server/pkg/agent/codex.go b/server/pkg/agent/codex.go
index 0e2ed833f..4443ea732 100644
--- a/server/pkg/agent/codex.go
+++ b/server/pkg/agent/codex.go
@@ -499,14 +499,11 @@ func (b *codexBackend) Execute(ctx context.Context, prompt string, opts ExecOpti
 	}
 
 	timeout := opts.Timeout
-	if timeout == 0 {
-		timeout = 20 * time.Minute
-	}
 	semanticInactivityTimeout := opts.SemanticInactivityTimeout
 	if semanticInactivityTimeout == 0 {
 		semanticInactivityTimeout = defaultCodexSemanticInactivityTimeout
 	}
-	runCtx, cancel := context.WithTimeout(ctx, timeout)
+	runCtx, cancel := runContext(ctx, timeout)
 
 	// Materialise the agent's MCP config into the per-task
 	// `$CODEX_HOME/config.toml`. Argv would be the simpler path, but
diff --git a/server/pkg/agent/copilot.go b/server/pkg/agent/copilot.go
index edf266fd6..23715fa09 100644
--- a/server/pkg/agent/copilot.go
+++ b/server/pkg/agent/copilot.go
@@ -203,10 +203,7 @@ func (b *copilotBackend) Execute(ctx context.Context, prompt string, opts ExecOp
 	}
 
 	timeout := opts.Timeout
-	if timeout == 0 {
-		timeout = 20 * time.Minute
-	}
-	runCtx, cancel := context.WithTimeout(ctx, timeout)
+	runCtx, cancel := runContext(ctx, timeout)
 
 	args := buildCopilotArgs(prompt, opts, b.cfg.Logger)
 	argv0, cmdArgs := chooseCopilotInvocation(execName, lookedUp, args, b.cfg.Logger)
diff --git a/server/pkg/agent/cursor.go b/server/pkg/agent/cursor.go
index f2bfa26e3..b6cebca69 100644
--- a/server/pkg/agent/cursor.go
+++ b/server/pkg/agent/cursor.go
@@ -31,10 +31,7 @@ func (b *cursorBackend) Execute(ctx context.Context, prompt string, opts ExecOpt
 	}
 
 	timeout := opts.Timeout
-	if timeout == 0 {
-		timeout = 20 * time.Minute
-	}
-	runCtx, cancel := context.WithTimeout(ctx, timeout)
+	runCtx, cancel := runContext(ctx, timeout)
 
 	args := buildCursorArgs(prompt, opts, b.cfg.Logger)
 	argv0, cmdArgs := chooseCursorInvocation(execName, lookedUp, args, b.cfg.Logger)
diff --git a/server/pkg/agent/gemini.go b/server/pkg/agent/gemini.go
index b0a6571fb..4e48de6af 100644
--- a/server/pkg/agent/gemini.go
+++ b/server/pkg/agent/gemini.go
@@ -27,10 +27,7 @@ func (b *geminiBackend) Execute(ctx context.Context, prompt string, opts ExecOpt
 	}
 
 	timeout := opts.Timeout
-	if timeout == 0 {
-		timeout = 20 * time.Minute
-	}
-	runCtx, cancel := context.WithTimeout(ctx, timeout)
+	runCtx, cancel := runContext(ctx, timeout)
 
 	args := buildGeminiArgs(prompt, opts, b.cfg.Logger)
 
diff --git a/server/pkg/agent/hermes.go b/server/pkg/agent/hermes.go
index f5a4eb927..ad03246a4 100644
--- a/server/pkg/agent/hermes.go
+++ b/server/pkg/agent/hermes.go
@@ -55,10 +55,7 @@ func (b *hermesBackend) Execute(ctx context.Context, prompt string, opts ExecOpt
 	}
 
 	timeout := opts.Timeout
-	if timeout == 0 {
-		timeout = 20 * time.Minute
-	}
-	runCtx, cancel := context.WithTimeout(ctx, timeout)
+	runCtx, cancel := runContext(ctx, timeout)
 
 	hermesArgs := append([]string{"acp"}, filterCustomArgs(opts.CustomArgs, hermesBlockedArgs, b.cfg.Logger)...)
 	cmd := exec.CommandContext(runCtx, execPath, hermesArgs...)
diff --git a/server/pkg/agent/kimi.go b/server/pkg/agent/kimi.go
index 9f50e3a24..896b276e7 100644
--- a/server/pkg/agent/kimi.go
+++ b/server/pkg/agent/kimi.go
@@ -49,10 +49,7 @@ func (b *kimiBackend) Execute(ctx context.Context, prompt string, opts ExecOptio
 	}
 
 	timeout := opts.Timeout
-	if timeout == 0 {
-		timeout = 20 * time.Minute
-	}
-	runCtx, cancel := context.WithTimeout(ctx, timeout)
+	runCtx, cancel := runContext(ctx, timeout)
 
 	// `kimi acp` ignores --yolo / --auto-approve (they're flags on the
 	// root `kimi` command, not on the `acp` subcommand). Instead, the
diff --git a/server/pkg/agent/kiro.go b/server/pkg/agent/kiro.go
index 7af230c47..d85f2fea2 100644
--- a/server/pkg/agent/kiro.go
+++ b/server/pkg/agent/kiro.go
@@ -54,10 +54,7 @@ func (b *kiroBackend) Execute(ctx context.Context, prompt string, opts ExecOptio
 	}
 
 	timeout := opts.Timeout
-	if timeout == 0 {
-		timeout = 20 * time.Minute
-	}
-	runCtx, cancel := context.WithTimeout(ctx, timeout)
+	runCtx, cancel := runContext(ctx, timeout)
 
 	kiroArgs := append([]string{"acp", "--trust-all-tools"}, filterCustomArgs(opts.CustomArgs, kiroBlockedArgs, b.cfg.Logger)...)
 	cmd := exec.CommandContext(runCtx, execPath, kiroArgs...)
diff --git a/server/pkg/agent/openclaw.go b/server/pkg/agent/openclaw.go
index 92fe5ec84..1f5ce366a 100644
--- a/server/pkg/agent/openclaw.go
+++ b/server/pkg/agent/openclaw.go
@@ -66,10 +66,7 @@ func (b *openclawBackend) Execute(ctx context.Context, prompt string, opts ExecO
 	}
 
 	timeout := opts.Timeout
-	if timeout == 0 {
-		timeout = 20 * time.Minute
-	}
-	runCtx, cancel := context.WithTimeout(ctx, timeout)
+	runCtx, cancel := runContext(ctx, timeout)
 
 	sessionID := opts.ResumeSessionID
 	if sessionID == "" {
diff --git a/server/pkg/agent/opencode.go b/server/pkg/agent/opencode.go
index e9c758b82..1e6868964 100644
--- a/server/pkg/agent/opencode.go
+++ b/server/pkg/agent/opencode.go
@@ -47,10 +47,7 @@ func (b *opencodeBackend) Execute(ctx context.Context, prompt string, opts ExecO
 	execPath = resolved
 
 	timeout := opts.Timeout
-	if timeout == 0 {
-		timeout = 20 * time.Minute
-	}
-	runCtx, cancel := context.WithTimeout(ctx, timeout)
+	runCtx, cancel := runContext(ctx, timeout)
 
 	args := []string{"run", "--format", "json", "--dangerously-skip-permissions"}
 	// Anchor OpenCode's project discovery (AGENTS.md walk-up + .opencode/skills/
diff --git a/server/pkg/agent/pi.go b/server/pkg/agent/pi.go
index da8b02d00..93078585d 100644
--- a/server/pkg/agent/pi.go
+++ b/server/pkg/agent/pi.go
@@ -184,9 +184,6 @@ func (b *piBackend) Execute(ctx context.Context, prompt string, opts ExecOptions
 	}
 
 	timeout := opts.Timeout
-	if timeout == 0 {
-		timeout = 20 * time.Minute
-	}
 
 	// Pi's --session flag expects a file path where events are appended.
 	// The path doubles as our opaque session identifier: we return it as
@@ -203,7 +200,7 @@ func (b *piBackend) Execute(ctx context.Context, prompt string, opts ExecOptions
 		return nil, fmt.Errorf("pi session file: %w", err)
 	}
 
-	runCtx, cancel := context.WithTimeout(ctx, timeout)
+	runCtx, cancel := runContext(ctx, timeout)
 
 	args := buildPiArgs(prompt, sessionPath, opts, b.cfg.Logger)
 	argv0, cmdArgs := choosePiInvocation(execName, lookedUp, args, b.cfg.Logger)