diff --git a/crates/app-tauri/src/state.rs b/crates/app-tauri/src/state.rs
index 0363493..51754ca 100644
--- a/crates/app-tauri/src/state.rs
+++ b/crates/app-tauri/src/state.rs
@@ -41,12 +41,11 @@ use application::{
 use async_trait::async_trait;
 use domain::ports::{
     AgentContextStore, AgentRuntime, AgentSession, AgentSessionFactory, AgentWakePort,
-    BackgroundTaskPortError, BackgroundTaskRunner, BackgroundTaskStore,
-    Clock, Embedder, EmbedderEnvInspector,
-    EmbedderProfileStore, EmbedderPromptStore, EventBus, FileSystem, GitPort, IdGenerator,
-    IssueNumberAllocator, IssueStore, MemoryRecall, MemoryStore, PermissionStore, ProcessSpawner,
-    ProfileStore, ProjectStore, PtyPort, ScheduledTask, Scheduler, SkillStore, TemplateStore,
-    WakeError, WakeReason,
+    BackgroundTaskPortError, BackgroundTaskRunner, BackgroundTaskStore, Clock, Embedder,
+    EmbedderEnvInspector, EmbedderProfileStore, EmbedderPromptStore, EventBus, FileSystem, GitPort,
+    IdGenerator, IssueNumberAllocator, IssueStore, MemoryRecall, MemoryStore, PermissionStore,
+    ProcessSpawner, ProfileStore, ProjectStore, PtyPort, ScheduledTask, Scheduler, SkillStore,
+    TemplateStore, WakeError, WakeReason,
 };
 use domain::profile::{
     AgentProfile, ContextInjection, McpConfigStrategy, McpTransport, StructuredAdapter,
@@ -61,9 +60,9 @@ use serde_json::{json, Map, Value};
 use uuid::Uuid;
 
 use infrastructure::{
-    AdaptiveMemoryRecall, BackgroundCompletionSink, BackgroundTaskReadyToDeliver,
-    ClaudePermissionProjector, ClaudeTranscriptInspector, CliAgentRuntime,
-    CodexPermissionProjector, CommandBackgroundRunner, embedder_from_profile, EmbedderEnvProbe,
+    embedder_from_profile, AdaptiveMemoryRecall, BackgroundCompletionSink,
+    BackgroundTaskReadyToDeliver, ClaudePermissionProjector, ClaudeTranscriptInspector,
+    CliAgentRuntime, CodexPermissionProjector, CommandBackgroundRunner, EmbedderEnvProbe,
     FsBackgroundTaskStore, FsConversationLog, FsEmbedderProfileStore, FsEmbedderPromptStore,
     FsHandoffStore, FsIssueNumberAllocator, FsIssueStore, FsLiveStateStore, FsMemoryStore,
     FsOrchestratorWatcher, FsPermissionStore, FsProfileStore, FsProjectStore,
@@ -1992,7 +1991,10 @@ impl AppState {
             .with_background_tasks(
                 Arc::clone(&background_tasks_port),
                 Arc::clone(&clock) as Arc<dyn Clock>,
-            ),
+            )
+            // Producteur B8 côté agent MCP : `idea_run_in_background` passe par le
+            // même use case que la commande Tauri, sans aller-retour frontend.
+            .with_spawn_background_command(Arc::clone(&spawn_background_command)),
         );
 
         let stop_live_agent = Arc::new(
@@ -4104,6 +4106,7 @@ mod mcp_serve_peer_tests {
         for expected in [
             "idea_list_agents",
             "idea_ask_agent",
+            "idea_run_in_background",
             "idea_launch_agent",
             "idea_stop_agent",
             "idea_update_context",
@@ -4140,8 +4143,8 @@ mod mcp_serve_peer_tests {
         assert!(!names.contains(&"idea_reply"));
         assert_eq!(
             tools.len(),
-            23,
-            "exactly the twenty-three exposed idea_* tools; got {names:?}"
+            24,
+            "exactly the twenty-four exposed idea_* tools; got {names:?}"
         );
 
         drop(client); // EOF ⇒ serve loop ends
diff --git a/crates/application/src/orchestrator/service.rs b/crates/application/src/orchestrator/service.rs
index 3b3a811..619211b 100644
--- a/crates/application/src/orchestrator/service.rs
+++ b/crates/application/src/orchestrator/service.rs
@@ -14,6 +14,7 @@
 //! infrastructure adapter's job. That keeps this fully unit-testable with fakes.
 
 use std::collections::HashMap;
+use std::path::{Component, Path, PathBuf};
 use std::sync::{Arc, Mutex as StdMutex};
 use std::time::{Duration, Instant};
 
@@ -39,6 +40,7 @@ use crate::agent::{
     ListAgents, ListAgentsInput, McpRuntime, ReattachDecision, UpdateAgentContext,
     UpdateAgentContextInput, CODEX_SUBMIT_DELAY_MS,
 };
+use crate::background::{SpawnBackgroundCommand, SpawnBackgroundCommandInput};
 use crate::error::AppError;
 use crate::orchestrator::rendezvous::{run_inactivity_watchdog, WatchdogOutcome};
 use crate::orchestrator::{
@@ -89,6 +91,55 @@ fn bound_task_text(value: &str, max_bytes: usize) -> String {
     value[..end].to_owned()
 }
 
+fn resolve_background_cwd(
+    project_root: &ProjectPath,
+    cwd: Option<String>,
+) -> Result<ProjectPath, AppError> {
+    let root = Path::new(project_root.as_str());
+    let raw = cwd.as_deref().map(str::trim).filter(|s| !s.is_empty());
+    let candidate = match raw {
+        None => root.to_path_buf(),
+        Some(value) => {
+            let path = Path::new(value);
+            if path.is_absolute() {
+                path.to_path_buf()
+            } else {
+                root.join(path)
+            }
+        }
+    };
+    let normalized = normalize_path_no_parent(&candidate)?;
+    if !normalized.starts_with(root) {
+        return Err(AppError::Invalid(
+            "background task cwd must stay under the project root".to_owned(),
+        ));
+    }
+    let Some(path) = normalized.to_str() else {
+        return Err(AppError::Invalid(
+            "background task cwd is not valid UTF-8".to_owned(),
+        ));
+    };
+    ProjectPath::new(path).map_err(|_| AppError::Invalid("invalid background task cwd".to_owned()))
+}
+
+fn normalize_path_no_parent(path: &Path) -> Result<PathBuf, AppError> {
+    let mut out = PathBuf::new();
+    for component in path.components() {
+        match component {
+            Component::Prefix(prefix) => out.push(prefix.as_os_str()),
+            Component::RootDir => out.push(component.as_os_str()),
+            Component::CurDir => {}
+            Component::Normal(part) => out.push(part),
+            Component::ParentDir => {
+                return Err(AppError::Invalid(
+                    "background task cwd must not contain `..`".to_owned(),
+                ))
+            }
+        }
+    }
+    Ok(out)
+}
+
 /// Bound on the synchronous inter-agent rendezvous (`agent.message` → `AskAgent`).
 ///
 /// A target agent's turn can be long (reasoning + tool use), so the cap is
@@ -433,6 +484,9 @@ pub struct OrchestratorService {
     /// `idea_ask_agent` comme [`BackgroundTaskKind::HeadlessRendezvous`]. `None` ⇒
     /// comportement historique sans persistance de tâche (call sites non câblés).
     background_tasks: Option<Arc<dyn BackgroundTaskStore>>,
+    /// Use case B8 qui produit une tâche de fond command-backed depuis la surface
+    /// agent MCP `idea_run_in_background`. `None` ⇒ outil non configuré.
+    spawn_background_command: Option<Arc<SpawnBackgroundCommand>>,
 }
 
 /// Bundle des quatre use cases C7 sous [`domain::fileguard::FileGuard`], injectés
@@ -504,9 +558,17 @@ impl OrchestratorService {
             ask_liveness_probe: None,
             ask_ceiling: ASK_AGENT_CEILING,
             background_tasks: None,
+            spawn_background_command: None,
         }
     }
 
+    /// Branche le producteur B8 command-backed pour `idea_run_in_background`.
+    #[must_use]
+    pub fn with_spawn_background_command(mut self, spawn: Arc<SpawnBackgroundCommand>) -> Self {
+        self.spawn_background_command = Some(spawn);
+        self
+    }
+
     /// Branche le store des tâches de fond pour tracer les rendez-vous inter-agents
     /// comme [`BackgroundTaskKind::HeadlessRendezvous`] (B6).
     ///
@@ -1096,9 +1158,70 @@ impl OrchestratorService {
                 )
                 .await
             }
+            OrchestratorCommand::RunInBackground {
+                owner,
+                label,
+                command,
+                args,
+                cwd,
+                deadline_ms,
+            } => {
+                self.run_in_background(project, owner, label, command, args, cwd, deadline_ms)
+                    .await
+            }
         }
     }
 
+    async fn run_in_background(
+        &self,
+        project: &Project,
+        owner: AgentId,
+        label: String,
+        command: String,
+        args: Vec<String>,
+        cwd: Option<String>,
+        deadline_ms: Option<u64>,
+    ) -> Result<OrchestratorOutcome, AppError> {
+        let spawn = self.spawn_background_command.as_ref().ok_or_else(|| {
+            AppError::Invalid("background command runner is not configured".to_owned())
+        })?;
+        let cwd = resolve_background_cwd(&project.root, cwd)?;
+        let output = spawn
+            .execute(SpawnBackgroundCommandInput {
+                project_id: project.id,
+                owner_agent_id: owner,
+                label,
+                command: domain::ports::SpawnSpec {
+                    command,
+                    args,
+                    cwd,
+                    env: Vec::new(),
+                    context_plan: None,
+                    sandbox: None,
+                },
+                wake_policy: BackgroundTaskWakePolicy::WakeOwner,
+                deadline_ms,
+            })
+            .await?;
+        let state = match output.task.state {
+            BackgroundTaskState::Queued => "Queued",
+            BackgroundTaskState::Running => "Running",
+            BackgroundTaskState::Waiting => "Waiting",
+            BackgroundTaskState::Completed => "Completed",
+            BackgroundTaskState::Failed => "Failed",
+            BackgroundTaskState::Cancelled => "Cancelled",
+            BackgroundTaskState::Expired => "Expired",
+        };
+        Ok(OrchestratorOutcome {
+            detail: serde_json::json!({
+                "taskId": output.task.id.to_string(),
+                "state": state,
+            })
+            .to_string(),
+            reply: None,
+        })
+    }
+
     /// Returns the injected C7 use cases, or a typed error when unwired.
     fn require_context_guard(&self) -> Result<&ContextGuardUseCases, AppError> {
         self.context_guard.as_deref().ok_or_else(|| {
diff --git a/crates/application/tests/orchestrator_service.rs b/crates/application/tests/orchestrator_service.rs
index 6631175..841a1ee 100644
--- a/crates/application/tests/orchestrator_service.rs
+++ b/crates/application/tests/orchestrator_service.rs
@@ -21,10 +21,11 @@ use domain::ids::SkillId;
 use domain::ids::{AgentId, NodeId, ProfileId, ProjectId};
 use domain::markdown::MarkdownDoc;
 use domain::ports::{
-    AgentContextStore, AgentRuntime, ContextInjectionPlan, DirEntry, EventBus, EventStream,
-    ExitStatus, FileSystem, FsError, IdGenerator, MemoryError, MemoryStore, OutputStream,
-    PreparedContext, ProfileStore, PtyError, PtyHandle, PtyPort, RemotePath, RuntimeError,
-    SessionPlan, SkillStore, SpawnSpec, StoreError,
+    AgentContextStore, AgentRuntime, BackgroundCompletionStream, BackgroundTaskHandle,
+    BackgroundTaskPortError, BackgroundTaskRunner, BackgroundTaskSpec, BackgroundTaskStore,
+    ContextInjectionPlan, DirEntry, EventBus, EventStream, ExitStatus, FileSystem, FsError,
+    IdGenerator, MemoryError, MemoryStore, OutputStream, PreparedContext, ProfileStore, PtyError,
+    PtyHandle, PtyPort, RemotePath, RuntimeError, SessionPlan, SkillStore, SpawnSpec, StoreError,
 };
 use domain::profile::{
     AgentProfile, ContextInjection, McpCapability, McpConfigStrategy, McpTransport,
@@ -34,14 +35,17 @@ use domain::project::{Project, ProjectPath};
 use domain::remote::RemoteRef;
 use domain::skill::{Skill, SkillScope};
 use domain::terminal::{SessionKind, TerminalSession};
+use domain::{
+    BackgroundTask, BackgroundTaskState, BackgroundTaskWakePolicy, OrchestratorCommand,
+    OrchestratorRequest, PtySize, SessionId, TaskId,
+};
 use domain::{Memory, MemoryIndexEntry, MemoryLink, MemorySlug};
-use domain::{OrchestratorCommand, OrchestratorRequest, PtySize, SessionId};
 use uuid::Uuid;
 
 use application::{
     CloseTerminal, CreateAgentFromScratch, CreateSkill, GetLiveStateLean, HarvestMemoryFromTurn,
     LaunchAgent, ListAgents, LiveStateProvider, LiveStateReadProvider, OrchestratorService,
-    TerminalSessions, UpdateAgentContext, UpdateLiveState,
+    SpawnBackgroundCommand, TerminalSessions, UpdateAgentContext, UpdateLiveState,
 };
 use domain::live_state::{LiveEntry, LiveState, WorkStatus};
 use domain::ports::LiveStateStore;
@@ -370,6 +374,104 @@ impl PtyPort for FakePty {
     }
 }
 
+#[derive(Clone, Default)]
+struct RecordingBackgroundStore {
+    tasks: Arc<Mutex<HashMap<TaskId, BackgroundTask>>>,
+}
+impl RecordingBackgroundStore {
+    fn task(&self, id: TaskId) -> Option<BackgroundTask> {
+        self.tasks.lock().unwrap().get(&id).cloned()
+    }
+}
+#[async_trait]
+impl BackgroundTaskStore for RecordingBackgroundStore {
+    async fn create(&self, task: &BackgroundTask) -> Result<(), BackgroundTaskPortError> {
+        let mut tasks = self.tasks.lock().unwrap();
+        if tasks.contains_key(&task.id) {
+            return Err(BackgroundTaskPortError::AlreadyExists);
+        }
+        tasks.insert(task.id, task.clone());
+        Ok(())
+    }
+
+    async fn get(&self, id: TaskId) -> Result<Option<BackgroundTask>, BackgroundTaskPortError> {
+        Ok(self.task(id))
+    }
+
+    async fn save(&self, task: &BackgroundTask) -> Result<(), BackgroundTaskPortError> {
+        self.tasks.lock().unwrap().insert(task.id, task.clone());
+        Ok(())
+    }
+
+    async fn list_open_for_agent(
+        &self,
+        agent_id: AgentId,
+    ) -> Result<Vec<BackgroundTask>, BackgroundTaskPortError> {
+        Ok(self
+            .tasks
+            .lock()
+            .unwrap()
+            .values()
+            .filter(|task| task.owner_agent_id == agent_id && !task.is_terminal())
+            .cloned()
+            .collect())
+    }
+
+    async fn list_undelivered_completions(
+        &self,
+    ) -> Result<Vec<BackgroundTask>, BackgroundTaskPortError> {
+        Ok(self
+            .tasks
+            .lock()
+            .unwrap()
+            .values()
+            .filter(|task| task.has_pending_completion_delivery())
+            .cloned()
+            .collect())
+    }
+
+    async fn mark_completion_delivered(
+        &self,
+        task_id: TaskId,
+    ) -> Result<(), BackgroundTaskPortError> {
+        let task = self
+            .task(task_id)
+            .ok_or(BackgroundTaskPortError::NotFound)?
+            .mark_completion_delivered()
+            .map_err(|err| BackgroundTaskPortError::Invalid(err.to_string()))?;
+        self.save(&task).await
+    }
+}
+
+#[derive(Clone, Default)]
+struct RecordingBackgroundRunner {
+    specs: Arc<Mutex<Vec<BackgroundTaskSpec>>>,
+}
+impl RecordingBackgroundRunner {
+    fn specs(&self) -> Vec<BackgroundTaskSpec> {
+        self.specs.lock().unwrap().clone()
+    }
+}
+#[async_trait]
+impl BackgroundTaskRunner for RecordingBackgroundRunner {
+    async fn spawn(
+        &self,
+        spec: BackgroundTaskSpec,
+    ) -> Result<BackgroundTaskHandle, BackgroundTaskPortError> {
+        let task_id = spec.task_id;
+        self.specs.lock().unwrap().push(spec);
+        Ok(BackgroundTaskHandle { task_id })
+    }
+
+    async fn cancel(&self, _task_id: TaskId) -> Result<(), BackgroundTaskPortError> {
+        Ok(())
+    }
+
+    fn subscribe_completions(&self) -> BackgroundCompletionStream {
+        Box::new(std::iter::empty())
+    }
+}
+
 #[derive(Default, Clone)]
 struct SpyBus(Arc<Mutex<Vec<DomainEvent>>>);
 impl SpyBus {
@@ -683,6 +785,71 @@ async fn spawn_unknown_agent_creates_then_launches() {
     assert!(launched, "AgentLaunched must be published");
 }
 
+#[tokio::test]
+async fn run_in_background_dispatch_creates_running_command_for_requester() {
+    let fx = fixture(FakeContexts::new());
+    let store = Arc::new(RecordingBackgroundStore::default());
+    let runner = Arc::new(RecordingBackgroundRunner::default());
+    let spawn = Arc::new(SpawnBackgroundCommand::new(
+        Arc::clone(&store) as Arc<dyn BackgroundTaskStore>,
+        Arc::clone(&runner) as Arc<dyn BackgroundTaskRunner>,
+        Arc::new(FixedMillisClock(42)) as Arc<dyn domain::ports::Clock>,
+        Arc::new(SeqIds::new()) as Arc<dyn IdGenerator>,
+    ));
+    let service = fx.service.with_spawn_background_command(spawn);
+    let owner = aid(77);
+
+    let out = service
+        .dispatch(
+            &project(),
+            OrchestratorCommand::RunInBackground {
+                owner,
+                label: "B8 T1".to_owned(),
+                command: "bash".to_owned(),
+                args: vec![
+                    "-lc".to_owned(),
+                    "sleep 45 && echo DONE_MARKER_DEVBACKEND_B8_T1".to_owned(),
+                ],
+                cwd: Some("crates".to_owned()),
+                deadline_ms: None,
+            },
+        )
+        .await
+        .expect("dispatch ok");
+
+    let payload: serde_json::Value = serde_json::from_str(&out.detail).unwrap();
+    assert_eq!(payload["state"], "Running");
+    let task_id =
+        TaskId::from_uuid(uuid::Uuid::parse_str(payload["taskId"].as_str().unwrap()).unwrap());
+    let task = store.task(task_id).expect("task persisted");
+    assert_eq!(task.project_id, project().id);
+    assert_eq!(task.owner_agent_id, owner);
+    assert_eq!(task.state, BackgroundTaskState::Running);
+    assert_eq!(task.wake_policy, BackgroundTaskWakePolicy::WakeOwner);
+    assert_eq!(
+        task.kind,
+        domain::BackgroundTaskKind::Command {
+            label: "B8 T1".to_owned(),
+        }
+    );
+
+    let specs = runner.specs();
+    assert_eq!(specs.len(), 1);
+    assert_eq!(specs[0].task_id, task_id);
+    assert_eq!(specs[0].owner_agent_id, owner);
+    assert_eq!(specs[0].wake_policy, BackgroundTaskWakePolicy::WakeOwner);
+    let command = specs[0].command.as_ref().expect("command spec");
+    assert_eq!(command.command, "bash");
+    assert_eq!(
+        command.args,
+        vec![
+            "-lc".to_owned(),
+            "sleep 45 && echo DONE_MARKER_DEVBACKEND_B8_T1".to_owned(),
+        ]
+    );
+    assert_eq!(command.cwd.as_str(), "/home/me/proj/crates");
+}
+
 #[tokio::test]
 async fn spawn_known_agent_launches_without_recreating() {
     let agent = scratch_agent(aid(1), "dev-backend", "agents/dev-backend.md");
diff --git a/crates/domain/src/orchestrator.rs b/crates/domain/src/orchestrator.rs
index b1afc58..7e1cf39 100644
--- a/crates/domain/src/orchestrator.rs
+++ b/crates/domain/src/orchestrator.rs
@@ -159,6 +159,24 @@ pub struct OrchestratorRequest {
     /// the other actions.
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub last_delegation: Option<String>,
+    /// Human-facing label for `background.run`. Required by that action, ignored
+    /// by the other actions.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub label: Option<String>,
+    /// Executable for `background.run`. Required by that action, ignored by the
+    /// other actions.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub command: Option<String>,
+    /// Arguments for `background.run`. Optional and defaults to an empty list.
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub args: Vec<String>,
+    /// Optional working directory for `background.run`, resolved by the
+    /// application layer under the project root.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub cwd: Option<String>,
+    /// Optional absolute deadline for `background.run`, epoch milliseconds.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub deadline_ms: Option<u64>,
 }
 
 /// A validated orchestrator command — the only thing the application layer acts on.
@@ -323,6 +341,25 @@ pub enum OrchestratorCommand {
         /// The ticket of the most recent delegation it issued, if any.
         last_delegation: Option<TicketId>,
     },
+    /// Start a command-backed first-class background task (`idea_run_in_background`).
+    ///
+    /// The owner is the connected peer's handshake identity (`requestedBy`), never
+    /// a model-supplied parameter. The application layer resolves the project from
+    /// the dispatch context and forces `WakeOwner`.
+    RunInBackground {
+        /// Owning agent, parsed from `requestedBy`.
+        owner: AgentId,
+        /// Human-facing label.
+        label: String,
+        /// Executable to run.
+        command: String,
+        /// Command arguments.
+        args: Vec<String>,
+        /// Optional working directory, resolved under the project root downstream.
+        cwd: Option<String>,
+        /// Optional absolute deadline, epoch milliseconds.
+        deadline_ms: Option<u64>,
+    },
 }
 
 /// Where IdeA should place a launched agent session.
@@ -433,6 +470,19 @@ impl OrchestratorRequest {
                 last_delegation: self
                     .parse_optional_ticket(action, self.last_delegation.as_deref())?,
             }),
+            "background.run" => Ok(OrchestratorCommand::RunInBackground {
+                owner: self.require_from(action)?,
+                label: self.require("label", action, self.label.as_deref())?,
+                command: self.require("command", action, self.command.as_deref())?,
+                args: self.args.clone(),
+                cwd: self
+                    .cwd
+                    .as_deref()
+                    .map(str::trim)
+                    .filter(|s| !s.is_empty())
+                    .map(str::to_owned),
+                deadline_ms: self.deadline_ms,
+            }),
             "list_agents" | "agent.list" => Ok(OrchestratorCommand::ListAgents),
             "create_skill" | "skill.create" => Ok(OrchestratorCommand::CreateSkill {
                 name: self.require_name(action)?,
@@ -1139,6 +1189,60 @@ mod tests {
         );
     }
 
+    #[test]
+    fn background_run_keys_owner_on_requester_and_parses_command() {
+        let owner = uuid::Uuid::from_u128(33);
+        let r = req(&format!(
+            r#"{{ "type":"background.run", "requestedBy":"{owner}", "label":"long test",
+                  "command":"bash", "args":["-lc","sleep 1 && echo done"],
+                  "cwd":"subdir", "deadlineMs":12345 }}"#
+        ));
+
+        assert_eq!(
+            r.validate().unwrap(),
+            OrchestratorCommand::RunInBackground {
+                owner: AgentId::from_uuid(owner),
+                label: "long test".to_owned(),
+                command: "bash".to_owned(),
+                args: vec!["-lc".to_owned(), "sleep 1 && echo done".to_owned()],
+                cwd: Some("subdir".to_owned()),
+                deadline_ms: Some(12345),
+            }
+        );
+    }
+
+    #[test]
+    fn background_run_requires_handshake_owner_label_and_command() {
+        assert_eq!(
+            req(r#"{ "type":"background.run", "label":"x", "command":"bash" }"#).validate(),
+            Err(OrchestratorError::MissingField {
+                action: "background.run".to_owned(),
+                field: "requestedBy".to_owned(),
+            })
+        );
+        let owner = uuid::Uuid::from_u128(33);
+        assert_eq!(
+            req(&format!(
+                r#"{{ "type":"background.run", "requestedBy":"{owner}", "command":"bash" }}"#
+            ))
+            .validate(),
+            Err(OrchestratorError::MissingField {
+                action: "background.run".to_owned(),
+                field: "label".to_owned(),
+            })
+        );
+        assert_eq!(
+            req(&format!(
+                r#"{{ "type":"background.run", "requestedBy":"{owner}", "label":"x" }}"#
+            ))
+            .validate(),
+            Err(OrchestratorError::MissingField {
+                action: "background.run".to_owned(),
+                field: "command".to_owned(),
+            })
+        );
+    }
+
     #[test]
     fn unknown_action_is_rejected() {
         let r = req(r#"{ "action": "delete_everything", "name": "a" }"#);
diff --git a/crates/infrastructure/src/orchestrator/mcp/tools.rs b/crates/infrastructure/src/orchestrator/mcp/tools.rs
index 0753ff5..0d2fa79 100644
--- a/crates/infrastructure/src/orchestrator/mcp/tools.rs
+++ b/crates/infrastructure/src/orchestrator/mcp/tools.rs
@@ -60,6 +60,7 @@ pub fn tool_returns_reply(tool: &str) -> bool {
             | "idea_context_read"
             | "idea_memory_read"
             | "idea_skill_read"
+            | "idea_run_in_background"
             | "idea_workstate_read"
     ) || is_ticket_tool(tool)
 }
@@ -103,6 +104,27 @@ pub fn catalogue() -> Vec<ToolDef> {
                 "additionalProperties": false
             }),
         },
+        ToolDef {
+            name: "idea_run_in_background",
+            description: "Run a command as a first-class IdeA background task. Returns the task id \
+                          immediately; completion is delivered later to your inbox.",
+            input_schema: json!({
+                "type": "object",
+                "properties": {
+                    "label": { "type": "string", "description": "Human-facing label for the background task." },
+                    "command": { "type": "string", "description": "Executable to run." },
+                    "args": {
+                        "type": "array",
+                        "items": { "type": "string" },
+                        "description": "Command arguments."
+                    },
+                    "cwd": { "type": "string", "description": "Working directory under the project root. Defaults to the project root." },
+                    "deadline_ms": { "type": "number", "description": "Optional absolute deadline, epoch milliseconds." }
+                },
+                "required": ["label", "command"],
+                "additionalProperties": false
+            }),
+        },
         ToolDef {
             name: "idea_launch_agent",
             description: "Launch (or attach) an IdeA agent. Fire-and-forget: returns once IdeA \
@@ -316,6 +338,16 @@ pub fn map_tool_call(
             task: s("task"),
             ..base()
         },
+        "idea_run_in_background" => OrchestratorRequest {
+            request_type: Some("background.run".to_owned()),
+            requested_by: Some(requester.to_owned()),
+            label: s("label"),
+            command: s("command"),
+            args: string_array(args.get("args"), name)?,
+            cwd: s("cwd"),
+            deadline_ms: optional_u64(args.get("deadline_ms"), name)?,
+            ..base()
+        },
         "idea_stop_agent" => OrchestratorRequest {
             request_type: Some("agent.stop".to_owned()),
             target_agent: s("target"),
@@ -417,6 +449,11 @@ fn base() -> OrchestratorRequest {
         intent: None,
         progress: None,
         last_delegation: None,
+        label: None,
+        command: None,
+        args: Vec::new(),
+        cwd: None,
+        deadline_ms: None,
     }
 }
 
@@ -430,6 +467,33 @@ fn parse_node_id(value: Option<&Value>) -> Option<domain::NodeId> {
         .map(domain::NodeId::from_uuid)
 }
 
+fn string_array(value: Option<&Value>, tool: &str) -> Result<Vec<String>, ToolMapError> {
+    let Some(value) = value else {
+        return Ok(Vec::new());
+    };
+    let items = value
+        .as_array()
+        .ok_or_else(|| ToolMapError::BadArguments(tool.to_owned()))?;
+    items
+        .iter()
+        .map(|item| {
+            item.as_str()
+                .map(str::to_owned)
+                .ok_or_else(|| ToolMapError::BadArguments(tool.to_owned()))
+        })
+        .collect()
+}
+
+fn optional_u64(value: Option<&Value>, tool: &str) -> Result<Option<u64>, ToolMapError> {
+    let Some(value) = value else {
+        return Ok(None);
+    };
+    value
+        .as_u64()
+        .map(Some)
+        .ok_or_else(|| ToolMapError::BadArguments(tool.to_owned()))
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -479,6 +543,66 @@ mod tests {
         );
     }
 
+    #[test]
+    fn run_in_background_maps_to_background_command_with_handshake_owner() {
+        let cmd = map_tool_call(
+            "idea_run_in_background",
+            &json!({
+                "label": "B8 T1",
+                "command": "bash",
+                "args": ["-lc", "sleep 45 && echo DONE"],
+                "cwd": "crates",
+                "deadline_ms": 123456
+            }),
+            REQ,
+        )
+        .unwrap();
+
+        assert_eq!(
+            cmd,
+            OrchestratorCommand::RunInBackground {
+                owner: domain::AgentId::from_uuid(uuid::Uuid::parse_str(REQ).unwrap()),
+                label: "B8 T1".to_owned(),
+                command: "bash".to_owned(),
+                args: vec!["-lc".to_owned(), "sleep 45 && echo DONE".to_owned()],
+                cwd: Some("crates".to_owned()),
+                deadline_ms: Some(123456),
+            }
+        );
+        assert!(tool_returns_reply("idea_run_in_background"));
+    }
+
+    #[test]
+    fn run_in_background_rejects_absent_requester_and_malformed_args() {
+        let no_requester = map_tool_call(
+            "idea_run_in_background",
+            &json!({ "label": "x", "command": "bash" }),
+            "",
+        );
+        assert!(matches!(no_requester, Err(ToolMapError::Invalid(_))));
+
+        assert_eq!(
+            map_tool_call(
+                "idea_run_in_background",
+                &json!({ "label": "x", "command": "bash", "args": "nope" }),
+                REQ,
+            ),
+            Err(ToolMapError::BadArguments(
+                "idea_run_in_background".to_owned()
+            ))
+        );
+        assert_eq!(
+            map_tool_call(
+                "idea_run_in_background",
+                &json!({ "label": "x", "command": "bash", "args": [1] }),
+                REQ,
+            ),
+            Err(ToolMapError::BadArguments(
+                "idea_run_in_background".to_owned()
+            ))
+        );
+    }
+
     #[test]
     fn launch_agent_maps_to_spawn_background_by_default() {
         let cmd = map("idea_launch_agent", &json!({ "target": "Dev" })).unwrap();
diff --git a/crates/infrastructure/tests/mcp_server.rs b/crates/infrastructure/tests/mcp_server.rs
index 2b84c5c..96a211b 100644
--- a/crates/infrastructure/tests/mcp_server.rs
+++ b/crates/infrastructure/tests/mcp_server.rs
@@ -486,6 +486,7 @@ async fn tools_list_advertises_the_idea_tools_with_schemas() {
     for expected in [
         "idea_list_agents",
         "idea_ask_agent",
+        "idea_run_in_background",
         "idea_launch_agent",
         "idea_stop_agent",
         "idea_update_context",
@@ -520,8 +521,8 @@ async fn tools_list_advertises_the_idea_tools_with_schemas() {
     assert!(!names.contains(&"idea_reply"));
     assert_eq!(
         tools.len(),
-        23,
-        "exactly the twenty-three exposed idea_* tools; got {names:?}"
+        24,
+        "exactly the twenty-four exposed idea_* tools; got {names:?}"
     );
 
     // Every tool advertises an object input schema.