# Agents

[← Docs index](./README.md)

Fusion uses multiple agent roles for planning, execution, review, and merge workflows.

## Agent Field Parity Matrix

Every first-class editable agent field has a defined create/edit/import/template behavior. This ensures consistent round-tripping across all surfaces.

### Agent Model Fields

| Field | Create | Edit | Import | Notes |
|-------|--------|------|--------|-------|
| `name` | ✓ | ✓ | ✓ (from manifest) | Unique identifier |
| `role` | ✓ | ✓ | ✓ (mapped from manifest) | Agent capability |
| `metadata` | ✓ | ✓ | ✓ | Arbitrary key-value data |
| `title` | ✓ | ✓ | ✓ (from manifest) | Job title/description |
| `icon` | ✓ | ✓ | ✓ (from manifest) | Emoji or icon identifier |
| `reportsTo` | ✓ | ✓ | ✓ (from manifest) | Parent agent ID |
| `runtimeConfig` | ✓ | ✓ | ✗ | Heartbeat/budget config |
| `permissions` | ✓ | ✓ | ✗ | Capability flags |
| `instructionsPath` | ✓ | ✓ | ✗ | File-backed instructions path |
| `instructionsText` | ✓ | ✓ | ✓ (from manifest `instructionBody`) | Inline instructions |
| `soul` | ✓ | ✓ | ✗ | Personality/identity description |
| `memory` | ✓ | ✓ | ✗ | Per-agent accumulated knowledge |
| `bundleConfig` | ✓ | ✓ | ✗ | Structured instruction bundle |

### Agent Companies Manifest Fields

| Manifest Field | First-Class Agent Field | Fallback |
|---------------|------------------------|----------|
| `name` | `name` | — (required) |
| `title` | `title` | — |
| `icon` | `icon` | — |
| `role` | `role` (mapped to AgentCapability) | `custom` |
| `reportsTo` | `reportsTo` | — |
| `instructionBody` | `instructionsText` | — |
| `skills` | `metadata.skills` | — |

### System-Managed Fields (Not User-Editable)

These fields are managed by the engine and cannot be directly edited:

- `id` — Auto-generated unique identifier
- `state` — Agent lifecycle state (managed by engine)
- `taskId` — Current working task (managed by scheduler)
- `totalInputTokens` / `totalOutputTokens` — Token usage totals (managed by engine)
- `createdAt` / `updatedAt` / `lastHeartbeatAt` — Timestamps (managed by system)
- `lastError` — Last error message (managed by engine)
- `pauseReason` — Reason for paused state (managed by engine)

### Stale Task Link Sanitization

The `taskId` field is suppressed in API responses when the linked task is in a terminal state (`done` or `archived`). This prevents stale "working on" UI indicators in the Agents dashboard for agents whose task has already completed.

**Terminal task statuses:**
- `done` — Task completed successfully
- `archived` — Task archived

**Affected API endpoints:**
- `GET /api/agents` — `taskId` is omitted from agents with terminal linked tasks
- `GET /api/agents/:id` — `taskId` is omitted when the linked task is terminal
- `GET /api/agents/stats` — `assignedTaskCount` excludes agents with terminal linked tasks

**Non-terminal task statuses (taskId is preserved):**
- `planning`
- `todo`
- `in-progress`
- `in-review`

**Graceful degradation:**
- If task lookup fails (e.g., task deleted), `taskId` is preserved in the response to avoid false negatives
- The underlying `taskId` is NOT modified in storage — only the API response is sanitized

### Update-Only Fields

These fields can only be set during update (not on create):

- `pauseReason` — Why the agent is paused
- `lastError` — Last error message
- `totalInputTokens` — Accumulated input token count
- `totalOutputTokens` — Accumulated output token count

## Execution Ownership for Assigned Agents

When a task sets `assignedAgentId` to a **durable (non-ephemeral)** agent, that same agent is used as the active execution owner during runtime execution.

Behavior:
- Fusion links the durable agent's `taskId` to the running task for execution visibility
- No synthetic `executor-FN-*` task-worker agent is created for that run
- On completion/error, the durable agent's execution task link is cleared (the durable record is preserved)

Fallback behavior remains unchanged:
- Unassigned tasks still use runtime-managed `executor-FN-*` task-worker agents
- Missing assigned agents, or assigned agents that are ephemeral/runtime-managed, fall back to task-worker execution ownership

Execution-ownership sync intentionally avoids assignment-trigger side effects (`agent:assigned` wakeups) that are intended for control-plane delegation.

## Agents View (Dashboard)

The agents surface provides:

- Agent-first list and board collections use the desktop split-pane layout (primary collection + detail pane)
- Org Chart is a full-view mode that takes over the full Agents content area; selecting a node opens detail in that same full-width region with back navigation to the chart
- Org chart nodes intentionally stay compact (role/state/health hierarchy signal only) and do not enumerate per-agent skill badges; detailed skills remain in list/board/detail surfaces
- A cross-pane **Overview** strip above the split layout with summary metrics and a disclosure to expand active/running live cards
- A compact **Controls** popup for secondary actions (state filter, Show system agents toggle, Import, and global Heartbeat Speed)
- Detail/config panels
- Split-view synchronization: successful saves and lifecycle actions from the right-side Agent Detail pane immediately refresh the left-side list/selection state (no wait for background polling)
- A per-agent **Token Usage** panel that summarizes cumulative token consumption for the currently displayed agents
- Run history
- Task assignment context

### Running Control Opens Live Run Details

When an agent card shows the **Running** control, that control is actionable:

- Clicking **Running** opens Agent Detail directly on the **Runs** tab
- If the agent has an active run ID, that run is automatically expanded
- The run detail payload and log stream are loaded immediately so operators can inspect live execution without manually switching tabs

Other entry points (for example, **View Details** or clicking the agent identity area) continue to open the default Agent Detail Dashboard tab.

### Token Usage Panel

The **Token Usage** panel in Agents view is derived from each agent's persisted cumulative counters:

- `totalInputTokens`
- `totalOutputTokens`

For the current filtered/visible agent set, the panel shows:

- Aggregate input token total
- Aggregate output token total
- Aggregate combined total (`input + output`)
- Per-agent rows sorted by descending combined token usage

If either token field is missing for an agent, the dashboard treats it as `0` so the panel stays stable and never crashes on partial/migrating data.

### Agent Deletion Controls

Agent deletion is available from both the detail header lifecycle controls and the **Settings** tab's danger zone.

- The Settings-tab delete button reuses the same delete flow as the header action.
- Deletion still requires confirmation before calling `DELETE /api/agents/:id`.
- On successful deletion, the dashboard shows a success toast and closes the detail view.
- Deletion availability is intentionally restricted to agents in `idle` or `terminated` state.

![Agents view](./screenshots/agents-view.png)

## Agent Memory Layers in Runtime Tools

When engine sessions include per-agent memory context, the memory tools operate over the full agent-memory workspace under `.fusion/agent-memory/{agentId}/`, not only the inline `agent.memory` field.

Runtime behavior:

- `fn_memory_search` can surface snippets from:
  - `.fusion/agent-memory/{agentId}/MEMORY.md` (long-term)
  - `.fusion/agent-memory/{agentId}/DREAMS.md` (synthesized patterns)
  - `.fusion/agent-memory/{agentId}/YYYY-MM-DD.md` (daily notes)
- `fn_memory_get` is intentionally bounded to those same files only.
- Empty inline `agent.memory` does **not** disable search/read of existing dreams/daily files once the agent-memory workspace exists.

This layered behavior is shared by heartbeat agents and task-scoped sessions that inherit agent identity.

## Research Tools in Planning/Execution Sessions

Triage and executor runtime sessions now include a bounded research tool surface:

- `fn_research_run` — create/start a bounded research run for a focused query
- `fn_research_list` — list recent runs and statuses
- `fn_research_get` — fetch one run's structured findings payload
- `fn_research_cancel` — cancel an active run

These tools return structured metadata (`runId`, `status`, `summary`, `findings`, `citations`, `error`, `setup`) in addition to concise text so downstream model steps can consume results deterministically.

Expected behavior and boundaries:

- Agents should use research only when repository/local context is insufficient
- Queries should stay narrow and task-scoped; avoid open-ended exploration
- If research is disabled or provider setup is incomplete, tools return actionable `setup` responses instead of crashing
- Durable conclusions should be persisted with `fn_task_document_write` (for example, `key="research"`)
- Research runs require the project engine to be running for processing; `fn_research_run` creates the run but does not block for completion unless `wait_for_completion` is set

For the full research workflow, provider setup, CLI commands, and API reference, see the [Research guide](./research.md).

## Built-In Agent Prompt Templates

Fusion includes built-in templates for role prompts:

- `default-executor`
- `default-planning`
- `default-reviewer`
- `default-merger`
- `senior-engineer`
- `strict-reviewer`
- `concise-planning`

These can be assigned per role using `agentPrompts.roleAssignments`.

## Per-Agent Configuration

Agents can be configured with:

- Custom instructions
- Heartbeat interval/timeout limits
- Max concurrent heartbeat runs
- Budget governance settings
- Model overrides for heartbeat sessions

In Agent Detail → **Settings**, configuration fields auto-save after edits (debounced) when validation passes. The inline status indicator shows saving/saved/error state, and no separate **Save Settings** click is required for settings persistence.

### Runtime Configuration Fields

The `runtimeConfig` field on agents supports the following options:

| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `enabled` | `boolean` | `true` | Whether heartbeat triggers are enabled for this agent |
| `heartbeatIntervalMs` | `number` | — | How often the agent should wake up for heartbeat checks (ms) |
| `autoClaimRelevantTasks` | `boolean` | `true` | During no-task heartbeats, opportunistically claim unowned relevant todo tasks that align with the agent's role/soul |
| `heartbeatTimeoutMs` | `number` | — | Time without heartbeat before agent is considered unresponsive (ms) |
| `maxConcurrentRuns` | `number` | `1` | Max concurrent heartbeat runs for this agent |
| `messageResponseMode` | `"immediate" \| "on-heartbeat"` | `"immediate"` | Whether agent wakes immediately on message (immediate) or processes during heartbeat (on-heartbeat). See [Heartbeat Run Mailbox Checking](#heartbeat-run-mailbox-checking) |
| `selfImproveEnabled` | `boolean` | `true` | Enable periodic self-improvement reflection prompts during heartbeat runs |
| `selfImproveIntervalMs` | `number` | `14400000` (4h) | Minimum delay between self-improvement cycles (minimum enforced: 3600000 ms) |
| `lastSelfImproveAt` | `string` (ISO timestamp) | — | Last recorded self-improvement checkpoint timestamp |
| `modelProvider` | `string` | — | AI provider override for heartbeat session |
| `modelId` | `string` | — | AI model ID override for heartbeat session |
| `budgetConfig` | `AgentBudgetConfig` | — | Token budget governance settings |

Heartbeat values are validated and minimum-clamped to 5 minutes (300,000 ms).
Project setting `heartbeatMultiplier` (default `1`) scales resolved heartbeat intervals globally; per-agent `heartbeatIntervalMs` remains the base interval before multiplier scaling. This setting is configured from the **Agents** screen's **Controls** popup under "Heartbeat Speed".

### No-task auto-claim behavior

When an identity-bearing, non-ephemeral agent wakes with no assigned task and `runtimeConfig.autoClaimRelevantTasks !== false`, the heartbeat monitor scans open todo tasks and may claim one before constructing the prompt run.

Guardrails:
- Only unpaused, unassigned, unchecked-out todo tasks with satisfied dependencies are considered
- Claims are rejected for terminal/paused/owned/conflicting tasks
- Checkout safety is preserved (`checkout_conflict` paths are non-fatal skips)
- On successful claim, the same heartbeat run switches into task-scoped execution (no nested run re-entry)

Operators can disable this per agent in **Agent Detail → Settings → Heartbeat Settings → Auto-Claim Relevant Tasks**.

### Self-improvement cycle

When `selfImproveEnabled !== false`, heartbeat runs periodically enter a self-improvement phase once `selfImproveIntervalMs` has elapsed since `lastSelfImproveAt` (or first run with available ratings). During that phase the agent is prompted to:

1. Call `fn_read_evaluations` to inspect ratings/reflections
2. Identify recurring quality issues and trends
3. Call `fn_update_identity` to adjust its own `soul`, `instructionsText`, or `memory`
4. Record concise improvement decisions

After a successful run, the monitor records `lastSelfImproveAt` in `runtimeConfig`.

## Agent Instructions (Dashboard)

The Agent Detail view includes a dedicated **Instructions** tab for editing agent custom instructions. This replaces the previous embedded instructions editor in the Settings tab, providing a more discoverable and user-friendly experience.

### Inline vs File-Backed Instructions

There are two ways to provide custom instructions:

1. **Inline Instructions**: Direct text entry in the dashboard textarea. Good for simple, short instructions.

2. **File-Backed Instructions**: A path to a `.md` file in the project that contains the instructions. Good for:
   - Longer, more complex instructions
   - Version control of instruction changes
   - Sharing instruction files across teams

### Using the Instructions Tab

1. Open an agent from the Agents view
2. Click the **Instructions** tab
3. Enter inline instructions in the **Inline Instructions** textarea
4. Or set a path in **Instructions File Path** (e.g., `.fusion/agents/my-agent.md`)
5. When a path is set, a **File Content** editor appears for direct file editing
6. Save instructions using the **Save Instructions** button
7. Save file content separately using the **Save File** button

### File Editor Behavior

- File content loads automatically when an instructions path is set
- Missing files (ENOENT) are treated as new files with empty content
- Non-ENOENT errors (e.g., permission denied) show an error toast
- The editor has an **Unsaved changes** indicator when file content is modified
- File saves are independent from instruction metadata saves

## Heartbeat Procedure File Access (Agent Detail Modal)

The **Settings** tab in the Agent Detail modal includes a **Heartbeat Procedure** section with an in-modal markdown file viewer/editor.

### How it works

1. The section shows the current `heartbeatProcedurePath`.
2. When a path exists, use **View Heartbeat Markdown** to load and inspect that file without leaving the modal.
3. The editor supports both **Edit** and **Preview** modes, with an unsaved-changes indicator and dedicated save action.
4. Reads/writes are scoped through the workspace file APIs with `projectId` awareness in multi-project mode.

### Relation to upgrade flow

- Canonical per-agent asset directories now use **display name + immutable id suffix** (example: `ceo-agent2736`).
  - Canonical heartbeat path example: `.fusion/agents/ceo-agent2736/HEARTBEAT.md`
  - Canonical managed bundle directory example: `.fusion/agents/ceo-agent2736-instructions/`
- Legacy id-only paths (for example `.fusion/agents/{agent.id}/HEARTBEAT.md`) and previously created display-name-based paths remain supported.
- Upgrade/create flows preserve existing compatible files and directories in place; Fusion does **not** auto-rename or delete old paths.
- If the selected default file does not exist yet, the backend seeds it from the built-in template.
- After upgrade completes and the agent refreshes, operators can immediately open the seeded per-agent `HEARTBEAT.md` from the same modal section.

## New Agent Presets (Dashboard UI)

The New Agent dialog keeps the existing 3-step flow, and step 0 is split into two tabs:

- **Preset personas** (default) — quick-start persona cards that prefill the same fields and immediately advance to step 1 when selected
- **Custom agent** — manual setup for identity, configuration, and the Generate with AI entry point

### Onboarding fields (step 0 custom tab)

The custom tab exposes separate fields for:

- **Title** (`title`) — optional role title/description
- **Soul** (`soul`) — optional personality and communication style guidance
- **Heartbeat Procedure Path** (`heartbeatProcedurePath`) — optional path to the agent heartbeat markdown file, typically `.fusion/agents/<display-name>-<agent-id>/HEARTBEAT.md` (legacy id-only paths remain valid)
- **Instructions Path** (`instructionsPath`) — optional file-backed instructions path
- **Inline Instructions** (`instructionsText`) — optional inline behavior instructions

For long-form prompt authoring, **Soul**, **Agent Memory**, and **Inline Instructions** now use the same rich editing affordances as other prompt editors in the dashboard:

- Larger default editing surfaces for easier drafting
- Plain/edit mode and Markdown preview mode
- Fullscreen expand/collapse editing for long content (safe-area-aware on mobile)

These controls are also available on the editable review step, so prompt content can be reviewed and refined with the same markdown and fullscreen behavior before submit.

### Final review edits (step 2)

Before clicking **Create**, the final review step remains editable for identity/instruction fields so operators can make last-minute corrections without navigating backward. The review step includes edit-in-place controls for:

- Title
- Soul
- Heartbeat Procedure Path
- Instructions Path
- Inline Instructions

The final `createAgent(...)` call always uses the latest values from these step-2 controls.

### Experimental planning-style onboarding

When **Settings → Experimental Features → Planning-style Agent Onboarding** (`experimentalFeatures.agentOnboarding`) is enabled, clicking **New Agent** opens an AI-guided onboarding modal instead of jumping straight to the classic dialog.

- The onboarding flow asks clarifying questions using repo-aware context (existing agents + preset/template options).
- It generates a **draft** agent configuration summary (name/role/instructions and optional template or pattern provenance).
- Clicking **Continue to agent form** hands that draft into the existing `NewAgentDialog` as a prefill for human review and edits.
- The onboarding flow does **not** auto-create agents directly.

When `experimentalFeatures.agentOnboarding` is disabled, the original `NewAgentDialog` behavior remains unchanged and opens immediately from **New Agent**.

The dashboard provides quick-start presets for common agent roles. Each preset includes:

- **Name and icon** - Display identification
- **Professional title** - Descriptive role title
- **Soul** - Personality and operating principles defining how the agent thinks and communicates
- **Instructions** - Actionable behavioral guidelines

### Preset Library Location

Preset definitions live in `packages/dashboard/app/components/agent-presets/`:

```
agent-presets/
├── index.ts              # Exports AGENT_PRESETS and helper functions
├── ceo/soul.md          # Chief Executive Officer soul
├── cto/soul.md          # Chief Technology Officer soul
├── cmo/soul.md          # Chief Marketing Officer soul
├── cfo/soul.md          # Chief Financial Officer soul
├── engineer/soul.md     # Software Engineer soul
├── backend-engineer/soul.md
├── frontend-engineer/soul.md
├── fullstack-engineer/soul.md
├── qa-engineer/soul.md
├── devops-engineer/soul.md
├── ci-engineer/soul.md
├── security-engineer/soul.md
├── data-engineer/soul.md
├── ml-engineer/soul.md
├── product-manager/soul.md
├── designer/soul.md
├── marketing-manager/soul.md
├── technical-writer/soul.md
├── planning/soul.md
└── reviewer/soul.md
```

### Soul File Format

Each `soul.md` file is a Markdown document containing:

```markdown
# Soul: [Role Name]

[First-person identity statement]

## Operating Principles

[Bullet points describing key behaviors]

## Communication Style

[How the agent communicates]
```

Soul content should be:

- **First-person** - Written from the agent's perspective ("I am...")
- **Role-specific** - Defines the unique character of this role
- **Actionable** - Describes concrete behaviors, not abstract qualities
- **Paperclip-inspired** - Clear ownership, decision discipline, communication standards

### Adding or Modifying Presets

1. Create or edit the `soul.md` file in the appropriate directory
2. Update `index.ts` if adding a new preset (export the imported soul and add to `AGENT_PRESETS` array)
3. Run tests to verify: `pnpm --filter @fusion/dashboard exec vitest run app/components/__tests__/agent-presets.test.ts`

### Preset vs Engine Templates

**Dashboard presets** are a UI-only concept that populates the New Agent dialog fields (name, icon, role, soul, instructionsText). They don't map to engine types.

**Engine role prompts** (in `agentPrompts` settings) define the actual agent behavior when executing tasks. These are separate from dashboard presets and live in project settings.

This separation means:
- Presets provide starting point personality and instructions for new agents
- Engine templates control actual task execution behavior
- An agent created from a preset can have its engine role prompt customized independently

## Configurable Agent Prompts (`agentPrompts`)

`agentPrompts` project setting supports:

- `templates[]`: custom prompt templates by role
- `roleAssignments`: map role → template ID

When no assignment is configured, Fusion falls back to built-in defaults.

## Fine-Grained Prompt Overrides (`promptOverrides`)

The **Prompts** section in the Settings modal provides a user-friendly interface for customizing specific segments of agent prompts. Unlike `agentPrompts` which replaces entire role templates, `promptOverrides` allows surgical customization of individual prompt sections.

### Supported Override Keys

| Key | Agent Role | Description |
|-----|-----------|-------------|
| `executor-welcome` | executor | Introductory section for the executor agent |
| `executor-guardrails` | executor | Behavioral guardrails and constraints |
| `executor-spawning` | executor | Instructions for spawning child agents |
| `executor-completion` | executor | Completion criteria and signaling |
| `triage-welcome` | planning | Introductory section for the planning agent |
| `triage-context` | planning | Context-gathering instructions |
| `reviewer-verdict` | reviewer | Verdict criteria and format |
| `merger-conflicts` | merger | Merge conflict resolution instructions |
| `agent-generation-system` | — | System prompt for AI-assisted agent plan generation |
| `workflow-step-refine` | — | System prompt for refining workflow step descriptions |

### How It Works

1. Navigate to **Settings → Prompts** in the dashboard
2. Each prompt shows its name, key, description, and current value
3. Edit the textarea to create a custom override
4. Click **Reset** to restore the built-in default

### Clearing Overrides

To clear a specific override, click the **Reset** button in the UI. This sends `null` for that prompt key, deleting the override from settings and reverting to the built-in default.

### Relationship with `agentPrompts`

- `agentPrompts` replaces entire role templates
- `promptOverrides` customizes individual segments within any template
- Both can be used together — `promptOverrides` applies to the segment even within a custom role template

## Inter-Agent Messaging

Messaging is available in dashboard mailbox UI and CLI.

```bash
fn message inbox
fn message outbox
fn message send AGENT-001 "Please prioritize FN-420"
fn message read MSG-123
fn message delete MSG-123
fn agent mailbox AGENT-001
```

## Heartbeat Prompt Composition and Autonomous Run Behavior

Heartbeat runs are composed from multiple prompt layers so each wake has full identity and operating context:

1. **System prompt**
   - Task-scoped runs use the task heartbeat system prompt.
   - No-task runs use the ambient/no-task heartbeat system prompt (tool-aligned: no task-scoped tools).
2. **Workspace tool mode**
   - Heartbeat sessions are created with coding-capable workspace tools (`read`, `write`, `edit`, `bash`, `grep`, `find`, `ls`) inside worktree boundary guards.
   - Heartbeat behavior still stays lightweight: one concrete action per run, then `fn_heartbeat_done`.
   - Engine-owned heartbeat tools are still layered on top (task creation/log/docs for task-scoped runs; ambient/delegation/memory tools for no-task runs).
2. **Agent identity and instructions bundle**
   - Inline instructions (`instructionsText`)
   - File-backed instructions (`instructionsPath`)
   - Soul/personality (`soul`)
   - Agent memory (`memory`)
   - Optional project memory guidance (when memory is enabled)
3. **Execution prompt framing**
   - `Identity Snapshot` block (agent ID/role + loaded soul/instructions/memory preview)
   - `Wake Delta` block (source, trigger detail, wake reason, assignment/comments/messages)
   - Heartbeat procedure block (task-scoped or no-task variant, plus optional per-agent procedure override file)

This structure ensures every run re-anchors on identity, wake reason, and current context before taking action.

### Manual / On-Demand Runs Are Autonomous Heartbeats

`POST /api/agents/:id/runs` with `source: "on_demand"` executes the same autonomous heartbeat flow as timer/assignment triggers. It is **not** a mailbox-only poll.

Expected behavior for both manual and automatic triggers:
- Re-check identity/instructions context for this tick
- Process wake delta first (including message/comment wakes)
- Re-evaluate assignment state
- Take exactly one concrete next action
- Finish with `fn_heartbeat_done`

Messages remain an important input signal, but they do not replace the heartbeat procedure.

## Heartbeat Run Mailbox Checking

When messaging tools are enabled for an agent, heartbeat runs check for unread mailbox messages during execution regardless of the trigger type. This ensures agents can see and respond to incoming messages without needing an explicit wake-on-message trigger.

### Reply Linking Contract

Mailbox replies use `message.metadata.replyTo.messageId` as the stable reply link.

- `read_messages` includes each message ID in its human-readable output so agents can target a specific message.
- `send_message` supports `reply_to_message_id`; when provided, the sent message is stored with `metadata.replyTo.messageId`.
- Heartbeat prompts explicitly instruct agents to include `reply_to_message_id` when replying.

The dashboard mailbox UI also uses the same metadata contract when users click **Reply**, so user and agent replies share one threading model.

### How It Works

1. **Message Prefetch**: When `messageStore` is available, heartbeat runs fetch up to 10 unread inbox messages for the agent.
2. **Prompt Injection**: Pending messages are injected into the execution prompt with message ID, sender, and timestamp information.
3. **Reply Guidance**: System instructions remind agents to reply with `reply_to_message_id` for linked threads.
4. **Mark as Read**: After successful heartbeat completion, messages are marked as read.
5. **Failed Runs**: If the heartbeat execution fails, messages remain unread for retry on the next run.

### Message Response Modes

The `messageResponseMode` runtime configuration controls when agents are triggered by incoming messages:

| Mode | Behavior |
|------|----------|
| `immediate` | Agent wakes immediately when a message arrives (via hook callback) |
| `on-heartbeat` | Agent processes messages during normal heartbeat runs only |

**Important**: Both modes include messages in the execution prompt. The `immediate` mode additionally triggers an immediate heartbeat run when a message arrives, while `on-heartbeat` relies on the agent's next scheduled heartbeat.

### Message Visibility

- **Timer-triggered runs**: Check mailbox and include pending messages
- **Assignment-triggered runs**: Check mailbox and include pending messages
- **On-demand runs**: Check mailbox and include pending messages
- **Wake-on-message triggers**: Check mailbox and include pending messages (same as other triggers, but triggered immediately)

This ensures inter-agent and user-to-agent communication is visible to agents on each run, avoiding stale coordination, missed instructions, and delayed responses.

## Agent Spawning

Executor sessions can spawn child agents through `spawn_agent`.

Behavior:

- Child agents run in separate worktrees
- Parent/child relationship is tracked
- Limits enforced:
  - `maxSpawnedAgentsPerParent` (default 5)
  - `maxSpawnedAgentsGlobal` (default 20)
- Child sessions terminate when parent task ends

## Agent Delegation

Executor and heartbeat agents can discover and delegate work to other agents using two built-in tools:

- **`list_agents`** — List available agents with optional filters (role, state, includeEphemeral)
- **`delegate_task`** — Create a task and assign it to a specific agent; the task enters `todo` and the agent picks it up on their next heartbeat

Delegation is designed for cross-agent handoff (e.g., an executor handing off to a QA agent). For parallel worktree-based parallelization, use `spawn_agent` instead.

## Heartbeat Monitoring and Trigger Scheduling

Fusion's `HeartbeatTriggerScheduler` supports five trigger types:

- `timer` — periodic wake based on heartbeat interval
- `assignment` — wake when task is assigned to agent
- `on_demand` — manual run trigger (`POST /api/agents/:id/runs`)
- `automation` — triggered by scheduled automation jobs
- `routine` — triggered by routine execution

All triggers respect per-agent `maxConcurrentRuns` and produce structured wake context metadata.

Pause governance for heartbeat execution:
- `globalPause` is a hard stop: timer, assignment, and on-demand heartbeats are skipped with observable run reasons.
- `enginePaused` is a soft stop for heartbeat timers: timer triggers are skipped, while assignment/on-demand triggers remain allowed for critical responsiveness paths.

### Control-Plane Lane (No Task Concurrency Gating)

Heartbeat runs from the Agents panel run on a **separate control-plane lane** that is independent of task execution concurrency limits. This ensures agent responsiveness is preserved even when task pipelines are saturated.

**Key behaviors:**

- Heartbeat runs (via `POST /api/agents/:id/runs`) execute without gating on `maxConcurrent` or in-progress task count
- The `HeartbeatTriggerScheduler` and `HeartbeatMonitor` components do not receive the task-lane semaphore
- Trigger scheduling remains responsive regardless of how busy the task pipeline is
- Active-run 409 conflict semantics still apply — a new heartbeat run is rejected if the agent already has an active run
- `POST /api/agents/:id/state` applies pause/resume immediately when monitor-bound:
  - Transitioning to `paused` first stops any active run via `HeartbeatMonitor.stopRun(agentId)`
  - Transitioning to `active` immediately calls `HeartbeatMonitor.executeHeartbeat(...)` (source: `on_demand`)

**Architectural boundary:**

| Component | Path | Concurrency |
|-----------|------|------------|
| PlanningProcessor | Task lane | Semaphore-gated |
| TaskExecutor | Task lane | Semaphore-gated |
| Scheduler | Task lane | Semaphore-gated |
| onMerge | Task lane | Semaphore-gated |
| HeartbeatMonitor | Utility/control plane | **NOT** semaphore-gated |
| HeartbeatTriggerScheduler | Utility/control plane | **NOT** semaphore-gated |
| CronRunner | Utility/control plane | **NOT** semaphore-gated |

### Timer State Lifecycle (FN-2289)

Heartbeat timers are armed for agents in valid working states and remain armed across state transitions:

**States where timers remain armed:**
- `active` — Agent is actively working on a task
- `running` — Agent has an active heartbeat run in progress
- `idle` — Agent is between tasks, waiting for work

**States where timers are cleared:**
- `terminated` — Agent has completed or been stopped
- `error` — Agent encountered an unrecoverable error
- `paused` — Agent is paused (e.g., by budget exhaustion or manual action)

**Key behaviors:**
- Timers remain armed when agents transition between `active`, `running`, and `idle` states
- This ensures heartbeat cadence is maintained even when agents complete tasks and await new assignments
- Ephemeral/task-worker agents are never armed with timers (managed directly by TaskExecutor)
- The `runtimeConfig.enabled` flag is respected for disabling heartbeat monitoring entirely

### Unresponsive Recovery (FN-3475)

When a tracked agent misses heartbeat for `2 × heartbeatTimeoutMs`, the monitor now performs recovery (not termination):

1. Dispose the stuck session and untrack the stale run
2. `pauseAgent(agentId, { pauseReason: "heartbeat-unresponsive", stopActiveRun: false })`
3. `resumeAgent(agentId, { triggerDetail: "unresponsive-recovery", triggerSource: "heartbeat-unresponsive", clearPauseReason: true })`

Effects:
- Agent state transitions `running/active → paused → active`
- `pauseReason` is set to `heartbeat-unresponsive` during recovery and cleared on resume
- Assigned tasks are auto-paused with `pausedByAgentId` during pause, then only those same tasks are auto-unpaused on resume
- Resume triggers one on-demand heartbeat restart only when `runtimeConfig.enabled !== false`
- `onTerminated` is reserved for true termination flows and is not used by unresponsive recovery

## Dashboard Health Status

The dashboard displays agent health status in AgentsView, AgentListModal, and AgentDetailView using a centralized health evaluation utility (`packages/dashboard/app/utils/agentHealth.ts`).

### Health Labels (Priority Order)

| Label | Condition |
|-------|-----------|
| **Terminated** | Agent state is "terminated" |
| **Error** | Agent state is "error" (uses lastError if available) |
| **Paused** | Agent state is "paused" (uses pauseReason if available) |
| **Running** | Agent state is "running" (task workers with `active` state also display "Running") |
| **Disabled** | `runtimeConfig.enabled === false` |
| **Starting...** | State is "active" with no lastHeartbeatAt |
| **Idle** | Non-active state with no lastHeartbeatAt |
| **Healthy** | Heartbeat is fresh within configured timeout |
| **Unresponsive** | Heartbeat exceeded configured timeout |

### Timeout Configuration

Health status uses a timeout-based evaluation:

1. If `runtimeConfig.heartbeatTimeoutMs` is set on the agent, use that value
2. Otherwise, use the default 60-second (60000ms) timeout

### Key Behaviors

- **Monitoring disabled**: Agents with `runtimeConfig.enabled === false` display "Disabled" — they are NOT falsely labeled as "Unresponsive"
- **Consistent across views**: All dashboard surfaces use the same centralized utility, ensuring consistent health labels everywhere
- **Auto-refresh**: Health status is refreshed every 30 seconds while views are open to keep status current
- **State-first evaluation**: Terminal states (terminated, error, paused, running) take priority over timeout-based evaluation

## Heartbeat Run Lifecycle

Agent runs have a defined lifecycle managed by `AgentStore`:

### Run States

A heartbeat run can be in one of these states:

- `active` — Run is currently executing
- `completed` — Run finished successfully (via `endHeartbeatRun(runId, "completed")`)
- `terminated` — Run was stopped (via `endHeartbeatRun(runId, "terminated")`)
- `failed` — Run encountered an error

### Run Lifecycle API

- `startHeartbeatRun(agentId)` — Creates a new run and persists it to structured storage
- `endHeartbeatRun(runId, status)` — Ends a run with terminal status, updates persisted state
- `getActiveHeartbeatRun(agentId)` — Returns the current active run (or null)
- `getCompletedHeartbeatRuns(agentId)` — Returns all terminal runs (newest first)
- `saveRun(run)` — Persists run to structured storage
- `getRunDetail(agentId, runId)` — Gets a specific run by ID

### Active-Run Conflict Semantics

When an agent already has an active run, attempts to start a new run return **409 Conflict**:

```
POST /api/agents/:id/runs → 409 { error: "Agent already has an active run", details: { runId } }
```

After a run is completed (or terminated), a new run can be started successfully:

```
POST /api/agents/:id/runs → 201 { id: "run-xxx", status: "active", ... }
```

### Storage Architecture

Run records are stored in structured JSON files at `.fusion/agents/{agentId}-runs/{runId}.json`.

Heartbeat events are also appended to `.fusion/agents/{agentId}-heartbeats.jsonl` for legacy compatibility. The structured storage is the source of truth; heartbeat events provide a fallback for older run data.

### Stopping Runs

Use `POST /api/agents/:id/runs/stop` to terminate an active run:

```
POST /api/agents/:id/runs/stop → 200 { ok: true, runId: "run-xxx" }
```

If there's no active run, returns `{ ok: true, message: "No active run" }`.

## Budget Governance

Per-agent token budget tracking controls costs and prevents runaway AI spending. Budget configuration is stored in `runtimeConfig.budgetConfig`.

### Budget Configuration Fields

| Field | Type | Description |
|-------|------|-------------|
| `tokenBudget` | `number` | Maximum tokens allowed per budget period |
| `usageThreshold` | `number` (0-1) | Percentage threshold (0.8 = 80%) to trigger warning/warning state |
| `budgetPeriod` | `"daily" \| "weekly" \| "monthly" \| "total"` | Reset interval for budget tracking |
| `resetDay` | `number` (0-6) | Day of week for weekly reset (0=Sunday) |

### Budget Status Fields

| Field | Type | Description |
|-------|------|-------------|
| `isOverBudget` | `boolean` | Budget limit exceeded |
| `isOverThreshold` | `boolean` | Usage exceeded warning threshold |
| `periodStart` | `string` | ISO timestamp when current period started |
| `inputTokens` | `number` | Tokens used in current period |
| `outputTokens` | `number` | Tokens generated in current period |
| `totalTokens` | `number` | Combined input + output tokens |

### Enforcement Behavior

Budget enforcement is centralized in `HeartbeatMonitor.executeHeartbeat()`:

- **Timer triggers**: Budget is enforced in `executeHeartbeat()` which creates explicit run records with `budget_exhausted` or `budget_threshold_exceeded` reasons. This makes timer budget skips observable rather than silent drops — users see explicit "skipped" run records in the dashboard instead of timer ticks that appear to "not run".
- **Assignment and on-demand triggers**: Budget is enforced in `executeHeartbeat()` with the same outcome recording. These triggers are allowed when over threshold (but not over budget) to maintain responsiveness.

When the engine is not paused, the `HeartbeatTriggerScheduler` dispatches timer callbacks regardless of budget status, delegating budget enforcement to the execution layer. This ensures every eligible timer tick produces a heartbeat run record that is visible in the agent's run history.

Agents can be paused by budget exhaustion. Timer-triggered heartbeats skip when over threshold to avoid runaway costs, but assignment-triggered and on-demand runs may still execute for responsiveness.

### Budget API Endpoints

| Method | Path | Description |
|--------|------|-------------|
| `GET` | `/api/agents/:id/budget` | Get current budget status |
| `POST` | `/api/agents/:id/budget/reset` | Reset budget counters for current period |

## Agent Performance Ratings

Agent performance ratings allow users and agents to provide feedback that influences future behavior through system prompt injection.

### Rating API Endpoints

| Method | Path | Description |
|--------|------|-------------|
| `GET` | `/api/agents/:id/ratings` | List all ratings for an agent |
| `POST` | `/api/agents/:id/ratings` | Submit a new rating |
| `GET` | `/api/agents/:id/ratings/summary` | Get aggregated rating summary |
| `DELETE` | `/api/agents/:id/ratings/:ratingId` | Delete a specific rating |

### Rating Structure

Ratings use a 1-5 scale:

| Value | Meaning |
|-------|---------|
| 1 | Poor — consistently fails or produces low-quality output |
| 2 | Below average — often needs correction |
| 3 | Average — meets expectations with occasional issues |
| 4 | Good — reliable with minor improvements possible |
| 5 | Excellent — exceeds expectations consistently |

### Rating Summary

The summary endpoint returns aggregated statistics:

```json
{
  "agentId": "AGENT-001",
  "averageRating": 4.2,
  "totalRatings": 15,
  "ratingDistribution": { "1": 0, "2": 1, "3": 2, "4": 8, "5": 4 },
  "trend": "improving"
}
```

The `trend` field indicates rating trajectory: `"improving"`, `"declining"`, or `"stable"`.

### Input Format

To submit a rating:

```
POST /api/agents/:id/ratings
{
  "rating": 4,
  "comment": "Agent completed the task efficiently with minimal corrections needed",
  "taskId": "FN-123"
}
```

## Related Docs

- [Workflow Steps](./workflow-steps.md)
- [Settings Reference](./settings-reference.md)
- [Architecture](./architecture.md)