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Agents

← Docs index

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

Agents View (Dashboard)

The agents surface provides:

  • Agent-first list/board/tree/org collection (primary content appears first)
  • A compact Controls popup for secondary actions (state filter, Show system agents toggle, Import, and global Heartbeat Speed)
  • Detail/config panels
  • Runtime metrics and active-agent live cards rendered below the main collection
  • A per-agent Token Usage panel that summarizes cumulative token consumption for the currently displayed agents
  • Run history
  • Task assignment context

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

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

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)
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
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".

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

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

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:

# 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.

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 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

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:

{
  "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