flynn/docs/architecture/AGENT_DIAGRAM.md

Agent-Oriented Project Diagram

This is a high-signal, agent-oriented view of Flynn's structure and execution flow.

If you're new to the codebase, start here, then jump to the referenced files.

Big Picture (Runtime Data Flow)

Inbound Message
  (Telegram/Discord/Slack/WhatsApp/WebChat)
        |
        v
ChannelAdapter  ->  ChannelRegistry
        |               |
        |               v
        |        createMessageRouter()
        |               |
        |               v
        |         SessionManager
        |               |
        |               v
        |        AgentOrchestrator
        |               |
        |               v
        |           NativeAgent
        |               |
        |        ModelRouter.chat()
        |               |
        |               v
        |          ModelClient
        |
        +----> (optional) PairingManager gate for unknown senders

Tool Calls (inside NativeAgent loop)
  NativeAgent -> ToolRegistry (policy-filtered) -> ToolExecutor
                 |                                 |
                 |                                 v
                 |                          HookEngine + autonomy
                 |                                 |
                 |                                 v
                 |                               Tool.execute()
                 |                                 |
                 |                                 v
                 +---------------------------> AuditLogger (redacted)

Outbound Reply
  -> ChannelAdapter.send()  (text + optional attachments)

Key files:

• Routing + per-session agent creation: src/daemon/routing.ts
• Orchestration: src/backends/native/orchestrator.ts
• Tool loop: src/backends/native/agent.ts
• Model routing: src/models/router.ts
• Tool policy + execution: src/tools/policy.ts, src/tools/executor.ts

Component Graph (Agent-Safety Boundary)

                 +---------------------------+
                 |         Config            |
                 |   (Zod schema + YAML)     |
                 |   src/config/schema.ts    |
                 +-------------+-------------+
                               |
                               v
 +-------------------+   +-------------+   +------------------+
 |   SkillRegistry   |   | ToolPolicy  |   |   HookEngine      |
 | src/skills/*      |   | src/tools/* |   | src/hooks/*       |
 +---------+---------+   +------+------+   +---------+--------+
           |                    |                    |
           | (system prompt)    | (allow/deny)       | (confirm/log/silent)
           v                    v                    v
 +-------------------+   +-------------+   +------------------+
 | System Prompt     |   | ToolRegistry|   | ToolExecutor      |
 | src/daemon/services.ts| src/tools/* |   | src/tools/executor.ts
 +---------+---------+   +------+------+   +---------+--------+
           |                    |                    |
           v                    |                    |
 +-------------------+          |                    v
 | AgentOrchestrator |          |              +-----------+
 | src/backends/*    |          +------------> | AuditLogger|
 +---------+---------+                         | src/audit/*|
           |
           v
 +-------------------+
 |   NativeAgent     |
 | src/backends/*    |
 +---------+---------+
           |
           v
 +-------------------+
 |   ModelRouter      |
 | src/models/*       |
 +-------------------+

Skills + Capabilities (What Gets Enforced)

Skills are local directories with:

• SKILL.md (instructions injected into the system prompt)
• manifest.json (metadata + optional permissions)

Skill permissions enforcement points

• Tool availability: ToolPolicy.resolveAllowedNames() intersects allowed tools with manifest.json.permissions.
• Tool execution (defense in depth): ToolExecutor.execute() enforces:
  • fs allowlists (permissions.fs.read / permissions.fs.write)
  • net allowlists (best-effort for web.fetch)
  • secret scopes (tools declare requiredSecretScopes, skills allow permissions.secrets)
  • injection guard when untrusted content is present

Important default:

• If a request is routed into a skill context but the skill has no permissions manifest, tool access is denied.

Key files:

• Skill manifest types: src/skills/types.ts
• Loader validation: src/skills/loader.ts
• Policy intersection: src/tools/policy.ts
• Executor enforcement: src/tools/executor.ts

Sandbox Execution (High-Risk Tools)

Flynn supports per-session Docker sandboxes.

Where sandboxing is applied today:

• shell.exec and process.start can be replaced with sandboxed implementations.
• Replacement is wired in src/daemon/routing.ts by cloning the ToolRegistry and swapping the tool implementations.

Skill context default:

• High-risk tool execution defaults to sandbox in skill context (when available).
• A skill can opt into host execution only by setting permissions.execution_environment: "host".

Key files:

• Sandbox lifecycle: src/sandbox/manager.ts, src/sandbox/docker.ts
• Sandboxed tool wrappers: src/sandbox/tools.ts
• Wiring: src/daemon/routing.ts

Prompt Injection Hardening (Practical)

Flynn treats content provenance as part of the control boundary:

• web.fetch, web.search, and browser.content outputs are treated as untrusted "fetched_content".
• Tool results are wrapped in provenance markers inside the tool loop.
• Once untrusted content is seen, ToolExecutor applies stricter gating (blocks obvious injection patterns for high-risk tools).

Key files:

• Provenance wrapping: src/backends/native/agent.ts
• Tool-call guard: src/tools/executor.ts
• System prompt safety guidance: src/daemon/services.ts

Mermaid (For Fast Visual Scanning)

If your renderer supports Mermaid, this is the same information as a sequence diagram.

sequenceDiagram
  autonumber
  participant U as User
  participant CA as ChannelAdapter
  participant CR as ChannelRegistry
  participant SM as SessionManager
  participant AR as AgentOrchestrator
  participant NA as NativeAgent
  participant MR as ModelRouter
  participant MC as ModelClient
  participant TP as ToolPolicy/Registry
  participant TE as ToolExecutor
  participant HE as HookEngine
  participant AL as AuditLogger

  U->>CA: message
  CA->>CR: onMessage(InboundMessage)
  CR->>SM: getSession(channel, sender)
  SM-->>CR: Session
  CR->>AR: getOrCreateAgent(session + routing)
  AR->>NA: process(userMessage)
  NA->>MR: chat(messages + tools)
  MR->>MC: provider request
  MC-->>MR: response (content or tool_calls)
  MR-->>NA: ChatResponse

  alt model requests tool use
    NA->>TP: filtered tool list (skill + policy)
    NA->>TE: execute(tool, args, context)
    TE->>HE: confirm/log/silent (autonomy)
    HE-->>TE: approved/denied
    TE->>AL: audit (redacted)
    TE-->>NA: ToolResult
    NA->>MR: chat(tool_result blocks)
  end

  NA-->>AR: assistant response
  AR-->>CR: OutboundMessage
  CR-->>CA: send()
  CA-->>U: reply