Build a custom adapter to connect FideliOS to any agent runtime.
If you’re using Claude Code, the .agents/skills/create-agent-adapter skill can guide you through the full adapter creation process interactively. Just ask Claude to create a new adapter and it will walk you through each step.

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Package Structure

packages/adapters/<name>/
  package.json
  tsconfig.json
  src/
    index.ts            # Shared metadata
    server/
      index.ts          # Server exports
      execute.ts        # Core execution logic
      parse.ts          # Output parsing
      test.ts           # Environment diagnostics
    ui/
      index.ts          # UI exports
      parse-stdout.ts   # Transcript parser
      build-config.ts   # Config builder
    cli/
      index.ts          # CLI exports
      format-event.ts   # Terminal formatter

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Step 1: Root Metadata

src/index.ts is imported by all three consumers. Keep it dependency-free. 
export const type = "my_agent";        // snake_case, globally unique
export const label = "My Agent (local)";
export const models = [
  { id: "model-a", label: "Model A" },
];
export const agentConfigurationDoc = `# my_agent configuration
Use when: ...
Don't use when: ...
Core fields: ...
`;

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Step 2: Server Execute

src/server/execute.ts is the core. It receives an AdapterExecutionContext and returns an AdapterExecutionResult. Key responsibilities:
  1. Read config using safe helpers (asString, asNumber, etc.)
  2. Build environment with buildFideliOSEnv(agent) plus context vars
  3. Resolve session state from runtime.sessionParams
  4. Render prompt with renderTemplate(template, data)
  5. Spawn the process with runChildProcess() or call via fetch()
  6. Parse output for usage, costs, session state, errors
  7. Handle unknown session errors (retry fresh, set clearSession: true)

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Step 3: Environment Test

src/server/test.ts validates the adapter config before running. Return structured diagnostics:
  • error for invalid/unusable setup
  • warn for non-blocking issues
  • info for successful checks

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Step 4: UI Module

  • parse-stdout.ts — converts stdout lines to TranscriptEntry[] for the run viewer
  • build-config.ts — converts form values to adapterConfig JSON
  • Config fields React component in ui/src/adapters/<name>/config-fields.tsx

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Step 5: CLI Module

format-event.ts — pretty-prints stdout for fidelios run --watch using picocolors.

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Step 6: Register

Add the adapter to all three registries:
  1. server/src/adapters/registry.ts
  2. ui/src/adapters/registry.ts
  3. cli/src/adapters/registry.ts

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Skills Injection

Make FideliOS skills discoverable to your agent runtime without writing to the agent’s working directory:
  1. Best: tmpdir + flag — create tmpdir, symlink skills, pass via CLI flag, clean up after
  2. Acceptable: global config dir — symlink to the runtime’s global plugins directory
  3. Acceptable: env var — point a skills path env var at the repo’s skills/ directory
  4. Last resort: prompt injection — include skill content in the prompt template

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Security

  • Treat agent output as untrusted (parse defensively, never execute)
  • Inject secrets via environment variables, not prompts
  • Configure network access controls if the runtime supports them
  • Always enforce timeout and grace period