> ## Documentation Index
> Fetch the complete documentation index at: https://docs.useharmonia.xyz/llms.txt
> Use this file to discover all available pages before exploring further.

# Google ADK

> How Harmonia uses Google ADK for typed specialist delegation, callbacks, skills, and managed state deltas.

Google ADK is Harmonia's agent framework. It defines one coordinator and bounded specialists while deterministic worker code controls stage ordering and persistence.

## How Harmonia uses it

* `harmonia_coordinator` delegates one typed task to the requested specialist.
* Nimi, Ryan, Temi, Noni, Dara, Maya, and Nova use separate input/output contracts and model policies.
* ADK `output_key` state deltas carry specialist results back to the deterministic wrapper.
* Noni and Dara run as separate calls inside an application-controlled two-pass maximum.
* Nimi and Ryan each receive one filesystem `SkillToolset` restricted to approved method references.
* Google Search is a separate ADK tool inside isolated request-bound search agents; it never shares a model request with Nimi's or Ryan's filesystem loaders. Nimi can separately use `VertexAiSearchTool` for a configured private index.
* Nimi records and validates independent skill-loader and grounded-research traces. Skill content cannot become search evidence.
* Nova receives a read-only ADK `SkillToolset`; Noni has a filesystem writing skill plus separate grounded-research tools; Dara receives only its filesystem editing-skill loaders; Temi has one planning-method skill plus six request-bound reads over an immutable Firestore snapshot. Maya remains tool-free.
* Callbacks attach authorized media evidence and reset, record, and validate actual skill-loader and tool traces.

ADK output is never workflow truth by itself. Application validators reject incomplete schemas, invented references, authority overreach, and invalid trajectories before Firestore changes.

## Failure behavior

Malformed output becomes a permanent protocol failure. Provider and managed-runtime failures remain typed and visible. Harmonia does not silently switch roles or fabricate successful state.

## Evidence status

Agent construction, routing, schemas, callbacks, and validators have automated local coverage. Managed ADK execution on Vertex AI requires authenticated Agent Engine evidence.

## Relevant files

* `agent/harmonia_agent/agents.py`
* `agent/harmonia_agent/agent_models.py`
* `agent/harmonia_agent/skills_runtime.py`
* `agent/harmonia_agent/team_runtime.py`