---

name: app-development description: "Help users author and customize Flower Apps with ServerApp, ClientApp, Context, Message, records, and pyproject.toml wiring." metadata: disco-role: operating disable-model-invocation: true license: Apache 2.0

app-development

Use this sub-skill for Flower App authoring, inspection, and troubleshooting.

Covers

• ServerApp, ClientApp, Context, Message, RecordDict, ArrayRecord, ConfigRecord, MetricRecord, and Array
• pyproject.toml app metadata and tool.flwr.app.components
• flwr new / flwr run app authoring loops
• Context.run_config, Context.node_config, and Context.state
• lifecycle hooks via lifespan()
• legacy compatibility and deprecation notes for app wiring

Does not cover

• strategy internals
• dataset partitioning
• deployment admin
• repo-maintenance commands

Start here

1. Read references/workflows.md.
2. Check references/api-reference.md for exact signatures and routing rules.
3. Use references/troubleshooting.md for signature, config, and record-type failures.
4. Run scripts/check_flower_app.py for a safe pyproject/component validation and tiny runtime smoke.

Quick routing

• Server orchestration and round entry point: ServerApp
• Client message handlers: ClientApp
• Runtime settings and node-local data: Context
• App payloads: Message and RecordDict
• Arrays, configs, and metrics: ArrayRecord, ConfigRecord, MetricRecord

Practical rule of thumb

Keep app objects stateless. Put per-run memory in context.state, read run-specific values from context.run_config, and read node-specific values from context.node_config.