JSBridge protocol

Look up the editor handshake, commands, events, state, and error model.

Envelope

Every packet carries a protocol version, session, sequence number, lane, kind, and type. Requests additionally carry an ID; responses and errors use replyTo. Inbound values are bounded JSON and sequence numbers stay within JavaScript's safe integer range.

Handshake

Text
1WebView                         Native runtime2   |  bridge.hello                   |3   | ------------------------------> |4   |  BridgeReadyPayload             |5   | <------------------------------ |6   |  bridge.readyAck                |7   | ------------------------------> |

BridgeReadyPayload contains capabilities, parameter metadata, current parameter values, and a state snapshot. The editor adopts the returned editorSessionId only after validating the complete payload.

Parameter commands

Type	Purpose
`param.begin`	Begin a host gesture
`param.perform`	Request a normalized edit
`param.end`	End a host gesture
`param.format`	Format a normalized value
`param.parse`	Parse display text
`param.changed`	Confirm host/controller state

Perform edits with a stable gesture ID. The runtime may coalesce pending perform requests while preserving all request IDs that require a response.

State and subscriptions

Reliable topics require an explicit subscription. Snapshot/config/UI commands use revisions to reject stale writes. Meter and realtime log streams are bounded; latest meter values may replace older frames.

Error codes

Important codes include validation_error, unsupported_version, unsupported_type, timeout, backpressure, host_rejected, plugin_faulted, state_conflict, and internal_error.

Errors are data, not thrown native panics. The JavaScript SDK turns an error packet into a rejected Promise with code, message, retryable, and optional bounded details.