ACP Extension Core

Provider-neutral contracts for Lody capabilities that are not part of ACP.

Design rules

• Use standard ACP whenever it can carry the behavior: session/fork, elicitation/create, plan_update, usage_update, and normal tool_call/tool_call_update lifecycle messages.
• Put Lody semantics on standard ACP messages under _meta.lody.<feature>.
• Advertise every optional feature under InitializeResponse.agentCapabilities._meta.lody, with an independent integer version.
• Use the _lody/... JSON-RPC namespace only when ACP has no equivalent request or notification.
• All absolute protocol timestamps are Unix epoch seconds and name that unit explicitly. Relative durations also name seconds explicitly.
• Provider adapters translate native data into these contracts. Consumers do not branch on provider-specific payloads.

Standard ACP envelopes

Feature	ACP envelope	Lody metadata
Fork	session/fork	_meta.lody.forkAtTurn for an optional source turn
Ask user	elicitation/create	_meta.lody.elicitation for details JSON Schema cannot express
Proposed plan	plan_update / plan_removed	none required
Context occupancy	usage_update	none required
Subagent/background/scheduled lifecycle	tool_call / tool_call_update	_meta.lody.task
Compaction/retry lifecycle	tool_call / tool_call_update	_meta.lody.activity
Canonical tool identity	tool_call / tool_call_update	_meta.lody.toolName
Goal/notice/title/message phase	normal session update	_meta.lody.<feature>

Custom methods

Method names and their request/response types are exported from src/methods.ts and the adjacent contract modules. LodyExtensionRequestMap, LodyExtensionNotificationMap, and LodyExtensionRequestHandlers bind every wire name to its payload types so adapters cannot implement a method against an unrelated DTO. Rate limits support both proactive _lody/rate_limits/update notifications and independent _lody/rate_limits/get queries. The query is not session-bound; sessionId, accountId, and modelId are optional filters.

Each rate limit's windows is the complete current list of concurrent quota constraints. A window may carry a provider-supplied label such as Fable, displayed alongside its duration. Multiple windows may have the same duration: an all-model weekly quota and a model weekly sub-cap remain separate meters, not additive allowances. Labels are display-only; do not use them for routing or deduplicate windows by duration, utilization, or reset time. This optional field is additive to the version 1 rate-limit contract.

Adapters should emit only the current contracts. Compatibility with payloads that predate this package belongs at the consumer boundary and should be time-bounded.

LODY_TOOL_NAMES defines the stable identities for tool flows that Lody treats specially. Adapters map provider-native names to these values; consumers never infer behavior from a human-facing tool title.