Selective context assembly

Enable optional context.assembly on a managed Agent/context. Explicit registerContextContributor(pluginName, companion) replaces that enabled plugin's prompt data view with bounded selectable blocks; no plugin method is auto-detected. createInContextMemoryContributor adapts the built-in whiteboard while retaining all stored entries and protecting critical entries. Default plugin interfaces, layout, saved state, observation hooks and single ToolManager remain unchanged.

Selection supports priorities, full dependency closures, protected data, expiry, source budgets and explicit host projections. Returned blocks are JSON user data, never host instructions. Protected task/evidence/instruction plugins cannot be replaced; violations, stale scope/revisions and deadline/fit failures are explicit. assembly.layout: 'stable-prefix' optionally places legacy dynamic data/date later and sorts tool definitions. Use existing responseReserve plus optional reasoningReserveTokens for headroom appropriate to actual model configuration.

Inspect detached lastPreparation.selection for IDs/status/reasons/tokens and actual provider-input/cache observations. Missing counters stay null, zero stays zero; opaque/multimodal estimates and unknown-model fallback remain uncertain. This is not a provider cache service or a cost-saving guarantee. Source state persists, while callbacks/selection policy must be reattached by trusted host code. AMOS contextAssembly.selectWhiteboard and /context breakdown demonstrate adoption. Account/task and registry-instance changes invalidate old selections. Managed history/input edits from hooks receive one bounded refresh in the same contributor allowance, without repeating hooks or compaction; existing history ownership stays unchanged. JSON repair permits the normal answer commit while rejecting a replaced host prompt or earlier input. Whiteboard overview/store_get guidance reflects partial visibility. Last-request usage includes wrap-up calls and remains separate from stream aggregates; consolidation performs no new contributor fetches. Selected structured run() formats before consolidation; selected structured suspension formats once before saving its session/correlation and emitting suspension. Formatting or storage failure retains the accepted observation in live context; checkpoint it before destruction instead of repeating the action. Native function/custom image/file results and opaque thought signatures set the uncertainty flag, shown by AMOS. Run npm run example:context-dispatch-safety for a deterministic demonstration. Read the complete recipe for public signatures, limits, JSON repair, lifecycle/authorization boundaries and offline/live setup.