## Public feature reference This chapter is the compact index to the entire supplied public inventory\. It is intentionally grouped by purpose rather than presented as one giant type dump\. ### `ExtensionAPI`\: registration and module access | Members | Practical contract | Worked example | | --- | --- | --- | | `logger` | File logging\; avoid console output that corrupts TUI\/RPC channels and avoid logging secrets | Lab status\; native delegation | | `typebox`\, `arktype`\, `zod` | Injected compatible schema authoring | Seed Desk\; Package Lab | | `pi` | Injected coding\-agent package exports\; availability still follows the matching host | SDK\-oriented integrations | | `on` | Subscribe using the exact supported event name and return shape | [Event reference]() | | `registerTool` | Register a schema\-shaped machine capability | Seed Desk\; Review Desk | | `registerCommand` | Register a human\/host slash\-command handler | All principal stories | | `registerShortcut` | Register a nonreserved operator key binding | Phrase\-key exercise | | `registerFlag`\, `getFlag` | Declare\/read a boolean or string flag\; read your own registered name | `seed-quiet` | | `setLabel` | Set the extension’s display label in the supplied concrete implementation | Lab status | | `registerMessageRenderer` | Render a named custom message type | Review Desk | | `registerAssistantThinkingRenderer` | Add supplemental UI after visible thinking blocks | Thinking\-length exercise | | `registerComposerShape` | Register a complete composer rendering contract | Workbook Field Dock | | `registerFileWriteFallback`\, `registerFileDeleteFallback` | Register separate native permission\-denied mutation seams | [File fallbacks]() | | `registerProvider`\, `unregisterProvider` | Register\/remove runtime model\-provider overrides | [Providers]() | | `events` | Shared runtime event bus with `on`\, `emit`\, `clear` | Field events | **`setLabel` compatibility edge\:** the public type advertises both extension\-label and entry\-label usage\, but `ConcreteExtensionAPI.setLabel(label)` only assigns the extension label in this snapshot\. Do not claim that the two\-argument form labels a journal entry here\. Do not cast the read\-only session manager to bypass the public boundary\. ### `ExtensionAPI`\: live actions | Members | Practical contract | | --- | --- | | `sendMessage` | Custom conversation\/context message\; optional steer\/follow\-up\/next\-turn and turn trigger | | `captureSessionTarget`\, `deliverMessage` | Persistent owner anchor and deduplicated complete delivery with a receipt | | `sendUserMessage` | User\-style prompt\/queue\; no slash\-command dispatch | | `appendEntry` | Custom state entry\, not model\-visible content | | `exec` | Program\/argv execution with cwd\, timeout and cancellation | | `getActiveTools`\, `getAllTools`\, `setActiveTools` | Enabled\-set inspection\, full registry metadata and asynchronous selection | | `getCommands` | Dynamic command metadata\, not a universal list of built\-ins | | `setModel` | Credential\-aware model selection | | `getThinkingLevel`\, `setThinkingLevel` | Effective thinking\-level control | | `getServiceTiers`\, `setServiceTier` | Detached per\-family tier snapshot and subsequent\-request override | | `getSessionName`\, `setSessionName` | Read\/set persisted session naming\, distinct from terminal title | `getCommands()` aggregates extension commands\, loaded custom\/MCP prompt commands and enabled skill commands through `getSessionSlashCommands()`\. Built\-ins are intentionally excluded from that helper\. Frontends may advertise a larger command list\. `RegisteredCommand` contains `name`\, optional `description`\, optional `getArgumentCompletions`\, and `handler`\. Completion values represent the complete argument text\, not just an appended fragment\. ### `ExtensionContext` | Members | What to remember | | --- | --- | | `ui`\, `mode`\, `hasUI` | Mode and actual method support matter\; `hasUI` is not “all TUI methods work” | | `cwd` | Current at context creation\; do not retain it as a permanent workspace identity | | `sessionManager` | Read\-oriented session\/journal access | | `modelRegistry` | Host registry and credential\-resolution access\; prefer `models` for selection queries | | `model`\, `models` | Current\/request\-specific model and read\-only query facade | | `localProtocolOptions` | Calling\-session `local://` mapping for compatible bridges | | `getContextUsage` | Estimated context tokens\/window\/percentage\; can be undefined | | `getAsyncJobSnapshot` | Read\-only owner\-scoped job state\; can be null | | `isIdle`\, `hasPendingMessages` | Snapshot predicates\, not locks | | `abort` | Request cancellation of the current agent operation | | `shutdown` | Request host shutdown\; host\-specific and not an immediate `process.exit` guarantee | | `getSystemPrompt` | Effective prompt blocks\; treat returned content as sensitive | | `compact` | Request host maintenance at a safe boundary | | `memory` | Optional status\/search\/save runtime | | `setInterval`\, `setTimeout`\, `clearTimer` | Managed timer lifecycle | | `invokeTool` | Optional same\-name native built\-in delegation | | `isProjectTrusted` | Compatibility method returning true\, not isolation | The read\-oriented session manager exposes identity\/cwd\/header\/leaf\/entry\/branch\/tree\/label\/usage queries\. It also includes artifact\/blob helpers such as `allocateArtifactPath`\, `saveArtifact`\, `getArtifactPath`\, `putBlob` and `putBlobSync`\. “Readonly” here does not mean every helper is side\-effect\-free\: artifact\/blob helpers can store data\. It means extensions are not handed the journal’s general navigation\/mutation API\. Use\: - `getBranch()` for branch\-derived state\; - `getEntries()` for deliberately whole\-journal inspection\; - `getEntry()` and `getTree()` for stable navigation targets\. Do not mutate returned session records in place\. ### `ExtensionCommandContext` Commands inherit the general context and additionally expose\: - `getContextUsage`\; - `waitForIdle`\; - `newSession`\; - `branch`\; - `navigateTree`\; - `switchSession`\; - `reload`\; - `compact`\. The duplicated usage\/compaction members remain the same public concepts\. The navigation methods are command\-only\. The supplied ACP shutdown action is inert\. Other hosts request deferred graceful shutdown\. Do not build essential durable cleanup around an assumption that `ctx.shutdown()` terminates every embedding\. ### Tool metadata and provenance `ToolInfo` contains\: - `name`\; - `description`\; - `parameters`\; - optional `promptGuidelines`\; - `sourceInfo`\. `SourceInfo` contains\: - `path`\; - `source`\, such as builtin\, SDK\, MCP or extension\; - `scope`\: user\, project or temporary\; - `origin`\: package or top\-level\; - optional `baseDir`\. This metadata answers “where did the tool come from\?” It is not an authorization certificate\. `ToolRenderResultOptions` contains `expanded`\, `isPartial`\, `spinnerFrame`\. `ToolSessionEvent` contains `reason` and `previousSessionFile`\. `ToolShellEnvironmentContext` contains `command`\, `cwd` and `env`\. All `ToolDefinition` fields are explained in [Tools\, interception and native delegation]()\. ### UI inventory index Every supplied `ExtensionUIContext` member belongs to one of these families\: - Dialogs\: `timeoutStartsOnPresentation`\, `select`\, `confirm`\, `input`\, optional `askDialog`\, `editor`\. - Notices and layout\: `notify`\, `setStatus`\, `setWorkingMessage`\, `setWidget`\, `setFooter`\, `setHeader`\, `setTitle`\. - Native components\/input\: `custom`\, `onTerminalInput`\. - Composer editing\: `setEditorText`\, `pasteToEditor`\, `getEditorText`\, `addAutocompleteProvider`\, `setEditorComponent`\. - Appearance\: `theme`\, `getAllThemes`\, `getTheme`\, `setTheme`\, `getToolsExpanded`\, `setToolsExpanded`\. The complete dialog\/select\/ask\/custom option shapes are explained in [Review Desk’s UI chapter]()\. Composer shape fields are explained in [Editors\, themes and composer shapes]()\. ### Named\-interface coverage index The supplied inventory’s 27 named interfaces are covered as follows\: | Family | Interfaces | | --- | --- | | Core | `ExtensionAPI`\, `ExtensionContext`\, `ExtensionCommandContext`\, `ExtensionModelQuery` | | Tools | `ToolDefinition`\, `ToolRenderResultOptions`\, `ToolSessionEvent`\, `ToolShellEnvironmentContext`\, `ToolInfo`\, `SourceInfo` | | Commands | `RegisteredCommand` | | UI | `ExtensionUIContext`\, `ExtensionUIDialogOptions`\, `ExtensionCustomOptions`\, `ComposerShapeDefinition`\, `ExtensionUISelectOption` | | Rich ask | `ExtensionAskDialogOption`\, `ExtensionAskDialogQuestion`\, `ExtensionAskDialogResultItem`\, `ExtensionAskDialogSubmitResult` | | Maintenance | `CompactOptions` | | Providers | `ProviderConfig`\, `ProviderModelConfig` | | Durable delivery | `ExtensionSessionTarget`\, `CaptureSessionTargetOptions`\, `ExtensionDeliveryReceipt`\, `DeliverExtensionMessageOptions` | ### Reserved shortcuts The supplied runner rejects these effective extension shortcuts\: `ctrl+c`\, `ctrl+d`\, `ctrl+z`\, `ctrl+k`\, `ctrl+p`\, `ctrl+l`\, `ctrl+o`\, `ctrl+t`\, `ctrl+g`\, `ctrl+q`\, `alt+m`\, `shift+tab`\, `shift+ctrl+p`\, `alt+enter`\, `escape`\, `enter`\. Other host keybindings can still conflict\. Test the actual chord in the actual terminal\. Built\-in command names are filtered by the host’s reserved command set\. Do not assume a name is available merely because an older example registered it\. *Source\, snapshot 2026\-08\-29\: `packages/coding-agent/src/extensibility/extensions/types.ts`\, supplied public inventory\; `loader.ts`\, `ConcreteExtensionAPI`\; `runner.ts`\; `get-commands-handler.ts`\; `packages/coding-agent/src/session/session-manager.ts`\, `ReadonlySessionManager`\.*