Add resolveApiKey to before_compact hook event

packages/coding-agent/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Added
+
+- **Compaction hook `resolveApiKey`**: The `before_compact` session event now includes `resolveApiKey` function to resolve API keys for any model (checks settings, OAuth, env vars). Useful for hooks that need to call different models during custom compaction.
+
 ## [0.27.5] - 2025-12-24
 
 ### Added

packages/coding-agent/docs/hooks.md

@@ -184,6 +184,7 @@ For `before_compact` events, additional fields are available:
 - `event.tokensBefore`: Current context token count
 - `event.model`: Model to use for summarization
 - `event.apiKey`: API key for the model
+- `event.resolveApiKey`: Function to resolve API key for any model (checks settings, OAuth, env vars)
 - `event.customInstructions`: Optional custom focus for summary (from `/compact` command)
 
 Return `{ compactionEntry }` to provide a custom summary instead of the default. The `compactionEntry` must have: `type: "compaction"`, `timestamp`, `summary`, `firstKeptEntryIndex` (from `cutPoint`), `tokensBefore`.

packages/coding-agent/src/core/agent-session.ts

@@ -772,6 +772,7 @@ export class AgentSession {
 					customInstructions,
 					model: this.model,
 					apiKey,
+					resolveApiKey: this._resolveApiKey,
 				})) as SessionEventResult | undefined;
 
 				if (result?.cancel) {
@@ -922,6 +923,7 @@ export class AgentSession {
 					customInstructions: undefined,
 					model: this.model,
 					apiKey,
+					resolveApiKey: this._resolveApiKey,
 				})) as SessionEventResult | undefined;
 
 				if (hookResult?.cancel) {

packages/coding-agent/src/core/hooks/types.ts

@@ -135,6 +135,8 @@ export type SessionEvent =
 			customInstructions?: string;
 			model: Model<any>;
 			apiKey: string;
+			/** Resolve API key for any model (checks settings, OAuth, env vars) */
+			resolveApiKey: (model: Model<any>) => Promise<string | undefined>;
 	  })
 	| (SessionEventBase & {
 			reason: "compact";