diff --git a/apps/cli/ai/sessions/context.ts b/apps/cli/ai/sessions/context.ts
index b88e101f84..4eb2fa0ed4 100644
--- a/apps/cli/ai/sessions/context.ts
+++ b/apps/cli/ai/sessions/context.ts
@@ -1,4 +1,4 @@
-import { isAiModelId, type AiModelId } from '@studio/common/ai/models';
+import { resolveSessionModel, type AiModelId } from '@studio/common/ai/models';
 import { isStudioCustomEntryOfType } from '@studio/common/ai/sessions/entry-types';
 import { AI_PROVIDERS, type AiProviderId } from 'cli/ai/providers';
 import type { LoadedAiSession } from '@studio/common/ai/sessions/types';
@@ -27,31 +27,21 @@ export function resolveResumeSessionContext(
 		context.sessionId = resumeSession.summary.id;
 	}
 
+	// Shared resolution: the most recent recorded model wins, and a removed
+	// model auto-switches to the default so resumed sessions never pin a
+	// model we no longer offer.
+	context.model = resolveSessionModel( resumeSession.entries );
+
 	for ( let index = resumeSession.entries.length - 1; index >= 0; index -= 1 ) {
 		const entry = resumeSession.entries[ index ];
 
-		if ( ! context.model && entry.type === 'model_change' ) {
-			const modelId = ( entry as { modelId?: unknown } ).modelId;
-			if ( typeof modelId === 'string' && isAiModelId( modelId ) ) {
-				context.model = modelId;
-			}
-		}
-
 		if ( isStudioCustomEntryOfType( entry, 'studio.session_context' ) ) {
 			const data = entry.data;
-			if ( data ) {
-				if ( ! context.provider && isAiProviderId( data.provider ) ) {
-					context.provider = data.provider;
-				}
-				if ( ! context.model && isAiModelId( data.model ) ) {
-					context.model = data.model;
-				}
+			if ( data && isAiProviderId( data.provider ) ) {
+				context.provider = data.provider;
+				break;
 			}
 		}
-
-		if ( context.sessionId && context.provider && context.model ) {
-			break;
-		}
 	}
 
 	return context;
diff --git a/tools/common/ai/models.ts b/tools/common/ai/models.ts
index 4cd20b8d86..8c8e7cd72a 100644
--- a/tools/common/ai/models.ts
+++ b/tools/common/ai/models.ts
@@ -20,8 +20,8 @@ export interface AiModel {
 // reasoning turns.
 export const AI_MODELS = [
 	{ id: 'claude-sonnet-4-6', label: 'Sonnet 4.6', family: 'anthropic' },
-	{ id: 'claude-opus-4-6', label: 'Opus 4.6', family: 'anthropic' },
 	{ id: 'claude-opus-4-7', label: 'Opus 4.7', family: 'anthropic' },
+	{ id: 'claude-opus-4-8', label: 'Opus 4.8', family: 'anthropic' },
 	{ id: 'gpt-5.5', label: 'GPT 5.5', family: 'openai' },
 ] as const satisfies readonly AiModel[];
 
@@ -58,26 +58,40 @@ export function getAiModelLabel( id: AiModelId ): string {
 	return getAiModel( id ).label;
 }
 
+/**
+ * Read the raw model id recorded on a single session entry, if any.
+ *
+ * Looks at the `model_change` entry the UI writes when the user picks a model
+ * and the `studio.session_context` payload the CLI records per turn. Returns
+ * the stored string verbatim (no validation) so callers can distinguish "no
+ * model recorded" from "a model we no longer offer".
+ */
+function readEntryModelId( entry: SessionEntry ): string | undefined {
+	if ( entry.type === 'model_change' ) {
+		const modelId = ( entry as { modelId?: unknown } ).modelId;
+		return typeof modelId === 'string' ? modelId : undefined;
+	}
+	if ( isStudioCustomEntryOfType( entry, 'studio.session_context' ) ) {
+		const model = entry.data?.model;
+		return typeof model === 'string' ? model : undefined;
+	}
+	return undefined;
+}
+
 /**
  * Derive the current model for a session from its pi entries.
  *
- * Prefers the most recent `model_change` entry (written when the user picks
- * a model from the UI) over the `studio.session_context` `customType`
- * payload that the CLI records per turn. Falls back to `DEFAULT_MODEL` for
- * sessions that have neither — e.g. a brand-new session before the first
- * turn runs.
+ * The most recently recorded model wins. If it names a model we no longer
+ * offer (e.g. one that was removed from `AI_MODELS`), the session
+ * auto-switches to `DEFAULT_MODEL` rather than pinning a dead id. Sessions
+ * that recorded no model — e.g. a brand-new session before the first turn
+ * runs — also fall back to `DEFAULT_MODEL`.
  */
 export function resolveSessionModel( entries: SessionEntry[] ): AiModelId {
 	for ( let index = entries.length - 1; index >= 0; index -= 1 ) {
-		const entry = entries[ index ];
-		if ( entry.type === 'model_change' ) {
-			const modelId = ( entry as { modelId?: unknown } ).modelId;
-			if ( typeof modelId === 'string' && isAiModelId( modelId ) ) return modelId;
-		}
-		if ( isStudioCustomEntryOfType( entry, 'studio.session_context' ) ) {
-			const model = entry.data?.model;
-			if ( typeof model === 'string' && isAiModelId( model ) ) return model;
-		}
+		const recordedModel = readEntryModelId( entries[ index ] );
+		if ( recordedModel === undefined ) continue;
+		return isAiModelId( recordedModel ) ? recordedModel : DEFAULT_MODEL;
 	}
 	return DEFAULT_MODEL;
 }