diff --git a/packages/coding-agent/test/agent-session-plan-reference-compaction.test.ts b/packages/coding-agent/test/agent-session-plan-reference-compaction.test.ts
index 00705619d..2885fc6e5 100644
--- a/packages/coding-agent/test/agent-session-plan-reference-compaction.test.ts
+++ b/packages/coding-agent/test/agent-session-plan-reference-compaction.test.ts
@@ -133,8 +133,13 @@ describe("AgentSession approved-plan reference re-injection after compaction (is
 			resolve: (call: ObservedPromptCall) => void;
 		}> = [];
 
-		const model = getBundledModel("anthropic", "claude-sonnet-4-5");
-		if (!model) throw new Error("Expected claude-sonnet-4-5 model to exist");
+		const bundled = getBundledModel("anthropic", "claude-sonnet-4-5");
+		if (!bundled) throw new Error("Expected claude-sonnet-4-5 model to exist");
+		// Pin the context window so the fixed 191k high-usage turn stays above the
+		// compaction threshold across catalog regenerations: claude-sonnet-4-5's
+		// bundled window grew to 1M, which a 191k turn no longer trips. Mirrors
+		// agent-session-eager-compaction / -auto-compaction-queue.
+		const model = { ...bundled, contextWindow: 200_000, maxTokens: 64_000 };
 
 		const authStorage = await AuthStorage.create(path.join(tempDir.path(), `testauth-${cleanups.length}.db`));
 		authStorage.setRuntimeApiKey("anthropic", "test-key");