diff --git a/packages/coding-agent/src/dap/config.ts b/packages/coding-agent/src/dap/config.ts
index 8827c2ac1..abeab9f86 100644
--- a/packages/coding-agent/src/dap/config.ts
+++ b/packages/coding-agent/src/dap/config.ts
@@ -87,7 +87,22 @@ function mergeAdapters(
 ): Record<string, DapAdapterConfig> {
 	const merged: Record<string, DapAdapterConfig> = { ...base };
 	for (const [name, config] of Object.entries(overrides)) {
-		const candidate = isRecord(merged[name]) && isRecord(config) ? { ...merged[name], ...config } : config;
+		const existing = merged[name];
+		const candidate =
+			isRecord(existing) && isRecord(config)
+				? {
+						...existing,
+						...config,
+						launchDefaults:
+							isRecord(existing.launchDefaults) || isRecord(config.launchDefaults)
+								? { ...existing.launchDefaults, ...normalizeObject(config.launchDefaults) }
+								: undefined,
+						attachDefaults:
+							isRecord(existing.attachDefaults) || isRecord(config.attachDefaults)
+								? { ...existing.attachDefaults, ...normalizeObject(config.attachDefaults) }
+								: undefined,
+					}
+				: config;
 		const normalized = normalizeAdapterConfig(candidate);
 		if (normalized) {
 			merged[name] = normalized;
diff --git a/packages/coding-agent/test/debug/dap-config.test.ts b/packages/coding-agent/test/debug/dap-config.test.ts
index 579ee5384..995198453 100644
--- a/packages/coding-agent/test/debug/dap-config.test.ts
+++ b/packages/coding-agent/test/debug/dap-config.test.ts
@@ -62,7 +62,7 @@ describe("DAP adapter configuration", () => {
 				adapters: {
 					debugpy: {
 						args: ["-m", "debugpy.adapter", "--log-dir", ".debugpy-logs"],
-						launchDefaults: { request: "launch", justMyCode: false },
+						launchDefaults: { justMyCode: false },
 					},
 				},
 			}),