diff --git a/packages/coding-agent/src/sdk.ts b/packages/coding-agent/src/sdk.ts
index bafa23800..f1e1eee94 100644
--- a/packages/coding-agent/src/sdk.ts
+++ b/packages/coding-agent/src/sdk.ts
@@ -1665,6 +1665,9 @@ export async function createAgentSession(options: CreateAgentSessionOptions = {}
 			isToolActive: name => activeToolNames.has(name),
 			setActiveToolNames,
 			hasUI: options.hasUI ?? false,
+			get additionalDirectories() {
+				return sessionManager.getAdditionalDirectories();
+			},
 			enableLsp,
 			enableIrc: restrictToolNames ? false : options.enableIrc,
 			restrictToolNames,
diff --git a/packages/coding-agent/src/task/executor.ts b/packages/coding-agent/src/task/executor.ts
index 220bd1f51..20e3f9ed3 100644
--- a/packages/coding-agent/src/task/executor.ts
+++ b/packages/coding-agent/src/task/executor.ts
@@ -287,6 +287,8 @@ function isRecord(value: unknown): value is Record<string, unknown> {
 /** Options for subagent execution */
 export interface ExecutorOptions {
 	cwd: string;
+	/** Additional workspace directories to seed on the subagent session (multi-root). */
+	additionalDirectories?: string[];
 	worktree?: string;
 	agent: AgentDefinition;
 	task: string;
@@ -2539,6 +2541,7 @@ export async function runSubprocess(options: ExecutorOptions): Promise<SingleRes
 			// artifacts dir) — only the SessionManager differs.
 			const buildSubagentSessionOptions = (sessionManagerForRun: SessionManager): CreateAgentSessionOptions => ({
 				cwd: worktree ?? cwd,
+				additionalDirectories: options.additionalDirectories,
 				authStorage,
 				modelRegistry,
 				settings: subagentSettings,
diff --git a/packages/coding-agent/src/task/structured-subagent.ts b/packages/coding-agent/src/task/structured-subagent.ts
index e8a18ea05..9cf7448df 100644
--- a/packages/coding-agent/src/task/structured-subagent.ts
+++ b/packages/coding-agent/src/task/structured-subagent.ts
@@ -371,6 +371,7 @@ function buildExecutorOptions(
 	const enableMCP = !policy.planMode && (session.enableMCP ?? true);
 	return {
 		cwd: session.cwd,
+		additionalDirectories: session.additionalDirectories,
 		agent: policy.effectiveAgent,
 		task: renderSubagentPrompt(request.assignment),
 		assignment: request.assignment.trim(),
diff --git a/packages/coding-agent/src/tools/index.ts b/packages/coding-agent/src/tools/index.ts
index 1ca56486a..90a75a80c 100644
--- a/packages/coding-agent/src/tools/index.ts
+++ b/packages/coding-agent/src/tools/index.ts
@@ -143,6 +143,8 @@ export interface DeferredDiagnosticsEntry {
 export interface ToolSession {
 	/** Current working directory */
 	cwd: string;
+	/** Additional workspace directories beyond cwd (multi-root), forwarded to subagents. */
+	additionalDirectories?: string[];
 	/** Whether UI is available */
 	hasUI: boolean;
 	/**