feat(system-prompt): add prompt:workspace_id variable

Lets the AI know which workspace it's in — especially useful when summoning
agents. Wired through the construct context in both the regular turn flow
and the compaction flow.

5 files changed, 12 insertions, 5 deletions

diff --git a/packages/session-orchestrator/src/orchestrator.ts b/packages/session-orchestrator/src/orchestrator.ts
index 5398867..7599a0c 100644
--- a/packages/session-orchestrator/src/orchestrator.ts
+++ b/packages/session-orchestrator/src/orchestrator.ts
@@ -489,6 +489,7 @@ export function createSessionOrchestrator(
 							effectiveCwd ?? process.cwd(),
 							{
 								...(modelName !== undefined ? { model: modelName } : {}),
+								...(workspaceId !== undefined ? { workspaceId } : {}),
 							},
 						);
 					} else {
@@ -952,8 +953,10 @@ export function createCompactionService(
 			let compactionSystemPrompt: string;
 			if (systemPromptService !== undefined) {
 				const cwd = (await deps.conversationStore.getEffectiveCwd(conversationId)) ?? process.cwd();
+				const workspaceId = await deps.conversationStore.getWorkspaceId(conversationId);
 				const constructed = await systemPromptService.construct(conversationId, cwd, {
 					...(opts?.modelName !== undefined ? { model: opts.modelName } : {}),
+					workspaceId,
 				});
 				compactionSystemPrompt = `${constructed}\n\n${COMPACTION_SYSTEM_PROMPT}`;
 			} else {
diff --git a/packages/system-prompt/src/catalog.ts b/packages/system-prompt/src/catalog.ts
index cfa3bb1..1c825ab 100644
--- a/packages/system-prompt/src/catalog.ts
+++ b/packages/system-prompt/src/catalog.ts
@@ -16,6 +16,7 @@ export function getVariableCatalog(): SystemPromptVariable[] {
 		{ type: "prompt", name: "cwd", description: "Conversation working directory" },
 		{ type: "prompt", name: "model", description: "Current model name" },
 		{ type: "prompt", name: "conversation_id", description: "Conversation identifier" },
+		{ type: "prompt", name: "workspace_id", description: "Workspace identifier" },
 		{ type: "git", name: "branch", description: "Current git branch" },
 		{ type: "git", name: "status", description: "Short git status" },
 		{
diff --git a/packages/system-prompt/src/resolver.ts b/packages/system-prompt/src/resolver.ts
index eed7bcb..1ef9028 100644
--- a/packages/system-prompt/src/resolver.ts
+++ b/packages/system-prompt/src/resolver.ts
@@ -55,6 +55,7 @@ export interface ResolverAdapters {
 export interface ResolverContext {
 	readonly model?: string;
 	readonly conversationId?: string;
+	readonly workspaceId?: string;
 }
 
 export interface ResolveOptions {
@@ -116,6 +117,7 @@ export async function resolveVariables(
 	vars.set("prompt:cwd", cwd);
 	vars.set("prompt:model", ctx?.model ?? null);
 	vars.set("prompt:conversation_id", ctx?.conversationId ?? null);
+	vars.set("prompt:workspace_id", ctx?.workspaceId ?? null);
 
 	// ── git:* ────────────────────────────────────────────────────────────────
 	// branch is a single value — trim fully; status keeps its leading status
diff --git a/packages/system-prompt/src/service.ts b/packages/system-prompt/src/service.ts
index 4b4436f..6fdae51 100644
--- a/packages/system-prompt/src/service.ts
+++ b/packages/system-prompt/src/service.ts
@@ -46,10 +46,11 @@ export function createSystemPromptService(deps: SystemPromptServiceDeps): System
 			if (template === null) template = DEFAULT_TEMPLATE;
 
 			const referencedKeys = extractVariables(template);
-			const resolverContext: ResolverContext =
-				context?.model !== undefined
-					? { model: context.model, conversationId }
-					: { conversationId };
+			const resolverContext: ResolverContext = {
+				conversationId,
+				...(context?.model !== undefined ? { model: context.model } : {}),
+				...(context?.workspaceId !== undefined ? { workspaceId: context.workspaceId } : {}),
+			};
 			const vars = await resolveVariables(cwd, deps.adapters, {
 				context: resolverContext,
 				referencedKeys,
diff --git a/packages/system-prompt/src/types.ts b/packages/system-prompt/src/types.ts
index dd6aa69..2690355 100644
--- a/packages/system-prompt/src/types.ts
+++ b/packages/system-prompt/src/types.ts
@@ -24,7 +24,7 @@ export interface SystemPromptService {
 	construct(
 		conversationId: string,
 		cwd: string,
-		context?: { readonly model?: string },
+		context?: { readonly model?: string; readonly workspaceId?: string },
 	): Promise<string>;
 
 	/** Read the persisted resolved system prompt, or `null` if never constructed. */