2 files changed, 22 insertions, 10 deletions

diff --git a/packages/session-orchestrator/src/orchestrator.test.ts b/packages/session-orchestrator/src/orchestrator.test.ts
index 8ff3f5e..654c0c3 100644
--- a/packages/session-orchestrator/src/orchestrator.test.ts
+++ b/packages/session-orchestrator/src/orchestrator.test.ts
@@ -3611,12 +3611,13 @@ function createFakeSystemPromptService(
 	constructImpl: (
 		conversationId: string,
 		cwd: string,
-		context?: { readonly model?: string },
+		context?: { readonly model?: string; readonly computerId?: string },
 	) => Promise<string>,
-	getWithMetaImpl: (
-		conversationId: string,
-	) => Promise<{ readonly prompt: string | null; readonly cwd: string | null }> = () =>
-		Promise.resolve({ prompt: null, cwd: null }),
+	getWithMetaImpl: (conversationId: string) => Promise<{
+		readonly prompt: string | null;
+		readonly cwd: string | null;
+		readonly computerId: string | null;
+	}> = () => Promise.resolve({ prompt: null, cwd: null, computerId: null }),
 ): SystemPromptService {
 	return {
 		construct: constructImpl,
@@ -3663,7 +3664,7 @@ describe("system prompt: regular turn flow", () => {
 					},
 					async (conversationId) => {
 						getCalls.push(conversationId);
-						return null;
+						return { prompt: null, cwd: null, computerId: null };
 					},
 				),
 		});
@@ -3714,7 +3715,7 @@ describe("system prompt: regular turn flow", () => {
 					},
 					async (conversationId) => {
 						getWithMetaCalls.push(conversationId);
-						return { prompt: "PERSISTED_PROMPT", cwd: "/work/dir" };
+						return { prompt: "PERSISTED_PROMPT", cwd: "/work/dir", computerId: null };
 					},
 				),
 		});
@@ -3762,7 +3763,7 @@ describe("system prompt: regular turn flow", () => {
 						constructCalls.push({ conversationId, cwd, model: context?.model });
 						return "RECONSTRUCTED_PROMPT";
 					},
-					async () => ({ prompt: null, cwd: null }),
+					async () => ({ prompt: null, cwd: null, computerId: null }),
 				),
 		});
 
@@ -3815,7 +3816,7 @@ describe("system prompt: regular turn flow", () => {
 					async (conversationId) => {
 						getWithMetaCalls.push(conversationId);
 						// Stored prompt was built against an OLD cwd.
-						return { prompt: "STALE_PROMPT", cwd: "/old/dir" };
+						return { prompt: "STALE_PROMPT", cwd: "/old/dir", computerId: null };
 					},
 				),
 		});
diff --git a/packages/session-orchestrator/src/orchestrator.ts b/packages/session-orchestrator/src/orchestrator.ts
index a1401d6..4aa77f7 100644
--- a/packages/session-orchestrator/src/orchestrator.ts
+++ b/packages/session-orchestrator/src/orchestrator.ts
@@ -619,17 +619,26 @@ export function createSessionOrchestrator(
 							{
 								...(effectiveModelName !== undefined ? { model: effectiveModelName } : {}),
 								...(workspaceId !== undefined ? { workspaceId } : {}),
+								...(effectiveComputerId !== undefined ? { computerId: effectiveComputerId } : {}),
 							},
 						);
 					} else {
 						const meta = await systemPromptService.getWithMeta(conversationId);
 						const currentCwd = effectiveCwd ?? process.cwd();
-						if (meta.prompt !== null && meta.cwd === currentCwd) {
+						const currentComputerId = effectiveComputerId ?? null;
+						// Invalidate when cwd OR computerId changed (switching computers
+						// must rebuild the prompt against the remote OS/hostname).
+						if (
+							meta.prompt !== null &&
+							meta.cwd === currentCwd &&
+							meta.computerId === currentComputerId
+						) {
 							systemPrompt = meta.prompt;
 						} else {
 							systemPrompt = await systemPromptService.construct(conversationId, currentCwd, {
 								...(effectiveModelName !== undefined ? { model: effectiveModelName } : {}),
 								...(workspaceId !== undefined ? { workspaceId } : {}),
+								...(effectiveComputerId !== undefined ? { computerId: effectiveComputerId } : {}),
 							});
 						}
 					}
@@ -1122,9 +1131,11 @@ export function createCompactionService(
 			if (systemPromptService !== undefined) {
 				const cwd = (await deps.conversationStore.getEffectiveCwd(conversationId)) ?? process.cwd();
 				const workspaceId = await deps.conversationStore.getWorkspaceId(conversationId);
+				const computerId = await deps.conversationStore.getEffectiveComputer(conversationId);
 				const constructed = await systemPromptService.construct(conversationId, cwd, {
 					...(opts?.modelName !== undefined ? { model: opts.modelName } : {}),
 					workspaceId,
+					...(computerId !== null ? { computerId } : {}),
 				});
 				compactionSystemPrompt = `${constructed}\n\n${COMPACTION_SYSTEM_PROMPT}`;
 			} else {