Fork assistant turns into new drafts (#1788)

* feat(chat): fork assistant turns into new drafts

Builds chat-history attachments on the daemon and routes them into draft composers so users can continue an assistant turn in an existing workspace tab or New Workspace.

* fix(chat): clean up fork draft handling

* fix(chat): address fork draft review feedback

* fix(server): build fork context from bounded timeline

* fix(app): restore assistant turn footer in streams

* fix(app): preserve fork draft setup

* fix(app): tighten assistant fork footers

* fix(app): lock active fork draft handoff

* fix(app): preserve attachment-only draft retries

* fix(app): unify composer attachment scopes

* fix(app): align chat history attachment labels

* fix(app): centralize attachment pill content

* fix(app): trim fork context for workspace naming

packages/protocol/src/messages.attachments.test.ts

@@ -226,6 +226,47 @@ describe("shared messages attachments", () => {
     ]);
   });
 
+  it("keeps known text attachment context kinds and ignores future ones", () => {
+    const parsed = SendAgentMessageRequestSchema.parse({
+      type: "send_agent_message_request",
+      requestId: "req-text-context",
+      agentId: "agent-1",
+      text: "Continue",
+      attachments: [
+        {
+          type: "text",
+          mimeType: "text/plain",
+          contextKind: "chat_history",
+          title: "Chat history",
+          text: "Earlier context",
+        },
+        {
+          type: "text",
+          mimeType: "text/plain",
+          contextKind: "future_context",
+          title: "Future context",
+          text: "Future client hint",
+        },
+      ],
+    });
+
+    expect(parsed.attachments).toEqual([
+      {
+        type: "text",
+        mimeType: "text/plain",
+        contextKind: "chat_history",
+        title: "Chat history",
+        text: "Earlier context",
+      },
+      {
+        type: "text",
+        mimeType: "text/plain",
+        title: "Future context",
+        text: "Future client hint",
+      },
+    ]);
+  });
+
   it("keeps known firstAgentContext attachments and drops unknown ones", () => {
     const parsed = CreatePaseoWorktreeRequestSchema.parse({
       type: "create_paseo_worktree_request",

packages/protocol/src/messages.ts

@@ -843,12 +843,18 @@ export const GitHubIssueAttachmentSchema = z.object({
   body: z.string().nullable().optional(),
 });
 
-export const TextAttachmentSchema = z.object({
-  type: z.literal("text"),
-  mimeType: z.literal("text/plain"),
-  title: z.string().nullable().optional(),
-  text: z.string(),
-});
+export const TextAttachmentSchema = z
+  .object({
+    type: z.literal("text"),
+    mimeType: z.literal("text/plain"),
+    contextKind: z.string().optional(),
+    title: z.string().nullable().optional(),
+    text: z.string(),
+  })
+  .transform(({ contextKind, ...attachment }) => ({
+    ...attachment,
+    ...(contextKind === "chat_history" ? { contextKind } : {}),
+  }));
 
 export const ReviewAttachmentContextLineSchema = z.object({
   oldLineNumber: z.number().int().positive().nullable(),
@@ -1274,6 +1280,13 @@ export const FetchAgentTimelineRequestMessageSchema = z.object({
   projection: z.enum(["projected", "canonical"]).optional(),
 });
 
+export const AgentForkContextRequestMessageSchema = z.object({
+  type: z.literal("agent.fork_context.request"),
+  agentId: z.string(),
+  boundaryMessageId: z.string().optional(),
+  requestId: z.string(),
+});
+
 export const SetAgentModeRequestMessageSchema = z.object({
   type: z.literal("set_agent_mode_request"),
   agentId: z.string(),
@@ -2060,6 +2073,7 @@ export const SessionInboundMessageSchema = z.discriminatedUnion("type", [
   RestartServerRequestMessageSchema,
   DaemonUpdateRequestMessageSchema,
   FetchAgentTimelineRequestMessageSchema,
+  AgentForkContextRequestMessageSchema,
   SetAgentModeRequestMessageSchema,
   SetAgentModelRequestMessageSchema,
   SetAgentThinkingRequestMessageSchema,
@@ -2335,6 +2349,8 @@ export const ServerInfoStatusPayloadSchema = z
         daemonDiagnostics: z.boolean().optional(),
         // COMPAT(daemonSelfUpdate): added in v0.1.93, remove gate after 2026-12-13.
         daemonSelfUpdate: z.boolean().optional(),
+        // COMPAT(agentForkContext): added in v0.1.102, remove gate after 2026-12-28.
+        agentForkContext: z.boolean().optional(),
       })
       .optional(),
   })
@@ -2926,6 +2942,18 @@ export const FetchAgentTimelineResponseMessageSchema = z.object({
   }),
 });
 
+export const AgentForkContextResponseMessageSchema = z.object({
+  type: z.literal("agent.fork_context.response"),
+  payload: z.object({
+    requestId: z.string(),
+    agentId: z.string(),
+    attachment: TextAttachmentSchema.nullable(),
+    itemCount: z.number().int().nonnegative(),
+    boundaryMessageId: z.string().nullable(),
+    error: z.string().nullable(),
+  }),
+});
+
 export const CancelAgentResponseMessageSchema = z.object({
   type: z.literal("cancel_agent_response"),
   payload: z.object({
@@ -4158,6 +4186,7 @@ export const SessionOutboundMessageSchema = z.discriminatedUnion("type", [
   ArchiveWorkspaceResponseMessageSchema,
   FetchAgentResponseMessageSchema,
   FetchAgentTimelineResponseMessageSchema,
+  AgentForkContextResponseMessageSchema,
   CancelAgentResponseMessageSchema,
   ClearAgentAttentionResponseMessageSchema,
   WorkspaceCreateResponseSchema,
@@ -4320,6 +4349,7 @@ export type FetchAgentResponseMessage = z.infer<typeof FetchAgentResponseMessage
 export type FetchAgentTimelineResponseMessage = z.infer<
   typeof FetchAgentTimelineResponseMessageSchema
 >;
+export type AgentForkContextResponseMessage = z.infer<typeof AgentForkContextResponseMessageSchema>;
 export type CancelAgentResponseMessage = z.infer<typeof CancelAgentResponseMessageSchema>;
 export type SendAgentMessageResponseMessage = z.infer<typeof SendAgentMessageResponseMessageSchema>;
 export type SetVoiceModeResponseMessage = z.infer<typeof SetVoiceModeResponseMessageSchema>;
@@ -4410,6 +4440,7 @@ export type FetchRecentProviderSessionsRequestMessage = z.infer<
 >;
 export type FetchWorkspacesRequestMessage = z.infer<typeof FetchWorkspacesRequestMessageSchema>;
 export type FetchAgentRequestMessage = z.infer<typeof FetchAgentRequestMessageSchema>;
+export type AgentForkContextRequestMessage = z.infer<typeof AgentForkContextRequestMessageSchema>;
 export type SendAgentMessageRequest = z.infer<typeof SendAgentMessageRequestSchema>;
 export type WaitForFinishRequest = z.infer<typeof WaitForFinishRequestSchema>;
 export type DictationStreamStartMessage = z.infer<typeof DictationStreamStartMessageSchema>;