Rewind chat or files from any user message (#1154)

* Add Pi extension-launch plumbing for in-process tree primitives

* Add Rewind controls for agent sessions

* Preserve SDK checkpoint env var so Claude file rewind works

The SDK injects CLAUDE_CODE_ENABLE_SDK_FILE_CHECKPOINTING=true when file checkpointing is enabled. The earlier parent-env stripping from c4782ec71c was too broad and removed that child flag along with real parent-session markers.

Keep stripping parent markers, but preserve the checkpoint flag so the SDK rewind path can run directly. With that boundary fixed, the JSONL file-rewind fallback is no longer needed.

* Update OpenCode history replay tests for rewind state

* Show Rewind actions in an adaptive sheet

* Fix rewind semantics across providers

* Refactor Pi IDs through extension capture

* Restore user message to composer after rewind

* Fix Claude rewind tool result mapping

* Fix Claude rewind session switch roundtrip

* Fix rewind and optimistic message regressions

* Tighten rewind test discipline

* Fix OpenCode optimistic message reconciliation

* Reconcile optimistic user messages by marker

* Reorder user message actions

* Unify provider user message contract

* Add Claude rewind flow Playwright contract

* Add Codex rewind flow Playwright contract

* Add OpenCode rewind flow Playwright contract

* Add Pi rewind flow Playwright contract

* Remove real-provider rewind Playwright contracts

* Gate real-provider rewind specs from CI Playwright

packages/server/src/shared/messages.ts

@@ -232,6 +232,12 @@ const AgentCapabilityFlagsSchema: z.ZodType<AgentCapabilityFlags> = z.object({
   supportsMcpServers: z.boolean(),
   supportsReasoningStream: z.boolean(),
   supportsToolInvocations: z.boolean(),
+  // COMPAT(rewind): added in v0.1.X, drop when floor >= v0.1.X.
+  supportsRewindConversation: z.boolean().optional().default(false),
+  // COMPAT(rewind): added in v0.1.X, drop when floor >= v0.1.X.
+  supportsRewindFiles: z.boolean().optional().default(false),
+  // COMPAT(rewind): added in v0.1.X, drop when floor >= v0.1.X.
+  supportsRewindBoth: z.boolean().optional().default(false),
 });
 
 const AgentUsageSchema: z.ZodType<AgentUsage> = z.object({
@@ -1246,6 +1252,26 @@ export const SetAgentFeatureResponseMessageSchema = z.object({
   payload: AgentActionResponsePayloadSchema,
 });
 
+export const AgentRewindModeSchema = z.enum(["conversation", "files", "both"]);
+
+export const AgentRewindRequestMessageSchema = z.object({
+  type: z.literal("agent.rewind.request"),
+  agentId: z.string(),
+  messageId: z.string(),
+  mode: AgentRewindModeSchema,
+  requestId: z.string(),
+});
+
+export const AgentRewindResponseMessageSchema = z.object({
+  type: z.literal("agent.rewind.response"),
+  payload: z.object({
+    requestId: z.string(),
+    agentId: z.string(),
+    ok: z.boolean(),
+    error: z.string().nullable(),
+  }),
+});
+
 export const UpdateAgentResponseMessageSchema = z.object({
   type: z.literal("update_agent_response"),
   payload: AgentActionResponsePayloadSchema,
@@ -1854,6 +1880,7 @@ export const SessionInboundMessageSchema = z.discriminatedUnion("type", [
   SetAgentModelRequestMessageSchema,
   SetAgentThinkingRequestMessageSchema,
   SetAgentFeatureRequestMessageSchema,
+  AgentRewindRequestMessageSchema,
   AgentPermissionResponseMessageSchema,
   CheckoutStatusRequestSchema,
   SubscribeCheckoutDiffRequestSchema,
@@ -2095,6 +2122,8 @@ export const ServerInfoStatusPayloadSchema = z
         daemonStatusRpc: z.boolean().optional(),
         // COMPAT(terminalRestoreModes): added in v0.1.81, remove gate after 2026-11-23.
         "terminal-restore-modes": z.boolean().optional(),
+        // COMPAT(rewind): added in v0.1.X, drop the gate when floor >= v0.1.X.
+        rewind: z.boolean().optional(),
       })
       .optional(),
   })
@@ -3624,6 +3653,7 @@ export const SessionOutboundMessageSchema = z.discriminatedUnion("type", [
   SetAgentModelResponseMessageSchema,
   SetAgentThinkingResponseMessageSchema,
   SetAgentFeatureResponseMessageSchema,
+  AgentRewindResponseMessageSchema,
   UpdateAgentResponseMessageSchema,
   ProjectRenameResponseSchema,
   WaitForFinishResponseMessageSchema,
@@ -3763,6 +3793,7 @@ export type SetAgentModeResponseMessage = z.infer<typeof SetAgentModeResponseMes
 export type SetAgentModelResponseMessage = z.infer<typeof SetAgentModelResponseMessageSchema>;
 export type SetAgentThinkingResponseMessage = z.infer<typeof SetAgentThinkingResponseMessageSchema>;
 export type SetAgentFeatureResponseMessage = z.infer<typeof SetAgentFeatureResponseMessageSchema>;
+export type AgentRewindResponseMessage = z.infer<typeof AgentRewindResponseMessageSchema>;
 export type UpdateAgentResponseMessage = z.infer<typeof UpdateAgentResponseMessageSchema>;
 export type ProjectRenameResponse = z.infer<typeof ProjectRenameResponseSchema>;
 export type ProjectRenameResponsePayload = z.infer<typeof ProjectRenameResponsePayloadSchema>;