feat(desktop): per-message usage stats UI (tokens, cost, TTFT, tok/s) (#10210)

Co-authored-by: Douwe M Osinga <douwe@sidewalklabs.com>

ui/sdk/src/generated/types.gen.ts

@@ -2533,7 +2533,9 @@ export type GooseSessionUpdate = ({
     sessionUpdate: 'usage_update';
 } & SessionUsageUpdate) | ({
     sessionUpdate: 'status_message';
-} & StatusMessageUpdate);
+} & StatusMessageUpdate) | ({
+    sessionUpdate: 'message_usage';
+} & MessageUsageUpdate);
 
 /**
  * Streaming context-window usage update for a session.
@@ -2562,6 +2564,43 @@ export type StatusMessageUpdate = {
     status: StatusMessage;
 };
 
+/**
+ * Wire mirror of the conversation `MessageUsage` (this crate cannot depend on
+ * goose-provider-types); field names and serde casing MUST stay in parity.
+ */
+export type MessageUsageData = {
+    inputTokens?: number | null;
+    outputTokens?: number | null;
+    totalTokens?: number | null;
+    cacheReadTokens?: number | null;
+    cacheWriteTokens?: number | null;
+    cost?: number | null;
+    costSource?: CostSourceData | null;
+    /**
+     * Wall-clock generation time, used by the client for a tokens/sec readout.
+     */
+    elapsedMs?: number | null;
+    timeToFirstTokenMs?: number | null;
+    /**
+     * Usage from a compaction/summarization call rather than a normal turn.
+     */
+    isCompaction?: boolean;
+};
+
+/**
+ * Wire mirror of the conversation `CostSource`.
+ */
+export type CostSourceData = 'provider_reported' | 'estimated';
+
+/**
+ * Per-message token usage/cost/timing, keyed by the message id used for
+ * chunk matching. Sent live after a turn's messages and on replay.
+ */
+export type MessageUsageUpdate = {
+    messageId?: string | null;
+    usage: MessageUsageData;
+};
+
 export type RequestRecipeParams_unstable = {
     sessionId: string;
     parameters: Array<RecipeParameterDto>;

ui/sdk/src/generated/zod.gen.ts

@@ -2698,6 +2698,70 @@ export const zStatusMessageUpdate = z.object({
     status: zStatusMessage
 });
 
+/**
+ * Wire mirror of the conversation `CostSource`.
+ */
+export const zCostSourceData = z.union([
+    z.literal('provider_reported'),
+    z.literal('estimated')
+]);
+
+/**
+ * Wire mirror of the conversation `MessageUsage` (this crate cannot depend on
+ * goose-provider-types); field names and serde casing MUST stay in parity.
+ */
+export const zMessageUsageData = z.object({
+    inputTokens: z.union([
+        z.number().int(),
+        z.null()
+    ]).optional(),
+    outputTokens: z.union([
+        z.number().int(),
+        z.null()
+    ]).optional(),
+    totalTokens: z.union([
+        z.number().int(),
+        z.null()
+    ]).optional(),
+    cacheReadTokens: z.union([
+        z.number().int(),
+        z.null()
+    ]).optional(),
+    cacheWriteTokens: z.union([
+        z.number().int(),
+        z.null()
+    ]).optional(),
+    cost: z.union([
+        z.number(),
+        z.null()
+    ]).optional(),
+    costSource: z.union([
+        zCostSourceData,
+        z.null()
+    ]).optional(),
+    elapsedMs: z.union([
+        z.number().int().gte(0),
+        z.null()
+    ]).optional(),
+    timeToFirstTokenMs: z.union([
+        z.number().int().gte(0),
+        z.null()
+    ]).optional(),
+    isCompaction: z.boolean().optional().default(false)
+});
+
+/**
+ * Per-message token usage/cost/timing, keyed by the message id used for
+ * chunk matching. Sent live after a turn's messages and on replay.
+ */
+export const zMessageUsageUpdate = z.object({
+    messageId: z.union([
+        z.string(),
+        z.null()
+    ]).optional(),
+    usage: zMessageUsageData
+});
+
 /**
  * Discriminated union of goose-specific session update payloads.
  * Variant tag matches ACP's convention (`sessionUpdate: "<snake_case>"`).
@@ -2712,7 +2776,10 @@ export const zGooseSessionUpdate = z.union([
     }).and(zSessionUsageUpdate),
     z.object({
         sessionUpdate: z.literal('status_message')
-    }).and(zStatusMessageUpdate)
+    }).and(zStatusMessageUpdate),
+    z.object({
+        sessionUpdate: z.literal('message_usage')
+    }).and(zMessageUsageUpdate)
 ]);
 
 /**