core: fix reasoning tracking for multiple blocks per response

Enable proper handling of multiple reasoning blocks within a single assistant
response by assigning unique reasoningIDs to each block. Previously, reasoning
blocks could get mixed up when multiple reasoning steps occurred in one turn,
causing deltas and completion events to apply to the wrong block.

Author: thdxr

packages/opencode/src/session/processor.ts

@@ -226,6 +226,7 @@ export const layer: Layer.Layer<
             if (value.id in ctx.reasoningMap) return
             SyncEvent.run(SessionEvent.Reasoning.Started.Sync, {
               sessionID: ctx.sessionID,
+              reasoningID: value.id,
               timestamp: DateTime.makeUnsafe(Date.now()),
             })
             ctx.reasoningMap[value.id] = {
@@ -242,6 +243,12 @@ export const layer: Layer.Layer<
 
           case "reasoning-delta":
             if (!(value.id in ctx.reasoningMap)) return
+            SyncEvent.run(SessionEvent.Reasoning.Delta.Sync, {
+              sessionID: ctx.sessionID,
+              reasoningID: value.id,
+              delta: value.text,
+              timestamp: DateTime.makeUnsafe(Date.now()),
+            })
             ctx.reasoningMap[value.id].text += value.text
             if (value.providerMetadata) ctx.reasoningMap[value.id].metadata = value.providerMetadata
             yield* session.updatePartDelta({
@@ -257,6 +264,7 @@ export const layer: Layer.Layer<
             if (!(value.id in ctx.reasoningMap)) return
             SyncEvent.run(SessionEvent.Reasoning.Ended.Sync, {
               sessionID: ctx.sessionID,
+              reasoningID: value.id,
               text: ctx.reasoningMap[value.id].text,
               timestamp: DateTime.makeUnsafe(Date.now()),
             })

packages/opencode/src/v2/session-entry-stepper.ts

@@ -60,8 +60,10 @@ export function stepWith<Result>(adapter: Adapter<Result>, event: SessionEvent.E
   const latestText = (assistant: DraftAssistant | undefined) =>
     assistant?.content.findLast((item): item is DraftText => item.type === "text")
 
-  const latestReasoning = (assistant: DraftAssistant | undefined) =>
-    assistant?.content.findLast((item): item is DraftReasoning => item.type === "reasoning")
+  const latestReasoning = (assistant: DraftAssistant | undefined, reasoningID: string) =>
+    assistant?.content.findLast(
+      (item): item is DraftReasoning => item.type === "reasoning" && item.reasoningID === reasoningID,
+    )
 
   SessionEvent.All.match(event, {
     "session.next.prompted": (event) => {
@@ -203,12 +205,13 @@ export function stepWith<Result>(adapter: Adapter<Result>, event: SessionEvent.E
         )
       }
     },
-    "session.next.reasoning.started": () => {
+    "session.next.reasoning.started": (event) => {
       if (currentAssistant) {
         adapter.updateAssistant(
           produce(currentAssistant, (draft) => {
             draft.content.push({
               type: "reasoning",
+              reasoningID: event.data.reasoningID,
               text: "",
             })
           }),
@@ -219,7 +222,7 @@ export function stepWith<Result>(adapter: Adapter<Result>, event: SessionEvent.E
       if (currentAssistant) {
         adapter.updateAssistant(
           produce(currentAssistant, (draft) => {
-            const match = latestReasoning(draft)
+            const match = latestReasoning(draft, event.data.reasoningID)
             if (match) match.text += event.data.delta
           }),
         )
@@ -229,7 +232,7 @@ export function stepWith<Result>(adapter: Adapter<Result>, event: SessionEvent.E
       if (currentAssistant) {
         adapter.updateAssistant(
           produce(currentAssistant, (draft) => {
-            const match = latestReasoning(draft)
+            const match = latestReasoning(draft, event.data.reasoningID)
             if (match) match.text = event.data.text
           }),
         )

packages/opencode/src/v2/session-entry.ts

@@ -107,6 +107,7 @@ export class AssistantText extends Schema.Class<AssistantText>("Session.Entry.As
 
 export class AssistantReasoning extends Schema.Class<AssistantReasoning>("Session.Entry.Assistant.Reasoning")({
   type: Schema.Literal("reasoning"),
+  reasoningID: Schema.String,
   text: Schema.String,
 }) {}
 

packages/opencode/src/v2/session-event.ts

@@ -117,6 +117,7 @@ export namespace Reasoning {
     schema: {
       timestamp: Schema.DateTimeUtcFromMillis,
       sessionID: SessionID,
+      reasoningID: Schema.String,
     },
   })
   export type Started = Schema.Schema.Type<typeof Started>
@@ -127,6 +128,7 @@ export namespace Reasoning {
     schema: {
       timestamp: Schema.DateTimeUtcFromMillis,
       sessionID: SessionID,
+      reasoningID: Schema.String,
       delta: Schema.String,
     },
   })
@@ -138,6 +140,7 @@ export namespace Reasoning {
     schema: {
       timestamp: Schema.DateTimeUtcFromMillis,
       sessionID: SessionID,
+      reasoningID: Schema.String,
       text: Schema.String,
     },
   })