feat(core/cli): expose model thinking events in --output-format stream-json

docs/reference/configuration.md

@@ -1558,7 +1558,10 @@ for that specific session.
   - **Values:**
     - `text`: (Default) The standard human-readable output.
     - `json`: A machine-readable JSON output.
-    - `stream-json`: A streaming JSON output that emits real-time events.
+    - `stream-json`: A streaming JSON output that emits real-time JSONL events.
+      Event types include: `init`, `message`, `thinking`, `tool_use`,
+      `tool_result`, `error`, and `result`. The `thinking` event exposes model
+      reasoning from thinking-capable models (for example, Gemini 2.5 Pro).
   - **Note:** For structured output and scripting, use the
     `--output-format json` or `--output-format stream-json` flag.
 - **`--sandbox`** (**`-s`**):

packages/cli/src/nonInteractiveCli.ts

@@ -314,7 +314,24 @@ export async function runNonInteractive({
             handleCancellationError(config);
           }
 
-          if (event.type === GeminiEventType.Content) {
+          if (event.type === GeminiEventType.Thought) {
+            if (streamFormatter) {
+              const isRaw =
+                config.getRawOutput() || config.getAcceptRawOutputRisk();
+              const subject = isRaw
+                ? event.value.subject || undefined
+                : stripAnsi(event.value.subject) || undefined;
+              const description = isRaw
+                ? event.value.description
+                : stripAnsi(event.value.description);
+              streamFormatter.emitEvent({
+                type: JsonStreamEventType.THINKING,
+                timestamp: new Date().toISOString(),
+                description,
+                subject,
+              });
+            }
+          } else if (event.type === GeminiEventType.Content) {
             const isRaw =
               config.getRawOutput() || config.getAcceptRawOutputRisk();
             const output = isRaw ? event.value : stripAnsi(event.value);

packages/core/src/output/types.ts

@@ -29,6 +29,7 @@ export interface JsonOutput {
 export enum JsonStreamEventType {
   INIT = 'init',
   MESSAGE = 'message',
+  THINKING = 'thinking',
   TOOL_USE = 'tool_use',
   TOOL_RESULT = 'tool_result',
   ERROR = 'error',
@@ -53,6 +54,12 @@ export interface MessageEvent extends BaseJsonStreamEvent {
   delta?: boolean;
 }
 
+export interface ThinkingEvent extends BaseJsonStreamEvent {
+  type: JsonStreamEventType.THINKING;
+  description: string;
+  subject?: string;
+}
+
 export interface ToolUseEvent extends BaseJsonStreamEvent {
   type: JsonStreamEventType.TOOL_USE;
   tool_name: string;
@@ -110,6 +117,7 @@ export interface ResultEvent extends BaseJsonStreamEvent {
 export type JsonStreamEvent =
   | InitEvent
   | MessageEvent
+  | ThinkingEvent
   | ToolUseEvent
   | ToolResultEvent
   | ErrorEvent