feat: stream shell tool output (#676)

2026-07-10 01:39:25 +00:00 · 2026-06-12 11:10:20 +08:00 · 2026-06-12 11:10:20 +08:00 · dcf30754d0
commit dcf30754d0
parent 0a3e87f05a
16 changed files with 204 additions and 13 deletions
--- a/.changeset/shell-streaming-output.md
+++ b/.changeset/shell-streaming-output.md
@ -0,0 +1,6 @@
+---
+"@moonshot-ai/agent-core": patch
+"@moonshot-ai/kimi-code": patch
+---
+
+Stream foreground Bash stdout and stderr while commands are still running.
--- a/apps/kimi-code/src/tui/components/messages/shell-execution.ts
+++ b/apps/kimi-code/src/tui/components/messages/shell-execution.ts
@ -20,6 +20,8 @@ export interface ShellExecutionOptions {
   */
  readonly commandPreviewLines?: number;
  readonly resultPreviewLines?: number;
+  readonly tailOutput?: boolean;
+  readonly expandHint?: boolean;
 }

 export class ShellExecutionComponent extends Container {
@ -35,6 +37,8 @@ export class ShellExecutionComponent extends Container {
        options.result,
        options.expanded ?? false,
        options.resultPreviewLines ?? PREVIEW_LINES,
+        options.tailOutput ?? false,
+        options.expandHint ?? true,
      );
    }
  }
@ -53,6 +57,8 @@ export class ShellExecutionComponent extends Container {
    result: ToolResultBlockData,
    expanded: boolean,
    previewLines: number,
+    tailOutput: boolean,
+    expandHint: boolean,
  ): void {
    if (!result.output) return;
    this.addChild(
@ -60,6 +66,8 @@ export class ShellExecutionComponent extends Container {
        expanded,
        isError: result.is_error ?? false,
        maxLines: previewLines,
+        tail: tailOutput,
+        expandHint,
      }),
    );
  }
--- a/apps/kimi-code/src/tui/components/messages/tool-call.ts
+++ b/apps/kimi-code/src/tui/components/messages/tool-call.ts
@ -44,6 +44,7 @@ const STREAMING_PROGRESS_INTERVAL_MS = 1000;
 const SUBAGENT_ELAPSED_INTERVAL_MS = 1000;
 const PROGRESS_URL_RE = /https?:\/\/\S+/g;
 const ABORTED_MARK = '⊘';
+const MAX_LIVE_OUTPUT_CHARS = 50_000;

 type SubagentTextKind = 'thinking' | 'text';
 type SubagentPhase = 'queued' | 'spawning' | 'running' | 'done' | 'failed' | 'backgrounded';
@ -557,6 +558,7 @@ export class ToolCallComponent extends Container {
  // authoritative final state.
  private progressLines: string[] = [];
  private static readonly MAX_PROGRESS_LINES = 24;
+  private liveOutput = '';

  /**
   * Registered by a group container (`AgentGroupComponent` or
@ -586,6 +588,7 @@ export class ToolCallComponent extends Container {
    this.buildCallPreview();
    this.callPreviewEndIndex = this.children.length;
    this.buildProgressBlock();
+    this.buildLiveOutputBlock();
    this.buildContent();
    this.buildSubagentBlock();
    this.syncStreamingProgressTimer();
@ -615,6 +618,7 @@ export class ToolCallComponent extends Container {
    // authoritative final state. Without this clear, a finished tool would
    // show both the streamed status lines and the final output stacked.
    this.progressLines = [];
+    this.liveOutput = '';
    this.finalizeSubagentElapsedIfNeeded();
    this.syncStreamingProgressTimer();
    this.syncSubagentElapsedTimer();
@ -657,6 +661,19 @@ export class ToolCallComponent extends Container {
    this.ui?.requestRender();
  }

+  appendLiveOutput(text: string): void {
+    if (this.result !== undefined || text.length === 0) return;
+    this.liveOutput += text;
+    if (this.liveOutput.length > MAX_LIVE_OUTPUT_CHARS) {
+      this.liveOutput = `[...truncated]\n${this.liveOutput.slice(
+        this.liveOutput.length - MAX_LIVE_OUTPUT_CHARS,
+      )}`;
+    }
+    this.rebuildContent();
+    this.notifySnapshotChange();
+    this.ui?.requestRender();
+  }
+
  dispose(): void {
    this.stopStreamingProgressTimer();
    this.stopSubagentElapsedTimer();
@ -1179,6 +1196,24 @@ export class ToolCallComponent extends Container {
    this.ui?.requestRender();
  }

+  appendSubToolLiveOutput(id: string, text: string): void {
+    if (text.length === 0) return;
+    const activity = this.subToolActivities.get(id);
+    const ongoing = this.ongoingSubCalls.get(id);
+    if (activity === undefined && ongoing === undefined) return;
+    const name = activity?.name ?? ongoing?.name ?? 'Tool';
+    const args = activity?.args ?? ongoing?.args ?? {};
+    const existingOutput = activity?.output ?? '';
+    let output = existingOutput + text;
+    if (output.length > MAX_LIVE_OUTPUT_CHARS) {
+      output = `[...truncated]\n${output.slice(output.length - MAX_LIVE_OUTPUT_CHARS)}`;
+    }
+    this.upsertSubToolActivity(id, name, args, activity?.phase ?? 'ongoing', output);
+    this.rebuildContent();
+    this.notifySnapshotChange();
+    this.ui?.requestRender();
+  }
+
  finishSubToolCall(result: {
    tool_call_id: string;
    output: string;
@ -1300,6 +1335,7 @@ export class ToolCallComponent extends Container {
      this.children.pop();
    }
    this.buildProgressBlock();
+    this.buildLiveOutputBlock();
    this.buildContent();
    this.buildSubagentBlock();
  }
@ -1311,6 +1347,7 @@ export class ToolCallComponent extends Container {
    this.buildCallPreview();
    this.callPreviewEndIndex = this.children.length;
    this.buildProgressBlock();
+    this.buildLiveOutputBlock();
    this.buildContent();
    this.buildSubagentBlock();
  }
@ -1345,6 +1382,24 @@ export class ToolCallComponent extends Container {
    }
  }

+  private buildLiveOutputBlock(): void {
+    if (this.result !== undefined) return;
+    if (this.liveOutput.length === 0) return;
+    this.addChild(
+      new ShellExecutionComponent({
+        result: {
+          tool_call_id: this.toolCall.id,
+          output: this.liveOutput,
+          is_error: false,
+        },
+        expanded: this.expanded,
+        resultPreviewLines: RESULT_PREVIEW_LINES,
+        tailOutput: true,
+        expandHint: false,
+      }),
+    );
+  }
+
  private buildSubagentBlock(): void {
    if (
      this.subagentAgentId === undefined &&
@ -1612,7 +1667,6 @@ export class ToolCallComponent extends Container {
  }

  private addSubToolOutputPreview(activity: SubToolActivity): void {
-    if (activity.phase === 'ongoing') return;
    const output = activity.output;
    if (output === undefined || output.trim().length === 0) return;
    // Mirror the main agent: Bash and any tool without a dedicated renderer
@ -1628,6 +1682,7 @@ export class ToolCallComponent extends Container {
        isError: activity.phase === 'failed',
        maxLines: RESULT_PREVIEW_LINES,
        indent: SUBAGENT_SUBTOOL_OUTPUT_INDENT,
+        tail: activity.phase === 'ongoing',
      }),
    );
  }
--- a/apps/kimi-code/src/tui/components/messages/tool-renderers/truncated.ts
+++ b/apps/kimi-code/src/tui/components/messages/tool-renderers/truncated.ts
@ -30,6 +30,7 @@ export class TruncatedOutputComponent implements Component {
  private readonly maxLines: number;
  private readonly indent: number;
  private readonly expandHint: boolean;
+  private readonly tail: boolean;

  constructor(
    output: string,
@ -41,12 +42,16 @@ export class TruncatedOutputComponent implements Component {
      // When false, the truncation footer omits the "ctrl+o to expand" promise
      // (for contexts whose output is fixed-truncated and never expands).
      expandHint?: boolean;
+      // When true, collapsed rendering keeps the latest visual rows instead of
+      // the first rows. This is useful for live output from a running command.
+      tail?: boolean;
    },
  ) {
    this.expanded = options.expanded;
    this.maxLines = options.maxLines ?? PREVIEW_LINES;
    this.indent = options.indent ?? DEFAULT_INDENT;
    this.expandHint = options.expandHint ?? true;
+    this.tail = options.tail ?? false;
    const cleaned = trimTrailingEmptyLines(output.split('\n')).join('\n');
    this.textComponent = new Text(
      options.isError ? currentTheme.fg('error', cleaned) : currentTheme.dim(cleaned),
@ -67,8 +72,16 @@ export class TruncatedOutputComponent implements Component {
      return contentLines;
    }

-    const shown = contentLines.slice(0, this.maxLines);
    const remaining = contentLines.length - this.maxLines;
+    if (this.tail) {
+      const shown = contentLines.slice(contentLines.length - this.maxLines);
+      return [
+        ' '.repeat(this.indent) + currentTheme.dim(`... (${String(remaining)} earlier lines)`),
+        ...shown,
+      ];
+    }
+
+    const shown = contentLines.slice(0, this.maxLines);
    const hint = this.expandHint
      ? `... (${String(remaining)} more lines, ctrl+o to expand)`
      : `... (${String(remaining)} more lines)`;
--- a/apps/kimi-code/src/tui/controllers/session-event-handler.ts
+++ b/apps/kimi-code/src/tui/controllers/session-event-handler.ts
@ -515,12 +515,17 @@ export class SessionEventHandler {
  }

  private handleToolProgress(event: ToolProgressEvent): void {
-    if (event.update.kind !== 'status') return;
    const text = event.update.text;
    if (text === undefined || text.length === 0) return;
    const tc = this.host.streamingUI.getToolComponent(event.toolCallId);
    if (tc === undefined) return;
-    tc.appendProgress(text);
+    if (event.update.kind === 'status') {
+      tc.appendProgress(text);
+      return;
+    }
+    if (event.update.kind === 'stdout' || event.update.kind === 'stderr') {
+      tc.appendLiveOutput(text);
+    }
  }

  private handleToolResult(event: ToolResultEvent): void {
--- a/apps/kimi-code/src/tui/controllers/subagent-event-handler.ts
+++ b/apps/kimi-code/src/tui/controllers/subagent-event-handler.ts
@ -107,6 +107,12 @@ export class SubAgentEventHandler {
        name: event.name,
        argumentsPart: event.argumentsPart ?? null,
      });
+    } else if (
+      event.type === 'tool.progress' &&
+      (event.update.kind === 'stdout' || event.update.kind === 'stderr') &&
+      event.update.text !== undefined
+    ) {
+      toolCall.appendSubToolLiveOutput(`${childAgentId}:${event.toolCallId}`, event.update.text);
    } else if (event.type === 'tool.result') {
      toolCall.finishSubToolCall({
        tool_call_id: `${childAgentId}:${event.toolCallId}`,
--- a/apps/kimi-code/test/tui/components/messages/tool-call.test.ts
+++ b/apps/kimi-code/test/tui/components/messages/tool-call.test.ts
@ -78,6 +78,48 @@ describe('ToolCallComponent', () => {
    expect(expanded).not.toContain('ctrl+o to expand');
  });

+  it('renders live Bash output while the command is running', () => {
+    const component = new ToolCallComponent(
+      {
+        id: 'call_shell_live',
+        name: 'Bash',
+        args: { command: 'printf output' },
+      },
+      undefined,
+    );
+
+    component.appendLiveOutput('line1\n');
+    component.appendLiveOutput('line2\n');
+
+    const out = strip(component.render(100).join('\n'));
+    expect(out).toContain('Using Bash');
+    expect(out).toContain('line1');
+    expect(out).toContain('line2');
+  });
+
+  it('clears live Bash output when the final result arrives', () => {
+    const component = new ToolCallComponent(
+      {
+        id: 'call_shell_live_done',
+        name: 'Bash',
+        args: { command: 'printf output' },
+      },
+      undefined,
+    );
+
+    component.appendLiveOutput('streamed-only\n');
+    component.setResult({
+      tool_call_id: 'call_shell_live_done',
+      output: 'final-only\n',
+      is_error: false,
+    });
+
+    const out = strip(component.render(100).join('\n'));
+    expect(out).toContain('Used Bash');
+    expect(out).toContain('final-only');
+    expect(out).not.toContain('streamed-only');
+  });
+
  it('hides tool output bodies that start with a <system tag', () => {
    const reminderOutput =
      '<system-reminder>\nThe task tools have not been used recently.\n</system-reminder>';
--- a/docs/en/reference/tools.md
+++ b/docs/en/reference/tools.md
@ -44,7 +44,7 @@ File tools handle reading, writing, and searching the local filesystem — the f
 - `description`: background task description; required when `run_in_background=true`
 - `disable_timeout`: whether to remove the timeout limit for background tasks

-Foreground mode blocks the current turn until the command completes or times out; background mode returns a task ID immediately and automatically notifies the Agent when the task finishes. stdin is always closed — interactive commands receive EOF immediately. A two-phase termination strategy (SIGTERM → 5-second grace period → SIGKILL) ensures reliable process cleanup after a timeout. On Windows, Git Bash is used by default.
+Foreground mode blocks the current turn until the command completes or times out, and the TUI streams stdout and stderr into the running `Bash` tool card while the command is still active. Background mode returns a task ID immediately and automatically notifies the Agent when the task finishes. stdin is always closed — interactive commands receive EOF immediately. A two-phase termination strategy (SIGTERM → 5-second grace period → SIGKILL) ensures reliable process cleanup after a timeout. On Windows, Git Bash is used by default.

 ## Web Tools

--- a/docs/zh/reference/tools.md
+++ b/docs/zh/reference/tools.md
@ -44,7 +44,7 @@
 - `description`：后台任务描述，`run_in_background=true` 时必填
 - `disable_timeout`：后台任务是否取消超时限制

-前台模式会阻塞当前轮次，直到命令结束或超时；后台模式立即返回任务 ID，任务结束时自动通知 Agent。stdin 始终被关闭，交互式命令会立即收到 EOF。两阶段终止策略（SIGTERM → 5 秒宽限期 → SIGKILL）确保超时后进程可靠结束。Windows 平台默认使用 Git Bash。
+前台模式会阻塞当前轮次，直到命令结束或超时；命令运行期间，TUI 会把 stdout 和 stderr 流式显示在正在运行的 `Bash` 工具卡片中。后台模式立即返回任务 ID，任务结束时自动通知 Agent。stdin 始终被关闭，交互式命令会立即收到 EOF。两阶段终止策略（SIGTERM → 5 秒宽限期 → SIGKILL）确保超时后进程可靠结束。Windows 平台默认使用 Git Bash。

 ## 网络类

--- a/packages/agent-core/src/tools/builtin/shell/bash.ts
+++ b/packages/agent-core/src/tools/builtin/shell/bash.ts
@ -31,7 +31,7 @@ import { z } from 'zod';

 import { ProcessBackgroundTask, type BackgroundManager } from '../../../agent/background';
 import type { BuiltinTool } from '../../../agent/tool';
-import type { ExecutableToolResult, ToolExecution } from '../../../loop/types';
+import type { ExecutableToolResult, ToolExecution, ToolUpdate } from '../../../loop/types';
 import { renderPrompt } from '../../../utils/render-prompt';
 import { toInputJsonSchema } from '../../support/input-schema';
 import { literalRulePattern, matchesGlobRuleSubject } from '../../support/rule-match';
@ -181,7 +181,7 @@ export class BashTool implements BuiltinTool<BashInput> {
      },
      approvalRule: literalRulePattern(this.name, args.command),
      matchesRule: (ruleArgs) => matchesGlobRuleSubject(ruleArgs, args.command),
-      execute: ({ signal }) => this.execution(args, signal),
+      execute: ({ signal, onUpdate }) => this.execution(args, signal, onUpdate),
    };
  }

@ -212,7 +212,11 @@ export class BashTool implements BuiltinTool<BashInput> {
    return this.kaos.execWithEnv(shellArgs, mergedEnv);
  }

-  private async execution(args: BashInput, signal: AbortSignal): Promise<ExecutableToolResult> {
+  private async execution(
+    args: BashInput,
+    signal: AbortSignal,
+    onUpdate?: ((update: ToolUpdate) => void) | undefined,
+  ): Promise<ExecutableToolResult> {
    if (signal.aborted) {
      return { isError: true, output: 'Aborted before command started' };
    }
@ -312,8 +316,8 @@ export class BashTool implements BuiltinTool<BashInput> {
      const isTerminating = (): boolean => timedOut || aborted || killed;
      const [, exitCode] = await Promise.all([
        Promise.all([
-          readStreamIntoBuilder(proc.stdout, builder, isTerminating),
-          readStreamIntoBuilder(proc.stderr, builder, isTerminating),
+          readStreamIntoBuilder(proc.stdout, builder, 'stdout', onUpdate, isTerminating),
+          readStreamIntoBuilder(proc.stderr, builder, 'stderr', onUpdate, isTerminating),
        ]),
        proc.wait(),
      ]);
@ -439,6 +443,8 @@ export class BashTool implements BuiltinTool<BashInput> {
 async function readStreamIntoBuilder(
  stream: Readable,
  builder: ToolResultBuilder,
+  kind: 'stdout' | 'stderr',
+  onUpdate?: ((update: ToolUpdate) => void) | undefined,
  suppressPrematureClose?: () => boolean,
 ): Promise<void> {
  const decoder = new StringDecoder('utf8');
@ -446,14 +452,18 @@ async function readStreamIntoBuilder(
    for await (const chunk of stream) {
      const buf: Buffer =
        typeof chunk === 'string' ? Buffer.from(chunk, 'utf8') : (chunk as Buffer);
-      builder.write(decoder.write(buf));
+      const text = decoder.write(buf);
+      if (text.length > 0) onUpdate?.({ kind, text });
+      builder.write(text);
    }
  } catch (error) {
    if (!isPrematureCloseError(error) || suppressPrematureClose?.() !== true) {
      throw error;
    }
  }
-  builder.write(decoder.end());
+  const trailing = decoder.end();
+  if (trailing.length > 0) onUpdate?.({ kind, text: trailing });
+  builder.write(trailing);
 }

 function isPrematureCloseError(error: unknown): boolean {
--- a/packages/agent-core/test/agent/basic.test.ts
+++ b/packages/agent-core/test/agent/basic.test.ts
@ -119,6 +119,7 @@ it('runs an agent turn through builtin tool approval and execution', async () =>
    [wire] permission.record_approval_result   { "turnId": 0, "toolCallId": "call_bash", "toolName": "Bash", "action": "Running: printf lookup-result", "result": { "decision": "approved", "selectedLabel": "approve" }, "time": "<time>" }
    [wire] context.append_loop_event           { "event": { "type": "tool.call", "uuid": "call_bash", "turnId": "0", "step": 1, "stepUuid": "<uuid-1>", "toolCallId": "call_bash", "name": "Bash", "args": { "command": "printf lookup-result", "timeout": 60 }, "description": "Running: printf lookup-result", "display": { "kind": "command", "command": "printf lookup-result", "cwd": "<cwd>", "language": "bash" } }, "time": "<time>" }
    [emit] tool.call.started                   { "turnId": 0, "toolCallId": "call_bash", "name": "Bash", "args": { "command": "printf lookup-result", "timeout": 60 }, "description": "Running: printf lookup-result", "display": { "kind": "command", "command": "printf lookup-result", "cwd": "<cwd>", "language": "bash" } }
+    [emit] tool.progress                       { "turnId": 0, "toolCallId": "call_bash", "update": { "kind": "stdout", "text": "lookup-result" } }
    [wire] context.append_loop_event           { "event": { "type": "tool.result", "parentUuid": "call_bash", "toolCallId": "call_bash", "result": { "output": "lookup-result" } }, "time": "<time>" }
    [emit] tool.result                         { "turnId": 0, "toolCallId": "call_bash", "output": "lookup-result" }
    [wire] context.append_loop_event           { "event": { "type": "step.end", "uuid": "<uuid-1>", "turnId": "0", "step": 1, "usage": { "inputOther": 11, "output": 22, "inputCacheRead": 0, "inputCacheCreation": 0 }, "finishReason": "tool_use" }, "time": "<time>" }
--- a/packages/agent-core/test/agent/config.test.ts
+++ b/packages/agent-core/test/agent/config.test.ts
@ -144,6 +144,7 @@ describe('Agent config', () => {
      [wire] tools.set_active_tools              { "names": [], "time": "<time>" }
      [wire] context.append_loop_event           { "event": { "type": "tool.call", "uuid": "call_bash", "turnId": "0", "step": 1, "stepUuid": "<uuid-1>", "toolCallId": "call_bash", "name": "Bash", "args": { "command": "printf original-result", "timeout": 60 }, "description": "Running: printf original-result", "display": { "kind": "command", "command": "printf original-result", "cwd": "<cwd>", "language": "bash" } }, "time": "<time>" }
      [emit] tool.call.started                   { "turnId": 0, "toolCallId": "call_bash", "name": "Bash", "args": { "command": "printf original-result", "timeout": 60 }, "description": "Running: printf original-result", "display": { "kind": "command", "command": "printf original-result", "cwd": "<cwd>", "language": "bash" } }
+      [emit] tool.progress                       { "turnId": 0, "toolCallId": "call_bash", "update": { "kind": "stdout", "text": "original-result" } }
      [wire] context.append_loop_event           { "event": { "type": "tool.result", "parentUuid": "call_bash", "toolCallId": "call_bash", "result": { "output": "original-result" } }, "time": "<time>" }
      [emit] tool.result                         { "turnId": 0, "toolCallId": "call_bash", "output": "original-result" }
      [wire] context.append_loop_event           { "event": { "type": "step.end", "uuid": "<uuid-1>", "turnId": "0", "step": 1, "usage": { "inputOther": 9, "output": 23, "inputCacheRead": 0, "inputCacheCreation": 0 }, "finishReason": "tool_use" }, "time": "<time>" }
--- a/packages/agent-core/test/agent/permission.test.ts
+++ b/packages/agent-core/test/agent/permission.test.ts
@ -58,6 +58,7 @@ describe('Agent permission', () => {
      [wire] context.append_loop_event   { "event": { "type": "content.part", "uuid": "<uuid-2>", "turnId": "0", "step": 1, "stepUuid": "<uuid-1>", "part": { "type": "text", "text": "Running without asking." } }, "time": "<time>" }
      [wire] context.append_loop_event   { "event": { "type": "tool.call", "uuid": "call_bash", "turnId": "0", "step": 1, "stepUuid": "<uuid-1>", "toolCallId": "call_bash", "name": "Bash", "args": { "command": "printf permission-output", "timeout": 60 }, "description": "Running: printf permission-output", "display": { "kind": "command", "command": "printf permission-output", "cwd": "<cwd>", "language": "bash" } }, "time": "<time>" }
      [emit] tool.call.started           { "turnId": 0, "toolCallId": "call_bash", "name": "Bash", "args": { "command": "printf permission-output", "timeout": 60 }, "description": "Running: printf permission-output", "display": { "kind": "command", "command": "printf permission-output", "cwd": "<cwd>", "language": "bash" } }
+      [emit] tool.progress               { "turnId": 0, "toolCallId": "call_bash", "update": { "kind": "stdout", "text": "auto-output" } }
      [wire] context.append_loop_event   { "event": { "type": "tool.result", "parentUuid": "call_bash", "toolCallId": "call_bash", "result": { "output": "auto-output" } }, "time": "<time>" }
      [emit] tool.result                 { "turnId": 0, "toolCallId": "call_bash", "output": "auto-output" }
      [wire] context.append_loop_event   { "event": { "type": "step.end", "uuid": "<uuid-1>", "turnId": "0", "step": 1, "usage": { "inputOther": 91, "output": 25, "inputCacheRead": 0, "inputCacheCreation": 0 }, "finishReason": "tool_use" }, "time": "<time>" }
@ -113,6 +114,7 @@ describe('Agent permission', () => {
      [wire] context.append_loop_event   { "event": { "type": "content.part", "uuid": "<uuid-2>", "turnId": "0", "step": 1, "stepUuid": "<uuid-1>", "part": { "type": "text", "text": "Running in yolo mode." } }, "time": "<time>" }
      [wire] context.append_loop_event   { "event": { "type": "tool.call", "uuid": "call_bash", "turnId": "0", "step": 1, "stepUuid": "<uuid-1>", "toolCallId": "call_bash", "name": "Bash", "args": { "command": "printf permission-output", "timeout": 60 }, "description": "Running: printf permission-output", "display": { "kind": "command", "command": "printf permission-output", "cwd": "<cwd>", "language": "bash" } }, "time": "<time>" }
      [emit] tool.call.started           { "turnId": 0, "toolCallId": "call_bash", "name": "Bash", "args": { "command": "printf permission-output", "timeout": 60 }, "description": "Running: printf permission-output", "display": { "kind": "command", "command": "printf permission-output", "cwd": "<cwd>", "language": "bash" } }
+      [emit] tool.progress               { "turnId": 0, "toolCallId": "call_bash", "update": { "kind": "stdout", "text": "yolo-output" } }
      [wire] context.append_loop_event   { "event": { "type": "tool.result", "parentUuid": "call_bash", "toolCallId": "call_bash", "result": { "output": "yolo-output" } }, "time": "<time>" }
      [emit] tool.result                 { "turnId": 0, "toolCallId": "call_bash", "output": "yolo-output" }
      [wire] context.append_loop_event   { "event": { "type": "step.end", "uuid": "<uuid-1>", "turnId": "0", "step": 1, "usage": { "inputOther": 7, "output": 25, "inputCacheRead": 0, "inputCacheCreation": 0 }, "finishReason": "tool_use" }, "time": "<time>" }
--- a/packages/agent-core/test/agent/plan.test.ts
+++ b/packages/agent-core/test/agent/plan.test.ts
@ -448,6 +448,7 @@ describe('plan allows safe tool flow', () => {
      [wire] context.append_loop_event   { "event": { "type": "content.part", "uuid": "<uuid-2>", "turnId": "0", "step": 1, "stepUuid": "<uuid-1>", "part": { "type": "text", "text": "I will inspect safely." } }, "time": "<time>" }
      [wire] context.append_loop_event   { "event": { "type": "tool.call", "uuid": "call_bash", "turnId": "0", "step": 1, "stepUuid": "<uuid-1>", "toolCallId": "call_bash", "name": "Bash", "args": { "command": "printf plan-safe", "timeout": 60 }, "description": "Running: printf plan-safe", "display": { "kind": "command", "command": "printf plan-safe", "cwd": "<cwd>", "language": "bash" } }, "time": "<time>" }
      [emit] tool.call.started           { "turnId": 0, "toolCallId": "call_bash", "name": "Bash", "args": { "command": "printf plan-safe", "timeout": 60 }, "description": "Running: printf plan-safe", "display": { "kind": "command", "command": "printf plan-safe", "cwd": "<cwd>", "language": "bash" } }
+      [emit] tool.progress               { "turnId": 0, "toolCallId": "call_bash", "update": { "kind": "stdout", "text": "plan-safe" } }
      [wire] context.append_loop_event   { "event": { "type": "tool.result", "parentUuid": "call_bash", "toolCallId": "call_bash", "result": { "output": "plan-safe" } }, "time": "<time>" }
      [emit] tool.result                 { "turnId": 0, "toolCallId": "call_bash", "output": "plan-safe" }
      [wire] context.append_loop_event   { "event": { "type": "step.end", "uuid": "<uuid-1>", "turnId": "0", "step": 1, "usage": { "inputOther": 536, "output": 23, "inputCacheRead": 0, "inputCacheCreation": 0 }, "finishReason": "tool_use" }, "time": "<time>" }
@ -501,6 +502,7 @@ describe('plan mode Bash ordinary permission behavior', () => {
      [wire] context.append_loop_event   { "event": { "type": "content.part", "uuid": "<uuid-2>", "turnId": "0", "step": 1, "stepUuid": "<uuid-1>", "part": { "type": "text", "text": "I will mutate a file." } }, "time": "<time>" }
      [wire] context.append_loop_event   { "event": { "type": "tool.call", "uuid": "call_bash", "turnId": "0", "step": 1, "stepUuid": "<uuid-1>", "toolCallId": "call_bash", "name": "Bash", "args": { "command": "rm forbidden.txt", "timeout": 60 }, "description": "Running: rm forbidden.txt", "display": { "kind": "command", "command": "rm forbidden.txt", "cwd": "<cwd>", "language": "bash" } }, "time": "<time>" }
      [emit] tool.call.started           { "turnId": 0, "toolCallId": "call_bash", "name": "Bash", "args": { "command": "rm forbidden.txt", "timeout": 60 }, "description": "Running: rm forbidden.txt", "display": { "kind": "command", "command": "rm forbidden.txt", "cwd": "<cwd>", "language": "bash" } }
+      [emit] tool.progress               { "turnId": 0, "toolCallId": "call_bash", "update": { "kind": "stdout", "text": "removed" } }
      [wire] context.append_loop_event   { "event": { "type": "tool.result", "parentUuid": "call_bash", "toolCallId": "call_bash", "result": { "output": "removed" } }, "time": "<time>" }
      [emit] tool.result                 { "turnId": 0, "toolCallId": "call_bash", "output": "removed" }
      [wire] context.append_loop_event   { "event": { "type": "step.end", "uuid": "<uuid-1>", "turnId": "0", "step": 1, "usage": { "inputOther": 533, "output": 23, "inputCacheRead": 0, "inputCacheCreation": 0 }, "finishReason": "tool_use" }, "time": "<time>" }
--- a/packages/agent-core/test/agent/turn.test.ts
+++ b/packages/agent-core/test/agent/turn.test.ts
@ -1565,6 +1565,7 @@ describe('Agent turn flow', () => {
      [wire] permission.record_approval_result   { "turnId": 0, "toolCallId": "call_bash", "toolName": "Bash", "action": "Running: printf approved", "result": { "decision": "approved", "selectedLabel": "approve" }, "time": "<time>" }
      [wire] context.append_loop_event           { "event": { "type": "tool.call", "uuid": "call_bash", "turnId": "0", "step": 1, "stepUuid": "<uuid-1>", "toolCallId": "call_bash", "name": "Bash", "args": { "command": "printf approved", "timeout": 60 }, "description": "Running: printf approved", "display": { "kind": "command", "command": "printf approved", "cwd": "<cwd>", "language": "bash" } }, "time": "<time>" }
      [emit] tool.call.started                   { "turnId": 0, "toolCallId": "call_bash", "name": "Bash", "args": { "command": "printf approved", "timeout": 60 }, "description": "Running: printf approved", "display": { "kind": "command", "command": "printf approved", "cwd": "<cwd>", "language": "bash" } }
+      [emit] tool.progress                       { "turnId": 0, "toolCallId": "call_bash", "update": { "kind": "stdout", "text": "approved" } }
      [wire] context.append_loop_event           { "event": { "type": "tool.result", "parentUuid": "call_bash", "toolCallId": "call_bash", "result": { "output": "approved" } }, "time": "<time>" }
      [emit] tool.result                         { "turnId": 0, "toolCallId": "call_bash", "output": "approved" }
      [wire] context.append_loop_event           { "event": { "type": "step.end", "uuid": "<uuid-1>", "turnId": "0", "step": 1, "usage": { "inputOther": 7, "output": 22, "inputCacheRead": 0, "inputCacheCreation": 0 }, "finishReason": "tool_use" }, "time": "<time>" }
--- a/packages/agent-core/test/tools/shell-quoting.test.ts
+++ b/packages/agent-core/test/tools/shell-quoting.test.ts
@ -35,6 +35,18 @@ function fakeProcess(): KaosProcess {
  };
 }

+function fakeProcessWithOutput(stdout: Readable, stderr: Readable): KaosProcess {
+  return {
+    stdin: { end: vi.fn(), write: vi.fn() } as unknown as Writable,
+    stdout,
+    stderr,
+    pid: 321,
+    exitCode: 0,
+    wait: vi.fn(async () => 0),
+    kill: vi.fn(async () => {}),
+  };
+}
+
 const signal = new AbortController().signal;

 function captureCommandRewrite(
@ -132,3 +144,30 @@ describe('shell command nul-redirect — non-Windows passthrough', () => {
    expect(rewritten).toBe(command);
  });
 });
+
+describe('BashTool streaming output updates', () => {
+  it('emits stdout and stderr chunks while preserving the final output', async () => {
+    const proc = fakeProcessWithOutput(
+      Readable.from([Buffer.from('out-1\n'), Buffer.from('out-2')]),
+      Readable.from([Buffer.from('err-1\n')]),
+    );
+    const execWithEnv = vi.fn().mockResolvedValue(proc);
+    const onUpdate = vi.fn();
+    const tool = new BashTool(createFakeKaos({ execWithEnv, osEnv: linuxEnv }), '/work');
+
+    const result = await executeTool(tool, {
+      turnId: '0',
+      toolCallId: 'tc_stream',
+      args: { command: 'printf output' },
+      signal,
+      onUpdate,
+    });
+
+    expect(result.output).toContain('out-1\n');
+    expect(result.output).toContain('out-2');
+    expect(result.output).toContain('err-1\n');
+    expect(onUpdate).toHaveBeenCalledWith({ kind: 'stdout', text: 'out-1\n' });
+    expect(onUpdate).toHaveBeenCalledWith({ kind: 'stdout', text: 'out-2' });
+    expect(onUpdate).toHaveBeenCalledWith({ kind: 'stderr', text: 'err-1\n' });
+  });
+});