fix(compact): harden pruning integration (round 2)

packages/ui/stdio/README.md

@@ -27,7 +27,7 @@ The plugin seeds display labels from the live agent registry, then tracks `agent
 
 **What the model sees**: Each non-empty terminal line outside an active question becomes one text block, sent with `agent.send()` while the target agent is idle and `agent.steer()` while it is running.
 
-**Token effect**: Submitted text is retained under the agent loop's normal session-history and compaction rules. The welcome banner, `> ` prompt, rendered transcript, and `[tool call]` / `[tool result]` terminal lines add no tokens.
+**Token effect**: Submitted text is retained under the agent loop's normal session-history and compaction rules. The welcome banner, `> ` prompt, rendered transcript, and `[tool call]` / `[tool result]` terminal lines add no tokens. A replacement `tool/result` remains model-visible through the session surface but is not rendered as a second execution; stdio keeps the original full-fidelity result line.
 
 ### Terminal user-interaction answers
 

packages/ui/stdio/src/index.ts

@@ -124,6 +124,10 @@ export function createStdioChat(ctx: Context, config: Config, runtime: StdioRunt
       inReasoning = false
       output.write(`\n  [tool call] ${toolName}(${args})`)
     } else if (event.type === 'tool/result') {
+      // A surface replacement changes future model context; it is not another
+      // execution. Keep the original full-fidelity terminal presentation and
+      // suppress duplicate output during live delivery or log replay.
+      if (event.surfaceOp !== undefined && event.surfaceOp !== 'append') return
       const { content } = event.data
       const text = content.filter(block => block.type === 'text').map(block => block.text).join('')
       output.write(`\n  [tool result] ${text}\n  `)

packages/ui/stdio/tests/stdio.spec.ts

@@ -288,6 +288,43 @@ describe('createStdioChat rendering', () => {
     expect(out.text()).toContain('[tool result] file.txt')
   })
 
+  it('renders one full-fidelity result whether the event feed is live or replayed', async () => {
+    const { ctx, out } = await setup()
+    const session = makeSession('main')
+    const original = {
+      type: 'tool/result',
+      seq: 2,
+      time: 0,
+      data: {
+        turn: 1,
+        step: 1,
+        callId: 'c1',
+        content: [{ type: 'text', text: 'full terminal output' }],
+        isError: false,
+        meta: { terminal: { output: 'full terminal output' } },
+      },
+      surfaceOp: 'append',
+    } as SessionEvent
+    const replacement = {
+      ...original,
+      seq: 3,
+      data: {
+        ...original.data,
+        content: [{ type: 'text', text: '[... tool result middle pruned ...]' }],
+      },
+      surfaceOp: { op: 'replace', start: 2, end: 2 },
+      sourceEventSeqs: [2],
+    } as SessionEvent
+
+    // Stdio consumes the same session/event shape whether a host forwards a
+    // live append or replays a stored log through the rendering feed.
+    for (const event of [original, replacement]) ctx.emit('session/event', session, event)
+
+    expect(out.text().match(/\[tool result\]/g)).toHaveLength(1)
+    expect(out.text()).toContain('full terminal output')
+    expect(out.text()).not.toContain('tool result middle pruned')
+  })
+
   it('renders a todo/write session event as a glyphed checklist', async () => {
     const { ctx, out } = await setup()
     const session = {} as Session