NousResearch/hermes-agent · error · Error

right-pane found no horizontal terminal split separator.

Error message

right-pane found no horizontal terminal split separator.

What it means

Error "right-pane found no horizontal terminal split separator." thrown in NousResearch/hermes-agent.

Source

Thrown at apps/desktop/scripts/perf/scenarios/right-pane.mjs:272

        await cdp.eval(`window.__PERF_DRIVE__.rightPaneGit(${JSON.stringify(relative)}, 'modified')`)
        await sleep(250)
        affectedGit = JSON.parse(await cdp.eval(SNAPSHOT_COUNTERS))
      }

      await cdp.eval(START_COUNTERS)
      const drag = JSON.parse(await cdp.eval(DRAG_TERMINAL_SPLIT))
      const dragCounters = JSON.parse(await cdp.eval(SNAPSHOT_COUNTERS))
      const recorded = JSON.parse(await cdp.eval(COLLECT_RECORDERS))
      const frames = trimWarmup(recorded.frames)
      const longtasks = recorded.longtasks.map(entry => entry.duration)
      const streamCounts = stream.counts
      const activationCounts = activation.counts
      const unrelatedCounts = unrelatedGit.counts
      const affectedRows = Object.values(affectedGit.rows).reduce((sum, count) => sum + count, 0)
      const affectedPaths = Object.keys(affectedGit.rows).length

      if (drag.target === 'none') {
        throw new Error('right-pane found no horizontal terminal split separator.')
      }

      return {
        metrics: {
          chat_terminal_measures: streamCounts['terminal-measure'],
          hidden_terminal_fits: activationCounts['terminal-fit-hidden'] + streamCounts['terminal-fit-hidden'],
          activation_fit_mismatch: Math.abs(activationCounts['terminal-fit-active'] - setup.terminalIds.length),
          unrelated_tree_renders: unrelatedCounts['project-tree-render'],
          unrelated_row_renders: unrelatedCounts['project-tree-row-render'],
          affected_tree_renders: affectedGit.counts['project-tree-render'],
          affected_row_path_excess: Math.max(0, affectedPaths - 1),
          terminal_drift_px: Math.round(drag.drift * 10) / 10,
          frame_p95_ms: Math.round(percentile(frames, 0.95) * 10) / 10,
          frame_p99_ms: Math.round(percentile(frames, 0.99) * 10) / 10,
          slow_frames_33: frames.filter(frame => frame > 33).length,
          longtask_max_ms: Math.round((longtasks.length ? Math.max(...longtasks) : 0) * 10) / 10
        },
        detail: {

View on GitHub (pinned to c896c09c42)

Solutions

1. Open a horizontal terminal split before running the scenario.
2. Verify the right-pane layout is enabled in the build under test.

When it happens

Trigger: Thrown at apps/desktop/scripts/perf/scenarios/right-pane.mjs:272 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of NousResearch/hermes-agent@c896c09c42 (2026-08-14). Data as JSON: /api/errors/a01fc91e048383da. Report an issue: GitHub.