Does Claude Code Plan Mode Actually Help? We Tested It

Both Claude Sonnet 4.6 builds passed every functional check and tied on blinded UX review; native Plan Mode took 79.587 seconds longer in this Project Board test.

The task

Read the exact prompt

1|Replace the starter page with a responsive Project Board interface.
2|
3|Create three columns named To Do, In Progress, and Done.
4|
5|Seed exactly six tasks across the three columns. Each task must have:
6|- a short realistic title
7|- an assignee chosen from Alex, Maya, or Sam
8|- a priority of Low, Medium, or High
9|
10|Users must be able to move tasks between adjacent columns. Drag and drop is not required. You may choose the interaction pattern.
11|
12|Add an assignee filter with options All, Alex, Maya, and Sam. Changing the filter must immediately update which task cards are visible.
13|
14|Each column header must show a live count of the currently visible tasks in that column.
15|
16|Persist the board state and selected assignee filter to localStorage so that refreshing the page restores the user's most recent state.
17|
18|Include a Reset Board control that restores the original six seeded tasks, resets the assignee filter to All, and updates localStorage accordingly.
19|
20|Make reasonable product and UX decisions so that a first-time user can understand how to use the board without separate instructions. The interface should make important actions, state changes, filtering, task movement, persistence, and reset behavior intuitive and discoverable. You may choose the interaction details, labels, hierarchy, and supporting microcopy you think best achieve that goal. Do not add an onboarding tutorial or explanatory documentation page.
21|
22|The interface must be usable on desktop and mobile.
23|
24|Use the existing Next.js and TypeScript setup.
25|
26|Do not add external services or unnecessary dependencies.
27|

Desktop screenshot of the Direct arm's responsive Project Board with To Do, In Progress, and Done columns — Direct — desktopClaude Sonnet 4.6 · 10/10 checks · 16/16 blinded UXOpen full capture

Desktop screenshot of the native Plan Mode arm's responsive Project Board with three task columns — Native Plan Mode — desktopClaude Sonnet 4.6 · 10/10 checks · 16/16 blinded UXOpen full capture

Mobile screenshot of the Direct arm's Project Board with stacked columns and task movement controls — Direct — mobileResponsive 390-pixel viewportOpen full capture

Mobile screenshot of the native Plan Mode arm's Project Board with stacked columns and full-width movement controls — Native Plan Mode — mobileResponsive 390-pixel viewportOpen full capture

What happened

The empirical answer was a tie on the predefined outcomes: Direct and native Plan Mode each passed all 10 deterministic checks and each scored 16/16 on the blinded UX/product rubric.

Direct completed in 139.423 seconds. Plan took 119.788 seconds to plan and 99.217 seconds to implement, for 219.010 seconds total.

Plan therefore took 79.587 seconds longer, approximately 57% more contestant wall time than Direct.

Plan also used substantially more of the exposed token fields: +20 input, +1,280 cache-creation input, +454,763 cache-read input, and +3,651 output tokens. These fields describe recorded Claude Code usage, not a unique prompt-size total.

This treatment used Claude Code's native --permission-mode plan for Phase 1. The source stayed unchanged during planning, and implementation resumed the exact same Claude session under bypassPermissions.

The UX/product review was scored from neutrally labeled desktop and mobile outputs before Direct and Plan treatment labels were revealed. The predefined rubric tied, so no qualitative winner was inferred after the fact.

Meaningful differences

Difference	Observed
Deterministic correctness	Direct: 10/10; Plan: 10/10 — tie.
Blinded UX/product score	Direct: 16/16; Plan: 16/16 — tie.
Contestant runtime	Direct: 139.423s; Plan: 219.010s. Plan added 79.587s, about 57%.
Planning and implementation	Plan spent 119.788s in native Plan Mode and 99.217s implementing in the resumed session; Direct implemented immediately.
Exposed token usage	Plan minus Direct: +20 input, +1,280 cache-creation input, +454,763 cache-read input, +3,651 output; +459,714 across the summed exposed fields.
Implementation shape	Both produced usable responsive boards. Direct changed 3 source files; Plan changed or created 11 files, including extracted components, types, data, and a CSS module.

What this tells us

In this single controlled Project Board test using Claude Sonnet 4.6, Claude Code's native Plan Mode produced the same measured correctness and UX outcome as Direct implementation, while taking about 57% longer and using substantially more of the exposed token fields.

Evidence & setup

Setup

{
  "participants": [
    "Claude Code Direct",
    "Claude Code native Plan Mode followed by implementation in the exact same session"
  ],
  "model": "claude-sonnet-4-6",
  "claude_code_version": "2.1.251",
  "held_constant": [
    "byte-identical pristine source snapshot",
    "exact public task",
    "exact model selection",
    "Claude Code version",
    "bypassPermissions implementation mode",
    "project-only settings source behavior",
    "strict empty MCP configuration",
    "dependency preparation",
    "10-minute total contestant wall per arm",
    "deterministic grader and post-run validation"
  ],
  "treatment_variable": "Direct implementation versus native Claude Code --permission-mode plan followed by --resume of the exact session under bypassPermissions",
  "retries": 0,
  "repair_passes": 0
}

Supporting evidence

{
  "publication_quality_gate": "Standard case study: PASS",
  "run_id": "20260830T040443Z",
  "pristine_source_sha256": "e064ea314a6da1fcfdb8c3da1924c56a7b5051290ed5b25a1ac7dd1b434f1967",
  "direct_final_source_sha256": "b2c235ca860abf5f2ad387f077954c70634b8d48b23c406818525aaf662cabfc",
  "plan_final_source_sha256": "4e125a47da0ad47072691a3deec65cecc96587c12ce4a03988d9cae249792387",
  "direct_console_errors": [],
  "plan_console_errors": [],
  "blinded_ux_review": true,
  "cost_note": "Actual cost metadata exists in the private run evidence but this page does not derive or estimate cost from token counts."
}

Provenance

{
  "source_run": "runs/20260830T040443Z",
  "source_results": "runs/20260830T040443Z/results.json",
  "source_publication_analysis": "runs/20260830T040443Z/publication.json",
  "source_results_sha256": null
}

Documented limitations · 7

This was one task and one run per condition.
The experiment used one model, Claude Sonnet 4.6, through Claude Code 2.1.251.
The task was a moderately structured frontend and product exercise; results may differ for other task families.
Both arms fully passed, so this run does not show what happens when task difficulty is high enough to create correctness failures.
The predefined UX rubric saturated at 16/16 for both outputs and therefore could not distinguish quality above that threshold.
The summed exposed token fields are not a unique prompt-size total; cache reads can repeatedly count reused context.
This result does not generalize to all uses of Claude Code Plan Mode, and it does not establish that Plan Mode is generally worse, useless, or always slower.

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