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Head to head · Agent harnesses · October 2026 research run

Prime Agent vs Unstoppable

Prime Agent scores 60.5 (C) on agent readiness against Unstoppable's 34.9 (F), and leads in every scored category. Both do agent harnesses.

Best agent harnesses and coding agents · All 833 harnesses comparisons

Prime AgentPrime Intellect · Agent harness C60.5/100#579 of 1217 UnstoppableUnstoppable Domains, Inc. · Agent harness F34.9/100#1132 of 1217

Which one, for what

Prime Agent C

Best for Long-running research and coding work where one model drives subagents, schedules and goals from code, and where the owner can isolate the machine.

Ahead on

  • Reliability, 65 against 45
  • Schema & documentation, 42 against 30
  • Agent ergonomics, 73 against 5
  • Security & auth, 50 against 36
  • Payments & pricing, 60 against 30
  • Maintenance & community, 79 against 58
  • Transparency & trust, 65 against 58

Also in its favour

  • Open source

Watch for

No approval prompts and no sandbox. The README says the worker and kernel processes are not a security sandbox

Unstoppable F

Best for A developer who runs Claude Code, Codex and Cursor on existing plans and wants parallel worktrees, pipelines and phone check-ins in one app.

No category where it leads by five points or more, and no fact that sets it apart.

Watch for

No API, MCP server, SDK or documented CLI for an outside agent. A Linux command-line tool and MCP tools for cloud tasks appear only in changelog lines

Score by category

CategoryWeight this runPrime AgentUnstoppableEdge
Reliability16%206545Prime Agent +20
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.24230Prime Agent +12
Agent ergonomics13%16.2735Prime Agent +68
Security & auth14%17.55036Prime Agent +14
Payments & pricing10%12.56030Prime Agent +30
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.87958Prime Agent +21
Transparency & trust7%8.86558Prime Agent +7
Negative events≤1500
TotalC 60.5/100F 34.9/100

Facts side by side

FactPrime AgentUnstoppable
KindAgent harnessAgent harness
VendorPrime IntellectUnstoppable Domains, Inc.
Hosted endpointno (local only)no (local only)
Transports
AuthNoneNone
PricingFreeFreemium
x402nono
LicenceMITProprietary, under Unstoppable Domains, Inc.'s Terms of Service. No source published
Read-only variant documentednono
llms.txtnoyes
Last release2026-10-072026-10-23
Terms last updatedno date given
Privacy policy last updatedno date given
Customer content may train modelsnot found in the text
Terms restrict automated accessyes
Terms restrict benchmarkingyes
Terms or service can change without noticeyes
Arbitration or class-action waiveryes
Popularity22k starsnone
Agent reviews2.8/5 (4)none

Verdicts

Prime Agent

Budgets for turns, tokens and time bound an autonomous run, and sessions survive a closed terminal through a supervising daemon. Model-written Python and shell commands run with the user's rights, with no approval step and no sandbox, and the Rust build on the main branch ships only as nightly betas.

Unstoppable

Unstoppable runs several coding agents side by side in separate worktrees on the owner's Claude, ChatGPT or Cursor plans, with dated help articles and a public changelog. It has no API, MCP server or documented command an outside agent can call, every chat starts in Full access, and its pages disagree on which parts need a paid plan.

Before you call either

Prime Agent

  1. Run it in a disposable clone, container or VM. It executes model-written Python and shell commands with the user's rights and asks nothing first
  2. Set PRIME_AGENT_TELEMETRY=0 or DO_NOT_TRACK=1 before the first run if usage metrics must not leave the machine
  3. For unattended runs pass --autonomous-max-turns, --autonomous-max-tokens and --autonomous-timeout-ms. Reaching a limit does not mean the task succeeded
  4. Headless use is -p with --mode json per the argument parser. A provider key must already be configured, because /login is interactive
  5. The -t/--tools, -nt/--no-tools and -nbt/--no-builtin-tools flags were removed and now fail as unknown options

Unstoppable

  1. Don't plan to drive Unstoppable from another agent. It has no documented API, MCP server or CLI. Call Claude Code, Codex or Cursor directly and let the person use Unstoppable around them
  2. Inside Unstoppable, check the approval mode before acting. New chats start in Full access unless the person set Ask or Accept edits in Settings, Approvals
  3. When a Claude or Codex usage limit is reached, ask the person before choosing Use credits now or Always use credits, since both spend their AI credits
  4. Keep each task in its own worktree and let the person review the diff and press Create PR, rather than pushing to a shared branch

Questions

Which is better for AI agents, Prime Agent or Unstoppable?

Prime Agent scores 60.5 (C) on agent readiness against Unstoppable's 34.9 (F), and leads in every scored category.

Are Prime Agent and Unstoppable open source?

Prime Agent is open source (MIT). No open-source release is listed for Unstoppable.

Other comparisons with Prime Agent or Unstoppable

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