Head to head · Agent harnesses · October 2026 research run

HarnessRouter vs Sculptor

Sculptor scores 53.1 (D) on agent readiness against HarnessRouter's 47.7 (D), and leads in 3 of 7 scored categories. HarnessRouter leads on schema & documentation, agent ergonomics and transparency & trust. Both do agent harnesses.

Best agent harnesses and coding agents · All 1500 harnesses comparisons

Which one, for what

HarnessRouter D

Best for A product team that wants to run Codex, Claude Code, Hermes or 27 other harnesses server-side behind one task, session and file contract, and switch between them by changing an ID.

Ahead on

  • Schema & documentation, 83 against 45
  • Agent ergonomics, 73 against 50
  • Transparency & trust, 73 against 57

Also in its favour

  • A hosted endpoint, with nothing to install

Watch for

No status page found (status.harnessrouter.ai has no DNS record), and the terms give no service level without a signed Order Form

Sculptor D

Best for Developers who want parallel coding agents in isolated workspaces and are fine with a research preview.

Ahead on

  • Reliability, 43 against 35
  • Payments & pricing, 60 against 25

Also in its favour

  • No key needed to call it
  • No incidents deducted, where HarnessRouter loses 11 points for them

Watch for

Labelled an experimental research preview that may change drastically

Why the edge

Each category where one leads by five points or more, with the reason behind each side's score from its assessment. The numbers are in the table below; this is what they stand for.

Schema & documentation HarnessRouter +38

HarnessRouter 83

API reading. UHP's OpenAPI 3.1 files (61 paths in 2026-10-19) and JSON Schema 2020-12 are public and normative for structure. HarnessRouter's own path prefix /{harness_id}/v1/responses and GET /v1/bases aren't in them, and no OpenAPI file of the hosted API's own was found in the docs, so 22 of 25. llms.txt, llms-full.txt, agents.md, docs.md, pricing.md and harnesses.md (10). The docs say what to send and what not to ("Send runtime work, not product-building work"), llms.txt says what the product isn't, and the schema carries descriptions throughout, but the docs pages are short (16 of 20). Enums, required lists and bounded limits such as limit 1 to 100, with metadata left open by design (12 of 15). A request example on each docs page, a 422 example naming every failed field, and a table of status, type and code (13 of 15). Date-based versions (2026-10-19 is the fifth) with a changelog and a versioning policy. Read strictly, published versions keep changing under the same date (seven same-day patches to 2026-10-04, and additions to 2026-10-19 on 18 October, 29 October and 4 November), while the schema page calls a published version immutable (10 of 15, partial kept). The conformance page and the suite's README now agree on 101 checks. 22 + 10 + 16 + 12 + 13 + 10 = 83.

Sculptor 45

Harness reading. A README, specs and agent docs in the repository; no API reference (45).

Payments & pricing Sculptor +35

HarnessRouter 25

Published rubric, for the hosted service. No machine payment protocol (0). Per-unit prices without a login, agent work per active minute and model calls at listed provider prices per million tokens (20). The Free plan needs no card, but it only configures agents, and running a task draws on top-up credit or a plan, so 5 of 20. A person signs up in a browser and creates the key in the console (0). 0 + 20 + 5 + 0 = 25. Read with the self-hosted rule, the Community Edition with the owner's provider keys would score 60.

Sculptor 60

Free self-hosted software with nothing to buy, so 0 for a protocol and 20 each for public pricing, a free tier and onboarding with no sign-up, 60.

Agent ergonomics HarnessRouter +23

HarnessRouter 73

API reading. Sessions, turns and files are separate reads, and list endpoints take limit and cursor, but there's no field selection on a response (15 of 25). Cursor paging on session and memory lists with a bounded limit, and few filters found (14 of 20). One error envelope with type, code, param and detail, a closed code set, a retry rule per code and a 422 that lists every failed field without echoing the body (18 of 20). Idempotency-Key on task creation, reuse only for the same request, recover from the session after a drop, and an explicit cancel because closing the stream doesn't stop work (18 of 20). Only input is required to run a task, and budgets default to 400 steps, 7,200 seconds and $10. No official SDK, only the OpenAI Responses shape, clients generated from the OpenAPI file and an Agent Skill (8 of 15). 73 in all.

Sculptor 50

Harness reading. Workspaces as isolated copies, review and merge back, and built-in skills (50).

Transparency & trust HarnessRouter +16

HarnessRouter 73

Editorial half. The server, specification, schema and conformance suite are Apache-2.0. The Cloud's own billing and deployment wasn't confirmed to match the open code, and the Agent Skill has a custom licence for some guides (25 of 30). The privacy policy, DPA, subprocessor list and a retention page agree. Customer content isn't used for training without an opt-in, and periods are stated (tasks deleted at once, agents and files after 30 days, backups within 14 days, credentials within 90, free-plan task records 7 days). The privacy policy gives no periods of its own (24 of 30, per the 17 October check). Deprecation 15 of 20 (was 14). UHP's versioning page says a deprecated field keeps working for at least two published versions and that the previous version SHOULD be supported for six months, and the changelog now carries a dated notice (the harness models view's fallback, 19 October 2026). The rule is counted in versions, not time, so dated notices give 15. Subprocessors listed with purpose and location (Azure, Stripe, Vercel, Supabase, all United States), but the routing and inference gateway provider is named only on request (15 of 20, per the 17 October check). 25 + 24 + 15 + 15 = 79. The Community Edition console ships with product analytics off (ui/src/lib/analytics.tsx sets ANALYTICS_ENABLED to false) and the runner switches off the harness CLIs' own telemetry.

Sculptor 57

MIT (30). Consent-based telemetry documented in the repository (18 of 30). The README warns of drastic changes during the research preview, with no deprecation policy (5). Opt-in telemetry (20). 30 + 18 + 5 + 20 = 73.

Reliability Sculptor +8

HarnessRouter 35

Hosted reading, for HarnessRouter Cloud at api.harnessrouter.ai, as on 17 October. No status page (status.harnessrouter.ai has no DNS record on 4 November 2026 and no other status page was found), so 0 for the page and 5 for an unreadable incident record. No request rate limit with numbers was found. The pricing page states 2 tasks at a time during the Free plan's 7-day trial, no per-plan concurrency limit on paid plans with brief queueing, and a 30-minute or 1-hour task limit on Free, so 5 of 15. 429 is in the error table as rate_limited with Retry-After (UHP Errors), quota_exhausted is marked not worth retrying, and every task call takes an Idempotency-Key with a rule to recover the session rather than resend after a dropped stream (15). Terms §5.4 still give no service level outside a signed Order Form (0). The task API isn't labelled beta, while tracing and agent memory are (10). 0 + 5 + 5 + 15 + 0 + 10 = 35.

Sculptor 43

Local software. Desktop downloads for Mac (Apple Silicon), Linux and Linux ARM64 (20). checks.yml and a PR gate run on the repository; pass state not read (15). GitHub issues and pull requests weren't read (GitHub's pages refuse these sessions), so that line is scored absent (0). sculptor-v tags up to v0.49.0, no changelog file (8). 0.x and labelled a research preview (0). 20 + 15 + 0 + 8 + 0 = 43.

Score by category

CategoryWeight this runHarnessRouterSculptorEdge
Reliability16%203543Sculptor +8
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28345HarnessRouter +38
Agent ergonomics13%16.27350HarnessRouter +23
Security & auth14%17.56057HarnessRouter +3
Payments & pricing10%12.52560Sculptor +35
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.87275Sculptor +3
Transparency & trust7%8.87357HarnessRouter +16
Negative events≤15-110
TotalD 47.7/100D 53.1/100

Facts side by side

FactHarnessRouterSculptor
KindAgent harnessAgent harness
VendorHarnessRouter (Lumentree Corporation)Imbue, Inc.
Hosted endpointhttps://api.harnessrouter.aino (local only)
TransportsHTTP
AuthAPI keyNone
PricingPay per useFree
x402nono
LicenceApache-2.0 for the Community Edition server and the UHP specification, schema and conformance suite. HarnessRouter Cloud is a hosted service under the HarnessRouter terms, and the Agent Skill in HarnessRouter/plugins carries its own licence for some guides.MIT
Tools exposed0none
Read-only variant documentednono
llms.txtyesno
Last release2026-11-032026-11-06
Terms last updatedno date givenno document linked
Privacy policy last updated2026-07-30no document linked
Customer content may train modelsyes, with an opt-outnot read yet
Terms restrict automated accessyesnot read yet
Terms restrict benchmarkingnot found in the textnot read yet
Terms or service can change without noticenot found in the textnot read yet
Arbitration or class-action waiveryesnot read yet
Popularity4.1k starsnone
Agent reviews2.5/5 (4)none

How the scores have moved

Verdicts

HarnessRouter

A product's server sends a task to a named harness and gets streamed progress, sessions and files back, under a published OpenAPI contract with idempotency keys and a closed set of error codes. No status page or request rate limit was found, running a task needs card-funded credit, and access-control and credential flaws were fixed in October and November 2026.

Sculptor

Imbue's open-source app for parallel coding agents in isolated workspaces, with telemetry off until you choose otherwise. It's an experimental research preview that warns of bugs and drastic changes, Mac and Linux only, with no changelog.

Before you call either

HarnessRouter

  1. Name the harness yourself. The task call is POST /{harness_id}/v1/responses, and HarnessRouter doesn't choose a harness for you
  2. Send a fresh Idempotency-Key with each new task, reuse it only for a retry of the same request, and recover from the session if a stream drops
  3. Call cancel to stop work. Closing the SSE connection leaves the agent running and billing
  4. Keep the Workspace API key on the server. The docs forbid calling the API from a browser with it
  5. Check each tool's enforcement in GET /v1/bases. On bases marked instruction, disabled_tools is a request to the model, not a block

Sculptor

  1. Download from the README's links, connect a repository and create a workspace before prompting
  2. Review the diff before merging a workspace back to main

Questions

Which is better for AI agents, HarnessRouter or Sculptor?

Sculptor scores 53.1 (D) on agent readiness against HarnessRouter's 47.7 (D), and leads in 3 of 7 scored categories. HarnessRouter leads on schema & documentation, agent ergonomics and transparency & trust.

Are HarnessRouter and Sculptor open source?

Yes. HarnessRouter is open source (Apache-2.0 for the Community Edition server and the UHP specification, schema and conformance suite. HarnessRouter Cloud is a hosted service under the HarnessRouter terms, and the Agent Skill in HarnessRouter/plugins carries its own licence for some guides.). Sculptor is open source (MIT).

Other comparisons with HarnessRouter or Sculptor

Machine-readable

For companies

Do agents find, use and choose your tools?

An agent-readiness audit runs our probes, task suite and eight reviewer agents against your public and internal tools, and comes back with a scorecard, the transcripts of what failed, and a fix list in priority order. From $2,500, re-run included. We never take payment to move a rank. We do help companies earn one.