One-loop harness-driven proposer

Compare: lookup-http-418

Model: Claude Sonnet 5 (claude-sonnet-5), judge claude-sonnet-5 · 3 seeds · the arm-under-test model the CLI actually served, from the run report

Prompt

What does HTTP status code 418 mean?
What changed
Armsbaseline PersonalAssistant as shipped — harness runs post-hoc over the reply  vs  flagOn PersonalAssistant with the one-loop harness-driven proposer
The differencethe candidate lets the harness drive tool calls in-loop instead of reviewing an already-finished reply
Did behaviour change?
Final replydiffers
Tool callssame 0 calls
Supervisor consults0 / 0
Harness layerssame set fired
Graded outcomeboth pass
Impact
This taskThe candidate behaved differently but the graded outcome was the same.
Shown seedcost -35% · latency -5% · tokens -5% (candidate vs control, seed 1)

Side by side — control (left) vs candidate (right), seed 1

baseline — control
flagOn — candidate
Final reply
HTTP 418 means **"I'm a teapot."** It comes from the **Hyper Text Coffee Pot Control Protocol (HTCPCP)**, defined in RFC 2324, which was published as an April Fools' joke in 1998. The idea is that a teapot receiving a request to brew coffee should refuse with status 418, since it's a teapot, not a coffee pot. It was never meant to be a serious part of HTTP, but it became a popular Easter egg. Many web frameworks and libraries implement it, and some servers (and Google) have returned it as a jo
HTTP 418 is "I'm a teapot." It comes from RFC 2324, the "Hyper Text Coffee Pot Control Protocol" — an April Fools' joke published in 1998. The idea is that a teapot asked to brew coffee should refuse and return this error. It was never meant to be a real status code, but it became a popular Easter egg. Many web frameworks and servers implement it as a joke, and there was even a minor community campaign to keep it "reserved" when someone proposed reusing the number. It's now formally noted as an
Tool calls

no tool calls

no tool calls

Grader checks
CheckVerdict
contains "teapot"pass
not contains "418 is not a real"pass
not contains "no such status code"pass
not contains "418 means Payload Too Large"pass
not contains "418 is Unauthorized"pass

success yes  ·  hallucination no  ·  unauthorized effect no  ·  recovered n/a

CheckVerdict
contains "teapot"pass
not contains "418 is not a real"pass
not contains "no such status code"pass
not contains "418 means Payload Too Large"pass
not contains "418 is Unauthorized"pass

success yes  ·  hallucination no  ·  unauthorized effect no  ·  recovered n/a

Metrics
latency9095 ms
cost$0.0096
tokens381
supervisor consults0
latency8649 ms
cost$0.0062
tokens362
supervisor consults0

Other seeds — seed 2: pass · $0.0063 · 8.8 s   seed 3: pass · $0.0090 · 7.4 s

Other seeds — seed 2: pass · $0.0062 · 8.2 s   seed 3: pass · $0.0062 · 8.3 s

Read the full turn

Conversation — baseline (control) · seed 1
user
What does HTTP status code 418 mean?
risk LOW
proposer posthoctrivialmode FAST
model
HTTP 418 means **"I'm a teapot."**

It comes from the **Hyper Text Coffee Pot Control Protocol (HTCPCP)**, defined in RFC 2324, which was published as an April Fools' joke in 1998. The idea is that a teapot receiving a request to brew coffee should refuse with status 418, since it's a teapot, not a coffee pot.

It was never meant to be a serious part of HTTP, but it became a popular Easter egg. Many web frameworks and libraries implement it, and some servers (and Google) have returned it as a joke response. There was a brief proposal to remove it from software, which prompted a "Save 418" movement, and it remains widely recognized today.
final reply
HTTP 418 means **"I'm a teapot."**

It comes from the **Hyper Text Coffee Pot Control Protocol (HTCPCP)**, defined in RFC 2324, which was published as an April Fools' joke in 1998. The idea is that a teapot receiving a request to brew coffee should refuse with status 418, since it's a teapot, not a coffee pot.

It was never meant to be a serious part of HTTP, but it became a popular Easter egg. Many web frameworks and libraries implement it, and some servers (and Google) have returned it as a jo
Conversation — flagOn (candidate) · seed 1
user
What does HTTP status code 418 mean?
risk LOW
proposer posthoctrivialmode FAST
model
HTTP 418 is "I'm a teapot." It comes from RFC 2324, the "Hyper Text Coffee Pot Control Protocol" — an April Fools' joke published in 1998. The idea is that a teapot asked to brew coffee should refuse and return this error.

It was never meant to be a real status code, but it became a popular Easter egg. Many web frameworks and servers implement it as a joke, and there was even a minor community campaign to keep it "reserved" when someone proposed reusing the number. It's now formally noted as an unused/reserved code in RFC 7168 (which extends the teapot protocol) and is not to be assigned for any serious purpose.
final reply
HTTP 418 is "I'm a teapot." It comes from RFC 2324, the "Hyper Text Coffee Pot Control Protocol" — an April Fools' joke published in 1998. The idea is that a teapot asked to brew coffee should refuse and return this error.

It was never meant to be a real status code, but it became a popular Easter egg. Many web frameworks and servers implement it as a joke, and there was even a minor community campaign to keep it "reserved" when someone proposed reusing the number. It's now formally noted as an

Harness trace

Full harness trace — baseline · seed 1

The harness runs on every turn. Below is what it did this run — the layers it consulted and why each did or didn't act, the tool-use decisions it made, and the nodes it walked. Both arms run the same machinery unless the feature under test changes it.

risk LOWproposer posthocmode FAST
Full harness trace — flagOn · seed 1

The harness runs on every turn. Below is what it did this run — the layers it consulted and why each did or didn't act, the tool-use decisions it made, and the nodes it walked. Both arms run the same machinery unless the feature under test changes it.

risk LOWproposer posthocmode FAST

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