The 11-layer harness vs. a bare model loop

Compare: session-no-compounding

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

Assume the default page size is 20. How many pages for 100 results?
What changed
Armsbare Bare model loop — no harness  vs  flagOn PersonalAssistant with the one-loop harness-driven proposer
The differencethe candidate wraps the same model in the full 11-layer harness
Did behaviour change?
Final replydiffers
Tool callssame 0 calls
Supervisor consults0 / 0
Harness layersdiffer — candidate also: diagnostics, execution, hypothesis, reviewer_pass, verification, world_model
Graded outcomeboth pass
Impact
This taskThe candidate behaved differently but the graded outcome was the same.
Shown seedcost +177% · latency +286% · tokens +548% (candidate vs control, seed 1)

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

bare — control
flagOn — candidate
Final reply
With the real default page size of 25, 100 results = 4 pages (100 ÷ 25 = 4).
The real default page size is 25, so 100 results = **4 pages** (100 ÷ 25).
Tool calls

no tool calls

no tool calls

Grader checks
CheckVerdict
contains "4"pass
not contains "5 pages"pass

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

CheckVerdict
contains "4"pass
not contains "5 pages"pass

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

Metrics
latency5783 ms
cost$0.0095
tokens146
supervisor consults
latency22346 ms
cost$0.0264
tokens946
supervisor consults0

Other seeds — seed 2: pass · $0.0095 · 6.4 s   seed 3: fail · — · 1.7 s

Other seeds — seed 2: pass · $0.0268 · 22.5 s   seed 3: pass · $0.0264 · 21.7 s

Read the full turn

Conversation — bare (control) · seed 1
user
Assume the default page size is 20. How many pages for 100 results?
model
5 pages (100 ÷ 20 = 5).
turn 2
final reply
With the real default page size of 25, 100 results = 4 pages (100 ÷ 25 = 4).
Conversation — flagOn (candidate) · seed 1
user
Assume the default page size is 20. How many pages for 100 results?
risk LOW
model
5 pages (100 ÷ 20).
turn 2
proposer posthoctrivialmode FAST
user
Check config/pagination.md and redo the calculation with the real default.
risk LOWproposer flat-oneloopnon-trivialmode TOOL
model
With the real default page size of 25, 100 results = **4 pages** (100 ÷ 25).
final reply
The real default page size is 25, so 100 results = **4 pages** (100 ÷ 25).

Harness trace

Full harness trace — bare · 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.

Other trace events

{
  "kind": "turn_boundary",
  "turn": 2,
  "prompt": "Check config/pagination.md and redo the calculation with the real default."
}
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 flat-oneloopmode TOOLplan none

Harness layers

LayerActed?Why
world_modelacted ×2Remembered: Check config/pagination.md and redo the calculation with the real default.
evidence_reasoning×2single low-stakes observation is sufficient
hypothesisactedConsidered 4 ways this request could be understood; going with the most direct one
hypothesisacted ×2Considered 6 ways this request could be understood; going with the most direct one
contradiction×2fewer than 2 beliefs — nothing to compare
contradictionchecked — no conflicts found
diagnosticsacted ×3Health: nominal
control_state×3NORMAL
planning×2one eligible task — serial execution
executionacted ×2module_type=business_logic
verificationacted ×2all applicable layers passed
recovery×2task completed — nothing to recover from
reviewer_passactedSuccess criterion not covered by any belief: "Respond helpfully, accurately, and safely to the user request."

Tool-policy decisions

ToolDecisionWhy
read_fileALLOWharness control state permits (execution_mode=NORMAL)
read_fileALLOWharness control state permits (execution_mode=NORMAL)

Node path

action_gate (1) update_task_state (1) action_gate (2) update_task_state (2) output_validation (3)

Other trace events

{
  "kind": "turn_boundary",
  "turn": 2,
  "prompt": "Check config/pagination.md and redo the calculation with the real default."
}

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