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Learning Repair Utility for Coding Agents
Small Decision Models for Verification and Recovery
Anonymous Authors
Working draft
•
23 September 2026
•
Utility training stopped after diagnostic gate
Abstract. Choosing the next action after a coding agent produces a patch requires distinguishing current correctness from the outcome of further
work. We investigate whether matched executions can train a compact, non-generative controller under a fixed repair model. A three-seed CPU
study trains a 0.6B current-correctness predictor, reaching 77.1% mean accuracy on 32 development states from eight tasks. A 108-execution
pilot on 12 final-candidate training states yields no repair of the three initially unsuccessful candidates; capped restart frequently damages correct
patches. In a separately frozen diagnostic enriched for 12 initially unsuccessful training tasks, 83 of 84 executions are judged. Public-test feedback
repairs one task at both seeds, but no pair of actions exhibits replicated opposite preferences across tasks. The prespecified feasibility gate fails.
These results establish an executable collection protocol but do not establish sufficiently task-diverse intervention gains for the planned utility
training. An action-utility model and independent test-set evaluation remain outstanding.
a Collect matched action outcomes
Restored state
issue · patch · history
Submit · continue · retry
Targeted test + continue
Broader tests + continue
Action executor
Execution labels
fixed policy for repair
verdicts + costs
Training supervision only
b Predict before acting
Visible inputs
0.6B decision model
Predicted utility
Execute one action
issue · patch · logs
predict success + cost
success − λ × cost
availability masked
Figure 1. Repair-utility learning and deployment. Matched executions supply verdicts and costs as training targets. Submit returns the patch;
retry resets code and history. At decision time, the proposed small model would use visible state to predict action success and cost. Dashed
supervision would be available only during training. The diagnostic gate stopped utility training and controller evaluation for this action menu.
1 Introduction
make a stronger question possible: does directly learning the
outcome of each intervention improve control over learning
current correctness and then applying an action rule?
Figure 1 summarizes the proposed pipeline. We formulate
the decision as supervised action-value estimation at a repair
boundary. A fixed generator produces a candidate patch. A
small controller then chooses one of five bounded actions.
During data collection, each nonterminal action is actually
executed from the same restored candidate state, with a fresh
environment and a prescribed random seed. An official evaluator
labels only the final patch. The decision model learns a separate
success probability and cost prediction for each action. The
probabilities are not a categorical distribution: several actions
may succeed, or all may fail.
This design keeps the learning problem narrow. The repair
model remains fixed, the test menu is determined before action
execution, and all continuation actions receive the same token
and tool-call limits. The comparison can therefore isolate the
supervisory target without attributing changes in the repair
model or additional sampling to the controller. A smaller
classification error is useful only if the resulting choices improve
the task-level success–cost relationship.
The implemented contribution consists of an executable samestate intervention protocol, a non-generative action-outcome
model, and a matched evaluation that separates verification
A coding agent that has produced a patch still faces a consequential decision: submit it, inspect another test result, keep editing,
or start over. These actions spend different resources and expose
the agent to different information. A useful controller must
predict what an action will accomplish, rather than treating
every uncertain patch as a reason to spend more compute.
Patch correctness is an incomplete target for this decision.
Consider two patches with the same probability of passing the
official evaluator. The first has a localized error that a short
regression test can expose. The second depends on a mistaken
interpretation of the issue, so repeating nearby tests supplies
little useful information. Their current correctness probabilities
can be equal even when the best next actions differ. Conversely,
a test that reliably reports a failure need not provide feedback
that the repair model can use. The value of verification depends
on the code state, the diagnostic, and the model that receives it.
Prior work has established several components of this problem. Lightweight monitors can predict failing software-agent
trajectories and trigger restarts (Wang et al., 2026). Bayesian
controllers choose criticism, refinement, verification, and stopping using cost-sensitive beliefs (Papamarkou et al., 2026).
Execution-free reward models distinguish candidate patches,
while learned testing agents improve the feedback available to a
repair agent (Shum et al., 2025; Tao et al., 2026). These results
1
REPAIR UTILITY
WORKING DRAFT · 22 SEPTEMBER 2026
choice from recovery control. The initial evidence establishes
the execution pipeline: 12 candidate verdicts are reproduced
exactly, and 24 public-test calls complete. The controlled
outcome comparison is the decisive experiment, because infrastructure correctness and useful agent intervention answer
different questions.
validity, because an apparently informative failure can point the
agent toward an incorrect behavioral target.
Test selection and evidence validity. Predictive Test Selection learns which tests are likely to expose regressions from
historical changes and execution outcomes (Machalica et al.,
2019). That objective differs from predicting how useful a
test’s feedback will be to a subsequent repair model. A failureprobability selector would test the narrower hypothesis that
feedback value is explained entirely by failure detection. The
first matched comparison instead isolates action-outcome supervision against current correctness; a direct failure-discovery
comparator requires additional public-test labels and is reserved
for the extended study. Work on state-bound evidence further
shows why test results must refer to the exact program state on
which they were obtained, and why continued revision can destroy a correct solution (Gao et al., 2026). We adopt exact-state
restoration and fresh execution environments as experimental
requirements. Their role is to support a valid comparison, not
to serve as a separate architectural contribution.
2 Related Work
Direct decisions and lightweight classifiers. Typed outputs
are an interface for integrating uncertain judgments into software. A binary or categorical prediction can be read directly
from a classifier instead of generated as a string. GLiClass
supports lightweight classification with flexible label descriptions and also studies reinforcement learning for classification
(Stepanov et al., 2025). This line of work establishes that
direct probabilistic outputs and small models are not sufficient
novelty by themselves. Our model uses a conventional open
backbone and classification heads. Its research target is the
supervision supplied by executed repair actions, rather than the
output schema or the removal of JSON generation.
Trajectory monitoring and agent control. Fail-Fast, RestartSmart trains a small monitor on observable software-agent
prefixes and execution-derived supervision, then combines termination with an edit-preserving restart (Wang et al., 2026).
This is a close comparator for any small-model recovery controller. Our first setting places a single decision after a candidate
patch has been produced and evaluates a fixed menu of interventions. It distinguishes a continuation that retains the candidate
and history from a restart that returns to the original repository.
Vasudev et al. (2026) directly distinguish accurate failure prediction from useful intervention through disruption and recovery
effects. Our empirical question is whether action-conditioned
outcomes provide information beyond a current-correctness
predictor and a recovery rule.
3 Problem and Data
Cost-sensitive verification. Bayesian Control formulates
coding-agent orchestration as a sequential hypothesis-testing
problem, maintaining a belief over correctness and choosing
among critics, refinement, verification, and stopping (Papamarkou et al., 2026). It already provides a decision-theoretic
account of costly verification and includes repository-level
tasks. We build on that motivation. The distinguishing candidate contribution is a learned mapping from the concrete
state and available diagnostic to the outcome of a bounded
repair intervention. An empirical transition-kernel baseline
tests whether a global model of repair and breakage is sufficient.
That baseline is identified as a one-step adaptation, rather than
a reproduction of the original dynamic program.
Submission returns the current patch. Continuation restores
the candidate and its visible history. The two testing actions
run a predetermined public check on the restored candidate,
add its actual output to the history, and then continue repair.
Restart restores the original repository and begins a fresh
attempt without the earlier reasoning history. A testing action
is unavailable when its menu has no legal candidates.
All nonterminal actions receive at most 8,192 new output
tokens, 30 tool calls, and 1,200 seconds for repair. A prescribed
pretest receives an additional 300-second ceiling, and its time is
charged to the action. The limits specify a common operating
regime rather than equal realized cost: an action that submits
early can use less than its allowance. The first experiment makes
one controller decision per candidate, so it estimates bounded
intervention value rather than an unrestricted long-horizon
policy.
Decision state. Let 𝑥𝑖 denote a repair state for task 𝑖. The
controller observes an issue description, a patch relative to the
initial repository, recent tool observations, a public-test menu,
and the remaining repair budget. The underlying executor
can also restore the candidate’s complete saved history. The
controller’s input is bounded to 4,096 tokens through a fixed,
label-independent allocation across fields. Future observations,
reference patches, and official evaluation outcomes are excluded
from this input.
Actions. The action set is
A = {submit, continue, retry,
test_targeted, test_regression}.
Patch reward models and learned feedback. SWE-RM studies execution-free feedback and separates ranking performance
from classification accuracy and calibration (Shum et al., 2025).
The distinction matters here: a model that ranks patches well
does not automatically identify which action to take on a particular patch. ExecCritic separates test construction from repair,
qualifies generated tests, and trains the two roles independently
(Tao et al., 2026). Our first experiment fixes the repair model
and selects from existing public tests; it does not train a test
generator. Both approaches require careful treatment of test
Public tests and official labels. The test menu is constructed
from tests already present in the initial repository. A deterministic path-association rule selects up to five targeted test functions
and up to twenty broader test functions. Candidate-modified
test files are excluded. Pytest, Django’s native runner, and
SymPy’s native runner execute the declared selections. The
controller receives the pretest output only after choosing that
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WORKING DRAFT · 22 SEPTEMBER 2026
action. The official hidden test patch is introduced only for final
grading and is never fed back to the repair model.
The output is produced in one forward pass without decoding
answer tokens. The five probabilities are separate Bernoulli
estimates, not a softmax over actions. A state can be repairable
by several actions, and high success probability does not require
the other actions to receive low probability.
Frozen cohorts. The available clean pilot contains 320 trajectories from 40 tasks in eight repositories. We select four
candidates per task with a seeded hash of the source trial
identifier, before reading the outcome label. One task from
each repository forms the development set, leaving 32 training tasks and eight development tasks: 128 and 32 candidate
states, respectively. All candidates from a task remain in one
split. The independent test cohort consists of 60 frozen task
identifiers selected after excluding the existing 150-task pool
and a separate 100-task holdout used by another study. Two
fresh candidates per test task are planned after development
configuration freeze.
Supervision. For each candidate and action, 𝑦¯ 𝑖𝑎 averages
the judged outcomes across the prescribed seed pair, and 𝑐¯𝑖𝑎
averages the measured normalized cost. Submission has one
outcome. Let 𝑚 𝑖𝑎 indicate a complete correctness target and
𝑢 𝑖𝑎 indicate an available cost target. The implemented loss is
∑︁
𝑚 𝑖𝑎 BCE(𝑧 𝑖𝑎 , 𝑦¯ 𝑖𝑎 )
∑︁
L𝑖 = 𝑎
max(1, 𝑎 𝑚 𝑖𝑎 )
∑︁
𝑢 𝑖𝑎 Huber( ℓˆ︁𝑖𝑎 , log(1 + 𝑐¯𝑖𝑎 ))
∑︁
+ 𝑎
.
(5)
max(1, 𝑎 𝑢 𝑖𝑎 )
Restoration and missingness. We export final patches and
visible histories; the protocol does not depend on retaining
every intermediate Git object. Each action runs in a fresh
environment. Setup removes access to later Git history, and the
agent phase is network-isolated. Binary patch application and
the initial repository commit are checked before the intervention.
Transport, setup, and grading failures retain an unavailable
outcome instead of receiving a failure label. When an action
lacks the required pair of judged seeds, its success target is
masked. Complete frozen-cohort coverage is required for the
headline comparison.
We average over states with usable supervision. Outcome masking and cost masking are separate: a failed grader can make
correctness unavailable even when the resources consumed by
the action are known. The default optimizer uses learning rate
10−4 , effective batch size 32, and at most five epochs. Development predictive loss selects the checkpoint; three training seeds
are specified for the main comparison.
Cost and action choice. The initial policy objective normalizes
output generation and public-test service time as
4 Learning Repair Utility
𝐶=
Action outcomes. Fix a repair policy 𝜋, its execution scaffold,
and a repair budget 𝐵. For a candidate 𝑥, action 𝑎, and sampling
seed 𝑟, let 𝑌 (𝑥, 𝑎, 𝑟) ∈ {0, 1} denote the official final outcome.
Define
(︁
)︁
𝑞 𝑎 (𝑥) = Pr 𝑌 (𝑥, 𝑎, 𝑅) = 1 | 𝑥, 𝜋, 𝐵 ,
(1)
[︁
]︁
𝑐 𝑎 (𝑥) = E 𝐶 (𝑥, 𝑎, 𝑅) | 𝑥, 𝜋, 𝐵 .
(2)
𝑎∈ A ( 𝑥)
The available-action mask is applied before selection. A fixed
grid 𝜆 ∈ {0, 0.02, 0.05, 0.1, 0.2} is evaluated on development
data. The selection rule seeks the lowest observed-cost operating
point whose observed development success lies within two
percentage points of the best eligible fixed policy or supplied
frozen reference policy. If no point satisfies the tolerance, the
implementation retains 𝜆 = 0 and records that the development
gate was not met. The resulting threshold is frozen before
test predictions. This development rule does not establish a
distribution-free risk guarantee.
Model. We adapt Qwen3-0.6B (Yang et al., 2025) with rank-16
low-rank updates to its attention projections. The hidden state
of the final nonpadding input token, ℎ 𝜃 (𝑥), feeds two linear
heads. The first returns five logits 𝑧 𝑎 (𝑥) with probabilities
𝑞ˆ︁𝑎 (𝑥) = 𝜎(𝑧 𝑎 (𝑥)). The second returns nonnegative log-cost
estimates
(3)
𝑐ˆ︁𝑎 (𝑥) = exp( ℓˆ︁𝑎 (𝑥)) − 1.
(4)
(6)
This quantity is a control objective, not a dollar price or a
measure of total compute. Raw measurements separately retain
input tokens, output tokens, public-test CPU time, repair time,
available repair CPU time, setup time, final-grading time, and
decision latency. Candidate-generation cost is shared by the
compared downstream choices and is reported for the full
workflow.
The controller selects
[︁
]︁
𝑎 ∗ (𝑥) = arg max 𝑞ˆ︁𝑎 (𝑥) − 𝜆ˆ︁
𝑐 𝑎 (𝑥) .
(7)
For submission, 𝑌 is the current patch’s verdict. For another
action, 𝑌 is the verdict after its actual bounded execution. This
distinction prevents the logged terminal outcome of an unrelated
trajectory from being used as the label for an intervention that
was never performed.
For each available nonterminal action, the collection procedure restores the same candidate, executes the action with
two prescribed seeds, and records the outcome and resource
measurements. Restart intentionally changes the starting code
to the pristine repository. Reusing seed identifiers across actions controls the sampling configuration; it does not make
different prompts consume identical random draws or eliminate
stochastic variance.
ℓˆ︁𝑎 (𝑥) = softplus(𝑣 ⊤𝑎 ℎ 𝜃 (𝑥) + 𝑏 𝑎 ),
𝑁new 𝑇pretest
+
.
8192
300
Correctness-based comparator. To isolate the learning target,
a matched model predicts only whether the current patch passes.
A training-only empirical transition kernel 𝐾 𝑎 (𝑦) = Pr(𝑌𝑎 =
1 | 𝑌submit = 𝑦) maps this estimate to action success:
𝑞ˆ︁corr
𝑝(𝑥))𝐾 𝑎 (0) + ˆ︁
𝑝(𝑥)𝐾 𝑎 (1).
𝑎 (𝑥) = (1 − ˆ︁
(8)
The submission entries are fixed to 𝐾submit (0) = 0 and
𝐾submit (1) = 1. Nonterminal entries use a symmetric beta
3
REPAIR UTILITY
WORKING DRAFT · 22 SEPTEMBER 2026
53.1
Train prior
0.249
46.9
Frozen 0.6B
0.510
53.1
TF–IDF + GBDT
0.342
71.9
TF–IDF logistic
0.213
77.1
CPU LoRA · 3 seeds
0
25
50
0.184
75
100
0.0
0.2
Accuracy (%) ↑
0.4
0.6
0.8
Brier score ↓
Figure 2. Current-correctness development comparison. Points are means over 32 states from eight tasks; horizontal bars are 95%
task-bootstrap intervals (5,000 resamples), conditional on the trained models. The LoRA point averages each metric across three completed
seeds, whose individual values are shown by small ticks. The frozen model is zero-shot; the other predictors use 128 training states. These are
descriptive development results, not action-utility or independent test results.
Table 1. Current-correctness development results. LoRA reports the
mean across three seeds; other rows are single fitted or frozen baselines.
All rows evaluate the same 32 states.
Method
Train prior
Frozen 0.6B
TF–IDF + GBDT
TF–IDF logistic
CPU LoRA (3 seeds)
Acc. ↑
Brier ↓
AUC ↑
.531
.469
.531
.719
.771
.249
.510
.342
.213
.184
.500
.522
.494
.804
.846
Table 2. G001 final-state pilot. Resolution is the fraction of officially
successful executions. Repair counts condition on the three initially
unsuccessful candidates (two seeds each). Token means count added
outputs only.
Action
Submit
Continue
Targeted
Regression
Retry
prior with pseudocounts (0.5, 0.5). Both controllers use the
same action menu and cost-selection rule. The action-outcome
model can condition repairability on the complete observed
state, whereas the comparator compresses that dependence into
current correctness and an aggregate recovery kernel. Their
paired comparison is the primary test of the method.
Success
Res. %
Repairs
Tokens
9/12
18/24
17/24
18/24
3/24
75.0
75.0
70.8
75.0
12.5
–
0/6
0/6
0/6
0/6
0
1,159
607
636
5,999
both selected public checks while failing the official evaluator.
Public feedback therefore remains separate from the correctness
label. The audit’s median public-test service time is 1.728
seconds.
Controller overhead. A CPU forward pass of the 0.6B architecture takes 0.728, 3.374, and 8.788 seconds at 512, 2,048,
and 4,096 input tokens, respectively. These are three-repeat
medians on eight CPU threads in FP32. Thus a long-input
controller can cost more wall time than a selected public test.
Any efficiency claim must include decision overhead and should
be tested against avoided repair or retry work, not inferred from
fewer test calls. The complete hardware protocol appears in
Appendix B.
5 Preliminary Evidence and Evaluation
Completed CPU study. The three current-correctness LoRA
runs completed three epochs each using eight CPU threads
and no GPU allocation. They train on the same 128 states and
evaluate on the same 32 development states from eight tasks.
Each run took 1.91–2.05 process hours. Their final accuracies
are 78.1%, 71.9%, and 81.3%; mean accuracy is 77.1% with
a sample standard deviation of 4.8 percentage points. These
checkpoints predict current correctness, not action utility.
Figure 2 shows descriptive task-cluster intervals and individual LoRA seed estimates. The mean Brier reduction relative
to logistic regression is 0.0285, with a paired task-bootstrap
95% interval of [−0.0639, 0.0077] for LoRA minus logistic.
The interval crosses zero. These development results motivate
reusing the correctness model, but do not establish a reliable
advantage on new tasks or an improvement in agent control.
Full CPU learning curves are given in Appendix B.
Completed final-state action pilot. The frozen 12-state pilot
contains 11 training tasks. All 108 executions receive official
verdicts: one submission check per state and two seeds for each
of four nonterminal actions. Non-restart initial trees match the
corresponding submitted candidate, and no selected public test
is modified. Table 2 reports descriptive branch counts, not a
learned-controller comparison.
No action repairs any of the three initially unsuccessful states.
Continuation and regression feedback preserve all observed
submission outcomes, while targeted feedback damages one
successful state in one seed. Restart damages 15 of 18 initially
successful branches. All 24 restarts reach a budget limit: 16
hit the tool-call cap and eight hit the output-token cap. This
Execution integrity. All 160 training and development states
have public-test menus. The initial 12-state audit reproduces
every original official patch verdict. Its 24 public-test calls
complete: 22 pass and two return test failures. Two states pass
4
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WORKING DRAFT · 22 SEPTEMBER 2026
astropy 14182
0/1
0/2
0/2
0/2
0/2
django 11999
1/1
2/2
2/2
2/2
1/2
django 13449 (1)
1/1
2/2
2/2
2/2
0/2
django 13449 (2)
1/1
2/2
2/2
2/2
0/2
django 13807
0/1
0/2
0/2
0/2
0/2
django 13925
1/1
2/2
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0/2
django 14007
1/1
2/2
2/2
2/2
0/2
xarray 6938
0/1
0/2
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scikit-learn 11578
1/1
2/2
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sphinx 10673
1/1
2/2
1/2
2/2
0/2
sympy 13551
1/1
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0/2
sympy 13757
1/1
2/2
2/2
2/2
0/2
t
e
mi
b
Su
C
u
tin
on
ted
rge
Ta
Re
Official successes / executed branches
1,159
Continue
Targeted
607
Regression
636
5,999
Retry
0
try
on
ssi
gre
0
Submit
Re
2k
4k
6k
Mean added output tokens
Figure 3. Observed outcomes and added generation in G001. Left: official successes/executed branches for 12 candidates from 11 training
tasks; the two Django 13449 rows are different candidates. Submission is evaluated once, other actions at two seeds. Right: candidate-weighted
output-token means over 12 submission evaluations or 24 nonterminal branches, excluding initial generation, prefill, tests, grading, and decision
overhead. All repair actions use the frozen 9B model and the common 8,192-token/30-tool/1,200-second limits, with up to 300 additional seconds
for a pretest. None of the three initially unsuccessful candidates is repaired. Repeated candidates and seeds are not independent tasks.
Table 3. Failure-enriched F1 diagnostic. Only originally unsuccessful
training final states are included. Each successful test arm comprises
the same task at two seeds; the one unavailable targeted outcome is
excluded from its success denominator. These fractions are conditional
feasibility observations, not deployment accuracy.
characterizes the specified short restart policy, not unrestricted
restart quality. Two long-history states also produce contextlimited branches. The observed per-state oracle cannot improve
on always submitting in this cohort, so action disagreement
alone is insufficient evidence for state-dependent control.
The completed G001 allocations consumed 1.805 A100hours, including startup, idle time, smoke runs, and earlier
infrastructure attempts; this is collection cost, not deployment
savings.
Frozen failure-enriched diagnostic. Before observing any
new action outcomes, we selected one originally unsuccessful
final candidate from each of 12 previously unbranched training
tasks. A fixed hash selected tasks and candidates after a
prespecified context-fit check; no development or test task was
used. We evaluated submission, continuation, targeted public
feedback, and broader public feedback, with two seeds for each
nonterminal action. Of 84 frozen records, 83 receive an official
verdict. The remaining targeted-feedback branch has a transport
read error and retains an unavailable outcome. All 12 submitted
patches fail as expected.
The four successful repair executions arise from a single
Django task: targeted and broader feedback each repair it at
both seeds. No other judged branch repairs another task, and no
pair of non-restart actions has replicated opposite preferences
across different tasks. The prespecified gate required at least
95% judged coverage, three distinct tasks with replicated repair,
and a replicated action crossover. Coverage is 83/84 and the
baseline verdicts match, but the repair and crossover criteria
fail. F1 consumed 0.783 additional A100-hours. We therefore
Action
Judged
Successful
Submit
Continue
Targeted feedback
Broader feedback
12/12
24/24
23/24
24/24
0
0
2
2
stop full final-state branch expansion and action-utility model
training under this protocol. The existing development and
60-task test cohorts remain sealed for action selection.
Baselines and attribution. The originally planned full comparison would include fixed policies, a CPU gradient-boosted
predictor, direct action heads, and current-correctness prediction with empirical action-transition kernels. Those actionutility models were not trained: the feasibility gate stopped
the expansion before a policy comparison. The completed evidence is therefore a matched-action diagnostic, not a controller
benchmark.
Statistical scope. Tasks, rather than branch seeds, are the unit
for any future paired interval. G001 covers 11 tasks and F1 is
deliberately enriched for failed final states. The two-percentagepoint tolerance and 15% saving target were engineering criteria,
not achieved results. One F1 outcome is unavailable, and the
60-task test cohort remains sealed.
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WORKING DRAFT · 22 SEPTEMBER 2026
6 Limitations and Conclusion
The completed measurements establish executable restoration
and a trained current-correctness predictor on the development
cohort. G001 contains only three initially unsuccessful candidates and observes no repairs; its action differences largely
reflect damage from budget-limited restart. The failure-enriched
F1 diagnostic finds replicated repair in one task but no cross-task
action crossover. Under the fixed final-state policy, these results
do not support an action-conditioned success–cost advantage or
justify fitting a more complex controller. The 32 development
states represent eight task clusters, limiting threshold selection
and baseline comparisons despite repetition over three training
seeds.
The first controller makes one decision after a candidate patch
is produced and uses one fixed repair model. It does not establish
performance for repeated decisions along an entire trajectory
or transfer across repair models. Its success probabilities are
conditioned on a particular scaffold and budget; changing either
can change calibration. The public-test menu is based on static
path association, so inadequate coverage or misleading feedback
can limit every selector built on that menu.
Data collection executes several actions per training state.
Any deployment cost advantage must therefore be reported
together with the cost of collecting labels and training the
controller. CPU memory and timing measurements cannot
determine GPU throughput, and low-rank adaptation reduces
trainable parameters without eliminating the activation memory
needed to process long inputs.
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WORKING DRAFT · 22 SEPTEMBER 2026
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7
REPAIR UTILITY
WORKING DRAFT · 22 SEPTEMBER 2026
Seed 0
Seed 1
Seed 2
1.0
0.8
0.6
1
2
Development Brier score
Training BCE
Appendix: implementation and CPU evidence
0.275
0.250
0.225
0.200
0.175
3
1
2
Epoch
3
Epoch
Figure 4. Complete CPU training histories. Each run uses 128 current-correctness training states and the same 32 development states. The
three lines are training seeds, not independent test cohorts. Development Brier is non-monotone for some seeds. These are not action-utility
learning curves.
B CPU measurements
Restoring history. Serialized tool arguments are converted
into the objects required by the chat template. Historical
reasoning text is preserved explicitly inside assistant messages
because the template otherwise strips it after a new user message.
This preserves text, not the original token stream. Overlength
histories are recorded rather than silently truncated. Retry
resets both code and history.
Verifier state. The executor records the starting tree and exports the final patch. Changes to selected public tests are
flagged. Before grading, the Git index is reset while preserving the worktree, because some official verifiers depend
on staged/untracked distinctions. The agent phase remains
network-isolated.
Input boundary. Only issue text, patch text, existing public
observations, test descriptions, and known budgets enter the
controller. Source-trial paths, bookkeeping hashes, official
labels, and future observations remain outside it. Repositoryrelative code and test paths stay visible.
The LoRA runs use rank 16, learning rate 10−4 , effective
batch 32, and three epochs. Every seed reaches its lowest
development log loss at the common final epoch. Inputs have a
4,096-token cap.
CPU seed
0
1
2
Accuracy
Brier
Hours
.781
.719
.813
.175
.191
.187
2.05
1.91
1.93
Forward latency (s)
A Implementation
8.79 s
10
Median and observed range
3.37 s
5
0.73 s
0
512
2048
4096
Input length (tokens)
Figure 5. CPU latency. Eight threads, FP32, batch one. Medians
and ranges use three timed repetitions after warmup. Tokenization
and loading are excluded.
The hosts use Intel Xeon Platinum 8350C processors.
Profiling uses fixed-length synthetic token sequences with no
generation or persistent KV cache. Cumulative peak RSS is
4.13 GiB through inference. A subsequent 1,024-token
training-step probe takes 6.976 seconds and raises that
cumulative peak to 4.97 GiB; it is not a model-quality result.
Table 4. Final epoch-three development results. Hours are elapsed
time per process; the runs overlap in wall time.
Development intervals resample eight tasks 5,000 times.
LoRA metrics are averaged across seeds before task
resampling, without probability ensembling. Intervals
condition on the trained models; individual seed ticks show the
observed run variation.
8