software tool builders

Abstract: The emergence of artificial intelligence (AI) coding agents has put pull requests under pressure: agents open millions of pull requests per month, while some open-source projects have begun to restrict or disable external contributions. We investigate which alternatives to pull requests practitioners are proposing or adopting and what these changes mean for empirical software engineering research. We reviewed 50 gray-literature documents from 31 organizations or individuals published between October 2025 and October 2026, coding the problems each named, the mechanisms it proposed or adopted, which of five roles of pull requests (integration, review, rationale, accountability, and external contribution) each mechanism takes over, and the evidence offered. Most responses retained pull requests in some form, whether by adding tooling, attaching a new artifact, or restricting access, and restriction was the response most often reported as adopted. Several proposed alternatives moved review and rationale into agent conversations and session records, but only Zed reported using a replacement in practice. Only two documents outlined a replacement for external contribution, and neither reported adoption. Pull requests are changing in ways that pull-request datasets will not capture: reviews conducted in agent conversations leave no pull-request comments, and projects that disable pull requests disappear from samples of newly opened ones. We outline a research agenda on the effectiveness of the emerging alternatives, their consequences for open-source participation, and the adaptation of empirical methods.

Abstract: Android Application Programming Interfaces (APIs) continuously evolve, causing existing APIs to become deprecated and requiring developers to migrate their usages to recommended replacements. Although prior studies have proposed automated migration techniques, their effectiveness is often limited by the diversity and contextual complexity of API changes. This paper presents a systematic study of deprecated Android APIs, their recommended replacements, and real-world usage updates performed by developers. Based on an analysis of 1,000 deprecated APIs and 4,336 migration examples collected from GitHub, we identify six migration categories and derive recurring usage-update patterns involving Android-version checks, parameter adaptation, object initialization, data-type conversion, and changes in API interaction mechanisms. To assess their applicability, we augment the zero-shot GUPPY benchmark prompts with the migration category and corresponding usage-update pattern. On 156 benchmark tasks, the pattern-guided prompt improves correct updates from 139 to 147 and performs better in five of the six categories.

Abstract: Terminal-agent capability depends jointly on model weights and the runtime harness that formats prompts, binds tools, and handles error recovery. Existing harness-model co-evolution approaches improve both components, yet often treat trajectories produced during harness search as an undifferentiated replay buffer. This practice overlooks that a trajectory's value for model training depends on the harness under which it was generated. To systematically analyze this interface, we establish an alternating co-evolution framework that decouples harness search and policy training through component-wise promotion decisions. Within this framework, we introduce CoTrace, a harness-aware data recipe that explicitly governs trajectory routing, provenance matching, and curriculum refresh. Under CoTrace, recurring execution failures guide harness synthesis, while policy training is strictly conditioned on verified rollouts matched to the adopted runtime for supervised fine-tuning (SFT) or fresh online interactions for reinforcement learning (RL). On the Tmax promotion split, CoTrace advances Qwen3.5-9B from 78 to 88 solved tasks under supervised fine-tuning while an online reinforcement variant reaches 90. Specifically, a compact harness-matched corpus produces steady model gains at substantially lower compute than much larger corpora pooled across sibling harnesses. Furthermore, evaluations on Terminal-Bench 2.1 and SWE-bench Lite show that out-of-distribution transfer depends fundamentally on harness compatibility, where maintaining consistency between training and evaluation runtimes prevents procedural execution breakdowns observed under foreign scaffolds.

Abstract: Large language models (LLMs) receive each user message as plain text, even when it combines text from different sources. For example, a user may paste text into a prompt and keep typing a comment directly below it. We study absorption: a phenomenon where the model treats a trailing user comment as part of the pasted text, returning it inside the edited text. This happens even though the user did not intend the comment to become part of that text. Existing instruction-data separation benchmarks tell the model which text is instruction and which is data, then test whether it obeys that separation. They do not test harmless user speech following an unmarked paste. We introduce SEAM, a controlled benchmark of 300 editing examples. Each example is tested under six matched conditions that vary how the boundary between pasted text and later user speech is expressed. Across 20 models, absorption at a bare newline ranges from 7.7% to 66.7%. Adding a blank line does not significantly reduce absorption in any model, while boundary markers reduce it in 19 of 20 models. Comments that fit the pasted text, such as a code comment typed after code, are absorbed significantly more often in 17 of 20 models. Models often fail to separate pasted material from later user speech, and explicit boundaries reduce but do not remove this failure.

Abstract: Evaluating code data as a single corpus can obscure which types of code data benefit which models and downstream tasks. Effective data selection requires understanding both the benefits of individual categories and whether these benefits persist when categories are combined. We introduce a decompositional lens for studying these effects in LLM post-training. We first decompose an execution-verified code corpus into interpretable categories based on the computational patterns of its solutions. Through controlled fine-tuning experiments, we compare individual categories with a balanced mixture across instruction-tuned models on question answering, mathematics, and code generation. The resulting response maps reveal recurring gains in average question-answering performance, while the same category can improve one model or task and degrade another. The best-performing category also varies with the starting model and target task. We then compose compact mixtures guided by these results and examine whether benefits observed in individual categories persist under joint training. On selected model--task pairs, mixtures whose constituents each improve the target task outperform both their best constituent and full-corpus training while using roughly 10--15\% of the full corpus. These exploratory findings illustrate a \emph{less is more} pattern and highlight how the value of code data in post training depends on which categories are combined for which model and task.