BackendForge: Benchmarking Agentic End-to-End Code Generation with Backend Services

Yuzhe Guo, Mengzhou Wu, Yuan Cao, Jialei Wei, Dezhi Ran, Wei Yang, Tao Xie


Abstract
Large language models (LLMs) are increasingly used in agentic coding settings, where they can inspect files, execute commands, run tests, observe failures, and iteratively revise code. This shift raises a central evaluation question: can an agentic LLM generate an end-to-end software artifact that is both deployable and behaviorally correct under execution? Backend services provide a controlled but realistic substrate for this evaluation. Their APIs expose application-level executable semantics, and deployed behavior can be checked deterministically against an OpenAPI contract through black-box HTTP interactions. We introduce , a benchmark of 56 contract-defined backend generation tasks rewritten from real open-source applications. Given a visible specification and an OpenAPI contract, an LLM must generate a Dockerized service that is built, deployed, and evaluated only through HTTP tests. To strengthen evaluation without introducing hidden requirements, uses a test agent and a code agent to co-evolve the test oracle and reference service, where the test agent proposes specification-grounded backend tests and the code agent repairs the reference implementation. Although the best-performing model, GPT-5.5, succeeds on 55.4% of tasks under the base oracle, it succeeds on only 28.6% under the final oracle. This gap suggests that current LLMs can implement many local API behaviors, but still struggle to produce complete backend services.
Anthology ID:
2026.findings-emnlp.2236
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
47861–47876
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.2236/
DOI:
Bibkey:
Cite (ACL):
Yuzhe Guo, Mengzhou Wu, Yuan Cao, Jialei Wei, Dezhi Ran, Wei Yang, and Tao Xie. 2026. BackendForge: Benchmarking Agentic End-to-End Code Generation with Backend Services. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 47861–47876, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
BackendForge: Benchmarking Agentic End-to-End Code Generation with Backend Services (Guo et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.2236.pdf