Stateful File Viewer

Give the agent a windowed, line-numbered view of the open file with goto and scroll commands instead of flooding context with full-file dumps.

A stateful file viewer keeps an open path and shows a fixed window (for example 100 lines) with prepended line numbers and indicators of content above/below. Commands such as open, goto, scroll_down, and scroll_up mutate that state; subsequent guardrailed edits reference the same line numbers. Window size is a measured knob: ~100 lines beat both ~30 lines (~−3.7 pts) and dumping the entire file (~−5.3 pts) on SWE-bench Lite under ACI component ablation.

Shell-only inspection fails this job: cat floods context; head/tail are poor navigators; bash is stateless so “scrolling” regenerates long commands; interactive pagers map poorly to one-shot LM actions. Grounding edit and search in viewer output is a core agent-computer interface pattern — complementary action/observation pairs under context engineering. Prefer search_file / goto over linear hunting; blind scroll loops are a common regression once the agent abandons search inside multi-thousand-line files.

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Sources

• SWE-agent (Yang et al.), pp. 1–15 (§5); pp. 16–30