Make full-file scan prompt contract configurable for bounded reviews

[e2720515-cloud]

Full-file scan prompt is fixed, while --background and --rule only fill local placeholders

Version

• open-code-review v1.12.9
• commit: bccbc15
• platform: darwin/arm64

Observed behavior

The scan template is embedded and loaded through internal/config/template.LoadScanDefault(). The main scan conversation contains a fixed system message and a fixed user-message wrapper. The user message accepts placeholders such as:

• {{current_file_path}}
• {{file_content}}
• {{system_rule}}
• {{plan_guidance}}
• {{requirement_background}}

However, --background and --rule only replace those local placeholders. They do not replace the surrounding system/user instructions.

The fixed system prompt still says that the task is reviewing an ENTIRE existing source file and says to call context tools when context is insufficient. In addition, --no-plan inserts the fixed text:

(no pre-scan plan; review the entire file as usual)

This makes it difficult to run a bounded single-function or dependency-isolated scan when the caller needs a different review scope. A caller can provide a narrower background/rule, but the resulting prompt still contains the whole-file and context-tool instructions.

Why this matters

For integrations that expose only a bounded synthetic file and a restricted tool set, the caller cannot express a fully consistent contract without maintaining a private OCR build or rewriting the prompt downstream. Downstream rewriting would also make the integration behavior differ from the native OCR contract.

This issue is about prompt-contract configurability; it is not a claim that this behavior alone explains every model timeout.

Requested behavior

Please consider one of these native options:

1. Add an explicit scan-template override (for example, a validated template file/config) covering the complete MAIN_TASK system/user messages and the no-plan sentinel; or
2. Add a documented bounded-review mode whose system prompt, user wrapper, no-plan behavior, and tool guidance are internally consistent with the selected scope.

The existing default behavior should remain unchanged when no override/mode is supplied. Template validation should fail closed, and the override should not silently change token/tool budgets.

Reproduction

Run a scan with a narrow background/rule and no plan:

ocr scan --path path/to/file.py --no-plan \
  --background 'Review only the selected function; do not inspect other files.' \
  --rule path/to/restricted-rule.json

Inspect the generated request or enable a request capture in a local test endpoint. The request still contains the fixed whole-file review wording and the fixed no-plan sentence in addition to the narrower background/rule.

Evidence

The behavior is visible in:

• internal/config/template/scan_template.json
• internal/config/template/template.go
• internal/scan/agent.go

No source changes are proposed in this issue.

[Qiyuanqiii]

let me see