IntelliJ plugin: `<system-reminder>` reports selected line numbers off by one

Description

When the user selects code in IntelliJ with the Claude Code plugin enabled, the plugin injects a <system-reminder> into the conversation describing the selection. The line-number range in that reminder is consistently one less than the actual line numbers in the file. The quoted content of the selection is correct — the bug is only in the numeric line range.

This is the same shape as #42759 (VS Code, closed stale, not fixed) but observed on the IntelliJ plugin.

Reminder shape

<system-reminder>
The user selected the lines X to Y from /path/to/file.ext:
<quoted content>

This may or may not be related to the current task.
</system-reminder>

X and Y are each actual_line - 1.

Reproductions (today, 2026-06-06)

File: be-platform-ui/src/api/projectApi.ts

Repro 1 — single line

• User selected line 22: export const projectApi: ProjectApi = {
• Reminder said: The user selected the lines 21 to 21 from … projectApi
• File content at line 21 is blank; the quoted symbol projectApi actually lives on line 22. Verified by reading the file.

Repro 2 — multi-line range

• User selected lines 7–9 inclusive (whole lines): the type ProjectApi = { opener, the create: line, and the get: line.
• Reminder said: The user selected the lines 6 to 8 from … followed by exactly those three lines of content.
• Verified the quoted content sits on lines 7–9 in the file, not 6–8.

Pattern: reported numbers are always actual - 1. Content extraction is correct.

Expected behavior

Reported line numbers should be 1-based to match what the user sees in the editor gutter.

Impact

• Misleads Claude when it acts on the location — e.g. calling LSP findReferences / goToDefinition at the reported line/character hits the wrong row.
• Forces a workaround: trust the quoted content over the numeric range, or compensate with +1 before any positional tool call.
• Likely a 0-based vs 1-based mismatch on the plugin side before the payload is injected.

Environment

• Platform: macOS (Darwin 25.3.0)
• IDE: IntelliJ with Claude Code plugin
• Claude model: Opus 4.7 (1M context) — but the bug is upstream of the model

Related

• #42759 — same bug reported for the VS Code extension; closed as stale without a fix. Suggests shared injection code across IDE plugins.