---
id: TASK-18.2
title: 'Document ${key} interpolation in user docs with examples'
status: Done
assignee:
  - codex
created_date: '2026-02-19 17:45'
updated_date: '2026-02-19 17:50'
labels: []
dependencies: []
references:
  - README.md
  - docs/
parent_task_id: TASK-18
---

## Description

<!-- SECTION:DESCRIPTION:BEGIN -->
Update user-facing docs (README or docs) to describe how to use ${key} placeholders in zconf.lua, including examples for global and profile args.
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## Acceptance Criteria
<!-- AC:BEGIN -->
- [x] #1 Add a dedicated doc section explaining ${key} interpolation and when it is applied.
- [x] #2 Provide example zconf.lua snippets for global config and profile-scoped args using ${board}, ${build_dir}, ${project_dir}, ${zephyr_ws}, ${zephyr_base}.
- [x] #3 Mention how CLI overrides and profiles affect interpolation scope.
<!-- AC:END -->

## Implementation Notes

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Added a README.md section on ${key} interpolation with global and profile-scoped examples and notes about interpolation timing and CLI/profile overrides.

Reopened to add missing documentation of supported ${key} interpolation variables in README.

Added supported interpolation keys list to README.md (board, runner, profile, build_dir, project_dir, zephyr_ws, zephyr_base, cwd, is_build, sysbuild).
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## Final Summary

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Summary:
- Documented ${key} interpolation support in README, including an explicit list of supported keys alongside existing examples and behavior notes.

Tests:
- Not run (documentation-only changes)

Notes:
- No Definition of Done items were defined for this task.
<!-- SECTION:FINAL_SUMMARY:END -->
