new-lib

name	new-lib
description	Use when adding a new library under lib/. Creates the full scaffold with Kconfig, CMakeLists.txt, header, source, and wires it into the build system. Invoke when the user says "add library", "new lib", "create library", or similar.
argument-hint	<lib_name> "<description>" <kconfig_symbol> <sys_init_priority>
allowed-tools	Read, Write, Edit, Bash, Glob, Grep

Add a New Consumer or Utility Library

Use this when adding a new library under lib/ — e.g. an MQTT publisher, telemetry codec, data logger, or any other consumer/utility that subscribes to zbus channels.

Arguments received: lib_name=$0 · description=$1 · kconfig_symbol=$2 · sys_init_priority=$3

Use the scaffold script

Instead of creating files manually, use the scaffold script:

scripts/scaffold-lib.sh <lib_name> "<description>" <kconfig_symbol> <sys_init_priority>

Options:

• --dry-run — Show what would be created without writing files
• --skip-build — Skip the build verification step
• --quiet — Suppress stderr progress output

Example:

scripts/scaffold-lib.sh mqtt_publisher "MQTT telemetry publisher" MQTT_PUBLISHER 95
scripts/scaffold-lib.sh mqtt_publisher "MQTT telemetry publisher" MQTT_PUBLISHER 95 --dry-run

Output: JSON to stdout with created files list, build status, and overall verdict. Human-readable progress goes to stderr.

JSON output schema:

{
  "script": "scaffold-lib",
  "timestamp": "2026-05-25T12:00:00Z",
  "verdict": "PASS|FAIL|DRY_RUN",
  "lib_name": "mqtt_publisher",
  "kconfig_symbol": "CONFIG_MQTT_PUBLISHER",
  "sys_init_priority": 95,
  "files_created": [
    "lib/mqtt_publisher/Kconfig",
    "lib/mqtt_publisher/CMakeLists.txt",
    "lib/mqtt_publisher/include/mqtt_publisher/mqtt_publisher.h",
    "lib/mqtt_publisher/src/mqtt_publisher.c",
    "lib/Kconfig (modified)",
    "CMakeLists.txt (modified)",
    "apps/gateway/prj.conf (modified)"
  ],
  "build_status": "PASS|FAIL|SKIPPED|N/A",
  "build_output": "...",
  "summary": "Created 7 files for lib/mqtt_publisher."
}

Exit codes: 0 = success, 1 = error (missing args, file exists, build failed)

Manual steps (for reference)

The script performs these steps:

1. Branch — git checkout master && git pull && git checkout -b feat/<lib_name>
2. Decide zbus channel ownership — Does this library define a new channel? If yes, ZBUS_CHAN_DEFINE in exactly one .c. If no, subscribe via ZBUS_CHAN_DECLARE + zbus_chan_add_obs().
3. Choose SYS_INIT priority — Consumers of sensor_event_chan must initialise after their producers (≥92). Publishers to sensor_trigger_chan stay below 90.
4. Create directory structure — lib/<lib_name>/{CMakeLists.txt, Kconfig, include/<lib_name>/<lib_name>.h, src/<lib_name>.c}
5. Write files — See reference templates in references/
6. Register in build system — Add to lib/Kconfig and root CMakeLists.txt
7. Enable in app configs — CONFIG_<KCONFIG_SYMBOL>=y in apps/gateway/prj.conf
8. Verify the build — Pristine rebuild required (Kconfig changed)

Architecture rules

• Architecture rule: ZBUS_CHAN_DEFINE in exactly one .c per channel. Never define a channel that is already defined elsewhere.
• Do not add target_link_libraries() in any app CMakeLists.txt — use Kconfig only
• Do not create a sensor_manager — sensors are trigger-driven, not polled
• Do not put application logic in main.c — main.c should contain only LOG_MODULE_REGISTER + optional SYS_INIT + k_sleep(K_FOREVER)
• Do not hardcode sensor_uid values in consumers — look them up via sensor_registry

Red Flags — STOP and re-check

Feeling	Reality
"I can use target_link_libraries() in the app"	Never. ADR-008: Kconfig-only composition.
"This channel is already defined somewhere else"	Don't define it again. ZBUS_CHAN_DEFINE in exactly one .c.
"I need a sensor_manager to poll sensors"	ADR-004: trigger-driven, not polled. Subscribe to channels.
"I'll put logic in main.c"	ADR-008: main.c = LOG_MODULE_REGISTER + return 0 only.
"I'll hardcode sensor_uid in the consumer"	ADR-006: sensor_uid is the identity key. Use sensor_registry.

Next steps

After completing this skill:

• Invoke /build-and-test to run the full verification gate
• If the library introduces a new pattern or channel → invoke /adr to document the decision