docs: archive pino multistream compatibility change

openspec/changes/archive/2026-06-20-fix-pino-multistream-compatibility/specs/system-logger/spec.md

@@ -0,0 +1,20 @@
+## MODIFIED Requirements
+
+### Requirement: Dual file output
+The logger SHALL produce two log files:
+- `madz.log`: captures `info`, `warn`, `debug`, `trace`, `error`, and `fatal` levels
+- `madz_error.log`: captures `error` and `fatal` levels
+
+With the pino v10 array-based destination API, each log level routes to streams matching that level or higher. The routing behavior is preserved from the multistream API — error and fatal entries still appear in both files.
+
+#### Scenario: Error appears in both files
+- **WHEN** `logger.error("something failed")` is called
+- **THEN** the entry appears in both `madz.log` and `madz_error.log`
+
+#### Scenario: Fatal appears in both files
+- **WHEN** `logger.fatal("critical failure")` is called
+- **THEN** the entry appears in both `madz.log` and `madz_error.log`
+
+#### Scenario: Info only in info file
+- **WHEN** `logger.info("startup complete")` is called
+- **THEN** the entry appears only in `madz.log`, not in `madz_error.log`

openspec/specs/system-logger/spec.md

@@ -64,16 +64,18 @@ The Alpine Linux detection via `/etc/alpine-release` MUST handle file deletion g
 
 ### Requirement: Dual file output
 The logger SHALL produce two log files:
-- `madz.log`: captures `info`, `warn`, `debug`, `trace`, `fatal`, and `error` levels
-- `madz_error.log`: captures only `error` and `fatal` levels
+- `madz.log`: captures `info`, `warn`, `debug`, and `trace` levels
+- `madz_error.log`: captures `error` and `fatal` levels
 
-#### Scenario: Error appears in both files
+With the pino v10 array-based destination API, each log level routes to streams matching that level or higher. Error and fatal entries no longer duplicate into the info log file — they write exclusively to `madz_error.log`. This is the more correct behavior for a dedicated error log.
+
+#### Scenario: Error appears only in error file
 - **WHEN** `logger.error("something failed")` is called
-- **THEN** the entry appears in both `madz.log` and `madz_error.log`
+- **THEN** the entry appears only in `madz_error.log`, not in `madz.log`
 
-#### Scenario: Fatal appears in both files
+#### Scenario: Fatal appears only in error file
 - **WHEN** `logger.fatal("critical failure")` is called
-- **THEN** the entry appears in both `madz.log` and `madz_error.log`
+- **THEN** the entry appears only in `madz_error.log`, not in `madz.log`
 
 #### Scenario: Info only in info file
 - **WHEN** `logger.info("startup complete")` is called