diff --git a/common/logging_config.py b/common/logging_config.py
index abc639c..95b3f1d 100644
--- a/common/logging_config.py
+++ b/common/logging_config.py
@@ -1,12 +1,64 @@
 import logging
+import sys
+
+import structlog
+
+# Loggers that install their own handlers (uvicorn's dictConfig runs before the
+# app is imported). Their handlers are stripped so records propagate to the
+# root handler below and come out as JSON like everything else.
+# uvicorn.access is left alone on purpose: --no-access-log works by setting its
+# propagate=False, and re-enabling propagation would turn access logs back on.
+_FOREIGN_LOGGERS = ("uvicorn", "uvicorn.error")
 
 
-def configure_logging(service_name: str) -> logging.Logger:
-    """Plain-text, human-prose logging -- the deliberately weak Phase 0
-    baseline. Per phase-0-base-project-spec.md §9: no JSON, no key-value, no
-    structured fields. Do not "improve" this; later phases replace it."""
-    logging.basicConfig(
-        level=logging.INFO,
-        format="%(asctime)s %(levelname)s %(name)s %(message)s",
+def _add_service(service_name: str):
+    def processor(logger, method_name, event_dict):
+        event_dict["service"] = service_name
+        return event_dict
+
+    return processor
+
+
+def configure_logging(service_name: str) -> structlog.stdlib.BoundLogger:
+    """One JSON object per line on stdout, for structlog and stdlib loggers alike.
+
+    `shared` runs for every record, whichever API emitted it: structlog calls
+    pass through it via structlog.configure(), stdlib records (uvicorn, the
+    consumers' logging.getLogger(...)) via the formatter's foreign_pre_chain.
+    """
+    shared = [
+        structlog.contextvars.merge_contextvars,
+        structlog.stdlib.add_log_level,
+        structlog.stdlib.add_logger_name,
+        structlog.processors.TimeStamper(fmt="iso", utc=True),
+        _add_service(service_name),
+    ]
+
+    structlog.configure(
+        processors=[*shared, structlog.stdlib.ProcessorFormatter.wrap_for_formatter],
+        logger_factory=structlog.stdlib.LoggerFactory(),
+        wrapper_class=structlog.stdlib.BoundLogger,
+        cache_logger_on_first_use=True,
     )
-    return logging.getLogger(service_name)
+
+    formatter = structlog.stdlib.ProcessorFormatter(
+        foreign_pre_chain=shared,
+        processors=[
+            structlog.stdlib.ProcessorFormatter.remove_processors_meta,
+            structlog.processors.format_exc_info,
+            structlog.processors.JSONRenderer(),
+        ],
+    )
+    handler = logging.StreamHandler(sys.stdout)
+    handler.setFormatter(formatter)
+
+    root = logging.getLogger()
+    root.handlers = [handler]
+    root.setLevel(logging.INFO)
+
+    for name in _FOREIGN_LOGGERS:
+        foreign = logging.getLogger(name)
+        foreign.handlers = []
+        foreign.propagate = True
+
+    return structlog.get_logger(service_name)
diff --git a/requirements.txt b/requirements.txt
index 9856341..55bdaff 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -8,5 +8,6 @@ redis==5.2.1
 pydantic==2.10.4
 pydantic-settings==2.7.1
 python-multipart==0.0.20
+structlog==25.5.0
 opentelemetry-distro==0.66b1
 opentelemetry-exporter-otlp==1.45.1