diff --git a/.env.splunk-poc.example b/.env.splunk-poc.example
new file mode 100644
index 0000000..66fb18a
--- /dev/null
+++ b/.env.splunk-poc.example
@@ -0,0 +1,18 @@
+# Splunk Distribution POC credentials. Copy to .env.splunk-poc (gitignored).
+# Locations in Splunk Observability Cloud:
+#   SPLUNK_ACCESS_TOKEN: Organization > Access Tokens (ingest scope)
+#   SPLUNK_REALM:        visible in the Splunk Observability Cloud URL
+#   SPLUNK_HEC_TOKEN:    Data Management > Connect Data > HTTP Event Collector
+#                        (may not be available on all tiers; see POC README caveat)
+
+SPLUNK_ACCESS_TOKEN=
+SPLUNK_REALM=us1
+SPLUNK_HEC_TOKEN=
+
+# Redirect otel-demo apps through the Splunk collector.
+OTEL_COLLECTOR_HOST=splunk-otel-collector
+
+# Activate the otel-demo overlay via the base compose's include directive.
+INCLUDE_COMPOSE_OTEL_DEMO=docker-compose.otel-demo.yml
+
+SPLUNK_COLLECTOR_VERSION=latest
diff --git a/.gitignore b/.gitignore
index 7630b3b..2ab7482 100644
--- a/.gitignore
+++ b/.gitignore
@@ -30,3 +30,7 @@ charts/*/charts/*.tgz
 
 # Terraform plan files
 *.plan
+
+# Splunk distribution POC
+.env.splunk-poc
+docker-compose/splunk-otel-collector/*.local.*
diff --git a/docker-compose.splunk-demo.yml b/docker-compose.splunk-demo.yml
new file mode 100644
index 0000000..582b6e9
--- /dev/null
+++ b/docker-compose.splunk-demo.yml
@@ -0,0 +1,40 @@
+# Splunk OTel distribution overlay for the side-by-side POC.
+# See docker-compose/splunk-otel-collector/README.md to run.
+
+services:
+  splunk-otel-collector:
+    image: quay.io/signalfx/splunk-otel-collector:${SPLUNK_COLLECTOR_VERSION:-latest}
+    container_name: splunk-otel-collector
+    pull_policy: always
+    command: ["--config=/etc/otelcol-config.yml"]
+    volumes:
+      - ./docker-compose/splunk-otel-collector/config.yaml:/etc/otelcol-config.yml
+    ports:
+      # Non-default host ports to avoid collision with the base collector's 4317/4318.
+      - "14317:4317"
+      - "14318:4318"
+      - "13133:13133"
+    networks:
+      - observability-stack-network
+    restart: unless-stopped
+    environment:
+      - SPLUNK_ACCESS_TOKEN
+      - SPLUNK_REALM
+      - SPLUNK_API_URL=https://api.${SPLUNK_REALM}.observability.splunkcloud.com
+      - SPLUNK_INGEST_URL=https://ingest.${SPLUNK_REALM}.observability.splunkcloud.com
+      - SPLUNK_HEC_TOKEN
+      - SPLUNK_HEC_URL=https://ingest.${SPLUNK_REALM}.observability.splunkcloud.com/v1/log
+      - SPLUNK_LISTEN_INTERFACE=0.0.0.0
+      - SPLUNK_MEMORY_TOTAL_MIB=512
+    deploy:
+      resources:
+        limits:
+          memory: 768M
+    depends_on:
+      otel-collector:
+        condition: service_started
+    healthcheck:
+      test: ["CMD", "wget", "-qO-", "http://localhost:13133"]
+      interval: 10s
+      timeout: 5s
+      retries: 5
diff --git a/docker-compose/splunk-otel-collector/README.md b/docker-compose/splunk-otel-collector/README.md
new file mode 100644
index 0000000..d3d8a04
--- /dev/null
+++ b/docker-compose/splunk-otel-collector/README.md
@@ -0,0 +1,69 @@
+# Splunk OTel Distribution POC
+
+Local POC. Inserts Splunk's [OpenTelemetry Collector distribution](https://github.com/signalfx/splunk-otel-collector) between the otel-demo apps and the base `otel-collector`. Demo telemetry fans out to Splunk Observability Cloud and OpenSearch at the same time.
+
+Branch: `feat/splunk-distribution-poc`. Not intended for upstream.
+
+## Dataflow
+
+```
+otel-demo apps
+     │ OTLP (OTEL_COLLECTOR_HOST=splunk-otel-collector)
+     ▼
+splunk-otel-collector
+     ├── signalfx exporter         → Splunk Infrastructure Monitoring
+     ├── otlphttp/splunk-apm       → Splunk APM (ingest/v2/trace/otlp)
+     ├── splunk_hec                → Splunk Log Observer (see caveats)
+     └── otlp/tee                  → base otel-collector (unchanged OpenSearch path)
+```
+
+## Run
+
+```bash
+cp .env.splunk-poc.example .env.splunk-poc
+# fill in SPLUNK_ACCESS_TOKEN, SPLUNK_REALM, SPLUNK_HEC_TOKEN
+
+# finch compose's --env-file doesn't feed ${VAR} substitution in compose files, only
+# container env. Append the POC vars into .env before `up`, restore after.
+cat .env.splunk-poc >> .env
+finch compose -f docker-compose.yml -f docker-compose.splunk-demo.yml up -d
+git checkout -- .env
+```
+
+Teardown:
+
+```bash
+finch compose -f docker-compose.yml -f docker-compose.splunk-demo.yml down
+```
+
+## Verify
+
+Counters on the Splunk collector (send success numbers; non-zero = data flowing):
+
+```bash
+finch run --rm --network observability-stack-network curlimages/curl:latest \
+  -s http://splunk-otel-collector:8888/metrics \
+  | grep -E '^otelcol_exporter_sent_(spans|metric_points)_total'
+```
+
+Host-exposed endpoints on `splunk-otel-collector`:
+
+- `localhost:13133` - health check (200 = ready)
+- `localhost:14317` - OTLP gRPC
+- `localhost:14318` - OTLP HTTP
+
+In Splunk Observability Cloud: **APM > Services** shows demo services (frontend, cart, checkout, ad, recommendation, …). **Infrastructure > Metrics Explorer** shows host metadata from `splunk-otel-collector` and app metrics from the demo.
+
+OpenSearch side is unaffected: Trace Analytics in OSD renders the same demo services via the tee.
+
+## Caveats from validation
+
+- **Splunk HEC logs return HTTP 404** on `/v1/log` with the access token reused as HEC token. The `splunk_hec` exporter retries indefinitely without blocking other pipelines. Logs still land in OpenSearch via `otlp/tee`. Cause is likely one of: access token lacks log-ingest scope, trial tier without Log Observer, or a distinct HEC token is required.
+- `smartagentreceiver` and `host_metrics` from Splunk's default `agent_config.yaml` are not included. The first is proprietary to Splunk's distribution bundle; the second is meaningless in a container.
+
+## Reference
+
+- [Splunk OTel Collector distribution](https://github.com/signalfx/splunk-otel-collector)
+- [Splunk default `agent_config.yaml`](https://github.com/signalfx/splunk-otel-collector/blob/main/cmd/otelcol/config/collector/agent_config.yaml)
+- [signalfxexporter](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/exporter/signalfxexporter)
+- [splunkhecexporter](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/exporter/splunkhecexporter)
diff --git a/docker-compose/splunk-otel-collector/config.yaml b/docker-compose/splunk-otel-collector/config.yaml
new file mode 100644
index 0000000..543dfba
--- /dev/null
+++ b/docker-compose/splunk-otel-collector/config.yaml
@@ -0,0 +1,98 @@
+# Splunk OpenTelemetry Collector config for the side-by-side POC.
+# See docker-compose/splunk-otel-collector/README.md to run.
+#
+# Based on Splunk's default agent_config.yaml with host-level receivers and
+# smartagent/opamp/http_forwarder extensions removed (not viable in-container).
+#
+# Reference: https://github.com/signalfx/splunk-otel-collector/blob/main/cmd/otelcol/config/collector/agent_config.yaml
+
+extensions:
+  health_check:
+    endpoint: "0.0.0.0:13133"
+
+receivers:
+  # OTLP on the same ports as the base collector so demo apps only need OTEL_COLLECTOR_HOST changed.
+  otlp:
+    protocols:
+      grpc:
+        endpoint: 0.0.0.0:4317
+      http:
+        endpoint: 0.0.0.0:4318
+        cors:
+          allowed_origins:
+            - "http://*"
+            - "https://*"
+
+processors:
+  memory_limiter:
+    check_interval: 5s
+    limit_percentage: 80
+    spike_limit_percentage: 25
+
+  batch:
+    timeout: 10s
+    send_batch_size: 1024
+
+  resourcedetection:
+    detectors: [env, system]
+
+exporters:
+  # Splunk APM: OTLP traces to Splunk's trace ingest endpoint.
+  otlphttp/splunk-apm:
+    traces_endpoint: "${SPLUNK_INGEST_URL}/v2/trace/otlp"
+    headers:
+      "X-SF-Token": "${SPLUNK_ACCESS_TOKEN}"
+
+  # Splunk Infrastructure Monitoring: metrics + events.
+  signalfx:
+    access_token: "${SPLUNK_ACCESS_TOKEN}"
+    api_url: "${SPLUNK_API_URL}"
+    ingest_url: "${SPLUNK_INGEST_URL}"
+    sync_host_metadata: true
+
+  # Splunk Log Observer via HEC. Returns 404 in current POC validation; see README caveats.
+  splunk_hec:
+    token: "${SPLUNK_HEC_TOKEN}"
+    endpoint: "${SPLUNK_HEC_URL}"
+    source: "otel-demo"
+    sourcetype: "otel"
+    profiling_data_enabled: false
+
+  # Forward to observability-stack's base otel-collector for the OpenSearch path.
+  otlp/tee:
+    endpoint: "otel-collector:4317"
+    tls:
+      insecure: true
+
+  debug:
+    verbosity: basic
+
+service:
+  extensions: [health_check]
+
+  pipelines:
+    traces:
+      receivers: [otlp]
+      processors: [memory_limiter, resourcedetection, batch]
+      exporters: [otlphttp/splunk-apm, signalfx, otlp/tee]
+
+    metrics:
+      receivers: [otlp]
+      processors: [memory_limiter, resourcedetection, batch]
+      exporters: [signalfx, otlp/tee]
+
+    logs:
+      receivers: [otlp]
+      processors: [memory_limiter, resourcedetection, batch]
+      exporters: [splunk_hec, otlp/tee]
+
+  telemetry:
+    logs:
+      level: info
+    metrics:
+      readers:
+        - pull:
+            exporter:
+              prometheus:
+                host: 0.0.0.0
+                port: 8888