diff --git a/.github/workflows/sdk-spec.yml b/.github/workflows/sdk-spec.yml
new file mode 100644
index 0000000..6952fea
--- /dev/null
+++ b/.github/workflows/sdk-spec.yml
@@ -0,0 +1,17 @@
+name: SDK spec
+
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+permissions:
+  contents: read
+
+jobs:
+  sdk-spec:
+    # Keep the ref in `uses:` and `spec-ref` in sync.
+    uses: Flagsmith/sdk-spec/.github/workflows/run-spec.yml@v0.3.0
+    with:
+      spec-ref: v0.3.0
+      language: python
diff --git a/renovate.json b/renovate.json
index 8bdf036..0ccc024 100644
--- a/renovate.json
+++ b/renovate.json
@@ -3,6 +3,15 @@
     "extends": ["config:recommended", ":semanticCommitScopeDisabled"],
     "ignorePresets": [":semanticPrefixFixDepsChoreOthers"],
     "semanticCommitType": "deps",
+    "customManagers": [
+        {
+            "customType": "regex",
+            "managerFilePatterns": ["/^\\.github/workflows/sdk-spec\\.yml$/"],
+            "matchStrings": ["spec-ref: (?<currentValue>v[\\d.]+)"],
+            "depNameTemplate": "Flagsmith/sdk-spec",
+            "datasourceTemplate": "github-tags"
+        }
+    ],
     "packageRules": [
         {
             "matchManagers": ["pip_requirements", "pip-compile", "pep621", "poetry", "github-actions"],
@@ -22,6 +31,11 @@
         {
             "matchPackageNames": ["flagsmith-flag-engine"],
             "enabled": true
+        },
+        {
+            "matchPackageNames": ["Flagsmith/sdk-spec"],
+            "groupName": "SDK spec",
+            "enabled": true
         }
     ]
 }
diff --git a/sdk-spec/Dockerfile b/sdk-spec/Dockerfile
new file mode 100644
index 0000000..d565079
--- /dev/null
+++ b/sdk-spec/Dockerfile
@@ -0,0 +1,13 @@
+# Runs this SDK, built from source, under the Flagsmith SDK behavioural spec.
+# docker build -f sdk-spec/Dockerfile --build-context harness=<sdk-spec>/harness/python .
+FROM python:3.12-slim
+
+WORKDIR /sdk
+COPY pyproject.toml poetry.lock README.md ./
+COPY flagsmith ./flagsmith
+RUN pip install --no-cache-dir .
+
+COPY --from=harness harness.py /harness/harness.py
+COPY sdk-spec/steps.py ./sdk-spec/steps.py
+
+ENTRYPOINT ["python", "/harness/harness.py", "sdk-spec/steps.py"]
diff --git a/sdk-spec/steps.py b/sdk-spec/steps.py
new file mode 100644
index 0000000..5cd373d
--- /dev/null
+++ b/sdk-spec/steps.py
@@ -0,0 +1,37 @@
+"""
+Steps for the Flagsmith SDK behavioural spec: https://github.com/Flagsmith/sdk-spec
+
+Each function implements the Gherkin step in the comment above it.
+"""
+
+import typing
+
+from flagsmith import Flagsmith
+from flagsmith.models import Flags
+from flagsmith.types import TraitMapping
+
+SpecFlag = dict[str, typing.Any]
+
+
+def as_spec_flags(flags: Flags) -> list[SpecFlag]:
+    return [
+        {"feature": flag.feature_name, "enabled": flag.enabled, "value": flag.value}
+        for flag in flags.all_flags()
+    ]
+
+
+# Create the SDK client
+def create_client(environment_key: str, api_url: str) -> Flagsmith:
+    return Flagsmith(environment_key=environment_key, api_url=api_url)
+
+
+# When the application gets the environment flags
+def get_environment_flags(flagsmith: Flagsmith) -> list[SpecFlag]:
+    return as_spec_flags(flagsmith.get_environment_flags())
+
+
+# When the application gets the flags for identity "{identifier}" with traits:
+def get_identity_flags(
+    flagsmith: Flagsmith, identifier: str, traits: TraitMapping
+) -> list[SpecFlag]:
+    return as_spec_flags(flagsmith.get_identity_flags(identifier, traits=traits))