diff --git a/containers/api-proxy/Dockerfile b/containers/api-proxy/Dockerfile
index 53a3fbba..52144684 100644
--- a/containers/api-proxy/Dockerfile
+++ b/containers/api-proxy/Dockerfile
@@ -31,7 +31,7 @@ COPY server.js logging.js metrics.js rate-limiter.js rate-limiter-window.js \
      upstream-log.js upstream-retry.js upstream-token.js \
      anthropic-cache.js otel.js otel-exporters.js otel-serialization.js \
      token-budget-log.js blocked-request-diagnostics.js \
-     provider-env-constants.js provider-names.js \
+     provider-env-constants.js provider-env-constants.json provider-names.js \
      model-api-mapping.js model-api-mapping.json ./
 COPY guards/ ./guards/
 COPY providers/ ./providers/
diff --git a/containers/api-proxy/provider-env-constants.js b/containers/api-proxy/provider-env-constants.js
index d22430e8..25632b3b 100644
--- a/containers/api-proxy/provider-env-constants.js
+++ b/containers/api-proxy/provider-env-constants.js
@@ -3,46 +3,7 @@
 /**
  * Environment variable name constants for the API proxy provider adapters.
  *
- * The TypeScript equivalent lives in src/api-proxy-env-constants.ts.
- * Keep both files in sync; src/api-proxy-env-constants-sync.test.ts enforces parity.
+ * Single source of truth: provider-env-constants.json
+ * The TypeScript host re-exports from the same JSON via src/api-proxy-env-constants.ts.
  */
-
-/** Environment variable names for the OpenAI provider adapter. */
-const OPENAI_ENV = /** @type {const} */ ({
-  KEY: 'OPENAI_API_KEY',
-  TARGET: 'OPENAI_API_TARGET',
-  BASE_PATH: 'OPENAI_API_BASE_PATH',
-  AUTH_HEADER: 'AWF_OPENAI_AUTH_HEADER',
-});
-
-/** Environment variable names for the Anthropic provider adapter. */
-const ANTHROPIC_ENV = /** @type {const} */ ({
-  KEY: 'ANTHROPIC_API_KEY',
-  TARGET: 'ANTHROPIC_API_TARGET',
-  BASE_PATH: 'ANTHROPIC_API_BASE_PATH',
-  AUTH_HEADER: 'AWF_ANTHROPIC_AUTH_HEADER',
-});
-
-/** Environment variable names for the Gemini provider adapter. */
-const GEMINI_ENV = /** @type {const} */ ({
-  KEY: 'GEMINI_API_KEY',
-  TARGET: 'GEMINI_API_TARGET',
-  BASE_PATH: 'GEMINI_API_BASE_PATH',
-});
-
-/** Environment variable names for the Copilot provider adapter. */
-const COPILOT_ENV = /** @type {const} */ ({
-  GITHUB_TOKEN: 'COPILOT_GITHUB_TOKEN',
-  PROVIDER_API_KEY: 'COPILOT_PROVIDER_API_KEY',
-  PROVIDER_TYPE: 'COPILOT_PROVIDER_TYPE',
-  PROVIDER_BASE_URL: 'COPILOT_PROVIDER_BASE_URL',
-  API_TARGET: 'COPILOT_API_TARGET',
-  API_BASE_PATH: 'COPILOT_API_BASE_PATH',
-});
-
-module.exports = {
-  OPENAI_ENV,
-  ANTHROPIC_ENV,
-  GEMINI_ENV,
-  COPILOT_ENV,
-};
+module.exports = require('./provider-env-constants.json');
diff --git a/containers/api-proxy/provider-env-constants.json b/containers/api-proxy/provider-env-constants.json
new file mode 100644
index 00000000..6fe19860
--- /dev/null
+++ b/containers/api-proxy/provider-env-constants.json
@@ -0,0 +1,27 @@
+{
+  "OPENAI_ENV": {
+    "KEY": "OPENAI_API_KEY",
+    "TARGET": "OPENAI_API_TARGET",
+    "BASE_PATH": "OPENAI_API_BASE_PATH",
+    "AUTH_HEADER": "AWF_OPENAI_AUTH_HEADER"
+  },
+  "ANTHROPIC_ENV": {
+    "KEY": "ANTHROPIC_API_KEY",
+    "TARGET": "ANTHROPIC_API_TARGET",
+    "BASE_PATH": "ANTHROPIC_API_BASE_PATH",
+    "AUTH_HEADER": "AWF_ANTHROPIC_AUTH_HEADER"
+  },
+  "GEMINI_ENV": {
+    "KEY": "GEMINI_API_KEY",
+    "TARGET": "GEMINI_API_TARGET",
+    "BASE_PATH": "GEMINI_API_BASE_PATH"
+  },
+  "COPILOT_ENV": {
+    "GITHUB_TOKEN": "COPILOT_GITHUB_TOKEN",
+    "PROVIDER_API_KEY": "COPILOT_PROVIDER_API_KEY",
+    "PROVIDER_TYPE": "COPILOT_PROVIDER_TYPE",
+    "PROVIDER_BASE_URL": "COPILOT_PROVIDER_BASE_URL",
+    "API_TARGET": "COPILOT_API_TARGET",
+    "API_BASE_PATH": "COPILOT_API_BASE_PATH"
+  }
+}
diff --git a/src/api-proxy-env-constants-sync.test.ts b/src/api-proxy-env-constants-sync.test.ts
index 2d41906a..d8318df8 100644
--- a/src/api-proxy-env-constants-sync.test.ts
+++ b/src/api-proxy-env-constants-sync.test.ts
@@ -9,7 +9,7 @@ const providerEnvConstants = require('../containers/api-proxy/provider-env-const
 };
 
 describe('API proxy provider env constants', () => {
-  it('stays in sync between TypeScript host code and JS sidecar code', () => {
+  it('TypeScript host and JS sidecar both load from the same JSON source', () => {
     expect(providerEnvConstants.OPENAI_ENV).toEqual(OPENAI_ENV);
     expect(providerEnvConstants.ANTHROPIC_ENV).toEqual(ANTHROPIC_ENV);
     expect(providerEnvConstants.GEMINI_ENV).toEqual(GEMINI_ENV);
diff --git a/src/api-proxy-env-constants.ts b/src/api-proxy-env-constants.ts
index e9c3fb72..8932daf3 100644
--- a/src/api-proxy-env-constants.ts
+++ b/src/api-proxy-env-constants.ts
@@ -1,42 +1,19 @@
 /**
  * Environment variable name constants for the API proxy provider adapters.
  *
- * The CommonJS equivalent lives in containers/api-proxy/provider-env-constants.js.
- * Keep both files in sync; src/api-proxy-env-constants-sync.test.ts enforces parity.
+ * Single source of truth: containers/api-proxy/provider-env-constants.json
+ * The CommonJS sidecar loads the same JSON via containers/api-proxy/provider-env-constants.js.
  */
+import providerEnvConstants from '../containers/api-proxy/provider-env-constants.json';
 
 /** Environment variable names for the OpenAI provider adapter. */
-export const OPENAI_ENV = {
-  KEY: 'OPENAI_API_KEY',
-  TARGET: 'OPENAI_API_TARGET',
-  BASE_PATH: 'OPENAI_API_BASE_PATH',
-  AUTH_HEADER: 'AWF_OPENAI_AUTH_HEADER',
-} as const;
-
+export const OPENAI_ENV = providerEnvConstants.OPENAI_ENV;
 /** Environment variable names for the Anthropic provider adapter. */
-export const ANTHROPIC_ENV = {
-  KEY: 'ANTHROPIC_API_KEY',
-  TARGET: 'ANTHROPIC_API_TARGET',
-  BASE_PATH: 'ANTHROPIC_API_BASE_PATH',
-  AUTH_HEADER: 'AWF_ANTHROPIC_AUTH_HEADER',
-} as const;
-
+export const ANTHROPIC_ENV = providerEnvConstants.ANTHROPIC_ENV;
 /** Environment variable names for the Gemini provider adapter. */
-export const GEMINI_ENV = {
-  KEY: 'GEMINI_API_KEY',
-  TARGET: 'GEMINI_API_TARGET',
-  BASE_PATH: 'GEMINI_API_BASE_PATH',
-} as const;
-
+export const GEMINI_ENV = providerEnvConstants.GEMINI_ENV;
 /** Environment variable names for the Copilot provider adapter. */
-export const COPILOT_ENV = {
-  GITHUB_TOKEN: 'COPILOT_GITHUB_TOKEN',
-  PROVIDER_API_KEY: 'COPILOT_PROVIDER_API_KEY',
-  PROVIDER_TYPE: 'COPILOT_PROVIDER_TYPE',
-  PROVIDER_BASE_URL: 'COPILOT_PROVIDER_BASE_URL',
-  API_TARGET: 'COPILOT_API_TARGET',
-  API_BASE_PATH: 'COPILOT_API_BASE_PATH',
-} as const;
+export const COPILOT_ENV = providerEnvConstants.COPILOT_ENV;
 
 /**
  * OIDC authentication env var mappings.