diff --git a/src/mcp/types.ts b/src/mcp/types.ts
index 29efc18..600c832 100644
--- a/src/mcp/types.ts
+++ b/src/mcp/types.ts
@@ -51,6 +51,8 @@ export interface ModelConfig {
   baseURL: string;
   model: string;
   apiKey: string;
+  /** Optional provider-specific header used to correlate one logical call across retries. */
+  callIdHeader?: string;
   secretRef?: string;
   temperature?: number;
   topP?: number;
diff --git a/src/provider/runtime.ts b/src/provider/runtime.ts
index 536f59e..4db7586 100644
--- a/src/provider/runtime.ts
+++ b/src/provider/runtime.ts
@@ -1,4 +1,5 @@
 import OpenAI from 'openai';
+import { randomUUID } from 'node:crypto';
 import type { RequestOptions } from 'openai/core';
 import type {
   ChatCompletion,
@@ -92,6 +93,25 @@ function nonNegativeInt(value: unknown, fallback: number): number {
     : fallback;
 }
 
+function resolveCallIdHeader(value: unknown): string | null {
+  if (value === undefined) return null;
+  if (typeof value !== 'string' || !/^[!#$%&'*+.^_`|~0-9A-Za-z-]{1,128}$/.test(value)) {
+    throw new Error('provider call id header is invalid');
+  }
+  return value.toLowerCase();
+}
+
+function callRequestOptions(
+  signal: AbortSignal | undefined,
+  header: string | null,
+  callId: string | null
+): RequestOptions {
+  return {
+    signal,
+    ...(header && callId ? { headers: { [header]: callId } } : {}),
+  } as RequestOptions;
+}
+
 export function resolveProviderPolicy(model: ModelConfig): ProviderPolicy {
   const requestTimeoutMs = positiveInt(
     model.requestTimeoutMs,
@@ -155,6 +175,10 @@ function isRetryableProviderError(err: unknown): boolean {
   if (err instanceof ProviderRequestTimeoutError) return true;
   if (isAbortLike(err)) return false;
 
+  const explicitRetryable = (err as any)?.error?.retryable ?? (err as any)?.retryable;
+  if (explicitRetryable === false) return false;
+  if (explicitRetryable === true) return true;
+
   const status = (err as any)?.status;
   if (
     status === 408 ||
@@ -294,6 +318,7 @@ export function createProviderRuntime(
   }
   const client = overrideClient ?? createProviderClient(model, policy);
   const maxAttempts = policy.maxRetries + 1;
+  const callIdHeader = resolveCallIdHeader(model.callIdHeader);
 
   async function runWithRetry<T>(
     stream: boolean,
@@ -348,13 +373,14 @@ export function createProviderRuntime(
     client,
     policy,
     createChatCompletion(request, options) {
+      const callId = callIdHeader ? `ma_call_${randomUUID()}` : null;
       return runWithRetry(
         false,
         () =>
           raceWithTimeout(
             client.chat.completions.create(
               { ...request, stream: false },
-              { signal: options?.signal } as RequestOptions
+              callRequestOptions(options?.signal, callIdHeader, callId)
             ) as unknown as Promise<ChatCompletion>,
             policy.requestTimeoutMs,
             options?.signal
@@ -363,14 +389,15 @@ export function createProviderRuntime(
       );
     },
     createStreamingChatCompletion(request, options) {
+      const callId = callIdHeader ? `ma_call_${randomUUID()}` : null;
       return runWithRetry(
         true,
         async () => {
           const start = await openStreamAndReadFirstChunk(
             () =>
               client.chat.completions.create(
-              { ...request, stream: true },
-              { signal: options?.signal } as RequestOptions
+                { ...request, stream: true },
+                callRequestOptions(options?.signal, callIdHeader, callId)
               ) as unknown as Promise<AsyncIterable<ChatCompletionChunk>>,
             policy,
             options?.signal
diff --git a/test/provider-runtime.test.ts b/test/provider-runtime.test.ts
index e197846..552ea60 100644
--- a/test/provider-runtime.test.ts
+++ b/test/provider-runtime.test.ts
@@ -127,8 +127,89 @@ test('provider runtime: request timeout is retried', async () => {
   assert.ok(events.some((event) => event.type === 'retry'));
 });
 
+test('provider runtime: reuses one logical call id across retries and rotates it for the next call', async () => {
+  const requestOptions: any[] = [];
+  let attempts = 0;
+  const runtime = createProviderRuntime(
+    {
+      baseURL: 'http://example.test/v1',
+      model: 'stub',
+      apiKey: 'key',
+      callIdHeader: 'X-MTEAM-MA-Call-ID',
+      requestTimeoutMs: 50,
+      maxRetries: 1,
+    },
+    fakeClient((_request, options) => {
+      requestOptions.push(options);
+      attempts++;
+      if (attempts === 1) {
+        const error = new Error('temporary failure') as Error & { status: number };
+        error.status = 503;
+        return Promise.reject(error);
+      }
+      return Promise.resolve({ choices: [{ message: { content: 'ok' } }] });
+    })
+  );
+
+  await runtime.createChatCompletion({ model: 'stub', messages: [], stream: false });
+  await runtime.createChatCompletion({ model: 'stub', messages: [], stream: false });
+
+  const ids = requestOptions.map((options) => options.headers['x-mteam-ma-call-id']);
+  assert.match(ids[0], /^ma_call_[0-9a-f-]{36}$/);
+  assert.equal(ids[1], ids[0]);
+  assert.notEqual(ids[2], ids[0]);
+});
+
+test('provider runtime: does not emit a call id header without an explicit provider opt-in', async () => {
+  let captured: any;
+  const runtime = createProviderRuntime(
+    {
+      baseURL: 'http://example.test/v1',
+      model: 'stub',
+      apiKey: 'key',
+      maxRetries: 0,
+    },
+    fakeClient((_request, options) => {
+      captured = options;
+      return Promise.resolve({ choices: [] });
+    })
+  );
+
+  await runtime.createChatCompletion({ model: 'stub', messages: [], stream: false });
+  assert.equal(captured.headers, undefined);
+});
+
+test('provider runtime: honors an explicit non-retryable provider error', async () => {
+  let calls = 0;
+  const runtime = createProviderRuntime(
+    {
+      baseURL: 'http://example.test/v1',
+      model: 'stub',
+      apiKey: 'key',
+      maxRetries: 3,
+    },
+    fakeClient(() => {
+      calls++;
+      const error = new Error('authority unavailable') as Error & {
+        status: number;
+        error: { retryable: boolean };
+      };
+      error.status = 503;
+      error.error = { retryable: false };
+      return Promise.reject(error);
+    })
+  );
+
+  await assert.rejects(
+    () => runtime.createChatCompletion({ model: 'stub', messages: [], stream: false }),
+    /authority unavailable/
+  );
+  assert.equal(calls, 1);
+});
+
 test('provider runtime: stream idle before first chunk is retried', async () => {
   let calls = 0;
+  const requestOptions: any[] = [];
   const runtime = createProviderRuntime(
     {
       baseURL: 'http://example.test/v1',
@@ -137,8 +218,10 @@ test('provider runtime: stream idle before first chunk is retried', async () =>
       requestTimeoutMs: 20,
       streamIdleTimeoutMs: 5,
       maxRetries: 1,
+      callIdHeader: 'x-mteam-ma-call-id',
     },
-    fakeClient(() => {
+    fakeClient((_request, options) => {
+      requestOptions.push(options);
       calls++;
       if (calls === 1) return Promise.resolve(stallBeforeFirst());
       return Promise.resolve(chunks([
@@ -157,6 +240,10 @@ test('provider runtime: stream idle before first chunk is retried', async () =>
   assert.equal(calls, 2);
   assert.equal(out.length, 1);
   assert.equal(out[0].choices[0].delta.content, 'ok');
+  assert.equal(
+    requestOptions[0].headers['x-mteam-ma-call-id'],
+    requestOptions[1].headers['x-mteam-ma-call-id'],
+  );
   assert.ok(events.some((event) => event.type === 'retry'));
 });