diff --git a/open-sse/executors/default.ts b/open-sse/executors/default.ts
index d7f114570d..905fab1659 100644
--- a/open-sse/executors/default.ts
+++ b/open-sse/executors/default.ts
@@ -419,6 +419,38 @@ export class DefaultExecutor extends BaseExecutor {
       }
     }
 
+    const isCompatibleProvider =
+      this.provider?.startsWith?.("openai-compatible-") ||
+      this.provider?.startsWith?.("anthropic-compatible-");
+
+    if (isCompatibleProvider) {
+      const rawCustomHeaders = credentials.providerSpecificData?.customHeaders;
+      let customHeaders: Record<string, string> | null = null;
+      if (rawCustomHeaders && typeof rawCustomHeaders === "object" && !Array.isArray(rawCustomHeaders)) {
+        customHeaders = rawCustomHeaders as Record<string, string>;
+      } else if (typeof rawCustomHeaders === "string") {
+        try {
+          const parsed = JSON.parse(rawCustomHeaders);
+          if (parsed && typeof parsed === "object" && !Array.isArray(parsed)) {
+            customHeaders = parsed;
+          }
+        } catch { /* ignore invalid JSON */ }
+      }
+      if (customHeaders) {
+        const forbidden = new Set([
+          "host", "connection", "content-length", "keep-alive",
+          "proxy-connection", "transfer-encoding", "te", "trailer", "upgrade",
+        ]);
+        const authHeaders = new Set(["authorization", "x-api-key", "x-goog-api-key", "api-key"]);
+        for (const [k, v] of Object.entries(customHeaders)) {
+          if (typeof k !== "string" || typeof v !== "string") continue;
+          if (forbidden.has(k.toLowerCase())) continue;
+          if (authHeaders.has(k.toLowerCase())) continue;
+          headers[k] = v;
+        }
+      }
+    }
+
     // Forward client request metadata headers (from OpenCode or similar clients)
     // Allowlist-based: only specific x-opencode-* headers and User-Agent are forwarded
     if (clientHeaders) {
diff --git a/src/app/api/provider-nodes/[id]/route.ts b/src/app/api/provider-nodes/[id]/route.ts
index b11daa306e..feba366e20 100644
--- a/src/app/api/provider-nodes/[id]/route.ts
+++ b/src/app/api/provider-nodes/[id]/route.ts
@@ -33,7 +33,7 @@ function sanitizeClaudeCodeCompatibleBaseUrl(baseUrl: string) {
 
 // PUT /api/provider-nodes/[id] - Update provider node
 export async function PUT(request: Request, { params }: { params: Promise<{ id: string }> }) {
-  let rawBody;
+  let rawBody: unknown;
   try {
     rawBody = await request.json();
   } catch {
@@ -54,7 +54,8 @@ export async function PUT(request: Request, { params }: { params: Promise<{ id:
     if (isValidationFailure(validation)) {
       return NextResponse.json({ error: validation.error }, { status: 400 });
     }
-    const { name, prefix, apiType, baseUrl, chatPath, modelsPath } = validation.data;
+    const { name, prefix, apiType, baseUrl, chatPath, modelsPath, customHeaders } =
+      validation.data;
     const node: any = await getProviderNodeById(id);
 
     if (!node) {
@@ -89,6 +90,7 @@ export async function PUT(request: Request, { params }: { params: Promise<{ id:
       baseUrl: sanitizedBaseUrl,
       chatPath: chatPath || null,
       modelsPath: isClaudeCodeCompatibleProvider(id) ? null : modelsPath || null,
+      customHeaders: customHeaders || null,
     };
 
     if (node.type === "openai-compatible") {
@@ -110,6 +112,7 @@ export async function PUT(request: Request, { params }: { params: Promise<{ id:
           baseUrl: sanitizedBaseUrl,
           nodeName: updated.name,
           chatPath: updated.chatPath || undefined,
+          customHeaders: updated.customHeaders || undefined,
         } as JsonRecord;
         if (updated.modelsPath) {
           providerSpecificData.modelsPath = updated.modelsPath;
@@ -136,7 +139,7 @@ export async function PUT(request: Request, { params }: { params: Promise<{ id:
 }
 
 // DELETE /api/provider-nodes/[id] - Delete provider node and its connections
-export async function DELETE(request: Request, { params }: { params: Promise<{ id: string }> }) {
+export async function DELETE(_request: Request, { params }: { params: Promise<{ id: string }> }) {
   try {
     const { id } = await params;
     const node = await getProviderNodeById(id);
diff --git a/src/app/api/provider-nodes/route.ts b/src/app/api/provider-nodes/route.ts
index b58f159d27..9eefbbcebe 100644
--- a/src/app/api/provider-nodes/route.ts
+++ b/src/app/api/provider-nodes/route.ts
@@ -68,7 +68,7 @@ export async function POST(request) {
     if (isValidationFailure(validation)) {
       return NextResponse.json({ error: validation.error }, { status: 400 });
     }
-    const { name, prefix, apiType, baseUrl, type, compatMode, chatPath, modelsPath } =
+    const { name, prefix, apiType, baseUrl, type, compatMode, chatPath, modelsPath, customHeaders } =
       validation.data;
 
     // Determine type
@@ -84,6 +84,7 @@ export async function POST(request) {
         name: name.trim(),
         chatPath: chatPath || null,
         modelsPath: modelsPath || null,
+        customHeaders: customHeaders || null,
       });
       return NextResponse.json({ node }, { status: 201 });
     }
@@ -110,6 +111,7 @@ export async function POST(request) {
         name: name.trim(),
         chatPath: chatPath || null,
         modelsPath: compatMode === "cc" ? null : modelsPath || null,
+        customHeaders: customHeaders || null,
       });
       return NextResponse.json({ node }, { status: 201 });
     }
diff --git a/src/app/api/providers/route.ts b/src/app/api/providers/route.ts
index e732508444..98bbeacc1f 100644
--- a/src/app/api/providers/route.ts
+++ b/src/app/api/providers/route.ts
@@ -126,6 +126,7 @@ export async function POST(request: Request) {
         nodeName: node.name,
         ...(node.chatPath ? { chatPath: node.chatPath } : {}),
         ...(node.modelsPath ? { modelsPath: node.modelsPath } : {}),
+        ...(node.customHeaders ? { customHeaders: node.customHeaders } : {}),
       };
     } else if (isAnthropicCompatibleProvider(provider)) {
       const node: any = await getProviderNodeById(provider);
@@ -150,6 +151,7 @@ export async function POST(request: Request) {
         nodeName: node.name,
         ...(node.chatPath ? { chatPath: node.chatPath } : {}),
         ...(node.modelsPath ? { modelsPath: node.modelsPath } : {}),
+        ...(node.customHeaders ? { customHeaders: node.customHeaders } : {}),
       };
     }
 
diff --git a/src/lib/db/core.ts b/src/lib/db/core.ts
index a365c6ff74..e844614b97 100644
--- a/src/lib/db/core.ts
+++ b/src/lib/db/core.ts
@@ -219,6 +219,9 @@ const SCHEMA_SQL = `
     prefix TEXT,
     api_type TEXT,
     base_url TEXT,
+    chat_path TEXT,
+    models_path TEXT,
+    custom_headers_json TEXT,
     created_at TEXT NOT NULL,
     updated_at TEXT NOT NULL
   );
diff --git a/src/lib/db/migrations/095_provider_node_custom_headers.sql b/src/lib/db/migrations/095_provider_node_custom_headers.sql
new file mode 100644
index 0000000000..b2952eafb2
--- /dev/null
+++ b/src/lib/db/migrations/095_provider_node_custom_headers.sql
@@ -0,0 +1,5 @@
+-- Add custom_headers_json column to provider_nodes
+-- Stores JSON object of custom HTTP headers to send with requests to this provider
+-- NULL = no custom headers (backward compatible)
+-- Column uses _json suffix so rowToCamel auto-parses it
+ALTER TABLE provider_nodes ADD COLUMN custom_headers_json TEXT;
diff --git a/src/lib/db/providers.ts b/src/lib/db/providers.ts
index d593e492be..f55f8e6dc8 100644
--- a/src/lib/db/providers.ts
+++ b/src/lib/db/providers.ts
@@ -783,6 +783,8 @@ export async function createProviderNode(data: JsonRecord) {
   const db = getDbInstance() as unknown as DbLike;
   const now = new Date().toISOString();
 
+  const customHeadersJson = data.customHeaders ? JSON.stringify(data.customHeaders) : null;
+
   const node = {
     id: data.id || uuidv4(),
     type: data.type,
@@ -792,19 +794,32 @@ export async function createProviderNode(data: JsonRecord) {
     baseUrl: data.baseUrl || null,
     chatPath: data.chatPath || null,
     modelsPath: data.modelsPath || null,
+    customHeadersJson,
     createdAt: now,
     updatedAt: now,
   };
 
   db.prepare(
     `
-    INSERT INTO provider_nodes (id, type, name, prefix, api_type, base_url, chat_path, models_path, created_at, updated_at)
-    VALUES (@id, @type, @name, @prefix, @apiType, @baseUrl, @chatPath, @modelsPath, @createdAt, @updatedAt)
+    INSERT INTO provider_nodes (id, type, name, prefix, api_type, base_url, chat_path, models_path, custom_headers_json, created_at, updated_at)
+    VALUES (@id, @type, @name, @prefix, @apiType, @baseUrl, @chatPath, @modelsPath, @customHeadersJson, @createdAt, @updatedAt)
   `
   ).run(node);
 
   backupDbFile("pre-write");
-  return node;
+
+  const result: JsonRecord = { ...node };
+  if (customHeadersJson) {
+    try {
+      result.customHeaders = JSON.parse(customHeadersJson);
+    } catch {
+      result.customHeaders = null;
+    }
+  } else {
+    result.customHeaders = null;
+  }
+  delete result.customHeadersJson;
+  return result;
 }
 
 export async function updateProviderNode(id: string, data: JsonRecord) {
@@ -818,11 +833,15 @@ export async function updateProviderNode(id: string, data: JsonRecord) {
     updatedAt: new Date().toISOString(),
   };
 
+  if (data.customHeaders !== undefined) {
+    merged["customHeadersJson"] = data.customHeaders ? JSON.stringify(data.customHeaders) : null;
+  }
+
   db.prepare(
     `
     UPDATE provider_nodes SET type = @type, name = @name, prefix = @prefix,
     api_type = @apiType, base_url = @baseUrl, chat_path = @chatPath,
-    models_path = @modelsPath, updated_at = @updatedAt
+    models_path = @modelsPath, custom_headers_json = @customHeadersJson, updated_at = @updatedAt
     WHERE id = @id
   `
   ).run({
@@ -834,11 +853,25 @@ export async function updateProviderNode(id: string, data: JsonRecord) {
     baseUrl: merged["baseUrl"] || null,
     chatPath: merged["chatPath"] || null,
     modelsPath: merged["modelsPath"] || null,
+    customHeadersJson: merged["customHeadersJson"] || null,
     updatedAt: merged["updatedAt"],
   });
 
   backupDbFile("pre-write");
-  return merged;
+
+  const result: JsonRecord = { ...merged };
+  const storedJson = merged["customHeadersJson"] as string | null;
+  if (storedJson) {
+    try {
+      result.customHeaders = JSON.parse(storedJson);
+    } catch {
+      result.customHeaders = null;
+    }
+  } else {
+    result.customHeaders = null;
+  }
+  delete result.customHeadersJson;
+  return result;
 }
 
 export async function deleteProviderNode(id: string) {
diff --git a/src/shared/validation/schemas.ts b/src/shared/validation/schemas.ts
index c9e2b0609a..5576ce6a98 100644
--- a/src/shared/validation/schemas.ts
+++ b/src/shared/validation/schemas.ts
@@ -1917,6 +1917,32 @@ export const updateKeyPermissionsSchema = z
     }
   });
 
+const customHeadersSchema = z
+  .record(z.string(), z.string())
+  .nullable()
+  .optional()
+  .refine(
+    (val) => {
+      if (!val) return true;
+      const forbidden = new Set([
+        "host",
+        "connection",
+        "content-length",
+        "keep-alive",
+        "proxy-connection",
+        "transfer-encoding",
+        "te",
+        "trailer",
+        "upgrade",
+      ]);
+      for (const key of Object.keys(val)) {
+        if (forbidden.has(key.toLowerCase())) return false;
+      }
+      return true;
+    },
+    { message: "Custom headers contain forbidden hop-by-hop or framing headers" }
+  );
+
 export const createProviderNodeSchema = z
   .object({
     name: z.string().trim().min(1, "Name is required"),
@@ -1936,6 +1962,7 @@ export const createProviderNodeSchema = z
     compatMode: z.enum(["cc"]).optional(),
     chatPath: z.string().trim().startsWith("/").max(500).optional().or(z.literal("")),
     modelsPath: z.string().trim().startsWith("/").max(500).optional().or(z.literal("")),
+    customHeaders: customHeadersSchema,
   })
   .superRefine((value, ctx) => {
     const nodeType = value.type || "openai-compatible";
@@ -1964,6 +1991,7 @@ export const updateProviderNodeSchema = z.object({
   baseUrl: z.string().trim().min(1, "Base URL is required"),
   chatPath: z.string().trim().startsWith("/").max(500).optional().or(z.literal("")),
   modelsPath: z.string().trim().startsWith("/").max(500).optional().or(z.literal("")),
+  customHeaders: customHeadersSchema,
 });
 
 export const providerNodeValidateSchema = z.object({
diff --git a/tests/unit/custom-headers-provider-nodes.test.ts b/tests/unit/custom-headers-provider-nodes.test.ts
new file mode 100644
index 0000000000..d98d844796
--- /dev/null
+++ b/tests/unit/custom-headers-provider-nodes.test.ts
@@ -0,0 +1,592 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+
+const TEST_DATA_DIR = fs.mkdtempSync(path.join(os.tmpdir(), "omniroute-custom-headers-"));
+process.env.DATA_DIR = TEST_DATA_DIR;
+
+const core = await import("../../src/lib/db/core.ts");
+const providersDb = await import("../../src/lib/db/providers.ts");
+const providerNodesRoute = await import("../../src/app/api/provider-nodes/route.ts");
+const providerNodesIdRoute = await import("../../src/app/api/provider-nodes/[id]/route.ts");
+const { OPENAI_COMPATIBLE_PREFIX } = await import("../../src/shared/constants/providers.ts");
+const { createProviderNodeSchema, updateProviderNodeSchema } = await import("../../src/shared/validation/schemas.ts");
+const { DefaultExecutor } = await import("../../open-sse/executors/default.ts");
+
+async function resetStorage() {
+  core.resetDbInstance();
+  fs.rmSync(TEST_DATA_DIR, { recursive: true, force: true });
+  fs.mkdirSync(TEST_DATA_DIR, { recursive: true });
+}
+
+function makeRequest(body: Record<string, unknown>) {
+  return new Request("http://localhost/api/provider-nodes", {
+    method: "POST",
+    headers: { "content-type": "application/json" },
+    body: JSON.stringify(body),
+  });
+}
+
+function makeUpdateRequest(id: string, body: Record<string, unknown>) {
+  return new Request(`http://localhost/api/provider-nodes/${id}`, {
+    method: "PUT",
+    headers: { "content-type": "application/json" },
+    body: JSON.stringify(body),
+  });
+}
+
+test.beforeEach(async () => {
+  await resetStorage();
+});
+
+test.after(async () => {
+  await resetStorage();
+  fs.rmSync(TEST_DATA_DIR, { recursive: true, force: true });
+});
+
+test("createProviderNodeSchema accepts valid customHeaders as record of strings", () => {
+  const validInputs = [
+    { name: "Test", prefix: "test", apiType: "chat", customHeaders: { "X-Custom-1": "value1" } },
+    { name: "Test", prefix: "test", apiType: "chat", customHeaders: { "X-Header": "value", "X-Another": "value2" } },
+    { name: "Test", prefix: "test", apiType: "chat", customHeaders: {} },
+    { name: "Test", prefix: "test", apiType: "chat" },
+  ];
+
+  for (const input of validInputs) {
+    const result = createProviderNodeSchema.safeParse(input);
+    assert.equal(result.success, true, `Should accept: ${JSON.stringify(input)}`);
+  }
+});
+
+test("createProviderNodeSchema rejects customHeaders with non-string values", () => {
+  const invalidInputs = [
+    { customHeaders: { "X-Custom": 123 } },
+    { customHeaders: { "X-Custom": null } },
+    { customHeaders: { "X-Custom": true } },
+    { customHeaders: { "X-Custom": ["array"] } },
+    { customHeaders: { "X-Custom": { nested: "object" } } },
+  ];
+
+  for (const input of invalidInputs) {
+    const result = createProviderNodeSchema.safeParse(input);
+    assert.equal(result.success, false, `Should reject: ${JSON.stringify(input)}`);
+  }
+});
+
+test("createProviderNodeSchema rejects forbidden hop-by-hop headers", () => {
+  const forbiddenHeaders = [
+    "host", "connection", "content-length", "keep-alive",
+    "proxy-connection", "transfer-encoding", "te", "trailer", "upgrade",
+  ];
+
+  for (const header of forbiddenHeaders) {
+    const result = createProviderNodeSchema.safeParse({
+      customHeaders: { [header]: "value" },
+    });
+    assert.equal(result.success, false, `Should reject forbidden header: ${header}`);
+  }
+
+  const result = createProviderNodeSchema.safeParse({
+    customHeaders: { "HOST": "evil", "Content-Length": "999" },
+  });
+  assert.equal(result.success, false, "Should reject case-insensitive forbidden headers");
+});
+
+test("updateProviderNodeSchema accepts valid customHeaders", () => {
+  const validInputs = [
+    { customHeaders: { "X-Updated": "new-value" } },
+    { customHeaders: { "X-A": "v1", "X-B": "v2" } },
+    { customHeaders: null },
+    {},
+  ];
+
+  for (const input of validInputs) {
+    const result = updateProviderNodeSchema.safeParse({
+      name: "Test",
+      prefix: "test",
+      baseUrl: "https://test.com",
+      ...input,
+    });
+    assert.equal(result.success, true, `Should accept: ${JSON.stringify(input)}`);
+  }
+});
+
+test("updateProviderNodeSchema rejects forbidden headers", () => {
+  const result = updateProviderNodeSchema.safeParse({
+    name: "Test",
+    prefix: "test",
+    baseUrl: "https://test.com",
+    customHeaders: { "host": "evil.com" },
+  });
+  assert.equal(result.success, false);
+});
+
+test("provider nodes route creates OpenAI-compatible nodes with customHeaders", async () => {
+  const response = await providerNodesRoute.POST(
+    makeRequest({
+      name: "Custom Headers Node",
+      prefix: "custom-headers",
+      apiType: "chat",
+      baseUrl: "https://custom.example.com/v1",
+      customHeaders: {
+        "X-Custom-Auth": "auth-token-123",
+        "X-Request-ID": "req-abc",
+      },
+    })
+  );
+  const body = (await response.json()) as any;
+
+  assert.equal(response.status, 201);
+  assert.match(body.node.id, new RegExp(`^${OPENAI_COMPATIBLE_PREFIX}chat-`));
+  assert.deepEqual(body.node.customHeaders, {
+    "X-Custom-Auth": "auth-token-123",
+    "X-Request-ID": "req-abc",
+  });
+});
+
+test("provider nodes route creates nodes without customHeaders (null)", async () => {
+  const response = await providerNodesRoute.POST(
+    makeRequest({
+      name: "No Custom Headers",
+      prefix: "no-custom",
+      apiType: "chat",
+      baseUrl: "https://nocustom.example.com/v1",
+    })
+  );
+  const body = (await response.json()) as any;
+
+  assert.equal(response.status, 201);
+  assert.equal(body.node.customHeaders, null);
+});
+
+test("provider nodes route update modifies customHeaders", async () => {
+  const createResponse = await providerNodesRoute.POST(
+    makeRequest({
+      name: "Original Node",
+      prefix: "original",
+      apiType: "chat",
+      baseUrl: "https://original.example.com/v1",
+      customHeaders: { "X-Original": "original-value" },
+    })
+  );
+  const created = (await createResponse.json()) as any;
+  const nodeId = created.node.id;
+
+  const updateBody = {
+    name: "Updated Node",
+    prefix: "updated",
+    apiType: "chat",
+    baseUrl: "https://updated.example.com/v1",
+    customHeaders: { "X-Updated": "updated-value", "X-New": "new-header" },
+  };
+  const updateResponse = await providerNodesIdRoute.PUT(
+    makeUpdateRequest(nodeId, updateBody),
+    { params: Promise.resolve({ id: nodeId }) }
+  );
+  const updated = (await updateResponse.json()) as any;
+
+  assert.equal(updateResponse.status, 200);
+  assert.deepEqual(updated.node.customHeaders, {
+    "X-Updated": "updated-value",
+    "X-New": "new-header",
+  });
+});
+
+test("provider nodes route update can clear customHeaders by passing null", async () => {
+  const createResponse = await providerNodesRoute.POST(
+    makeRequest({
+      name: "Node With Headers",
+      prefix: "with-headers",
+      apiType: "chat",
+      baseUrl: "https://withheaders.example.com/v1",
+      customHeaders: { "X-Keep": "keep-value" },
+    })
+  );
+  const created = (await createResponse.json()) as any;
+  const nodeId = created.node.id;
+
+const clearBody = {
+    name: "Node Without Headers",
+    prefix: "no-headers",
+    apiType: "chat",
+    baseUrl: "https://noclear.example.com/v1",
+    customHeaders: null,
+  };
+  const updateResponse = await providerNodesIdRoute.PUT(
+    makeUpdateRequest(nodeId, clearBody),
+    { params: Promise.resolve({ id: nodeId }) }
+  );
+  const updated = (await updateResponse.json()) as any;
+
+  assert.equal(updateResponse.status, 200);
+  assert.equal(updated.node.customHeaders, null);
+});
+
+test("DefaultExecutor.buildHeaders applies customHeaders from providerSpecificData", () => {
+  const executor = new DefaultExecutor("openai-compatible-test");
+
+const headers = executor.buildHeaders(
+    {
+      apiKey: "test-key",
+      providerSpecificData: {
+        baseUrl: "https://proxy.example.com/v1",
+        customHeaders: {
+          "X-Custom-Auth": "custom-auth-value",
+          "X-Request-ID": "request-123",
+          "X-Custom-Header": "extra-value",
+        },
+      },
+    },
+    true
+  ) as Record<string, string>;
+
+  assert.equal(headers["X-Custom-Auth"], "custom-auth-value");
+  assert.equal(headers["X-Request-ID"], "request-123");
+  assert.equal(headers["X-Custom-Header"], "extra-value");
+  assert.equal(headers["Content-Type"], "application/json");
+  assert.equal(headers["Authorization"], "Bearer test-key");
+});
+
+test("DefaultExecutor.buildHeaders does NOT override auth headers with customHeaders", () => {
+  const executor = new DefaultExecutor("openai-compatible-test");
+
+  const headers = executor.buildHeaders(
+    {
+      apiKey: "real-key",
+      providerSpecificData: {
+        baseUrl: "https://proxy.example.com/v1",
+        customHeaders: {
+          "Authorization": "Bearer fake-token",
+          "x-api-key": "fake-key",
+          "X-Custom": "custom-value",
+        },
+      },
+    },
+    true
+  ) as Record<string, string>;
+
+  assert.equal(headers.Authorization, "Bearer real-key");
+  assert.equal(headers["x-api-key"], undefined);
+  assert.equal(headers["X-Custom"], "custom-value");
+});
+
+test("DefaultExecutor.buildHeaders blocks forbidden hop-by-hop headers from customHeaders", () => {
+  const executor = new DefaultExecutor("openai-compatible-test");
+
+  const headers = executor.buildHeaders(
+    {
+      apiKey: "test-key",
+      providerSpecificData: {
+        baseUrl: "https://proxy.example.com/v1",
+        customHeaders: {
+          "host": "evil.com",
+          "content-length": "999",
+          "connection": "close",
+          "X-Legitimate": "good-header",
+        },
+      },
+    },
+    true
+  ) as Record<string, string>;
+
+  assert.equal(headers.host, undefined);
+  assert.equal(headers["content-length"], undefined);
+  assert.equal(headers.connection, undefined);
+  assert.equal(headers["X-Legitimate"], "good-header");
+});
+
+test("DefaultExecutor.buildHeaders handles string customHeaders (JSON parsed)", () => {
+  const executor = new DefaultExecutor("openai-compatible-test");
+
+  const headers = executor.buildHeaders(
+    {
+      apiKey: "test-key",
+      providerSpecificData: {
+        baseUrl: "https://proxy.example.com/v1",
+        customHeaders: JSON.stringify({ "X-From-String": "parsed-value" }),
+      },
+    },
+    true
+  ) as Record<string, string>;
+
+  assert.equal(headers["X-From-String"], "parsed-value");
+});
+
+test("DefaultExecutor.buildHeaders handles invalid JSON in string customHeaders gracefully", () => {
+  const executor = new DefaultExecutor("openai-compatible-test");
+
+  const headers = executor.buildHeaders(
+    {
+      apiKey: "test-key",
+      providerSpecificData: {
+        baseUrl: "https://proxy.example.com/v1",
+        customHeaders: "not valid json {",
+      },
+    },
+    true
+  ) as Record<string, string>;
+
+  assert.equal(headers["X-From-String"], undefined);
+  assert.equal(headers.Authorization, "Bearer test-key");
+});
+
+test("DefaultExecutor.buildHeaders handles array customHeaders gracefully", () => {
+  const executor = new DefaultExecutor("openai-compatible-test");
+
+  const headers = executor.buildHeaders(
+    {
+      apiKey: "test-key",
+      providerSpecificData: {
+        baseUrl: "https://proxy.example.com/v1",
+        customHeaders: ["array", "not", "valid"],
+      },
+    },
+    true
+  ) as Record<string, string>;
+
+  assert.equal(headers["X-From-String"], undefined);
+  assert.equal(headers.Authorization, "Bearer test-key");
+});
+
+test("DefaultExecutor.buildHeaders handles null/undefined/empty customHeaders", () => {
+  const executor = new DefaultExecutor("openai-compatible-test");
+
+  const nullHeaders = executor.buildHeaders(
+    { apiKey: "key", providerSpecificData: { customHeaders: null } },
+    true
+  ) as Record<string, string>;
+  const undefinedHeaders = executor.buildHeaders(
+    { apiKey: "key", providerSpecificData: {} },
+    true
+  ) as Record<string, string>;
+  const emptyHeaders = executor.buildHeaders(
+    { apiKey: "key", providerSpecificData: { customHeaders: {} } },
+    true
+  ) as Record<string, string>;
+
+  for (const headers of [nullHeaders, undefinedHeaders, emptyHeaders]) {
+    assert.equal(headers["X-Anything"], undefined);
+    assert.equal(headers.Authorization, "Bearer key");
+  }
+});
+
+test("DefaultExecutor.buildHeaders customHeaders are case-sensitive for header names", () => {
+  const executor = new DefaultExecutor("openai-compatible-test");
+
+  const headers = executor.buildHeaders(
+    {
+      apiKey: "test-key",
+      providerSpecificData: {
+        baseUrl: "https://proxy.example.com/v1",
+        customHeaders: {
+          "x-lower": "lower-value",
+          "X-Upper": "upper-value",
+          "X-Mixed": "mixed-value",
+        },
+      },
+    },
+    true
+  ) as Record<string, string>;
+
+  assert.equal(headers["x-lower"], "lower-value");
+  assert.equal(headers["X-Upper"], "upper-value");
+  assert.equal(headers["X-Mixed"], "mixed-value");
+});
+
+test("DefaultExecutor.buildHeaders for non-openai-compatible providers ignores customHeaders", () => {
+  const executor = new DefaultExecutor("openai");
+
+  const headers = executor.buildHeaders(
+    {
+      apiKey: "test-key",
+      providerSpecificData: {
+        customHeaders: {
+          "X-Custom": "should-be-ignored",
+        },
+      },
+    },
+    true
+  ) as Record<string, string>;
+
+  assert.equal(headers["X-Custom"], undefined);
+  assert.equal(headers.Authorization, "Bearer test-key");
+});
+
+test("DefaultExecutor.execute sends customHeaders in the actual HTTP request", async () => {
+  const executor = new DefaultExecutor("openai-compatible-test");
+  const originalFetch = globalThis.fetch;
+  let capturedHeaders: Record<string, string> = {};
+
+  globalThis.fetch = async (_url: string | URL | Request, init: RequestInit = {}) => {
+    capturedHeaders = (init.headers as Record<string, string>) || {};
+    return new Response(JSON.stringify({ ok: true }), {
+      status: 200,
+      headers: { "Content-Type": "application/json" },
+    });
+  };
+
+  try {
+    await executor.execute({
+      model: "gpt-4.1",
+      body: { messages: [{ role: "user", content: "hi" }] },
+      stream: false,
+      credentials: {
+        apiKey: "test-key",
+        providerSpecificData: {
+          baseUrl: "https://test.proxy.com/v1",
+          customHeaders: {
+            "X-Request-ID": "test-req-123",
+            "X-Trace-Id": "trace-abc",
+          },
+        },
+      },
+    });
+
+    assert.equal(capturedHeaders["X-Request-ID"], "test-req-123");
+    assert.equal(capturedHeaders["X-Trace-Id"], "trace-abc");
+    assert.equal(capturedHeaders["Authorization"], "Bearer test-key");
+    assert.equal(capturedHeaders["Content-Type"], "application/json");
+  } finally {
+    globalThis.fetch = originalFetch;
+  }
+});
+
+test("DefaultExecutor.execute does NOT send forbidden headers from customHeaders in HTTP request", async () => {
+  const executor = new DefaultExecutor("openai-compatible-test");
+  const originalFetch = globalThis.fetch;
+  let capturedHeaders: Record<string, string> = {};
+
+  globalThis.fetch = async (_url: string | URL | Request, init: RequestInit = {}) => {
+    capturedHeaders = (init.headers as Record<string, string>) || {};
+    return new Response(JSON.stringify({ ok: true }), {
+      status: 200,
+      headers: { "Content-Type": "application/json" },
+    });
+  };
+
+  try {
+    await executor.execute({
+      model: "gpt-4.1",
+      body: { messages: [{ role: "user", content: "hi" }] },
+      stream: false,
+      credentials: {
+        apiKey: "test-key",
+        providerSpecificData: {
+          baseUrl: "https://test.proxy.com/v1",
+          customHeaders: {
+            "host": "evil.com",
+            "content-length": "9999",
+            "X-Legitimate": "good",
+          },
+        },
+      },
+    });
+
+    assert.equal(capturedHeaders.host, undefined);
+    assert.equal(capturedHeaders["content-length"], undefined);
+    assert.equal(capturedHeaders["X-Legitimate"], "good");
+    assert.equal(capturedHeaders.Authorization, "Bearer test-key");
+  } finally {
+    globalThis.fetch = originalFetch;
+  }
+});
+
+test("DefaultExecutor.execute does NOT allow customHeaders to override Authorization", async () => {
+  const executor = new DefaultExecutor("openai-compatible-test");
+  const originalFetch = globalThis.fetch;
+  let capturedHeaders: Record<string, string> = {};
+
+  globalThis.fetch = async (_url: string | URL | Request, init: RequestInit = {}) => {
+    capturedHeaders = (init.headers as Record<string, string>) || {};
+    return new Response(JSON.stringify({ ok: true }), {
+      status: 200,
+      headers: { "Content-Type": "application/json" },
+    });
+  };
+
+  try {
+    await executor.execute({
+      model: "gpt-4.1",
+      body: { messages: [{ role: "user", content: "hi" }] },
+      stream: false,
+      credentials: {
+        apiKey: "real-key",
+        providerSpecificData: {
+          baseUrl: "https://test.proxy.com/v1",
+          customHeaders: {
+            "Authorization": "Bearer forged-key",
+          },
+        },
+      },
+    });
+
+    assert.equal(capturedHeaders.Authorization, "Bearer real-key");
+    assert.notEqual(capturedHeaders.Authorization, "Bearer forged-key");
+  } finally {
+    globalThis.fetch = originalFetch;
+  }
+});
+
+test("db: createProviderNode and getProviderNodeById handle customHeaders as JSON", async () => {
+  const node = await providersDb.createProviderNode({
+    id: "openai-compatible-chat-custom-headers-db",
+    type: "openai-compatible",
+    name: "DB Custom Headers Test",
+    prefix: "db-custom",
+    apiType: "chat",
+    baseUrl: "https://db.example.com/v1",
+    customHeaders: { "X-DB-Header": "db-value", "X-Another": "another" },
+  });
+
+  assert.deepEqual(node.customHeaders, { "X-DB-Header": "db-value", "X-Another": "another" });
+
+  const retrieved = await providersDb.getProviderNodeById("openai-compatible-chat-custom-headers-db");
+  assert.deepEqual(retrieved.customHeaders, { "X-DB-Header": "db-value", "X-Another": "another" });
+});
+
+test("db: updateProviderNode modifies customHeaders", async () => {
+  const node = await providersDb.createProviderNode({
+    id: "openai-compatible-chat-update-custom",
+    type: "openai-compatible",
+    name: "Update Custom Test",
+    prefix: "update-custom",
+    apiType: "chat",
+    baseUrl: "https://update.example.com/v1",
+    customHeaders: { "X-Initial": "initial-value" },
+  });
+
+  assert.deepEqual(node.customHeaders, { "X-Initial": "initial-value" });
+
+  const updated = await providersDb.updateProviderNode(
+    "openai-compatible-chat-update-custom",
+    { customHeaders: { "X-Updated": "updated-value", "X-New-Header": "new" } }
+  );
+
+  assert.deepEqual(updated.customHeaders, { "X-Updated": "updated-value", "X-New-Header": "new" });
+
+  const retrieved = await providersDb.getProviderNodeById("openai-compatible-chat-update-custom");
+  assert.deepEqual(retrieved.customHeaders, { "X-Updated": "updated-value", "X-New-Header": "new" });
+});
+
+test("db: updateProviderNode can clear customHeaders by passing null", async () => {
+  const node = await providersDb.createProviderNode({
+    id: "openai-compatible-chat-clear-custom",
+    type: "openai-compatible",
+    name: "Clear Custom Test",
+    prefix: "clear-custom",
+    apiType: "chat",
+    baseUrl: "https://clear.example.com/v1",
+    customHeaders: { "X-ToClear": "clear-me" },
+  });
+
+  assert.deepEqual(node.customHeaders, { "X-ToClear": "clear-me" });
+
+  const updated = await providersDb.updateProviderNode(
+    "openai-compatible-chat-clear-custom",
+    { customHeaders: null }
+  );
+
+  assert.equal(updated.customHeaders, null);
+});
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