diff --git a/packages/web/server/lib/small-model/DOCUMENTATION.md b/packages/web/server/lib/small-model/DOCUMENTATION.md
index 56769495..dfe20b6f 100644
--- a/packages/web/server/lib/small-model/DOCUMENTATION.md
+++ b/packages/web/server/lib/small-model/DOCUMENTATION.md
@@ -51,6 +51,8 @@ other runtime API.
     provider's base URL, resolved from (1) `provider.<id>.options.baseURL`
     in the OpenCode config, (2) the hardcoded `https://api.openai.com/v1`
      endpoint, or (3) the provider's `api` field from the models.dev catalog.
+    Configured API keys honor OpenCode's `{env:NAME}` and `{file:path}`
+    substitutions; file contents and resolved credentials remain server-side.
   - `[small-model:diagnostic]` logs record provider/model, input character
     counts, output budget, thinking toggle, HTTP/finish status, and
     content/reasoning lengths without logging prompts, response text, or
diff --git a/packages/web/server/lib/small-model/call.js b/packages/web/server/lib/small-model/call.js
index b67e3343..df3bdd1a 100644
--- a/packages/web/server/lib/small-model/call.js
+++ b/packages/web/server/lib/small-model/call.js
@@ -1,5 +1,8 @@
+import fs from 'fs';
+import os from 'os';
+import path from 'path';
 import { readAuthFile, writeAuthFile } from '../opencode/auth.js';
-import { readConfig } from '../opencode/shared.js';
+import { readConfig, readConfigLayers } from '../opencode/shared.js';
 import { getCatalogProvider } from './catalog.js';
 import { getAuthEntryForProvider } from './resolve.js';
 
@@ -312,13 +315,48 @@ const callCodexResponses = async ({ accessToken, accountId, modelID, prompt, sys
 // Custom provider configuration support
 // ---------------------------------------------------------------------------
 
+const resolveConfigApiKey = (value, workingDirectory, providerID) => {
+  const envMatch = value.match(/^\{env:([^}]+)\}$/i);
+  if (envMatch) {
+    return process.env[envMatch[1].trim()]?.trim() || null;
+  }
+
+  const fileMatch = value.match(/^\{file:(.+)\}$/i);
+  if (!fileMatch) return value;
+
+  const configuredPath = fileMatch[1].trim();
+  let resolvedPath;
+  if (configuredPath === '~' || configuredPath.startsWith('~/') || configuredPath.startsWith('~\\')) {
+    resolvedPath = path.join(os.homedir(), configuredPath.slice(2));
+  } else if (path.isAbsolute(configuredPath)) {
+    resolvedPath = configuredPath;
+  } else {
+    const layers = readConfigLayers(workingDirectory);
+    const source = [
+      { config: layers.customConfig, filePath: layers.paths.customPath },
+      { config: layers.projectConfig, filePath: layers.paths.projectPath },
+      { config: layers.userConfig, filePath: layers.paths.userPath },
+    ].find(({ config }) => config?.provider?.[providerID]?.options?.apiKey === value);
+    resolvedPath = path.resolve(source?.filePath ? path.dirname(source.filePath) : workingDirectory || process.cwd(), configuredPath);
+  }
+
+  try {
+    const key = fs.readFileSync(resolvedPath, 'utf8').trim();
+    if (!key) throw new Error('empty file');
+    return key;
+  } catch {
+    throw new Error(`Failed to resolve configured apiKey file for provider "${providerID}"`);
+  }
+};
+
 const readProviderConfig = (workingDirectory, providerID) => {
   try {
     const config = readConfig(workingDirectory);
     const providerCfg = config?.provider?.[providerID];
     if (!providerCfg || typeof providerCfg !== 'object') return null;
     const baseURL = typeof providerCfg?.options?.baseURL === 'string' ? providerCfg.options.baseURL.trim() : null;
-    const apiKey = typeof providerCfg?.options?.apiKey === 'string' ? providerCfg.options.apiKey.trim() : null;
+    const rawApiKey = typeof providerCfg?.options?.apiKey === 'string' ? providerCfg.options.apiKey.trim() : null;
+    const apiKey = rawApiKey ? resolveConfigApiKey(rawApiKey, workingDirectory, providerID) : null;
     return {
       baseURL,
       // Shape the config-supplied key as a regular api-key auth entry so it
diff --git a/packages/web/server/lib/small-model/call.test.js b/packages/web/server/lib/small-model/call.test.js
index 34d73b16..86602217 100644
--- a/packages/web/server/lib/small-model/call.test.js
+++ b/packages/web/server/lib/small-model/call.test.js
@@ -1,3 +1,6 @@
+import fs from 'fs';
+import os from 'os';
+import path from 'path';
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
 
 // readConfig reads merged opencode config layers from disk; mock it so each
@@ -6,10 +9,11 @@ import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
 // untouched for this file.
 vi.mock('../opencode/shared.js', () => ({
   readConfig: vi.fn(),
+  readConfigLayers: vi.fn(),
 }));
 
 const { callSmallModel } = await import('./call.js');
-const { readConfig } = await import('../opencode/shared.js');
+const { readConfig, readConfigLayers } = await import('../opencode/shared.js');
 
 // Minimal catalog fragment used by the catalog-based base URL resolution case.
 const CATALOG = {
@@ -50,13 +54,68 @@ describe('callSmallModel — custom provider config', () => {
     originalFetch = globalThis.fetch;
     globalThis.fetch = fetchMock;
     readConfig.mockReset();
+    readConfigLayers.mockReset();
   });
 
   afterEach(() => {
     globalThis.fetch = originalFetch;
+    vi.restoreAllMocks();
+    delete process.env.OPENCHAMBER_TEST_PROVIDER_KEY;
   });
 
   describe('config-supplied credentials (no auth.json entry)', () => {
+    it('resolves an OpenCode file variable before sending the API key', async () => {
+      const secretPath = path.join(os.homedir(), '.secret');
+      const originalReadFileSync = fs.readFileSync;
+      vi.spyOn(fs, 'readFileSync').mockImplementation((filePath, ...args) => {
+        if (filePath === secretPath) return 'sk-file-key\n';
+        return originalReadFileSync(filePath, ...args);
+      });
+      readConfig.mockReturnValue({
+        provider: {
+          custom: {
+            options: { apiKey: '{file:~/.secret}', baseURL: 'https://proxy.example.test/v1' },
+          },
+        },
+      });
+      fetchMock.mockResolvedValue(ok('hello'));
+
+      await callSmallModel({
+        auth: {},
+        catalog: {},
+        workingDirectory: '/proj',
+        providerID: 'custom',
+        modelID: 'model',
+        prompt: 'hi',
+      });
+
+      expect(lastCall(fetchMock).init.headers.Authorization).toBe('Bearer sk-file-key');
+      expect(JSON.stringify(fetchMock.mock.calls[0][1])).not.toContain('{file:');
+    });
+
+    it('resolves an OpenCode environment variable before sending the API key', async () => {
+      process.env.OPENCHAMBER_TEST_PROVIDER_KEY = 'sk-env-key';
+      readConfig.mockReturnValue({
+        provider: {
+          custom: {
+            options: { apiKey: '{env:OPENCHAMBER_TEST_PROVIDER_KEY}', baseURL: 'https://proxy.example.test/v1' },
+          },
+        },
+      });
+      fetchMock.mockResolvedValue(ok('hello'));
+
+      await callSmallModel({
+        auth: {},
+        catalog: {},
+        workingDirectory: '/proj',
+        providerID: 'custom',
+        modelID: 'model',
+        prompt: 'hi',
+      });
+
+      expect(lastCall(fetchMock).init.headers.Authorization).toBe('Bearer sk-env-key');
+    });
+
     it('uses apiKey and baseURL from provider config when no auth.json entry exists', async () => {
       readConfig.mockReturnValue({
         provider: {