diff --git a/Cargo.lock b/Cargo.lock
index 44ea77ca..25b9b46e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4604,6 +4604,7 @@ dependencies = [
  "hex",
  "http 1.4.0",
  "openssl",
+ "pem",
  "rand 0.8.5",
  "rcgen",
  "reqwest 0.13.2",
diff --git a/crates/goose-server/Cargo.toml b/crates/goose-server/Cargo.toml
index 9621bed6..2045caa6 100644
--- a/crates/goose-server/Cargo.toml
+++ b/crates/goose-server/Cargo.toml
@@ -76,6 +76,7 @@ rcgen = "0.13"
 axum-server = { version = "0.8.0" }
 aws-lc-rs = { version = "1.16.0", optional = true }
 openssl = { version = "0.10", optional = true }
+pem = "3.0.6"
 
 [target.'cfg(windows)'.dependencies]
 winreg = { version = "0.55.0" }
diff --git a/crates/goose-server/src/commands/agent.rs b/crates/goose-server/src/commands/agent.rs
index f06c464b..26bb0915 100644
--- a/crates/goose-server/src/commands/agent.rs
+++ b/crates/goose-server/src/commands/agent.rs
@@ -5,7 +5,7 @@ use axum::middleware;
 use axum_server::Handle;
 use goose_server::auth::check_token;
 #[cfg(any(feature = "rustls-tls", feature = "native-tls"))]
-use goose_server::tls::self_signed_config;
+use goose_server::tls::setup_tls;
 use tower_http::cors::{Any, CorsLayer};
 use tracing::info;
 
@@ -78,7 +78,11 @@ pub async fn run() -> Result<()> {
     if settings.tls {
         #[cfg(any(feature = "rustls-tls", feature = "native-tls"))]
         {
-            let tls_setup = self_signed_config().await?;
+            let tls_setup = setup_tls(
+                settings.tls_cert_path.as_deref(),
+                settings.tls_key_path.as_deref(),
+            )
+            .await?;
 
             let handle = Handle::new();
             let shutdown_handle = handle.clone();
diff --git a/crates/goose-server/src/configuration.rs b/crates/goose-server/src/configuration.rs
index 4f28ec34..c6f45836 100644
--- a/crates/goose-server/src/configuration.rs
+++ b/crates/goose-server/src/configuration.rs
@@ -11,6 +11,8 @@ pub struct Settings {
     pub port: u16,
     #[serde(default = "default_tls")]
     pub tls: bool,
+    pub tls_cert_path: Option<String>,
+    pub tls_key_path: Option<String>,
 }
 
 impl Settings {
@@ -91,6 +93,8 @@ mod tests {
             host: "127.0.0.1".to_string(),
             port: 3000,
             tls: true,
+            tls_cert_path: None,
+            tls_key_path: None,
         };
         let addr = server_settings.socket_addr();
         assert_eq!(addr.to_string(), "127.0.0.1:3000");
diff --git a/crates/goose-server/src/tls.rs b/crates/goose-server/src/tls.rs
index 5eb7e3f4..8f1431a2 100644
--- a/crates/goose-server/src/tls.rs
+++ b/crates/goose-server/src/tls.rs
@@ -11,8 +11,9 @@
 //!   / SChannel respectively, but `axum-server` does not offer those backends so
 //!   the server listener always uses OpenSSL when this feature is active.
 
-use anyhow::Result;
+use anyhow::{bail, Result};
 use rcgen::{CertificateParams, DnType, KeyPair, SanType};
+use std::path::Path;
 
 #[cfg(feature = "rustls-tls")]
 pub type TlsConfig = axum_server::tls_rustls::RustlsConfig;
@@ -65,6 +66,45 @@ fn sha256_fingerprint(der: &[u8]) -> String {
     }
 }
 
+/// Load TLS configuration from user-provided PEM certificate and key files.
+///
+/// The SHA-256 fingerprint of the leaf certificate is computed and printed to
+/// stdout so the parent process (e.g. Electron) can pin it, just like the
+/// self-signed path.
+pub async fn from_pem_files(cert_path: &Path, key_path: &Path) -> Result<TlsSetup> {
+    let cert_pem = std::fs::read(cert_path)?;
+    let key_pem = std::fs::read(key_path)?;
+
+    // Parse the first PEM block to extract the DER-encoded certificate for fingerprinting.
+    let der = pem::parse(&cert_pem)?.into_contents();
+    let fingerprint = sha256_fingerprint(&der);
+    println!("GOOSED_CERT_FINGERPRINT={fingerprint}");
+
+    #[cfg(feature = "rustls-tls")]
+    let config = {
+        let _ = rustls::crypto::aws_lc_rs::default_provider().install_default();
+        axum_server::tls_rustls::RustlsConfig::from_pem(cert_pem, key_pem.clone()).await?
+    };
+
+    #[cfg(feature = "native-tls")]
+    let config = axum_server::tls_openssl::OpenSSLConfig::from_pem(&cert_pem, &key_pem)?;
+
+    Ok(TlsSetup {
+        config,
+        fingerprint,
+    })
+}
+
+/// Set up TLS, using user-provided PEM files if both paths are given,
+/// otherwise generating a self-signed certificate.
+pub async fn setup_tls(cert_path: Option<&str>, key_path: Option<&str>) -> Result<TlsSetup> {
+    match (cert_path, key_path) {
+        (Some(cert), Some(key)) => from_pem_files(Path::new(cert), Path::new(key)).await,
+        (None, None) => self_signed_config().await,
+        _ => bail!("Both GOOSE_TLS_CERT_PATH and GOOSE_TLS_KEY_PATH must be set, or neither"),
+    }
+}
+
 /// Generate a self-signed TLS certificate for localhost (127.0.0.1) and
 /// return a [`TlsSetup`] containing the server config and the SHA-256
 /// fingerprint of the generated certificate (colon-separated hex).
diff --git a/ui/desktop/src/components/settings/app/ExternalBackendSection.tsx b/ui/desktop/src/components/settings/app/ExternalBackendSection.tsx
index deeff84b..5f7fcd8e 100644
--- a/ui/desktop/src/components/settings/app/ExternalBackendSection.tsx
+++ b/ui/desktop/src/components/settings/app/ExternalBackendSection.tsx
@@ -41,6 +41,18 @@ const i18n = defineMessages({
     id: 'externalBackendSection.secretKeyHelp',
     defaultMessage: 'The secret key configured on the goosed server (GOOSE_SERVER__SECRET_KEY)',
   },
+  certFingerprint: {
+    id: 'externalBackendSection.certFingerprint',
+    defaultMessage: 'Certificate Fingerprint (optional)',
+  },
+  certFingerprintPlaceholder: {
+    id: 'externalBackendSection.certFingerprintPlaceholder',
+    defaultMessage: 'AA:BB:CC:... or sha256/base64',
+  },
+  certFingerprintHelp: {
+    id: 'externalBackendSection.certFingerprintHelp',
+    defaultMessage: 'Pin a specific TLS certificate fingerprint. If omitted, the certificate is trusted on first use (TOFU).',
+  },
   restartNote: {
     id: 'externalBackendSection.restartNote',
     defaultMessage:
@@ -189,6 +201,25 @@ export default function ExternalBackendSection() {
                 </p>
               </div>
 
+              <div className="space-y-2">
+                <label htmlFor="external-cert-fingerprint" className="text-text-primary text-xs">
+                  {intl.formatMessage(i18n.certFingerprint)}
+                </label>
+                <Input
+                  id="external-cert-fingerprint"
+                  type="text"
+                  placeholder={intl.formatMessage(i18n.certFingerprintPlaceholder)}
+                  value={config.certFingerprint || ''}
+                  onChange={(e) => updateField('certFingerprint', e.target.value)}
+                  onBlur={() => saveConfig(config)}
+                  disabled={isSaving}
+                  className="font-mono text-xs"
+                />
+                <p className="text-xs text-text-secondary">
+                  {intl.formatMessage(i18n.certFingerprintHelp)}
+                </p>
+              </div>
+
               <div className="bg-amber-50 dark:bg-amber-950 border border-amber-200 dark:border-amber-800 rounded-md p-3">
                 <p className="text-xs text-amber-800 dark:text-amber-200">
                   <strong>Note:</strong> {intl.formatMessage(i18n.restartNote)}
diff --git a/ui/desktop/src/goosed.ts b/ui/desktop/src/goosed.ts
index 9f211e81..0dafe833 100644
--- a/ui/desktop/src/goosed.ts
+++ b/ui/desktop/src/goosed.ts
@@ -142,6 +142,7 @@ export interface ExternalGoosedConfig {
   enabled: boolean;
   url?: string;
   secret?: string;
+  certFingerprint?: string;
 }
 
 export interface StartGoosedOptions {
diff --git a/ui/desktop/src/i18n/messages/en.json b/ui/desktop/src/i18n/messages/en.json
index a2655c06..36cc72d6 100644
--- a/ui/desktop/src/i18n/messages/en.json
+++ b/ui/desktop/src/i18n/messages/en.json
@@ -1136,6 +1136,15 @@
   "extensionsView.searchPlaceholder": {
     "defaultMessage": "Search extensions..."
   },
+  "externalBackendSection.certFingerprint": {
+    "defaultMessage": "Certificate Fingerprint (optional)"
+  },
+  "externalBackendSection.certFingerprintHelp": {
+    "defaultMessage": "Pin a specific TLS certificate fingerprint. If omitted, the certificate is trusted on first use (TOFU)."
+  },
+  "externalBackendSection.certFingerprintPlaceholder": {
+    "defaultMessage": "AA:BB:CC:... or sha256/base64"
+  },
   "externalBackendSection.description": {
     "defaultMessage": "By default goose launches a server for you, use this to connect to an external goose server"
   },
diff --git a/ui/desktop/src/main.ts b/ui/desktop/src/main.ts
index cdef3f0a..821ae797 100644
--- a/ui/desktop/src/main.ts
+++ b/ui/desktop/src/main.ts
@@ -117,17 +117,26 @@ async function configureProxy() {
 
 if (started) app.quit();
 
-// Accept self-signed certificates from the local goosed server.
+// Certificate trust for goosed servers (local and external).
 // Both certificate-error (renderer) and setCertificateVerifyProc (main-process
-// net.fetch) pin to the exact cert fingerprint emitted by goosed at startup.
-// Before the fingerprint is available (during the health-check bootstrap
-// window) any localhost cert is accepted so the server can come up.
+// net.fetch) pin to the exact cert fingerprint. For locally-spawned goosed the
+// fingerprint comes from its stdout; for external backends we use Trust-On-First-Use
+// (TOFU) — the first TLS handshake pins the cert for the lifetime of the process.
 let pinnedCertFingerprint: string | null = null;
 
+// Cached hostname of the configured external goosed server, updated when a
+// chat is created so we don't hit the filesystem on every TLS handshake.
+let trustedExternalHostname: string | null = null;
+
 function isLocalhost(hostname: string): boolean {
   return hostname === '127.0.0.1' || hostname === 'localhost';
 }
 
+function isTrustedHost(hostname: string): boolean {
+  if (isLocalhost(hostname)) return true;
+  return trustedExternalHostname !== null && hostname === trustedExternalHostname;
+}
+
 function normalizeFingerprint(fp: string): string {
   if (fp.startsWith('sha256/')) {
     const b64 = fp.slice('sha256/'.length);
@@ -145,7 +154,7 @@ function normalizeFingerprint(fp: string): string {
 // window) any localhost cert is accepted so the server can come up.
 app.on('certificate-error', (event, _webContents, url, _error, certificate, callback) => {
   const parsed = new URL(url);
-  if (!isLocalhost(parsed.hostname)) {
+  if (!isTrustedHost(parsed.hostname)) {
     callback(false);
     return;
   }
@@ -155,6 +164,8 @@ app.on('certificate-error', (event, _webContents, url, _error, certificate, call
     event.preventDefault();
     callback(match);
   } else {
+    // TOFU: pin the certificate from the first successful handshake.
+    pinnedCertFingerprint = normalizeFingerprint(certificate.fingerprint);
     event.preventDefault();
     callback(true);
   }
@@ -163,17 +174,19 @@ app.on('certificate-error', (event, _webContents, url, _error, certificate, call
 // Main-process net.fetch: pin to the exact cert goosed generated.
 app.whenReady().then(() => {
   session.defaultSession.setCertificateVerifyProc((request, callback) => {
-    if (!isLocalhost(request.hostname)) {
+    if (!isTrustedHost(request.hostname)) {
       callback(-3);
       return;
     }
     if (!pinnedCertFingerprint) {
+      // TOFU: pin the certificate from the first successful handshake.
+      pinnedCertFingerprint = normalizeFingerprint(request.certificate.fingerprint);
       callback(0);
       return;
     }
     const match =
       normalizeFingerprint(request.certificate.fingerprint) === pinnedCertFingerprint.toUpperCase();
-    callback(match ? 0 : -3);
+    callback(match ? 0 : -2);
   });
 });
 
@@ -574,6 +587,26 @@ const createChat = async (app: App, options: CreateChatOptions = {}) => {
   const settings = getSettings();
   const serverSecret = getServerSecret(settings);
 
+  // Update the cached trusted-external-hostname so the TLS handlers allow
+  // connections to the configured remote backend.
+  if (settings.externalGoosed?.enabled && settings.externalGoosed.url) {
+    try {
+      trustedExternalHostname = new URL(settings.externalGoosed.url).hostname;
+    } catch {
+      trustedExternalHostname = null;
+    }
+  } else {
+    trustedExternalHostname = null;
+  }
+
+  // If the user provided a cert fingerprint for the external backend, pin it
+  // directly (skips TOFU). Otherwise reset so the first handshake pins via TOFU.
+  if (settings.externalGoosed?.enabled && settings.externalGoosed.certFingerprint) {
+    pinnedCertFingerprint = normalizeFingerprint(settings.externalGoosed.certFingerprint);
+  } else {
+    pinnedCertFingerprint = null;
+  }
+
   const goosedResult = await startGoosed({
     serverSecret,
     dir: dir || os.homedir(),
@@ -586,8 +619,9 @@ const createChat = async (app: App, options: CreateChatOptions = {}) => {
     logger: log,
   });
 
-  // Pin the certificate fingerprint so the cert handlers above only accept
-  // the exact cert that *this* goosed instance generated.
+  // For locally-spawned goosed, pin using the fingerprint from stdout.
+  // For external backends the TOFU path in the cert handlers will pin
+  // the fingerprint on the first successful TLS handshake.
   if (goosedResult.certFingerprint) {
     pinnedCertFingerprint = goosedResult.certFingerprint;
   }
diff --git a/ui/desktop/src/utils/settings.ts b/ui/desktop/src/utils/settings.ts
index f23cdd59..6e491b9c 100644
--- a/ui/desktop/src/utils/settings.ts
+++ b/ui/desktop/src/utils/settings.ts
@@ -2,6 +2,7 @@ export interface ExternalGoosedConfig {
   enabled: boolean;
   url: string;
   secret: string;
+  certFingerprint?: string;
 }
 
 export interface KeyboardShortcuts {