impl: fall back to CODER_HEADER_COMMAND when the header command setting is blank

CHANGELOG.md

@@ -4,6 +4,10 @@
 
 ## Unreleased
 
+### Added
+
+- the header command falls back to the `CODER_HEADER_COMMAND` environment variable when the setting is blank, matching the Coder CLI and the VS Code extension
+
 ## 2.23.1 - 2026-01-21
 
 ### Changed

src/main/kotlin/com/coder/gateway/CoderSettingsConfigurable.kt

@@ -2,6 +2,7 @@ package com.coder.gateway
 
 import com.coder.gateway.services.CoderSettingsService
 import com.coder.gateway.services.CoderSettingsStateService
+import com.coder.gateway.settings.CODER_HEADER_COMMAND
 import com.coder.gateway.settings.CODER_SSH_CONFIG_OPTIONS
 import com.coder.gateway.util.canCreateDirectory
 import com.intellij.openapi.components.service
@@ -89,7 +90,10 @@ class CoderSettingsConfigurable : BoundConfigurable("Coder") {
                 textField().resizableColumn().align(AlignX.FILL)
                     .bindText(state::headerCommand)
                     .comment(
-                        CoderGatewayBundle.message("gateway.connector.settings.header-command.comment"),
+                        CoderGatewayBundle.message(
+                            "gateway.connector.settings.header-command.comment",
+                            CODER_HEADER_COMMAND,
+                        ),
                     )
             }.layout(RowLayout.PARENT_GRID)
             row(CoderGatewayBundle.message("gateway.connector.settings.tls-cert-path.title")) {

src/main/kotlin/com/coder/gateway/settings/CoderSettings.kt

@@ -14,6 +14,7 @@ import java.nio.file.Files
 import java.nio.file.Path
 import java.nio.file.Paths
 
+const val CODER_HEADER_COMMAND = "CODER_HEADER_COMMAND"
 const val CODER_SSH_CONFIG_OPTIONS = "CODER_SSH_CONFIG_OPTIONS"
 const val CODER_URL = "CODER_URL"
 
@@ -76,8 +77,8 @@ open class CoderSettingsState(
 
     // An external command that outputs additional HTTP headers added to all
     // requests. The command must output each header as `key=value` on its own
-    // line. The following environment variables will be available to the
-    // process: CODER_URL.
+    // line. When this setting is blank, the CODER_HEADER_COMMAND environment
+    // variable is used instead, if set.
     open var headerCommand: String = "",
     // Optionally set this to the path of a certificate to use for TLS
     // connections. The certificate should be in X.509 PEM format.
@@ -194,10 +195,12 @@ open class CoderSettings(
     val defaultSignatureNameByOsAndArch: String get() = getCoderSignatureForOS(getOS(), getArch())
 
     /**
-     * A command to run to set headers for API calls.
+     * A command to run to set headers for API calls. Falls back to the
+     * CODER_HEADER_COMMAND environment variable (the same variable the Coder
+     * CLI reads) when the setting is blank.
      */
     val headerCommand: String
-        get() = state.headerCommand
+        get() = state.headerCommand.ifBlank { env.get(CODER_HEADER_COMMAND) }
 
     /**
      * Whether to disable automatically starting a workspace when connecting.

src/main/resources/messages/CoderGatewayBundle.properties

@@ -82,8 +82,8 @@ gateway.connector.settings.fallback-on-coder-for-signatures.comment=Verify binar
 gateway.connector.settings.header-command.title=Header command
 gateway.connector.settings.header-command.comment=An external command that \
   outputs additional HTTP headers added to all requests. The command must \
-  output each header as `key=value` on its own line. The following \
-  environment variables will be available to the process: CODER_URL.
+  output each header as `key=value` on its own line. When this setting is \
+  left blank, the environment variable {0} is used instead, if set.
 gateway.connector.settings.tls-cert-path.title=Cert path
 gateway.connector.settings.tls-cert-path.comment=Optionally set this to \
   the path of a certificate to use for TLS connections. The certificate \

src/test/kotlin/com/coder/gateway/settings/CoderSettingsTest.kt

@@ -243,6 +243,27 @@ internal class CoderSettingsTest {
         assertEquals(Pair("http://test.gateway.coder.com$expected", null), got)
     }
 
+    @Test
+    fun testHeaderCommand() {
+        var settings = CoderSettings(CoderSettingsState(headerCommand = "header command from state"))
+        assertEquals("header command from state", settings.headerCommand)
+
+        settings =
+            CoderSettings(
+                CoderSettingsState(),
+                env = Environment(mapOf(CODER_HEADER_COMMAND to "header command from env")),
+            )
+        assertEquals("header command from env", settings.headerCommand)
+
+        // State has precedence.
+        settings =
+            CoderSettings(
+                CoderSettingsState(headerCommand = "header command from state"),
+                env = Environment(mapOf(CODER_HEADER_COMMAND to "header command from env")),
+            )
+        assertEquals("header command from state", settings.headerCommand)
+    }
+
     @Test
     fun testSSHConfigOptions() {
         var settings = CoderSettings(CoderSettingsState(sshConfigOptions = "ssh config options from state"))