Invoke cargo-ndk directly from Android Gradle

Co-authored-by: Codex <noreply@openai.com>

android/build.gradle.kts

@@ -21,8 +21,28 @@ val codexTargets = mapOf(
 tasks.register<Exec>("buildCodexCliNative") {
     group = "build"
     description = "Build the Android codex binary packaged into the Agent and Genie APKs."
-    workingDir = repoRoot
-    commandLine("just", "android-build")
+    workingDir = repoRoot.resolve("codex-rs")
+    environment("CARGO_TARGET_DIR", "target/android")
+    val cargoArgs = mutableListOf(
+        "cargo",
+        "ndk",
+        "--platform",
+        "26",
+        "-t",
+        "arm64-v8a",
+        "-t",
+        "x86_64",
+        "build",
+        "-p",
+        "codex-cli",
+    )
+    if (skipAndroidLto) {
+        cargoArgs += listOf("--profile", "android-release-no-lto")
+    } else {
+        cargoArgs += "--release"
+    }
+    cargoArgs += listOf("--bin", "codex")
+    commandLine(cargoArgs)
     if (skipAndroidLto) {
         environment("CODEX_ANDROID_SKIP_LTO", "1")
     }
@@ -31,8 +51,6 @@ tasks.register<Exec>("buildCodexCliNative") {
             exclude("target/**")
         },
     ).withPathSensitivity(PathSensitivity.RELATIVE)
-    inputs.file(repoRoot.resolve("justfile"))
-        .withPathSensitivity(PathSensitivity.RELATIVE)
     outputs.files(
         codexTargets.values.map { triple ->
             repoRoot.resolve("codex-rs/target/android/${triple}/${codexCargoProfileDir}/codex")

docs/android-build.md

@@ -60,10 +60,10 @@ If you prefer the system Gradle install, use `gradle :app:assembleDebug` from
 The Agent/Genie prototype modules also require
 `ANDROID_AGENT_PLATFORM_STUB_SDK_ZIP` (or `-PagentPlatformStubSdkZip=...`) so
 Gradle can compile against the stub SDK jar. The Agent APK and Genie APK both
-package the Android `codex` binary as `libcodex.so`. Gradle now rebuilds that
-native binary automatically before `:app:assembleDebug` and
-`:genie:assembleDebug`, so plain APK builds no longer silently package a stale
-`libcodex.so`.
+package the Android `codex` binary as `libcodex.so`. Gradle now runs the
+equivalent of `cargo ndk ... build -p codex-cli --bin codex` automatically
+before `:app:assembleDebug` and `:genie:assembleDebug`, so plain APK builds no
+longer silently package a stale `libcodex.so`.
 
 To install both APKs, assign the AGENT/GENIE roles, grant notifications, and
 optionally seed `auth.json` into the Agent sandbox: