diff --git a/crates/fbuild-cli/src/cli/args.rs b/crates/fbuild-cli/src/cli/args.rs
index cf975e8f7..b0ae08555 100644
--- a/crates/fbuild-cli/src/cli/args.rs
+++ b/crates/fbuild-cli/src/cli/args.rs
@@ -1066,9 +1066,17 @@ pub fn resolve_project_dir(
     subcommand_dir: Option<String>,
     top_level_dir: &Option<String>,
 ) -> String {
-    subcommand_dir
+    let raw = subcommand_dir
         .or_else(|| top_level_dir.clone())
-        .unwrap_or_else(|| ".".to_string())
+        .unwrap_or_else(|| ".".to_string());
+    // Send the daemon an absolute path. A relative one is read against the
+    // daemon's working directory, and every path derived from it stays
+    // relative while the compiler runs from the project dir -- which is how
+    // `fbuild ci/kitchensink build` lost its libraries' include paths
+    // (FastLED/fbuild#1441). Lexical only: symlinks are not resolved.
+    std::path::absolute(&raw)
+        .map(|p| p.to_string_lossy().into_owned())
+        .unwrap_or(raw)
 }
 
 /// Known subcommand names for arg rewriting.
diff --git a/crates/fbuild-daemon/src/handlers/operations/build.rs b/crates/fbuild-daemon/src/handlers/operations/build.rs
index 4d9029a1d..6838065cf 100644
--- a/crates/fbuild-daemon/src/handlers/operations/build.rs
+++ b/crates/fbuild-daemon/src/handlers/operations/build.rs
@@ -2,6 +2,7 @@
 
 use super::common::{
     OperationGuard, export_artifacts_bundle, resolve_build_dir, resolve_client_path,
+    resolve_request_project_dir,
 };
 use crate::context::DaemonContext;
 use crate::models::{BuildRequest, OperationResponse};
@@ -9,7 +10,6 @@ use axum::Json;
 use axum::extract::State;
 use axum::http::StatusCode;
 use fbuild_core::channel::{UnboundedReceiver, UnboundedSender, unbounded};
-use std::path::PathBuf;
 use std::sync::Arc;
 use std::sync::atomic::{AtomicBool, Ordering};
 use tokio::sync::Notify;
@@ -146,7 +146,7 @@ pub async fn build(
     let request_id = req
         .request_id
         .unwrap_or_else(|| uuid::Uuid::new_v4().to_string());
-    let project_dir = PathBuf::from(&req.project_dir);
+    let project_dir = resolve_request_project_dir(&req.project_dir, req.caller_cwd.as_deref());
     let stream = req.stream;
 
     if !project_dir.exists() {
diff --git a/crates/fbuild-daemon/src/handlers/operations/common.rs b/crates/fbuild-daemon/src/handlers/operations/common.rs
index 1106eb169..01365b582 100644
--- a/crates/fbuild-daemon/src/handlers/operations/common.rs
+++ b/crates/fbuild-daemon/src/handlers/operations/common.rs
@@ -335,6 +335,26 @@ pub(crate) fn parse_deploy_route(
     }
 }
 
+/// A request's `project_dir` as an absolute path.
+///
+/// A relative project dir must be read against the *caller's* working
+/// directory, not the daemon's. Left relative, every path derived from it --
+/// the build dir, downloaded libraries, their `-I` flags -- stays relative,
+/// while the compiler runs from the absolute project dir, so those flags point
+/// nowhere (FastLED/fbuild#1441: `fbuild ci/kitchensink build` could not find
+/// a registry library's headers). Lexical only: symlinks are not resolved.
+pub(crate) fn resolve_request_project_dir(raw: &str, caller_cwd: Option<&str>) -> PathBuf {
+    let path = PathBuf::from(raw);
+    if path.is_absolute() {
+        return path;
+    }
+    let joined = match caller_cwd {
+        Some(cwd) => PathBuf::from(cwd).join(path),
+        None => path,
+    };
+    std::path::absolute(&joined).unwrap_or(joined)
+}
+
 pub(crate) fn resolve_client_path(
     raw: &str,
     caller_cwd: Option<&str>,
diff --git a/crates/fbuild-daemon/src/handlers/operations/deploy.rs b/crates/fbuild-daemon/src/handlers/operations/deploy.rs
index 0ce7d6463..34298416f 100644
--- a/crates/fbuild-daemon/src/handlers/operations/deploy.rs
+++ b/crates/fbuild-daemon/src/handlers/operations/deploy.rs
@@ -3,7 +3,7 @@
 use super::common::{
     DeployRoute, EmulatorKind, OperationGuard, compute_esp32_image_hash, export_artifacts_bundle,
     infer_default_emulator_kind, parse_deploy_route, qemu_extra_build_flags, resolve_build_dir,
-    resolve_client_path, trust_device_hash_enabled,
+    resolve_client_path, resolve_request_project_dir, trust_device_hash_enabled,
 };
 use super::deploy_port::{append_warning_to_stderr, choose_deploy_port};
 use super::monitor::{MonitorOutcome, run_monitor_loop};
@@ -73,7 +73,7 @@ pub async fn deploy(
         .request_id
         .clone()
         .unwrap_or_else(|| uuid::Uuid::new_v4().to_string());
-    let project_dir = PathBuf::from(&req.project_dir);
+    let project_dir = resolve_request_project_dir(&req.project_dir, req.caller_cwd.as_deref());
 
     if !project_dir.exists() {
         return (
diff --git a/crates/fbuild-daemon/src/handlers/operations/install_deps.rs b/crates/fbuild-daemon/src/handlers/operations/install_deps.rs
index 319839c29..486adbad7 100644
--- a/crates/fbuild-daemon/src/handlers/operations/install_deps.rs
+++ b/crates/fbuild-daemon/src/handlers/operations/install_deps.rs
@@ -1,13 +1,12 @@
 //! `POST /api/install-deps` — fetch toolchains, frameworks, and libraries
 //! without building.
 
-use super::common::OperationGuard;
+use super::common::{OperationGuard, resolve_request_project_dir};
 use crate::context::DaemonContext;
 use crate::models::{InstallDepsRequest, OperationResponse};
 use axum::Json;
 use axum::extract::State;
 use axum::http::StatusCode;
-use std::path::PathBuf;
 use std::sync::Arc;
 
 /// POST /api/install-deps
@@ -21,7 +20,7 @@ pub async fn install_deps(
     let request_id = req
         .request_id
         .unwrap_or_else(|| uuid::Uuid::new_v4().to_string());
-    let project_dir = PathBuf::from(&req.project_dir);
+    let project_dir = resolve_request_project_dir(&req.project_dir, req.caller_cwd.as_deref());
 
     if !project_dir.exists() {
         return (
diff --git a/crates/fbuild-daemon/src/handlers/operations/tests.rs b/crates/fbuild-daemon/src/handlers/operations/tests.rs
index 2e2e1a35e..a6137054f 100644
--- a/crates/fbuild-daemon/src/handlers/operations/tests.rs
+++ b/crates/fbuild-daemon/src/handlers/operations/tests.rs
@@ -194,3 +194,44 @@ mod image_hash_memo_tests {
         );
     }
 }
+
+mod request_project_dir_tests {
+    //! A request's project dir must come out absolute, read against the
+    //! caller's working directory (FastLED/fbuild#1441).
+    use super::super::common::resolve_request_project_dir;
+    use std::path::Path;
+
+    #[test]
+    fn relative_dir_is_joined_onto_caller_cwd() {
+        let cwd = std::env::temp_dir().join("caller");
+        let resolved = resolve_request_project_dir("ci/kitchensink", Some(cwd.to_str().unwrap()));
+        assert!(resolved.is_absolute());
+        assert_eq!(resolved, cwd.join("ci").join("kitchensink"));
+    }
+
+    #[test]
+    fn absolute_dir_is_kept_as_is() {
+        let abs = std::env::temp_dir().join("proj");
+        let resolved = resolve_request_project_dir(abs.to_str().unwrap(), Some("/elsewhere"));
+        assert_eq!(resolved, abs);
+    }
+
+    #[test]
+    fn relative_dir_without_caller_cwd_is_still_absolute() {
+        let resolved = resolve_request_project_dir("proj", None);
+        assert!(resolved.is_absolute());
+        assert!(resolved.ends_with(Path::new("proj")));
+    }
+
+    #[test]
+    fn dot_resolves_to_the_caller_cwd_itself() {
+        let cwd = std::env::temp_dir().join("caller");
+        let resolved = resolve_request_project_dir(".", Some(cwd.to_str().unwrap()));
+        assert!(resolved.is_absolute());
+        // `std::path::absolute` keeps a trailing `.` component lexically on
+        // some hosts; compare by components that matter.
+        let components: Vec<_> = resolved.components().collect();
+        let expected: Vec<_> = cwd.components().collect();
+        assert_eq!(components, expected);
+    }
+}