claw-store/src/claw_cargo.rs

@@ -1,38 +1,42 @@
-//! `claw-cargo` — fingerprint-keyed cargo build cache (Phase 5b).
+//! `claw-cargo` — fingerprint-keyed cargo build cache CLI (Phase 5b/5c).
 //!
-//! Wraps `cargo build` with a peer-cache lookup. Flow:
+//! Wraps `cargo build` with a peer-cache lookup:
 //!
 //! ```text
-//! 1. compute_workspace_fingerprint(workspace, profile, features)
+//! HIT : GetRef → BlobStat → BlobGetStream → restore_target → cargo build
-//! 2. QUIC + mTLS connect to peer
+//! MISS: cargo build → capture_target → BlobPutStream → PutRef
-//! 3. GetRef(fingerprint) → BlobId?
-//!    HIT: BlobGetStream → restore_target → cargo build (fast, just workspace)
-//!    MISS: cargo build (full) → capture_target → BlobPutStream → PutRef
 //! ```
 //!
-//! First argument after subcommand flags is passed through to cargo verbatim,
+//! Config precedence (later wins):
-//! so `claw-cargo build --profile release -p my-crate` works the same as
+//!   1. Built-in defaults (profile=dev, features=[])
-//! `cargo build --profile release -p my-crate` — the only difference is
+//!   2. `~/.claw-cargo/config.toml`
-//! the pre/post cache lookup.
+//!   3. `<workspace>/.claw-cargo.toml`
+//!   4. CLI flags
+//!
+//! Subcommands:
+//! * `build`       — run cargo with cache lookup + populate on miss
+//! * `prefetch`    — download+restore cache into target/, no cargo
+//! * `status`      — print fingerprint + peer cache state (no cargo)
+//! * `fingerprint` — print fingerprint only (no network)
 
-mod cluster;
+mod actions;
 mod cargo_init;
+mod cluster;
 mod config;
+mod daemon;
 mod head_watch;
 mod hot;
 mod manifest;
 mod restore;
+mod serve;
 mod snapshot;
 mod sync;
 mod zfs;
-mod actions;
-mod daemon;
-mod serve;
 
-use anyhow::{bail, Context, Result};
+use anyhow::{Context, Result};
 use clap::{Parser, Subcommand};
 use std::net::SocketAddr;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 use std::process::Command;
 use std::time::Instant;
 
@@ -40,6 +44,7 @@ use crate::cluster::blob::BlobId;
 use crate::cluster::build_cache::{
     capture_target, compute_workspace_fingerprint, restore_target, Fingerprint,
 };
+use crate::cluster::client_config::{ClientConfig, ResolvedClientConfig};
 use crate::cluster::rpc::{
     call_blob_get_stream, call_blob_put_stream, call_blob_stat, call_get_ref, call_put_ref,
 };
@@ -58,46 +63,62 @@ struct Cli {
 
 #[derive(Subcommand)]
 enum Cmd {
-    /// Build with cache lookup: hit → restore + cargo build (fast);
+    /// Build with cache lookup: hit → restore + cargo build; miss →
-    /// miss → cargo build + capture + upload.
+    /// cargo build + capture + upload.
     Build(BuildArgs),
-    /// Print the fingerprint for the current workspace without touching
+    /// Download + restore the cached target dir into `target/<profile>`
-    /// the cache. Useful for diagnosis + integration tests.
+    /// without running cargo. Prints hit/miss + bytes.
-    Fingerprint {
+    Prefetch(PeerArgs),
-        #[arg(long, default_value = "dev")]
+    /// Print the fingerprint + peer cache state, no build, no download.
-        profile: String,
+    Status(PeerArgs),
-        #[arg(long, num_args = 0.., value_delimiter = ',')]
+    /// Print the fingerprint only. Local, no network.
-        features: Vec<String>,
+    Fingerprint(LocalArgs),
-        #[arg(long)]
-        workspace: Option<PathBuf>,
-    },
 }
 
-#[derive(clap::Args)]
+/// Args every network-touching subcommand accepts (with layered
-struct BuildArgs {
+/// defaults from `~/.claw-cargo/config.toml` + workspace config).
-    /// Peer's RPC socket (gossip_port + 1 by default).
+#[derive(clap::Args, Debug, Clone)]
+struct PeerArgs {
+    /// Peer's node name (overrides config).
     #[arg(long)]
-    peer_addr: SocketAddr,
+    peer: Option<String>,
-    /// Peer's node name — must match the peer's leaf cert SAN.
+    /// Peer's RPC socket (overrides config).
     #[arg(long)]
-    peer: String,
+    peer_addr: Option<SocketAddr>,
-    /// Directory holding this node's mTLS material
+    /// Directory holding this node's mTLS material (overrides config).
-    /// (`ca.crt` + `node.crt` + `node.key`).
     #[arg(long)]
-    tls_dir: PathBuf,
+    tls_dir: Option<PathBuf>,
-    /// Cargo profile — passed to cargo AND used in the fingerprint.
+    /// Cargo profile (overrides config).
-    #[arg(long, default_value = "dev")]
+    #[arg(long)]
-    profile: String,
+    profile: Option<String>,
-    /// Enabled features — passed to cargo AND used in the fingerprint.
+    /// Enabled features (overrides config).
     #[arg(long, num_args = 0.., value_delimiter = ',')]
-    features: Vec<String>,
+    features: Option<Vec<String>>,
     /// Workspace root. Defaults to the current directory.
     #[arg(long)]
     workspace: Option<PathBuf>,
+}
+
+/// Args for the local-only `fingerprint` subcommand.
+#[derive(clap::Args, Debug, Clone)]
+struct LocalArgs {
+    #[arg(long)]
+    profile: Option<String>,
+    #[arg(long, num_args = 0.., value_delimiter = ',')]
+    features: Option<Vec<String>>,
+    #[arg(long)]
+    workspace: Option<PathBuf>,
+}
+
+/// `build` gets peer args + a couple extras.
+#[derive(clap::Args, Debug, Clone)]
+struct BuildArgs {
+    #[command(flatten)]
+    peer: PeerArgs,
     /// Skip capture + upload on a miss. Useful for read-only cache use.
     #[arg(long)]
     no_upload: bool,
-    /// Extra args passed verbatim to `cargo build`.
+    /// Extra args passed verbatim to `cargo build` (after `--`).
     #[arg(last = true)]
     cargo_args: Vec<String>,
 }
@@ -110,107 +131,257 @@ async fn main() -> Result<()> {
     let cli = Cli::parse();
     match cli.cmd {
         Cmd::Build(args) => cmd_build(args).await,
-        Cmd::Fingerprint {
+        Cmd::Prefetch(args) => cmd_prefetch(args).await,
-            profile,
+        Cmd::Status(args) => cmd_status(args).await,
-            features,
+        Cmd::Fingerprint(args) => cmd_fingerprint(args),
-            workspace,
-        } => cmd_fingerprint(profile, features, workspace),
     }
 }
 
-fn cmd_fingerprint(
+/// Common setup shared by every subcommand: figure out the workspace,
-    profile: String,
+/// load layered config, resolve CLI overrides, compute the fingerprint.
-    features: Vec<String>,
+fn setup_local(
-    workspace: Option<PathBuf>,
+    workspace_arg: Option<PathBuf>,
-) -> Result<()> {
+    profile_arg: Option<String>,
-    let workspace =
+    features_arg: Option<Vec<String>>,
-        workspace.unwrap_or_else(|| std::env::current_dir().expect("cwd"));
+) -> Result<(PathBuf, ResolvedClientConfig, Fingerprint)> {
+    let workspace = workspace_arg
+        .clone()
+        .unwrap_or_else(|| std::env::current_dir().expect("cwd"));
+    let layered = ClientConfig::load_layered(&workspace)?;
+    let resolved = ResolvedClientConfig::resolve(
+        layered,
+        None,           // peer_name
+        None,           // peer_addr
+        None,           // tls_dir
+        profile_arg,
+        features_arg,
+        "dev",
+    );
     let (_inputs, fp) =
-        compute_workspace_fingerprint(&workspace, &profile, &features)?;
+        compute_workspace_fingerprint(&workspace, &resolved.profile, &resolved.features)?;
+    Ok((workspace, resolved, fp))
+}
+
+/// Full setup for a peer-touching subcommand. Resolves peer settings
+/// too and validates they're all present.
+fn setup_peer(peer_args: &PeerArgs) -> Result<(PathBuf, ResolvedClientConfig, Fingerprint)> {
+    let workspace = peer_args
+        .workspace
+        .clone()
+        .unwrap_or_else(|| std::env::current_dir().expect("cwd"));
+    let layered = ClientConfig::load_layered(&workspace)?;
+    let resolved = ResolvedClientConfig::resolve(
+        layered,
+        peer_args.peer.clone(),
+        peer_args.peer_addr,
+        peer_args.tls_dir.clone(),
+        peer_args.profile.clone(),
+        peer_args.features.clone(),
+        "dev",
+    );
+    let (_inputs, fp) =
+        compute_workspace_fingerprint(&workspace, &resolved.profile, &resolved.features)?;
+    Ok((workspace, resolved, fp))
+}
+
+/// Open a QUIC connection to the resolved peer. Returns
+/// `(client, connection)` — client stays alive so callers can shut down.
+async fn connect_peer(cfg: &ResolvedClientConfig) -> Result<(QuicClient, quinn::Connection)> {
+    let (peer_name, peer_addr, tls_dir) = cfg.require_peer_bundle()?;
+    let identity = NodeIdentity::from_pem_dir(tls_dir)
+        .with_context(|| format!("loading node identity from {}", tls_dir.display()))?;
+    let client = QuicClient::new("0.0.0.0:0".parse()?, identity)?;
+    let conn = client
+        .connect(peer_addr, peer_name)
+        .await
+        .with_context(|| format!("connecting to {peer_name} @ {peer_addr}"))?;
+    Ok((client, conn))
+}
+
+/// Ask the peer for the BlobId keyed by our fingerprint. Returns
+/// (BlobId, Option<BlobStat>) — the second is present when the
+/// referenced blob actually exists (a ref could point at a
+/// garbage-collected blob).
+async fn peer_lookup(
+    conn: &quinn::Connection,
+    fp: &Fingerprint,
+) -> Result<Option<(BlobId, crate::cluster::blob::BlobStat)>> {
+    let key = *fp.as_bytes();
+    let value_bytes = match call_get_ref(conn, &key).await? {
+        Some(v) => v,
+        None => return Ok(None),
+    };
+    let blob_id = BlobId::from_bytes(value_bytes);
+    match call_blob_stat(conn, &blob_id).await? {
+        Some(stat) => Ok(Some((blob_id, stat))),
+        None => {
+            // Ref points at a missing blob — treat as miss so
+            // build+upload will re-populate.
+            tracing::warn!(
+                "ref pointed at blob {} but peer has no such blob; treating as miss",
+                blob_id
+            );
+            Ok(None)
+        }
+    }
+}
+
+// ── fingerprint ──────────────────────────────────────────────────────
+
+fn cmd_fingerprint(args: LocalArgs) -> Result<()> {
+    let (workspace, resolved, fp) =
+        setup_local(args.workspace, args.profile, args.features)?;
     println!("workspace:   {}", workspace.display());
-    println!("profile:     {}", profile);
+    println!("profile:     {}", resolved.profile);
-    println!("features:    {}", features.join(","));
+    println!("features:    {}", resolved.features.join(","));
     println!("fingerprint: {}", fp);
     Ok(())
 }
 
-async fn cmd_build(args: BuildArgs) -> Result<()> {
+// ── status ───────────────────────────────────────────────────────────
-    let workspace = args
-        .workspace
-        .clone()
-        .unwrap_or_else(|| std::env::current_dir().expect("cwd"));
-    let target_dir = workspace.join("target").join(&args.profile);
 
-    // ── 1. Fingerprint ────────────────────────────────────────────
+async fn cmd_status(args: PeerArgs) -> Result<()> {
-    let (_inputs, fingerprint) =
+    let (workspace, resolved, fp) = setup_peer(&args)?;
-        compute_workspace_fingerprint(&workspace, &args.profile, &args.features)
+    let (peer_name, peer_addr, tls_dir) = resolved.require_peer_bundle()?;
-            .context("computing workspace fingerprint")?;
-    tracing::info!("fingerprint {}", fingerprint);
 
-    // ── 2. Connect to peer ────────────────────────────────────────
+    println!("workspace:   {}", workspace.display());
-    let identity = NodeIdentity::from_pem_dir(&args.tls_dir).with_context(|| {
+    println!("profile:     {}", resolved.profile);
-        format!("loading node identity from {}", args.tls_dir.display())
+    println!("features:    {}", resolved.features.join(","));
-    })?;
+    println!("fingerprint: {}", fp);
-    let client = QuicClient::new("0.0.0.0:0".parse()?, identity)?;
+    println!("peer:        {peer_name} @ {peer_addr}");
-    let conn = client.connect(args.peer_addr, &args.peer).await?;
+    println!("tls:         {}", tls_dir.display());
 
-    // ── 3. Cache lookup ───────────────────────────────────────────
+    let (client, conn) = connect_peer(&resolved).await?;
-    let key = *fingerprint.as_bytes();
+    match peer_lookup(&conn, &fp).await? {
-    let mut outcome = CacheOutcome::Miss;
+        Some((blob_id, stat)) => {
-    match call_get_ref(&conn, &key).await? {
+            println!("cache:       HIT");
-        Some(value_bytes) => {
+            println!("  blob:      {}", blob_id);
-            let blob_id = BlobId::from_bytes(value_bytes);
+            println!("  size:      {} bytes ({} chunks)", stat.total_size, stat.chunk_count);
-            tracing::info!("cache HIT — blob {}", blob_id);
+        }
-            match call_blob_stat(&conn, &blob_id).await? {
+        None => {
-                Some(stat) => {
+            println!("cache:       MISS");
-                    tracing::info!(
+        }
-                        "downloading cached target ({} chunks, {} bytes) → {}",
+    }
-                        stat.chunk_count,
+    conn.close(quinn::VarInt::from_u32(0), b"done");
-                        stat.total_size,
+    client.shutdown().await;
-                        target_dir.display()
+    Ok(())
-                    );
+}
-                    let mut buf = Vec::with_capacity(stat.total_size as usize);
+
-                    let ok = call_blob_get_stream(&conn, &blob_id, &mut buf).await?;
+// ── prefetch ─────────────────────────────────────────────────────────
-                    if !ok {
+
-                        tracing::warn!(
+async fn cmd_prefetch(args: PeerArgs) -> Result<()> {
-                            "ref pointed at blob {} but peer returned NotFound; falling through",
+    let (workspace, resolved, fp) = setup_peer(&args)?;
-                            blob_id
+    let target_dir = workspace.join("target").join(&resolved.profile);
-                        );
+
-                    } else {
+    let (client, conn) = connect_peer(&resolved).await?;
-                        std::fs::create_dir_all(&target_dir).with_context(|| {
+    let outcome = match peer_lookup(&conn, &fp).await? {
-                            format!("creating {}", target_dir.display())
+        Some((blob_id, stat)) => {
-                        })?;
+            println!(
-                        restore_target(&buf, &target_dir)
+                "cache HIT — downloading {} bytes ({} chunks) to {}",
-                            .context("restoring cached target dir")?;
+                stat.total_size,
-                        outcome = CacheOutcome::Hit {
+                stat.chunk_count,
-                            blob_id,
+                target_dir.display()
-                            downloaded_bytes: buf.len() as u64,
+            );
-                        };
+            let start = Instant::now();
-                    }
+            let mut buf = Vec::with_capacity(stat.total_size as usize);
-                }
+            let ok = call_blob_get_stream(&conn, &blob_id, &mut buf).await?;
-                None => {
+            if !ok {
-                    tracing::warn!(
+                println!("cache: MISS (ref pointed at a missing blob)");
-                        "ref pointed at blob {} but peer has no such blob; falling through",
+                PrefetchOutcome::Miss
-                        blob_id
+            } else {
-                    );
+                std::fs::create_dir_all(&target_dir)
+                    .with_context(|| format!("creating {}", target_dir.display()))?;
+                restore_target(&buf, &target_dir).context("restoring target dir")?;
+                PrefetchOutcome::Hit {
+                    blob_id,
+                    bytes: buf.len() as u64,
+                    elapsed: start.elapsed(),
                 }
             }
         }
         None => {
-            tracing::info!("cache MISS — no ref for fingerprint");
+            println!("cache: MISS (no ref for fingerprint)");
+            PrefetchOutcome::Miss
+        }
+    };
+    conn.close(quinn::VarInt::from_u32(0), b"done");
+    client.shutdown().await;
+
+    match outcome {
+        PrefetchOutcome::Hit {
+            blob_id,
+            bytes,
+            elapsed,
+        } => {
+            println!();
+            println!("── claw-cargo prefetch ─────────────────────────────");
+            println!("fingerprint: {}", fp);
+            println!("blob:        {}", blob_id);
+            println!("downloaded:  {} bytes in {:?}", bytes, elapsed);
+            println!("restored to: {}", target_dir.display());
+            println!("────────────────────────────────────────────────────");
+        }
+        PrefetchOutcome::Miss => {
+            println!();
+            println!("fingerprint: {} — no cache to prefetch", fp);
         }
     }
+    Ok(())
+}
 
-    // ── 4. Run cargo ──────────────────────────────────────────────
+enum PrefetchOutcome {
+    Hit {
+        blob_id: BlobId,
+        bytes: u64,
+        elapsed: std::time::Duration,
+    },
+    Miss,
+}
+
+// ── build ────────────────────────────────────────────────────────────
+
+async fn cmd_build(args: BuildArgs) -> Result<()> {
+    let (workspace, resolved, fp) = setup_peer(&args.peer)?;
+    let target_dir = workspace.join("target").join(&resolved.profile);
+    tracing::info!("fingerprint {}", fp);
+
+    let (client, conn) = connect_peer(&resolved).await?;
+
+    let mut outcome = CacheOutcome::Miss;
+    match peer_lookup(&conn, &fp).await? {
+        Some((blob_id, stat)) => {
+            tracing::info!("cache HIT — blob {} ({} bytes)", blob_id, stat.total_size);
+            let mut buf = Vec::with_capacity(stat.total_size as usize);
+            let ok = call_blob_get_stream(&conn, &blob_id, &mut buf).await?;
+            if ok {
+                std::fs::create_dir_all(&target_dir).with_context(|| {
+                    format!("creating {}", target_dir.display())
+                })?;
+                restore_target(&buf, &target_dir).context("restoring cached target dir")?;
+                outcome = CacheOutcome::Hit {
+                    blob_id,
+                    downloaded_bytes: buf.len() as u64,
+                };
+            }
+        }
+        None => tracing::info!("cache MISS"),
+    }
+
+    // Run cargo. Even on hit we run cargo — the workspace's own crates
+    // still need to be compiled; the cache only shortcuts the deps.
     let cargo_started = Instant::now();
-    let cargo_status = run_cargo(&workspace, &args.profile, &args.features, &args.cargo_args)?;
+    let cargo_status = run_cargo(
+        &workspace,
+        &resolved.profile,
+        &resolved.features,
+        &args.cargo_args,
+    )?;
     let cargo_elapsed = cargo_started.elapsed();
     if !cargo_status.success() {
-        bail!("cargo build failed with exit {}", cargo_status);
+        anyhow::bail!("cargo build failed with exit {}", cargo_status);
     }
     tracing::info!("cargo build finished in {:?}", cargo_elapsed);
 
-    // ── 5. On miss, capture + upload ──────────────────────────────
     if matches!(outcome, CacheOutcome::Miss) && !args.no_upload {
         if !target_dir.is_dir() {
             tracing::warn!(
@@ -218,28 +389,11 @@ async fn cmd_build(args: BuildArgs) -> Result<()> {
                 target_dir.display()
             );
         } else {
-            let capture_started = Instant::now();
             let bytes = capture_target(&target_dir).context("capturing target dir")?;
-            let capture_elapsed = capture_started.elapsed();
-            tracing::info!(
-                "captured target: {} bytes in {:?}",
-                bytes.len(),
-                capture_elapsed
-            );
-
-            let upload_started = Instant::now();
             let cursor = std::io::Cursor::new(bytes.clone());
             let blob_id = call_blob_put_stream(&conn, cursor).await?;
-            let upload_elapsed = upload_started.elapsed();
+            call_put_ref(&conn, fp.as_bytes(), blob_id.as_bytes()).await?;
-            tracing::info!(
+            tracing::info!("uploaded blob {} + set ref", blob_id);
-                "uploaded blob {} in {:?}",
-                blob_id,
-                upload_elapsed
-            );
-
-            call_put_ref(&conn, &key, blob_id.as_bytes()).await?;
-            tracing::info!("set ref {} → {}", fingerprint, blob_id);
-
             outcome = CacheOutcome::Populated {
                 blob_id,
                 uploaded_bytes: bytes.len() as u64,
@@ -247,15 +401,13 @@ async fn cmd_build(args: BuildArgs) -> Result<()> {
         }
     }
 
-    // ── 6. Shutdown + summary ─────────────────────────────────────
     conn.close(quinn::VarInt::from_u32(0), b"done");
     client.shutdown().await;
 
-    print_summary(&fingerprint, &outcome, cargo_elapsed);
+    print_summary(&fp, &outcome, cargo_elapsed);
     Ok(())
 }
 
-/// Outcome of the cache lookup + build cycle. Reported at end-of-run.
 enum CacheOutcome {
     Hit {
         blob_id: BlobId,
@@ -298,10 +450,8 @@ fn print_summary(fp: &Fingerprint, outcome: &CacheOutcome, cargo_elapsed: std::t
     println!("────────────────────────────────────────────────────");
 }
 
-/// Invoke `cargo build` with the same profile/features + any passthrough
-/// args the caller supplied. Runs to completion, returns the exit status.
 fn run_cargo(
-    workspace: &std::path::Path,
+    workspace: &Path,
     profile: &str,
     features: &[String],
     passthrough: &[String],

claw-store/src/cluster.rs

@@ -16,6 +16,7 @@
 
 pub mod blob;
 pub mod build_cache;
+pub mod client_config;
 pub mod gossip;
 pub mod refs;
 pub mod rpc;

claw-store/src/cluster/client_config.rs

@@ -0,0 +1,496 @@
+//! Client-side config for `claw-cargo` and any future peer-facing
+//! tools (Phase 5c).
+//!
+//! Layered defaults:
+//!   1. Built-in defaults (empty struct).
+//!   2. `~/.claw-cargo/config.toml` if present.
+//!   3. `<workspace>/.claw-cargo.toml` if present.
+//!   4. CLI overrides.
+//!
+//! Every field is optional at every layer; the final merged
+//! [`ResolvedClientConfig`] validates that the fields it needs are
+//! actually set before running an operation that requires them.
+
+use anyhow::{bail, Context, Result};
+use serde::{Deserialize, Serialize};
+use std::net::SocketAddr;
+use std::path::{Path, PathBuf};
+
+/// Location of a per-user config file: `<home>/.claw-cargo/config.toml`.
+pub fn user_config_path() -> Option<PathBuf> {
+    std::env::var_os("HOME")
+        .map(PathBuf::from)
+        .map(|h| h.join(".claw-cargo").join("config.toml"))
+}
+
+/// Location of a workspace-level config file: `<workspace>/.claw-cargo.toml`.
+pub fn workspace_config_path(workspace: &Path) -> PathBuf {
+    workspace.join(".claw-cargo.toml")
+}
+
+/// TOML-serialisable config. Every field optional; layers merge with
+/// later-wins semantics on `Option::or`.
+#[derive(Debug, Clone, Default, PartialEq, Serialize, Deserialize)]
+pub struct ClientConfig {
+    #[serde(default)]
+    pub peer: Option<PeerSection>,
+    #[serde(default)]
+    pub build: Option<BuildSection>,
+}
+
+#[derive(Debug, Clone, Default, PartialEq, Serialize, Deserialize)]
+pub struct PeerSection {
+    /// Peer's node name — must match the peer's leaf cert SAN.
+    #[serde(default)]
+    pub name: Option<String>,
+    /// Peer's RPC socket (gossip_port + 1 typically).
+    #[serde(default)]
+    pub addr: Option<SocketAddr>,
+    /// Directory holding this node's mTLS material
+    /// (`ca.crt` + `node.crt` + `node.key`).
+    #[serde(default)]
+    pub tls_dir: Option<PathBuf>,
+}
+
+#[derive(Debug, Clone, Default, PartialEq, Serialize, Deserialize)]
+pub struct BuildSection {
+    #[serde(default)]
+    pub profile: Option<String>,
+    #[serde(default)]
+    pub features: Option<Vec<String>>,
+}
+
+impl ClientConfig {
+    /// Parse TOML from a string. Errors on syntactic problems, not on
+    /// missing fields (those get None).
+    pub fn from_toml_str(s: &str) -> Result<Self> {
+        toml::from_str(s).context("parsing client config TOML")
+    }
+
+    /// Read a file. Returns default (all-None) when the file doesn't
+    /// exist, so callers can chain multiple loads unconditionally.
+    pub fn from_file_or_default(path: &Path) -> Result<Self> {
+        match std::fs::read_to_string(path) {
+            Ok(s) => Self::from_toml_str(&s)
+                .with_context(|| format!("reading client config at {}", path.display())),
+            Err(e) if e.kind() == std::io::ErrorKind::NotFound => Ok(Self::default()),
+            Err(e) => Err(anyhow::Error::from(e))
+                .with_context(|| format!("reading client config at {}", path.display())),
+        }
+    }
+
+    /// Merge `other` on top of `self`: any field set in `other` wins;
+    /// unset fields fall through to `self`. In-place — mutates `self`.
+    pub fn merge(&mut self, other: ClientConfig) {
+        if let Some(o_peer) = other.peer {
+            let p = self.peer.get_or_insert_with(PeerSection::default);
+            if o_peer.name.is_some() {
+                p.name = o_peer.name;
+            }
+            if o_peer.addr.is_some() {
+                p.addr = o_peer.addr;
+            }
+            if o_peer.tls_dir.is_some() {
+                p.tls_dir = o_peer.tls_dir;
+            }
+        }
+        if let Some(o_build) = other.build {
+            let b = self.build.get_or_insert_with(BuildSection::default);
+            if o_build.profile.is_some() {
+                b.profile = o_build.profile;
+            }
+            if o_build.features.is_some() {
+                b.features = o_build.features;
+            }
+        }
+    }
+
+    /// Standard load: user config < workspace config. Missing files
+    /// treated as empty. Doesn't apply CLI overrides — the caller
+    /// merges those in last so the semantics stay tidy.
+    pub fn load_layered(workspace: &Path) -> Result<Self> {
+        let mut cfg = ClientConfig::default();
+        if let Some(user_path) = user_config_path() {
+            let user = ClientConfig::from_file_or_default(&user_path)?;
+            cfg.merge(user);
+        }
+        let workspace_cfg =
+            ClientConfig::from_file_or_default(&workspace_config_path(workspace))?;
+        cfg.merge(workspace_cfg);
+        Ok(cfg)
+    }
+}
+
+/// A ClientConfig plus the CLI-supplied overrides, resolved against
+/// each other into concrete-final-values with validation. Every field
+/// that is required for a subcommand to run is `Result`-checked via
+/// the `require_*` helpers so the caller gets a specific error message
+/// instead of "some Option was None".
+#[derive(Debug, Clone, PartialEq)]
+pub struct ResolvedClientConfig {
+    pub peer_name: Option<String>,
+    pub peer_addr: Option<SocketAddr>,
+    pub tls_dir: Option<PathBuf>,
+    pub profile: String,
+    pub features: Vec<String>,
+}
+
+impl ResolvedClientConfig {
+    /// Apply CLI overrides (Option::Some wins) on top of the layered
+    /// config and produce the final resolved shape. `default_profile`
+    /// is the process default when nothing is set anywhere (`"dev"`
+    /// per cargo convention).
+    pub fn resolve(
+        layered: ClientConfig,
+        cli_peer_name: Option<String>,
+        cli_peer_addr: Option<SocketAddr>,
+        cli_tls_dir: Option<PathBuf>,
+        cli_profile: Option<String>,
+        cli_features: Option<Vec<String>>,
+        default_profile: &str,
+    ) -> Self {
+        let (peer_name, peer_addr, tls_dir) = match layered.peer {
+            Some(p) => (
+                cli_peer_name.or(p.name),
+                cli_peer_addr.or(p.addr),
+                cli_tls_dir.or(p.tls_dir),
+            ),
+            None => (cli_peer_name, cli_peer_addr, cli_tls_dir),
+        };
+        let (profile, features) = match layered.build {
+            Some(b) => (
+                cli_profile
+                    .or(b.profile)
+                    .unwrap_or_else(|| default_profile.to_string()),
+                cli_features.or(b.features).unwrap_or_default(),
+            ),
+            None => (
+                cli_profile.unwrap_or_else(|| default_profile.to_string()),
+                cli_features.unwrap_or_default(),
+            ),
+        };
+        Self {
+            peer_name,
+            peer_addr,
+            tls_dir,
+            profile,
+            features,
+        }
+    }
+
+    pub fn require_peer_name(&self) -> Result<&str> {
+        self.peer_name
+            .as_deref()
+            .context("peer.name not set (config file or --peer)")
+    }
+
+    pub fn require_peer_addr(&self) -> Result<SocketAddr> {
+        self.peer_addr
+            .context("peer.addr not set (config file or --peer-addr)")
+    }
+
+    pub fn require_tls_dir(&self) -> Result<&Path> {
+        self.tls_dir
+            .as_deref()
+            .context("peer.tls_dir not set (config file or --tls-dir)")
+    }
+
+    /// Bundled "everything a build/prefetch/status needs" check.
+    pub fn require_peer_bundle(&self) -> Result<(&str, SocketAddr, &Path)> {
+        let name = self.require_peer_name()?;
+        let addr = self.require_peer_addr()?;
+        let tls = self.require_tls_dir()?;
+        Ok((name, addr, tls))
+    }
+}
+
+/// Save the given `cfg` to `path`. Creates parent dirs if needed.
+/// Used by an eventual `claw-cargo config write` helper — currently
+/// consumed by tests but public so integration callers can seed a
+/// config in a tempdir.
+pub fn write_config_file(path: &Path, cfg: &ClientConfig) -> Result<()> {
+    if let Some(parent) = path.parent() {
+        std::fs::create_dir_all(parent)
+            .with_context(|| format!("creating config dir {}", parent.display()))?;
+    }
+    let s = toml::to_string_pretty(cfg).context("serialising client config to TOML")?;
+    std::fs::write(path, s)
+        .with_context(|| format!("writing client config to {}", path.display()))?;
+    Ok(())
+}
+
+/// Sanity: refuse to run a peer operation when the resolved config
+/// leaves any of `peer_name` / `peer_addr` / `tls_dir` unset.
+pub fn validate_peer(cfg: &ResolvedClientConfig) -> Result<()> {
+    if cfg.peer_name.is_none() || cfg.peer_addr.is_none() || cfg.tls_dir.is_none() {
+        bail!(
+            "peer settings incomplete: name={:?} addr={:?} tls_dir={:?} \
+             (set via config file or CLI flags)",
+            cfg.peer_name,
+            cfg.peer_addr,
+            cfg.tls_dir
+        );
+    }
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn from_toml_str_parses_full_config() {
+        let s = r#"
+[peer]
+name = "tank"
+addr = "10.0.0.14:7702"
+tls_dir = "/etc/claw-store/tls"
+
+[build]
+profile = "release"
+features = ["a", "b"]
+"#;
+        let cfg = ClientConfig::from_toml_str(s).unwrap();
+        let peer = cfg.peer.unwrap();
+        assert_eq!(peer.name.unwrap(), "tank");
+        assert_eq!(
+            peer.addr.unwrap(),
+            "10.0.0.14:7702".parse::<SocketAddr>().unwrap()
+        );
+        assert_eq!(peer.tls_dir.unwrap(), PathBuf::from("/etc/claw-store/tls"));
+        let build = cfg.build.unwrap();
+        assert_eq!(build.profile.unwrap(), "release");
+        assert_eq!(build.features.unwrap(), vec!["a", "b"]);
+    }
+
+    #[test]
+    fn from_toml_str_handles_partial_sections() {
+        // Only peer.name — should parse fine with everything else None.
+        let s = r#"
+[peer]
+name = "tank"
+"#;
+        let cfg = ClientConfig::from_toml_str(s).unwrap();
+        let peer = cfg.peer.unwrap();
+        assert_eq!(peer.name.unwrap(), "tank");
+        assert!(peer.addr.is_none());
+        assert!(peer.tls_dir.is_none());
+        assert!(cfg.build.is_none());
+    }
+
+    #[test]
+    fn from_file_or_default_returns_default_when_missing() {
+        let tmp = tempfile::TempDir::new().unwrap();
+        let cfg =
+            ClientConfig::from_file_or_default(&tmp.path().join("does-not-exist")).unwrap();
+        assert_eq!(cfg, ClientConfig::default());
+    }
+
+    #[test]
+    fn merge_prefers_later_over_earlier() {
+        let mut base = ClientConfig::from_toml_str(
+            r#"
+[peer]
+name = "tank"
+addr = "10.0.0.14:7702"
+tls_dir = "/etc/tls"
+
+[build]
+profile = "dev"
+features = ["a"]
+"#,
+        )
+        .unwrap();
+        let workspace = ClientConfig::from_toml_str(
+            r#"
+[peer]
+name = "architect"
+
+[build]
+profile = "release"
+"#,
+        )
+        .unwrap();
+        base.merge(workspace);
+        let peer = base.peer.unwrap();
+        assert_eq!(peer.name.unwrap(), "architect", "later config wins");
+        assert_eq!(
+            peer.addr.unwrap(),
+            "10.0.0.14:7702".parse::<SocketAddr>().unwrap(),
+            "unset field falls through"
+        );
+        assert_eq!(peer.tls_dir.unwrap(), PathBuf::from("/etc/tls"));
+        let build = base.build.unwrap();
+        assert_eq!(build.profile.unwrap(), "release");
+        assert_eq!(build.features.unwrap(), vec!["a"], "features fall through");
+    }
+
+    #[test]
+    fn resolve_applies_cli_overrides_over_layered() {
+        let layered = ClientConfig::from_toml_str(
+            r#"
+[peer]
+name = "tank"
+addr = "10.0.0.14:7702"
+tls_dir = "/etc/tls"
+
+[build]
+profile = "dev"
+features = ["a", "b"]
+"#,
+        )
+        .unwrap();
+        let resolved = ResolvedClientConfig::resolve(
+            layered,
+            Some("architect".into()),      // override
+            None,                           // fall through
+            None,                           // fall through
+            Some("release".into()),         // override
+            None,                           // fall through
+            "dev",
+        );
+        assert_eq!(resolved.peer_name.unwrap(), "architect");
+        assert_eq!(
+            resolved.peer_addr.unwrap(),
+            "10.0.0.14:7702".parse::<SocketAddr>().unwrap()
+        );
+        assert_eq!(resolved.tls_dir.unwrap(), PathBuf::from("/etc/tls"));
+        assert_eq!(resolved.profile, "release");
+        assert_eq!(resolved.features, vec!["a", "b"]);
+    }
+
+    #[test]
+    fn resolve_falls_through_to_default_profile_when_unset_everywhere() {
+        let resolved = ResolvedClientConfig::resolve(
+            ClientConfig::default(),
+            None,
+            None,
+            None,
+            None,
+            None,
+            "dev",
+        );
+        assert_eq!(resolved.profile, "dev");
+        assert!(resolved.features.is_empty());
+        assert!(resolved.peer_name.is_none());
+    }
+
+    #[test]
+    fn require_peer_bundle_errors_when_incomplete() {
+        let resolved = ResolvedClientConfig {
+            peer_name: Some("tank".into()),
+            peer_addr: None, // missing
+            tls_dir: Some("/etc/tls".into()),
+            profile: "dev".into(),
+            features: vec![],
+        };
+        let err = resolved.require_peer_bundle().unwrap_err().to_string();
+        assert!(err.contains("peer.addr"), "unexpected: {err}");
+    }
+
+    #[test]
+    fn validate_peer_errors_on_missing_field() {
+        let resolved = ResolvedClientConfig {
+            peer_name: Some("tank".into()),
+            peer_addr: Some("10.0.0.14:7702".parse().unwrap()),
+            tls_dir: None,
+            profile: "dev".into(),
+            features: vec![],
+        };
+        let err = validate_peer(&resolved).unwrap_err().to_string();
+        assert!(err.contains("peer settings incomplete"), "unexpected: {err}");
+    }
+
+    #[test]
+    fn load_layered_reads_both_files() {
+        // Fake HOME → tmp/user; workspace at tmp/ws. Both files exist.
+        let tmp = tempfile::TempDir::new().unwrap();
+        let user_home = tmp.path().join("user_home");
+        let workspace = tmp.path().join("ws");
+        std::fs::create_dir_all(&workspace).unwrap();
+
+        // User config: sets everything.
+        let user_cfg = ClientConfig::from_toml_str(
+            r#"
+[peer]
+name = "tank"
+addr = "10.0.0.14:7702"
+tls_dir = "/user/tls"
+
+[build]
+profile = "dev"
+"#,
+        )
+        .unwrap();
+        write_config_file(
+            &user_home.join(".claw-cargo").join("config.toml"),
+            &user_cfg,
+        )
+        .unwrap();
+
+        // Workspace config overrides profile only.
+        let ws_cfg = ClientConfig::from_toml_str(
+            r#"
+[build]
+profile = "release"
+"#,
+        )
+        .unwrap();
+        write_config_file(&workspace.join(".claw-cargo.toml"), &ws_cfg).unwrap();
+
+        // Point HOME at our fake home so user_config_path picks it up.
+        // std::env::set_var is process-global; save/restore the prior
+        // value to keep the test hermetic.
+        let saved = std::env::var_os("HOME");
+        std::env::set_var("HOME", &user_home);
+        let cfg = ClientConfig::load_layered(&workspace).unwrap();
+        match saved {
+            Some(v) => std::env::set_var("HOME", v),
+            None => std::env::remove_var("HOME"),
+        }
+
+        let peer = cfg.peer.unwrap();
+        assert_eq!(peer.name.unwrap(), "tank", "user config peer name survives");
+        assert_eq!(
+            peer.addr.unwrap(),
+            "10.0.0.14:7702".parse::<SocketAddr>().unwrap()
+        );
+        let build = cfg.build.unwrap();
+        assert_eq!(
+            build.profile.unwrap(),
+            "release",
+            "workspace config overrode user profile"
+        );
+    }
+
+    #[test]
+    fn user_config_path_uses_home() {
+        let saved = std::env::var_os("HOME");
+        std::env::set_var("HOME", "/tmp/test-home");
+        let path = user_config_path().unwrap();
+        assert_eq!(path, PathBuf::from("/tmp/test-home/.claw-cargo/config.toml"));
+        match saved {
+            Some(v) => std::env::set_var("HOME", v),
+            None => std::env::remove_var("HOME"),
+        }
+    }
+
+    #[test]
+    fn write_and_read_round_trip_via_disk() {
+        let tmp = tempfile::TempDir::new().unwrap();
+        let path = tmp.path().join("nested").join("dir").join("config.toml");
+        let cfg = ClientConfig::from_toml_str(
+            r#"
+[peer]
+name = "tank"
+addr = "10.0.0.14:7702"
+tls_dir = "/etc/tls"
+"#,
+        )
+        .unwrap();
+        write_config_file(&path, &cfg).unwrap();
+        assert!(path.exists());
+        let round = ClientConfig::from_file_or_default(&path).unwrap();
+        assert_eq!(round, cfg);
+    }
+}