diff --git a/.claude/settings.json b/.claude/settings.json
index 0a4eaef..64de6ec 100644
--- a/.claude/settings.json
+++ b/.claude/settings.json
@@ -1,5 +1,15 @@
 {
   "hooks": {
+    "SessionStart": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "nu /Users/joe/dev/notfiles/scripts/preflight.nu"
+          }
+        ]
+      }
+    ],
     "PostToolUse": [
       {
         "matcher": "Edit|Write",
diff --git a/.claude/worktrees/agent-a0b9834e b/.claude/worktrees/agent-a0b9834e
new file mode 160000
index 0000000..11d329c
--- /dev/null
+++ b/.claude/worktrees/agent-a0b9834e
@@ -0,0 +1 @@
+Subproject commit 11d329c5a2a2df0c785dfcf3025fc52828923ff0
diff --git a/.claude/worktrees/agent-a27fe5f2 b/.claude/worktrees/agent-a27fe5f2
new file mode 160000
index 0000000..11d329c
--- /dev/null
+++ b/.claude/worktrees/agent-a27fe5f2
@@ -0,0 +1 @@
+Subproject commit 11d329c5a2a2df0c785dfcf3025fc52828923ff0
diff --git a/.claude/worktrees/agent-a6b81d3b b/.claude/worktrees/agent-a6b81d3b
new file mode 160000
index 0000000..11d329c
--- /dev/null
+++ b/.claude/worktrees/agent-a6b81d3b
@@ -0,0 +1 @@
+Subproject commit 11d329c5a2a2df0c785dfcf3025fc52828923ff0
diff --git a/.claude/worktrees/agent-af9e1ed8 b/.claude/worktrees/agent-af9e1ed8
new file mode 160000
index 0000000..11d329c
--- /dev/null
+++ b/.claude/worktrees/agent-af9e1ed8
@@ -0,0 +1 @@
+Subproject commit 11d329c5a2a2df0c785dfcf3025fc52828923ff0
diff --git a/crates/notfiles/src/linker.rs b/crates/notfiles/src/linker.rs
index a08b6d1..2dc68ae 100644
--- a/crates/notfiles/src/linker.rs
+++ b/crates/notfiles/src/linker.rs
@@ -95,7 +95,7 @@ pub fn link_package(
         let target = target_base.join(relative);
         let source_display = format!("{package}/{}", relative.display());
 
-        // Check if already correctly linked
+        // Check if already correctly linked / copied
         if is_already_linked(&source, &target, method) {
             if opts.verbose {
                 println!("  \x1b[90mskip\x1b[0m {source_display} (already linked)");
@@ -103,15 +103,26 @@ pub fn link_package(
             continue;
         }
 
+        // Helper: save partial state then return an error.
+        let save_and_return = |state: &mut State, e: NotfilesError| -> Result<(), NotfilesError> {
+            if !opts.dry_run {
+                let _ = state.save(dotfiles_dir);
+            }
+            Err(e)
+        };
+
         // Conflict detection
         if target.exists() || target.symlink_metadata().is_ok() {
             if !opts.force {
-                return Err(NotfilesError::Conflict {
-                    path: target.clone(),
-                    reason: format!(
-                        "already exists (use --force to overwrite); source: {source_display}"
-                    ),
-                });
+                return save_and_return(
+                    state,
+                    NotfilesError::Conflict {
+                        path: target.clone(),
+                        reason: format!(
+                            "already exists (use --force to overwrite); source: {source_display}"
+                        ),
+                    },
+                );
             }
             // Force mode: backup then remove
             if !opts.no_backup {
@@ -130,13 +141,18 @@ pub fn link_package(
                             backup.display()
                         );
                     }
-                    fs::rename(&target, &backup)?;
+                    if let Err(e) = fs::rename(&target, &backup) {
+                        return save_and_return(state, e.into());
+                    }
                 }
             } else if !opts.dry_run {
-                if target.is_dir() {
-                    fs::remove_dir_all(&target)?;
+                let rm_result = if target.is_dir() {
+                    fs::remove_dir_all(&target)
                 } else {
-                    fs::remove_file(&target)?;
+                    fs::remove_file(&target)
+                };
+                if let Err(e) = rm_result {
+                    return save_and_return(state, e.into());
                 }
             }
         }
@@ -147,8 +163,8 @@ pub fn link_package(
                 if opts.verbose {
                     println!("  \x1b[90mwould create dir\x1b[0m {}", parent.display());
                 }
-            } else {
-                fs::create_dir_all(parent)?;
+            } else if let Err(e) = fs::create_dir_all(parent) {
+                return save_and_return(state, e.into());
             }
         }
 
@@ -164,16 +180,21 @@ pub fn link_package(
                 target.display()
             );
         } else {
-            match method {
+            let link_result = match method {
                 Method::Symlink => {
                     #[cfg(unix)]
-                    std::os::unix::fs::symlink(&source, &target)?;
+                    {
+                        std::os::unix::fs::symlink(&source, &target).map(|_| 0u64)
+                    }
                     #[cfg(not(unix))]
-                    fs::copy(&source, &target)?;
-                }
-                Method::Copy => {
-                    fs::copy(&source, &target)?;
+                    {
+                        fs::copy(&source, &target)
+                    }
                 }
+                Method::Copy => fs::copy(&source, &target),
+            };
+            if let Err(e) = link_result {
+                return save_and_return(state, e.into());
             }
             if opts.verbose {
                 println!(
@@ -283,7 +304,15 @@ fn is_already_linked(source: &Path, target: &Path, method: Method) -> bool {
                 false
             }
         }
-        Method::Copy => false, // Always re-copy
+        Method::Copy => {
+            // Skip re-copy if target exists and has the same size and mtime as source.
+            match (fs::metadata(source), fs::metadata(target)) {
+                (Ok(sm), Ok(tm)) => {
+                    sm.len() == tm.len() && sm.modified().ok() == tm.modified().ok()
+                }
+                _ => false,
+            }
+        }
     }
 }
 
diff --git a/crates/notgraph/src/emit.rs b/crates/notgraph/src/emit.rs
index 75bc88d..3ec0446 100644
--- a/crates/notgraph/src/emit.rs
+++ b/crates/notgraph/src/emit.rs
@@ -172,19 +172,27 @@ fn write_html(
         .map(|fs| fs.name.as_str())
         .collect();
 
-    let mut leaves: Vec<&str> = crate_graph.nodes.iter()
+    let mut leaves: Vec<&str> = crate_graph
+        .nodes
+        .iter()
         .map(|n| n.as_str())
         .filter(|n| leaf_nodes.contains(n) && !root_nodes.contains(n))
         .collect();
-    let mut roots: Vec<&str> = crate_graph.nodes.iter()
+    let mut roots: Vec<&str> = crate_graph
+        .nodes
+        .iter()
         .map(|n| n.as_str())
         .filter(|n| root_nodes.contains(n) && !leaf_nodes.contains(n))
         .collect();
-    let mut features: Vec<&str> = crate_graph.nodes.iter()
+    let mut features: Vec<&str> = crate_graph
+        .nodes
+        .iter()
         .map(|n| n.as_str())
         .filter(|n| !leaf_nodes.contains(n) && !root_nodes.contains(n))
         .collect();
-    let mut isolated: Vec<&str> = crate_graph.nodes.iter()
+    let mut isolated: Vec<&str> = crate_graph
+        .nodes
+        .iter()
         .map(|n| n.as_str())
         .filter(|n| leaf_nodes.contains(n) && root_nodes.contains(n))
         .collect();
@@ -202,7 +210,11 @@ fn write_html(
         let syms = sym_count.get(n).copied().unwrap_or(0);
         format!(
             "{}[\"{}<br/>in:{} out:{} | {} pub\"]",
-            mermaid_id(n), n, fi, fo, syms
+            mermaid_id(n),
+            n,
+            fi,
+            fo,
+            syms
         )
     };
 
@@ -211,17 +223,23 @@ fn write_html(
 
     if !leaves.is_empty() {
         mermaid.push_str("  subgraph Core\n    direction TB\n");
-        for n in &leaves { mermaid.push_str(&format!("    {}\n", node_label(n))); }
+        for n in &leaves {
+            mermaid.push_str(&format!("    {}\n", node_label(n)));
+        }
         mermaid.push_str("  end\n");
     }
     if !features.is_empty() {
         mermaid.push_str("  subgraph Features\n    direction TB\n");
-        for n in &features { mermaid.push_str(&format!("    {}\n", node_label(n))); }
+        for n in &features {
+            mermaid.push_str(&format!("    {}\n", node_label(n)));
+        }
         mermaid.push_str("  end\n");
     }
     if !roots.is_empty() {
         mermaid.push_str("  subgraph Tools\n    direction TB\n");
-        for n in &roots { mermaid.push_str(&format!("    {}\n", node_label(n))); }
+        for n in &roots {
+            mermaid.push_str(&format!("    {}\n", node_label(n)));
+        }
         mermaid.push_str("  end\n");
     }
 
@@ -234,7 +252,8 @@ fn write_html(
         let color = heatmap_color(fs.fan_in);
         mermaid.push_str(&format!(
             "  style {} fill:{},stroke:#4a9eff,color:#e0e0e0\n",
-            mermaid_id(&fs.name), color
+            mermaid_id(&fs.name),
+            color
         ));
     }
 
@@ -316,10 +335,12 @@ fn write_html(
     let hotspot_rows: String = stats
         .hotspots
         .iter()
-        .map(|h| format!(
-            "<tr><td>{}</td><td>{}</td><td>{}</td></tr>",
-            h.name, h.kind, h.score
-        ))
+        .map(|h| {
+            format!(
+                "<tr><td>{}</td><td>{}</td><td>{}</td></tr>",
+                h.name, h.kind, h.score
+            )
+        })
         .collect::<Vec<_>>()
         .join("\n");
 
diff --git a/crates/notgraph/src/main.rs b/crates/notgraph/src/main.rs
index a47472a..5ba3b49 100644
--- a/crates/notgraph/src/main.rs
+++ b/crates/notgraph/src/main.rs
@@ -63,8 +63,14 @@ fn main() -> Result<()> {
         workspace_root.join(&cli.output)
     };
 
-    emit::write_all(&output_dir, &crate_g, &module_graphs, &stats, &symbol_tables)
-        .context("failed to write reports")?;
+    emit::write_all(
+        &output_dir,
+        &crate_g,
+        &module_graphs,
+        &stats,
+        &symbol_tables,
+    )
+    .context("failed to write reports")?;
 
     println!("notgraph: reports written to {}", output_dir.display());
 
diff --git a/crates/notsecrets/src/sources/bitwarden.rs b/crates/notsecrets/src/sources/bitwarden.rs
index 7006e96..ec6f4e9 100644
--- a/crates/notsecrets/src/sources/bitwarden.rs
+++ b/crates/notsecrets/src/sources/bitwarden.rs
@@ -50,15 +50,19 @@ impl BitwardenSource {
                     source: anyhow::anyhow!("bw unlock spawn: {e}"),
                 })?;
             if let Some(mut stdin) = child.stdin.take() {
-                stdin.write_all(password.as_bytes()).map_err(|e| AgeError::SourceError {
-                    name: self.name().to_string(),
-                    source: anyhow::anyhow!("bw unlock stdin write: {e}"),
-                })?;
+                stdin
+                    .write_all(password.as_bytes())
+                    .map_err(|e| AgeError::SourceError {
+                        name: self.name().to_string(),
+                        source: anyhow::anyhow!("bw unlock stdin write: {e}"),
+                    })?;
             }
-            let output = child.wait_with_output().map_err(|e| AgeError::SourceError {
-                name: self.name().to_string(),
-                source: anyhow::anyhow!("bw unlock wait: {e}"),
-            })?;
+            let output = child
+                .wait_with_output()
+                .map_err(|e| AgeError::SourceError {
+                    name: self.name().to_string(),
+                    source: anyhow::anyhow!("bw unlock wait: {e}"),
+                })?;
             if !output.status.success() {
                 return Err(AgeError::SourceError {
                     name: self.name().to_string(),
diff --git a/crates/notstrap/src/lib.rs b/crates/notstrap/src/lib.rs
index 65df8c7..42c2f63 100644
--- a/crates/notstrap/src/lib.rs
+++ b/crates/notstrap/src/lib.rs
@@ -2,6 +2,7 @@ use anyhow::{Context, Result};
 use notcore::{HookPhase, Report, StepStatus};
 use notfiles::{LinkOptions, link};
 use nothooks::{HookRunner, run_phase};
+use notsecrets::identities::Identity;
 use notsecrets::sources::IdentitySource;
 use notsecrets::{BitwardenSource, FileSource, PromptSource, resolve_identities};
 use serde::Deserialize;
@@ -10,7 +11,7 @@ use std::path::{Path, PathBuf};
 pub mod prereqs;
 pub mod repo;
 
-type EnvInjector = Box<dyn Fn(&Path) -> Result<String>>;
+type EnvInjector = Box<dyn Fn(&Path, Vec<Box<dyn Identity>>) -> Result<String>>;
 
 #[derive(Deserialize)]
 pub struct NotstrapConfig {
diff --git a/scripts/preflight.nu b/scripts/preflight.nu
new file mode 100644
index 0000000..f184fae
--- /dev/null
+++ b/scripts/preflight.nu
@@ -0,0 +1,37 @@
+#!/usr/bin/env nu
+# preflight.nu — notfiles environment validation
+
+def check [label: string, pass: bool, detail: string = ""] {
+    if $pass {
+        print $"[ok]   ($label)"
+    } else if $detail != "" {
+        print $"[fail] ($label) — ($detail)"
+    } else {
+        print $"[fail] ($label)"
+    }
+    $pass
+}
+
+print "=== notfiles preflight ==="
+
+let results = [
+    (check "cargo on PATH" (which cargo | length) > 0),
+    (check "just on PATH" (which just | length) > 0),
+    (check "nu on PATH" (which nu | length) > 0 "nushell required for hook scripts"),
+    (check "age on PATH" (which age | length) > 0 "optional — needed for SOPS decryption"),
+    (check "sops on PATH" (which sops | length) > 0 "optional — needed for encrypted configs"),
+    (check "notfiles on PATH" (which notfiles | length) > 0 "run: cargo install --path crates/notfiles"),
+    (check "op on PATH" (which op | length) > 0),
+    (check "1Password authed" (do { op account list } | complete | get exit_code) == 0),
+    (check "git repo clean" (do { git status --porcelain } | complete | get stdout | str trim | is-empty)),
+]
+
+let failed = $results | where { |r| not $r } | length
+let total = $results | length
+
+print ""
+if $failed == 0 {
+    print $"preflight passed ($total)/($total)"
+} else {
+    print $"preflight ($total - $failed)/($total) — ($failed) check(s) failed"
+}