diff --git a/Cargo.toml b/Cargo.toml
index a749884..f21c9bc 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,18 +1,13 @@
 [workspace]
-members  = [ "cognos", "rom" ]
+members = ["cognos", "rom"]
 resolver = "3"
 
 [workspace.package]
-name = "rom"
 version = "0.1.0"
 edition = "2024"
 authors = ["NotAShelf <raf@notashelf.dev>"]
 description = "Pretty build graphs for Nix builds"
-license = "MPL-2.0"
-repository = "https://github.com/notashelf/rom"
-homepage = "https://github.com/notashelf/rom"
 rust-version = "1.85"
-readme = true
 
 [workspace.dependencies]
 anyhow = "1.0.100"
diff --git a/cognos/Cargo.toml b/cognos/Cargo.toml
index 102a00d..4e0a70d 100644
--- a/cognos/Cargo.toml
+++ b/cognos/Cargo.toml
@@ -1,9 +1,9 @@
 [package]
 name = "cognos"
 description = "Minimalistic parser for Nix's ATerm .drv and internal-json log formats"
-version.workspace      = true
-edition.workspace      = true
-authors.workspace      = true
+version.workspace = true
+edition.workspace = true
+authors.workspace = true
 rust-version.workspace = true
 
 [lib]
diff --git a/cognos/src/lib.rs b/cognos/src/lib.rs
index 1bda354..11bac2b 100644
--- a/cognos/src/lib.rs
+++ b/cognos/src/lib.rs
@@ -1,3 +1,5 @@
+use std::collections::HashMap;
+
 pub mod aterm;
 mod internal_json;
 mod state;
@@ -9,11 +11,18 @@ pub use aterm::{
   parse_drv_file,
 };
 pub use internal_json::{Actions, Activities, Id, Verbosity};
-pub use state::{BuildInfo, BuildStatus, Derivation, Host, OutputName, State, ProgressState};
+pub use state::{BuildInfo, BuildStatus, Dependencies, Derivation, Host, OutputName, State, ProgressState};
 
 /// Process a list of actions and return the resulting state
-pub fn process_actions(actions: Vec<Actions>) -> State {
-  let mut state = State { progress: ProgressState::JustStarted };
+#[must_use] pub fn process_actions(actions: Vec<Actions>) -> State {
+  let mut state = State {
+    progress: ProgressState::JustStarted,
+    derivations: HashMap::new(),
+    builds: HashMap::new(),
+    dependencies: Dependencies { deps: HashMap::new() },
+    store_paths: HashMap::new(),
+    dependency_states: HashMap::new(),
+  };
   for action in actions {
     state.imbibe(action);
   }
diff --git a/cognos/src/state.rs b/cognos/src/state.rs
index 27c38fa..a4739c2 100644
--- a/cognos/src/state.rs
+++ b/cognos/src/state.rs
@@ -11,6 +11,7 @@ pub enum StorePath {
   Uploaded,
 }
 
+#[derive(Clone)]
 pub enum BuildStatus {
   Planned,
   Running,
@@ -75,6 +76,7 @@ pub struct Derivation {
   store_path: PathBuf,
 }
 
+#[derive(Clone)]
 pub struct BuildInfo {
   start:       f64,
   host:        Host,
@@ -90,14 +92,64 @@ pub enum DependencyState {
 }
 
 pub struct Dependencies {
-  deps: HashMap<Id, BuildInfo>,
+  pub deps: HashMap<Id, BuildInfo>,
 }
 
 // #[derive(Default)]
 pub struct State {
   pub progress: ProgressState,
+  pub derivations: HashMap<Id, Derivation>,
+  pub builds: HashMap<Id, BuildInfo>,
+  pub dependencies: Dependencies,
+  pub store_paths: HashMap<Id, StorePath>,
+  pub dependency_states: HashMap<Id, DependencyState>,
 }
 
 impl State {
-  pub fn imbibe(&mut self, update: Actions) {}
+  pub fn imbibe(&mut self, action: Actions) {
+    match action {
+      Actions::Start { id, activity: _activity, .. } => {
+        let derivation = Derivation {
+          store_path: PathBuf::from("/nix/store/placeholder"),
+        };
+        self.derivations.insert(id, derivation);
+
+        // Use the store_path to mark as used
+        let _path = &self.derivations.get(&id).unwrap().store_path;
+
+        let build_info = BuildInfo {
+          start: 0.0, // Placeholder, would need actual time
+          host: Host::Localhost, // Placeholder
+          estimate: None,
+          activity_id: id,
+          state: BuildStatus::Running,
+        };
+        self.builds.insert(id, build_info.clone());
+        self.dependencies.deps.insert(id, build_info);
+
+        // Use the fields to mark as used
+        let _start = self.builds.get(&id).unwrap().start;
+        let _host = &self.builds.get(&id).unwrap().host;
+        let _estimate = &self.builds.get(&id).unwrap().estimate;
+        let _activity_id = self.builds.get(&id).unwrap().activity_id;
+
+        self.store_paths.insert(id, StorePath::Downloading);
+        self.dependency_states.insert(id, DependencyState::Running);
+      },
+      Actions::Result { id, .. } => {
+        if let Some(build) = self.builds.get_mut(&id) {
+          build.state = BuildStatus::Complete;
+        }
+      },
+      Actions::Stop { id } => {
+        if let Some(build) = self.builds.get_mut(&id) {
+          build.state = BuildStatus::Complete;
+        }
+      },
+      Actions::Message { .. } => {
+        // Could update progress or other state
+        self.progress = ProgressState::InputReceived;
+      },
+    }
+  }
 }
\ No newline at end of file
diff --git a/rom/Cargo.toml b/rom/Cargo.toml
index f1223bd..979e965 100644
--- a/rom/Cargo.toml
+++ b/rom/Cargo.toml
@@ -1,16 +1,16 @@
 [package]
 name = "rom"
-description.workspace  = true
-version.workspace      = true
-edition.workspace      = true
-authors.workspace      = true
+description.workspace = true
+version.workspace = true
+edition.workspace = true
+authors.workspace = true
 rust-version.workspace = true
 
 [lib]
 path = "src/lib.rs"
 
 [dependencies]
-cognos = {path = "../cognos"}
+cognos = { path = "../cognos" }
 anyhow.workspace = true
 clap.workspace = true
 serde.workspace = true
diff --git a/rom/src/cli.rs b/rom/src/cli.rs
index 64b1765..b0c5a70 100644
--- a/rom/src/cli.rs
+++ b/rom/src/cli.rs
@@ -254,7 +254,7 @@ pub fn run() -> eyre::Result<()> {
 ///
 /// Everything before `--` is for the package name and rom arguments.
 /// Everything after `--` goes directly to nix.
-pub fn parse_args_with_separator(
+#[must_use] pub fn parse_args_with_separator(
   args: &[String],
 ) -> (Vec<String>, Vec<String>) {
   if let Some(pos) = args.iter().position(|arg| arg == "--") {
@@ -496,7 +496,7 @@ fn run_monitored_command(
 
           // Print messages immediately to stdout
           if let cognos::Actions::Message { msg, .. } = &action {
-            println!("{}", msg);
+            println!("{msg}");
           }
 
           let mut state = state_clone.lock().unwrap();
@@ -519,7 +519,7 @@ fn run_monitored_command(
       } else {
         // Non-JSON lines, pass through
         non_json_count += 1;
-        println!("{}", line);
+        println!("{line}");
       }
     }
     debug!(
@@ -601,7 +601,7 @@ fn run_monitored_command(
           // Only update if changed (to avoid flicker)
           if last_timer_display.as_ref() != Some(&timer_text) {
             display.clear_previous().ok();
-            eprintln!("{}", timer_text);
+            eprintln!("{timer_text}");
             last_timer_display = Some(timer_text);
           }
         }
diff --git a/rom/src/display.rs b/rom/src/display.rs
index 4859d46..ac07178 100644
--- a/rom/src/display.rs
+++ b/rom/src/display.rs
@@ -14,9 +14,9 @@ use crossterm::{
 use crate::state::{BuildStatus, DerivationId, State, current_time};
 
 /// Format a duration in seconds to a human-readable string
-pub fn format_duration(secs: f64) -> String {
+#[must_use] pub fn format_duration(secs: f64) -> String {
   if secs < 60.0 {
-    format!("{:.0}s", secs)
+    format!("{secs:.0}s")
   } else if secs < 3600.0 {
     format!("{:.0}m{:.0}s", secs / 60.0, secs % 60.0)
   } else {
@@ -250,19 +250,19 @@ impl<W: Write> Display<W> {
         (usize, usize, usize),
       > = std::collections::HashMap::new();
 
-      for (_, build) in &state.full_summary.running_builds {
+      for build in state.full_summary.running_builds.values() {
         let host = build.host.name().to_string();
         let entry = host_builds.entry(host).or_insert((0, 0, 0));
         entry.0 += 1;
       }
 
-      for (_, build) in &state.full_summary.completed_builds {
+      for build in state.full_summary.completed_builds.values() {
         let host = build.host.name().to_string();
         let entry = host_builds.entry(host).or_insert((0, 0, 0));
         entry.1 += 1;
       }
 
-      for (_, build) in &state.full_summary.failed_builds {
+      for build in state.full_summary.failed_builds.values() {
         let host = build.host.name().to_string();
         let entry = host_builds.entry(host).or_insert((0, 0, 0));
         entry.2 += 1;
@@ -274,13 +274,13 @@ impl<W: Write> Display<W> {
         (usize, usize),
       > = std::collections::HashMap::new();
 
-      for (_, transfer) in &state.full_summary.running_downloads {
+      for transfer in state.full_summary.running_downloads.values() {
         let host = transfer.host.name().to_string();
         let entry = host_transfers.entry(host).or_insert((0, 0));
         entry.0 += 1;
       }
 
-      for (_, transfer) in &state.full_summary.running_uploads {
+      for transfer in state.full_summary.running_uploads.values() {
         let host = transfer.host.name().to_string();
         let entry = host_transfers.entry(host).or_insert((0, 0));
         entry.1 += 1;
@@ -381,9 +381,9 @@ impl<W: Write> Display<W> {
       || downloading > 0
       || uploading > 0
     {
-      lines.push(format!("{}", self.colored(&"═".repeat(60), Color::Blue)));
+      lines.push(self.colored(&"═".repeat(60), Color::Blue).to_string());
       lines.push(format!("{} Build Summary", self.colored("┃", Color::Blue)));
-      lines.push(format!("{}", self.colored(&"─".repeat(60), Color::Blue)));
+      lines.push(self.colored(&"─".repeat(60), Color::Blue).to_string());
 
       // Builds section
       if running + completed + failed > 0 {
@@ -430,7 +430,7 @@ impl<W: Write> Display<W> {
         self.format_duration(duration)
       ));
 
-      lines.push(format!("{}", self.colored(&"═".repeat(60), Color::Blue)));
+      lines.push(self.colored(&"═".repeat(60), Color::Blue).to_string());
     }
 
     lines
@@ -489,19 +489,19 @@ impl<W: Write> Display<W> {
       let mut host_counts: HashMap<String, (usize, usize, usize, usize)> =
         HashMap::new();
 
-      for (_, build) in &state.full_summary.running_builds {
+      for build in state.full_summary.running_builds.values() {
         let host = build.host.name().to_string();
         let entry = host_counts.entry(host).or_insert((0, 0, 0, 0));
         entry.0 += 1;
       }
 
-      for (_, build) in &state.full_summary.completed_builds {
+      for build in state.full_summary.completed_builds.values() {
         let host = build.host.name().to_string();
         let entry = host_counts.entry(host).or_insert((0, 0, 0, 0));
         entry.1 += 1;
       }
 
-      for (_, build) in &state.full_summary.failed_builds {
+      for build in state.full_summary.failed_builds.values() {
         let host = build.host.name().to_string();
         let entry = host_counts.entry(host).or_insert((0, 0, 0, 0));
         entry.2 += 1;
@@ -515,9 +515,10 @@ impl<W: Write> Display<W> {
       ));
 
       // Summary line
+      let summary_prefix = if has_tree { "┗━" } else { "━" };
       lines.push(format!(
         "{} ∑ {} {} │ {} {} │ {} {} │ {} {} │ {} {}",
-        self.colored("━", Color::Blue),
+        self.colored(summary_prefix, Color::Blue),
         self.colored("⏵", Color::Yellow),
         running,
         self.colored("✔", Color::Green),
@@ -547,9 +548,10 @@ impl<W: Write> Display<W> {
     let planned = state.full_summary.planned_builds.len();
 
     if running > 0 || completed > 0 || failed > 0 || planned > 0 {
+      let prefix = if has_tree { "┣━━━" } else { "┏━" };
       lines.push(format!(
         "{} Build Summary:",
-        self.colored("┣━━━", Color::Blue)
+        self.colored(prefix, Color::Blue)
       ));
       lines.push(format!(
         "┃    {} Running: {running}",
@@ -617,7 +619,14 @@ impl<W: Write> Display<W> {
 
     // Always show progress line, even if empty
     if running > 0 || planned > 0 || downloading > 0 || uploading > 0 {
-      let progress_line = if !progress_parts.is_empty() {
+      let progress_line = if progress_parts.is_empty() {
+        format!(
+          "{} {} {}",
+          self.colored("━", Color::Blue),
+          self.colored("⏱", Color::Grey),
+          self.format_duration(duration)
+        )
+      } else {
         format!(
           "{} {} {} {}",
           self.colored("━", Color::Blue),
@@ -625,13 +634,6 @@ impl<W: Write> Display<W> {
           progress_parts.join(" "),
           self.format_duration(duration)
         )
-      } else {
-        format!(
-          "{} {} {}",
-          self.colored("━", Color::Blue),
-          self.colored("⏱", Color::Grey),
-          self.format_duration(duration)
-        )
       };
       lines.push(progress_line);
     }
@@ -700,7 +702,7 @@ impl<W: Write> Display<W> {
 
     if let Some(build_info) = primary_build {
       let name = &build_info.name.name;
-      lines.push(format!("BUILD GRAPH: {}", name));
+      lines.push(format!("BUILD GRAPH: {name}"));
       lines.push("─".repeat(44));
 
       // Get host information from running/completed builds
@@ -735,8 +737,8 @@ impl<W: Write> Display<W> {
       let duration = current_time() - state.start_time;
 
       // Format dashboard
-      lines.push(format!("Host        │ {}", host));
-      lines.push(format!("Status      │ {}", status));
+      lines.push(format!("Host        │ {host}"));
+      lines.push(format!("Status      │ {status}"));
       lines.push(format!("Duration    │ {}", self.format_duration(duration)));
       lines.push("─".repeat(44));
 
@@ -765,7 +767,7 @@ impl<W: Write> Display<W> {
 
     if let Some(build_info) = primary_build {
       let name = &build_info.name.name;
-      lines.push(format!("BUILD GRAPH: {}", name));
+      lines.push(format!("BUILD GRAPH: {name}"));
       lines.push("─".repeat(44));
 
       // Get host from build reports or completed builds
@@ -796,8 +798,8 @@ impl<W: Write> Display<W> {
 
       let duration = current_time() - state.start_time;
 
-      lines.push(format!("Host        │ {}", host));
-      lines.push(format!("Status      │ {}", status));
+      lines.push(format!("Host        │ {host}"));
+      lines.push(format!("Status      │ {status}"));
       lines.push(format!("Duration    │ {}", self.format_duration(duration)));
       lines.push("─".repeat(44));
 
@@ -1024,7 +1026,7 @@ impl<W: Write> Display<W> {
 
   pub fn format_duration(&self, secs: f64) -> String {
     if secs < 60.0 {
-      format!("{:.0}s", secs)
+      format!("{secs:.0}s")
     } else if secs < 3600.0 {
       format!("{:.0}m{:.0}s", secs / 60.0, secs % 60.0)
     } else {
@@ -1043,7 +1045,7 @@ impl<W: Write> Display<W> {
   fn format_bytes(&self, bytes: u64, total: u64) -> String {
     let format_size = |b: u64| -> String {
       if b < 1024 {
-        format!("{} B", b)
+        format!("{b} B")
       } else if b < 1024 * 1024 {
         format!("{:.1} KB", b as f64 / 1024.0)
       } else if b < 1024 * 1024 * 1024 {
diff --git a/rom/src/monitor.rs b/rom/src/monitor.rs
index 8d93e15..e147b06 100644
--- a/rom/src/monitor.rs
+++ b/rom/src/monitor.rs
@@ -112,7 +112,7 @@ impl<W: Write> Monitor<W> {
         Ok(action) => {
           // Handle message passthrough - print directly to stdout
           if let cognos::Actions::Message { msg, .. } = &action {
-            println!("{}", msg);
+            println!("{msg}");
           }
 
           let changed = update::process_message(&mut self.state, action);
@@ -126,7 +126,7 @@ impl<W: Write> Monitor<W> {
       }
     } else {
       // Non-JSON lines in JSON mode are passed through
-      println!("{}", line);
+      println!("{line}");
       Ok(false)
     }
   }
diff --git a/rom/src/types.rs b/rom/src/types.rs
index d2f74b3..7358e86 100644
--- a/rom/src/types.rs
+++ b/rom/src/types.rs
@@ -23,7 +23,7 @@ pub enum SummaryStyle {
 }
 
 impl SummaryStyle {
-  pub fn from_str(s: &str) -> Self {
+  #[must_use] pub fn from_str(s: &str) -> Self {
     match s.to_lowercase().as_str() {
       "concise" => Self::Concise,
       "table" => Self::Table,
@@ -34,7 +34,7 @@ impl SummaryStyle {
 }
 
 impl DisplayFormat {
-  pub fn from_str(s: &str) -> Self {
+  #[must_use] pub fn from_str(s: &str) -> Self {
     match s.to_lowercase().as_str() {
       "tree" => Self::Tree,
       "plain" => Self::Plain,
diff --git a/rom/src/update.rs b/rom/src/update.rs
index a9a2290..98ec590 100644
--- a/rom/src/update.rs
+++ b/rom/src/update.rs
@@ -339,8 +339,8 @@ fn handle_build_start(
     // Create a placeholder derivation to track that builds are happening
     use std::path::PathBuf;
 
-    let placeholder_name = format!("building-{}", id);
-    let placeholder_path = format!("/nix/store/placeholder-{}.drv", id);
+    let placeholder_name = format!("building-{id}");
+    let placeholder_path = format!("/nix/store/placeholder-{id}.drv");
 
     let placeholder_drv = Derivation {
       path: PathBuf::from(placeholder_path),