diff --git a/src/cli/commands/mod.rs b/src/cli/commands/mod.rs
index 5f7a5b0..ca06e4e 100644
--- a/src/cli/commands/mod.rs
+++ b/src/cli/commands/mod.rs
@@ -7,6 +7,7 @@ mod history;
 mod pr;
 mod release;
 mod ship;
+pub mod smartlog;
 mod stack;
 mod tracker_cmds;
 mod workspace;
@@ -20,6 +21,7 @@ pub use history::*;
 pub use pr::*;
 pub use release::*;
 pub use ship::*;
+pub use smartlog::smartlog;
 pub use stack::*;
 pub use tracker_cmds::*;
 pub use workspace::*;
diff --git a/src/cli/commands/smartlog.rs b/src/cli/commands/smartlog.rs
new file mode 100644
index 0000000..50f987a
--- /dev/null
+++ b/src/cli/commands/smartlog.rs
@@ -0,0 +1,315 @@
+//! `parsec smartlog` (alias `sl`) — visualize active worktrees as a commit DAG.
+//!
+//! Issue #245 — Phase 1 (skeleton):
+//! - Collect every active worktree via [`WorktreeManager`]
+//! - Read each worktree's commits since its base branch (`base..branch`)
+//! - Render as ASCII tree, or emit JSON
+//!
+//! PR/CI/review overlay is intentionally **out of scope** for this PR;
+//! [`SmartlogNode::pr`] / [`SmartlogNode::ci`] fields are placeholders that
+//! later PRs will populate (e.g., GitHub PR state, CI run state, review state).
+
+use std::collections::BTreeMap;
+use std::path::{Path, PathBuf};
+
+use anyhow::Result;
+use chrono::{DateTime, Utc};
+use serde::Serialize;
+
+use crate::config::ParsecConfig;
+use crate::git;
+use crate::output::Mode;
+use crate::worktree::WorktreeManager;
+
+/// Default number of commits per worktree shown in the DAG.
+const DEFAULT_DEPTH: usize = 10;
+
+/// One worktree's row in the smartlog output.
+#[derive(Debug, Clone, Serialize)]
+pub struct SmartlogNode {
+    pub ticket: String,
+    pub ticket_title: Option<String>,
+    pub branch: String,
+    pub base_branch: String,
+    pub worktree_path: PathBuf,
+    pub commits: Vec<CommitSummary>,
+    /// PR overlay — populated by a later PR (see #245 follow-up).
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub pr: Option<serde_json::Value>,
+    /// CI overlay — populated by a later PR (see #245 follow-up).
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub ci: Option<serde_json::Value>,
+}
+
+/// Single commit in a worktree's diff against its base.
+#[derive(Debug, Clone, Serialize, PartialEq, Eq)]
+pub struct CommitSummary {
+    pub sha_short: String,
+    pub subject: String,
+    pub author: String,
+    pub timestamp: DateTime<Utc>,
+}
+
+/// Entry point for the `smartlog` subcommand.
+pub async fn smartlog(repo: &Path, depth: Option<usize>, mode: Mode) -> Result<()> {
+    let depth = depth.unwrap_or(DEFAULT_DEPTH);
+    let config = ParsecConfig::load()?;
+    let manager = WorktreeManager::new(repo, &config)?;
+    let workspaces = manager.list()?;
+
+    let mut nodes = Vec::with_capacity(workspaces.len());
+    for ws in workspaces {
+        let commits = collect_commits(&ws.path, &ws.base_branch, &ws.branch, depth)
+            // Soft-fail per worktree: a corrupt worktree shouldn't take the whole
+            // command down. Empty list is rendered as "(no commits)" instead.
+            .unwrap_or_default();
+        nodes.push(SmartlogNode {
+            ticket: ws.ticket,
+            ticket_title: ws.ticket_title,
+            branch: ws.branch,
+            base_branch: ws.base_branch,
+            worktree_path: ws.path,
+            commits,
+            pr: None,
+            ci: None,
+        });
+    }
+
+    match mode {
+        Mode::Json => {
+            println!("{}", serde_json::to_string_pretty(&nodes)?);
+        }
+        _ => {
+            print!("{}", render_text(&nodes));
+        }
+    }
+    Ok(())
+}
+
+/// Read commits in `base..branch` from a worktree, capped at `depth`.
+///
+/// Pure shell-out to `git log` — no `git2` dependency, matches the rest of the
+/// `git/` module's style. Returns empty `Vec` (not error) when range is empty
+/// or git refuses to walk (e.g., orphan branch).
+fn collect_commits(
+    worktree: &Path,
+    base: &str,
+    branch: &str,
+    depth: usize,
+) -> Result<Vec<CommitSummary>> {
+    let range = format!("{}..{}", base, branch);
+    let limit = format!("-n{}", depth);
+    let raw = git::run_output(
+        worktree,
+        &["log", &range, "--pretty=format:%h\t%s\t%an\t%aI", &limit],
+    )?;
+    Ok(raw.lines().filter_map(parse_commit_line).collect())
+}
+
+/// Parse a single tab-separated line emitted by our `git log --pretty` format.
+///
+/// Format: `<sha_short>\t<subject>\t<author_name>\t<author_iso8601>`.
+/// Any line that doesn't conform is silently dropped; this keeps the parser
+/// resilient to commit messages containing tabs (we splitn by 4 so the first
+/// three tabs are guaranteed to be the field separators).
+fn parse_commit_line(line: &str) -> Option<CommitSummary> {
+    let mut parts = line.splitn(4, '\t');
+    let sha_short = parts.next()?.trim().to_string();
+    let subject = parts.next()?.to_string();
+    let author = parts.next()?.to_string();
+    let ts_raw = parts.next()?.trim();
+    let timestamp = DateTime::parse_from_rfc3339(ts_raw)
+        .ok()?
+        .with_timezone(&Utc);
+    if sha_short.is_empty() {
+        return None;
+    }
+    Some(CommitSummary {
+        sha_short,
+        subject,
+        author,
+        timestamp,
+    })
+}
+
+/// Render an ASCII commit DAG, grouped by base branch.
+///
+/// Returns the rendered string (instead of printing) so it's testable. Empty
+/// node list returns a single explanatory line.
+pub fn render_text(nodes: &[SmartlogNode]) -> String {
+    if nodes.is_empty() {
+        return "No active worktrees. Run `parsec start <ticket>` to create one.\n".to_string();
+    }
+
+    let mut by_base: BTreeMap<String, Vec<&SmartlogNode>> = BTreeMap::new();
+    for n in nodes {
+        by_base.entry(n.base_branch.clone()).or_default().push(n);
+    }
+
+    let mut out = String::new();
+    let base_count = by_base.len();
+    for (base_idx, (base, group)) in by_base.iter().enumerate() {
+        out.push_str(&format!("○ {} (base)\n", base));
+        let last_idx = group.len().saturating_sub(1);
+        for (i, node) in group.iter().enumerate() {
+            let is_last = i == last_idx;
+            let branch_glyph = if is_last { "└" } else { "├" };
+            let title = node.ticket_title.as_deref().unwrap_or("(no title)");
+            out.push_str("│\n");
+            out.push_str(&format!(
+                "{}─● {} {} [{}]\n",
+                branch_glyph, node.ticket, title, node.branch
+            ));
+
+            let prefix = if is_last { "   " } else { "│  " };
+            if node.commits.is_empty() {
+                out.push_str(&format!("{}└─ (no commits since {})\n", prefix, base));
+            } else {
+                let last_c = node.commits.len() - 1;
+                for (ci, c) in node.commits.iter().enumerate() {
+                    let glyph = if ci == last_c { "└" } else { "├" };
+                    out.push_str(&format!(
+                        "{}{}─ {} {}\n",
+                        prefix, glyph, c.sha_short, c.subject
+                    ));
+                }
+            }
+        }
+        if base_idx + 1 < base_count {
+            out.push('\n');
+        }
+    }
+    out
+}
+
+// ---------------------------------------------------------------------------
+// Tests
+// ---------------------------------------------------------------------------
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use chrono::TimeZone;
+
+    fn mk_commit(sha: &str, subject: &str) -> CommitSummary {
+        CommitSummary {
+            sha_short: sha.to_string(),
+            subject: subject.to_string(),
+            author: "Eric".to_string(),
+            timestamp: Utc.with_ymd_and_hms(2026, 5, 13, 0, 0, 0).unwrap(),
+        }
+    }
+
+    fn mk_node(
+        ticket: &str,
+        title: Option<&str>,
+        branch: &str,
+        commits: Vec<CommitSummary>,
+    ) -> SmartlogNode {
+        SmartlogNode {
+            ticket: ticket.to_string(),
+            ticket_title: title.map(|t| t.to_string()),
+            branch: branch.to_string(),
+            base_branch: "main".to_string(),
+            worktree_path: PathBuf::from(format!("/tmp/{}", ticket)),
+            commits,
+            pr: None,
+            ci: None,
+        }
+    }
+
+    #[test]
+    fn parse_commit_line_basic() {
+        let c =
+            parse_commit_line("a1b2c3d\tFix auth bug\tEric\t2026-05-13T09:30:00+09:00").unwrap();
+        assert_eq!(c.sha_short, "a1b2c3d");
+        assert_eq!(c.subject, "Fix auth bug");
+        assert_eq!(c.author, "Eric");
+    }
+
+    #[test]
+    fn parse_commit_line_subject_with_tabs() {
+        // splitn(4) means tabs in the subject are preserved (first 3 tabs are separators)
+        let c = parse_commit_line("aa\tsub\twith\ttab\tEric\t2026-05-13T09:30:00+09:00");
+        // splitn(4, '\t') → ["aa", "sub", "with", "tab\tEric\t2026-05-13T09:30:00+09:00"]
+        // Last segment isn't a valid timestamp → None.
+        assert!(c.is_none(), "ambiguous line should be rejected");
+    }
+
+    #[test]
+    fn parse_commit_line_rejects_garbage() {
+        assert!(parse_commit_line("").is_none());
+        assert!(parse_commit_line("only_one_field").is_none());
+        assert!(parse_commit_line("a\tb\tc\tnot-a-date").is_none());
+    }
+
+    #[test]
+    fn parse_commit_line_rejects_empty_sha() {
+        assert!(parse_commit_line("\tsubject\tEric\t2026-05-13T09:30:00+09:00").is_none());
+    }
+
+    #[test]
+    fn render_text_empty() {
+        let s = render_text(&[]);
+        assert!(s.contains("No active worktrees"));
+    }
+
+    #[test]
+    fn render_text_single_node() {
+        let nodes = vec![mk_node(
+            "CL-2283",
+            Some("Add rate limiting"),
+            "feature/CL-2283",
+            vec![mk_commit("a1b2c3d", "Implement rate limiter")],
+        )];
+        let s = render_text(&nodes);
+        assert!(s.contains("○ main (base)"));
+        assert!(s.contains("CL-2283"));
+        assert!(s.contains("Add rate limiting"));
+        assert!(s.contains("[feature/CL-2283]"));
+        assert!(s.contains("a1b2c3d Implement rate limiter"));
+    }
+
+    #[test]
+    fn render_text_no_commits_shows_placeholder() {
+        let nodes = vec![mk_node("CL-2291", None, "scratch/CL-2291", vec![])];
+        let s = render_text(&nodes);
+        assert!(s.contains("(no commits since main)"));
+        assert!(s.contains("(no title)"));
+    }
+
+    #[test]
+    fn render_text_multiple_nodes_groups_by_base() {
+        let mut a = mk_node(
+            "CL-1",
+            Some("A"),
+            "f/CL-1",
+            vec![mk_commit("aaaaaaa", "first commit")],
+        );
+        a.base_branch = "main".to_string();
+        let mut b = mk_node(
+            "CL-2",
+            Some("B"),
+            "f/CL-2",
+            vec![mk_commit("bbbbbbb", "second commit")],
+        );
+        b.base_branch = "develop".to_string();
+        let s = render_text(&[a, b]);
+        assert!(s.contains("○ main (base)"));
+        assert!(s.contains("○ develop (base)"));
+        // Both nodes should render their commits.
+        assert!(s.contains("first commit"));
+        assert!(s.contains("second commit"));
+    }
+
+    #[test]
+    fn smartlog_node_serializes_without_overlay_fields() {
+        let node = mk_node("CL-1", Some("A"), "f/CL-1", vec![]);
+        let json = serde_json::to_string(&node).unwrap();
+        // PR/CI placeholder fields use skip_serializing_if so they don't pollute
+        // the JSON output until a follow-up PR populates them.
+        assert!(!json.contains("\"pr\""));
+        assert!(!json.contains("\"ci\""));
+        assert!(json.contains("\"ticket\":\"CL-1\""));
+    }
+}
diff --git a/src/cli/mod.rs b/src/cli/mod.rs
index 94f71f8..318faa8 100644
--- a/src/cli/mod.rs
+++ b/src/cli/mod.rs
@@ -501,6 +501,17 @@ pub enum Command {
         /// New ticket identifier
         new_ticket: String,
     },
+
+    /// Visualize active worktrees as a commit DAG (alias: sl)
+    ///
+    /// Lists every active worktree, the commits it adds on top of its base
+    /// branch, and (in later releases) PR/CI/review state. Issue #245.
+    #[command(alias = "sl")]
+    Smartlog {
+        /// Maximum commits per worktree (default: 10)
+        #[arg(long, short)]
+        depth: Option<usize>,
+    },
 }
 
 #[derive(Subcommand)]
@@ -596,6 +607,7 @@ pub async fn run(cli: Cli) -> Result<()> {
         Command::Create { .. } => "create",
         Command::Rename { .. } => "rename",
         Command::Compress { .. } => "compress",
+        Command::Smartlog { .. } => "smartlog",
     };
     let exec_id = crate::execlog::new_execution_id();
     let exec_started_at = chrono::Utc::now();
@@ -882,6 +894,7 @@ pub async fn run(cli: Cli) -> Result<()> {
         Command::Compress { ticket, message } => {
             commands::compress(&repo_path, ticket.as_deref(), message, output_mode).await
         }
+        Command::Smartlog { depth } => commands::smartlog(&repo_path, depth, output_mode).await,
     };
 
     // Record execution entry (best-effort, never fail the command)