diff --git a/src/cli.rs b/src/cli.rs
index 4c9d665..c3b1f21 100644
--- a/src/cli.rs
+++ b/src/cli.rs
@@ -5,12 +5,13 @@
 //! ```text
 //! anwesen serve  --vault <path> [--bind <addr:port>] [--log-level <level>]
 //! anwesen doctor --vault <path> [--log-level <level>]
+//! anwesen merge  --vault <path> [--query <string>] [--log-level <level>]
 //! anwesen version
 //! ```
 //!
-//! `--bind` is `serve`-only; `doctor` does not bind a port; `version` takes
-//! no flags. Each flag has a matching `ANWESEN_<UPPER>` environment variable
-//! and CLI wins over env per the manual.
+//! `--bind` is `serve`-only; `doctor` and `merge` do not bind a port;
+//! `version` takes no flags. Each flag has a matching `ANWESEN_<UPPER>`
+//! environment variable and CLI wins over env per the manual.
 
 use std::net::SocketAddr;
 use std::path::PathBuf;
@@ -30,6 +31,9 @@ pub enum Command {
     Serve(ServeArgs),
     /// Walk the vault once and report ingestion blockers. Read-only.
     Doctor(DoctorArgs),
+    /// Walk the vault once, evaluate the query, and write the merged markdown
+    /// document to stdout. One-shot; no server. Read-only.
+    Merge(MergeArgs),
     /// Print the version and exit.
     Version,
 }
@@ -60,6 +64,25 @@ pub struct DoctorArgs {
     pub log_level: LogLevel,
 }
 
+#[derive(Debug, clap::Args)]
+pub struct MergeArgs {
+    /// Path to the vault root.
+    #[arg(long, env = "ANWESEN_VAULT")]
+    pub vault: PathBuf,
+
+    /// Query in the `/query` query-string grammar, for example
+    /// `tags=anwesen&__anw-kind=skill&__anw-order=order`. The `__anw-kind`
+    /// homogeneity guard and `__anw-order` fragment ordering ride inside this
+    /// string -- there are no separate flags. Empty merges every note under
+    /// the vault root.
+    #[arg(long, env = "ANWESEN_QUERY", default_value = "")]
+    pub query: String,
+
+    /// Log verbosity. Logs go to stderr; the merged document goes to stdout.
+    #[arg(long, env = "ANWESEN_LOG_LEVEL", default_value = "info")]
+    pub log_level: LogLevel,
+}
+
 #[derive(Debug, Clone, Copy, ValueEnum)]
 #[value(rename_all = "lower")]
 pub enum LogLevel {
@@ -142,6 +165,51 @@ mod tests {
         }
     }
 
+    #[test]
+    fn merge_requires_vault() {
+        assert!(parse(&["merge"]).is_err());
+    }
+
+    #[test]
+    fn merge_query_defaults_to_empty() {
+        let cli = parse(&["merge", "--vault", "/tmp/v"]).expect("parse");
+        match cli.command {
+            Command::Merge(a) => {
+                assert_eq!(a.vault, PathBuf::from("/tmp/v"));
+                assert_eq!(a.query, "");
+            }
+            _ => panic!("expected merge"),
+        }
+    }
+
+    #[test]
+    fn merge_accepts_vault_query_and_log_level() {
+        let cli = parse(&[
+            "merge",
+            "--vault",
+            "/tmp/v",
+            "--query",
+            "tags=anwesen&__anw-order=order",
+            "--log-level",
+            "warn",
+        ])
+        .expect("parse");
+        match cli.command {
+            Command::Merge(a) => {
+                assert_eq!(a.query, "tags=anwesen&__anw-order=order");
+                assert!(matches!(a.log_level, LogLevel::Warn));
+            }
+            _ => panic!("expected merge"),
+        }
+    }
+
+    #[test]
+    fn merge_rejects_bind() {
+        // --bind is serve-only; merge must not accept it.
+        let err = parse(&["merge", "--vault", "/tmp/v", "--bind", "0.0.0.0:9000"]).unwrap_err();
+        assert_eq!(err.kind(), clap::error::ErrorKind::UnknownArgument);
+    }
+
     #[test]
     fn version_takes_no_flags() {
         assert!(matches!(
diff --git a/src/lib.rs b/src/lib.rs
index 2fa823f..0111390 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -10,6 +10,7 @@ pub mod app;
 pub mod doctor;
 pub mod health;
 pub mod http;
+pub mod merge;
 pub mod query;
 pub mod store;
 pub mod vault;
diff --git a/src/main.rs b/src/main.rs
index 8f9997d..f265ced 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,12 +1,13 @@
 //! Anwesen: read-only HTTP daemon over a markdown vault.
 //!
-//! This module wires the CLI to the (still-stub) `serve` and `doctor`
-//! subcommands. The full daemon arrives over [ANW-11..ANW-19].
+//! This module wires the CLI to the `serve`, `doctor`, `merge`, and
+//! `version` subcommands.
 
 mod cli;
 
 use anwesen::app::Anwesen;
 use anwesen::doctor;
+use anwesen::merge;
 use anyhow::Result;
 use clap::Parser;
 use hydra::Application;
@@ -38,6 +39,19 @@ fn main() -> Result<()> {
             print!("{rendered}");
             std::process::exit(exit);
         }
+        Command::Merge(args) => {
+            init_logging(args.log_level);
+            match merge::run(&args.vault, &args.query) {
+                // `print!`, not `println!`: the merged document is byte-stable
+                // and byte-identical to the HTTP merge body, which carries no
+                // trailing newline. An empty match set prints nothing, exit 0.
+                Ok(doc) => print!("{doc}"),
+                Err(e) => {
+                    eprint!("{}", e.render());
+                    std::process::exit(1);
+                }
+            }
+        }
         Command::Version => {
             println!("{}", env!("CARGO_PKG_VERSION"));
         }
diff --git a/src/merge.rs b/src/merge.rs
new file mode 100644
index 0000000..a9b6d2b
--- /dev/null
+++ b/src/merge.rs
@@ -0,0 +1,205 @@
+//! One-shot local markdown-merge for the `anwesen merge` subcommand ([ANW-27]).
+//!
+//! Walks a vault directory once (the same [`vault::scan`] as `doctor`),
+//! evaluates the `--query` string, and assembles the merged markdown document
+//! with [`query::execute_merge`] -- the very engine the HTTP `/query` merge
+//! mode ([ANW-26]) uses. CLI and HTTP output are therefore byte-identical for
+//! the same vault and query. No HTTP, no watcher, no persistent index.
+
+use std::fmt::Write as _;
+use std::path::Path;
+
+use crate::query::{self, MergeError, QueryError};
+use crate::store::NoteStore;
+use crate::vault::{self, ScanIssue};
+
+/// Why a one-shot merge could not produce a document.
+#[derive(Debug)]
+pub enum MergeCliError {
+    /// The `--query` string did not parse. Same grammar, same message as the
+    /// HTTP `/query` `400`.
+    Query(QueryError),
+    /// One or more files could not be read, or their frontmatter did not
+    /// parse. Same hard-failure posture as `doctor`; soft warnings (e.g. a
+    /// non-mapping frontmatter root) are ignored, matching what `serve`
+    /// ingests.
+    Scan(Vec<ScanIssue>),
+    /// The `__anw-kind` homogeneity guard rejected the matched set. The
+    /// `String` is the same naming message the HTTP path returns as `400`,
+    /// surfaced here on stderr instead.
+    Kind(String),
+}
+
+impl MergeCliError {
+    /// Render the error for stderr. One concern per line, deterministic so the
+    /// stderr surface is golden-testable.
+    #[must_use]
+    pub fn render(&self) -> String {
+        match self {
+            Self::Query(e) => format!("{e}\n"),
+            Self::Scan(issues) => {
+                let mut s = String::from("merge: cannot read vault\n");
+                for issue in issues {
+                    let _ = writeln!(s, "  {}: {}", issue.path.display(), issue.kind);
+                }
+                s
+            }
+            Self::Kind(msg) => msg.clone(),
+        }
+    }
+}
+
+/// Walk `vault_root`, evaluate `raw_query`, and return the merged document.
+///
+/// On success the returned `String` is byte-identical to the HTTP merge body
+/// for the same vault and query. An empty match set yields an empty string.
+///
+/// # Errors
+/// - [`MergeCliError::Query`] when `raw_query` is malformed;
+/// - [`MergeCliError::Scan`] when the directory is unreadable or any file's
+///   frontmatter fails to parse;
+/// - [`MergeCliError::Kind`] when the `__anw-kind` homogeneity guard fails.
+pub fn run(vault_root: &Path, raw_query: &str) -> Result<String, MergeCliError> {
+    let parsed = query::parse(raw_query).map_err(MergeCliError::Query)?;
+
+    let scan = vault::scan(vault_root);
+    if !scan.issues.is_empty() {
+        return Err(MergeCliError::Scan(scan.issues));
+    }
+
+    // The merge engine reads from a NoteStore exactly as the HTTP path does;
+    // a one-shot `replace` is the whole "index" this subcommand needs.
+    let store = NoteStore::new();
+    store.replace(scan.notes);
+
+    query::execute_merge(&store, &parsed)
+        .map_err(|MergeError::KindGuard(msg)| MergeCliError::Kind(msg))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::fs;
+    use std::path::Path;
+    use tempfile::TempDir;
+
+    fn write(root: &Path, rel: &str, body: &str) {
+        let p = root.join(rel);
+        if let Some(parent) = p.parent() {
+            fs::create_dir_all(parent).unwrap();
+        }
+        fs::write(p, body).unwrap();
+    }
+
+    #[test]
+    fn merges_bodies_with_source_markers() {
+        let tmp = TempDir::new().unwrap();
+        write(tmp.path(), "a.md", "---\nnum: 1\n---\nalpha\n");
+        write(tmp.path(), "b.md", "---\nnum: 2\n---\nbeta\n");
+        let out = run(tmp.path(), "").unwrap();
+        // Body is frontmatter-stripped; fragments join with a blank line and
+        // there is no trailing newline -- byte-identical to the HTTP body.
+        assert_eq!(
+            out,
+            "<!-- source: a.md -->\nalpha\n\n\n<!-- source: b.md -->\nbeta\n"
+        );
+    }
+
+    #[test]
+    fn order_desc_then_path_tiebreak() {
+        let tmp = TempDir::new().unwrap();
+        write(tmp.path(), "a.md", "---\nnum: 1\n---\nlow\n");
+        write(tmp.path(), "b.md", "---\nnum: 3\n---\nhigh\n");
+        write(tmp.path(), "c.md", "---\nnum: 2\n---\nmid\n");
+        let out = run(tmp.path(), "__anw-order=num:desc").unwrap();
+        let bodies: Vec<&str> = out
+            .lines()
+            .filter(|l| !l.starts_with("<!--") && !l.is_empty())
+            .collect();
+        assert_eq!(bodies, vec!["high", "mid", "low"]);
+    }
+
+    #[test]
+    fn empty_match_set_is_empty_string() {
+        let tmp = TempDir::new().unwrap();
+        write(tmp.path(), "a.md", "---\ntags: [x]\n---\nbody\n");
+        // Predicate matches nothing.
+        assert_eq!(run(tmp.path(), "tags=nope").unwrap(), "");
+    }
+
+    #[test]
+    fn empty_vault_is_empty_string() {
+        let tmp = TempDir::new().unwrap();
+        assert_eq!(run(tmp.path(), "").unwrap(), "");
+    }
+
+    #[test]
+    fn kind_guard_passes_when_uniform() {
+        let tmp = TempDir::new().unwrap();
+        write(tmp.path(), "a.md", "---\nkind: skill\n---\nA\n");
+        write(tmp.path(), "b.md", "---\nkind: skill\n---\nB\n");
+        assert!(run(tmp.path(), "__anw-kind=kind").is_ok());
+    }
+
+    #[test]
+    fn kind_guard_rejects_distinct_values_naming_offenders() {
+        let tmp = TempDir::new().unwrap();
+        write(tmp.path(), "a.md", "---\nkind: skill\n---\nA\n");
+        write(tmp.path(), "b.md", "---\nkind: note\n---\nB\n");
+        let err = run(tmp.path(), "__anw-kind=kind").unwrap_err();
+        let msg = err.render();
+        assert!(msg.contains("distinct values found"));
+        assert!(msg.contains("a.md"));
+        assert!(msg.contains("b.md"));
+    }
+
+    #[test]
+    fn kind_guard_rejects_missing_key() {
+        let tmp = TempDir::new().unwrap();
+        write(tmp.path(), "a.md", "---\nkind: skill\n---\nA\n");
+        write(tmp.path(), "b.md", "---\n---\nB\n");
+        let err = run(tmp.path(), "__anw-kind=kind").unwrap_err();
+        assert!(matches!(err, MergeCliError::Kind(_)));
+        assert!(err.render().contains("notes missing the key"));
+    }
+
+    #[test]
+    fn malformed_query_is_reported() {
+        let tmp = TempDir::new().unwrap();
+        write(tmp.path(), "a.md", "---\n---\nbody\n");
+        let err = run(tmp.path(), "x__bogus=1").unwrap_err();
+        assert!(matches!(err, MergeCliError::Query(_)));
+        // Non-empty stderr surface.
+        assert!(!err.render().is_empty());
+    }
+
+    #[test]
+    fn unparseable_frontmatter_is_a_scan_error() {
+        let tmp = TempDir::new().unwrap();
+        write(tmp.path(), "bad.md", "---\n:: :: ::\n---\n");
+        let err = run(tmp.path(), "").unwrap_err();
+        assert!(matches!(err, MergeCliError::Scan(_)));
+        assert!(err.render().contains("cannot read vault"));
+        assert!(err.render().contains("bad.md"));
+    }
+
+    #[test]
+    fn output_matches_http_engine_for_same_vault_and_query() {
+        // The shared-engine check: the CLI path and a directly-built store
+        // feeding execute_merge must produce the identical document.
+        let tmp = TempDir::new().unwrap();
+        write(tmp.path(), "a.md", "---\nnum: 2\n---\nA body\n");
+        write(tmp.path(), "b.md", "---\nnum: 1\n---\nB body\n");
+        let raw = "__anw-order=num:asc";
+
+        let cli = run(tmp.path(), raw).unwrap();
+
+        let scan = vault::scan(tmp.path());
+        let store = NoteStore::new();
+        store.replace(scan.notes);
+        let parsed = query::parse(raw).unwrap();
+        let direct = query::execute_merge(&store, &parsed).unwrap();
+
+        assert_eq!(cli, direct);
+    }
+}