diff --git a/src/commands/mod.rs b/src/commands/mod.rs
index 10d6ca1..8c16aa1 100644
--- a/src/commands/mod.rs
+++ b/src/commands/mod.rs
@@ -1,6 +1,7 @@
 pub mod auth;
 pub mod token;
 pub mod record;
+pub mod reply;
 pub mod sync;
 pub mod push;
 pub mod notify;
diff --git a/src/commands/notify.rs b/src/commands/notify.rs
index 98fac33..ad7f50e 100644
--- a/src/commands/notify.rs
+++ b/src/commands/notify.rs
@@ -113,15 +113,37 @@ pub async fn listen(interval_secs: u64, reasons: &[String]) -> Result<()> {
 
             // Output in chronological order (oldest first)
             for notif in new_items.iter().rev() {
+                // Build root/parent for reply threading
+                let root = if notif["record"]["reply"]["root"]["uri"].is_string() {
+                    serde_json::json!({
+                        "uri": notif["record"]["reply"]["root"]["uri"],
+                        "cid": notif["record"]["reply"]["root"]["cid"],
+                    })
+                } else {
+                    // This post is the root
+                    serde_json::json!({
+                        "uri": notif["uri"],
+                        "cid": notif["cid"],
+                    })
+                };
+
+                let parent = serde_json::json!({
+                    "uri": notif["uri"],
+                    "cid": notif["cid"],
+                });
+
                 let out = serde_json::json!({
                     "reason": notif["reason"],
                     "uri": notif["uri"],
+                    "cid": notif["cid"],
                     "author": {
                         "did": notif["author"]["did"],
                         "handle": notif["author"]["handle"],
                     },
                     "text": notif["record"]["text"],
                     "indexedAt": notif["indexedAt"],
+                    "root": root,
+                    "parent": parent,
                 });
                 writeln!(stdout, "{}", serde_json::to_string(&out)?)?;
                 stdout.flush()?;
diff --git a/src/commands/reply.rs b/src/commands/reply.rs
new file mode 100644
index 0000000..5f38842
--- /dev/null
+++ b/src/commands/reply.rs
@@ -0,0 +1,86 @@
+use anyhow::{Context, Result};
+use serde_json::Value;
+
+use super::auth;
+use crate::lexicons::com_atproto_repo;
+use crate::tid;
+use crate::types::{PutRecordRequest, PutRecordResponse};
+use crate::xrpc::XrpcClient;
+
+/// Reply to a post on ATProto.
+///
+/// `root_uri`, `root_cid`: thread root
+/// `parent_uri`, `parent_cid`: direct parent being replied to
+pub async fn reply(
+    text: &str,
+    root_uri: &str,
+    root_cid: &str,
+    parent_uri: &str,
+    parent_cid: &str,
+) -> Result<()> {
+    let session = auth::refresh_session().await?;
+    let pds = session.pds.as_deref().unwrap_or("bsky.social");
+    let client = XrpcClient::new(pds);
+
+    let now = chrono::Utc::now()
+        .format("%Y-%m-%dT%H:%M:%S%.3fZ")
+        .to_string();
+
+    let record = serde_json::json!({
+        "$type": "app.bsky.feed.post",
+        "text": text,
+        "reply": {
+            "root": {
+                "uri": root_uri,
+                "cid": root_cid,
+            },
+            "parent": {
+                "uri": parent_uri,
+                "cid": parent_cid,
+            },
+        },
+        "createdAt": now,
+    });
+
+    let rkey = tid::generate_tid();
+
+    let req = PutRecordRequest {
+        repo: session.did.clone(),
+        collection: "app.bsky.feed.post".to_string(),
+        rkey,
+        record,
+    };
+
+    let result: PutRecordResponse = client
+        .call(&com_atproto_repo::PUT_RECORD, &req, &session.access_jwt)
+        .await?;
+
+    let out = serde_json::json!({
+        "uri": result.uri,
+        "cid": result.cid,
+    });
+    println!("{}", serde_json::to_string_pretty(&out)?);
+
+    Ok(())
+}
+
+/// Reply from JSON input (stdin or argument).
+/// Expects fields: text, root.uri, root.cid, parent.uri, parent.cid
+pub async fn reply_json(json_str: &str, text: &str) -> Result<()> {
+    let v: Value = serde_json::from_str(json_str).context("Invalid JSON input")?;
+
+    let root_uri = v["root"]["uri"]
+        .as_str()
+        .context("missing root.uri")?;
+    let root_cid = v["root"]["cid"]
+        .as_str()
+        .context("missing root.cid")?;
+    let parent_uri = v["parent"]["uri"]
+        .as_str()
+        .context("missing parent.uri")?;
+    let parent_cid = v["parent"]["cid"]
+        .as_str()
+        .context("missing parent.cid")?;
+
+    reply(text, root_uri, root_cid, parent_uri, parent_cid).await
+}
diff --git a/src/main.rs b/src/main.rs
index cbd8b69..da63ce9 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -135,6 +135,27 @@ enum Commands {
         server: String,
     },
 
+    /// Reply to a post
+    Reply {
+        /// Reply text
+        text: String,
+        /// Parent post URI (at://...)
+        #[arg(long)]
+        uri: Option<String>,
+        /// Parent post CID
+        #[arg(long)]
+        cid: Option<String>,
+        /// Root post URI (defaults to parent if omitted)
+        #[arg(long)]
+        root_uri: Option<String>,
+        /// Root post CID (defaults to parent if omitted)
+        #[arg(long)]
+        root_cid: Option<String>,
+        /// JSON with root/parent info (from `notify listen` output)
+        #[arg(long)]
+        json: Option<String>,
+    },
+
     /// Chat with AI
     #[command(alias = "c")]
     Chat {
@@ -248,6 +269,19 @@ async fn main() -> Result<()> {
         Commands::Did { handle, server } => {
             commands::did::resolve(&handle, &server).await?;
         }
+        Commands::Reply { text, uri, cid, root_uri, root_cid, json } => {
+            if let Some(json_str) = json {
+                commands::reply::reply_json(&json_str, &text).await?;
+            } else {
+                let parent_uri = uri.as_deref()
+                    .expect("--uri is required (or use --json)");
+                let parent_cid = cid.as_deref()
+                    .expect("--cid is required (or use --json)");
+                let r_uri = root_uri.as_deref().unwrap_or(parent_uri);
+                let r_cid = root_cid.as_deref().unwrap_or(parent_cid);
+                commands::reply::reply(&text, r_uri, r_cid, parent_uri, parent_cid).await?;
+            }
+        }
         Commands::Chat { message, new } => {
             lms::chat::run(message.as_deref(), new).await?;
         }