diff --git a/codex-rs/Cargo.lock b/codex-rs/Cargo.lock
index 101219c32b..dbcdd74886 100644
--- a/codex-rs/Cargo.lock
+++ b/codex-rs/Cargo.lock
@@ -592,8 +592,9 @@ dependencies = [
  "dirs",
  "libc",
  "names",
- "nanoid",
  "nix 0.27.1",
+ "petname",
+ "rand 0.9.1",
  "serde",
  "serde_json",
  "sysinfo",
@@ -2085,15 +2086,6 @@ dependencies = [
  "rand 0.8.5",
 ]
 
-[[package]]
-name = "nanoid"
-version = "0.4.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3ffa00dec017b5b1a8b7cf5e2c008bfda1aa7e0697ac1508b491fdf2622fb4d8"
-dependencies = [
- "rand 0.8.5",
-]
-
 [[package]]
 name = "native-tls"
 version = "0.2.14"
@@ -2412,6 +2404,20 @@ dependencies = [
  "indexmap 2.9.0",
 ]
 
+[[package]]
+name = "petname"
+version = "2.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9cd31dcfdbbd7431a807ef4df6edd6473228e94d5c805e8cf671227a21bad068"
+dependencies = [
+ "anyhow",
+ "clap",
+ "itertools 0.13.0",
+ "proc-macro2",
+ "quote",
+ "rand 0.8.5",
+]
+
 [[package]]
 name = "phf_shared"
 version = "0.11.3"
diff --git a/codex-rs/session/Cargo.toml b/codex-rs/session/Cargo.toml
index 4263376ddb..9b8d29237d 100644
--- a/codex-rs/session/Cargo.toml
+++ b/codex-rs/session/Cargo.toml
@@ -33,7 +33,8 @@ sysinfo = "0.29"
 tabwriter = "1.3"
 names = { version = "0.14", default-features = false }
 nix = { version = "0.27", default-features = false, features = ["process", "signal", "term", "fs"] }
-nanoid = "0.4.0"
+petname = "2.0.2"
+rand = "0.9.1"
 
 # Re-use the codex-exec library for its CLI definition
 codex_exec = { package = "codex-exec", path = "../exec" }
diff --git a/codex-rs/session/src/cli.rs b/codex-rs/session/src/cli.rs
index 1909395aa0..41ac7d2de8 100644
--- a/codex-rs/session/src/cli.rs
+++ b/codex-rs/session/src/cli.rs
@@ -17,12 +17,13 @@ use chrono::SecondsFormat;
 use clap::Args;
 use clap::Parser;
 use clap::Subcommand;
-use nanoid::nanoid;
 
 // Platform-specific imports
 
 #[cfg(unix)]
 use codex_repl as _;
+use petname::Generator;
+use petname::Petnames;
 use serde::Serialize;
 
 /// A human-friendly representation of a byte count (e.g. 1.4M).
@@ -198,9 +199,17 @@ fn truncate_preview(p: &str) -> String {
     }
 }
 
+/// Generate a new unique session identifier.
+///
+/// We use the `petname` crate to create short, memorable names consisting of
+/// two random words separated by a dash (e.g. "autumn-panda").  In the rare
+/// event of a collision with an existing session directory we retry until we
+/// find an unused ID.
 fn generate_session_id() -> Result<String> {
+    let mut shortnames = Petnames::default();
+    shortnames.retain(|s| s.len() <= 5);
     loop {
-        let id = nanoid!(8);
+        let id = shortnames.generate_one(2, "-").context("failed to generate session ID")?;
         if !store::paths_for(&id)?.dir.exists() {
             return Ok(id);
         }