diff --git a/crates/plannotator-tui/src/cli.rs b/crates/plannotator-tui/src/cli.rs
index 594b863..c9f01c1 100644
--- a/crates/plannotator-tui/src/cli.rs
+++ b/crates/plannotator-tui/src/cli.rs
@@ -141,7 +141,7 @@ fn show_config() -> Result<()> {
 
 /// `plannotator-tui herdr open [PATH] [--placement P] [--deliver-to PANE]`.
 fn herdr_command(args: &[String]) -> Result<()> {
-    use crate::herdr::launch::{OpenArgs, plan, plan_last, process_info, run};
+    use crate::herdr::launch::{OpenArgs, agent_get, plan, plan_last, process_info, run};
     let sub = args.first().map(String::as_str);
     if sub == Some("pane") {
         return herdr_pane();
@@ -172,7 +172,8 @@ fn herdr_command(args: &[String]) -> Result<()> {
         let probe = plan(&env, &config, OpenArgs { path: None, ..open.clone() }, &cwd)?;
         let pane = probe.deliver.as_ref().map(|t| t.pane.clone()).or(probe.target_pane);
         let pane = pane.context("no agent pane to read: not focused on one and no --deliver-to")?;
-        plan_last(&env, &config, open, &cwd, &process_info(&env, &pane)?)?
+        let agent = agent_get(&env, &pane);
+        plan_last(&env, &config, open, &cwd, &process_info(&env, &pane)?, agent.as_deref())?
     } else {
         plan(&env, &config, open, &cwd)?
     };
@@ -186,6 +187,7 @@ fn herdr_pane() -> Result<()> {
         crate::last::run(&crate::last::LastOptions {
             host: env.host.clone(),
             pid: Some(pid),
+            session: env.session.clone(),
             pick: 25,
             ..crate::last::LastOptions::default()
         })
diff --git a/crates/plannotator-tui/src/herdr/context.rs b/crates/plannotator-tui/src/herdr/context.rs
index 7157730..f0767f8 100644
--- a/crates/plannotator-tui/src/herdr/context.rs
+++ b/crates/plannotator-tui/src/herdr/context.rs
@@ -49,6 +49,10 @@ pub(crate) struct HerdrEnv {
     pub(crate) message_pid: Option<u32>,
     /// `PLANNOTATOR_TUI_HOST`: which agent's transcript format to read.
     pub(crate) host: Option<String>,
+    /// `PLANNOTATOR_TUI_SESSION`: the agent's transcript path, when Herdr knew it.
+    pub(crate) session: Option<PathBuf>,
+    /// `PLANNOTATOR_TUI_SESSION_ID`: the agent's session id, for hosts without transcript files.
+    pub(crate) session_id: Option<String>,
 }
 
 impl HerdrEnv {
@@ -72,6 +76,8 @@ impl HerdrEnv {
             plugin_id: non_empty("HERDR_PLUGIN_ID"),
             message_pid: non_empty("PLANNOTATOR_TUI_MESSAGE_PID").and_then(|v| v.parse().ok()),
             host: non_empty("PLANNOTATOR_TUI_HOST"),
+            session: non_empty("PLANNOTATOR_TUI_SESSION").map(PathBuf::from),
+            session_id: non_empty("PLANNOTATOR_TUI_SESSION_ID"),
         }
     }
 
diff --git a/crates/plannotator-tui/src/herdr/launch.rs b/crates/plannotator-tui/src/herdr/launch.rs
index 69ddb18..010d4dd 100644
--- a/crates/plannotator-tui/src/herdr/launch.rs
+++ b/crates/plannotator-tui/src/herdr/launch.rs
@@ -36,6 +36,27 @@ pub(crate) struct Launch {
     pub(crate) plugin: String,
     /// Open an agent's last message instead of `file`: (pid, host label).
     pub(crate) message: Option<(u32, String)>,
+    /// The agent's session as Herdr reports it: a transcript path or a host-specific id.
+    pub(crate) session: Option<AgentSession>,
+}
+
+/// `agent_session` from `herdr agent get`: the exact transcript when Herdr knows it.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub(crate) enum AgentSession {
+    Path(String),
+    Id(String),
+}
+
+/// Parse `herdr agent get <pane>` JSON for its `agent_session`, when present.
+pub(crate) fn agent_session(agent_get_json: &str) -> Option<AgentSession> {
+    let json: serde_json::Value = serde_json::from_str(agent_get_json).ok()?;
+    let session = json.pointer("/result/agent/agent_session")?;
+    let value = session.get("value")?.as_str()?.to_owned();
+    match session.get("kind")?.as_str()? {
+        "path" => Some(AgentSession::Path(value)),
+        "id" => Some(AgentSession::Id(value)),
+        _ => None,
+    }
 }
 
 /// The agent process behind a pane, from `herdr pane process-info --pane <id>` JSON: the
@@ -80,6 +101,7 @@ pub(crate) fn plan_last(
     args: OpenArgs,
     cwd: &Path,
     process_info_json: &str,
+    agent_get_json: Option<&str>,
 ) -> Result<Launch> {
     let mut launch = plan(env, config, OpenArgs { path: None, ..args }, cwd)?;
     let pane = launch.deliver.as_ref().map(|t| t.pane.clone()).or_else(|| launch.target_pane.clone());
@@ -91,6 +113,7 @@ pub(crate) fn plan_last(
     };
     launch.file.clone_from(&launch.cwd);
     launch.message = Some(message);
+    launch.session = agent_get_json.and_then(agent_session);
     Ok(launch)
 }
 
@@ -181,6 +204,7 @@ pub(crate) fn plan(env: &HerdrEnv, config: &Config, args: OpenArgs, cwd: &Path)
         deliver,
         plugin: env.plugin_id.clone().unwrap_or_else(|| "plannotator-tui".to_owned()),
         message: None,
+        session: None,
     })
 }
 
@@ -211,6 +235,15 @@ pub(crate) fn argv(launch: &Launch) -> Vec<String> {
             out.extend(["--env".to_owned(), format!("PLANNOTATOR_TUI_MESSAGE_PID={pid}")]);
             out.extend(["--env".to_owned(), format!("PLANNOTATOR_TUI_HOST={host}")]);
             out.extend(["--env".to_owned(), format!("PLANNOTATOR_TUI_CWD={}", launch.cwd.display())]);
+            match &launch.session {
+                Some(AgentSession::Path(p)) => {
+                    out.extend(["--env".to_owned(), format!("PLANNOTATOR_TUI_SESSION={p}")]);
+                }
+                Some(AgentSession::Id(id)) => {
+                    out.extend(["--env".to_owned(), format!("PLANNOTATOR_TUI_SESSION_ID={id}")]);
+                }
+                None => {}
+            }
         }
         None => out.extend(["--env".to_owned(), format!("PLANNOTATOR_TUI_FILE={}", launch.file.display())]),
     }
@@ -235,6 +268,12 @@ pub(crate) fn process_info(env: &HerdrEnv, pane: &str) -> Result<String> {
     Ok(String::from_utf8_lossy(&output.stdout).into_owned())
 }
 
+/// `herdr agent get <pane>`, raw JSON; `None` when the pane has no agent Herdr can describe.
+pub(crate) fn agent_get(env: &HerdrEnv, pane: &str) -> Option<String> {
+    let output = Command::new(&env.bin).args(["agent", "get", pane]).output().ok()?;
+    output.status.success().then(|| String::from_utf8_lossy(&output.stdout).into_owned())
+}
+
 /// Run the launch through `bin`. Herdr's own stdout/stderr pass through.
 pub(crate) fn run(env: &HerdrEnv, launch: &Launch) -> Result<()> {
     if !env.in_herdr {
diff --git a/crates/plannotator-tui/src/herdr/launch/tests.rs b/crates/plannotator-tui/src/herdr/launch/tests.rs
index 07d5910..080058b 100644
--- a/crates/plannotator-tui/src/herdr/launch/tests.rs
+++ b/crates/plannotator-tui/src/herdr/launch/tests.rs
@@ -187,6 +187,7 @@ fn a_last_launch_carries_the_pid_and_host_instead_of_a_file() {
         OpenArgs::default(),
         Path::new("/"),
         PROCESS_INFO,
+        None,
     )
     .expect("plans");
     assert_eq!(launch.message, Some((91279, "claude".into())));
@@ -196,3 +197,47 @@ fn a_last_launch_carries_the_pid_and_host_instead_of_a_file() {
     assert!(args.contains(&"PLANNOTATOR_TUI_HOST=claude".to_owned()));
     assert!(!args.iter().any(|a| a.starts_with("PLANNOTATOR_TUI_FILE=")));
 }
+
+const AGENT_GET_PATH: &str = r#"{"id":"cli:agent:get","result":{"agent":{"agent":"omp","agent_session":{"agent":"omp","kind":"path","source":"herdr:omp","value":"~/.omp/agent/sessions/--w--/2026-08-29T01-00-00-000Z_0199.jsonl"},"pane_id":"w1:p1"},"type":"agent_info"}}"#;
+const AGENT_GET_ID: &str = r#"{"id":"cli:agent:get","result":{"agent":{"agent":"hermes","agent_session":{"agent":"hermes","kind":"id","source":"herdr:hermes","value":"sess_abc123"},"pane_id":"w1:p1"},"type":"agent_info"}}"#;
+
+#[test]
+fn herdrs_agent_session_is_passed_to_the_pane_as_a_path_or_an_id() {
+    assert_eq!(
+        agent_session(AGENT_GET_PATH),
+        Some(AgentSession::Path("~/.omp/agent/sessions/--w--/2026-08-29T01-00-00-000Z_0199.jsonl".into()))
+    );
+    assert_eq!(agent_session(AGENT_GET_ID), Some(AgentSession::Id("sess_abc123".into())));
+    assert_eq!(agent_session(r#"{"result":{"agent":{"agent":"pi"}}}"#), None);
+
+    let context = HerdrContext {
+        focused_pane_id: Some("w1:p1".into()),
+        focused_pane_agent: Some("omp".into()),
+        focused_pane_cwd: Some("/w".into()),
+        ..HerdrContext::default()
+    };
+    let launch = plan_last(
+        &env(None, Some(context.clone())),
+        &Config::default(),
+        OpenArgs::default(),
+        Path::new("/"),
+        &PROCESS_INFO.replace(r#""name":"claude""#, r#""name":"omp""#),
+        Some(AGENT_GET_PATH),
+    )
+    .expect("plans");
+    let args = argv(&launch);
+    assert!(args.iter().any(|a| a.starts_with("PLANNOTATOR_TUI_SESSION=~/.omp/agent/sessions/")), "{args:?}");
+    assert!(args.contains(&"PLANNOTATOR_TUI_HOST=omp".to_owned()));
+
+    let launch = plan_last(
+        &env(None, Some(context)),
+        &Config::default(),
+        OpenArgs::default(),
+        Path::new("/"),
+        PROCESS_INFO,
+        Some(AGENT_GET_ID),
+    )
+    .expect("plans");
+    let args = argv(&launch);
+    assert!(args.contains(&"PLANNOTATOR_TUI_SESSION_ID=sess_abc123".to_owned()), "{args:?}");
+}