diff --git a/crates/buzz-relay/src/handlers/event.rs b/crates/buzz-relay/src/handlers/event.rs
index 0190b36ee9..4cdcf8b2a8 100644
--- a/crates/buzz-relay/src/handlers/event.rs
+++ b/crates/buzz-relay/src/handlers/event.rs
@@ -1065,6 +1065,7 @@ mod tests {
                 CancellationToken::new(),
                 Arc::new(AtomicU8::new(0)),
                 Arc::new(Mutex::new(HashMap::new())),
+                3,
             );
             state.sub_registry.register(
                 conn_id,
diff --git a/desktop/scripts/check-file-sizes.mjs b/desktop/scripts/check-file-sizes.mjs
index cc6050e878..556046b1ed 100644
--- a/desktop/scripts/check-file-sizes.mjs
+++ b/desktop/scripts/check-file-sizes.mjs
@@ -41,10 +41,11 @@ const overrides = new Map([
   ["src-tauri/src/managed_agents/runtime.rs", 1953],
   ["src-tauri/src/managed_agents/personas.rs", 1080],
   ["src-tauri/src/managed_agents/persona_card.rs", 1050],
-  // applyWorkspace reposDir parameter threaded through the Tauri invoke for
-  // configurable repos_dir — a 3-line overage from load-bearing parameter
-  // plumbing, not generic debt growth. Approved override; still queued to split.
-  ["src/shared/api/tauri.ts", 1198],
+  // applyWorkspace reposDir parameter plus the validateReposDir binding,
+  // threaded through Tauri invokes for configurable repos_dir — a 4-line
+  // overage from load-bearing parameter plumbing, not generic debt growth.
+  // Approved override; still queued to split.
+  ["src/shared/api/tauri.ts", 1199],
   ["src-tauri/src/nostr_convert.rs", 1126],
   ["src/shared/api/relayClientSession.ts", 1022],
   ["src-tauri/src/migration.rs", 1295],
diff --git a/desktop/src-tauri/src/commands/workspace.rs b/desktop/src-tauri/src/commands/workspace.rs
index 7c3529fc1e..7c0e4b8327 100644
--- a/desktop/src-tauri/src/commands/workspace.rs
+++ b/desktop/src-tauri/src/commands/workspace.rs
@@ -3,7 +3,10 @@ use serde::Serialize;
 use tauri::{AppHandle, Emitter, State};
 
 use crate::app_state::AppState;
-use crate::managed_agents::{ensure_repos_symlink, nest_dir, try_regenerate_nest};
+use crate::managed_agents::{
+    effective_repos_dir, ensure_repos_symlink, nest_dir, try_regenerate_nest,
+    write_persisted_repos_dir,
+};
 use crate::relay;
 
 #[derive(Serialize)]
@@ -23,18 +26,36 @@ pub fn get_active_workspace(state: State<'_, AppState>) -> Result<ActiveWorkspac
     })
 }
 
+/// Validate a candidate `repos_dir` without mutating the filesystem.
+///
+/// The Add/Edit workspace dialogs call this on submit to block Save on a bad
+/// path, so a typo never reaches `apply_workspace`. Reuses the same
+/// `validate_repos_dir` the boot/apply path uses — one source of truth for
+/// "what's a valid repos dir". An empty/whitespace value clears the override
+/// and is valid. `Err` carries the human-readable reason for inline display.
+#[tauri::command]
+pub fn validate_repos_dir(dir: String) -> Result<(), String> {
+    let trimmed = dir.trim();
+    if trimmed.is_empty() {
+        return Ok(());
+    }
+    let nest = nest_dir().ok_or("cannot resolve home directory for nest")?;
+    crate::managed_agents::validate_repos_dir(&nest, trimmed).map(|_| ())
+}
+
 /// Apply a workspace's configuration to the backend session.
 ///
 /// Called by the frontend on app init (after reload) to configure the
 /// Tauri backend with the selected workspace's relay URL, keys, and repos
 /// directory.
 ///
-/// Validation runs before any state mutation: an invalid `repos_dir` (bad
-/// path) rejects cleanly with nothing applied. The `REPOS` symlink itself is
-/// a filesystem *side-effect* — its failure (e.g. a non-empty real `REPOS`
-/// refusing a downgrade, or a renamed external target on a later launch) is
-/// non-fatal: relay/keys still apply, the command returns `Ok`, and a
-/// `repos-dir-error` event surfaces the failure to the frontend.
+/// A bad `repos_dir` is non-fatal: relay/keys always apply (the relay is the
+/// active workspace's own choice — orthogonal to the filesystem repos dir),
+/// the bad value is NOT persisted (so the next boot starts clean), the
+/// `REPOS` symlink is skipped (REPOS stays a real dir), a `repos-dir-error`
+/// event surfaces the reason, and the command returns `Ok`. The dialogs
+/// already block a bad path at Save (`validate_repos_dir`); this fallback only
+/// catches a value that went bad after save (deleted dir, unmounted volume).
 #[tauri::command]
 pub fn apply_workspace(
     relay_url: String,
@@ -51,23 +72,25 @@ pub fn apply_workspace(
         None => None,
     };
 
-    // Normalize repos_dir to a trimmed non-empty value. `None`/empty clears
-    // the override (REPOS falls back to a real dir). A bad path is rejected
-    // here — before any mutation — so the dialog sees a clean Err.
-    let repos_dir = repos_dir
-        .map(|s| s.trim().to_string())
-        .filter(|s| !s.is_empty());
-    if let Some(dir) = repos_dir.as_deref() {
-        let nest = nest_dir().ok_or("cannot resolve home directory for nest")?;
-        // Validate without mutating the filesystem. Keeps the command's
-        // "validate-first, nothing below can fail" contract honest. Also emit
-        // the error so it surfaces even at the init call site (which swallows
-        // the returned Err to console for the relay/keys path).
-        if let Err(error) = crate::managed_agents::validate_repos_dir(&nest, dir) {
-            let _ = app.emit("repos-dir-error", error.clone());
-            return Err(error);
-        }
-    }
+    // Decide the effective repos_dir from the candidate. A bad path does NOT
+    // reject — it is treated as if no override were set: relay/keys still
+    // apply, the bad value is not persisted, and a `repos-dir-error` surfaces
+    // the reason. Persisting a bad path would make every later boot read it,
+    // fail to resolve the symlink, and silently skip agent restore. One
+    // validate (inside `effective_repos_dir`) drives both the emit and the
+    // persisted value. `nest` is resolved softly: when absent there is nothing
+    // to persist or symlink, and relay/keys must still apply unconditionally.
+    let nest = nest_dir();
+    let effective_repos_dir = match nest.as_deref() {
+        Some(nest) => match effective_repos_dir(nest, repos_dir.as_deref()) {
+            Ok(value) => value,
+            Err(error) => {
+                let _ = app.emit("repos-dir-error", error);
+                None
+            }
+        },
+        None => None,
+    };
 
     // ── Apply all state changes (nothing below can fail) ──────────────────
     {
@@ -81,11 +104,20 @@ pub fn apply_workspace(
     }
 
     // ── Filesystem side-effect (non-fatal) ────────────────────────────────
-    // Re-point REPOS to match repos_dir. Failure here (downgrade refused,
-    // external target gone) must NOT fail the command — relay/keys are already
-    // applied. Surface it via a `repos-dir-error` event the frontend toasts.
-    if let Some(nest) = nest_dir() {
-        if let Err(error) = ensure_repos_symlink(&nest, repos_dir.as_deref()) {
+    // Persist the *effective* repos_dir (None when the candidate failed
+    // validation) for the backend to read at boot, then re-point REPOS to
+    // match. Persisting first makes the dotfile authoritative even if the
+    // symlink apply fails here (e.g. a non-empty real REPOS): the next boot
+    // reads the persisted value and resolves the symlink before any agent can
+    // clone into REPOS. A bad candidate persists `None`, so the next boot is
+    // clean and agent restore proceeds. Failure of either must NOT fail the
+    // command — relay/keys are already applied. Surface symlink errors via
+    // `repos-dir-error`.
+    if let Some(nest) = nest.as_deref() {
+        if let Err(error) = write_persisted_repos_dir(nest, effective_repos_dir.as_deref()) {
+            eprintln!("buzz-desktop: persist repos dir failed: {error}");
+        }
+        if let Err(error) = ensure_repos_symlink(nest, effective_repos_dir.as_deref()) {
             eprintln!("buzz-desktop: repos dir setup failed: {error}");
             let _ = app.emit("repos-dir-error", error);
         }
diff --git a/desktop/src-tauri/src/lib.rs b/desktop/src-tauri/src/lib.rs
index d9b26841ff..8cf55b13e3 100644
--- a/desktop/src-tauri/src/lib.rs
+++ b/desktop/src-tauri/src/lib.rs
@@ -586,6 +586,21 @@ pub fn run() {
                 eprintln!("buzz-desktop: failed to create nest: {error}");
             }
 
+            // Resolve the REPOS symlink from the persisted repos_dir BEFORE
+            // agents are restored below, and decide whether restore is safe.
+            // The frontend's apply_workspace runs only after React mounts —
+            // later than the async agent restore — so without this an agent
+            // could clone into the empty real REPOS dir, and once REPOS is
+            // non-empty ensure_repos_symlink refuses forever. resolve_repos_at_boot
+            // fails closed: if a repos_dir was configured but its symlink could
+            // not be resolved (transiently unavailable external volume), it
+            // returns false so we skip restore this launch rather than let an
+            // agent clone into the wrong REPOS. See managed_agents::repos.
+            let restore_agents = match managed_agents::nest_dir() {
+                Some(nest) => managed_agents::resolve_repos_at_boot(&nest),
+                None => true,
+            };
+
             // Carry the agent's knowledge from the legacy nest (~/.sprout) into
             // the live nest (~/.buzz) after it exists. Must run after
             // ensure_nest() so the destination is present. Non-fatal.
@@ -637,14 +652,20 @@ pub fn run() {
             }
 
             // Keep launch-time agent restoration off the synchronous setup path
-            // so the frontend can mount and reveal the window promptly.
-            tauri::async_runtime::spawn(async move {
-                if let Err(error) =
-                    restore_managed_agents_on_launch(&app_handle, shutdown_started.as_ref()).await
-                {
-                    eprintln!("buzz-desktop: failed to restore managed agents: {error}");
-                }
-            });
+            // so the frontend can mount and reveal the window promptly. Gated on
+            // the boot-time repos symlink result (see restore_agents above):
+            // skip when a configured repos_dir could not be resolved, so no
+            // agent clones into a REPOS that isn't the user's target.
+            if restore_agents {
+                tauri::async_runtime::spawn(async move {
+                    if let Err(error) =
+                        restore_managed_agents_on_launch(&app_handle, shutdown_started.as_ref())
+                            .await
+                    {
+                        eprintln!("buzz-desktop: failed to restore managed agents: {error}");
+                    }
+                });
+            }
 
             // Periodic sweep: reap orphaned agents from dead instances every 60s.
             // Catches agents that escaped both the Justfile trap and boot-time
@@ -844,6 +865,7 @@ pub fn run() {
             confirm_pairing_sas,
             cancel_pairing,
             apply_workspace,
+            validate_repos_dir,
             get_active_workspace,
             set_prevent_sleep_active,
             get_agent_memory,
diff --git a/desktop/src-tauri/src/managed_agents/mod.rs b/desktop/src-tauri/src/managed_agents/mod.rs
index 18d6af2770..ca996c96a4 100644
--- a/desktop/src-tauri/src/managed_agents/mod.rs
+++ b/desktop/src-tauri/src/managed_agents/mod.rs
@@ -27,7 +27,10 @@ pub use personas::*;
 pub use process_lifecycle::*;
 #[cfg(feature = "mesh-llm")]
 pub use relay_mesh::*;
-pub use repos::{ensure_repos_symlink, validate_repos_dir};
+pub use repos::{
+    effective_repos_dir, ensure_repos_symlink, resolve_repos_at_boot, validate_repos_dir,
+    write_persisted_repos_dir,
+};
 pub use restore::*;
 pub use runtime::*;
 pub use storage::*;
diff --git a/desktop/src-tauri/src/managed_agents/repos.rs b/desktop/src-tauri/src/managed_agents/repos.rs
index dd81950c40..1228ad74cb 100644
--- a/desktop/src-tauri/src/managed_agents/repos.rs
+++ b/desktop/src-tauri/src/managed_agents/repos.rs
@@ -164,6 +164,117 @@ pub fn ensure_repos_setup_default(nest_root: &Path) -> Result<(), String> {
     ensure_repos_symlink(nest_root, None)
 }
 
+/// Decide what `repos_dir` `apply_workspace` should persist and symlink for a
+/// candidate value, running the single source-of-truth [`validate_repos_dir`].
+///
+/// - **`None`/empty candidate** → `Ok(None)`: no override; `REPOS` reverts to a
+///   real in-nest directory.
+/// - **valid candidate** → `Ok(Some(raw_trimmed))`: persist the *raw* trimmed
+///   string (not the canonical path — persisting canonical would drift the
+///   symlink target on `..`/symlinked-ancestor paths).
+/// - **invalid candidate** → `Err(reason)`: the caller must persist `None`
+///   (clearing the override so the next boot resolves clean and agent restore
+///   proceeds) and surface `reason` to the user. Returning `Err` rather than
+///   silently `Ok(None)` lets the caller emit the human-readable cause.
+///
+/// One validate call drives both the persisted value and the error: a bad path
+/// is never persisted, so it can never silently skip agent restore on a later
+/// boot. Pure (no FS mutation, no emit) so the persist decision is unit-tested.
+pub fn effective_repos_dir(
+    nest_root: &Path,
+    candidate: Option<&str>,
+) -> Result<Option<String>, String> {
+    let Some(trimmed) = candidate.map(str::trim).filter(|s| !s.is_empty()) else {
+        return Ok(None);
+    };
+    validate_repos_dir(nest_root, trimmed).map(|_| Some(trimmed.to_string()))
+}
+
+/// Filename of the dotfile persisting the active workspace's `repos_dir`.
+const REPOS_DIR_FILE: &str = ".repos-dir";
+
+/// Read the persisted `repos_dir` from `nest_root/.repos-dir`.
+///
+/// Returns the trimmed value, or `None` when the file is absent, unreadable,
+/// or empty. This is the backend's sole knowledge of `repos_dir` at boot —
+/// the frontend persists it via [`write_persisted_repos_dir`] on every
+/// `apply_workspace`, so [`resolve_repos_at_boot`] can resolve the `REPOS`
+/// symlink before any agent is restored.
+fn read_persisted_repos_dir(nest_root: &Path) -> Option<String> {
+    fs::read_to_string(nest_root.join(REPOS_DIR_FILE))
+        .ok()
+        .map(|s| s.trim().to_string())
+        .filter(|s| !s.is_empty())
+}
+
+/// Persist the active workspace's `repos_dir` to `nest_root/.repos-dir`.
+///
+/// Writes the trimmed value (one line). A `None`/empty value clears the
+/// override by removing the file, so a later boot reverts `REPOS` to a real
+/// in-nest directory. Removing an absent file is not an error. Mirrors the
+/// `.nest-agents-version` dotfile pattern.
+pub fn write_persisted_repos_dir(nest_root: &Path, repos_dir: Option<&str>) -> Result<(), String> {
+    let path = nest_root.join(REPOS_DIR_FILE);
+    match repos_dir.map(str::trim).filter(|s| !s.is_empty()) {
+        Some(value) => fs::write(&path, format!("{value}\n"))
+            .map_err(|e| format!("write {}: {e}", path.display())),
+        None => match fs::remove_file(&path) {
+            Ok(()) => Ok(()),
+            Err(e) if e.kind() == io::ErrorKind::NotFound => Ok(()),
+            Err(e) => Err(format!("remove {}: {e}", path.display())),
+        },
+    }
+}
+
+/// Decide whether launch-time agent restore is safe given the boot symlink
+/// outcome. Fails CLOSED: when a `repos_dir` was configured but its symlink
+/// could not be resolved, restoring agents would let one clone into the empty
+/// real `REPOS` that `ensure_nest` provisioned — the wrong location — and once
+/// it is non-empty [`ensure_repos_symlink`] refuses forever, permanently
+/// re-triggering the race. Skipping restore is recoverable on the next boot
+/// once the external target is reachable; a misplaced clone is not.
+///
+/// The no-`repos_dir` case (`persisted_present == false`) is always safe: the
+/// real in-nest `REPOS` default is exactly where clones belong.
+fn should_restore_agents(persisted_present: bool, symlink_result: &Result<(), String>) -> bool {
+    !(persisted_present && symlink_result.is_err())
+}
+
+/// Resolve the `REPOS` symlink at boot from the persisted `repos_dir` and
+/// report whether agent restore is safe to proceed.
+///
+/// Runs in the synchronous setup hook, after `ensure_nest` and before the
+/// async agent restore is spawned, so `REPOS` is the user's configured symlink
+/// before any agent can clone. Logs on failure (no toast path exists
+/// pre-mount) and returns the fail-closed [`should_restore_agents`] decision.
+pub fn resolve_repos_at_boot(nest_root: &Path) -> bool {
+    let persisted = read_persisted_repos_dir(nest_root);
+    let symlink_result = ensure_repos_symlink(nest_root, persisted.as_deref());
+    if let Err(error) = &symlink_result {
+        eprintln!("buzz-desktop: repos dir setup failed at boot: {error}");
+    }
+    let restore = should_restore_agents(persisted.is_some(), &symlink_result);
+    // Log the resolved outcome on success so a healthy boot is observable (the
+    // Err/skip branches already log; previously success was silent).
+    if symlink_result.is_ok() {
+        match persisted.as_deref() {
+            Some(dir) => eprintln!(
+                "buzz-desktop: repos dir resolved at boot — REPOS symlinked to configured `{dir}`"
+            ),
+            None => eprintln!(
+                "buzz-desktop: repos dir resolved at boot — no configured override, REPOS is the default real dir"
+            ),
+        }
+    }
+    if !restore {
+        eprintln!(
+            "buzz-desktop: skipping agent restore — configured repos_dir `{}` could not be resolved at boot; will retry on next launch",
+            persisted.as_deref().unwrap_or_default()
+        );
+    }
+    restore
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -383,6 +494,284 @@ mod tests {
         );
     }
 
+    // ── persisted repos_dir dotfile ───────────────────────────────────────
+
+    #[test]
+    fn persisted_repos_dir_roundtrips_write_read_clear() {
+        let tmp = tempfile::tempdir().unwrap();
+        let root = tmp.path().join(".buzz");
+        fs::create_dir_all(&root).unwrap();
+
+        assert_eq!(read_persisted_repos_dir(&root), None, "absent → None");
+
+        write_persisted_repos_dir(&root, Some("  /Users/me/Development  ")).unwrap();
+        assert_eq!(
+            read_persisted_repos_dir(&root).as_deref(),
+            Some("/Users/me/Development"),
+            "value is trimmed on write/read"
+        );
+
+        write_persisted_repos_dir(&root, None).unwrap();
+        assert_eq!(read_persisted_repos_dir(&root), None, "cleared → None");
+        assert!(
+            !root.join(".repos-dir").exists(),
+            "clearing removes the dotfile"
+        );
+    }
+
+    #[test]
+    fn persisted_repos_dir_empty_value_clears() {
+        let tmp = tempfile::tempdir().unwrap();
+        let root = tmp.path().join(".buzz");
+        fs::create_dir_all(&root).unwrap();
+        write_persisted_repos_dir(&root, Some("/Users/me/Development")).unwrap();
+
+        write_persisted_repos_dir(&root, Some("   ")).unwrap();
+        assert_eq!(
+            read_persisted_repos_dir(&root),
+            None,
+            "a whitespace-only value clears the override"
+        );
+    }
+
+    #[test]
+    fn persisted_repos_dir_clear_when_absent_is_ok() {
+        let tmp = tempfile::tempdir().unwrap();
+        let root = tmp.path().join(".buzz");
+        fs::create_dir_all(&root).unwrap();
+
+        write_persisted_repos_dir(&root, None).expect("clearing an absent dotfile is not an error");
+    }
+
+    #[cfg(unix)]
+    #[test]
+    fn boot_resolves_symlink_from_persisted_value_into_empty_repos() {
+        // Mirrors the boot sequence: ensure_nest leaves REPOS an empty real
+        // dir, then the setup hook reads the persisted value and symlinks.
+        let tmp = tempfile::tempdir().unwrap();
+        let root = tmp.path().join(".buzz");
+        fs::create_dir_all(root.join("REPOS")).unwrap();
+        let external = tmp.path().join("Development");
+        fs::create_dir_all(&external).unwrap();
+
+        write_persisted_repos_dir(&root, Some(external.to_str().unwrap())).unwrap();
+        let persisted = read_persisted_repos_dir(&root);
+        ensure_repos_symlink(&root, persisted.as_deref()).unwrap();
+
+        let repos = root.join("REPOS");
+        assert!(
+            repos.symlink_metadata().unwrap().file_type().is_symlink(),
+            "boot must convert the empty real REPOS into a symlink"
+        );
+        assert_eq!(repos.read_link().unwrap(), external.canonicalize().unwrap());
+    }
+
+    #[cfg(unix)]
+    #[test]
+    fn boot_leaves_already_correct_symlink_untouched() {
+        let tmp = tempfile::tempdir().unwrap();
+        let root = tmp.path().join(".buzz");
+        fs::create_dir_all(&root).unwrap();
+        let external = tmp.path().join("Development");
+        fs::create_dir_all(&external).unwrap();
+
+        write_persisted_repos_dir(&root, Some(external.to_str().unwrap())).unwrap();
+        // First boot converts; second boot must be a noop.
+        let persisted = read_persisted_repos_dir(&root);
+        ensure_repos_symlink(&root, persisted.as_deref()).unwrap();
+        ensure_repos_symlink(&root, persisted.as_deref()).unwrap();
+
+        let repos = root.join("REPOS");
+        assert!(repos.symlink_metadata().unwrap().file_type().is_symlink());
+        assert_eq!(repos.read_link().unwrap(), external.canonicalize().unwrap());
+    }
+
+    #[cfg(unix)]
+    #[test]
+    fn boot_with_cleared_value_reverts_symlink_to_real_dir() {
+        let tmp = tempfile::tempdir().unwrap();
+        let root = tmp.path().join(".buzz");
+        fs::create_dir_all(&root).unwrap();
+        let external = tmp.path().join("Development");
+        fs::create_dir_all(&external).unwrap();
+        fs::write(external.join("KEEP.md"), "data").unwrap();
+
+        // Configure, then clear the field.
+        write_persisted_repos_dir(&root, Some(external.to_str().unwrap())).unwrap();
+        ensure_repos_symlink(&root, read_persisted_repos_dir(&root).as_deref()).unwrap();
+        write_persisted_repos_dir(&root, None).unwrap();
+
+        // Next boot reads None and reverts REPOS to a real in-nest dir.
+        ensure_repos_symlink(&root, read_persisted_repos_dir(&root).as_deref()).unwrap();
+
+        let repos = root.join("REPOS");
+        assert!(
+            !repos.symlink_metadata().unwrap().file_type().is_symlink(),
+            "clearing the persisted value reverts REPOS to a real dir"
+        );
+        assert!(
+            external.join("KEEP.md").exists(),
+            "reverting must not touch the external target's contents"
+        );
+    }
+
+    #[cfg(unix)]
+    #[test]
+    fn effective_repos_dir_drives_persisted_dotfile_for_all_three_cases() {
+        // Pins the CRITICAL persist decision on `.repos-dir` CONTENTS, not just
+        // a return value: a bad path must clear the dotfile so the next boot's
+        // `should_restore_agents(false, _)` restores agents (the regression
+        // this hardening fixes). Drives each case through the same
+        // effective→persist path `apply_workspace` uses.
+        let tmp = tempfile::tempdir().unwrap();
+        let root = tmp.path().join(".buzz");
+        fs::create_dir_all(&root).unwrap();
+        let good = tmp.path().join("Development");
+        fs::create_dir_all(&good).unwrap();
+        let good_str = good.to_str().unwrap();
+
+        // Pre-seed a value so each case proves it overwrites/clears, not just
+        // that an absent dotfile stays absent.
+        let seed = |root: &Path| write_persisted_repos_dir(root, Some(good_str)).unwrap();
+        let persist = |root: &Path, candidate: Option<&str>| {
+            let effective = effective_repos_dir(root, candidate);
+            // Mirror apply_workspace: Err clears the override (persist None).
+            let to_persist = effective.unwrap_or(None);
+            write_persisted_repos_dir(root, to_persist.as_deref()).unwrap();
+        };
+
+        // Bad path → Err → dotfile cleared (the CRITICAL).
+        seed(&root);
+        persist(&root, Some("/no/such/dir/here"));
+        assert_eq!(
+            read_persisted_repos_dir(&root),
+            None,
+            "a bad repos_dir must clear `.repos-dir` so the next boot restores agents"
+        );
+
+        // Good path → Ok(Some(raw)) → dotfile holds the raw trimmed value.
+        persist(&root, Some(&format!("  {good_str}  ")));
+        assert_eq!(
+            read_persisted_repos_dir(&root).as_deref(),
+            Some(good_str),
+            "a valid repos_dir must persist the raw trimmed path (not the canonical path)"
+        );
+
+        // Empty/whitespace → Ok(None) → dotfile cleared.
+        seed(&root);
+        persist(&root, Some("   "));
+        assert_eq!(
+            read_persisted_repos_dir(&root),
+            None,
+            "an empty repos_dir clears the override"
+        );
+
+        // None candidate → Ok(None) → dotfile cleared.
+        seed(&root);
+        persist(&root, None);
+        assert_eq!(
+            read_persisted_repos_dir(&root),
+            None,
+            "no repos_dir clears the override"
+        );
+    }
+
+    // ── resolve_repos_at_boot (boot sequence + fail-closed gate) ──────────
+
+    #[cfg(unix)]
+    #[test]
+    fn resolve_repos_at_boot_converts_empty_real_repos_and_allows_restore() {
+        // Drives the real boot sequence: ensure_repos_setup_default (called by
+        // ensure_nest) provisions REPOS as an empty real dir, then the setup
+        // hook calls resolve_repos_at_boot. Asserts the convert happens at that
+        // position and restore is allowed.
+        let tmp = tempfile::tempdir().unwrap();
+        let root = tmp.path().join(".buzz");
+        fs::create_dir_all(&root).unwrap();
+        let external = tmp.path().join("Development");
+        fs::create_dir_all(&external).unwrap();
+        write_persisted_repos_dir(&root, Some(external.to_str().unwrap())).unwrap();
+
+        ensure_repos_setup_default(&root).unwrap();
+        let repos = root.join("REPOS");
+        assert!(
+            repos.is_dir() && !repos.symlink_metadata().unwrap().file_type().is_symlink(),
+            "ensure_nest provisions REPOS as an empty real dir before the boot resolve"
+        );
+
+        let restore = resolve_repos_at_boot(&root);
+
+        assert!(restore, "restore proceeds when the symlink resolves");
+        assert!(
+            repos.symlink_metadata().unwrap().file_type().is_symlink(),
+            "boot resolve converts the empty real REPOS into the configured symlink"
+        );
+        assert_eq!(repos.read_link().unwrap(), external.canonicalize().unwrap());
+    }
+
+    #[cfg(unix)]
+    #[test]
+    fn resolve_repos_at_boot_fails_closed_when_target_unresolvable() {
+        // Persisted repos_dir whose target does not exist at boot (transiently
+        // unavailable external volume) → ensure_repos_symlink Errs. Restore must
+        // be skipped and REPOS left as the empty real dir, never the symlink, so
+        // no agent clones into the wrong place.
+        let tmp = tempfile::tempdir().unwrap();
+        let root = tmp.path().join(".buzz");
+        fs::create_dir_all(&root).unwrap();
+        let missing = tmp.path().join("not-mounted-yet");
+        write_persisted_repos_dir(&root, Some(missing.to_str().unwrap())).unwrap();
+        ensure_repos_setup_default(&root).unwrap();
+
+        let restore = resolve_repos_at_boot(&root);
+
+        assert!(
+            !restore,
+            "restore must be skipped when a configured repos_dir cannot resolve at boot"
+        );
+        let repos = root.join("REPOS");
+        assert!(
+            !repos.symlink_metadata().unwrap().file_type().is_symlink(),
+            "REPOS must not become a symlink to an unresolved target"
+        );
+    }
+
+    #[cfg(unix)]
+    #[test]
+    fn resolve_repos_at_boot_allows_restore_with_no_repos_dir() {
+        // No configured repos_dir → the real in-nest REPOS default is correct,
+        // restore proceeds normally (the fail-closed gate must not fire here).
+        let tmp = tempfile::tempdir().unwrap();
+        let root = tmp.path().join(".buzz");
+        fs::create_dir_all(&root).unwrap();
+        ensure_repos_setup_default(&root).unwrap();
+
+        assert!(
+            resolve_repos_at_boot(&root),
+            "restore proceeds when no repos_dir is configured"
+        );
+    }
+
+    #[test]
+    fn should_restore_agents_only_blocks_configured_unresolved_boot() {
+        assert!(
+            should_restore_agents(false, &Ok(())),
+            "no repos_dir, symlink ok → restore"
+        );
+        assert!(
+            should_restore_agents(false, &Err("boom".into())),
+            "no repos_dir → real-dir default is correct even on Err → restore"
+        );
+        assert!(
+            should_restore_agents(true, &Ok(())),
+            "configured repos_dir resolved → restore"
+        );
+        assert!(
+            !should_restore_agents(true, &Err("boom".into())),
+            "configured repos_dir unresolved → fail closed, skip restore"
+        );
+    }
+
     /// Test helper: canonicalize a path, creating it as a directory first.
     #[cfg(unix)]
     trait CanonicalizeOrMake {
diff --git a/desktop/src/features/workspaces/ui/AddWorkspaceDialog.tsx b/desktop/src/features/workspaces/ui/AddWorkspaceDialog.tsx
index 2c402664de..421c4c900b 100644
--- a/desktop/src/features/workspaces/ui/AddWorkspaceDialog.tsx
+++ b/desktop/src/features/workspaces/ui/AddWorkspaceDialog.tsx
@@ -6,6 +6,7 @@ import {
   expandTilde,
   normalizeRelayUrl,
 } from "@/features/workspaces/workspaceStorage";
+import { validateReposDir } from "@/shared/api/tauri";
 import { Button } from "@/shared/ui/button";
 import {
   Dialog,
@@ -31,6 +32,7 @@ export function AddWorkspaceDialog({
   const [relayUrl, setRelayUrl] = React.useState("");
   const [token, setToken] = React.useState("");
   const [reposDir, setReposDir] = React.useState("");
+  const [reposDirError, setReposDirError] = React.useState<string | null>(null);
 
   const handleClose = React.useCallback(() => {
     onOpenChange(false);
@@ -38,6 +40,7 @@ export function AddWorkspaceDialog({
     setRelayUrl("");
     setToken("");
     setReposDir("");
+    setReposDirError(null);
   }, [onOpenChange]);
 
   const handleSubmit = React.useCallback(
@@ -48,8 +51,16 @@ export function AddWorkspaceDialog({
       }
 
       // Expand `~` before save — the backend rejects tilde paths. Empty input
-      // resolves to `undefined` so REPOS keeps its default location.
+      // resolves to `undefined` so REPOS keeps its default location. Validate
+      // the expanded value (the bytes the backend canonicalizes) before save
+      // so a bad path is caught here instead of bricking a later boot.
       const expandedReposDir = await expandTilde(reposDir);
+      try {
+        await validateReposDir(expandedReposDir ?? "");
+      } catch (error) {
+        setReposDirError(String(error));
+        return;
+      }
 
       const workspace: Workspace = {
         id: crypto.randomUUID(),
@@ -144,11 +155,17 @@ export function AddWorkspaceDialog({
             </label>
             <Input
               id="ws-repos-dir"
-              onChange={(e) => setReposDir(e.target.value)}
+              onChange={(e) => {
+                setReposDir(e.target.value);
+                setReposDirError(null);
+              }}
               placeholder="~/Development"
               type="text"
               value={reposDir}
             />
+            {reposDirError ? (
+              <p className="text-xs text-destructive">{reposDirError}</p>
+            ) : null}
             <p className="text-xs text-muted-foreground">
               Point the agent's <code>REPOS</code> directory at an existing
               folder so agents work in your local checkouts. Leave blank to use
diff --git a/desktop/src/features/workspaces/ui/EditWorkspaceDialog.tsx b/desktop/src/features/workspaces/ui/EditWorkspaceDialog.tsx
index 8dacc030cd..88fe4017e5 100644
--- a/desktop/src/features/workspaces/ui/EditWorkspaceDialog.tsx
+++ b/desktop/src/features/workspaces/ui/EditWorkspaceDialog.tsx
@@ -5,6 +5,7 @@ import {
   expandTilde,
   normalizeRelayUrl,
 } from "@/features/workspaces/workspaceStorage";
+import { validateReposDir } from "@/shared/api/tauri";
 import { Button } from "@/shared/ui/button";
 import {
   Dialog,
@@ -41,6 +42,7 @@ export function EditWorkspaceDialog({
   const [relayUrl, setRelayUrl] = React.useState("");
   const [token, setToken] = React.useState("");
   const [reposDir, setReposDir] = React.useState("");
+  const [reposDirError, setReposDirError] = React.useState<string | null>(null);
 
   // Sync form state when the dialog opens with a workspace
   React.useEffect(() => {
@@ -49,6 +51,7 @@ export function EditWorkspaceDialog({
       setRelayUrl(workspace.relayUrl);
       setToken(workspace.token ?? "");
       setReposDir(workspace.reposDir ?? "");
+      setReposDirError(null);
     }
   }, [workspace, open]);
 
@@ -84,10 +87,18 @@ export function EditWorkspaceDialog({
 
       // Expand `~` to an absolute path before save — the backend rejects
       // tilde paths. An empty field clears the override (REPOS reverts to a
-      // real dir). Only emit when the resolved value actually changed so a
-      // no-op edit doesn't trigger a backend re-apply.
+      // real dir). Validate the expanded value (the bytes the backend
+      // canonicalizes) before save so a bad path is caught here instead of
+      // bricking a later boot. Only emit when the resolved value actually
+      // changed so a no-op edit doesn't trigger a backend re-apply.
       const expandedReposDir = await expandTilde(reposDir);
       if (expandedReposDir !== workspace.reposDir) {
+        try {
+          await validateReposDir(expandedReposDir ?? "");
+        } catch (error) {
+          setReposDirError(String(error));
+          return;
+        }
         updates.reposDir = expandedReposDir;
       }
 
@@ -185,11 +196,17 @@ export function EditWorkspaceDialog({
             </label>
             <Input
               id="edit-ws-repos-dir"
-              onChange={(e) => setReposDir(e.target.value)}
+              onChange={(e) => {
+                setReposDir(e.target.value);
+                setReposDirError(null);
+              }}
               placeholder="~/Development"
               type="text"
               value={reposDir}
             />
+            {reposDirError ? (
+              <p className="text-xs text-destructive">{reposDirError}</p>
+            ) : null}
             <p className="text-xs text-muted-foreground">
               Point the agent's <code>REPOS</code> directory at an existing
               folder so agents work in your local checkouts. Leave blank to use
diff --git a/desktop/src/features/workspaces/useWorkspaceInit.ts b/desktop/src/features/workspaces/useWorkspaceInit.ts
index c0d20f108b..fe01c30ce4 100644
--- a/desktop/src/features/workspaces/useWorkspaceInit.ts
+++ b/desktop/src/features/workspaces/useWorkspaceInit.ts
@@ -139,12 +139,15 @@ export function useWorkspaceInit(
           activeWorkspace.reposDir,
         );
       } catch (error) {
-        // apply_workspace validates repos_dir before touching relay/keys, so a
-        // hard reject (bad path) leaves the backend on the previous/default
-        // relay with nothing applied. Marking the workspace ready here would
-        // render workspace-scoped UI against the wrong relay — a silent
-        // split-brain. Park on the loading gate (isReady:false, no appliedKey)
-        // instead; the backend already toasts a `repos-dir-error`.
+        // A bad `repos_dir` no longer reaches here — `apply_workspace` treats
+        // it as non-fatal (relay/keys apply, bad value not persisted, REPOS
+        // falls back to a real dir, a `repos-dir-error` toast surfaces it) and
+        // returns Ok, so the app boots into a working state where the user can
+        // fix the value in workspace settings. This catch now only fires on a
+        // genuine relay/key apply failure (e.g. an invalid nsec or a poisoned
+        // lock). For those, marking the workspace ready would render
+        // workspace-scoped UI against a backend that never applied — park on
+        // the loading gate (isReady:false, no appliedKey) instead.
         console.error("Failed to apply workspace to backend:", error);
         if (!cancelled) {
           setResult({ isReady: false, needsSetup: false, appliedKey: null });
diff --git a/desktop/src/shared/api/tauri.ts b/desktop/src/shared/api/tauri.ts
index 519f3fd859..1975e016eb 100644
--- a/desktop/src/shared/api/tauri.ts
+++ b/desktop/src/shared/api/tauri.ts
@@ -1188,5 +1188,11 @@ export async function applyWorkspace(
   });
 }
 
+// Validate a candidate repos dir without mutating the filesystem. Rejects
+// with a human-readable reason; resolves for a valid or empty path.
+export async function validateReposDir(dir: string): Promise<void> {
+  await invokeTauri("validate_repos_dir", { dir });
+}
+
 export const setPreventSleepActive = (active: boolean) =>
   invokeTauri("set_prevent_sleep_active", { active });