diff --git a/CHANGELOG.md b/CHANGELOG.md
index 092cfea..7b8df78 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 ### Fixed
 
 - **`task-done --remove-worktree` now force-deletes reviewer branches so `task-reviewer` re-dispatch isn't blocked.** The cleanup's `git branch -d` is the safe-delete variant that requires the branch to be fully merged into HEAD — correct for worker branches (don't drop unmerged work), but wrong for reviewer worktrees, whose `task/review-pr<N>` branch is forked from the PR's head ref and is never going to land in main (the PR is). Result: every reviewer cleanup left `task/review-pr<N>` behind as an orphan, and the next `task-reviewer <N>` refused to dispatch via its per-PR guard with `Error: a review worktree or branch already exists`. The user had to manually `git branch -D task/review-pr<N>` between every re-review round. `task-done` now branches on the `PR_NUMBER=` marker that `task-reviewer` writes into the worktree's `.info` file: when present it does `git branch -D` (scaffold-only, safe to force); when absent worker behavior is unchanged. Lands across the `task-done-std` and `task-done-local` drift groups (7 binaries). (#148)
+- **Radio session corruption on long-running workers — `LOADOUT` / `AGENT` / `TAB_ID` no longer lost mid-life.** Three-bug cluster surfaced by `--auto` workers running for hours: Claude Code's `SessionEnd` hook fires repeatedly with non-`clear|resume` reasons (the diagnostic added in #150 caught bursts of 144 invocations in ~25s, payload literally a single `y` character, `reason=<unset>` — phantom calls upstream of the documented hook contract), each one wiping `~/.task-force/radio/sessions/<role>.info`. The next `busy`/`ready` hook re-seeded the file with `LOADOUT=unknown`, empty `TAB_ID=`, and `AGENT=claude` (silently flipping kiro-* workers), which then broke `radio send`'s tab-id-based wake-up — PM pings landed in the mailbox silently and never woke the worker. Three concrete fixes: **(#140 Fix B)** `_zellij_tab_id_by_name` now matches the emoji-prefixed visible name (`⏸️ <slug>` / `▶️ <slug>` / `❓︎ <slug>`) so the re-seed's tab-id lookup survives `_rename_tab`'s repaints; **(#140 Fix C / #150 / #151)** `cmd_register` writes a `<role>.loadout` (and now `<role>.agent`) sidecar atomically BEFORE the `.info` write (so a kill mid-call leaves a recoverable state), `_ensure_session_file` reads from those sidecars on re-seed (TOCTOU-safe via `cat || true`), and `cmd_unregister`'s skip-list now also short-circuits on empty `reason` — treating the cascade pattern the same as `clear` / `resume`. Real-exit reasons (`logout` / `prompt_input_exit` / `other`) still flow through and clean up normally. Net result: a worker that previously degraded after 4–8 hours (or sooner under heavy subagent use) now keeps its full identity through the cascade, and PM `radio send` keeps waking it via the original `TAB_ID`. (#140, #150, #151)
 - **`task-reviewer`'s spec-issue cross-check now works on `claude-jira` / `claude-notion` / `claude-local`.** The dispatcher and the `/reviewer` prompt were both GitHub-only: `parse_issue_number` rejected anything that wasn't a bare integer or `github.com/.../issues/N`; PR-body auto-detect only matched `Closes #N`; the URL-synthesis step always emitted a GitHub issues URL; and the prompt hardcoded `gh issue view <M>` for spec lookup. Net result: in any non-gh loadout, `task-reviewer <pr> <spec-id>` silently degraded to a diff-only review. The dispatcher is now loadout-aware (detects from its own file path) — `claude-gh` keeps numeric / URL parsing and PR-body auto-detect; `claude-jira` / `claude-notion` / `claude-local` accept any non-empty 2nd positional arg as an opaque spec identifier (Jira key, Notion URL, local task slug) and pass it through to `/reviewer` unchanged. The 4 dispatcher bodies stay byte-identical (drift-checked). Each loadout's `commands/reviewer.md` now points the spec-lookup step at the right tool: GH stays on `gh issue view`; `claude-jira` uses `mcp__atlassian__getJiraIssue`; `claude-notion` uses `mcp__notion__notion-fetch`; `claude-local` reads `tasks/<id>-<slug>.md` via the `Read` tool. With no 2nd arg in a non-gh loadout, the wrapper emits a clear "PR-body auto-detect is GitHub-only — pass the spec id explicitly" advisory and proceeds diff-only. **Upgrading**: re-run `task-init <loadout>` after pulling this change so the updated `/reviewer` prompt lands in `.claude/commands/`. (#144)
 
 ### Changed
diff --git a/claude-gh/bin/radio b/claude-gh/bin/radio
index a091d7b..5ae3e6b 100755
--- a/claude-gh/bin/radio
+++ b/claude-gh/bin/radio
@@ -167,6 +167,17 @@ _loadout_sidecar() {
   printf '%s/%s.loadout' "$SESSIONS_DIR" "$1"
 }
 
+# Agent sidecar (#151). Same problem as LOADOUT: $TASK_FORCE_AGENT isn't
+# exported into Claude Code's hook subshells, so _ensure_session_file's
+# previous fallback to "${TASK_FORCE_AGENT:-claude}" silently wrote
+# AGENT=claude for kiro-* workers on every re-seed. Parallel sidecar, parallel
+# write/read/sweep semantics — no current runtime consumer, but a kiro worker
+# whose re-seeded session reports AGENT=claude is a footgun if anyone wires
+# AGENT-conditional behaviour later.
+_agent_sidecar() {
+  printf '%s/%s.agent' "$SESSIONS_DIR" "$1"
+}
+
 _inbox_dir()    { printf '%s/%s/inbox'     "$MAILBOX_DIR" "$1"; }
 _processed_dir(){ printf '%s/%s/processed' "$MAILBOX_DIR" "$1"; }
 
@@ -216,13 +227,26 @@ _ensure_session_file() {
   loadout=$(cat "$sidecar" 2>/dev/null || true)
   [[ -n "$loadout" ]] || loadout="${TASK_FORCE_LOADOUT:-unknown}"
 
+  # AGENT recovery (#151): same hook-subshell unset story as LOADOUT — the
+  # cascade wipes .info, and the next re-seed used to default to "claude"
+  # regardless of whether this was a kiro-* worker. Read the agent sidecar
+  # cmd_register persisted; fall back to the env var only for test paths that
+  # exercise _ensure_session_file directly. Same TOCTOU-safe `cat … || true`
+  # pattern as the loadout read above for the same reason (concurrent
+  # unregister race window).
+  local agent=""
+  local agent_sidecar
+  agent_sidecar=$(_agent_sidecar "$TASK_FORCE_ROLE")
+  agent=$(cat "$agent_sidecar" 2>/dev/null || true)
+  [[ -n "$agent" ]] || agent="${TASK_FORCE_AGENT:-claude}"
+
   local repo
   repo=$(git rev-parse --show-toplevel 2>/dev/null || echo "")
 
   {
     printf 'ROLE=%s\nTAB=%s\nTAB_ID=%s\nREPO=%s\nSTATE=idle\nLAST_HEARTBEAT=%s\nAGENT=%s\nLOADOUT=%s\n' \
       "$TASK_FORCE_ROLE" "$ZELLIJ_TAB" "$tab_id" "$repo" "$(_now)" \
-      "${TASK_FORCE_AGENT:-claude}" "$loadout"
+      "$agent" "$loadout"
     # Preserve the --auto opt-in across self-heal so cmd_send keeps using CR
     # for wake-up after an intra-session re-seed (#128). Use `if` rather than
     # `&&` so the brace group exits 0 when the flag is absent — otherwise
@@ -234,7 +258,7 @@ _ensure_session_file() {
   } | _atomic_write "$f"
 
   mkdir -p "$(_inbox_dir "$TASK_FORCE_ROLE")" "$(_processed_dir "$TASK_FORCE_ROLE")"
-  _log "ensure_session: re-seeded $TASK_FORCE_ROLE (file was missing) tab_id=$tab_id loadout=$loadout"
+  _log "ensure_session: re-seeded $TASK_FORCE_ROLE (file was missing) tab_id=$tab_id loadout=$loadout agent=$agent"
 }
 
 # Update STATE=… and LAST_HEARTBEAT=… on the current session file.
@@ -385,29 +409,33 @@ cmd_register() {
     fi
   fi
 
-  # Persist the loadout sidecar BEFORE the session file (#150 round-2 review:
-  # Finding 1). If the process is killed (OOM, task-done --force, host
-  # shutdown) between these two _atomic_write calls, the order matters:
+  # Persist the loadout and agent sidecars BEFORE the session file (#150
+  # round-2 review: Finding 1; extended for AGENT in #151). If the process is
+  # killed (OOM, task-done --force, host shutdown) between these writes, the
+  # order matters:
   #
   #   sidecar-first (this order):
-  #     pre-kill state:  .loadout=claude-gh, .info absent
-  #     re-seed reads:   .loadout → LOADOUT=claude-gh recovered ✓
+  #     pre-kill state:  .loadout=claude-gh, .agent=claude, .info absent
+  #     re-seed reads:   sidecars → LOADOUT/AGENT recovered ✓
   #
   #   info-first (the OLD order — pre-#150-r3):
-  #     pre-kill state:  .info has LOADOUT=claude-gh, .loadout absent
-  #     unregister cascade deletes .info; .loadout never existed
+  #     pre-kill state:  .info has LOADOUT/AGENT, sidecars absent
+  #     unregister cascade deletes .info; sidecars never existed
   #     re-seed reads:   no sidecar, hook subshell has no $TASK_FORCE_LOADOUT
-  #                      → LOADOUT=unknown ✗
+  #                      / $TASK_FORCE_AGENT → LOADOUT=unknown / AGENT=claude ✗
   #
   # The window is microseconds wide, but the cascade in #140 makes it
   # statistically reachable. Reversing the order eliminates the failure mode
-  # entirely. Skipping the sidecar on empty $loadout keeps the sidecar's mere
+  # entirely. Skipping the loadout sidecar on empty $loadout keeps its mere
   # existence equivalent to "we have a real loadout to restore" — otherwise
   # a re-seed could read an empty sidecar and clobber the env-var fallback
-  # that test paths still rely on.
+  # that test paths still rely on. The agent sidecar is always written
+  # because --agent is required (cmd_register exits 2 above if absent), so
+  # $agent is always a real value here.
   if [[ -n "$loadout" ]]; then
     printf '%s' "$loadout" | _atomic_write "$(_loadout_sidecar "$role")"
   fi
+  printf '%s' "$agent" | _atomic_write "$(_agent_sidecar "$role")"
 
   {
     printf 'ROLE=%s\nTAB=%s\nTAB_ID=%s\nREPO=%s\nSTATE=idle\nLAST_HEARTBEAT=%s\nAGENT=%s\nLOADOUT=%s\n' \
@@ -461,6 +489,22 @@ cmd_unregister() {
           _log "unregister: skipping (reason=$reason — intra-session event) role=$TASK_FORCE_ROLE"
           return 0
           ;;
+        "")
+          # Cascade pattern (#151): payload is present but contains no
+          # parseable `.reason` field. The PR-#150 diagnostic showed bursts of
+          # 144 unregister calls in ~25s with payload literally "y" and
+          # reason=<unset> — phantom invocations from somewhere upstream of
+          # Claude Code's documented SessionEnd hook (which always includes
+          # reason ∈ {clear, resume, logout, prompt_input_exit, other}).
+          # Treat these the same as clear/resume: known non-real-exit events
+          # that must not wipe the session file or the sidecars. Real exits
+          # still flow through the logout/prompt_input_exit/other branches
+          # below and clean up normally; manual invocations (no stdin) also
+          # proceed because `[[ ! -t 0 ]]` is false then.
+          payload_oneline=$(printf '%s' "$payload" | tr '\n' ' ' | tr -s ' ')
+          _log "unregister: skipping (reason=<unset> — cascade, no real-exit signal) role=$TASK_FORCE_ROLE payload=$payload_oneline"
+          return 0
+          ;;
       esac
     fi
     # Instrumentation for #140: when the hook fires with a payload that
@@ -468,7 +512,10 @@ cmd_unregister() {
     # what reason (or non-reason) is driving the unregister cascade. Empirically
     # observed as bursts of 20+ unregister calls in ~30s on long-running
     # worker sessions; the root cause needs the payload to investigate. Log
-    # is compacted to one line via tr so it doesn't fragment radio.log.
+    # is compacted to one line via tr so it doesn't fragment radio.log. Post-
+    # #151, an empty reason is already short-circuited above, so this line
+    # only fires for non-empty named reasons (logout, prompt_input_exit,
+    # other, or anything new Claude Code adds in the future).
     if [[ -n "$payload" ]]; then
       payload_oneline=$(printf '%s' "$payload" | tr '\n' ' ' | tr -s ' ')
       _log "unregister: proceeding (reason=${reason:-<unset>}) role=$TASK_FORCE_ROLE payload=$payload_oneline"
@@ -478,10 +525,11 @@ cmd_unregister() {
   local f
   f=$(_session_file "$TASK_FORCE_ROLE")
   rm -f "$f"
-  # Sweep the loadout sidecar too — leaving it behind would let a future
-  # _ensure_session_file resurrect a stale loadout for a role whose tab has
-  # really exited and been re-used (#140).
+  # Sweep the loadout + agent sidecars too — leaving them behind would let a
+  # future _ensure_session_file resurrect a stale loadout / agent for a role
+  # whose tab has really exited and been re-used (#140, #151).
   rm -f "$(_loadout_sidecar "$TASK_FORCE_ROLE")"
+  rm -f "$(_agent_sidecar "$TASK_FORCE_ROLE")"
   _log "unregister role=$TASK_FORCE_ROLE"
 }
 
diff --git a/claude-gh/bin/task-done b/claude-gh/bin/task-done
index b44dfc6..c627525 100755
--- a/claude-gh/bin/task-done
+++ b/claude-gh/bin/task-done
@@ -131,8 +131,14 @@ fi
 # `|| true` is a safety net: $TASK_FORCE_ROLE should be set inside a worker
 # tab, but if it isn't (e.g., task-done invoked from an unexpected shell)
 # the no-op must not abort cleanup. `radio unregister` itself already
-# silently exits when $TASK_FORCE_ROLE is unset (#93).
-radio unregister 2>/dev/null || true
+# silently exits when $TASK_FORCE_ROLE is unset (#93). Redirect stdin from
+# /dev/null so `radio unregister` doesn't inherit task-done's stdin — under
+# `--force` the calling shell may have piped `y` (or any other content)
+# to confirm something else, and post-#151 a non-empty stdin without a
+# parseable JSON reason triggers the cascade-skip path. That's correct
+# behaviour for SessionEnd hook invocations but wrong for explicit
+# task-done cleanup, which must always proceed with the unregister.
+radio unregister </dev/null 2>/dev/null || true
 
 # Move out of worktree before removing it
 cd "$MAIN_WORKTREE"
diff --git a/claude-jira/bin/radio b/claude-jira/bin/radio
index a091d7b..5ae3e6b 100755
--- a/claude-jira/bin/radio
+++ b/claude-jira/bin/radio
@@ -167,6 +167,17 @@ _loadout_sidecar() {
   printf '%s/%s.loadout' "$SESSIONS_DIR" "$1"
 }
 
+# Agent sidecar (#151). Same problem as LOADOUT: $TASK_FORCE_AGENT isn't
+# exported into Claude Code's hook subshells, so _ensure_session_file's
+# previous fallback to "${TASK_FORCE_AGENT:-claude}" silently wrote
+# AGENT=claude for kiro-* workers on every re-seed. Parallel sidecar, parallel
+# write/read/sweep semantics — no current runtime consumer, but a kiro worker
+# whose re-seeded session reports AGENT=claude is a footgun if anyone wires
+# AGENT-conditional behaviour later.
+_agent_sidecar() {
+  printf '%s/%s.agent' "$SESSIONS_DIR" "$1"
+}
+
 _inbox_dir()    { printf '%s/%s/inbox'     "$MAILBOX_DIR" "$1"; }
 _processed_dir(){ printf '%s/%s/processed' "$MAILBOX_DIR" "$1"; }
 
@@ -216,13 +227,26 @@ _ensure_session_file() {
   loadout=$(cat "$sidecar" 2>/dev/null || true)
   [[ -n "$loadout" ]] || loadout="${TASK_FORCE_LOADOUT:-unknown}"
 
+  # AGENT recovery (#151): same hook-subshell unset story as LOADOUT — the
+  # cascade wipes .info, and the next re-seed used to default to "claude"
+  # regardless of whether this was a kiro-* worker. Read the agent sidecar
+  # cmd_register persisted; fall back to the env var only for test paths that
+  # exercise _ensure_session_file directly. Same TOCTOU-safe `cat … || true`
+  # pattern as the loadout read above for the same reason (concurrent
+  # unregister race window).
+  local agent=""
+  local agent_sidecar
+  agent_sidecar=$(_agent_sidecar "$TASK_FORCE_ROLE")
+  agent=$(cat "$agent_sidecar" 2>/dev/null || true)
+  [[ -n "$agent" ]] || agent="${TASK_FORCE_AGENT:-claude}"
+
   local repo
   repo=$(git rev-parse --show-toplevel 2>/dev/null || echo "")
 
   {
     printf 'ROLE=%s\nTAB=%s\nTAB_ID=%s\nREPO=%s\nSTATE=idle\nLAST_HEARTBEAT=%s\nAGENT=%s\nLOADOUT=%s\n' \
       "$TASK_FORCE_ROLE" "$ZELLIJ_TAB" "$tab_id" "$repo" "$(_now)" \
-      "${TASK_FORCE_AGENT:-claude}" "$loadout"
+      "$agent" "$loadout"
     # Preserve the --auto opt-in across self-heal so cmd_send keeps using CR
     # for wake-up after an intra-session re-seed (#128). Use `if` rather than
     # `&&` so the brace group exits 0 when the flag is absent — otherwise
@@ -234,7 +258,7 @@ _ensure_session_file() {
   } | _atomic_write "$f"
 
   mkdir -p "$(_inbox_dir "$TASK_FORCE_ROLE")" "$(_processed_dir "$TASK_FORCE_ROLE")"
-  _log "ensure_session: re-seeded $TASK_FORCE_ROLE (file was missing) tab_id=$tab_id loadout=$loadout"
+  _log "ensure_session: re-seeded $TASK_FORCE_ROLE (file was missing) tab_id=$tab_id loadout=$loadout agent=$agent"
 }
 
 # Update STATE=… and LAST_HEARTBEAT=… on the current session file.
@@ -385,29 +409,33 @@ cmd_register() {
     fi
   fi
 
-  # Persist the loadout sidecar BEFORE the session file (#150 round-2 review:
-  # Finding 1). If the process is killed (OOM, task-done --force, host
-  # shutdown) between these two _atomic_write calls, the order matters:
+  # Persist the loadout and agent sidecars BEFORE the session file (#150
+  # round-2 review: Finding 1; extended for AGENT in #151). If the process is
+  # killed (OOM, task-done --force, host shutdown) between these writes, the
+  # order matters:
   #
   #   sidecar-first (this order):
-  #     pre-kill state:  .loadout=claude-gh, .info absent
-  #     re-seed reads:   .loadout → LOADOUT=claude-gh recovered ✓
+  #     pre-kill state:  .loadout=claude-gh, .agent=claude, .info absent
+  #     re-seed reads:   sidecars → LOADOUT/AGENT recovered ✓
   #
   #   info-first (the OLD order — pre-#150-r3):
-  #     pre-kill state:  .info has LOADOUT=claude-gh, .loadout absent
-  #     unregister cascade deletes .info; .loadout never existed
+  #     pre-kill state:  .info has LOADOUT/AGENT, sidecars absent
+  #     unregister cascade deletes .info; sidecars never existed
   #     re-seed reads:   no sidecar, hook subshell has no $TASK_FORCE_LOADOUT
-  #                      → LOADOUT=unknown ✗
+  #                      / $TASK_FORCE_AGENT → LOADOUT=unknown / AGENT=claude ✗
   #
   # The window is microseconds wide, but the cascade in #140 makes it
   # statistically reachable. Reversing the order eliminates the failure mode
-  # entirely. Skipping the sidecar on empty $loadout keeps the sidecar's mere
+  # entirely. Skipping the loadout sidecar on empty $loadout keeps its mere
   # existence equivalent to "we have a real loadout to restore" — otherwise
   # a re-seed could read an empty sidecar and clobber the env-var fallback
-  # that test paths still rely on.
+  # that test paths still rely on. The agent sidecar is always written
+  # because --agent is required (cmd_register exits 2 above if absent), so
+  # $agent is always a real value here.
   if [[ -n "$loadout" ]]; then
     printf '%s' "$loadout" | _atomic_write "$(_loadout_sidecar "$role")"
   fi
+  printf '%s' "$agent" | _atomic_write "$(_agent_sidecar "$role")"
 
   {
     printf 'ROLE=%s\nTAB=%s\nTAB_ID=%s\nREPO=%s\nSTATE=idle\nLAST_HEARTBEAT=%s\nAGENT=%s\nLOADOUT=%s\n' \
@@ -461,6 +489,22 @@ cmd_unregister() {
           _log "unregister: skipping (reason=$reason — intra-session event) role=$TASK_FORCE_ROLE"
           return 0
           ;;
+        "")
+          # Cascade pattern (#151): payload is present but contains no
+          # parseable `.reason` field. The PR-#150 diagnostic showed bursts of
+          # 144 unregister calls in ~25s with payload literally "y" and
+          # reason=<unset> — phantom invocations from somewhere upstream of
+          # Claude Code's documented SessionEnd hook (which always includes
+          # reason ∈ {clear, resume, logout, prompt_input_exit, other}).
+          # Treat these the same as clear/resume: known non-real-exit events
+          # that must not wipe the session file or the sidecars. Real exits
+          # still flow through the logout/prompt_input_exit/other branches
+          # below and clean up normally; manual invocations (no stdin) also
+          # proceed because `[[ ! -t 0 ]]` is false then.
+          payload_oneline=$(printf '%s' "$payload" | tr '\n' ' ' | tr -s ' ')
+          _log "unregister: skipping (reason=<unset> — cascade, no real-exit signal) role=$TASK_FORCE_ROLE payload=$payload_oneline"
+          return 0
+          ;;
       esac
     fi
     # Instrumentation for #140: when the hook fires with a payload that
@@ -468,7 +512,10 @@ cmd_unregister() {
     # what reason (or non-reason) is driving the unregister cascade. Empirically
     # observed as bursts of 20+ unregister calls in ~30s on long-running
     # worker sessions; the root cause needs the payload to investigate. Log
-    # is compacted to one line via tr so it doesn't fragment radio.log.
+    # is compacted to one line via tr so it doesn't fragment radio.log. Post-
+    # #151, an empty reason is already short-circuited above, so this line
+    # only fires for non-empty named reasons (logout, prompt_input_exit,
+    # other, or anything new Claude Code adds in the future).
     if [[ -n "$payload" ]]; then
       payload_oneline=$(printf '%s' "$payload" | tr '\n' ' ' | tr -s ' ')
       _log "unregister: proceeding (reason=${reason:-<unset>}) role=$TASK_FORCE_ROLE payload=$payload_oneline"
@@ -478,10 +525,11 @@ cmd_unregister() {
   local f
   f=$(_session_file "$TASK_FORCE_ROLE")
   rm -f "$f"
-  # Sweep the loadout sidecar too — leaving it behind would let a future
-  # _ensure_session_file resurrect a stale loadout for a role whose tab has
-  # really exited and been re-used (#140).
+  # Sweep the loadout + agent sidecars too — leaving them behind would let a
+  # future _ensure_session_file resurrect a stale loadout / agent for a role
+  # whose tab has really exited and been re-used (#140, #151).
   rm -f "$(_loadout_sidecar "$TASK_FORCE_ROLE")"
+  rm -f "$(_agent_sidecar "$TASK_FORCE_ROLE")"
   _log "unregister role=$TASK_FORCE_ROLE"
 }
 
diff --git a/claude-jira/bin/task-done b/claude-jira/bin/task-done
index 17af7c1..c5574a9 100755
--- a/claude-jira/bin/task-done
+++ b/claude-jira/bin/task-done
@@ -137,8 +137,14 @@ fi
 # `|| true` is a safety net: $TASK_FORCE_ROLE should be set inside a worker
 # tab, but if it isn't (e.g., task-done invoked from an unexpected shell)
 # the no-op must not abort cleanup. `radio unregister` itself already
-# silently exits when $TASK_FORCE_ROLE is unset (#93).
-radio unregister 2>/dev/null || true
+# silently exits when $TASK_FORCE_ROLE is unset (#93). Redirect stdin from
+# /dev/null so `radio unregister` doesn't inherit task-done's stdin — under
+# `--force` the calling shell may have piped `y` (or any other content)
+# to confirm something else, and post-#151 a non-empty stdin without a
+# parseable JSON reason triggers the cascade-skip path. That's correct
+# behaviour for SessionEnd hook invocations but wrong for explicit
+# task-done cleanup, which must always proceed with the unregister.
+radio unregister </dev/null 2>/dev/null || true
 
 # Move out of worktree before removing it
 cd "$MAIN_WORKTREE"
diff --git a/claude-local/bin/radio b/claude-local/bin/radio
index a091d7b..5ae3e6b 100755
--- a/claude-local/bin/radio
+++ b/claude-local/bin/radio
@@ -167,6 +167,17 @@ _loadout_sidecar() {
   printf '%s/%s.loadout' "$SESSIONS_DIR" "$1"
 }
 
+# Agent sidecar (#151). Same problem as LOADOUT: $TASK_FORCE_AGENT isn't
+# exported into Claude Code's hook subshells, so _ensure_session_file's
+# previous fallback to "${TASK_FORCE_AGENT:-claude}" silently wrote
+# AGENT=claude for kiro-* workers on every re-seed. Parallel sidecar, parallel
+# write/read/sweep semantics — no current runtime consumer, but a kiro worker
+# whose re-seeded session reports AGENT=claude is a footgun if anyone wires
+# AGENT-conditional behaviour later.
+_agent_sidecar() {
+  printf '%s/%s.agent' "$SESSIONS_DIR" "$1"
+}
+
 _inbox_dir()    { printf '%s/%s/inbox'     "$MAILBOX_DIR" "$1"; }
 _processed_dir(){ printf '%s/%s/processed' "$MAILBOX_DIR" "$1"; }
 
@@ -216,13 +227,26 @@ _ensure_session_file() {
   loadout=$(cat "$sidecar" 2>/dev/null || true)
   [[ -n "$loadout" ]] || loadout="${TASK_FORCE_LOADOUT:-unknown}"
 
+  # AGENT recovery (#151): same hook-subshell unset story as LOADOUT — the
+  # cascade wipes .info, and the next re-seed used to default to "claude"
+  # regardless of whether this was a kiro-* worker. Read the agent sidecar
+  # cmd_register persisted; fall back to the env var only for test paths that
+  # exercise _ensure_session_file directly. Same TOCTOU-safe `cat … || true`
+  # pattern as the loadout read above for the same reason (concurrent
+  # unregister race window).
+  local agent=""
+  local agent_sidecar
+  agent_sidecar=$(_agent_sidecar "$TASK_FORCE_ROLE")
+  agent=$(cat "$agent_sidecar" 2>/dev/null || true)
+  [[ -n "$agent" ]] || agent="${TASK_FORCE_AGENT:-claude}"
+
   local repo
   repo=$(git rev-parse --show-toplevel 2>/dev/null || echo "")
 
   {
     printf 'ROLE=%s\nTAB=%s\nTAB_ID=%s\nREPO=%s\nSTATE=idle\nLAST_HEARTBEAT=%s\nAGENT=%s\nLOADOUT=%s\n' \
       "$TASK_FORCE_ROLE" "$ZELLIJ_TAB" "$tab_id" "$repo" "$(_now)" \
-      "${TASK_FORCE_AGENT:-claude}" "$loadout"
+      "$agent" "$loadout"
     # Preserve the --auto opt-in across self-heal so cmd_send keeps using CR
     # for wake-up after an intra-session re-seed (#128). Use `if` rather than
     # `&&` so the brace group exits 0 when the flag is absent — otherwise
@@ -234,7 +258,7 @@ _ensure_session_file() {
   } | _atomic_write "$f"
 
   mkdir -p "$(_inbox_dir "$TASK_FORCE_ROLE")" "$(_processed_dir "$TASK_FORCE_ROLE")"
-  _log "ensure_session: re-seeded $TASK_FORCE_ROLE (file was missing) tab_id=$tab_id loadout=$loadout"
+  _log "ensure_session: re-seeded $TASK_FORCE_ROLE (file was missing) tab_id=$tab_id loadout=$loadout agent=$agent"
 }
 
 # Update STATE=… and LAST_HEARTBEAT=… on the current session file.
@@ -385,29 +409,33 @@ cmd_register() {
     fi
   fi
 
-  # Persist the loadout sidecar BEFORE the session file (#150 round-2 review:
-  # Finding 1). If the process is killed (OOM, task-done --force, host
-  # shutdown) between these two _atomic_write calls, the order matters:
+  # Persist the loadout and agent sidecars BEFORE the session file (#150
+  # round-2 review: Finding 1; extended for AGENT in #151). If the process is
+  # killed (OOM, task-done --force, host shutdown) between these writes, the
+  # order matters:
   #
   #   sidecar-first (this order):
-  #     pre-kill state:  .loadout=claude-gh, .info absent
-  #     re-seed reads:   .loadout → LOADOUT=claude-gh recovered ✓
+  #     pre-kill state:  .loadout=claude-gh, .agent=claude, .info absent
+  #     re-seed reads:   sidecars → LOADOUT/AGENT recovered ✓
   #
   #   info-first (the OLD order — pre-#150-r3):
-  #     pre-kill state:  .info has LOADOUT=claude-gh, .loadout absent
-  #     unregister cascade deletes .info; .loadout never existed
+  #     pre-kill state:  .info has LOADOUT/AGENT, sidecars absent
+  #     unregister cascade deletes .info; sidecars never existed
   #     re-seed reads:   no sidecar, hook subshell has no $TASK_FORCE_LOADOUT
-  #                      → LOADOUT=unknown ✗
+  #                      / $TASK_FORCE_AGENT → LOADOUT=unknown / AGENT=claude ✗
   #
   # The window is microseconds wide, but the cascade in #140 makes it
   # statistically reachable. Reversing the order eliminates the failure mode
-  # entirely. Skipping the sidecar on empty $loadout keeps the sidecar's mere
+  # entirely. Skipping the loadout sidecar on empty $loadout keeps its mere
   # existence equivalent to "we have a real loadout to restore" — otherwise
   # a re-seed could read an empty sidecar and clobber the env-var fallback
-  # that test paths still rely on.
+  # that test paths still rely on. The agent sidecar is always written
+  # because --agent is required (cmd_register exits 2 above if absent), so
+  # $agent is always a real value here.
   if [[ -n "$loadout" ]]; then
     printf '%s' "$loadout" | _atomic_write "$(_loadout_sidecar "$role")"
   fi
+  printf '%s' "$agent" | _atomic_write "$(_agent_sidecar "$role")"
 
   {
     printf 'ROLE=%s\nTAB=%s\nTAB_ID=%s\nREPO=%s\nSTATE=idle\nLAST_HEARTBEAT=%s\nAGENT=%s\nLOADOUT=%s\n' \
@@ -461,6 +489,22 @@ cmd_unregister() {
           _log "unregister: skipping (reason=$reason — intra-session event) role=$TASK_FORCE_ROLE"
           return 0
           ;;
+        "")
+          # Cascade pattern (#151): payload is present but contains no
+          # parseable `.reason` field. The PR-#150 diagnostic showed bursts of
+          # 144 unregister calls in ~25s with payload literally "y" and
+          # reason=<unset> — phantom invocations from somewhere upstream of
+          # Claude Code's documented SessionEnd hook (which always includes
+          # reason ∈ {clear, resume, logout, prompt_input_exit, other}).
+          # Treat these the same as clear/resume: known non-real-exit events
+          # that must not wipe the session file or the sidecars. Real exits
+          # still flow through the logout/prompt_input_exit/other branches
+          # below and clean up normally; manual invocations (no stdin) also
+          # proceed because `[[ ! -t 0 ]]` is false then.
+          payload_oneline=$(printf '%s' "$payload" | tr '\n' ' ' | tr -s ' ')
+          _log "unregister: skipping (reason=<unset> — cascade, no real-exit signal) role=$TASK_FORCE_ROLE payload=$payload_oneline"
+          return 0
+          ;;
       esac
     fi
     # Instrumentation for #140: when the hook fires with a payload that
@@ -468,7 +512,10 @@ cmd_unregister() {
     # what reason (or non-reason) is driving the unregister cascade. Empirically
     # observed as bursts of 20+ unregister calls in ~30s on long-running
     # worker sessions; the root cause needs the payload to investigate. Log
-    # is compacted to one line via tr so it doesn't fragment radio.log.
+    # is compacted to one line via tr so it doesn't fragment radio.log. Post-
+    # #151, an empty reason is already short-circuited above, so this line
+    # only fires for non-empty named reasons (logout, prompt_input_exit,
+    # other, or anything new Claude Code adds in the future).
     if [[ -n "$payload" ]]; then
       payload_oneline=$(printf '%s' "$payload" | tr '\n' ' ' | tr -s ' ')
       _log "unregister: proceeding (reason=${reason:-<unset>}) role=$TASK_FORCE_ROLE payload=$payload_oneline"
@@ -478,10 +525,11 @@ cmd_unregister() {
   local f
   f=$(_session_file "$TASK_FORCE_ROLE")
   rm -f "$f"
-  # Sweep the loadout sidecar too — leaving it behind would let a future
-  # _ensure_session_file resurrect a stale loadout for a role whose tab has
-  # really exited and been re-used (#140).
+  # Sweep the loadout + agent sidecars too — leaving them behind would let a
+  # future _ensure_session_file resurrect a stale loadout / agent for a role
+  # whose tab has really exited and been re-used (#140, #151).
   rm -f "$(_loadout_sidecar "$TASK_FORCE_ROLE")"
+  rm -f "$(_agent_sidecar "$TASK_FORCE_ROLE")"
   _log "unregister role=$TASK_FORCE_ROLE"
 }
 
diff --git a/claude-local/bin/task-done b/claude-local/bin/task-done
index a5a1b63..21f923a 100755
--- a/claude-local/bin/task-done
+++ b/claude-local/bin/task-done
@@ -133,8 +133,14 @@ fi
 # `|| true` is a safety net: $TASK_FORCE_ROLE should be set inside a worker
 # tab, but if it isn't (e.g., task-done invoked from an unexpected shell)
 # the no-op must not abort cleanup. `radio unregister` itself already
-# silently exits when $TASK_FORCE_ROLE is unset (#93).
-radio unregister 2>/dev/null || true
+# silently exits when $TASK_FORCE_ROLE is unset (#93). Redirect stdin from
+# /dev/null so `radio unregister` doesn't inherit task-done's stdin — under
+# `--force` the calling shell may have piped `y` (or any other content)
+# to confirm something else, and post-#151 a non-empty stdin without a
+# parseable JSON reason triggers the cascade-skip path. That's correct
+# behaviour for SessionEnd hook invocations but wrong for explicit
+# task-done cleanup, which must always proceed with the unregister.
+radio unregister </dev/null 2>/dev/null || true
 
 # Move out of worktree before removing it
 cd "$MAIN_WORKTREE"
diff --git a/claude-notion/bin/radio b/claude-notion/bin/radio
index a091d7b..5ae3e6b 100755
--- a/claude-notion/bin/radio
+++ b/claude-notion/bin/radio
@@ -167,6 +167,17 @@ _loadout_sidecar() {
   printf '%s/%s.loadout' "$SESSIONS_DIR" "$1"
 }
 
+# Agent sidecar (#151). Same problem as LOADOUT: $TASK_FORCE_AGENT isn't
+# exported into Claude Code's hook subshells, so _ensure_session_file's
+# previous fallback to "${TASK_FORCE_AGENT:-claude}" silently wrote
+# AGENT=claude for kiro-* workers on every re-seed. Parallel sidecar, parallel
+# write/read/sweep semantics — no current runtime consumer, but a kiro worker
+# whose re-seeded session reports AGENT=claude is a footgun if anyone wires
+# AGENT-conditional behaviour later.
+_agent_sidecar() {
+  printf '%s/%s.agent' "$SESSIONS_DIR" "$1"
+}
+
 _inbox_dir()    { printf '%s/%s/inbox'     "$MAILBOX_DIR" "$1"; }
 _processed_dir(){ printf '%s/%s/processed' "$MAILBOX_DIR" "$1"; }
 
@@ -216,13 +227,26 @@ _ensure_session_file() {
   loadout=$(cat "$sidecar" 2>/dev/null || true)
   [[ -n "$loadout" ]] || loadout="${TASK_FORCE_LOADOUT:-unknown}"
 
+  # AGENT recovery (#151): same hook-subshell unset story as LOADOUT — the
+  # cascade wipes .info, and the next re-seed used to default to "claude"
+  # regardless of whether this was a kiro-* worker. Read the agent sidecar
+  # cmd_register persisted; fall back to the env var only for test paths that
+  # exercise _ensure_session_file directly. Same TOCTOU-safe `cat … || true`
+  # pattern as the loadout read above for the same reason (concurrent
+  # unregister race window).
+  local agent=""
+  local agent_sidecar
+  agent_sidecar=$(_agent_sidecar "$TASK_FORCE_ROLE")
+  agent=$(cat "$agent_sidecar" 2>/dev/null || true)
+  [[ -n "$agent" ]] || agent="${TASK_FORCE_AGENT:-claude}"
+
   local repo
   repo=$(git rev-parse --show-toplevel 2>/dev/null || echo "")
 
   {
     printf 'ROLE=%s\nTAB=%s\nTAB_ID=%s\nREPO=%s\nSTATE=idle\nLAST_HEARTBEAT=%s\nAGENT=%s\nLOADOUT=%s\n' \
       "$TASK_FORCE_ROLE" "$ZELLIJ_TAB" "$tab_id" "$repo" "$(_now)" \
-      "${TASK_FORCE_AGENT:-claude}" "$loadout"
+      "$agent" "$loadout"
     # Preserve the --auto opt-in across self-heal so cmd_send keeps using CR
     # for wake-up after an intra-session re-seed (#128). Use `if` rather than
     # `&&` so the brace group exits 0 when the flag is absent — otherwise
@@ -234,7 +258,7 @@ _ensure_session_file() {
   } | _atomic_write "$f"
 
   mkdir -p "$(_inbox_dir "$TASK_FORCE_ROLE")" "$(_processed_dir "$TASK_FORCE_ROLE")"
-  _log "ensure_session: re-seeded $TASK_FORCE_ROLE (file was missing) tab_id=$tab_id loadout=$loadout"
+  _log "ensure_session: re-seeded $TASK_FORCE_ROLE (file was missing) tab_id=$tab_id loadout=$loadout agent=$agent"
 }
 
 # Update STATE=… and LAST_HEARTBEAT=… on the current session file.
@@ -385,29 +409,33 @@ cmd_register() {
     fi
   fi
 
-  # Persist the loadout sidecar BEFORE the session file (#150 round-2 review:
-  # Finding 1). If the process is killed (OOM, task-done --force, host
-  # shutdown) between these two _atomic_write calls, the order matters:
+  # Persist the loadout and agent sidecars BEFORE the session file (#150
+  # round-2 review: Finding 1; extended for AGENT in #151). If the process is
+  # killed (OOM, task-done --force, host shutdown) between these writes, the
+  # order matters:
   #
   #   sidecar-first (this order):
-  #     pre-kill state:  .loadout=claude-gh, .info absent
-  #     re-seed reads:   .loadout → LOADOUT=claude-gh recovered ✓
+  #     pre-kill state:  .loadout=claude-gh, .agent=claude, .info absent
+  #     re-seed reads:   sidecars → LOADOUT/AGENT recovered ✓
   #
   #   info-first (the OLD order — pre-#150-r3):
-  #     pre-kill state:  .info has LOADOUT=claude-gh, .loadout absent
-  #     unregister cascade deletes .info; .loadout never existed
+  #     pre-kill state:  .info has LOADOUT/AGENT, sidecars absent
+  #     unregister cascade deletes .info; sidecars never existed
   #     re-seed reads:   no sidecar, hook subshell has no $TASK_FORCE_LOADOUT
-  #                      → LOADOUT=unknown ✗
+  #                      / $TASK_FORCE_AGENT → LOADOUT=unknown / AGENT=claude ✗
   #
   # The window is microseconds wide, but the cascade in #140 makes it
   # statistically reachable. Reversing the order eliminates the failure mode
-  # entirely. Skipping the sidecar on empty $loadout keeps the sidecar's mere
+  # entirely. Skipping the loadout sidecar on empty $loadout keeps its mere
   # existence equivalent to "we have a real loadout to restore" — otherwise
   # a re-seed could read an empty sidecar and clobber the env-var fallback
-  # that test paths still rely on.
+  # that test paths still rely on. The agent sidecar is always written
+  # because --agent is required (cmd_register exits 2 above if absent), so
+  # $agent is always a real value here.
   if [[ -n "$loadout" ]]; then
     printf '%s' "$loadout" | _atomic_write "$(_loadout_sidecar "$role")"
   fi
+  printf '%s' "$agent" | _atomic_write "$(_agent_sidecar "$role")"
 
   {
     printf 'ROLE=%s\nTAB=%s\nTAB_ID=%s\nREPO=%s\nSTATE=idle\nLAST_HEARTBEAT=%s\nAGENT=%s\nLOADOUT=%s\n' \
@@ -461,6 +489,22 @@ cmd_unregister() {
           _log "unregister: skipping (reason=$reason — intra-session event) role=$TASK_FORCE_ROLE"
           return 0
           ;;
+        "")
+          # Cascade pattern (#151): payload is present but contains no
+          # parseable `.reason` field. The PR-#150 diagnostic showed bursts of
+          # 144 unregister calls in ~25s with payload literally "y" and
+          # reason=<unset> — phantom invocations from somewhere upstream of
+          # Claude Code's documented SessionEnd hook (which always includes
+          # reason ∈ {clear, resume, logout, prompt_input_exit, other}).
+          # Treat these the same as clear/resume: known non-real-exit events
+          # that must not wipe the session file or the sidecars. Real exits
+          # still flow through the logout/prompt_input_exit/other branches
+          # below and clean up normally; manual invocations (no stdin) also
+          # proceed because `[[ ! -t 0 ]]` is false then.
+          payload_oneline=$(printf '%s' "$payload" | tr '\n' ' ' | tr -s ' ')
+          _log "unregister: skipping (reason=<unset> — cascade, no real-exit signal) role=$TASK_FORCE_ROLE payload=$payload_oneline"
+          return 0
+          ;;
       esac
     fi
     # Instrumentation for #140: when the hook fires with a payload that
@@ -468,7 +512,10 @@ cmd_unregister() {
     # what reason (or non-reason) is driving the unregister cascade. Empirically
     # observed as bursts of 20+ unregister calls in ~30s on long-running
     # worker sessions; the root cause needs the payload to investigate. Log
-    # is compacted to one line via tr so it doesn't fragment radio.log.
+    # is compacted to one line via tr so it doesn't fragment radio.log. Post-
+    # #151, an empty reason is already short-circuited above, so this line
+    # only fires for non-empty named reasons (logout, prompt_input_exit,
+    # other, or anything new Claude Code adds in the future).
     if [[ -n "$payload" ]]; then
       payload_oneline=$(printf '%s' "$payload" | tr '\n' ' ' | tr -s ' ')
       _log "unregister: proceeding (reason=${reason:-<unset>}) role=$TASK_FORCE_ROLE payload=$payload_oneline"
@@ -478,10 +525,11 @@ cmd_unregister() {
   local f
   f=$(_session_file "$TASK_FORCE_ROLE")
   rm -f "$f"
-  # Sweep the loadout sidecar too — leaving it behind would let a future
-  # _ensure_session_file resurrect a stale loadout for a role whose tab has
-  # really exited and been re-used (#140).
+  # Sweep the loadout + agent sidecars too — leaving them behind would let a
+  # future _ensure_session_file resurrect a stale loadout / agent for a role
+  # whose tab has really exited and been re-used (#140, #151).
   rm -f "$(_loadout_sidecar "$TASK_FORCE_ROLE")"
+  rm -f "$(_agent_sidecar "$TASK_FORCE_ROLE")"
   _log "unregister role=$TASK_FORCE_ROLE"
 }
 
diff --git a/claude-notion/bin/task-done b/claude-notion/bin/task-done
index b44dfc6..c627525 100755
--- a/claude-notion/bin/task-done
+++ b/claude-notion/bin/task-done
@@ -131,8 +131,14 @@ fi
 # `|| true` is a safety net: $TASK_FORCE_ROLE should be set inside a worker
 # tab, but if it isn't (e.g., task-done invoked from an unexpected shell)
 # the no-op must not abort cleanup. `radio unregister` itself already
-# silently exits when $TASK_FORCE_ROLE is unset (#93).
-radio unregister 2>/dev/null || true
+# silently exits when $TASK_FORCE_ROLE is unset (#93). Redirect stdin from
+# /dev/null so `radio unregister` doesn't inherit task-done's stdin — under
+# `--force` the calling shell may have piped `y` (or any other content)
+# to confirm something else, and post-#151 a non-empty stdin without a
+# parseable JSON reason triggers the cascade-skip path. That's correct
+# behaviour for SessionEnd hook invocations but wrong for explicit
+# task-done cleanup, which must always proceed with the unregister.
+radio unregister </dev/null 2>/dev/null || true
 
 # Move out of worktree before removing it
 cd "$MAIN_WORKTREE"
diff --git a/kiro-gh/bin/radio b/kiro-gh/bin/radio
index a091d7b..5ae3e6b 100755
--- a/kiro-gh/bin/radio
+++ b/kiro-gh/bin/radio
@@ -167,6 +167,17 @@ _loadout_sidecar() {
   printf '%s/%s.loadout' "$SESSIONS_DIR" "$1"
 }
 
+# Agent sidecar (#151). Same problem as LOADOUT: $TASK_FORCE_AGENT isn't
+# exported into Claude Code's hook subshells, so _ensure_session_file's
+# previous fallback to "${TASK_FORCE_AGENT:-claude}" silently wrote
+# AGENT=claude for kiro-* workers on every re-seed. Parallel sidecar, parallel
+# write/read/sweep semantics — no current runtime consumer, but a kiro worker
+# whose re-seeded session reports AGENT=claude is a footgun if anyone wires
+# AGENT-conditional behaviour later.
+_agent_sidecar() {
+  printf '%s/%s.agent' "$SESSIONS_DIR" "$1"
+}
+
 _inbox_dir()    { printf '%s/%s/inbox'     "$MAILBOX_DIR" "$1"; }
 _processed_dir(){ printf '%s/%s/processed' "$MAILBOX_DIR" "$1"; }
 
@@ -216,13 +227,26 @@ _ensure_session_file() {
   loadout=$(cat "$sidecar" 2>/dev/null || true)
   [[ -n "$loadout" ]] || loadout="${TASK_FORCE_LOADOUT:-unknown}"
 
+  # AGENT recovery (#151): same hook-subshell unset story as LOADOUT — the
+  # cascade wipes .info, and the next re-seed used to default to "claude"
+  # regardless of whether this was a kiro-* worker. Read the agent sidecar
+  # cmd_register persisted; fall back to the env var only for test paths that
+  # exercise _ensure_session_file directly. Same TOCTOU-safe `cat … || true`
+  # pattern as the loadout read above for the same reason (concurrent
+  # unregister race window).
+  local agent=""
+  local agent_sidecar
+  agent_sidecar=$(_agent_sidecar "$TASK_FORCE_ROLE")
+  agent=$(cat "$agent_sidecar" 2>/dev/null || true)
+  [[ -n "$agent" ]] || agent="${TASK_FORCE_AGENT:-claude}"
+
   local repo
   repo=$(git rev-parse --show-toplevel 2>/dev/null || echo "")
 
   {
     printf 'ROLE=%s\nTAB=%s\nTAB_ID=%s\nREPO=%s\nSTATE=idle\nLAST_HEARTBEAT=%s\nAGENT=%s\nLOADOUT=%s\n' \
       "$TASK_FORCE_ROLE" "$ZELLIJ_TAB" "$tab_id" "$repo" "$(_now)" \
-      "${TASK_FORCE_AGENT:-claude}" "$loadout"
+      "$agent" "$loadout"
     # Preserve the --auto opt-in across self-heal so cmd_send keeps using CR
     # for wake-up after an intra-session re-seed (#128). Use `if` rather than
     # `&&` so the brace group exits 0 when the flag is absent — otherwise
@@ -234,7 +258,7 @@ _ensure_session_file() {
   } | _atomic_write "$f"
 
   mkdir -p "$(_inbox_dir "$TASK_FORCE_ROLE")" "$(_processed_dir "$TASK_FORCE_ROLE")"
-  _log "ensure_session: re-seeded $TASK_FORCE_ROLE (file was missing) tab_id=$tab_id loadout=$loadout"
+  _log "ensure_session: re-seeded $TASK_FORCE_ROLE (file was missing) tab_id=$tab_id loadout=$loadout agent=$agent"
 }
 
 # Update STATE=… and LAST_HEARTBEAT=… on the current session file.
@@ -385,29 +409,33 @@ cmd_register() {
     fi
   fi
 
-  # Persist the loadout sidecar BEFORE the session file (#150 round-2 review:
-  # Finding 1). If the process is killed (OOM, task-done --force, host
-  # shutdown) between these two _atomic_write calls, the order matters:
+  # Persist the loadout and agent sidecars BEFORE the session file (#150
+  # round-2 review: Finding 1; extended for AGENT in #151). If the process is
+  # killed (OOM, task-done --force, host shutdown) between these writes, the
+  # order matters:
   #
   #   sidecar-first (this order):
-  #     pre-kill state:  .loadout=claude-gh, .info absent
-  #     re-seed reads:   .loadout → LOADOUT=claude-gh recovered ✓
+  #     pre-kill state:  .loadout=claude-gh, .agent=claude, .info absent
+  #     re-seed reads:   sidecars → LOADOUT/AGENT recovered ✓
   #
   #   info-first (the OLD order — pre-#150-r3):
-  #     pre-kill state:  .info has LOADOUT=claude-gh, .loadout absent
-  #     unregister cascade deletes .info; .loadout never existed
+  #     pre-kill state:  .info has LOADOUT/AGENT, sidecars absent
+  #     unregister cascade deletes .info; sidecars never existed
   #     re-seed reads:   no sidecar, hook subshell has no $TASK_FORCE_LOADOUT
-  #                      → LOADOUT=unknown ✗
+  #                      / $TASK_FORCE_AGENT → LOADOUT=unknown / AGENT=claude ✗
   #
   # The window is microseconds wide, but the cascade in #140 makes it
   # statistically reachable. Reversing the order eliminates the failure mode
-  # entirely. Skipping the sidecar on empty $loadout keeps the sidecar's mere
+  # entirely. Skipping the loadout sidecar on empty $loadout keeps its mere
   # existence equivalent to "we have a real loadout to restore" — otherwise
   # a re-seed could read an empty sidecar and clobber the env-var fallback
-  # that test paths still rely on.
+  # that test paths still rely on. The agent sidecar is always written
+  # because --agent is required (cmd_register exits 2 above if absent), so
+  # $agent is always a real value here.
   if [[ -n "$loadout" ]]; then
     printf '%s' "$loadout" | _atomic_write "$(_loadout_sidecar "$role")"
   fi
+  printf '%s' "$agent" | _atomic_write "$(_agent_sidecar "$role")"
 
   {
     printf 'ROLE=%s\nTAB=%s\nTAB_ID=%s\nREPO=%s\nSTATE=idle\nLAST_HEARTBEAT=%s\nAGENT=%s\nLOADOUT=%s\n' \
@@ -461,6 +489,22 @@ cmd_unregister() {
           _log "unregister: skipping (reason=$reason — intra-session event) role=$TASK_FORCE_ROLE"
           return 0
           ;;
+        "")
+          # Cascade pattern (#151): payload is present but contains no
+          # parseable `.reason` field. The PR-#150 diagnostic showed bursts of
+          # 144 unregister calls in ~25s with payload literally "y" and
+          # reason=<unset> — phantom invocations from somewhere upstream of
+          # Claude Code's documented SessionEnd hook (which always includes
+          # reason ∈ {clear, resume, logout, prompt_input_exit, other}).
+          # Treat these the same as clear/resume: known non-real-exit events
+          # that must not wipe the session file or the sidecars. Real exits
+          # still flow through the logout/prompt_input_exit/other branches
+          # below and clean up normally; manual invocations (no stdin) also
+          # proceed because `[[ ! -t 0 ]]` is false then.
+          payload_oneline=$(printf '%s' "$payload" | tr '\n' ' ' | tr -s ' ')
+          _log "unregister: skipping (reason=<unset> — cascade, no real-exit signal) role=$TASK_FORCE_ROLE payload=$payload_oneline"
+          return 0
+          ;;
       esac
     fi
     # Instrumentation for #140: when the hook fires with a payload that
@@ -468,7 +512,10 @@ cmd_unregister() {
     # what reason (or non-reason) is driving the unregister cascade. Empirically
     # observed as bursts of 20+ unregister calls in ~30s on long-running
     # worker sessions; the root cause needs the payload to investigate. Log
-    # is compacted to one line via tr so it doesn't fragment radio.log.
+    # is compacted to one line via tr so it doesn't fragment radio.log. Post-
+    # #151, an empty reason is already short-circuited above, so this line
+    # only fires for non-empty named reasons (logout, prompt_input_exit,
+    # other, or anything new Claude Code adds in the future).
     if [[ -n "$payload" ]]; then
       payload_oneline=$(printf '%s' "$payload" | tr '\n' ' ' | tr -s ' ')
       _log "unregister: proceeding (reason=${reason:-<unset>}) role=$TASK_FORCE_ROLE payload=$payload_oneline"
@@ -478,10 +525,11 @@ cmd_unregister() {
   local f
   f=$(_session_file "$TASK_FORCE_ROLE")
   rm -f "$f"
-  # Sweep the loadout sidecar too — leaving it behind would let a future
-  # _ensure_session_file resurrect a stale loadout for a role whose tab has
-  # really exited and been re-used (#140).
+  # Sweep the loadout + agent sidecars too — leaving them behind would let a
+  # future _ensure_session_file resurrect a stale loadout / agent for a role
+  # whose tab has really exited and been re-used (#140, #151).
   rm -f "$(_loadout_sidecar "$TASK_FORCE_ROLE")"
+  rm -f "$(_agent_sidecar "$TASK_FORCE_ROLE")"
   _log "unregister role=$TASK_FORCE_ROLE"
 }
 
diff --git a/kiro-gh/bin/task-done b/kiro-gh/bin/task-done
index b44dfc6..c627525 100755
--- a/kiro-gh/bin/task-done
+++ b/kiro-gh/bin/task-done
@@ -131,8 +131,14 @@ fi
 # `|| true` is a safety net: $TASK_FORCE_ROLE should be set inside a worker
 # tab, but if it isn't (e.g., task-done invoked from an unexpected shell)
 # the no-op must not abort cleanup. `radio unregister` itself already
-# silently exits when $TASK_FORCE_ROLE is unset (#93).
-radio unregister 2>/dev/null || true
+# silently exits when $TASK_FORCE_ROLE is unset (#93). Redirect stdin from
+# /dev/null so `radio unregister` doesn't inherit task-done's stdin — under
+# `--force` the calling shell may have piped `y` (or any other content)
+# to confirm something else, and post-#151 a non-empty stdin without a
+# parseable JSON reason triggers the cascade-skip path. That's correct
+# behaviour for SessionEnd hook invocations but wrong for explicit
+# task-done cleanup, which must always proceed with the unregister.
+radio unregister </dev/null 2>/dev/null || true
 
 # Move out of worktree before removing it
 cd "$MAIN_WORKTREE"
diff --git a/kiro-local/bin/radio b/kiro-local/bin/radio
index a091d7b..5ae3e6b 100755
--- a/kiro-local/bin/radio
+++ b/kiro-local/bin/radio
@@ -167,6 +167,17 @@ _loadout_sidecar() {
   printf '%s/%s.loadout' "$SESSIONS_DIR" "$1"
 }
 
+# Agent sidecar (#151). Same problem as LOADOUT: $TASK_FORCE_AGENT isn't
+# exported into Claude Code's hook subshells, so _ensure_session_file's
+# previous fallback to "${TASK_FORCE_AGENT:-claude}" silently wrote
+# AGENT=claude for kiro-* workers on every re-seed. Parallel sidecar, parallel
+# write/read/sweep semantics — no current runtime consumer, but a kiro worker
+# whose re-seeded session reports AGENT=claude is a footgun if anyone wires
+# AGENT-conditional behaviour later.
+_agent_sidecar() {
+  printf '%s/%s.agent' "$SESSIONS_DIR" "$1"
+}
+
 _inbox_dir()    { printf '%s/%s/inbox'     "$MAILBOX_DIR" "$1"; }
 _processed_dir(){ printf '%s/%s/processed' "$MAILBOX_DIR" "$1"; }
 
@@ -216,13 +227,26 @@ _ensure_session_file() {
   loadout=$(cat "$sidecar" 2>/dev/null || true)
   [[ -n "$loadout" ]] || loadout="${TASK_FORCE_LOADOUT:-unknown}"
 
+  # AGENT recovery (#151): same hook-subshell unset story as LOADOUT — the
+  # cascade wipes .info, and the next re-seed used to default to "claude"
+  # regardless of whether this was a kiro-* worker. Read the agent sidecar
+  # cmd_register persisted; fall back to the env var only for test paths that
+  # exercise _ensure_session_file directly. Same TOCTOU-safe `cat … || true`
+  # pattern as the loadout read above for the same reason (concurrent
+  # unregister race window).
+  local agent=""
+  local agent_sidecar
+  agent_sidecar=$(_agent_sidecar "$TASK_FORCE_ROLE")
+  agent=$(cat "$agent_sidecar" 2>/dev/null || true)
+  [[ -n "$agent" ]] || agent="${TASK_FORCE_AGENT:-claude}"
+
   local repo
   repo=$(git rev-parse --show-toplevel 2>/dev/null || echo "")
 
   {
     printf 'ROLE=%s\nTAB=%s\nTAB_ID=%s\nREPO=%s\nSTATE=idle\nLAST_HEARTBEAT=%s\nAGENT=%s\nLOADOUT=%s\n' \
       "$TASK_FORCE_ROLE" "$ZELLIJ_TAB" "$tab_id" "$repo" "$(_now)" \
-      "${TASK_FORCE_AGENT:-claude}" "$loadout"
+      "$agent" "$loadout"
     # Preserve the --auto opt-in across self-heal so cmd_send keeps using CR
     # for wake-up after an intra-session re-seed (#128). Use `if` rather than
     # `&&` so the brace group exits 0 when the flag is absent — otherwise
@@ -234,7 +258,7 @@ _ensure_session_file() {
   } | _atomic_write "$f"
 
   mkdir -p "$(_inbox_dir "$TASK_FORCE_ROLE")" "$(_processed_dir "$TASK_FORCE_ROLE")"
-  _log "ensure_session: re-seeded $TASK_FORCE_ROLE (file was missing) tab_id=$tab_id loadout=$loadout"
+  _log "ensure_session: re-seeded $TASK_FORCE_ROLE (file was missing) tab_id=$tab_id loadout=$loadout agent=$agent"
 }
 
 # Update STATE=… and LAST_HEARTBEAT=… on the current session file.
@@ -385,29 +409,33 @@ cmd_register() {
     fi
   fi
 
-  # Persist the loadout sidecar BEFORE the session file (#150 round-2 review:
-  # Finding 1). If the process is killed (OOM, task-done --force, host
-  # shutdown) between these two _atomic_write calls, the order matters:
+  # Persist the loadout and agent sidecars BEFORE the session file (#150
+  # round-2 review: Finding 1; extended for AGENT in #151). If the process is
+  # killed (OOM, task-done --force, host shutdown) between these writes, the
+  # order matters:
   #
   #   sidecar-first (this order):
-  #     pre-kill state:  .loadout=claude-gh, .info absent
-  #     re-seed reads:   .loadout → LOADOUT=claude-gh recovered ✓
+  #     pre-kill state:  .loadout=claude-gh, .agent=claude, .info absent
+  #     re-seed reads:   sidecars → LOADOUT/AGENT recovered ✓
   #
   #   info-first (the OLD order — pre-#150-r3):
-  #     pre-kill state:  .info has LOADOUT=claude-gh, .loadout absent
-  #     unregister cascade deletes .info; .loadout never existed
+  #     pre-kill state:  .info has LOADOUT/AGENT, sidecars absent
+  #     unregister cascade deletes .info; sidecars never existed
   #     re-seed reads:   no sidecar, hook subshell has no $TASK_FORCE_LOADOUT
-  #                      → LOADOUT=unknown ✗
+  #                      / $TASK_FORCE_AGENT → LOADOUT=unknown / AGENT=claude ✗
   #
   # The window is microseconds wide, but the cascade in #140 makes it
   # statistically reachable. Reversing the order eliminates the failure mode
-  # entirely. Skipping the sidecar on empty $loadout keeps the sidecar's mere
+  # entirely. Skipping the loadout sidecar on empty $loadout keeps its mere
   # existence equivalent to "we have a real loadout to restore" — otherwise
   # a re-seed could read an empty sidecar and clobber the env-var fallback
-  # that test paths still rely on.
+  # that test paths still rely on. The agent sidecar is always written
+  # because --agent is required (cmd_register exits 2 above if absent), so
+  # $agent is always a real value here.
   if [[ -n "$loadout" ]]; then
     printf '%s' "$loadout" | _atomic_write "$(_loadout_sidecar "$role")"
   fi
+  printf '%s' "$agent" | _atomic_write "$(_agent_sidecar "$role")"
 
   {
     printf 'ROLE=%s\nTAB=%s\nTAB_ID=%s\nREPO=%s\nSTATE=idle\nLAST_HEARTBEAT=%s\nAGENT=%s\nLOADOUT=%s\n' \
@@ -461,6 +489,22 @@ cmd_unregister() {
           _log "unregister: skipping (reason=$reason — intra-session event) role=$TASK_FORCE_ROLE"
           return 0
           ;;
+        "")
+          # Cascade pattern (#151): payload is present but contains no
+          # parseable `.reason` field. The PR-#150 diagnostic showed bursts of
+          # 144 unregister calls in ~25s with payload literally "y" and
+          # reason=<unset> — phantom invocations from somewhere upstream of
+          # Claude Code's documented SessionEnd hook (which always includes
+          # reason ∈ {clear, resume, logout, prompt_input_exit, other}).
+          # Treat these the same as clear/resume: known non-real-exit events
+          # that must not wipe the session file or the sidecars. Real exits
+          # still flow through the logout/prompt_input_exit/other branches
+          # below and clean up normally; manual invocations (no stdin) also
+          # proceed because `[[ ! -t 0 ]]` is false then.
+          payload_oneline=$(printf '%s' "$payload" | tr '\n' ' ' | tr -s ' ')
+          _log "unregister: skipping (reason=<unset> — cascade, no real-exit signal) role=$TASK_FORCE_ROLE payload=$payload_oneline"
+          return 0
+          ;;
       esac
     fi
     # Instrumentation for #140: when the hook fires with a payload that
@@ -468,7 +512,10 @@ cmd_unregister() {
     # what reason (or non-reason) is driving the unregister cascade. Empirically
     # observed as bursts of 20+ unregister calls in ~30s on long-running
     # worker sessions; the root cause needs the payload to investigate. Log
-    # is compacted to one line via tr so it doesn't fragment radio.log.
+    # is compacted to one line via tr so it doesn't fragment radio.log. Post-
+    # #151, an empty reason is already short-circuited above, so this line
+    # only fires for non-empty named reasons (logout, prompt_input_exit,
+    # other, or anything new Claude Code adds in the future).
     if [[ -n "$payload" ]]; then
       payload_oneline=$(printf '%s' "$payload" | tr '\n' ' ' | tr -s ' ')
       _log "unregister: proceeding (reason=${reason:-<unset>}) role=$TASK_FORCE_ROLE payload=$payload_oneline"
@@ -478,10 +525,11 @@ cmd_unregister() {
   local f
   f=$(_session_file "$TASK_FORCE_ROLE")
   rm -f "$f"
-  # Sweep the loadout sidecar too — leaving it behind would let a future
-  # _ensure_session_file resurrect a stale loadout for a role whose tab has
-  # really exited and been re-used (#140).
+  # Sweep the loadout + agent sidecars too — leaving them behind would let a
+  # future _ensure_session_file resurrect a stale loadout / agent for a role
+  # whose tab has really exited and been re-used (#140, #151).
   rm -f "$(_loadout_sidecar "$TASK_FORCE_ROLE")"
+  rm -f "$(_agent_sidecar "$TASK_FORCE_ROLE")"
   _log "unregister role=$TASK_FORCE_ROLE"
 }
 
diff --git a/kiro-local/bin/task-done b/kiro-local/bin/task-done
index a5a1b63..21f923a 100755
--- a/kiro-local/bin/task-done
+++ b/kiro-local/bin/task-done
@@ -133,8 +133,14 @@ fi
 # `|| true` is a safety net: $TASK_FORCE_ROLE should be set inside a worker
 # tab, but if it isn't (e.g., task-done invoked from an unexpected shell)
 # the no-op must not abort cleanup. `radio unregister` itself already
-# silently exits when $TASK_FORCE_ROLE is unset (#93).
-radio unregister 2>/dev/null || true
+# silently exits when $TASK_FORCE_ROLE is unset (#93). Redirect stdin from
+# /dev/null so `radio unregister` doesn't inherit task-done's stdin — under
+# `--force` the calling shell may have piped `y` (or any other content)
+# to confirm something else, and post-#151 a non-empty stdin without a
+# parseable JSON reason triggers the cascade-skip path. That's correct
+# behaviour for SessionEnd hook invocations but wrong for explicit
+# task-done cleanup, which must always proceed with the unregister.
+radio unregister </dev/null 2>/dev/null || true
 
 # Move out of worktree before removing it
 cd "$MAIN_WORKTREE"
diff --git a/kiro-notion/bin/radio b/kiro-notion/bin/radio
index a091d7b..5ae3e6b 100755
--- a/kiro-notion/bin/radio
+++ b/kiro-notion/bin/radio
@@ -167,6 +167,17 @@ _loadout_sidecar() {
   printf '%s/%s.loadout' "$SESSIONS_DIR" "$1"
 }
 
+# Agent sidecar (#151). Same problem as LOADOUT: $TASK_FORCE_AGENT isn't
+# exported into Claude Code's hook subshells, so _ensure_session_file's
+# previous fallback to "${TASK_FORCE_AGENT:-claude}" silently wrote
+# AGENT=claude for kiro-* workers on every re-seed. Parallel sidecar, parallel
+# write/read/sweep semantics — no current runtime consumer, but a kiro worker
+# whose re-seeded session reports AGENT=claude is a footgun if anyone wires
+# AGENT-conditional behaviour later.
+_agent_sidecar() {
+  printf '%s/%s.agent' "$SESSIONS_DIR" "$1"
+}
+
 _inbox_dir()    { printf '%s/%s/inbox'     "$MAILBOX_DIR" "$1"; }
 _processed_dir(){ printf '%s/%s/processed' "$MAILBOX_DIR" "$1"; }
 
@@ -216,13 +227,26 @@ _ensure_session_file() {
   loadout=$(cat "$sidecar" 2>/dev/null || true)
   [[ -n "$loadout" ]] || loadout="${TASK_FORCE_LOADOUT:-unknown}"
 
+  # AGENT recovery (#151): same hook-subshell unset story as LOADOUT — the
+  # cascade wipes .info, and the next re-seed used to default to "claude"
+  # regardless of whether this was a kiro-* worker. Read the agent sidecar
+  # cmd_register persisted; fall back to the env var only for test paths that
+  # exercise _ensure_session_file directly. Same TOCTOU-safe `cat … || true`
+  # pattern as the loadout read above for the same reason (concurrent
+  # unregister race window).
+  local agent=""
+  local agent_sidecar
+  agent_sidecar=$(_agent_sidecar "$TASK_FORCE_ROLE")
+  agent=$(cat "$agent_sidecar" 2>/dev/null || true)
+  [[ -n "$agent" ]] || agent="${TASK_FORCE_AGENT:-claude}"
+
   local repo
   repo=$(git rev-parse --show-toplevel 2>/dev/null || echo "")
 
   {
     printf 'ROLE=%s\nTAB=%s\nTAB_ID=%s\nREPO=%s\nSTATE=idle\nLAST_HEARTBEAT=%s\nAGENT=%s\nLOADOUT=%s\n' \
       "$TASK_FORCE_ROLE" "$ZELLIJ_TAB" "$tab_id" "$repo" "$(_now)" \
-      "${TASK_FORCE_AGENT:-claude}" "$loadout"
+      "$agent" "$loadout"
     # Preserve the --auto opt-in across self-heal so cmd_send keeps using CR
     # for wake-up after an intra-session re-seed (#128). Use `if` rather than
     # `&&` so the brace group exits 0 when the flag is absent — otherwise
@@ -234,7 +258,7 @@ _ensure_session_file() {
   } | _atomic_write "$f"
 
   mkdir -p "$(_inbox_dir "$TASK_FORCE_ROLE")" "$(_processed_dir "$TASK_FORCE_ROLE")"
-  _log "ensure_session: re-seeded $TASK_FORCE_ROLE (file was missing) tab_id=$tab_id loadout=$loadout"
+  _log "ensure_session: re-seeded $TASK_FORCE_ROLE (file was missing) tab_id=$tab_id loadout=$loadout agent=$agent"
 }
 
 # Update STATE=… and LAST_HEARTBEAT=… on the current session file.
@@ -385,29 +409,33 @@ cmd_register() {
     fi
   fi
 
-  # Persist the loadout sidecar BEFORE the session file (#150 round-2 review:
-  # Finding 1). If the process is killed (OOM, task-done --force, host
-  # shutdown) between these two _atomic_write calls, the order matters:
+  # Persist the loadout and agent sidecars BEFORE the session file (#150
+  # round-2 review: Finding 1; extended for AGENT in #151). If the process is
+  # killed (OOM, task-done --force, host shutdown) between these writes, the
+  # order matters:
   #
   #   sidecar-first (this order):
-  #     pre-kill state:  .loadout=claude-gh, .info absent
-  #     re-seed reads:   .loadout → LOADOUT=claude-gh recovered ✓
+  #     pre-kill state:  .loadout=claude-gh, .agent=claude, .info absent
+  #     re-seed reads:   sidecars → LOADOUT/AGENT recovered ✓
   #
   #   info-first (the OLD order — pre-#150-r3):
-  #     pre-kill state:  .info has LOADOUT=claude-gh, .loadout absent
-  #     unregister cascade deletes .info; .loadout never existed
+  #     pre-kill state:  .info has LOADOUT/AGENT, sidecars absent
+  #     unregister cascade deletes .info; sidecars never existed
   #     re-seed reads:   no sidecar, hook subshell has no $TASK_FORCE_LOADOUT
-  #                      → LOADOUT=unknown ✗
+  #                      / $TASK_FORCE_AGENT → LOADOUT=unknown / AGENT=claude ✗
   #
   # The window is microseconds wide, but the cascade in #140 makes it
   # statistically reachable. Reversing the order eliminates the failure mode
-  # entirely. Skipping the sidecar on empty $loadout keeps the sidecar's mere
+  # entirely. Skipping the loadout sidecar on empty $loadout keeps its mere
   # existence equivalent to "we have a real loadout to restore" — otherwise
   # a re-seed could read an empty sidecar and clobber the env-var fallback
-  # that test paths still rely on.
+  # that test paths still rely on. The agent sidecar is always written
+  # because --agent is required (cmd_register exits 2 above if absent), so
+  # $agent is always a real value here.
   if [[ -n "$loadout" ]]; then
     printf '%s' "$loadout" | _atomic_write "$(_loadout_sidecar "$role")"
   fi
+  printf '%s' "$agent" | _atomic_write "$(_agent_sidecar "$role")"
 
   {
     printf 'ROLE=%s\nTAB=%s\nTAB_ID=%s\nREPO=%s\nSTATE=idle\nLAST_HEARTBEAT=%s\nAGENT=%s\nLOADOUT=%s\n' \
@@ -461,6 +489,22 @@ cmd_unregister() {
           _log "unregister: skipping (reason=$reason — intra-session event) role=$TASK_FORCE_ROLE"
           return 0
           ;;
+        "")
+          # Cascade pattern (#151): payload is present but contains no
+          # parseable `.reason` field. The PR-#150 diagnostic showed bursts of
+          # 144 unregister calls in ~25s with payload literally "y" and
+          # reason=<unset> — phantom invocations from somewhere upstream of
+          # Claude Code's documented SessionEnd hook (which always includes
+          # reason ∈ {clear, resume, logout, prompt_input_exit, other}).
+          # Treat these the same as clear/resume: known non-real-exit events
+          # that must not wipe the session file or the sidecars. Real exits
+          # still flow through the logout/prompt_input_exit/other branches
+          # below and clean up normally; manual invocations (no stdin) also
+          # proceed because `[[ ! -t 0 ]]` is false then.
+          payload_oneline=$(printf '%s' "$payload" | tr '\n' ' ' | tr -s ' ')
+          _log "unregister: skipping (reason=<unset> — cascade, no real-exit signal) role=$TASK_FORCE_ROLE payload=$payload_oneline"
+          return 0
+          ;;
       esac
     fi
     # Instrumentation for #140: when the hook fires with a payload that
@@ -468,7 +512,10 @@ cmd_unregister() {
     # what reason (or non-reason) is driving the unregister cascade. Empirically
     # observed as bursts of 20+ unregister calls in ~30s on long-running
     # worker sessions; the root cause needs the payload to investigate. Log
-    # is compacted to one line via tr so it doesn't fragment radio.log.
+    # is compacted to one line via tr so it doesn't fragment radio.log. Post-
+    # #151, an empty reason is already short-circuited above, so this line
+    # only fires for non-empty named reasons (logout, prompt_input_exit,
+    # other, or anything new Claude Code adds in the future).
     if [[ -n "$payload" ]]; then
       payload_oneline=$(printf '%s' "$payload" | tr '\n' ' ' | tr -s ' ')
       _log "unregister: proceeding (reason=${reason:-<unset>}) role=$TASK_FORCE_ROLE payload=$payload_oneline"
@@ -478,10 +525,11 @@ cmd_unregister() {
   local f
   f=$(_session_file "$TASK_FORCE_ROLE")
   rm -f "$f"
-  # Sweep the loadout sidecar too — leaving it behind would let a future
-  # _ensure_session_file resurrect a stale loadout for a role whose tab has
-  # really exited and been re-used (#140).
+  # Sweep the loadout + agent sidecars too — leaving them behind would let a
+  # future _ensure_session_file resurrect a stale loadout / agent for a role
+  # whose tab has really exited and been re-used (#140, #151).
   rm -f "$(_loadout_sidecar "$TASK_FORCE_ROLE")"
+  rm -f "$(_agent_sidecar "$TASK_FORCE_ROLE")"
   _log "unregister role=$TASK_FORCE_ROLE"
 }
 
diff --git a/kiro-notion/bin/task-done b/kiro-notion/bin/task-done
index b44dfc6..c627525 100755
--- a/kiro-notion/bin/task-done
+++ b/kiro-notion/bin/task-done
@@ -131,8 +131,14 @@ fi
 # `|| true` is a safety net: $TASK_FORCE_ROLE should be set inside a worker
 # tab, but if it isn't (e.g., task-done invoked from an unexpected shell)
 # the no-op must not abort cleanup. `radio unregister` itself already
-# silently exits when $TASK_FORCE_ROLE is unset (#93).
-radio unregister 2>/dev/null || true
+# silently exits when $TASK_FORCE_ROLE is unset (#93). Redirect stdin from
+# /dev/null so `radio unregister` doesn't inherit task-done's stdin — under
+# `--force` the calling shell may have piped `y` (or any other content)
+# to confirm something else, and post-#151 a non-empty stdin without a
+# parseable JSON reason triggers the cascade-skip path. That's correct
+# behaviour for SessionEnd hook invocations but wrong for explicit
+# task-done cleanup, which must always proceed with the unregister.
+radio unregister </dev/null 2>/dev/null || true
 
 # Move out of worktree before removing it
 cd "$MAIN_WORKTREE"
diff --git a/tests/radio_lifecycle.bats b/tests/radio_lifecycle.bats
index b58af7b..722b5fe 100644
--- a/tests/radio_lifecycle.bats
+++ b/tests/radio_lifecycle.bats
@@ -84,20 +84,58 @@ teardown() {
   assert [ ! -f "$sess" ]
 }
 
-@test "unregister proceeds when stdin payload is not valid JSON" {
+@test "unregister skips when stdin payload is not valid JSON (cascade pattern #151)" {
+  # Pre-#151 this proceeded with the delete: jq returned an empty reason,
+  # nothing matched the skip-list, the file got wiped. The diagnostic logging
+  # added in PR #150 surfaced the actual cascade payload — literally a single
+  # "y" character, 144 instances in 25s on one long-running worker session.
+  # That's not a Claude Code SessionEnd hook firing (those always include a
+  # parseable JSON reason); it's a phantom invocation we don't want to act on.
+  # Treat any payload-present-but-no-reason input the same as clear/resume.
   "$RADIO" register --role worker-foo --tab w-foo --agent claude
   local sess="$TASK_FORCE_HOME/radio/sessions/worker-foo.info"
   TASK_FORCE_ROLE=worker-foo run bash -c "echo 'not json' | '$RADIO' unregister"
   assert_success
-  assert [ ! -f "$sess" ]
+  assert [ -f "$sess" ]
+  run cat "$TASK_FORCE_HOME/radio/log"
+  assert_output --partial "skipping (reason=<unset>"
+  assert_output --partial "cascade"
 }
 
-@test "unregister proceeds when payload JSON has no reason field" {
+@test "unregister skips when payload JSON has no reason field (cascade pattern #151)" {
+  # Same as above, but with valid JSON whose `.reason` is missing. jq -r
+  # '.reason // empty' returns empty here too; the cascade case matches.
   "$RADIO" register --role worker-foo --tab w-foo --agent claude
   local sess="$TASK_FORCE_HOME/radio/sessions/worker-foo.info"
   TASK_FORCE_ROLE=worker-foo run bash -c "echo '{\"other_field\":\"value\"}' | '$RADIO' unregister"
   assert_success
-  assert [ ! -f "$sess" ]
+  assert [ -f "$sess" ]
+  run cat "$TASK_FORCE_HOME/radio/log"
+  assert_output --partial "skipping (reason=<unset>"
+}
+
+@test "unregister skips when payload is the literal 'y' observed in #151 logs (cascade pattern)" {
+  # The smoking-gun payload from #151's PR-#150-diagnostic logs: a single
+  # "y" character. 144 invocations in 25s, all identical, all reason=<unset>.
+  # Source uncertain (likely a Claude Code subagent termination leaking the
+  # parent's TUI confirmation keystroke into the SessionEnd hook stdin), but
+  # the fix is the same regardless of source: skip when reason is unparseable.
+  "$RADIO" register --role worker-foo --tab w-foo --agent claude --loadout claude-gh
+  local sess="$TASK_FORCE_HOME/radio/sessions/worker-foo.info"
+  local loadout_sidecar="$TASK_FORCE_HOME/radio/sessions/worker-foo.loadout"
+  local agent_sidecar="$TASK_FORCE_HOME/radio/sessions/worker-foo.agent"
+  assert [ -f "$sess" ]
+  assert [ -f "$loadout_sidecar" ]
+  assert [ -f "$agent_sidecar" ]
+
+  # Single non-JSON character on stdin, exactly as the cascade fires it.
+  TASK_FORCE_ROLE=worker-foo run bash -c "printf 'y' | '$RADIO' unregister"
+  assert_success
+  # Session file AND both sidecars must survive — otherwise the next
+  # _ensure_session_file would write LOADOUT=unknown / AGENT=claude.
+  assert [ -f "$sess" ]
+  assert [ -f "$loadout_sidecar" ]
+  assert [ -f "$agent_sidecar" ]
 }
 
 # ----- register-if-missing (self-healing) -----------------------------------
@@ -510,11 +548,143 @@ teardown() {
   assert [ -f "$sidecar" ]
 }
 
+# ----- #151: AGENT sidecar (parallel to LOADOUT) ----------------------------
+#
+# Same hook-subshell unset problem _ensure_session_file had for $TASK_FORCE_LOADOUT
+# applies to $TASK_FORCE_AGENT. Pre-#151 a kiro-* worker that survived the
+# cascade and re-seeded ended up with AGENT=claude (the literal fallback in
+# the printf format string), silently flipping its identity. No runtime
+# consumer breaks today, but the sidecar is cheap and the alternative is a
+# trap for whoever adds AGENT-conditional behaviour next.
+
+@test "register: writes agent sidecar alongside session file (#151)" {
+  "$RADIO" register --role worker-foo --tab worker-foo --agent kiro --loadout kiro-gh
+  local sidecar="$TASK_FORCE_HOME/radio/sessions/worker-foo.agent"
+  assert [ -f "$sidecar" ]
+  run cat "$sidecar"
+  assert_output "kiro"
+}
+
+@test "re-seed after unregister recovers AGENT from sidecar (#151)" {
+  # Mirror of the LOADOUT recovery test above: register as kiro, wipe the
+  # .info, re-seed via busy with $TASK_FORCE_AGENT unset (matches the hook
+  # subshell). Without the sidecar, the printf format string's "${...:-claude}"
+  # fallback would write AGENT=claude — silently misrepresenting the worker's
+  # identity.
+  "$RADIO" register --role worker-foo --tab worker-foo --agent kiro --loadout kiro-gh
+  local sess="$TASK_FORCE_HOME/radio/sessions/worker-foo.info"
+  run grep "^AGENT=" "$sess"
+  assert_output "AGENT=kiro"
+
+  rm -f "$sess"
+
+  TASK_FORCE_ROLE=worker-foo ZELLIJ_TAB=worker-foo run env -u TASK_FORCE_AGENT "$RADIO" busy
+  assert_success
+  run grep "^AGENT=" "$sess"
+  assert_output "AGENT=kiro"
+  refute_output --partial "claude"
+}
+
+@test "re-seed AGENT falls back to env var when sidecar is absent (#151)" {
+  # Test-harness escape hatch: directly poke _ensure_session_file without a
+  # prior register (so no sidecar exists). The env var fallback must still
+  # work — same shape as the loadout fallback at the same point.
+  local sess="$TASK_FORCE_HOME/radio/sessions/worker-foo.info"
+  assert [ ! -f "$sess" ]
+
+  TASK_FORCE_ROLE=worker-foo ZELLIJ_TAB=worker-foo TASK_FORCE_AGENT=kiro run "$RADIO" busy
+  assert_success
+  run grep "^AGENT=" "$sess"
+  assert_output "AGENT=kiro"
+}
+
+@test "re-seed AGENT defaults to 'claude' when no sidecar and no env var (#151)" {
+  # Last-resort fallback for the no-identity-context case (preserves the
+  # pre-#151 default so we don't regress non-task-force test paths).
+  local sess="$TASK_FORCE_HOME/radio/sessions/worker-foo.info"
+  TASK_FORCE_ROLE=worker-foo ZELLIJ_TAB=worker-foo run env -u TASK_FORCE_AGENT "$RADIO" busy
+  assert_success
+  run grep "^AGENT=" "$sess"
+  assert_output "AGENT=claude"
+}
+
+@test "unregister: sweeps agent sidecar so a stale value can't leak (#151)" {
+  # Symmetric to the loadout sweep: real-exit unregister must remove the
+  # agent sidecar too, otherwise a tab reused for a different role would
+  # inherit the previous AGENT value on its first re-seed.
+  "$RADIO" register --role worker-foo --tab worker-foo --agent kiro --loadout kiro-gh
+  local sess="$TASK_FORCE_HOME/radio/sessions/worker-foo.info"
+  local agent_sidecar="$TASK_FORCE_HOME/radio/sessions/worker-foo.agent"
+  assert [ -f "$agent_sidecar" ]
+
+  TASK_FORCE_ROLE=worker-foo run bash -c "echo '{\"reason\":\"logout\"}' | '$RADIO' unregister"
+  assert_success
+  assert [ ! -f "$sess" ]
+  assert [ ! -f "$agent_sidecar" ]
+}
+
+@test "unregister: skipped unregister (reason=clear) does NOT sweep agent sidecar (#151)" {
+  # Symmetric to the loadout no-sweep-on-skip test. If we skipped the .info
+  # delete, we must skip the sidecar delete too — otherwise the next re-seed
+  # rebuilds with the wrong AGENT.
+  "$RADIO" register --role worker-foo --tab worker-foo --agent kiro --loadout kiro-gh
+  local agent_sidecar="$TASK_FORCE_HOME/radio/sessions/worker-foo.agent"
+  assert [ -f "$agent_sidecar" ]
+
+  TASK_FORCE_ROLE=worker-foo run bash -c "echo '{\"reason\":\"clear\"}' | '$RADIO' unregister"
+  assert_success
+  assert [ -f "$agent_sidecar" ]
+}
+
+@test "unregister: cascade-skipped unregister (reason=<unset>) does NOT sweep sidecars (#151)" {
+  # The new empty-reason skip branch must preserve both sidecars too — same
+  # invariant as clear/resume. This is the realistic worker-life scenario:
+  # 144 of these fire in 25s, each must be a no-op.
+  "$RADIO" register --role worker-foo --tab worker-foo --agent kiro --loadout kiro-gh
+  local sess="$TASK_FORCE_HOME/radio/sessions/worker-foo.info"
+  local loadout_sidecar="$TASK_FORCE_HOME/radio/sessions/worker-foo.loadout"
+  local agent_sidecar="$TASK_FORCE_HOME/radio/sessions/worker-foo.agent"
+
+  TASK_FORCE_ROLE=worker-foo run bash -c "printf 'y' | '$RADIO' unregister"
+  assert_success
+  assert [ -f "$sess" ]
+  assert [ -f "$loadout_sidecar" ]
+  assert [ -f "$agent_sidecar" ]
+}
+
+@test "end-to-end: cascade burst leaves LOADOUT + AGENT + TAB_ID intact (#151)" {
+  # Replays the #140/#151 cascade pattern: 20 unregister calls with the "y"
+  # payload, fired in rapid succession. The session file plus both sidecars
+  # must still be there at the end, and the values must be the original
+  # registration values — not the "unknown" / "claude" fallbacks that would
+  # land if any of the 20 calls had slipped through.
+  setup_stubs
+  seed_zellij_tabs worker-foo
+  export ZELLIJ=fake
+
+  "$RADIO" register --role worker-foo --tab worker-foo --agent kiro --loadout kiro-gh
+  local sess="$TASK_FORCE_HOME/radio/sessions/worker-foo.info"
+
+  for _ in $(seq 1 20); do
+    TASK_FORCE_ROLE=worker-foo run bash -c "printf 'y' | '$RADIO' unregister"
+    assert_success
+  done
+
+  # Original identity preserved end-to-end.
+  run grep "^LOADOUT=" "$sess"
+  assert_output "LOADOUT=kiro-gh"
+  run grep "^AGENT=" "$sess"
+  assert_output "AGENT=kiro"
+  run grep "^TAB_ID=" "$sess"
+  assert_output "TAB_ID=7"
+}
+
 @test "unregister: logs full payload when proceeding past the skip-list (#140 Fix A instrumentation)" {
-  # When the cascade fires with a reason we don't recognise (or no reason
-  # at all), we still proceed with the delete — but log the full payload so
-  # we can investigate what's driving the cascade. Without the payload in
-  # the log, the cascade is invisible.
+  # For non-empty reasons we don't explicitly recognise (anything outside
+  # the clear|resume skip-list and the empty-reason cascade case added in
+  # #151), we still proceed with the delete — but log the full payload so
+  # the next time Claude Code adds a real-exit reason we can spot it. The
+  # empty-reason path now skips (#151) and is exercised by the test below.
   "$RADIO" register --role worker-foo --tab worker-foo --agent claude
   TASK_FORCE_ROLE=worker-foo run bash -c "echo '{\"reason\":\"weird_event\",\"extra\":\"data\"}' | '$RADIO' unregister"
   assert_success
@@ -525,13 +695,16 @@ teardown() {
   assert_output --partial "extra"
 }
 
-@test "unregister: logs payload even when reason is missing (#140 Fix A instrumentation)" {
+@test "unregister: logs payload even when reason is missing (#140 Fix A → #151 skip)" {
   # The smoking gun in #140 was unregister calls with no parseable reason.
-  # Make sure we log the payload then too.
+  # Post-#151 those route to the skip branch (cascade pattern) — but we still
+  # log the payload, so a future shift in the cascade source can be diagnosed
+  # without losing the diagnostic surface.
   "$RADIO" register --role worker-foo --tab worker-foo --agent claude
   TASK_FORCE_ROLE=worker-foo run bash -c "echo '{\"other\":\"value\"}' | '$RADIO' unregister"
   assert_success
   run cat "$TASK_FORCE_HOME/radio/log"
-  assert_output --partial "unregister: proceeding (reason=<unset>)"
+  assert_output --partial "unregister: skipping (reason=<unset>"
   assert_output --partial "payload="
+  assert_output --partial "other"
 }