handoff

name	handoff
description	Generate a structured handoff document + ready-to-paste starting prompt for the next session, preserving context across session boundaries. **Use `/handoff` whenever you reach context limits, need to hand off to a colleague, or want to continue in a fresh session.** Modes: `/handoff` (manual mode, output prompt), `/handoff auto` (auto-launch next session). Includes state summary, acceptance criteria, references — no manual reconstruction needed.
argument-hint	[auto] [optional extra instructions for the next session]
user-invocable	true
allowed-tools	Read, Write, Bash, Glob, Grep

/handoff — Session Handoff & Continuation

You are executing the handoff skill. This is the only entry point for handoff — nothing triggers automatically. Follow these steps precisely.

Invocation modes

Parse $ARGUMENTS:

Trigger	Mode	Behavior
/handoff (no args)	manual	Write doc + output starting prompt in chat. Do NOT launch a new session. Old session stays alive by user choice.
/handoff <instructions>	manual + extra	Same as manual; put <instructions> into the "User Instructions" section of the handoff doc.
/handoff auto	auto	Write doc + output starting prompt + auto-launch new session via claude CLI after Pre-Termination Checklist passes. Old session should /exit after — auto mode treats the old session as a terminal event.
/handoff auto <instructions>	auto + extra	Same as auto, with extra instructions embedded.

Default (no explicit auto): manual mode. Never auto-launch without an explicit auto token as the first whitespace-delimited argument.

Note on /handoff:auto: Claude Code's colon syntax (<x>:<y>) is reserved for plugin namespacing (e.g. /plugin-name:skill-name). A project-level skill registered as handoff only resolves via /handoff, and /handoff:auto is NOT a valid slash invocation for this skill — the parser will treat it as an unknown command. Always use /handoff auto (space-delimited).

Strict parsing: auto must be the sole argument or the first whitespace-delimited token (i.e., /handoff auto <extra> is auto+extra, /handoff automatic is manual with instructions "automatic"). This prevents accidental auto-spawn from user instructions that happen to start with "auto".

Terminal-event semantics: "handoff is a terminal event for the old session" only applies to auto mode — the old session is expected to /exit immediately after spawning the new one. In manual mode the skill does NOT terminate the session; the user decides whether to /exit, paste the prompt into a fresh session elsewhere, or keep working. Both are valid; the skill itself writes the doc and outputs the prompt, nothing else.

Step 1: Gather Context

Layer these sources (each optional):

Layer 1: Conversation context (always available)

You have the full conversation in context. Synthesize:

• What the user was working on
• Decisions made and their rationale
• Problems encountered and solutions found
• Incomplete work and known next steps

Layer 2: Memory search (agentic)

Search the project's auto-memory directory:

~/.claude/projects/<encoded_cwd>/memory/

Where <encoded_cwd> is the cwd with : \ / replaced by -, leading - stripped.

Glob for *.md. Read previous handoffs, checkpoints, project memories.

Layer 3: Project documentation (if present)

Skim CLAUDE.md, AGENTS.md, README.md at project root or parents. Extract what's relevant to the handoff.

Layer 4: Version control (optional)

If git is available:

git status --short 2>/dev/null
git log --oneline -5 2>/dev/null
git branch --show-current 2>/dev/null

Layer 5: GitHub Project / Issues (best-effort — skip cleanly if unavailable)

If the project uses GitHub Issues + a GitHub Project (v2), query for next-task selection. This layer is best-effort: if gh is missing, unauthenticated, or the repo has no Project, skip this layer and fall back to Layers 1–4 + .mercury/docs/EXECUTION-PLAN.md (or the repo's equivalent plan). Never let a Layer 5 failure block the handoff.

# Pre-flight: bail out gracefully if gh is unavailable or unauthenticated.
if ! command -v gh >/dev/null 2>&1 || ! gh auth status >/dev/null 2>&1; then
  echo "INFO: gh CLI unavailable — skipping Layer 5"
else
  gh issue list --label "P0" --state open --json number,title,labels --limit 50 2>/dev/null || true
  gh issue list --label "P1" --state open --json number,title,labels --limit 50 2>/dev/null || true

  # Project number: configurable via $HANDOFF_PROJECT_NUM. No per-repo
  # auto-fallback — the skill stays agnostic about which GitHub Project
  # belongs to which repo. Callers that want Project integration (e.g.
  # Mercury with Project #3) set the env var in their shell profile or
  # per-session before invoking /handoff.
  OWNER=$(gh repo view --json owner --jq '.owner.login' 2>/dev/null)
  PROJ_NUM="${HANDOFF_PROJECT_NUM:-}"

  if [ -z "$OWNER" ]; then
    echo "INFO: could not resolve repo owner via gh — skipping Project query"
  elif [ -n "$PROJ_NUM" ]; then
    gh project item-list "$PROJ_NUM" --owner "$OWNER" --format json --limit 100 2>/dev/null | \
      python -c "
import json, sys
try:
    data = json.loads(sys.stdin.read() or '{}')
except json.JSONDecodeError:
    sys.exit(0)  # gh returned empty/invalid — silently skip
items = [i for i in data.get('items', []) if i.get('status') in ('Todo', 'In Progress')]
status_order = {'In Progress': 0, 'Todo': 1}
for i in sorted(items, key=lambda x: (status_order.get(x.get('status', ''), 9), x.get('priority', 'P9'))):
    num = i.get('content', {}).get('number', '?')
    print(f'#{num} [{i.get(\"priority\",\"?\")}] {i.get(\"title\",\"?\")} ({i.get(\"status\",\"?\")})')
" 2>/dev/null || true
  else
    echo "INFO: HANDOFF_PROJECT_NUM not set — skipping Project query (set it to enable)"
  fi
fi

Selection criteria (in order):

1. Actively blocked P1 bugs with known root cause
2. In-Progress items from the Project board
3. Highest-priority P0 Todo from Project board
4. Next Phase sub-item per .mercury/docs/EXECUTION-PLAN.md (or equivalent)

Pick one primary task + one secondary fallback. Never produce a menu.

Step 2: Generate Handoff Document

Write to:

~/.claude/projects/<encoded_cwd>/memory/session-handoff.md

---
name: session_handoff
description: "Session handoff — <one-line summary>"
type: project
---
# Session Handoff — <YYYY-MM-DD>

## Starting Prompt

这是 S{N+1}。<1-line context>。

### 当前状态
<repo / branch / commit / clean or dirty>

### S{N+1} 主任务：<Issue #N — specific title>

**背景**：<1-2 lines why this is highest priority, cite Issue/Project>

**执行步骤**：
1. <actionable step with file paths / commands>
2. <actionable step>
3. <verification>
4. <commit / PR>

**次要任务（主任务完成后）**：<Issue #N or Phase X-Y, one line>

### 参考文档
<only main-task-related docs>

## Task State
- **Primary Issue**: #N [title] (status)
- **Branch**: <branch>
- **Completed**: <commits + what they did>
- **In Progress**: <current step / blockers>
- **Pending**: <remaining items>

## Key Context (compact-loss protection)
- <architecture decisions not recoverable from code>
- <gotchas / constraints>
- <important file paths + roles>

## User Instructions
<If args passed in, embed here. Else "No additional instructions.">

CRITICAL RULE for Starting Prompt: one primary task with numbered execution steps. Never a menu of options. The next session must be able to start executing step 1 without asking for direction.

Step 3: Session-chain update (best-effort, optional)

Session-chain tracking is provided by the claude-handoff plugin (see github.com/392fyc/claude-handoff). If the plugin's session_chain DB exists, record this handoff edge:

python -c "
import os, sys
from pathlib import Path

# Plugin DB default location (claude-handoff plugin)
db_path = Path(os.environ.get('CLAUDE_HANDOFF_DB') or
                Path.home() / '.claude' / 'handoff' / 'session_chain.db')
if not db_path.exists():
    print('session_chain DB not found — skipping (plugin not installed or scaffold-only)')
    sys.exit(0)

# Defer actual writes to the plugin's session_chain package; do not duplicate
# schema logic here. If the package is importable, use it; else skip.
try:
    from session_chain import SessionChainDB
except ImportError:
    print('session_chain package not importable — skipping (scaffold not wired yet)')
    sys.exit(0)

db = SessionChainDB(db_path)
parent = os.environ.get('CLAUDE_SESSION_ID')
if not parent:
    print('CLAUDE_SESSION_ID not set — cannot record handoff edge')
    sys.exit(0)

db.record_handoff(
    chain_id=os.environ.get('CLAUDE_HANDOFF_CHAIN_ID') or parent,
    parent_session_id=parent,
    child_session_id=None,  # bound later by child session's SessionStart hook
    project_dir=os.getcwd(),
    task_ref=os.environ.get('CLAUDE_HANDOFF_TASK_REF'),
)
print('session_chain edge recorded (child pending)')
"

IMPORTANT: the AGENTKB-based orchestrator path ($AGENTKB_DIR/scripts/handoff-orchestrator.py) is deprecated. Do not call it. The replacement is the claude-handoff plugin's session_chain module (above), currently a scaffold — write side may not yet be wired at session-start.py.

Step 4: Pre-Termination Checklist

Before launching a new session (auto mode) OR outputting the prompt (manual mode), verify all in-flight work has finished or been explicitly deferred. In auto mode, the handoff is a terminal event for the old session — once the new session is spawned, the old session should /exit. In manual mode, producing the handoff prompt is not itself a terminal event; the output is a stable snapshot that the next session (or the current session continuing) can pick up from. In either mode, nothing carries over automatically to the next session unless it goes through the written handoff document + auto-memory path.

Confirm each:

• No pending tool calls. All Bash / file / tool operations returned.
• No background processes. run_in_background tasks, builds, spawned subprocesses have completed OR the user has explicitly accepted they continue after handoff.
• No unsaved state. Edits / commits / writes are actually on disk.
• No pending user questions. If the old session owes a reply, answer it.

If any item is incomplete, finish or defer explicitly. Surface status: "All pending work done — ready to hand off?"

Step 5: Output & Dispatch

Always do both of these — never skip either:

1. Output the Starting Prompt section directly in chat — PRIMARY artifact. User pastes it verbatim as the first message of a new session.
2. Save the full handoff document to the memory path above. The auto- memory system will load it at next session start.

Manual mode (/handoff default)

After Step 5.1 + 5.2, stop. Tell the user the old session stays alive; they can copy the prompt to a new session manually or continue working in this one. Do NOT spawn any new process.

Optional: offer to launch if the user later says so (Step 6).

Auto mode (/handoff auto)

After Step 5.1 + 5.2, and Pre-Termination Checklist passed:

Required launch pattern — use a SHORT reference prompt, never inline the full handoff content into the command line. Inlining multi-line/multi-KB content into wt/tmux/shell commands causes catastrophic failures on Windows (multi-line expansion breaks argument parsing → error 0x80070002, multiple ghost terminal windows; see feedback_handoff_short_prompt_only.md — S3-side-multi-lane 2026-04-26 forensic record).

The SHORT_PROMPT directs the new session to Read the handoff doc explicitly as its first action. A SessionStart hook (e.g. the claude-handoff plugin's hooks/session-start.py) MAY additionally inject the doc as additionalContext, but the prompt MUST NOT assume that injection happened — plugin install scope may not cover the new session's cwd (Mercury #359 / claude-handoff #12 forensic record), the plugin may not be installed, or the runtime may have failed silently. The explicit Read directive guarantees handoff visibility regardless of hook state.

SHORT_PROMPT contract (Δ11 — Path C lane assertion):

The prompt MUST start with a [LANE=<name>] marker as its first whitespace-delimited token. The new session's startup checks (via scripts/lane-assertion.sh) verify three-way alignment between this marker, the cwd-encoded project state dir, and the current git branch prefix. If the marker is missing or any pair disagrees, the assertion fails fast and guides recovery — preventing the share-cwd routing-bleed failure mode (Issue #342, S13-side-multi-lane forensic record).

# Resolve the active lane:
#   - main lane handoff file    → lane=main
#   - lane-suffixed handoff file → lane=<suffix> (after first hyphen)
HANDOFF_BASENAME=$(basename "$HANDOFF_PATH" .md)
case "$HANDOFF_BASENAME" in
  session-handoff)             LANE_NAME="main" ;;
  session-handoff-*)           LANE_NAME="${HANDOFF_BASENAME#session-handoff-}" ;;
  *)                           echo "ERROR: unrecognised handoff filename: $HANDOFF_BASENAME" >&2; exit 1 ;;
esac

# Resolve the worktree path from LANES.md (Rule 5.1, Issue #342).
# This is the cwd that wt/tmux must launch the new session at — its
# encoding determines ~/.claude/projects/<encoded>/ project state dir.
LANES_FILE="${MERCURY_MEMORY_DIR:-${CLAUDE_CONFIG_DIR:-$HOME/.claude}/projects/D--Mercury-Mercury/memory}/LANES.md"
WORKTREE_PATH_RAW=$(awk -v lane="$LANE_NAME" '
BEGIN { in_section=0; in_fence=0 }
/^```/ { in_fence = !in_fence; next }
in_fence { next }
/^### `[^`]+`/ {
  match($0, /^### `[^`]+`/)
  hdr=substr($0, RSTART+5, RLENGTH-6)
  in_section=(hdr == lane) ? 1 : 0
  next
}
in_section && /\*\*Worktree path\*\*/ {
  s=$0
  i=index(s, "**Worktree path**"); s=substr(s, i+length("**Worktree path**"))
  if (substr(s, 1, 2) == " (") { e=index(s, ")"); if (e > 0) s=substr(s, e+1) }
  c=index(s, ":"); if (c == 0) next
  s=substr(s, c+1); sub(/^[[:space:]]+/, "", s)
  if (substr(s, 1, 1) == "`") {
    # Backtick-quoted (canonical) — preserves paths with spaces, but trims
    # trailing whitespace inside the quoted region to defang invisible typos.
    s=substr(s, 2); bt=index(s, "`")
    if (bt > 0) { out=substr(s, 1, bt-1); sub(/[[:space:]]+$/, "", out); if (out != "") print out }
  } else {
    sub(/[[:space:]]+$/, "", s); if (s != "") print s
  }
}
' "$LANES_FILE")
if [ -z "$WORKTREE_PATH_RAW" ]; then
  echo "ERROR: lane '$LANE_NAME' has no Worktree path field in $LANES_FILE" >&2
  echo "       Add it per feedback_lane_protocol.md Rule 5.1 before auto-handoff." >&2
  exit 1
fi
# Reject duplicate Worktree path bullets — first-wins would silently route
# to a stale value.
WORKTREE_COUNT=$(printf '%s\n' "$WORKTREE_PATH_RAW" | grep -c '^.')
if [ "$WORKTREE_COUNT" -gt 1 ]; then
  echo "ERROR: lane '$LANE_NAME' has $WORKTREE_COUNT Worktree path bullets in $LANES_FILE" >&2
  echo "       Edit the lane section to keep exactly one before auto-handoff." >&2
  exit 1
fi
WORKTREE_PATH="$WORKTREE_PATH_RAW"

SHORT_PROMPT="[LANE=${LANE_NAME}] Continue from session handoff. Read ${HANDOFF_PATH} as your first action."

<encoded_cwd> for the handoff doc path uses the same encode_project_path() logic referenced earlier (: \ / → -, strip leading -).

SHORT_PROMPT must remain free of wt/tmux metacharacters — ; (command separator), & (background), | (pipe), \ outside quotes, $() (command substitution). The [LANE=<name>] marker only contains [a-z0-9-]+ per Rule 2.1 + the literal [/]/= brackets, none of which are wt/tmux metacharacters. The lane name is read from LANES.md (which the protocol governs), so injection via crafted lane names is bounded by Rule 2.1 + Rule 6 (lane sections only edited by their owning lane).

Pre-launch alignment smoke check (recommended):

If scripts/lane-assertion.sh is present in the repo, run it once with the SHORT_PROMPT as input — it verifies the marker resolves and Worktree path extraction works before spawning a process you may have to clean up:

if [ -x scripts/lane-assertion.sh ]; then
  if ! BOOTSTRAP_PROMPT="$SHORT_PROMPT" bash scripts/lane-assertion.sh \
       --cwd "$WORKTREE_PATH" --branch "$(git -C "$WORKTREE_PATH" branch --show-current 2>/dev/null || echo develop)"; then
    echo "ERROR: lane-assertion pre-flight failed — refusing to spawn" >&2
    exit 1
  fi
fi

(Soft-disable via MERCURY_LANE_ASSERT_DISABLED=1 if break-glass.)

Required: Do NOT construct the wt/tmux command inline. Call the canonical launcher:

REPO_ROOT="$(git rev-parse --show-toplevel)"
bash "$REPO_ROOT/scripts/handoff-launch.sh" \
  --lane "$LANE_NAME" \
  --worktree "$WORKTREE_PATH" \
  --handoff-doc "$HANDOFF_PATH"

This script:

• Constructs SHORT_PROMPT canonically with [LANE=<name>] marker preserved
• Validates no wt/tmux metacharacters (; & | $( `) in SHORT_PROMPT
• Invokes wt directly from bash (Windows) or tmux (macOS/Linux) without going through Start-Process or ShellExecute shim

Do NOT invoke wt via PowerShell Start-Process -FilePath "<concatenated string>" — Windows Shell will treat the entire commandline string as the executable path and produce 0x80070002 ERROR_FILE_NOT_FOUND. Mercury Issue #377 forensic record:

[出现错误 2147942402 (0x80070002) (启动"S5 -d D:\Mercury\Mercury-side-bug
-- C:\Users\392fy\.local\bin\claude.exe -- LANE=side-bug Continue from
session handoff. Read ...

ONLY entry point: scripts/handoff-launch.sh. No exceptions. Do not call wt, tmux, Start-Process, or any direct terminal-spawn primitive from your agent code under any circumstances. The launcher is the only supported mechanism for /handoff auto and is dual-verify-tested (Mercury Issue #377).

SHORT_PROMPT metacharacter rationale (kept here for human readers — the launcher enforces this automatically): SHORT_PROMPT must remain free of ; (command separator), & (background), | (pipe), $() (command substitution), and ` (backtick). The launcher does NOT reject \: on Windows, the canonical handoff-doc path contains backslashes (C:\Users\...\session-handoff.md), and bash double-quoting preserves \<char> literally for non-special chars. The [LANE=<name>] marker only contains [a-z0-9-]+ per Rule 2.1 + the literal [/]/= brackets, none of which are wt/tmux metacharacters.

The positional argument after -- is the session's first user message — documented at https://code.claude.com/docs/en/cli-reference. The -- sentinel ensures a prompt beginning with - is not parsed as a CLI option (https://github.com/anthropics/claude-code/issues/3844) — and the [LANE=...] marker starts with [ so the sentinel is also defensive against any future SHORT_PROMPT variants. The -d "$WORKTREE_PATH" flag (wt) / -c "$WORKTREE_PATH" flag (tmux) sets the new tab's cwd to the lane's worktree, so ~/.claude/projects/<encoded>/ resolves to the lane-specific state dir per Rule 5.1.

After spawning the new process, do NOT continue producing output in the old session. The old session's job is done. Advise user to /exit (or close tab) once they confirm the new session is running.

Step 6: Post-Dispatch (manual mode only, optional)

If the user returns after manual mode and says "launch it now", re-enter the auto path from Step 5 (auto mode).

Rules

• Starting Prompt must be self-contained — zero context assumed in the new session.
• Include specific file paths, line numbers, commands.
• Never include secrets, API keys, credentials.
• The chat-output prompt is the PRIMARY deliverable — never skip it.
• Do NOT add automatic hooks for SessionEnd or PreCompact — handoff is explicit only.
• Mode-scoped termination: auto mode treats handoff as a terminal event for the old session (spawn new → /exit old). Manual mode does NOT terminate; the user decides. Never apply auto-mode termination to a manual invocation.
• Before terminating (auto mode) verify all pending work has completed. Nothing carries over automatically.
• Manual mode MUST NOT spawn processes. Only the auto token (as the first whitespace-delimited argument to /handoff) triggers the claude CLI launch.
• The legacy $AGENTKB_DIR/scripts/handoff-orchestrator.py path is DEPRECATED. Do not invoke it. The claude-handoff plugin is the canonical session-continuity module (https://github.com/392fyc/claude-handoff).
• Δ10/Δ11 (Issue #345) — auto-mode SHORT_PROMPT MUST start with [LANE=<name>] marker, and wt -d / tmux -c MUST be set to the lane's Worktree path field from LANES.md (Rule 5.1). The new session's scripts/lane-assertion.sh validates three-way alignment (marker × cwd-encoded × branch prefix) at startup. Soft-disable via MERCURY_LANE_ASSERT_DISABLED=1. See .mercury/docs/guides/lane-naming.md §Lane workspace isolation Δ10/Δ11 sub-sections for the full contract.