AgentHub/docs/HOOKS.md

Hook System Integration Guide

Comprehensive guide to integrating with Claude Code's hook system for real-time agent monitoring.

---

Table of Contents

• Overview
• Hook Architecture
• Hook Installation
• Hook Types
• Hook Handler Implementation
• Event Processing
• Error Handling
• Performance Considerations
• Testing Hooks
• Troubleshooting

---

Overview

Claude Code provides a hook system that allows external tools to receive real-time events during agent execution. Agent Dashboard uses these hooks to capture session lifecycle, tool executions, and notifications.

Privacy (Settings → Database → Privacy, server/lib/privacy.js): a hook whose cwd is an ignored folder (AGENTHUB_IGNORE_CWD, or under one — path-boundary match) is answered {ok: true, ignored: true} and nothing is stored; with Redact secrets on (AGENTHUB_REDACT_SECRETS=1) the stored events.data and events.summary have API keys, tokens, bearer headers, private keys and password=-style values replaced by [redacted] (trim_event_data / redact_text in server/db.js). The hook route still reads the raw payload in memory, and the transcript on disk is untouched. Hooks from another machine can be pushed to POST /api/hooks/ingest-batch with a token (see API.md → Push ingest).

Cursor (informational): Live hooks fire from Claude Code. Cursor sessions that only exist as JSONL under ~/.claude (Cursor uses the same paths locally) are still counted — they appear via startup import, continuous project sync, or remote SSH sync, not via hooks.

graph TB
    subgraph "Claude Code Process"
        CLI[Claude CLI]
        Agent[Agent Execution]
        Hooks[Hook System]
    end
    
    subgraph "Hook Wiring (~/.claude/settings.json)"
        SessionStart[SessionStart]
        UserPromptSubmit[UserPromptSubmit]
        PreTool[PreToolUse]
        PostTool[PostToolUse]
        Stop[Stop]
        SubagentStop[SubagentStop]
        Notification[Notification]
        SessionEnd[SessionEnd]
    end

    subgraph "Hook Handler"
        Handler[hook-handler.js]
    end

    subgraph "Dashboard Server"
        API[Express Server<br/>:4820]
    end

    Agent --> Hooks
    Hooks -->|stdin JSON| SessionStart
    Hooks -->|stdin JSON| UserPromptSubmit
    Hooks -->|stdin JSON| PreTool
    Hooks -->|stdin JSON| PostTool
    Hooks -->|stdin JSON| Stop
    Hooks -->|stdin JSON| SubagentStop
    Hooks -->|stdin JSON| Notification
    Hooks -->|stdin JSON| SessionEnd

    SessionStart -->|exec| Handler
    UserPromptSubmit -->|exec| Handler
    PreTool -->|exec| Handler
    PostTool -->|exec| Handler
    Stop -->|exec| Handler
    SubagentStop -->|exec| Handler
    Notification -->|exec| Handler
    SessionEnd -->|exec| Handler
    
    Handler -->|HTTP POST| API
    
    style Hooks fill:#F59E0B
    style Handler fill:#10B981
    style API fill:#3B82F6

---

Hook Architecture

Hook Execution Flow

sequenceDiagram
    participant Claude as Claude Code
    participant Handler as hook-handler.js
    participant Server as Dashboard Server
    participant DB as SQLite
    participant WS as WebSocket

    Claude->>Handler: node hook-handler.js <HookType> (stdin: JSON)
    Handler->>Handler: Wrap stdin as {hook_type, data}
    Handler->>Server: HTTP POST /api/hooks/event (one per dashboard database)
    Handler-->>Claude: exit 0 once the body is sent (never waits for the reply)
    Server->>DB: Insert/Update (one transaction)
    Server->>WS: Broadcast session_updated / agent_updated / new_event …

    Note over Claude: Continues as soon as<br/>the handler exits

Security: the hook handler POSTs to the loopback dashboard (127.0.0.1:<port>). The /api/hooks ingestion path is exempt from the optional DASHBOARD_TOKEN gate — it is a local-only write — so hooks keep working without a token even when one is configured for the rest of the API (GHSA-gr74-4xfh-6jw9).

Hook System Characteristics

Design Principles:

graph TB
    subgraph "Hook System Goals"
        NonBlocking[Non-Blocking<br/>Never block Claude Code]
        FailSafe[Fail-Safe<br/>Errors don't stop execution]
        FastExec[Fast Execution<br/>&lt; 100ms per hook]
        Complete[Complete Data<br/>Capture all events]
    end
    
    subgraph "Implementation"
        Timeout[2 s request timeout<br/>2.5 s hard exit]
        ErrorLog[Always exit 0<br/>errors are dropped]
        Async[Fire-and-forget POST<br/>no wait for the reply]
        JSON[JSON Serialization]
    end
    
    NonBlocking --> Timeout
    FailSafe --> ErrorLog
    FastExec --> Async
    Complete --> JSON
    
    style NonBlocking fill:#10B981
    style FailSafe fill:#10B981
    style FastExec fill:#10B981

---

Hook Installation

Installation Script

# Install hooks
npm run install-hooks

Important

Skip this entirely when the agenthub plugin is installed. The plugin declares the same eight hooks itself (inline in .claude-plugin/plugin.json, each running ${CLAUDE_PLUGIN_ROOT}/scripts/hook-handler.js). Running both means every event is POSTed twice. Events carry no id, so ingest can only drop a POST whose payload is byte-identical to the session's LATEST event from the last 10 seconds (findRecentDuplicateEvent, since v1.8.1) — that stops the doubled feed rows, token/cost figures and subagent cards, but the second hook process still runs on every event, so remove the duplicate registration anyway. scripts/plugin-bootstrap.js removes checkout-installed entries on session start (backup: ~/.claude/settings.json.agenthub-bak) — and since v1.6.17 a settings file that still carries them also blocks the bootstrap's fast path (hasLegacyHooks), because the strip runs only in the full pass and a healthy install skipped it every session, keeping the duplicates alive indefinitely. And install-hooks.js itself — run by hand or by every checkout server start (npm run dev, npm start) — adds nothing while settings.json enables agenthub@… and removes every hook-handler.js entry it finds instead (same backup); it used to put them straight back after each strip, so a dev server beside the plugin kept ~40% of events doubled. Settings reports such hooks as installed (source: "plugin"). /agenthub-doctor reports any duplicates that remain. See PLUGINS.md.

Important

Hooks are a host-side step. Claude Code runs on your host, so the hook command must reference a hook-handler.js path that exists on the host. Run npm run install-hooks on the host — never inside a container. When run inside Docker/Podman, the installer refuses and exits non-zero (issue #193): a container-internal path written into a bind-mounted ~/.claude would break every host hook with MODULE_NOT_FOUND. The host handler POSTs to http://localhost:4820, which a containerized dashboard already publishes. (Escape hatch for running Claude Code inside the same container: AGENTHUB_ALLOW_CONTAINER_HOOKS=1 npm run install-hooks.)

For each of the eight hook types it adds one entry to ~/.claude/settings.json that runs the handler with the type as its argument; the five tool/turn hooks (PreToolUse, PostToolUse, Stop, SubagentStop, Notification) carry "matcher": "*". PreToolUse and PostToolUse also carry "async": true (ASYNC_HOOKS in scripts/install-hooks.js, and the same in .claude-plugin/plugin.json): they fire around every tool call, and Claude Code waits for a synchronous hook before going on — each a Node start of 0.1–0.2 s, so ~0.4 s added to every tool call. The handler only reports (it prints nothing and decides nothing), so nothing is lost by not waiting; the rarer hooks stay synchronous so a turn's start and end reach the dashboard in order. Entries that are not AgentHub's are left alone. There is nothing else to install — Claude Code runs scripts/hook-handler.js directly.

{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "*",
        "hooks": [
          { "type": "command", "command": "node \"/path/to/agenthub/scripts/hook-handler.js\" PreToolUse", "async": true }
        ]
      }
    ],
    "SessionStart": [
      {
        "hooks": [
          { "type": "command", "command": "node \"/path/to/agenthub/scripts/hook-handler.js\" SessionStart" }
        ]
      }
    ]
  }
}

Verification

# One line per hook type with an AgentHub entry in settings.json
# (with the plugin installed the hooks live in its plugin.json, so this prints nothing)
grep -o 'hook-handler.js[^ ]* [A-Za-z]*' ~/.claude/settings.json

The Settings page reports the same (source: "plugin" when the plugin supplies them), and /agenthub-doctor reports missing or duplicated entries.

---

Hook Types

1. SessionStart

Triggered when a Claude Code session starts. The source field distinguishes the trigger: startup (fresh launch), resume (--resume/--continue), clear (/clear), and fork, and compact — which fires mid-turn when auto-compaction kicks in while Claude is actively working, not at a fresh prompt.

Payload Example:

{
  "session_id": "8d1f0c2e-5b7a-4c3e-9f10-2a6b7c8d9e01",
  "transcript_path": "/home/you/.claude/projects/-home-you-repo/8d1f0c2e-5b7a-4c3e-9f10-2a6b7c8d9e01.jsonl",
  "cwd": "/home/you/repo",
  "hook_event_name": "SessionStart",
  "source": "startup",
  "model": "claude-opus-5-5"
}

Purpose:

• Create the session and main-agent records on first contact
• Stamp awaiting_input_since (with awaiting_reason = session_start) so the dashboard shows the row in Waiting from the moment the CLI lands at a prompt — only for startup/resume/clear. A compact-source SessionStart fires mid-turn while Claude is working, so it leaves the awaiting flag untouched: a genuinely-active session stays Active (not flipped to Waiting), and a session that compacted while idle keeps its existing Waiting flag and reason
• Reactivate completed/abandoned sessions on resume
• Sweep other active sessions whose last activity is older than DASHBOARD_STALE_MINUTES (default 180), marking them abandoned with their agents completed (Remote Data Source sessions, source ≠ local, are exempt — their status comes from the SSH-mirror reconciliation, not local activity)

---

2. UserPromptSubmit

Triggered the moment the user hits enter on a prompt — fires before Claude does any work.

Payload Example:

{
  "session_id": "8d1f0c2e-5b7a-4c3e-9f10-2a6b7c8d9e01",
  "transcript_path": "/home/you/.claude/projects/-home-you-repo/8d1f0c2e-5b7a-4c3e-9f10-2a6b7c8d9e01.jsonl",
  "cwd": "/home/you/repo",
  "permission_mode": "default",
  "hook_event_name": "UserPromptSubmit",
  "prompt": "Refactor this function..."
}

Purpose:

• Clear awaiting_input_since (and awaiting_reason — both reset to NULL together) on the session and main agent
• Promote the main agent to working so the dashboard reflects "Claude is now thinking on this" through the entire response — including text-only replies that emit no PreToolUse before Stop

---

3. PreToolUse

Triggered before a tool executes.

Payload Example:

{
  "session_id": "8d1f0c2e-5b7a-4c3e-9f10-2a6b7c8d9e01",
  "transcript_path": "/home/you/.claude/projects/-home-you-repo/8d1f0c2e-5b7a-4c3e-9f10-2a6b7c8d9e01.jsonl",
  "cwd": "/home/you/repo",
  "permission_mode": "default",
  "hook_event_name": "PreToolUse",
  "tool_name": "Bash",
  "tool_input": { "command": "npm test", "description": "Run the tests" },
  "tool_use_id": "toolu_01AbCdEfGhIjKlMnOpQrStUv"
}

A tool call made inside a subagent also carries agent_id and agent_type.

Purpose:

• Clear awaiting_input_since (and awaiting_reason — both reset to NULL together; Claude can only call a tool after fresh user input)
• Set agent to working, set current_tool
• Track tool execution start time
• If tool name is Agent, create a subagent record

---

4. PostToolUse

Triggered after a tool completes execution.

Payload Example:

{
  "session_id": "8d1f0c2e-5b7a-4c3e-9f10-2a6b7c8d9e01",
  "transcript_path": "/home/you/.claude/projects/-home-you-repo/8d1f0c2e-5b7a-4c3e-9f10-2a6b7c8d9e01.jsonl",
  "cwd": "/home/you/repo",
  "permission_mode": "default",
  "hook_event_name": "PostToolUse",
  "tool_name": "Bash",
  "tool_input": { "command": "npm test", "description": "Run the tests" },
  "tool_response": { "stdout": "…", "stderr": "", "interrupted": false },
  "tool_use_id": "toolu_01AbCdEfGhIjKlMnOpQrStUv",
  "duration_ms": 1234
}

The payload carries no token counts: tokens are read from the transcript (see Transcript-derived sync).

Purpose:

• Clear awaiting_input_since (and awaiting_reason — both reset to NULL together; covers permission-prompt approval mid-tool)
• Clear current_tool on agent (agent stays working)
• Sync the session's tokens from its transcript, like every event that carries a transcript_path

Token and cost flow: no cost is stored. Tokens land in token_usage, one row per session and model bucket, and cost is computed when it is read (calculateCost, e.g. GET /api/pricing/cost) from those rows and the editable model_pricing table.

graph TB
    Hook[Any hook with transcript_path] --> Cache[TranscriptCache<br/>reads only the new bytes]
    Cache --> Usage[token_usage<br/>per session + model bucket]
    Usage --> Read[Cost computed on read<br/>token_usage × model_pricing]

    style Usage fill:#10B981
    style Read fill:#3B82F6

---

5. Stop

Triggered when Claude finishes a turn (NOT when the session is closed).

Payload Example:

{
  "session_id": "8d1f0c2e-5b7a-4c3e-9f10-2a6b7c8d9e01",
  "transcript_path": "/home/you/.claude/projects/-home-you-repo/8d1f0c2e-5b7a-4c3e-9f10-2a6b7c8d9e01.jsonl",
  "cwd": "/home/you/repo",
  "permission_mode": "default",
  "hook_event_name": "Stop",
  "stop_hook_active": false,
  "last_assistant_message": "Done — the tests pass."
}

Purpose:

• Non-error: set main agent to idle and stamp awaiting_input_since (with awaiting_reason = stop) — Claude finished its turn, ball is in the user's court. The session shows as Waiting until UserPromptSubmit / PreToolUse fires
• Error (stop_reason="error"): drop awaiting_input_since (and awaiting_reason, cleared to NULL together), mark the session error
• Background subagents continue running — they complete individually via SubagentStop, never via Stop

Note: Stop does not fire when the user cancels a turn with Esc — interrupts emit no hook at all. The dashboard instead recovers cancelled turns from the transcript (see User interrupts (Esc)).

---

6. SubagentStop

Triggered when a sub-agent (explore, task, etc.) completes.

Payload Example:

{
  "session_id": "8d1f0c2e-5b7a-4c3e-9f10-2a6b7c8d9e01",
  "transcript_path": "/home/you/.claude/projects/-home-you-repo/8d1f0c2e-5b7a-4c3e-9f10-2a6b7c8d9e01.jsonl",
  "cwd": "/home/you/repo",
  "permission_mode": "default",
  "hook_event_name": "SubagentStop",
  "agent_id": "a73b0d3904535a49c",
  "agent_type": "Explore",
  "agent_transcript_path": "/home/you/.claude/projects/-home-you-repo/8d1f0c2e-5b7a-4c3e-9f10-2a6b7c8d9e01/subagents/agent-a73b0d3904535a49c.jsonl",
  "stop_hook_active": false,
  "last_assistant_message": "Found 3 call sites…"
}

Purpose:

• Match the finishing subagent by description, type, or task and mark it completed
• Deliberately does NOT clear awaiting_input_since (nor awaiting_reason) — a backgrounded subagent finishing tells us nothing about whether the human has responded
• Triggers a fire-and-forget JSONL scan (scanAndImportSubagents from scripts/import-history.js) after res.json() returns. The scan walks the session's subagents/agent-*.jsonl files, pairs each assistant tool_use block with the next matching user tool_result block by tool_use_id, and emits per-tool PreToolUse + PostToolUse events under the subagent's own agent_id. Idempotent (data LIKE '%"tool_use_id":"X"%' dedup) and merges into a hook-created live row when one matches by subagent_type + started_at within 30 s — closes the gap where subagent-internal tool calls would otherwise be invisible to the dashboard
• Attributes per-subagent tokens to each subagent's OWN model (issue #185). Each subagent transcript carries its own msg.usage under its own msg.model; the scan writes those token buckets to token_usage keyed by the real model (e.g. a Haiku QA agent under an Opus orchestrator) so cost is no longer priced at the orchestrator's rate. The subagent's resolved model is also stamped onto its agent row (metadata.model). Buckets whose model equals the parent session's model are deliberately skipped here — that bucket is owned by the main-transcript writer, and double-writing it would trip replaceTokenUsage's compaction baseline-shift; same-model subagents are reconciled by the authoritative importSession / reconcileTokens path instead
• Rebuilds the nested-subagent hierarchy (reconcileSubagentParents). Subagent rows are inserted flat under the main agent because no single hook event or JSONL file carries the spawner's identity. Each subagent transcript, however, records every child it spawned via the Task tool as toolUseResult.agentId (surfaced by parseSubagentFile as spawnedChildren). The scan inverts these into a child→parent map and repoints parent_agent_id (via setAgentParent) so a subagent that spawns its own subagents nests under its true spawner instead of collapsing to a single level under main; any subagent no other subagent claims stays under main. Idempotent and additive (only rewrites parent_agent_id, never inserts/deletes), it also corrects the live PreToolUse-Agent parent heuristic's guesses once transcripts land. scanAndImportSubagents returns reparented alongside created; the SubagentStop refetch nudge fires when either is non-zero so a pure re-parent still refreshes the tree
• Imported tool events carry imported: true, source: "subagent_jsonl" in their JSON data payload so analytics can distinguish backfilled rows from live hook-captured ones if needed

---

7. Notification

Triggered when Claude Code sends a system notification.

Payload Example:

{
  "session_id": "8d1f0c2e-5b7a-4c3e-9f10-2a6b7c8d9e01",
  "transcript_path": "/home/you/.claude/projects/-home-you-repo/8d1f0c2e-5b7a-4c3e-9f10-2a6b7c8d9e01.jsonl",
  "cwd": "/home/you/repo",
  "hook_event_name": "Notification",
  "message": "Claude needs your permission to use Bash",
  "notification_type": "permission_prompt"
}

Other notification_type values seen: idle_prompt, agent_completed, auth_success.

Purpose:

• Log the event for the activity feed
• If the message matches a permission/input-prompt pattern (permission, waiting for input, needs your approval, awaiting your response, …), stamp awaiting_input_since (with awaiting_reason = notification) so the session lands in Waiting
• If the message matches a compaction pattern, tag as a Compaction event
• Trigger a browser notification when the user has notifications enabled — this event and Stop are the two "Claude is waiting for YOU" moments, so each has its own switch in Settings → Notifications (onAwaitingInput / onTurnComplete in client/src/lib/notifPrefs.ts) and both default to ON once notifications are enabled

---

8. SessionEnd

Triggered when a Claude Code session ends.

Payload Example:

{
  "session_id": "8d1f0c2e-5b7a-4c3e-9f10-2a6b7c8d9e01",
  "transcript_path": "/home/you/.claude/projects/-home-you-repo/8d1f0c2e-5b7a-4c3e-9f10-2a6b7c8d9e01.jsonl",
  "cwd": "/home/you/repo",
  "hook_event_name": "SessionEnd",
  "reason": "prompt_input_exit"
}

reason is one of prompt_input_exit, clear, resume, other.

Purpose:

• Drop awaiting_input_since (and awaiting_reason, cleared to NULL together) on the session and any agents that still have it
• Mark all agents and the session as completed — unless the session is in error AND that error is still unrecovered at the transcript tail (isErrorAtTail: the latest API error has no successful turn after it), in which case error is preserved. A transient error the CLI retried past (successful assistant turns after the last error) finalizes as completed instead of freezing in a stale error
• Evict the session's transcript from the shared transcript cache

Stale-error self-heal. Separately from SessionEnd, the 15 s watchdog now scans error sessions (not just active) and clears a session back to active when its transcript has progressed past the last API error (isErrorAtTail is false). Claude auto-retries transient API errors (e.g. "Connection closed mid-response") and keeps working, so an error followed by real turn activity has recovered — recovery previously required a live UserPromptSubmit/PreToolUse hook, leaving imported or sweep-monitored sessions pinned in error indefinitely.

---

Hook Handler Implementation

hook-handler.js Architecture

graph TB
    Args[argv: HookType + optional tool] --> Wrap
    Stdin[stdin JSON] --> Wrap[Envelope<br/>hook_type, data, tool?, run_id?]
    Wrap --> Ports[resolveHookIngestPorts<br/>one port per database]
    Ports --> P1[POST /api/hooks/event<br/>dashboard A]
    Ports --> P2[POST /api/hooks/event<br/>dashboard B]
    P1 --> Flushed[Request body sent]
    P2 --> Flushed
    Flushed --> Exit[exit 0]
    Guard[2.5 s safety timer] --> Exit

    style Exit fill:#10B981

What it does

scripts/hook-handler.js (about 120 lines) is the whole forwarder:

• Envelope. It POSTs {hook_type, data, tool?, run_id?} to /api/hooks/event. hook_type is its first argument; data is the parsed stdin, or {raw: "<stdin>"} when stdin is not JSON. tool is codex or antigravity when those tools' own hook scripts pass it as the second argument (Claude Code passes none). run_id is AGENTHUB_RUN_ID, set in every pane the dashboard starts.
• Fire-and-forget. It exits once the request body is sent, without waiting for the dashboard's reply, so a busy or wedged dashboard never holds Claude Code at "running hooks".
• Never fails. A refused connection is skipped, a request that takes over 2 s is dropped, and a 2.5 s timer exits regardless. The exit code is always 0.

Port resolution & fan-out. The handler resolves its targets at runtime via server/lib/server-info.js:

1. If CLAUDE_DASHBOARD_PORT is set in the environment, the handler treats it as an explicit operator override and POSTs to that single port — no discovery, no fan-out (useful for tests and container setups).
2. Otherwise it reads ~/.claude/.agenthub.json, a JSON document that lists every dashboard server currently running on the machine. Each server appends its {port, pid, startedAt, dataDir} entry on startup and removes it on a clean shutdown. The handler prunes any entry whose PID is no longer alive and POSTs the hook payload to one port per unique SQLite data directory (lowest port wins when two instances share ~/.claude/agenthub). The other instance re-broadcasts the workspaces those hooks moved within DASHBOARD_LANE_SYNC_MS (2 s), so its browsers see a workspace's status without a refresh.
3. If neither yields a target, the handler falls back to 4820.

Dashboards with different databases (e.g. the packaged desktop app using its own Application Support data dir alongside npm run dev) still each receive hooks. Dashboards sharing one database never double-ingest events.

---

Event Processing

Server-Side Hook Processing

POST /api/hooks/event (server/routes/hooks.js, ingestHook):

1. Checks the body (400 when it is not a hook), maps a Codex or Antigravity payload onto Claude's shape, and answers {ok: true, ignored: true} for a hook from an ignored folder and {ok: true, duplicate: true} for the same event posted twice within 10 s.
2. Reads the transcript first (incremental TranscriptCache), so the write transaction never waits on a large file.
3. Runs processEvent — session and agent upserts, the status transitions described under Hook Types, the event row (redacted when Redact secrets is on) and the transcript-derived sync below — then binds the session to the workspace pane that ran it (run_id).
4. Broadcasts the changes over WebSocket: session_created, session_updated, agent_created, agent_updated, new_event, workflow_upserted.
5. After the reply, evaluates event-driven alert rules, and a SubagentStop starts the subagent JSONL scan.

Event Processing Pipeline

graph TB
    Hook[Hook Event] --> Validate[Validate Payload]
    Validate --> DB[Database Operations]
    DB --> Session[Update Session]
    DB --> Agent[Update Agent]
    DB --> Tool[Create Tool Record]
    
    Session --> Broadcast[Broadcast to WebSocket]
    Agent --> Broadcast
    Tool --> Broadcast
    
    Broadcast --> Client1[Client 1]
    Broadcast --> Client2[Client 2]
    Broadcast --> ClientN[Client N]
    
    style Validate fill:#3B82F6
    style DB fill:#003B57,color:#fff
    style Broadcast fill:#F59E0B

Transcript-derived sync

On every event that carries a transcript_path, the shared TranscriptCache re-reads the JSONL (incrementally) and the ingestor keeps three session fields in sync with what the user is actually doing in the CLI:

• Tokens / cost — usage is accumulated per model bucket (compaction-aware baselines).
• Model — the most recent assistant entry's model keeps sessions.model current after a /model switch.
• Name — the session title is read from the transcript: the custom-title line (/rename, claude -n, picker Ctrl+R) always wins, otherwise the auto-generated ai-title fills a placeholder/auto name (so a user-chosen name is never clobbered). When neither title exists, the session's first user prompt (tool-result, meta/caveat, and slash-command plumbing entries skipped; whitespace-collapsed, 60-char label) fills the placeholder session name plus the main agent's placeholder name and empty task — a later ai-title can still replace a descriptor-filled name, and the agent fill passes the in-flight current_tool through so it is never wiped mid-turn. sessions.name is updated via a no-op-guarded statement and a session_updated broadcast fires only on a real change, so the dashboard reflects renames in real time. The 15 s error-detection watchdog runs the same sync for active sessions left idle right after a /rename.

User interrupts (Esc) — no hook fires

Cancelling a turn with Esc fires no hook at all (a documented Claude Code limitation — there is no Stop, Notification, or other event on interrupt). Since UserPromptSubmit has already promoted the main agent to working, an un-handled cancel would leave the session stuck in working indefinitely. The dashboard recovers it from the transcript, via the same 15 s watchdog, two ways:

1. Marker path — when the cancel happens after some output, Claude Code appends a [Request interrupted by user] user entry (with an interruptedMessageId). TranscriptCache reports pendingInterrupt, computed from transcript ordering alone: the latest interrupt timestamp vs the latest real turn activity, both on Claude Code's clock. (It is not compared against the session's last hook event — those clocks differ, and for a sub-second cancel the UserPromptSubmit event is recorded after the transcript interrupt, the precise case that used to stay stuck.) The session moves to Waiting within ~15 s.
2. Idle-working timeout — when Esc is pressed before any output, Claude Code writes no marker; the only evidence is silence. When the main agent has been working with current_tool null and neither a hook event nor the transcript mtime has advanced for DASHBOARD_WORKING_IDLE_SECONDS (default 120), the turn is treated as dead. A streaming/long-output turn (transcript still growing) and an in-flight tool call are exempt by those guards; a rare false flip self-heals on the next real hook.

Both paths land the session in Waiting (main agent → waiting, awaiting_input_since stamped with awaiting_reason = interrupted — identical to a non-error Stop aside from the reason) and log an Interrupted event. A resume (new prompt in the transcript) clears pendingInterrupt and the fresh hook keeps the session non-stale.

Missed SessionEnd (dashboard down) — liveness reap

SessionEnd is the only signal that a session closed, and hooks are fire-and-forget: if the dashboard was not running when the user quit (Ctrl+C, terminal closed), the POST fails silently and the event is lost forever — the session previously sat in Waiting until the stale sweep (3 h by default). The same 15 s watchdog closes the gap with a process-liveness probe (server/lib/session-liveness.js): it enumerates running claude CLI processes and their working directories (ps + lsof on macOS, /proc/<pid>/cwd on Linux) and completes any active session whose cwd has no live claude process — the same terminal state a real SessionEnd produces, plus a synthetic SessionEnd event (data.source = "liveness-probe") on the timeline.

Fail-safe guards: the probe reports "no answer" (nothing changes) on Windows, inside containers (host processes are invisible), on ps/lsof failure, or when disabled via DASHBOARD_LIVENESS_PROBE=0 (the escape hatch for hooks arriving from another machine); the session must have a cwd, and that cwd must be POSIX-absolute — a household-hook-forwarded session reports the origin machine's own path (e.g. a Windows D:\Git\ai-deck) that this host's /proc/lsof scan can never produce, so the reap skips it rather than falsely completing every remote session (this makes a mixed local + forwarded deployment correct without the blanket DASHBOARD_LIVENESS_PROBE=0); Remote Data Source sessions (sessions.source ≠ local) are also skipped outright — their POSIX-absolute cwd lives on another machine reached over SSH, so this host's process probe proves nothing about them, and their status is reconciled from the SSH mirror by remote-sync.js (the same source = 'local' guard also exempts them from the watchdog's error/interrupt scan and both stale sweeps); and — on watchdog ticks only — its transcript must not have been written for at least DASHBOARD_LIVENESS_IDLE_SECONDS (default 60; the last hook write is the fallback clock when no transcript exists on disk) so a mid-turn / just-resumed session never flickers out. The reap runs immediately at startup (rows from a previous run), again ~5 s after startup (rows the startup sync just imported) — both startup passes skip the idle gate, so a session quit even seconds before launch clears at once — and on every 15 s watchdog tick (gated) as the safety net. A false completion self-heals — the next hook event reactivates the session.

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Error Handling

Error Handling Strategy

The handler has no error path that reaches Claude Code:

What goes wrong	What the handler does
stdin is not JSON	Forwards it as data: {raw: "<stdin>"}
No dashboard listening (ECONNREFUSED)	Skips that target
A dashboard does not take the request within 2 s	Drops it and moves on
Anything hangs	The 2.5 s safety timer exits
The dashboard rejects or fails the event	Not seen — the handler never reads the reply

It always exits 0, so Claude Code never shows a hook error and never waits on AgentHub. Events sent while no dashboard was running are not replayed; the transcript sync and the liveness reap bring the session up to date later.

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Performance Considerations

Hook Execution Time

Claude Code waits only for the handler process: Node start-up, reading stdin, sending the request. Measured on a 4-core desktop: 60–90 ms per hook, almost all of it Node start-up. The dashboard's work happens after the handler has exited — ingesting a hook took ~2 ms (p50) against a 1.25 GB database at 10 hooks/s, and stayed under 40 ms (p99) at 100 hooks/s with 10 browsers open.

What keeps it fast

• Fire-and-forget POST — no wait for the dashboard's reply.
• Incremental transcript reads — TranscriptCache reads only the bytes appended since the last hook.
• One POST per database, not per server — servers sharing a database get each event once (resolveHookIngestPorts).
• Heavy reads off the event loop — aggregates run in a worker (server/lib/read-pool.js), so a slow page never delays ingest.

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Testing Hooks

Manual Testing

Pipe a payload into the handler. It posts to every running dashboard, so use a session id you will recognise:

echo '{"session_id":"hook-test-001","cwd":"/tmp","hook_event_name":"SessionStart","source":"startup"}' \
  | node scripts/hook-handler.js SessionStart

echo '{"session_id":"hook-test-001","cwd":"/tmp","hook_event_name":"PreToolUse","tool_name":"Bash","tool_input":{"command":"ls"},"tool_use_id":"toolu_test_1"}' \
  | node scripts/hook-handler.js PreToolUse

The handler prints nothing. To see the dashboard's answer, POST the envelope yourself:

curl -s -X POST http://localhost:4820/api/hooks/event \
  -H 'Content-Type: application/json' \
  -d '{"hook_type":"Stop","data":{"session_id":"hook-test-001","cwd":"/tmp","hook_event_name":"Stop"}}'

Integration Testing

The server suite drives POST /api/hooks/event end to end — for example server/__tests__/api.test.js and server/__tests__/awaiting-subagent-guard.test.js; Codex and Antigravity hooks have codex-hook-route.test.js and antigravity-hook-route.test.js. Run them with npm run test:server, never a bare node --test from a workspace pane (some suites start and kill tmux sessions).

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Troubleshooting

Common Issues

Issue	Symptoms	Solution
Hooks not installed	No data in dashboard	grep hook-handler.js ~/.claude/settings.json (or check the plugin is enabled), then npm run install-hooks or /agenthub-doctor
Hooks installed twice	Every event doubled	Plugin and settings.json both carry them — see Installation Script
Dashboard not running	Hooks run, nothing arrives	agenthub start (or npm start from a checkout); events sent meanwhile are not replayed, the transcript sync fills the session in
Dashboard on another port	Nothing arrives	The handler finds servers through ~/.claude/.agenthub.json; set CLAUDE_DASHBOARD_PORT to force one
Hooks installed from a container	MODULE_NOT_FOUND in Claude Code	Install on the host — see the container note under Installation Script

Seeing what a hook sends

The handler logs nothing by design. POST the envelope yourself (see Manual Testing) and read the reply.

Health Check

# Check server is running
curl http://localhost:4820/api/health

# Expected: {"status":"ok","version":"…","timestamp":"…"}

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Summary

The hook system provides:

• ✅ Real-time event capture - Lifecycle, tools, notifications
• ✅ Non-blocking execution - Never delays Claude Code
• ✅ Fail-safe design - Errors don't stop execution
• ✅ Fast processing - < 100ms per hook
• ✅ Complete coverage - All agent lifecycle events
• ✅ Easy installation - One-command setup

For server-side processing, see server/README.md.