Imsg

imsg — iMessage CLI for agents

When to use

• Reading, searching, or summarizing iMessage conversations on this Mac.
• Sending a text or file attachment to a handle (phone/email) or chat GUID.
• Waiting for a reply (blocking watch --timeout or non-blocking poll loop).

When NOT to use

• Non-macOS systems (the CLI reads ~/Library/Messages/chat.db and drives Messages.app).
• Group MMS edge cases (RCS/MMS group behavior is not guaranteed).
• Anything requiring message deletion or editing — the db is opened read-only.

Agent rules

• Always pass --json. It is the stable machine contract: no ANSI, ISO dates, fixed field names. Never parse human output.
• Branch on exit codes:

• Disambiguate exit 2 via stdout: policy blocks emit {"error": "...", "blocked": true}; usage errors print a usage line to stderr.

Wait-for-reply loop (poll + cursor)

Bootstrap once (returns the current cursor, exit 3, no messages):

imsg poll --json
# => { "chat": null, "messages": [], "cursor": { "rowid": 48291, "ts": "..." } }

Then loop: sleep N seconds, poll from the saved cursor, scoped to the handle you are waiting on:

imsg poll +14085551234 --since-rowid 48291 --json

• Exit 0: new messages — process messages[], save the new cursor.rowid.
• Exit 3: nothing yet — keep waiting with the same cursor.
• The cursor never re-emits a message and never skips one; when --limit truncates, the cursor points at the last emitted message so the next call resumes exactly there.

Alternative single blocking wait:

imsg watch +14085551234 --timeout 300 --json

• Exit 0: stdout is one { chat, messages, cursor } object with the new messages.
• Exit 124: timed out; messages is empty, cursor is current.

Monitoring / waiting for messages

For agent harnesses that watch a background process's output rather than polling a script, use imsg stream — a long-running NDJSON event stream (one JSON object per stdout line, no ANSI, no human formatting):

imsg stream --from +14085551234 --max-events 1 --timeout 600

Run it as a background command and watch stdout for the "type":"message" line: in Claude Code, the Monitor tool watching the background shell's stdout; in other harnesses, tail the background process's output until a matching line appears or the process exits. Exits 0 once --max-events is hit, 124 on --timeout with no match, 2 if policy-blocked. See references/commands.md for the full event schema.

When the monitor is started shortly after a separate one-shot read, add a bounded replay window so the handoff cannot miss an intervening message:

imsg stream --chat-id 12 --from +17739974600 --lookback 2m

--lookback applies the same chat, sender, and text filters to historical and live rows. Historical message events add "replay": true; live event shape is unchanged. Do not use it to bypass allowlist blocks or Full Disk Access.

Send safety

• Confirm the recipient handle with the user before any real send.
• Optional advanced config at ~/.config/imsg/config.json can restrict imsg to an allowlist of handles/chats ({ "allowlist": [...], "confirmSend": true }); by default (no config file) everything is unrestricted. When a block does occur (exit 2, blocked: true), surface it to the user — do NOT retry or work around it.
• When confirmSend is enabled, sends require --yes.
• Use --dry-run to validate a send with zero side effects (works with text and files).
• Messages over 500 chars require --force in interactive human mode.

Attachments

Send a file (with or without text):

imsg send +14085551234 --file /absolute/path/pic.jpg --json
imsg send +14085551234 "see attached" --file ~/Desktop/doc.pdf --json

Incoming attachments appear in read/recent/poll/watch JSON as:

"attachments": [{ "filename": "~/Library/Messages/Attachments/...", "mimeType": "image/heic", "transferName": "IMG_0001.heic", "resolvedPath": "/Users/me/Library/Messages/Attachments/..." }]

resolvedPath is the absolute on-disk path (may be null if not downloaded).

Troubleshooting

Run imsg doctor --json first. Five checks: chat.db access, osascript, Messages.app, runtime, config.

• chat.db access failing = the terminal lacks Full Disk Access (System Settings > Privacy & Security > Full Disk Access, then restart the terminal).
• osascript failing or send errors = Automation permission for Messages.app not granted (System Settings > Privacy & Security > Automation).
• Env overrides: IMESSAGE_DB_PATH (alternate chat.db), IMSG_CONFIG_PATH (alternate safety config).

Full command/flag/exit-code and JSON-shape reference: references/commands.md. Copy-paste patterns for common use cases: references/recipes.md.