ST then OSC 99 ; i=ID : p=body : d=1 ; <body> ST builds a multi-part notification keyed by identifier i.", "required": false, "byte_sequence_ST": "\u001b]99;i=1:p=title;Build\u001b\\", "byte_sequence_ST_readable": "ESC ] 9 9 ; i = 1 : p = t i t l e ; B u i l d ESC \\ == \\x1b]99;i=1:p=title;Build\\x1b\\\\ (title chunk; send body with d=1 to finish)", "byte_sequence_BEL": "\u001b]99;i=1:p=title;Build\u0007", "byte_sequence_BEL_readable": "ESC ] 9 9 ; i = 1 : p = t i t l e ; B u i l d BEL", "subparams": [] } ], "gotchas": [ "The metadata is colon-separated key=value pairs BEFORE the ';' that introduces the payload; getting the ';' vs ':' separators wrong breaks parsing.", "Long or binary payloads should be base64-encoded with e=1; multi-chunk notifications share the same i= identifier and end with d=1.", "OSC 99 is far richer than OSC 9 (titles, bodies, actions, icons) but only kitty (and a small set of compatible terminals) implement it — feature-detect.", "Notifications can be suppressed by the OS/notification daemon; a successful escape does not guarantee a visible popup.", "Over tmux/ssh the sequence needs passthrough." ], "v1_smoke_test": { "asserts": "OSC 99 simple and titled (multi-chunk) forms render as byte-exact OSC strings with kitty's key=value metadata grammar.", "behavioral_conformance": "deferred to v2." } }, "updated": "2026-05-29T00:00:00Z" }

{ "id": "terminal-osc/99", "family": "terminal-osc", "slug": "99", "title": "OSC 99 — Desktop notifications (kitty protocol)", "summary": "OSC 99 is kitty's structured desktop-notification protocol: OSC 99 ; metadata ; payload ST, where metadata is a list of key=value pairs (i= identifier, d= done flag, p= payload type such as title/body, e= base64-encoded) and payload is the (optionally base64) text. It supports multi-chunk notifications, titles+bodies, actions, and icons — far richer than OSC 9.", "kind": "control-sequence", "aliases": [ "OSC 99", "ESC ] 99", "kitty notifications", "desktop notification" ], "status": "de-facto", "verification": "verified", "tier": "C", "source_url": "https://sw.kovidgoyal.net/kitty/desktop-notifications/", "source_version": "kitty desktop-notifications protocol documentation, retrieved 2026-05-29", "retrieved_date": "2026-05-29", "attribution": [ { "claim_ref": "#summary", "source_url": "https://sw.kovidgoyal.net/kitty/desktop-notifications/", "source_version": "kitty docs, retrieved 2026-05-29", "note": "kitty: OSC 99 ; ; ST. Metadata keys include i (id), d (done), p (payload type: title/body/...), e (base64 encoding flag), a (actions). Allows multi-chunk title+body notifications." }, { "claim_ref": "#adoption", "source_url": "https://github.com/kovidgoyal/kitty/blob/master/docs/desktop-notifications.rst", "source_version": "kitty desktop-notifications.rst (protocol spec), retrieved 2026-05-29", "note": "The protocol spec source documents the escape-code grammar and the encoding/chunking rules; published for other terminals to implement." } ], "see_also": [ "terminal-osc/9", "terminal-osc/777" ], "ext_type": "terminal-escape@1", "ext": { "csi_or_osc": "OSC", "command_number": 99, "frame": { "introducer_7bit": "\u001b]", "introducer_7bit_readable": "ESC ] (0x1B 0x5D)", "introducer_8bit": "", "introducer_8bit_readable": "0x9D (single-byte OSC, 8-bit C1)", "note": "OSC frame (ECMA-48). Command number 99 is kitty's notification protocol; metadata 'key=value' pairs precede a ';' and the payload." }, "terminator": "ST|BEL", "terminator_detail": { "canonical_ST_7bit": "\u001b\\", "canonical_ST_7bit_readable": "ESC \\ (0x1B 0x5C)", "canonical_ST_8bit": "", "canonical_ST_8bit_readable": "0x9C (single-byte ST, 8-bit C1)", "alt_BEL": "\u0007", "alt_BEL_readable": "BEL (0x07)", "note": "ECMA-48 mandates ST; xterm and most modern terminals also accept BEL. Emit ST, accept both." }, "params": [ { "id": "simple", "anchor": "#simple", "name": "Simple notification", "meaning": "OSC 99 ; ; ST shows a notification with the given body text (empty metadata = single-chunk, plain).", "required": true, "byte_sequence_ST": "\u001b]99;;Hello\u001b\\", "byte_sequence_ST_readable": "ESC ] 9 9 ; ; H e l l o ESC \\ == \\x1b]99;;Hello\\x1b\\\\ (simple notification)", "byte_sequence_BEL": "\u001b]99;;Hello\u0007", "byte_sequence_BEL_readable": "ESC ] 9 9 ; ; H e l l o BEL", "subparams": [] }, { "id": "titled", "anchor": "#titled", "name": "Title + body", "meaning": "OSC 99 ; i=ID : p=title ; ST then OSC 99 ; i=ID : p=body : d=1 ; <body> ST builds a multi-part notification keyed by identifier i.", "required": false, "byte_sequence_ST": "\u001b]99;i=1:p=title;Build\u001b\\", "byte_sequence_ST_readable": "ESC ] 9 9 ; i = 1 : p = t i t l e ; B u i l d ESC \\ == \\x1b]99;i=1:p=title;Build\\x1b\\\\ (title chunk; send body with d=1 to finish)", "byte_sequence_BEL": "\u001b]99;i=1:p=title;Build\u0007", "byte_sequence_BEL_readable": "ESC ] 9 9 ; i = 1 : p = t i t l e ; B u i l d BEL", "subparams": [] } ], "gotchas": [ "The metadata is colon-separated key=value pairs BEFORE the ';' that introduces the payload; getting the ';' vs ':' separators wrong breaks parsing.", "Long or binary payloads should be base64-encoded with e=1; multi-chunk notifications share the same i= identifier and end with d=1.", "OSC 99 is far richer than OSC 9 (titles, bodies, actions, icons) but only kitty (and a small set of compatible terminals) implement it — feature-detect.", "Notifications can be suppressed by the OS/notification daemon; a successful escape does not guarantee a visible popup.", "Over tmux/ssh the sequence needs passthrough." ], "v1_smoke_test": { "asserts": "OSC 99 simple and titled (multi-chunk) forms render as byte-exact OSC strings with kitty's key=value metadata grammar.", "behavioral_conformance": "deferred to v2." } }, "updated": "2026-05-29T00:00:00Z" }