{
  "id": "terminal-osc/133",
  "family": "terminal-osc",
  "slug": "133",
  "title": "OSC 133 — Semantic Prompts (FinalTerm / FTCS shell integration)",
  "summary": "OSC 133 marks shell prompt, command-input, and command-output boundaries so terminals can navigate by command, fold output, and color the prompt by exit status. Four subcommands: A (prompt start), B (command-line start), C (output start), D[;exitcode] (command finished). Originated in the defunct FinalTerm emulator; harmonized by Per Bothner's Semantic Prompts proposal; near-universally adopted.",
  "kind": "control-sequence",
  "aliases": [
    "FTCS",
    "FinalTerm prompt markers",
    "FinalTerm sequences",
    "semantic prompts",
    "shell integration marks",
    "FTCS_PROMPT/FTCS_COMMAND_START/FTCS_COMMAND_EXECUTED/FTCS_COMMAND_FINISHED"
  ],
  "status": "de-facto",
  "verification": "verified",
  "tier": "C",
  "source_url": "https://gitlab.freedesktop.org/Per_Bothner/specifications/-/blob/master/proposals/semantic-prompts.md",
  "source_version": "semantic-prompts.md @ gitlab.freedesktop.org/Per_Bothner/specifications master (unversioned living document)",
  "retrieved_date": "2026-05-29",
  "attribution": [
    {
      "claim_ref": "#summary",
      "source_url": "https://gitlab.freedesktop.org/Per_Bothner/specifications/-/blob/master/proposals/semantic-prompts.md",
      "source_version": "master, retrieved 2026-05-29",
      "note": "Semantic Prompts proposal is the harmonizing cross-terminal spec; defines purpose of prompt/input/output marking."
    },
    {
      "claim_ref": "#A",
      "source_url": "https://learn.microsoft.com/en-us/windows/terminal/tutorials/shell-integration",
      "source_version": "retrieved 2026-05-29",
      "note": "OSC 133 ; A ST = FTCS_PROMPT, start of prompt. Stated identically by Windows Terminal docs and Contour."
    },
    {
      "claim_ref": "#A",
      "source_url": "https://contour-terminal.org/vt-extensions/osc-133-shell-integration/",
      "source_version": "retrieved 2026-05-29",
      "note": "Second independent source for A semantics (quorum)."
    },
    {
      "claim_ref": "#B",
      "source_url": "https://learn.microsoft.com/en-us/windows/terminal/tutorials/shell-integration",
      "source_version": "retrieved 2026-05-29",
      "note": "OSC 133 ; B ST = FTCS_COMMAND_START, start of command line / end of prompt."
    },
    {
      "claim_ref": "#B",
      "source_url": "https://contour-terminal.org/vt-extensions/osc-133-shell-integration/",
      "source_version": "retrieved 2026-05-29",
      "note": "Second independent source for B semantics (quorum)."
    },
    {
      "claim_ref": "#C",
      "source_url": "https://learn.microsoft.com/en-us/windows/terminal/tutorials/shell-integration",
      "source_version": "retrieved 2026-05-29",
      "note": "OSC 133 ; C ST = FTCS_COMMAND_EXECUTED, start of command output / end of command line."
    },
    {
      "claim_ref": "#C",
      "source_url": "https://contour-terminal.org/vt-extensions/osc-133-shell-integration/",
      "source_version": "retrieved 2026-05-29",
      "note": "Second independent source for C semantics (quorum)."
    },
    {
      "claim_ref": "#D",
      "source_url": "https://learn.microsoft.com/en-us/windows/terminal/tutorials/shell-integration",
      "source_version": "retrieved 2026-05-29",
      "note": "OSC 133 ; D [ ; exitcode ] ST = FTCS_COMMAND_FINISHED; 0 success, nonzero error; omitting exitcode leaves the mark default-colored."
    },
    {
      "claim_ref": "#D",
      "source_url": "https://contour-terminal.org/vt-extensions/osc-133-shell-integration/",
      "source_version": "retrieved 2026-05-29",
      "note": "Second independent source for D semantics including optional exit code (quorum)."
    },
    {
      "claim_ref": "#origin",
      "source_url": "https://iterm2.com/documentation-escape-codes.html",
      "source_version": "retrieved 2026-05-29",
      "note": "iTerm2 states the sequences were pioneered by the now-defunct FinalTerm emulator and documents them."
    },
    {
      "claim_ref": "ext.terminator",
      "source_url": "https://invisible-island.net/xterm/ctlseqs/ctlseqs.html",
      "source_version": "xterm patch #410, 2026/04/19",
      "note": "OSC frame is ESC ] ... terminated by ST (ESC \\\\); xterm convention also accepts BEL (0x07) as terminator."
    },
    {
      "claim_ref": "ext.frame",
      "source_url": "https://invisible-island.net/xterm/ctlseqs/ctlseqs.html",
      "source_version": "xterm patch #410, 2026/04/19",
      "note": "OSC = ESC ] (0x9D in 8-bit). ECMA-48 5th ed. 1991 defines the OSC frame and ST; command numbers are not registered anywhere."
    }
  ],
  "see_also": [
    "terminal-osc/633",
    "terminal-osc/0",
    "terminal-osc/7",
    "terminal-osc/8"
  ],
  "ext_type": "terminal-escape@1",
  "ext": {
    "csi_or_osc": "OSC",
    "command_number": 133,
    "frame": {
      "introducer_7bit": "\u001b]",
      "introducer_7bit_readable": "ESC ] (0x1B 0x5D)",
      "introducer_8bit": "",
      "introducer_8bit_readable": "0x9D (single-byte OSC, 8-bit C1)",
      "note": "Per ECMA-48 5th ed. 1991 / ISO 6429. Command numbers (the '133') have no registry; see terminfo.dev and xterm ctlseqs."
    },
    "terminator": "ST|BEL",
    "terminator_detail": {
      "canonical_ST_7bit": "\u001b\\",
      "canonical_ST_7bit_readable": "ESC \\ (0x1B 0x5C)",
      "canonical_ST_8bit": "œ",
      "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 virtually all modern terminals ALSO accept BEL on the parsing side. Emit ST for spec-correctness; accept both when parsing."
    },
    "params": [
      {
        "id": "A",
        "anchor": "#A",
        "name": "FTCS_PROMPT",
        "meaning": "Start of the prompt. Emitted by the shell precmd hook just before printing PS1.",
        "required": false,
        "byte_sequence_ST": "\u001b]133;A\u001b\\",
        "byte_sequence_ST_readable": "ESC ] 1 3 3 ; A ESC \\   ==  \\x1b]133;A\\x1b\\\\",
        "byte_sequence_BEL": "\u001b]133;A\u0007",
        "byte_sequence_BEL_readable": "ESC ] 1 3 3 ; A BEL   ==  \\x1b]133;A\\x07",
        "subparams": []
      },
      {
        "id": "B",
        "anchor": "#B",
        "name": "FTCS_COMMAND_START",
        "meaning": "Start of the command line / end of the prompt. Everything after this until C is what the user typed.",
        "required": false,
        "byte_sequence_ST": "\u001b]133;B\u001b\\",
        "byte_sequence_ST_readable": "ESC ] 1 3 3 ; B ESC \\   ==  \\x1b]133;B\\x1b\\\\",
        "byte_sequence_BEL": "\u001b]133;B\u0007",
        "byte_sequence_BEL_readable": "ESC ] 1 3 3 ; B BEL   ==  \\x1b]133;B\\x07",
        "subparams": []
      },
      {
        "id": "C",
        "anchor": "#C",
        "name": "FTCS_COMMAND_EXECUTED",
        "meaning": "Start of command output / end of the command line. Emitted from the shell preexec hook, just before the command runs.",
        "required": false,
        "byte_sequence_ST": "\u001b]133;C\u001b\\",
        "byte_sequence_ST_readable": "ESC ] 1 3 3 ; C ESC \\   ==  \\x1b]133;C\\x1b\\\\",
        "byte_sequence_BEL": "\u001b]133;C\u0007",
        "byte_sequence_BEL_readable": "ESC ] 1 3 3 ; C BEL   ==  \\x1b]133;C\\x07",
        "subparams": []
      },
      {
        "id": "D",
        "anchor": "#D",
        "name": "FTCS_COMMAND_FINISHED",
        "meaning": "End of the command. Optional exit code as a second parameter: 0 = success, nonzero = error. Omitting the exit code leaves the mark default-colored (no success/error tint).",
        "required": false,
        "byte_sequence_ST": "\u001b]133;D\u001b\\",
        "byte_sequence_ST_readable": "ESC ] 1 3 3 ; D ESC \\   ==  \\x1b]133;D\\x1b\\\\   (no exit code)",
        "byte_sequence_BEL": "\u001b]133;D\u0007",
        "byte_sequence_BEL_readable": "ESC ] 1 3 3 ; D BEL   ==  \\x1b]133;D\\x07   (no exit code)",
        "subparams": [
          {
            "id": "fact-d-exitcode",
            "anchor": "#fact-d-exitcode",
            "name": "ExitCode",
            "meaning": "Optional integer exit status of the finished command. 0 = success (often green mark), nonzero = error (often red mark). When absent, the terminal does not tint the mark.",
            "required": false,
            "example_byte_sequence_ST": "\u001b]133;D;0\u001b\\",
            "example_byte_sequence_ST_readable": "ESC ] 1 3 3 ; D ; 0 ESC \\   ==  \\x1b]133;D;0\\x1b\\\\   (success)",
            "example_byte_sequence_nonzero_ST": "\u001b]133;D;1\u001b\\",
            "example_byte_sequence_nonzero_ST_readable": "ESC ] 1 3 3 ; D ; 1 ESC \\   ==  \\x1b]133;D;1\\x1b\\\\   (error, exit 1)"
          }
        ]
      }
    ],
    "variants": [
      {
        "variant_of": "terminal-osc/133",
        "label": "OSC 633 (VS Code)",
        "entry_id": "terminal-osc/633",
        "note": "VS Code's integrated terminal uses OSC 633 as a superset/sibling of OSC 133 (633;A/B/C/D mirror 133, plus 633;E command line, 633;P properties like Cwd). VS Code emits BOTH 133 and 633 for portability. Treat 633 as a distinct entry; cross-linked via see_also."
      },
      {
        "variant_of": "terminal-osc/133",
        "label": "FTCS_COMMAND (P;)",
        "entry_id": "terminal-osc/133",
        "note": "Some implementations add OSC 133 ; P ; key=value ST for aux properties (e.g. Cwd, prompt kind) and OSC 133 ; L for fresh-line. These are extensions in the Semantic Prompts proposal beyond the core A/B/C/D and support varies; treat as partial."
      }
    ],
    "support_matrix": [
      {
        "terminal": "FinalTerm",
        "version_added": "original (defunct)",
        "level": "full",
        "variant_of": null,
        "notes": "Origin of the FTCS sequences; project is defunct but documented by iTerm2."
      },
      {
        "terminal": "iTerm2",
        "version_added": "Shell Integration (3.x)",
        "level": "full",
        "variant_of": null,
        "notes": "Documents the sequences; also defines its own OSC 1337 family for additional shell-integration features."
      },
      {
        "terminal": "VTE / GNOME Terminal",
        "version_added": "VTE 0.66+",
        "level": "full",
        "variant_of": null,
        "notes": "Recognizes OSC 133 A/B/C/D for prompt/command tracking."
      },
      {
        "terminal": "WezTerm",
        "version_added": "documented",
        "level": "full",
        "variant_of": null,
        "notes": "Implements semantic zones from OSC 133; documents shell integration."
      },
      {
        "terminal": "kitty",
        "version_added": "documented",
        "level": "full",
        "variant_of": null,
        "notes": "Uses OSC 133 for shell integration / command tracking."
      },
      {
        "terminal": "Ghostty",
        "version_added": "1.0",
        "level": "full",
        "variant_of": null,
        "notes": "Supports OSC 133 shell integration out of the box."
      },
      {
        "terminal": "Windows Terminal",
        "version_added": "stable shell-integration tutorial",
        "level": "full",
        "variant_of": null,
        "notes": "Documents A/B/C/D identically to Contour; supports D exit-code coloring."
      },
      {
        "terminal": "Contour",
        "version_added": "documented",
        "level": "full",
        "variant_of": null,
        "notes": "Dedicated OSC-133 shell-integration page; authoritative cross-source for A/B/C/D."
      },
      {
        "terminal": "VS Code integrated terminal",
        "version_added": "shell integration",
        "level": "variant",
        "variant_of": "terminal-osc/633",
        "notes": "Prefers OSC 633 (superset) but also accepts/emits OSC 133 for portability."
      },
      {
        "terminal": "Warp",
        "version_added": "documented",
        "level": "partial",
        "variant_of": null,
        "notes": "Block model derives from prompt/command boundaries; uses shell-integration marks though its native model predates a pure 133 dependency."
      },
      {
        "terminal": "DomTerm",
        "version_added": "Per Bothner ref impl",
        "level": "full",
        "variant_of": null,
        "notes": "Reference implementation behind the Semantic Prompts proposal."
      }
    ],
    "gotchas": [
      "Terminator divergence: ECMA-48 requires ST (ESC \\, i.e. \\x1b\\x5c). xterm and nearly every modern terminal ALSO accept BEL (\\x07). Emit ST; accept both when parsing. Mixing a bare ESC followed by an unrelated byte will mis-terminate the string.",
      "Wrap marks in PROMPT_COMMAND/precmd, not inside the visible PS1 width calculation: in bash/zsh the mark bytes must be wrapped in \\[ \\] (bash) or %{ %} (zsh) so the shell does not count them as visible columns, otherwise line editing and wrapping break.",
      "C must be emitted from preexec (just before the command runs), not from precmd, or output folding will include the command line itself.",
      "D's exit code is OPTIONAL; if you always want success/error coloring you must pass it explicitly (\\x1b]133;D;$?\\x1b\\). A bare D leaves the mark untinted.",
      "OSC 633 (VS Code) is NOT the same entry: 633 is a superset with extra subcommands (E command-line, P properties). Do not assume a 133 parser handles 633;P key=value.",
      "There is NO registry for the number 133 itself; collisions are possible in principle but 133 is de-facto reserved for FinalTerm/FTCS across the ecosystem.",
      "8-bit forms (0x9D for OSC, 0x9C for ST) exist per ECMA-48 but are rarely used in UTF-8 locales because they collide with UTF-8 continuation bytes; always prefer the 7-bit ESC-based forms in modern pipelines."
    ],
    "v1_smoke_test": {
      "asserts": "Entry emits a syntactically correct ST-terminated example (\\x1b]133;A\\x1b\\\\) and records that BEL (\\x07) is also accepted on the parsing side, capturing the ECMA-48-vs-practice divergence.",
      "behavioral_conformance": "deferred to v2 (headless VTE harness asserting observed prompt/command/output zones); support_matrix cells are pre-shaped to receive those results."
    }
  },
  "updated": "2026-05-29T00:00:00Z"
}