Rename the diff-line-metadata OSC from 456 to 1717

The terminal-allocation audit settled the protocol's OSC number on 1717 (unused
by every surveyed terminal — see diff-line-metadata-osc-spec.md), retiring the
456 placeholder. Rename the host side to match: the gocui carrier that accumulates
and reads back the sequence, the parser, and the handshake env var the pager
subprocess is given (now EMIT_OSC1717_METADATA). Flip the design notes and spec
from 'rename pending' to done.

The delta and difftastic emitters are renamed in their own repos.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

diff-line-metadata-notes.md

@@ -230,9 +230,9 @@ through `Diff.AdjustLineNumber` before opening the editor, exactly as today
 > iTerm2, Windows Terminal, Ghostty, VS Code, ConEmu, urxvt**; `1717` collides with
 > none and sits in the large empty 1400–5000 band (only iTerm2's `1337` is nearby).
 > The full danger list is in the spec appendix (`diff-line-metadata-osc-spec.md`).
-> **The prototype code (delta/difftastic/gocui/lazygit + the `EMIT_OSC456_METADATA`
-> env var) still uses `456`** — renaming `456`→`1717` across the three repos is a
-> tracked follow-up, not yet done.
+> **The prototype code has been renamed `456`→`1717`** across all three repos
+> (delta/difftastic/gocui/lazygit), and the handshake env var is now
+> `EMIT_OSC1717_METADATA`; builds + the metadata unit tests are green in each.
 
 Known-used slots to avoid (verified in the audit): `0–3` (title/icon/X11),
 `4/5/6` (palette/special/tab color), `7` (cwd), `8` (hyperlinks), `9`
@@ -501,8 +501,8 @@ logic is a near-copy of `linenumbers_and_styles`.
 ### 9.2 Pinned v1 wire format (final OSC `1717`; prototype code still uses `456`)
 
 > The number was finalized to **`1717`** after the terminal audit (§3.4); the
-> prototype code still emits `456` (rename is a tracked follow-up). The published
-> spec (`diff-line-metadata-osc-spec.md`) uses `1717`.
+> prototype code has been renamed from the `456` placeholder to emit `1717`. The
+> published spec (`diff-line-metadata-osc-spec.md`) uses `1717`.
 
 ```
 ESC ] 1717 ; <version> ; <type> ; <new-line> ; <old-line> ; <file> ST
@@ -530,8 +530,8 @@ emits V1 when the advertised list contains `V1`.
 - **Terminal-source audit of the OSC number is DONE** (§3.4). Final number is
   **`1717`** (audited against xterm/VTE/kitty/foot/WezTerm/iTerm2/Windows Terminal/
   Ghostty/VS Code/ConEmu/urxvt; danger list in the spec appendix). The prototype
-  code still emits the `456` placeholder — the `456`→`1717` rename across
-  delta/difftastic/gocui/lazygit + the env var is a tracked follow-up.
+  code has been renamed `456`→`1717` across delta/difftastic/gocui/lazygit + the
+  `EMIT_OSC1717_METADATA` env var; builds and metadata unit tests green in each.
 - **Wrapped continuation rows** (`Hunk*Wrapped`) get no attachment in the prototype
   — only the primary content row does. Fine for the normal case (gocui's own
   wrapping is handled host-side by the view-line→buffer-line mapping); delta-level

diff-line-metadata-osc-spec.md

@@ -408,8 +408,8 @@ per-line identity and is not addressed.
 
 ## 10. Reference implementations (prototype)
 
-All three are at prototype quality and emit the v1 format described here (modulo
-the placeholder OSC number, which these used `456` for before `1717` was chosen):
+All three are at prototype quality and emit the v1 format described here, over
+OSC `1717`:
 
 - **delta** — a dedicated additive emitter that injects only OSC bytes (no change
   to styling, width, or wrapping); with the env var unset, output is byte-for-byte

focused-main-view-notes.md

@@ -1339,9 +1339,11 @@ unified single-column wire format is validated (§9.2), side-by-side is validate
 (§17 — v1 needs no addition), and the draft speaks to difftastic's token-vs-line
 mismatch (diff-line-metadata-notes.md §10.2). The **OSC number is resolved to
 `1717`** after a terminal-allocation audit (diff-line-metadata-notes.md §3.4 +
-the spec appendix); `456` is retired as the placeholder. **Still pending:** the
-`456`→`1717` rename across the prototype code (delta/difftastic/gocui/lazygit + the
-`EMIT_OSC456_METADATA` env var), and circulating the draft for feedback.
+the spec appendix); `456` is retired as the placeholder. The `456`→`1717` rename
+across the prototype code (delta/difftastic/gocui/lazygit + the env var, now
+`EMIT_OSC1717_METADATA`) is **done** — builds + metadata unit tests green in each
+repo, and fresh delta/difftastic release binaries built. **Still pending:**
+circulating the draft for feedback.
 
 **Decisions locked (session 6):** concurrency stays **mutex-based**, including for
 productionization (the main-thread-mutation rework is a separate, later effort — do

pkg/gocui/escape.go

@@ -22,7 +22,7 @@ type escapeInterpreter struct {
 
 	// the OSC number being accumulated while we don't yet know which OSC this is
 	oscNumber strings.Builder
-	// the payload of an OSC 456 per-line diff-metadata sequence (see
+	// the payload of an OSC 1717 per-line diff-metadata sequence (see
 	// diff-line-metadata-notes.md), accumulated like hyperlink
 	metadata strings.Builder
 
@@ -435,7 +435,7 @@ func (ei *escapeInterpreter) parseOne(ch []byte) (isEscape bool, err error) {
 	case stateOSC:
 		// Accumulate the OSC number until its terminating ';', then dispatch on
 		// it. (The previous code only recognised the single-digit '8'; a number
-		// like 456 needs more than one character.)
+		// like 1717 needs more than one character.)
 		switch {
 		case len(ch) == 1 && ch[0] >= '0' && ch[0] <= '9':
 			ei.oscNumber.WriteByte(ch[0])
@@ -445,7 +445,7 @@ func (ei *escapeInterpreter) parseOne(ch []byte) (isEscape bool, err error) {
 			case "8":
 				ei.hyperlink.Reset()
 				ei.state = stateOSCParams
-			case "456":
+			case "1717":
 				ei.metadata.Reset()
 				ei.state = stateOSCMetadata
 			default:

pkg/gocui/view.go

@@ -538,7 +538,7 @@ type cell struct {
 	width            int    // number of terminal cells occupied by chr (always 1 or 2)
 	bgColor, fgColor Attribute
 	hyperlink        string
-	// per-line diff metadata from an OSC 456 sequence (see
+	// per-line diff metadata from an OSC 1717 sequence (see
 	// diff-line-metadata-notes.md); empty unless a pager emitted it
 	metadata string
 }
@@ -923,7 +923,7 @@ func (b *viewBuffer) write(v *View, p []byte) {
 		if b.wy >= len(b.lines) {
 			b.lines = append(b.lines, lineType{})
 		}
-		// An OSC 456 diff-metadata sequence applies only to the line it prefixes
+		// An OSC 1717 diff-metadata sequence applies only to the line it prefixes
 		// (the pager re-emits one per line and never closes it), so drop it at the
 		// line boundary rather than letting it carry onto a line with no metadata.
 		b.ei.metadata.Reset()
@@ -1810,7 +1810,7 @@ func (v *View) HyperLinkInLine(y int, urlScheme string) (string, bool) {
 	return "", false
 }
 
-// DiffLineMetadataInLine returns the OSC 456 per-line diff metadata payload
+// DiffLineMetadataInLine returns the OSC 1717 per-line diff metadata payload
 // attached to the given (wrapped) view line, if a pager emitted one. In the
 // single-column case every cell of the line carries the same payload, so the
 // first non-empty one is the answer. See diff-line-metadata-notes.md.
@@ -1834,7 +1834,7 @@ func (v *View) DiffLineMetadataInLine(y int) (string, bool) {
 
 // DiffLineContent is the raw per-line material the diff-line backends parse to
 // recover a rendered row's patch-space identity (see diff-line-metadata-notes.md):
-// the decolorized text (for host-side parsing, mechanism #1), the OSC-456
+// the decolorized text (for host-side parsing, mechanism #1), the OSC-1717
 // metadata payload a pager emitted (#2), and the line's hyperlink (delta's
 // lazygit-edit fallback). It is indexed by unwrapped buffer line, so one entry
 // covers all the (wrapped) view lines that line maps to.

pkg/gocui/view_test.go

@@ -163,10 +163,10 @@ func TestDiffLineMetadata(t *testing.T) {
 	v := NewView("name", 0, 0, 80, 10, OutputNormal)
 
 	// Synthetic delta-style output: each content line is prefixed with an
-	// OSC 456 sequence carrying version;type;new;old;file (old empty unless a
+	// OSC 1717 sequence carrying version;type;new;old;file (old empty unless a
 	// deletion), and the OSC bytes themselves must not become visible cells. The
 	// final line is a header with no OSC, to prove the metadata doesn't bleed.
-	osc := func(payload string) string { return "\x1b]456;" + payload + "\x1b\\" }
+	osc := func(payload string) string { return "\x1b]1717;" + payload + "\x1b\\" }
 	v.writeString(strings.Join([]string{
 		osc("1;c;1;;foo.txt") + "line1",
 		osc("1;d;2;2;foo.txt") + "old2",
@@ -269,7 +269,7 @@ func TestOffscreenDiffLineContents(t *testing.T) {
 	// No off-screen render in progress: nothing to scan.
 	assert.Nil(t, v.OffscreenDiffLineContents())
 
-	osc := func(payload string) string { return "\x1b]456;" + payload + "\x1b\\" }
+	osc := func(payload string) string { return "\x1b]1717;" + payload + "\x1b\\" }
 	v.BeginOffscreenRender()
 	v.writeString(strings.Join([]string{
 		osc("1;c;1;;foo.txt") + "context",

pkg/gui/controllers/helpers/diff_line_parser.go

@@ -156,7 +156,7 @@ func pathFromDiffGitLine(line string) string {
 	return ""
 }
 
-// parseDiffLineMetadata parses mechanism #2's OSC 456 payload (v1):
+// parseDiffLineMetadata parses mechanism #2's OSC 1717 payload (v1):
 // version;type;new-line;old-line;file — positional and ';'-delimited, with the
 // file last (so it may itself contain ';') and old-line empty unless the line is
 // a deletion. See diff-line-metadata-notes.md §9.2. ok is false for a payload of

pkg/gui/pty.go

@@ -105,7 +105,7 @@ func (gui *Gui) newPtyTask(view *gocui.View, cmd *exec.Cmd, prefix string) error
 		// an OSC sequence we can read back (see diff-line-metadata-notes.md). A
 		// pager that doesn't understand it ignores the variable, so this is safe to
 		// set unconditionally.
-		cmd.Env = append(cmd.Env, "EMIT_OSC456_METADATA=V1")
+		cmd.Env = append(cmd.Env, "EMIT_OSC1717_METADATA=V1")
 
 		manager := gui.getManager(view)