fix(cli): restore fallback paste collapse + handle long single-line pastes (#32447)

Follow-up to #32087 after community report from @ethernet that 8000-char
single-line pastes get dumped raw into the input box.

A) Fallback regression revert
   paste_collapse_threshold_fallback default: 0 -> 5
   #32087 disabled the fallback handler by default. The fallback path
   has been always-on with line_count >= 5 since #3065 (March 2026);
   the previous shape was the salvaged contributor's design and didn't
   match pre-existing behavior for terminals without bracketed paste
   support (Windows terminals, some SSH setups). Restoring the original
   on-by-default.

B) Long single-line paste guard
   New config key: paste_collapse_char_threshold (default 2000)
   Bracketed-paste handler and fallback handler now BOTH collapse when
   line count >= line threshold OR total char length >= char threshold.
   Catches the case ethernet hit: ~8000 chars of minified JSON / log
   output on a single line dumped raw into the buffer.
   TUI mirrors the same config via uiStore.pasteCollapseChars.
   Set 0 to disable.

Defaults verified:
  paste_collapse_threshold: 5
  paste_collapse_threshold_fallback: 5
  paste_collapse_char_threshold: 2000

Tests:
  tests/hermes_cli/test_config.py: 87/87 pass
  ui-tui useConfigSync.test.ts: 34/34 pass
  ui-tui useComposerState.test.ts: 9/9 pass
  tsc: 0 new errors in touched files

cli.py

@@ -13352,7 +13352,10 @@ class HermesCLI:
                 line_count = pasted_text.count('\n')
                 buf = event.current_buffer
                 threshold = self.config.get("paste_collapse_threshold", 5)
-                if threshold > 0 and line_count >= threshold and not buf.text.strip().startswith('/'):
+                char_threshold = self.config.get("paste_collapse_char_threshold", 2000)
+                lines_hit = threshold > 0 and line_count >= threshold
+                chars_hit = char_threshold > 0 and len(pasted_text) >= char_threshold
+                if (lines_hit or chars_hit) and not buf.text.strip().startswith('/'):
                     _paste_counter[0] += 1
                     paste_dir = _hermes_home / "pastes"
                     paste_dir.mkdir(parents=True, exist_ok=True)
@@ -13521,8 +13524,11 @@ class HermesCLI:
             newlines_added = line_count - _prev_newline_count[0]
             _prev_newline_count[0] = line_count
             is_paste = chars_added > 1 or newlines_added >= 4
-            threshold = self.config.get("paste_collapse_threshold_fallback", 0)
+            threshold = self.config.get("paste_collapse_threshold_fallback", 5)
-            if threshold > 0 and line_count >= threshold and is_paste and not text.startswith('/'):
+            char_threshold = self.config.get("paste_collapse_char_threshold", 2000)
+            lines_hit = threshold > 0 and line_count >= threshold
+            chars_hit = char_threshold > 0 and len(text) >= char_threshold
+            if (lines_hit or chars_hit) and is_paste and not text.startswith('/'):
                 _paste_counter[0] += 1
                 paste_dir = _hermes_home / "pastes"
                 paste_dir.mkdir(parents=True, exist_ok=True)

hermes_cli/config.py

@@ -1905,13 +1905,25 @@ DEFAULT_CONFIG = {
     },
 
     # Paste collapse thresholds (TUI + CLI).
-    # collapse_threshold: paste collapses to a file reference when line count
+    #
-    #   exceeds this value (bracketed paste, safe: appends to existing text).
+    # paste_collapse_threshold (default 5)
-    # collapse_threshold_fallback: same but for the fallback heuristic used
+    #   Bracketed-paste handler. Pastes with this many newlines or more
-    #   by terminals without bracketed paste support (destructive: replaces
+    #   collapse to a file reference. Set 0 to disable.
-    #   entire buffer).  0 = disabled.
+    #
+    # paste_collapse_threshold_fallback (default 5)
+    #   Fallback heuristic for terminals without bracketed paste support.
+    #   Same line count test but heuristically gated by chars-added /
+    #   newlines-added to avoid false positives from normal typing.
+    #   Set 0 to disable.
+    #
+    # paste_collapse_char_threshold (default 2000)
+    #   Long single-line paste guard. Pastes whose total char length
+    #   reaches this value collapse to a file reference even if line
+    #   count is below the line threshold. Catches the "8000 chars of
+    #   minified JSON / log output on one line" case. Set 0 to disable.
     "paste_collapse_threshold": 5,
-    "paste_collapse_threshold_fallback": 0,
+    "paste_collapse_threshold_fallback": 5,
+    "paste_collapse_char_threshold": 2000,
 
 
     # Config schema version - bump this when adding new required fields

ui-tui/src/app/interfaces.ts

@@ -106,6 +106,7 @@ export interface UiState {
   inlineDiffs: boolean
   mouseTracking: MouseTrackingMode
   pasteCollapseLines: number
+  pasteCollapseChars: number
 
   sections: SectionVisibility
   showCost: boolean

ui-tui/src/app/uiStore.ts

@@ -18,6 +18,7 @@ const buildUiState = (): UiState => ({
   inlineDiffs: true,
   mouseTracking: MOUSE_TRACKING,
   pasteCollapseLines: 5,
+  pasteCollapseChars: 2000,
   sections: {},
   showCost: false,
   showReasoning: false,

ui-tui/src/app/useComposerState.ts

@@ -190,8 +190,11 @@ export function useComposerState({
 
       const lineCount = cleanedText.split('\n').length
       const pasteCollapseLines = getUiState().pasteCollapseLines
+      const pasteCollapseChars = getUiState().pasteCollapseChars
+      const linesHit = pasteCollapseLines > 0 && lineCount >= pasteCollapseLines
+      const charsHit = pasteCollapseChars > 0 && cleanedText.length >= pasteCollapseChars
 
-      if (pasteCollapseLines === 0 || lineCount < pasteCollapseLines) {
+      if (!linesHit && !charsHit) {
         return {
           cursor: cursor + cleanedText.length,
           value: value.slice(0, cursor) + cleanedText + value.slice(cursor)

ui-tui/src/app/useConfigSync.ts

@@ -153,6 +153,17 @@ const _pasteCollapseLinesFromConfig = (cfg: ConfigFullResponse | null): number =
   return 5
 }
 
+const _pasteCollapseCharsFromConfig = (cfg: ConfigFullResponse | null): number => {
+  if (!cfg?.config) return 2000
+  const raw = cfg.config.paste_collapse_char_threshold
+  if (typeof raw === 'number' && Number.isFinite(raw) && raw >= 0) return Math.round(raw)
+  if (typeof raw === 'string') {
+    const n = parseInt(raw, 10)
+    if (Number.isFinite(n) && n >= 0) return n
+  }
+  return 2000
+}
+
 /** Fetch ``config.get full`` and fan the result through ``applyDisplay``.
  *
  * Extracted so the mtime-reload path can be exercised by the test
@@ -200,6 +211,7 @@ export const applyDisplay = (
     inlineDiffs: d.inline_diffs !== false,
     mouseTracking: normalizeMouseTracking(d),
     pasteCollapseLines: _pasteCollapseLinesFromConfig(cfg),
+    pasteCollapseChars: _pasteCollapseCharsFromConfig(cfg),
     sections: resolveSections(d.sections),
     showCost: !!d.show_cost,
     showReasoning: !!d.show_reasoning,

ui-tui/src/gatewayTypes.ts

@@ -82,7 +82,7 @@ export interface ConfigVoiceConfig {
 }
 
 export interface ConfigFullResponse {
-  config?: { display?: ConfigDisplayConfig; voice?: ConfigVoiceConfig; paste_collapse_threshold?: number }
+  config?: { display?: ConfigDisplayConfig; voice?: ConfigVoiceConfig; paste_collapse_threshold?: number; paste_collapse_char_threshold?: number }
 }
 
 export interface ConfigMtimeResponse {