Composer @ completion started in whitespace can dismiss early and insert with wrong spacing #291

Closed
#936
Closed
Composer @ completion started in whitespace can dismiss early and insert with wrong spacing#291
#936

Description

@mwolson
mwolson
opened on Mar 7, 2026

Summary

Composer @ completion can misbehave when it is started inside existing whitespace.

If the cursor is positioned so there is a space immediately before it and also a space at the cursor position, typing @ opens the completion menu correctly, but follow-up typing and selection can behave incorrectly.

Repro steps

  1. In the composer, insert a file mention so there is already at least one mention pill in the prompt, for example @AGENTS.md.
  2. Continue typing normal text and leave two spaces somewhere later in the prompt.
  3. Move the cursor into that double-space gap so there is one space before the cursor and one space at the cursor position.
  4. Type @.
  5. Type one or two more characters so the menu filters to matching results.
  6. Select a completion.

Expected

  • The completion menu stays open while the typed query still matches results.
  • Selecting a completion replaces the query cleanly.
  • The inserted mention ends with exactly one trailing space.
  • The caret lands immediately after the inserted mention.

Actual

  • In this whitespace-started case, the menu can dismiss while typing even though there is still a valid match.
  • If selection succeeds, the inserted completion can leave an extra trailing space.
  • In related cursor positions, the caret can land farther right than expected after insertion.

Sample setup prompt

Use this to create the setup quickly, then move the cursor back into the double space after then:

Please inspect @AGENTS.md and then summarize how the composer mention picker behaves.

Sample agent prompt

Investigate and fix composer @-completion behavior in the web app.

Problem summary:

  • The composer has mention pills for completed @path references.
  • Cursor handling currently mixes collapsed mention-aware offsets and expanded text offsets.
  • A remaining bug shows up when the user starts an @ completion inside existing whitespace.

Repro target:

  1. In the composer, create at least one existing mention pill, for example @AGENTS.md.
  2. Leave two spaces somewhere later in the prompt.
  3. Put the cursor between those two spaces so there is a space immediately before the cursor and also a space at the cursor position.
  4. Type @, then type a few characters so the completion menu stays filtered.
  5. Select a completion.

Expected behavior:

  • The completion menu should remain open while the typed query still matches results.
  • Selecting a completion should replace the query cleanly.
  • The inserted mention should end with exactly one trailing space.
  • The caret should land immediately after that trailing space.

Known implementation context:

  • Mention parsing/cursor logic lives in apps/web/src/composer-logic.ts.
  • Lexical editor integration lives in apps/web/src/components/ComposerPromptEditor.tsx.
  • Trigger detection and replacement flow live in apps/web/src/components/ChatView.tsx.
  • The bug is likely another edge case where live trigger detection or replacement range calculation is using the wrong cursor coordinate system, or is not consuming an existing space under the cursor when inserting a completion.

Constraints:

  • Preserve existing mention pill behavior.
  • Do not regress cases where completion starts next to non-whitespace text.
  • Add focused tests for the whitespace-started completion case and any cursor/spacing regression you fix.
  • Finish by running bun typecheck.

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      , 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
       blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

      Skip to content
      Composer @ completion started in whitespace can dismiss early and insert with wrong spacing #291
      Closed
      #936
      Closed
      Composer @ completion started in whitespace can dismiss early and insert with wrong spacing#291
      #936
      Description
      @mwolson
      mwolson
      opened on Mar 7, 2026
      Summary
      Composer @ completion can misbehave when it is started inside existing whitespace.
      If the cursor is positioned so there is a space immediately before it and also a space at the cursor position, typing @ opens the completion menu correctly, but follow-up typing and selection can behave incorrectly.
      Repro steps
      1. In the composer, insert a file mention so there is already at least one mention pill in the prompt, for example @AGENTS.md.
      2. Continue typing normal text and leave two spaces somewhere later in the prompt.
      3. Move the cursor into that double-space gap so there is one space before the cursor and one space at the cursor position.
      4. Type @.
      5. Type one or two more characters so the menu filters to matching results.
      6. Select a completion.
      Expected
      • The completion menu stays open while the typed query still matches results.
      • Selecting a completion replaces the query cleanly.
      • The inserted mention ends with exactly one trailing space.
      • The caret lands immediately after the inserted mention.
      Actual
      • In this whitespace-started case, the menu can dismiss while typing even though there is still a valid match.
      • If selection succeeds, the inserted completion can leave an extra trailing space.
      • In related cursor positions, the caret can land farther right than expected after insertion.
      Sample setup prompt
      Use this to create the setup quickly, then move the cursor back into the double space after then:
      Please inspect @AGENTS.md and then summarize how the composer mention picker behaves.
      Sample agent prompt
      Investigate and fix composer @-completion behavior in the web app.
      Problem summary:
      • The composer has mention pills for completed @path references.
      • Cursor handling currently mixes collapsed mention-aware offsets and expanded text offsets.
      • A remaining bug shows up when the user starts an @ completion inside existing whitespace.
      Repro target:
      1. In the composer, create at least one existing mention pill, for example @AGENTS.md.
      2. Leave two spaces somewhere later in the prompt.
      3. Put the cursor between those two spaces so there is a space immediately before the cursor and also a space at the cursor position.
      4. Type @, then type a few characters so the completion menu stays filtered.
      5. Select a completion.
      Expected behavior:
      • The completion menu should remain open while the typed query still matches results.
      • Selecting a completion should replace the query cleanly.
      • The inserted mention should end with exactly one trailing space.
      • The caret should land immediately after that trailing space.
      Known implementation context:
      • Mention parsing/cursor logic lives in apps/web/src/composer-logic.ts.
      • Lexical editor integration lives in apps/web/src/components/ComposerPromptEditor.tsx.
      • Trigger detection and replacement flow live in apps/web/src/components/ChatView.tsx.
      • The bug is likely another edge case where live trigger detection or replacement range calculation is using the wrong cursor coordinate system, or is not consuming an existing space under the cursor when inserting a completion.
      Constraints:
      • Preserve existing mention pill behavior.
      • Do not regress cases where completion starts next to non-whitespace text.
      • Add focused tests for the whitespace-started completion case and any cursor/spacing regression you fix.
      • Finish by running bun typecheck.
      Metadata
      Metadata
      Assignees
      No one assigned
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        No type
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        No projects
          Milestone
          No milestone
          Relationships
          None yet
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          No branches or pull requests
          Issue actions
          
, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

          Skip to content
          Composer @ completion started in whitespace can dismiss early and insert with wrong spacing #291
          Closed
          #936
          Closed
          Composer @ completion started in whitespace can dismiss early and insert with wrong spacing#291
          #936
          Description
          @mwolson
          mwolson
          opened on Mar 7, 2026
          Summary
          Composer @ completion can misbehave when it is started inside existing whitespace.
          If the cursor is positioned so there is a space immediately before it and also a space at the cursor position, typing @ opens the completion menu correctly, but follow-up typing and selection can behave incorrectly.
          Repro steps
          1. In the composer, insert a file mention so there is already at least one mention pill in the prompt, for example @AGENTS.md.
          2. Continue typing normal text and leave two spaces somewhere later in the prompt.
          3. Move the cursor into that double-space gap so there is one space before the cursor and one space at the cursor position.
          4. Type @.
          5. Type one or two more characters so the menu filters to matching results.
          6. Select a completion.
          Expected
          • The completion menu stays open while the typed query still matches results.
          • Selecting a completion replaces the query cleanly.
          • The inserted mention ends with exactly one trailing space.
          • The caret lands immediately after the inserted mention.
          Actual
          • In this whitespace-started case, the menu can dismiss while typing even though there is still a valid match.
          • If selection succeeds, the inserted completion can leave an extra trailing space.
          • In related cursor positions, the caret can land farther right than expected after insertion.
          Sample setup prompt
          Use this to create the setup quickly, then move the cursor back into the double space after then:
          Please inspect @AGENTS.md and then summarize how the composer mention picker behaves.
          Sample agent prompt
          Investigate and fix composer @-completion behavior in the web app.
          Problem summary:
          • The composer has mention pills for completed @path references.
          • Cursor handling currently mixes collapsed mention-aware offsets and expanded text offsets.
          • A remaining bug shows up when the user starts an @ completion inside existing whitespace.
          Repro target:
          1. In the composer, create at least one existing mention pill, for example @AGENTS.md.
          2. Leave two spaces somewhere later in the prompt.
          3. Put the cursor between those two spaces so there is a space immediately before the cursor and also a space at the cursor position.
          4. Type @, then type a few characters so the completion menu stays filtered.
          5. Select a completion.
          Expected behavior:
          • The completion menu should remain open while the typed query still matches results.
          • Selecting a completion should replace the query cleanly.
          • The inserted mention should end with exactly one trailing space.
          • The caret should land immediately after that trailing space.
          Known implementation context:
          • Mention parsing/cursor logic lives in apps/web/src/composer-logic.ts.
          • Lexical editor integration lives in apps/web/src/components/ComposerPromptEditor.tsx.
          • Trigger detection and replacement flow live in apps/web/src/components/ChatView.tsx.
          • The bug is likely another edge case where live trigger detection or replacement range calculation is using the wrong cursor coordinate system, or is not consuming an existing space under the cursor when inserting a completion.
          Constraints:
          • Preserve existing mention pill behavior.
          • Do not regress cases where completion starts next to non-whitespace text.
          • Add focused tests for the whitespace-started completion case and any cursor/spacing regression you fix.
          • Finish by running bun typecheck.
          Metadata
          Metadata
          Assignees
          No one assigned
            Labels
            No labels
            No labels
            Type
            No type
            Projects
            No projects
              Milestone
              No milestone
              Relationships
              None yet
              Development
              No branches or pull requests
              Issue actions
              
, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

              Skip to content
              Composer @ completion started in whitespace can dismiss early and insert with wrong spacing #291
              Closed
              #936
              Closed
              Composer @ completion started in whitespace can dismiss early and insert with wrong spacing#291
              #936
              Description
              @mwolson
              mwolson
              opened on Mar 7, 2026
              Summary
              Composer @ completion can misbehave when it is started inside existing whitespace.
              If the cursor is positioned so there is a space immediately before it and also a space at the cursor position, typing @ opens the completion menu correctly, but follow-up typing and selection can behave incorrectly.
              Repro steps
              1. In the composer, insert a file mention so there is already at least one mention pill in the prompt, for example @AGENTS.md.
              2. Continue typing normal text and leave two spaces somewhere later in the prompt.
              3. Move the cursor into that double-space gap so there is one space before the cursor and one space at the cursor position.
              4. Type @.
              5. Type one or two more characters so the menu filters to matching results.
              6. Select a completion.
              Expected
              • The completion menu stays open while the typed query still matches results.
              • Selecting a completion replaces the query cleanly.
              • The inserted mention ends with exactly one trailing space.
              • The caret lands immediately after the inserted mention.
              Actual
              • In this whitespace-started case, the menu can dismiss while typing even though there is still a valid match.
              • If selection succeeds, the inserted completion can leave an extra trailing space.
              • In related cursor positions, the caret can land farther right than expected after insertion.
              Sample setup prompt
              Use this to create the setup quickly, then move the cursor back into the double space after then:
              Please inspect @AGENTS.md and then summarize how the composer mention picker behaves.
              Sample agent prompt
              Investigate and fix composer @-completion behavior in the web app.
              Problem summary:
              • The composer has mention pills for completed @path references.
              • Cursor handling currently mixes collapsed mention-aware offsets and expanded text offsets.
              • A remaining bug shows up when the user starts an @ completion inside existing whitespace.
              Repro target:
              1. In the composer, create at least one existing mention pill, for example @AGENTS.md.
              2. Leave two spaces somewhere later in the prompt.
              3. Put the cursor between those two spaces so there is a space immediately before the cursor and also a space at the cursor position.
              4. Type @, then type a few characters so the completion menu stays filtered.
              5. Select a completion.
              Expected behavior:
              • The completion menu should remain open while the typed query still matches results.
              • Selecting a completion should replace the query cleanly.
              • The inserted mention should end with exactly one trailing space.
              • The caret should land immediately after that trailing space.
              Known implementation context:
              • Mention parsing/cursor logic lives in apps/web/src/composer-logic.ts.
              • Lexical editor integration lives in apps/web/src/components/ComposerPromptEditor.tsx.
              • Trigger detection and replacement flow live in apps/web/src/components/ChatView.tsx.
              • The bug is likely another edge case where live trigger detection or replacement range calculation is using the wrong cursor coordinate system, or is not consuming an existing space under the cursor when inserting a completion.
              Constraints:
              • Preserve existing mention pill behavior.
              • Do not regress cases where completion starts next to non-whitespace text.
              • Add focused tests for the whitespace-started completion case and any cursor/spacing regression you fix.
              • Finish by running bun typecheck.
              Metadata
              Metadata
              Assignees
              No one assigned
                Labels
                No labels
                No labels
                Type
                No type
                Projects
                No projects
                  Milestone
                  No milestone
                  Relationships
                  None yet
                  Development
                  No branches or pull requests
                  Issue actions
                  
, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

                  Skip to content
                  Composer @ completion started in whitespace can dismiss early and insert with wrong spacing #291
                  Closed
                  #936
                  Closed
                  Composer @ completion started in whitespace can dismiss early and insert with wrong spacing#291
                  #936
                  Description
                  @mwolson
                  mwolson
                  opened on Mar 7, 2026
                  Summary
                  Composer @ completion can misbehave when it is started inside existing whitespace.
                  If the cursor is positioned so there is a space immediately before it and also a space at the cursor position, typing @ opens the completion menu correctly, but follow-up typing and selection can behave incorrectly.
                  Repro steps
                  1. In the composer, insert a file mention so there is already at least one mention pill in the prompt, for example @AGENTS.md.
                  2. Continue typing normal text and leave two spaces somewhere later in the prompt.
                  3. Move the cursor into that double-space gap so there is one space before the cursor and one space at the cursor position.
                  4. Type @.
                  5. Type one or two more characters so the menu filters to matching results.
                  6. Select a completion.
                  Expected
                  • The completion menu stays open while the typed query still matches results.
                  • Selecting a completion replaces the query cleanly.
                  • The inserted mention ends with exactly one trailing space.
                  • The caret lands immediately after the inserted mention.
                  Actual
                  • In this whitespace-started case, the menu can dismiss while typing even though there is still a valid match.
                  • If selection succeeds, the inserted completion can leave an extra trailing space.
                  • In related cursor positions, the caret can land farther right than expected after insertion.
                  Sample setup prompt
                  Use this to create the setup quickly, then move the cursor back into the double space after then:
                  Please inspect @AGENTS.md and then summarize how the composer mention picker behaves.
                  Sample agent prompt
                  Investigate and fix composer @-completion behavior in the web app.
                  Problem summary:
                  • The composer has mention pills for completed @path references.
                  • Cursor handling currently mixes collapsed mention-aware offsets and expanded text offsets.
                  • A remaining bug shows up when the user starts an @ completion inside existing whitespace.
                  Repro target:
                  1. In the composer, create at least one existing mention pill, for example @AGENTS.md.
                  2. Leave two spaces somewhere later in the prompt.
                  3. Put the cursor between those two spaces so there is a space immediately before the cursor and also a space at the cursor position.
                  4. Type @, then type a few characters so the completion menu stays filtered.
                  5. Select a completion.
                  Expected behavior:
                  • The completion menu should remain open while the typed query still matches results.
                  • Selecting a completion should replace the query cleanly.
                  • The inserted mention should end with exactly one trailing space.
                  • The caret should land immediately after that trailing space.
                  Known implementation context:
                  • Mention parsing/cursor logic lives in apps/web/src/composer-logic.ts.
                  • Lexical editor integration lives in apps/web/src/components/ComposerPromptEditor.tsx.
                  • Trigger detection and replacement flow live in apps/web/src/components/ChatView.tsx.
                  • The bug is likely another edge case where live trigger detection or replacement range calculation is using the wrong cursor coordinate system, or is not consuming an existing space under the cursor when inserting a completion.
                  Constraints:
                  • Preserve existing mention pill behavior.
                  • Do not regress cases where completion starts next to non-whitespace text.
                  • Add focused tests for the whitespace-started completion case and any cursor/spacing regression you fix.
                  • Finish by running bun typecheck.
                  Metadata
                  Metadata
                  Assignees
                  No one assigned
                    Labels
                    No labels
                    No labels
                    Type
                    No type
                    Projects
                    No projects
                      Milestone
                      No milestone
                      Relationships
                      None yet
                      Development
                      No branches or pull requests
                      Issue actions
                      
, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

                      Skip to content
                      Composer @ completion started in whitespace can dismiss early and insert with wrong spacing #291
                      Closed
                      #936
                      Closed
                      Composer @ completion started in whitespace can dismiss early and insert with wrong spacing#291
                      #936
                      Description
                      @mwolson
                      mwolson
                      opened on Mar 7, 2026
                      Summary
                      Composer @ completion can misbehave when it is started inside existing whitespace.
                      If the cursor is positioned so there is a space immediately before it and also a space at the cursor position, typing @ opens the completion menu correctly, but follow-up typing and selection can behave incorrectly.
                      Repro steps
                      1. In the composer, insert a file mention so there is already at least one mention pill in the prompt, for example @AGENTS.md.
                      2. Continue typing normal text and leave two spaces somewhere later in the prompt.
                      3. Move the cursor into that double-space gap so there is one space before the cursor and one space at the cursor position.
                      4. Type @.
                      5. Type one or two more characters so the menu filters to matching results.
                      6. Select a completion.
                      Expected
                      • The completion menu stays open while the typed query still matches results.
                      • Selecting a completion replaces the query cleanly.
                      • The inserted mention ends with exactly one trailing space.
                      • The caret lands immediately after the inserted mention.
                      Actual
                      • In this whitespace-started case, the menu can dismiss while typing even though there is still a valid match.
                      • If selection succeeds, the inserted completion can leave an extra trailing space.
                      • In related cursor positions, the caret can land farther right than expected after insertion.
                      Sample setup prompt
                      Use this to create the setup quickly, then move the cursor back into the double space after then:
                      Please inspect @AGENTS.md and then summarize how the composer mention picker behaves.
                      Sample agent prompt
                      Investigate and fix composer @-completion behavior in the web app.
                      Problem summary:
                      • The composer has mention pills for completed @path references.
                      • Cursor handling currently mixes collapsed mention-aware offsets and expanded text offsets.
                      • A remaining bug shows up when the user starts an @ completion inside existing whitespace.
                      Repro target:
                      1. In the composer, create at least one existing mention pill, for example @AGENTS.md.
                      2. Leave two spaces somewhere later in the prompt.
                      3. Put the cursor between those two spaces so there is a space immediately before the cursor and also a space at the cursor position.
                      4. Type @, then type a few characters so the completion menu stays filtered.
                      5. Select a completion.
                      Expected behavior:
                      • The completion menu should remain open while the typed query still matches results.
                      • Selecting a completion should replace the query cleanly.
                      • The inserted mention should end with exactly one trailing space.
                      • The caret should land immediately after that trailing space.
                      Known implementation context:
                      • Mention parsing/cursor logic lives in apps/web/src/composer-logic.ts.
                      • Lexical editor integration lives in apps/web/src/components/ComposerPromptEditor.tsx.
                      • Trigger detection and replacement flow live in apps/web/src/components/ChatView.tsx.
                      • The bug is likely another edge case where live trigger detection or replacement range calculation is using the wrong cursor coordinate system, or is not consuming an existing space under the cursor when inserting a completion.
                      Constraints:
                      • Preserve existing mention pill behavior.
                      • Do not regress cases where completion starts next to non-whitespace text.
                      • Add focused tests for the whitespace-started completion case and any cursor/spacing regression you fix.
                      • Finish by running bun typecheck.
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

                          Skip to content
                          Composer @ completion started in whitespace can dismiss early and insert with wrong spacing #291
                          Closed
                          #936
                          Closed
                          Composer @ completion started in whitespace can dismiss early and insert with wrong spacing#291
                          #936
                          Description
                          @mwolson
                          mwolson
                          opened on Mar 7, 2026
                          Summary
                          Composer @ completion can misbehave when it is started inside existing whitespace.
                          If the cursor is positioned so there is a space immediately before it and also a space at the cursor position, typing @ opens the completion menu correctly, but follow-up typing and selection can behave incorrectly.
                          Repro steps
                          1. In the composer, insert a file mention so there is already at least one mention pill in the prompt, for example @AGENTS.md.
                          2. Continue typing normal text and leave two spaces somewhere later in the prompt.
                          3. Move the cursor into that double-space gap so there is one space before the cursor and one space at the cursor position.
                          4. Type @.
                          5. Type one or two more characters so the menu filters to matching results.
                          6. Select a completion.
                          Expected
                          • The completion menu stays open while the typed query still matches results.
                          • Selecting a completion replaces the query cleanly.
                          • The inserted mention ends with exactly one trailing space.
                          • The caret lands immediately after the inserted mention.
                          Actual
                          • In this whitespace-started case, the menu can dismiss while typing even though there is still a valid match.
                          • If selection succeeds, the inserted completion can leave an extra trailing space.
                          • In related cursor positions, the caret can land farther right than expected after insertion.
                          Sample setup prompt
                          Use this to create the setup quickly, then move the cursor back into the double space after then:
                          Please inspect @AGENTS.md and then summarize how the composer mention picker behaves.
                          Sample agent prompt
                          Investigate and fix composer @-completion behavior in the web app.
                          Problem summary:
                          • The composer has mention pills for completed @path references.
                          • Cursor handling currently mixes collapsed mention-aware offsets and expanded text offsets.
                          • A remaining bug shows up when the user starts an @ completion inside existing whitespace.
                          Repro target:
                          1. In the composer, create at least one existing mention pill, for example @AGENTS.md.
                          2. Leave two spaces somewhere later in the prompt.
                          3. Put the cursor between those two spaces so there is a space immediately before the cursor and also a space at the cursor position.
                          4. Type @, then type a few characters so the completion menu stays filtered.
                          5. Select a completion.
                          Expected behavior:
                          • The completion menu should remain open while the typed query still matches results.
                          • Selecting a completion should replace the query cleanly.
                          • The inserted mention should end with exactly one trailing space.
                          • The caret should land immediately after that trailing space.
                          Known implementation context:
                          • Mention parsing/cursor logic lives in apps/web/src/composer-logic.ts.
                          • Lexical editor integration lives in apps/web/src/components/ComposerPromptEditor.tsx.
                          • Trigger detection and replacement flow live in apps/web/src/components/ChatView.tsx.
                          • The bug is likely another edge case where live trigger detection or replacement range calculation is using the wrong cursor coordinate system, or is not consuming an existing space under the cursor when inserting a completion.
                          Constraints:
                          • Preserve existing mention pill behavior.
                          • Do not regress cases where completion starts next to non-whitespace text.
                          • Add focused tests for the whitespace-started completion case and any cursor/spacing regression you fix.
                          • Finish by running bun typecheck.
                          Metadata
                          Metadata
                          Assignees
                          No one assigned
                            Labels
                            No labels
                            No labels
                            Type
                            No type
                            Projects
                            No projects
                              Milestone
                              No milestone
                              Relationships
                              None yet
                              Development
                              No branches or pull requests
                              Issue actions
                              
, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

                              Skip to content
                              Composer @ completion started in whitespace can dismiss early and insert with wrong spacing #291
                              Closed
                              #936
                              Closed
                              Composer @ completion started in whitespace can dismiss early and insert with wrong spacing#291
                              #936
                              Description
                              @mwolson
                              mwolson
                              opened on Mar 7, 2026
                              Summary
                              Composer @ completion can misbehave when it is started inside existing whitespace.
                              If the cursor is positioned so there is a space immediately before it and also a space at the cursor position, typing @ opens the completion menu correctly, but follow-up typing and selection can behave incorrectly.
                              Repro steps
                              1. In the composer, insert a file mention so there is already at least one mention pill in the prompt, for example @AGENTS.md.
                              2. Continue typing normal text and leave two spaces somewhere later in the prompt.
                              3. Move the cursor into that double-space gap so there is one space before the cursor and one space at the cursor position.
                              4. Type @.
                              5. Type one or two more characters so the menu filters to matching results.
                              6. Select a completion.
                              Expected
                              • The completion menu stays open while the typed query still matches results.
                              • Selecting a completion replaces the query cleanly.
                              • The inserted mention ends with exactly one trailing space.
                              • The caret lands immediately after the inserted mention.
                              Actual
                              • In this whitespace-started case, the menu can dismiss while typing even though there is still a valid match.
                              • If selection succeeds, the inserted completion can leave an extra trailing space.
                              • In related cursor positions, the caret can land farther right than expected after insertion.
                              Sample setup prompt
                              Use this to create the setup quickly, then move the cursor back into the double space after then:
                              Please inspect @AGENTS.md and then summarize how the composer mention picker behaves.
                              Sample agent prompt
                              Investigate and fix composer @-completion behavior in the web app.
                              Problem summary:
                              • The composer has mention pills for completed @path references.
                              • Cursor handling currently mixes collapsed mention-aware offsets and expanded text offsets.
                              • A remaining bug shows up when the user starts an @ completion inside existing whitespace.
                              Repro target:
                              1. In the composer, create at least one existing mention pill, for example @AGENTS.md.
                              2. Leave two spaces somewhere later in the prompt.
                              3. Put the cursor between those two spaces so there is a space immediately before the cursor and also a space at the cursor position.
                              4. Type @, then type a few characters so the completion menu stays filtered.
                              5. Select a completion.
                              Expected behavior:
                              • The completion menu should remain open while the typed query still matches results.
                              • Selecting a completion should replace the query cleanly.
                              • The inserted mention should end with exactly one trailing space.
                              • The caret should land immediately after that trailing space.
                              Known implementation context:
                              • Mention parsing/cursor logic lives in apps/web/src/composer-logic.ts.
                              • Lexical editor integration lives in apps/web/src/components/ComposerPromptEditor.tsx.
                              • Trigger detection and replacement flow live in apps/web/src/components/ChatView.tsx.
                              • The bug is likely another edge case where live trigger detection or replacement range calculation is using the wrong cursor coordinate system, or is not consuming an existing space under the cursor when inserting a completion.
                              Constraints:
                              • Preserve existing mention pill behavior.
                              • Do not regress cases where completion starts next to non-whitespace text.
                              • Add focused tests for the whitespace-started completion case and any cursor/spacing regression you fix.
                              • Finish by running bun typecheck.
                              Metadata
                              Metadata
                              Assignees
                              No one assigned
                                Labels
                                No labels
                                No labels
                                Type
                                No type
                                Projects
                                No projects
                                  Milestone
                                  No milestone
                                  Relationships
                                  None yet
                                  Development
                                  No branches or pull requests
                                  Issue actions