2026-08-10 08:57:09 +00:00
13 changed files with 702 additions and 8 deletions
--- a/README.md
+++ b/README.md
@ -19,6 +19,9 @@ threads, create and self-assign issues, discover, claim, and release issue assig
 list repository labels and open milestones, set or clear due dates on assigned issues, create issue comments, close assigned issues,
 inspect/comment on assigned pull
 requests, merge assigned pull requests, and submit pull-request reviews.
+Assigned-issue comments can include one PNG, JPEG, or WebP screenshot up to 2 MB.
+The screenshot uploads before the comment is posted; validation or upload failures keep
+both the typed comment and removable preview available for retry.
 Pull-request replies and mobile My Work issue and PR comments use Gitea's
 issue-comment API. In issue, pull-request, and unread-update conversations, typing
 at least two characters after `@` offers repository-scoped teammate suggestions;
--- a/frontend/dashboard.css
+++ b/frontend/dashboard.css
@ -255,6 +255,14 @@ textarea { resize: vertical; min-height: 120px; }
 .issue-comment { padding:10px 0; border-bottom:1px solid #1b2d45; }
 .issue-comment-composer { display:grid; gap:8px; margin-top:16px; }
 .issue-comment-composer button { min-height:44px; width:100%; }
+.visually-hidden { position:absolute; width:1px; height:1px; padding:0; margin:-1px; overflow:hidden; clip:rect(0,0,0,0); white-space:nowrap; border:0; }
+.issue-attachment-controls { display:flex; max-width:100%; }
+.issue-attachment-trigger { min-height:44px; display:inline-flex; align-items:center; justify-content:center; padding:8px 12px; border:1px solid #60a5fa; border-radius:10px; color:#dbeafe; font-weight:700; cursor:pointer; }
+.issue-attachment-preview { display:grid; grid-template-columns:64px minmax(0,1fr); gap:8px 12px; align-items:center; max-width:100%; overflow:hidden; padding:10px; border:1px solid #315781; border-radius:10px; background:#101f34; }
+.issue-attachment-preview[hidden] { display:none; }
+.issue-attachment-preview img { grid-row:span 2; width:64px; height:64px; object-fit:cover; border-radius:8px; }
+.issue-attachment-preview .small { min-width:0; overflow-wrap:anywhere; }
+.issue-attachment-preview button { min-height:44px; width:auto; justify-self:start; }
 .mention-options { display:grid; max-width:100%; max-height:220px; overflow:auto; border:1px solid #315781; border-radius:10px; background:#101f34; box-shadow:0 10px 28px rgba(0,0,0,.35); }
 .mention-options[hidden] { display:none; }
 .mention-option { min-height:44px; max-width:100%; overflow:hidden; padding:9px 12px; border:0; border-bottom:1px solid #203a5c; border-radius:0; text-align:left; text-overflow:ellipsis; white-space:nowrap; background:#101f34; color:#dbeafe; }
--- a/frontend/dashboard.js
+++ b/frontend/dashboard.js
@ -272,6 +272,37 @@
    mobile: window.matchMedia('(max-width: 600px)').matches,
  });
  const issueController = createIssueSheet({ fetchJson: fetchReviewJson, storage: localStorage });
+  const issueAttachmentController = issueAttachment.mount({
+    input: qs('#issue-attachment'),
+    preview: qs('#issue-attachment-preview'),
+    image: qs('#issue-attachment-image'),
+    meta: qs('#issue-attachment-meta'),
+    remove: qs('#remove-issue-attachment'),
+    status: qs('#issue-comment-status'),
+    createObjectURL: file => URL.createObjectURL(file),
+    revokeObjectURL: url => URL.revokeObjectURL(url),
+    readDataUrl: file => new Promise((resolve, reject) => {
+      const reader = new FileReader();
+      reader.onload = () => resolve(reader.result);
+      reader.onerror = () => reject(new Error('The screenshot could not be read. Choose it again.'));
+      reader.readAsDataURL(file);
+    }),
+    upload: payload => {
+      const repository = payload.repository.split('/').map(encodeURIComponent).join('/');
+      return fetchReviewJson(
+        'api/v1/repos/' + repository + '/issues/' + encodeURIComponent(payload.number) + '/attachments',
+        {
+          method: 'POST',
+          headers: { Accept: 'application/json', 'Content-Type': 'application/json' },
+          body: JSON.stringify({
+            filename: payload.filename,
+            content_type: payload.content_type,
+            data: payload.data,
+          }),
+        },
+      );
+    },
+  });
  const planningLoader = createIssueSheet.createPlanningLoader({
    loadLabels: item => issueController.loadLabels(item),
    loadMilestones: item => issueController.loadMilestones(item),
@ -2143,6 +2174,7 @@
      return;
    }
    mobileComposerViewport.close(qs('#issue-sheet .issue-sheet-panel'));
+    issueAttachmentController.clear();
    qs('#issue-sheet').classList.remove('open');
    selectedIssue = null;
    selectedIssueOffline = false;
@ -3729,7 +3761,7 @@
    const textarea = qs('#' + kind + '-comment');
    const status = qs('#' + kind + '-comment-status');
    const body = textarea.value.trim();
-    if (!body) {
+    if (!body && (kind !== 'issue' || !issueAttachmentController.state())) {
      status.textContent = 'Write a comment before posting.';
      textarea.focus();
      return;
@ -3741,17 +3773,21 @@
      item.repository + '#' + item.number + ':operation');
    postButton.disabled = true;
    nextButton.disabled = true;
-    status.textContent = 'Posting comment and opening next…';
+    status.textContent = kind === 'issue' && issueAttachmentController.state() ?
+      'Uploading screenshot before opening next…' : 'Posting comment and opening next…';
    try {
-      const result = await controller.submit(item, body, operationId);
+      const preparedBody = kind === 'issue' ?
+        await issueAttachmentController.prepareComment(item, body) : body;
+      const result = await controller.submit(item, preparedBody, operationId);
      const stillOpen = kind === 'issue' ? selectedIssue === item : selectedPull === item;
      if (!stillOpen) return;
+      if (kind === 'issue') issueAttachmentController.clear();
      if (!result.completed) status.textContent = 'Comment saved, but Today still needs completion.';
      else if (result.delivery === 'posted') status.textContent = 'Comment posted.';
      else if (result.background) status.textContent = 'Queued for sync when the connection returns.';
      else status.textContent = 'Saved for next launch; background delivery unavailable.';
    } catch (error) {
-      status.textContent = error.message + ' Your draft and Today position are safe; retry.';
+      status.textContent = error.message + ' Your draft, screenshot, and Today position are safe; retry.';
      textarea.focus();
    } finally {
      postButton.disabled = false;
@ -3763,28 +3799,40 @@
  qs('#send-issue-comment').addEventListener('click', async () => {
    if (!selectedIssue) return;
    const body = qs('#issue-comment').value.trim();
-    if (!body) {
+    if (!body && !issueAttachmentController.state()) {
      qs('#issue-comment-status').textContent = 'Write a comment before posting.';
      qs('#issue-comment').focus();
      return;
    }
    const button = qs('#send-issue-comment');
    button.disabled = true;
-    qs('#issue-comment-status').textContent = 'Posting comment…';
+    qs('#issue-comment-status').textContent = issueAttachmentController.state() ?
+      'Uploading screenshot…' : 'Posting comment…';
+    let preparedBody;
    try {
-      const comment = await issueController.comment(selectedIssue, body);
+      preparedBody = await issueAttachmentController.prepareComment(selectedIssue, body);
+    } catch (error) {
+      qs('#issue-comment-status').textContent = error.message + ' Your comment and screenshot are safe; retry.';
+      qs('#issue-comment').focus();
+      button.disabled = false;
+      return;
+    }
+    try {
+      const comment = await issueController.comment(selectedIssue, preparedBody);
      if (issueConversation) renderIssueConversation(issueConversation.append(comment));
      qs('#issue-comment').value = '';
+      issueAttachmentController.clear();
      qs('#issue-comment-status').textContent = 'Comment posted.';
    } catch (error) {
      if (canQueueMessage(error)) {
        const operationId = localStorage.getItem('stackchain.issue-comment.v1:' + selectedIssue.repository + '#' + selectedIssue.number + ':operation');
        qs('#issue-comment-status').textContent = 'Saving for background delivery…';
        const admission = await authoredOutbox.enqueueDurably({ kind:'issue-comment', repository:selectedIssue.repository,
-          number:selectedIssue.number, body, operationId });
+          number:selectedIssue.number, body:preparedBody, operationId });
        refreshMyWorkView();
        if (admission.background) {
          qs('#issue-comment').value = '';
+          issueAttachmentController.clear();
          qs('#issue-comment-status').textContent = 'Queued for sync when the connection returns.';
        } else {
          qs('#issue-comment-status').textContent = 'Saved for next launch; background delivery unavailable.';
--- a/frontend/index.html
+++ b/frontend/index.html
@ -297,6 +297,15 @@
      <textarea id="issue-comment" maxlength="10000" placeholder="Write a comment"></textarea>
      <div class="mention-options" id="issue-comment-mentions" role="listbox" aria-label="Teammates" hidden></div>
      <div class="mention-status small" id="issue-comment-mention-status" aria-live="polite"></div>
+      <div class="issue-attachment-controls">
+        <input class="visually-hidden" id="issue-attachment" type="file" accept="image/png,image/jpeg,image/webp" />
+        <label class="issue-attachment-trigger" for="issue-attachment">Attach screenshot</label>
+      </div>
+      <div class="issue-attachment-preview" id="issue-attachment-preview" hidden>
+        <img id="issue-attachment-image" alt="Selected screenshot preview" />
+        <span class="small" id="issue-attachment-meta"></span>
+        <button id="remove-issue-attachment" type="button">Remove screenshot</button>
+      </div>
      <div class="comment-actions">
        <button id="send-issue-comment" type="button">Post comment</button>
        <button id="send-issue-comment-next" type="button" hidden>Comment &amp; next</button>
@ -660,6 +669,7 @@
 <script src="static/later-picker.js"></script>
 <script src="static/pick-work.js"></script>
 <script src="static/conversation.js"></script>
+<script src="static/issue-attachment.js"></script>
 <script src="static/issue-sheet.js"></script>
 <script src="static/create-issue-sheet.js"></script>
 <script src="static/create-and-start.js"></script>
--- a/frontend/issue-attachment.js
+++ b/frontend/issue-attachment.js
@ -0,0 +1,107 @@
+(function(root, factory) {
+  const api = factory();
+  if (typeof module === 'object' && module.exports) module.exports = api;
+  else root.issueAttachment = api;
+})(typeof self !== 'undefined' ? self : this, function() {
+  'use strict';
+
+  const MAX_BYTES = 2 * 1024 * 1024;
+  const IMAGE_TYPES = new Set(['image/png', 'image/jpeg', 'image/webp']);
+
+  function create(options) {
+    const readDataUrl = options.readDataUrl;
+    const upload = options.upload;
+    let selected = null;
+    let confirmed = null;
+
+    function select(file) {
+      if (!file || !IMAGE_TYPES.has(file.type)) {
+        throw new Error('Choose a PNG, JPEG, or WebP screenshot.');
+      }
+      if (!Number.isFinite(file.size) || file.size <= 0 || file.size > MAX_BYTES) {
+        throw new Error('Choose a screenshot that is 2 MB or smaller.');
+      }
+      selected = file;
+      confirmed = null;
+      return state();
+    }
+
+    function clear() {
+      selected = null;
+      confirmed = null;
+    }
+
+    function state() {
+      return selected ? {
+        name: selected.name,
+        size: selected.size,
+        uploaded: Boolean(confirmed),
+      } : null;
+    }
+
+    async function prepareComment(item, body) {
+      const text = String(body || '').trim();
+      if (!selected) return text;
+      if (!confirmed) {
+        const dataUrl = await readDataUrl(selected);
+        const marker = ';base64,';
+        const markerAt = String(dataUrl).indexOf(marker);
+        if (markerAt < 0) throw new Error('The screenshot could not be read. Choose it again.');
+        confirmed = await upload({
+          repository: item.repository,
+          number: item.number,
+          filename: selected.name,
+          content_type: selected.type,
+          data: String(dataUrl).slice(markerAt + marker.length),
+        });
+        if (!confirmed || typeof confirmed.markdown !== 'string' || !confirmed.markdown) {
+          confirmed = null;
+          throw new Error('The server did not confirm the screenshot upload.');
+        }
+      }
+      return text ? text + '\n\n' + confirmed.markdown : confirmed.markdown;
+    }
+
+    return { select, clear, state, prepareComment };
+  }
+
+  function mount(options) {
+    const controller = create(options);
+    const clearSelection = controller.clear;
+    let previewUrl = '';
+
+    function clearPreview() {
+      if (previewUrl) options.revokeObjectURL(previewUrl);
+      previewUrl = '';
+      options.image.src = '';
+      options.preview.hidden = true;
+      options.input.value = '';
+      clearSelection();
+    }
+
+    options.input.addEventListener('change', event => {
+      const file = event.target.files && event.target.files[0];
+      try {
+        controller.select(file);
+      } catch (error) {
+        options.status.textContent = error.message;
+        options.input.value = '';
+        return;
+      }
+      if (previewUrl) options.revokeObjectURL(previewUrl);
+      previewUrl = options.createObjectURL(file);
+      options.image.src = previewUrl;
+      options.meta.textContent = file.name + ' · ' + Math.ceil(file.size / 1024) + ' KB';
+      options.preview.hidden = false;
+      options.status.textContent = 'Screenshot ready to upload with this comment.';
+    });
+    options.remove.addEventListener('click', () => {
+      clearPreview();
+      options.status.textContent = 'Screenshot removed. Your comment is unchanged.';
+    });
+
+    return Object.assign(controller, { clear: clearPreview });
+  }
+
+  return { create, mount, MAX_BYTES };
+});
--- a/frontend/service-worker.js
+++ b/frontend/service-worker.js
@ -42,6 +42,7 @@ const SHELL = [
  BASE + 'static/later-picker.js',
  BASE + 'static/pick-work.js',
  BASE + 'static/conversation.js',
+  BASE + 'static/issue-attachment.js',
  BASE + 'static/issue-sheet.js',
  BASE + 'static/create-issue-sheet.js',
  BASE + 'static/create-and-start.js',
--- a/src/gitea_proxy.py
+++ b/src/gitea_proxy.py
@ -878,6 +878,33 @@ async def comment_on_issue(repository: str, number: int, body: str) -> dict:
    return _normalize_issue_comment(comment)


+async def upload_assigned_issue_attachment(
+    repository: str,
+    number: int,
+    filename: str,
+    content_type: str,
+    content: bytes,
+) -> dict:
+    if not await is_assigned_issue(repository, number):
+        raise IssueNotAvailableError("Assigned issue not found")
+    response = await _get_client().post(
+        f"/api/v1/repos/{repository}/issues/{number}/assets",
+        headers=_auth(),
+        params={"name": filename},
+        files={"attachment": (filename, content, content_type)},
+    )
+    response.raise_for_status()
+    attachment = response.json()
+    if not isinstance(attachment, dict):
+        raise ValueError("Gitea attachment response was not an object")
+    name = attachment.get("name")
+    url = _safe_web_url(attachment.get("browser_download_url"))
+    size = attachment.get("size")
+    if not isinstance(name, str) or not name or not url or not isinstance(size, int):
+        raise ValueError("Gitea did not confirm the attachment")
+    return {"name": name, "url": url, "size": size}
+
+
 async def repo_labels(repository: str) -> list[dict]:
    response = await _get_client().get(
        f"/api/v1/repos/{repository}/labels",
--- a/src/main.py
+++ b/src/main.py
@ -1,4 +1,6 @@
 import asyncio
+import base64
+import binascii
 import hmac
 import math
 import os
@ -310,6 +312,46 @@ class IssueComment(BaseModel):
        return value


+class IssueAttachment(BaseModel):
+    filename: str = Field(min_length=1, max_length=255)
+    content_type: Literal["image/png", "image/jpeg", "image/webp"]
+    data: str = Field(min_length=1, max_length=2_800_000)
+
+    @model_validator(mode="after")
+    def validate_filename(self):
+        if (
+            "/" in self.filename
+            or "\\" in self.filename
+            or any(ord(character) < 32 for character in self.filename)
+        ):
+            raise ValueError("attachment filename must be a plain file name")
+        extension = self.filename.rsplit(".", 1)[-1].lower() if "." in self.filename else ""
+        expected = {
+            "image/png": {"png"},
+            "image/jpeg": {"jpg", "jpeg"},
+            "image/webp": {"webp"},
+        }
+        if extension not in expected[self.content_type]:
+            raise ValueError("attachment filename must match the selected image type")
+        return self
+
+    def content(self) -> bytes:
+        try:
+            content = base64.b64decode(self.data, validate=True)
+        except (ValueError, binascii.Error) as exc:
+            raise ValueError("attachment data must be valid base64") from exc
+        if len(content) > 2 * 1024 * 1024:
+            raise ValueError("screenshot must be 2 MB or smaller")
+        signatures = {
+            "image/png": content.startswith(b"\x89PNG\r\n\x1a\n"),
+            "image/jpeg": content.startswith(b"\xff\xd8\xff"),
+            "image/webp": content.startswith(b"RIFF") and content[8:12] == b"WEBP",
+        }
+        if not signatures[self.content_type]:
+            raise ValueError("file contents do not match the selected image type")
+        return content
+
+
 class IssueCreation(BaseModel):
    title: str = Field(min_length=1, max_length=255)
    body: str = Field(default="", max_length=10_000)
@ -2728,6 +2770,48 @@ async def comment_on_assigned_issue(
    return JSONResponse(result, status_code=201)


+@app.post("/api/v1/repos/{owner}/{repo}/issues/{number}/attachments", status_code=201)
+async def attach_to_assigned_issue(
+    attachment: IssueAttachment,
+    owner: str,
+    repo: str,
+    number: int = PathParam(gt=0),
+):
+    repository = f"{owner}/{repo}"
+    try:
+        content = attachment.content()
+    except ValueError as exc:
+        raise HTTPException(status_code=422, detail=str(exc)) from exc
+    try:
+        result = await asyncio.wait_for(
+            gitea_proxy.upload_assigned_issue_attachment(
+                repository,
+                number,
+                attachment.filename,
+                attachment.content_type,
+                content,
+            ),
+            timeout=ISSUE_ACTION_TIMEOUT_SECONDS,
+        )
+    except gitea_proxy.IssueNotAvailableError as exc:
+        raise HTTPException(status_code=404, detail="Assigned issue not found") from exc
+    except HTTPException:
+        raise
+    except Exception:
+        return JSONResponse(
+            {"error": "The screenshot could not be uploaded. Your draft is safe; please retry."},
+            status_code=503,
+            headers={"Retry-After": "1"},
+        )
+    safe_name = (
+        result["name"].replace("\\", "\\\\").replace("[", "\\[").replace("]", "\\]")
+        .replace("\r", " ").replace("\n", " ")
+    )
+    safe_url = result["url"].replace("<", "%3C").replace(">", "%3E")
+    result["markdown"] = f"![{safe_name}](<{safe_url}>)"
+    return JSONResponse(result, status_code=201)
+
+
@app.patch("/api/v1/repos/{owner}/{repo}/issues/{number}/close")
 async def close_assigned_issue(
    request: Request,
--- a/src/request_boundary.py
+++ b/src/request_boundary.py
@ -5,6 +5,7 @@ from starlette.types import ASGIApp, Message, Receive, Scope, Send

 SESSION_BODY_LIMIT = 16 * 1024
 API_MUTATION_BODY_LIMIT = 64 * 1024
+ISSUE_ATTACHMENT_BODY_LIMIT = 3 * 1024 * 1024
 MUTATION_METHODS = frozenset({"POST", "PUT", "PATCH"})


@ -13,6 +14,13 @@ def request_body_limit(method: str, path: str) -> int | None:
    normalized_method = method.upper()
    if normalized_method == "POST" and path == "/api/v1/session":
        return SESSION_BODY_LIMIT
+    if (
+        normalized_method == "POST"
+        and path.startswith("/api/v1/repos/")
+        and "/issues/" in path
+        and path.endswith("/attachments")
+    ):
+        return ISSUE_ATTACHMENT_BODY_LIMIT
    if normalized_method in MUTATION_METHODS and path.startswith("/api/v1/"):
        return API_MUTATION_BODY_LIMIT
    return None
--- a/tests/test_issue_attachment_ui.py
+++ b/tests/test_issue_attachment_ui.py
@ -0,0 +1,134 @@
+import json
+import re
+import subprocess
+from pathlib import Path
+
+
+ATTACHMENT = Path(__file__).parents[1] / "frontend" / "issue-attachment.js"
+INDEX = Path(__file__).parents[1] / "frontend" / "index.html"
+CSS = Path(__file__).parents[1] / "frontend" / "dashboard.css"
+DASHBOARD = Path(__file__).parents[1] / "frontend" / "dashboard.js"
+SERVICE_WORKER = Path(__file__).parents[1] / "frontend" / "service-worker.js"
+README = Path(__file__).parents[1] / "README.md"
+
+
+def run_node(script: str) -> str:
+    return subprocess.run(
+        ["node", "-e", script], check=True, capture_output=True, text=True
+    ).stdout
+
+
+def test_mobile_attachment_prepares_comment_and_reuses_confirmed_upload():
+    script = f"""
+const attachment = require({json.dumps(str(ATTACHMENT))});
+const calls = [];
+const file = {{name:'checkout.png', type:'image/png', size:8}};
+const controller = attachment.create({{
+  readDataUrl: async selected => {{ calls.push('read:' + selected.name); return 'data:image/png;base64,iVBORw0KGgo='; }},
+  upload: async payload => {{ calls.push(payload); return {{markdown:'![checkout.png](https://forge.example/a.png)'}}; }},
+}});
+controller.select(file);
+(async()=>{{
+  const first = await controller.prepareComment({{repository:'stackchain/api', number:17}}, 'Layout breaks');
+  const second = await controller.prepareComment({{repository:'stackchain/api', number:17}}, 'Layout breaks');
+  process.stdout.write(JSON.stringify({{first,second,calls,state:controller.state()}}));
+}})().catch(error=>{{ console.error(error); process.exit(1); }});
+"""
+    output = json.loads(run_node(script))
+    assert output["first"] == (
+        "Layout breaks\n\n![checkout.png](https://forge.example/a.png)"
+    )
+    assert output["second"] == output["first"]
+    assert output["calls"] == [
+        "read:checkout.png",
+        {
+            "repository": "stackchain/api",
+            "number": 17,
+            "filename": "checkout.png",
+            "content_type": "image/png",
+            "data": "iVBORw0KGgo=",
+        },
+    ]
+    assert output["state"] == {
+        "name": "checkout.png", "size": 8, "uploaded": True
+    }
+
+
+def test_issue_composer_renders_thumb_reachable_screenshot_preview():
+    html = INDEX.read_text()
+    css = CSS.read_text()
+
+    assert 'id="issue-attachment"' in html
+    assert 'type="file"' in html
+    assert 'accept="image/png,image/jpeg,image/webp"' in html
+    assert 'for="issue-attachment"' in html
+    assert 'id="issue-attachment-preview"' in html
+    assert 'id="remove-issue-attachment"' in html
+    assert '.issue-attachment-trigger' in css
+    assert '.issue-attachment-preview' in css
+    assert 'min-height:44px' in css
+
+
+def test_attachment_view_keeps_invalid_draft_and_removes_preview():
+    script = f"""
+const attachment = require({json.dumps(str(ATTACHMENT))});
+class Element {{
+  constructor() {{ this.listeners={{}}; this.hidden=true; this.value=''; this.files=[]; this.textContent=''; this.src=''; }}
+  addEventListener(type, fn) {{ this.listeners[type]=fn; }}
+  dispatch(type) {{ return this.listeners[type]({{target:this}}); }}
+}}
+const input=new Element(), preview=new Element(), image=new Element(), meta=new Element(), remove=new Element(), status=new Element();
+const revoked=[];
+const controller=attachment.mount({{
+  input,preview,image,meta,remove,status,
+  createObjectURL:()=> 'blob:preview', revokeObjectURL:url=>revoked.push(url),
+  readDataUrl:async()=>'', upload:async()=>{{}},
+}});
+input.files=[{{name:'payload.svg',type:'image/svg+xml',size:20}}]; input.dispatch('change');
+const invalid={{message:status.textContent,hidden:preview.hidden}};
+input.files=[{{name:'screen.png',type:'image/png',size:2048}}]; input.dispatch('change');
+const selected={{src:image.src,meta:meta.textContent,hidden:preview.hidden,state:controller.state()}};
+remove.dispatch('click');
+process.stdout.write(JSON.stringify({{invalid,selected,removed:{{hidden:preview.hidden,src:image.src,revoked,state:controller.state()}}}}));
+"""
+    output = json.loads(run_node(script))
+    assert output["invalid"] == {
+        "message": "Choose a PNG, JPEG, or WebP screenshot.", "hidden": True
+    }
+    assert output["selected"]["src"] == "blob:preview"
+    assert output["selected"]["hidden"] is False
+    assert "screen.png" in output["selected"]["meta"]
+    assert output["removed"] == {
+        "hidden": True, "src": "", "revoked": ["blob:preview"], "state": None
+    }
+
+
+def test_issue_comment_actions_upload_before_posting_and_clear_after_acceptance():
+    source = DASHBOARD.read_text()
+
+    assert "issueAttachment.mount({" in source
+    assert "'/attachments'" in source
+    assert "issueAttachmentController.prepareComment(item, body)" in source
+    assert "issueAttachmentController.prepareComment(selectedIssue, body)" in source
+    assert source.count("issueAttachmentController.clear();") >= 2
+
+
+def test_closing_issue_sheet_cannot_carry_a_screenshot_to_another_issue():
+    source = DASHBOARD.read_text()
+    close_body = re.search(
+        r"function closeIssueSheet\(navigate = true\) \{(?P<body>.*?)\n  \}",
+        source,
+        re.DOTALL,
+    ).group("body")
+    assert "issueAttachmentController.clear();" in close_body
+
+
+def test_attachment_runtime_is_available_in_the_offline_app_shell():
+    assert "static/issue-attachment.js" in SERVICE_WORKER.read_text()
+
+
+def test_readme_documents_mobile_screenshot_limits_and_delivery_order():
+    readme = README.read_text()
+    assert "PNG, JPEG, or WebP" in readme
+    assert "2 MB" in readme
+    assert "uploads before the comment is posted" in readme
--- a/tests/test_issue_attachments.py
+++ b/tests/test_issue_attachments.py
@ -0,0 +1,256 @@
+import base64
+
+import httpx
+import pytest
+
+from src import gitea_proxy, main
+
+
+PNG_BYTES = b"\x89PNG\r\n\x1a\n" + b"mobile screenshot"
+
+
+@pytest.mark.anyio
+async def test_attachment_endpoint_uploads_valid_screenshot_to_assigned_issue(monkeypatch):
+    calls = []
+
+    async def upload(repository, number, filename, content_type, content):
+        calls.append((repository, number, filename, content_type, content))
+        return {
+            "name": "checkout.png",
+            "url": "https://forge.example/attachments/checkout.png",
+            "size": len(content),
+        }
+
+    monkeypatch.setattr(
+        main.gitea_proxy, "upload_assigned_issue_attachment", upload, raising=False
+    )
+    transport = httpx.ASGITransport(app=main.app)
+    async with httpx.AsyncClient(transport=transport, base_url="http://test") as client:
+        response = await client.post(
+            "/api/v1/repos/stackchain/api/issues/17/attachments",
+            json={
+                "filename": "checkout.png",
+                "content_type": "image/png",
+                "data": base64.b64encode(PNG_BYTES).decode("ascii"),
+            },
+        )
+
+    assert response.status_code == 201
+    assert response.headers["cache-control"] == "no-store"
+    assert response.json() == {
+        "name": "checkout.png",
+        "url": "https://forge.example/attachments/checkout.png",
+        "size": len(PNG_BYTES),
+        "markdown": "![checkout.png](<https://forge.example/attachments/checkout.png>)",
+    }
+    assert calls == [
+        ("stackchain/api", 17, "checkout.png", "image/png", PNG_BYTES)
+    ]
+
+
+@pytest.mark.anyio
+async def test_attachment_endpoint_admits_a_normal_phone_screenshot(monkeypatch):
+    screenshot = b"\x89PNG\r\n\x1a\n" + (b"x" * (100 * 1024))
+
+    async def upload(_repository, _number, filename, _content_type, content):
+        return {
+            "name": filename,
+            "url": "https://forge.example/attachments/screen.png",
+            "size": len(content),
+        }
+
+    monkeypatch.setattr(
+        main.gitea_proxy, "upload_assigned_issue_attachment", upload, raising=False
+    )
+    transport = httpx.ASGITransport(app=main.app)
+    async with httpx.AsyncClient(transport=transport, base_url="http://test") as client:
+        response = await client.post(
+            "/api/v1/repos/stackchain/api/issues/17/attachments",
+            json={
+                "filename": "screen.png",
+                "content_type": "image/png",
+                "data": base64.b64encode(screenshot).decode("ascii"),
+            },
+        )
+
+    assert response.status_code == 201
+    assert response.json()["size"] == len(screenshot)
+
+
+@pytest.mark.anyio
+async def test_attachment_endpoint_rejects_spoofed_image_before_upstream(monkeypatch):
+    called = False
+
+    async def upload(*_args):
+        nonlocal called
+        called = True
+
+    monkeypatch.setattr(
+        main.gitea_proxy, "upload_assigned_issue_attachment", upload, raising=False
+    )
+    transport = httpx.ASGITransport(app=main.app)
+    async with httpx.AsyncClient(transport=transport, base_url="http://test") as client:
+        response = await client.post(
+            "/api/v1/repos/stackchain/api/issues/17/attachments",
+            json={
+                "filename": "not-really.png",
+                "content_type": "image/png",
+                "data": base64.b64encode(b"<script>alert(1)</script>").decode("ascii"),
+            },
+        )
+
+    assert response.status_code == 422
+    assert response.headers["cache-control"] == "no-store"
+    assert called is False
+
+
+@pytest.mark.anyio
+async def test_attachment_endpoint_rejects_image_over_two_megabytes_before_upstream(monkeypatch):
+    called = False
+
+    async def upload(*_args):
+        nonlocal called
+        called = True
+        return {"name": "large.png", "url": "https://forge.example/a", "size": 1}
+
+    monkeypatch.setattr(main.gitea_proxy, "upload_assigned_issue_attachment", upload)
+    oversized = b"\x89PNG\r\n\x1a\n" + b"x" * (2 * 1024 * 1024 - 7)
+    transport = httpx.ASGITransport(app=main.app)
+    async with httpx.AsyncClient(transport=transport, base_url="http://test") as client:
+        response = await client.post(
+            "/api/v1/repos/stackchain/api/issues/17/attachments",
+            json={
+                "filename": "large.png",
+                "content_type": "image/png",
+                "data": base64.b64encode(oversized).decode("ascii"),
+            },
+        )
+
+    assert len(oversized) == 2 * 1024 * 1024 + 1
+    assert response.status_code == 422
+    assert called is False
+
+
+@pytest.mark.anyio
+async def test_gitea_attachment_revalidates_assignment_and_sends_multipart():
+    requests = []
+
+    async def handler(request):
+        requests.append(request)
+        if request.url.path == "/api/v1/user":
+            return httpx.Response(200, json={"login": "timmy"})
+        if request.method == "GET":
+            return httpx.Response(200, json={
+                "state": "open", "pull_request": None,
+                "assignees": [{"login": "timmy"}],
+            })
+        return httpx.Response(201, json={
+            "id": 9,
+            "name": "checkout.png",
+            "size": len(PNG_BYTES),
+            "browser_download_url": "https://forge.example/attachments/checkout.png",
+        })
+
+    gitea_proxy.start_client(transport=httpx.MockTransport(handler))
+    try:
+        result = await gitea_proxy.upload_assigned_issue_attachment(
+            "stackchain/api", 17, "checkout.png", "image/png", PNG_BYTES
+        )
+    finally:
+        await gitea_proxy.stop_client()
+
+    assert [(request.method, request.url.path) for request in requests] == [
+        ("GET", "/api/v1/user"),
+        ("GET", "/api/v1/repos/stackchain/api/issues/17"),
+        ("POST", "/api/v1/repos/stackchain/api/issues/17/assets"),
+    ]
+    upload = requests[-1]
+    assert upload.url.params["name"] == "checkout.png"
+    assert "multipart/form-data" in upload.headers["content-type"]
+    assert b'name="attachment"; filename="checkout.png"' in upload.content
+    assert PNG_BYTES in upload.content
+    assert result == {
+        "name": "checkout.png",
+        "url": "https://forge.example/attachments/checkout.png",
+        "size": len(PNG_BYTES),
+    }
+
+
+@pytest.mark.anyio
+async def test_attachment_markdown_escapes_untrusted_confirmed_filename(monkeypatch):
+    async def upload(*_args):
+        return {
+            "name": "screen](not-an-image).png",
+            "url": "https://forge.example/attachments/a.png",
+            "size": len(PNG_BYTES),
+        }
+
+    monkeypatch.setattr(main.gitea_proxy, "upload_assigned_issue_attachment", upload)
+    transport = httpx.ASGITransport(app=main.app)
+    async with httpx.AsyncClient(transport=transport, base_url="http://test") as client:
+        response = await client.post(
+            "/api/v1/repos/stackchain/api/issues/17/attachments",
+            json={
+                "filename": "screen.png",
+                "content_type": "image/png",
+                "data": base64.b64encode(PNG_BYTES).decode("ascii"),
+            },
+        )
+
+    assert response.status_code == 201
+    assert response.json()["markdown"] == (
+        "![screen\\](not-an-image).png](<https://forge.example/attachments/a.png>)"
+    )
+
+
+@pytest.mark.anyio
+async def test_attachment_endpoint_hides_an_issue_that_is_no_longer_assigned(monkeypatch):
+    async def upload(*_args):
+        raise gitea_proxy.IssueNotAvailableError("not assigned")
+
+    monkeypatch.setattr(main.gitea_proxy, "upload_assigned_issue_attachment", upload)
+    transport = httpx.ASGITransport(app=main.app)
+    async with httpx.AsyncClient(transport=transport, base_url="http://test") as client:
+        response = await client.post(
+            "/api/v1/repos/stackchain/api/issues/17/attachments",
+            json={
+                "filename": "screen.png",
+                "content_type": "image/png",
+                "data": base64.b64encode(PNG_BYTES).decode("ascii"),
+            },
+        )
+
+    assert response.status_code == 404
+    assert response.headers["cache-control"] == "no-store"
+
+
+@pytest.mark.anyio
+async def test_attachment_endpoint_rejects_unsafe_or_mismatched_filename(monkeypatch):
+    called = False
+
+    async def upload(*_args):
+        nonlocal called
+        called = True
+
+    monkeypatch.setattr(main.gitea_proxy, "upload_assigned_issue_attachment", upload)
+    transport = httpx.ASGITransport(app=main.app)
+    async with httpx.AsyncClient(transport=transport, base_url="http://test") as client:
+        traversal = await client.post(
+            "/api/v1/repos/stackchain/api/issues/17/attachments",
+            json={
+                "filename": "../payload.png",
+                "content_type": "image/png",
+                "data": base64.b64encode(PNG_BYTES).decode("ascii"),
+            },
+        )
+        mismatch = await client.post(
+            "/api/v1/repos/stackchain/api/issues/17/attachments",
+            json={
+                "filename": "payload.html",
+                "content_type": "image/png",
+                "data": base64.b64encode(PNG_BYTES).decode("ascii"),
+            },
+        )
+
+    assert [traversal.status_code, mismatch.status_code] == [422, 422]
+    assert called is False
--- a/tests/test_request_boundary.py
+++ b/tests/test_request_boundary.py
@ -112,6 +112,13 @@ def test_request_limits_are_route_specific_and_cover_api_mutations():
        == 64 * 1024
    )
    assert main.request_body_limit("GET", "/api/v1/context") is None
+    assert (
+        main.request_body_limit(
+            "POST", "/api/v1/repos/stackchain/project/issues/17/attachments"
+        )
+        == 3 * 1024 * 1024
+    )
+    assert main.request_body_limit("POST", "/unrelated/attachments") is None
    assert main.request_body_limit("POST", "/unrelated") is None


--- a/tests/test_service_worker.py
+++ b/tests/test_service_worker.py
@ -437,6 +437,7 @@ def test_install_precaches_complete_subpath_scoped_app_shell():
        "/dashboard/static/later-picker.js",
        "/dashboard/static/pick-work.js",
        "/dashboard/static/conversation.js",
+        "/dashboard/static/issue-attachment.js",
        "/dashboard/static/issue-sheet.js",
        "/dashboard/static/create-issue-sheet.js",
        "/dashboard/static/create-and-start.js",