diff --git a/.github/workflows/similar-issues.yml b/.github/workflows/similar-issues.yml
index c3f1da19f..ab96a6ca2 100644
--- a/.github/workflows/similar-issues.yml
+++ b/.github/workflows/similar-issues.yml
@@ -1,91 +1,73 @@
-name: Similar Issues via AI MCP
+name: duplicate-issues
 
 on:
-    issues:
-        types: [opened]
+  issues:
+    types: [opened]
+  workflow_dispatch:
+    inputs:
+      issue_number:
+        description: Issue number to check manually
+        required: true
+        type: number
 
 jobs:
-    find-similar:
-        permissions:
-            contents: read
-            issues: write
-            models: read
-        runs-on: ubuntu-slim
-        steps:
-            - name: Check out repository
-              uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+  check-duplicates:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      issues: write
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 1
 
-            - name: Prepare prompt variables
-              id: prepare_input
-              uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd # v8.0.0
-              with:
-                  script: |
-                      const issue = context.payload.issue || {};
-                      const title = issue.title || '';
-                      const body = issue.body || '';
-                      const indent = '      ';
-                      // Indent subsequent lines so YAML block scalar indentation remains valid
-                      const bodyIndented = body.replace(/\n/g, '\n' + indent);
-                      core.setOutput('issue_title_json', JSON.stringify(title));
-                      core.setOutput('issue_body_indented_json', JSON.stringify(bodyIndented));
-                      core.setOutput('issue_number', issue.number);
+      - name: Set up Bun
+        uses: oven-sh/setup-bun@v2
 
-            - name: Find similar issues with AI (MCP)
-              id: inference
-              uses: actions/ai-inference@a380166897b5408b8fb7dddd148142794cb5624a # v2.0.6
-              with:
-                  prompt-file: ./.github/prompts/similar_issues.prompt.yml
-                  input: |
-                      issue_title: ${{ steps.prepare_input.outputs.issue_title_json }}
-                      issue_body: ${{ steps.prepare_input.outputs.issue_body_indented_json }}
-                      issue_number: ${{ steps.prepare_input.outputs.issue_number }}
-                      repository: ${{ github.repository }}
-                  enable-github-mcp: true
-                  # Inference token can use GITHUB_TOKEN. MCP specifically requires a PAT.
-                  token: ${{ secrets.GITHUB_TOKEN }}
-                  github-mcp-token: ${{ secrets.USER_PAT }}
-                  max-tokens: 8000
+      - name: Install opencode
+        run: curl -fsSL https://opencode.ai/install | bash
 
-            - name: Prepare comment body
-              id: prepare
-              uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd # v8.0.0
-              env:
-                  AI_RESPONSE: ${{ steps.inference.outputs.response }}
-              with:
-                  script: |
-                      let data;
-                      try {
-                        data = JSON.parse(process.env.AI_RESPONSE || '{}');
-                      } catch (e) {
-                        core.setOutput('has_matches', 'false');
-                        return;
-                      }
-                      const matches = Array.isArray(data.matches) ? data.matches.filter(m => m.number !== context.payload.issue.number) : [];
-                      if (!matches.length) {
-                        core.setOutput('has_matches', 'false');
-                        return;
-                      }
-                      const lines = [];
-                      lines.push('I found similar issues that might help:');
-                      for (const m of matches.slice(0, 3)) {
-                        const num = m.number != null ? `#${m.number}` : '';
-                        const title = m.title || 'Untitled';
-                        const url = m.url || '';
-                        const score = typeof m.similarity_score === 'number' ? ` (similarity: ${m.similarity_score.toFixed(2)})` : '';
-                        lines.push(`- ${url}${score}`.trim());
-                      }
-                      core.setOutput('has_matches', 'true');
-                      core.setOutput('comment_body', lines.join('\n'));
+      - name: Check for duplicate issues
+        env:
+          OPENCODE_API_KEY: ${{ secrets.OPENCODE_API_KEY }}
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          ISSUE_NUMBER: ${{ github.event.issue.number || inputs.issue_number }}
+          OPENCODE_PERMISSION: |
+            {
+              "bash": {
+                "*": "deny",
+                "gh issue*": "allow"
+              },
+              "webfetch": "deny"
+            }
+        run: |
+          if [ -z "$ISSUE_NUMBER" ]; then
+            echo "issue_number is required"
+            exit 1
+          fi
 
-            - name: Comment similar issues
-              if: steps.prepare.outputs.has_matches == 'true'
-              uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd # v8.0.0
-              with:
-                  script: |
-                      const body = ${{ toJson(steps.prepare.outputs.comment_body) }};
-                      await github.rest.issues.createComment({
-                        owner: context.repo.owner,
-                        repo: context.repo.repo,
-                        issue_number: context.payload.issue.number,
-                        body
-                      });
+          opencode run -m ${{ vars.OPENCODE_MODEL }} "A new issue has been created:'
+
+          Issue number:
+          $ISSUE_NUMBER
+
+          Lookup this issue and search through existing issues (excluding #$ISSUE_NUMBER) in this repository to find any potential duplicates of this new issue.
+          Consider:
+          1. Similar titles or descriptions
+          2. Same error messages or symptoms
+          3. Related functionality or components
+          4. Similar feature requests
+
+          If you find any potential duplicates, please comment on the new issue with:
+          - A brief explanation of why it might be a duplicate
+          - Links to the potentially duplicate issues
+          - A suggestion to check those issues first
+
+          Use this format for the comment:
+          'This issue might be a duplicate of existing issues. Please check:
+          - #[issue_number]: [brief description of similarity]
+
+          Feel free to ignore if none of these address your specific case.'
+
+          If no clear duplicates are found, do not comment."