diff --git a/.opencode/agents/ca-test-infra-improver.md b/.opencode/agents/ca-test-infra-improver.md
index e4dc21936..eedcac656 100644
--- a/.opencode/agents/ca-test-infra-improver.md
+++ b/.opencode/agents/ca-test-infra-improver.md
@@ -335,10 +335,38 @@ For each finding, invoke `ca-new-issue-creator` with:
 
 ### Duplicate Avoidance
 
-Before filing any issue:
-1. Search Forgejo for existing issues with "TEST-INFRA:" prefix
-2. Check for similar titles/descriptions
-3. If potential duplicate found, skip
+**CRITICAL: Duplicate issue creation is the #1 problem with this agent.**
+Previous sessions created 48+ TEST-INFRA issues with massive duplication
+(6 issues about "dependency caching", 7 about "matrix builds", 5 about
+"parallelize CI jobs", etc.). You MUST follow this procedure rigorously.
+
+Before filing ANY issue, you MUST perform ALL of these checks:
+
+1. **Mandatory keyword search.** Extract the 2-3 key nouns from your
+   proposed issue title (e.g., for "Implement dependency caching in CI",
+   search for "dependency caching", "cache", "caching"). Search Forgejo
+   for ALL open AND closed issues containing these keywords. If ANY issue
+   with overlapping keywords exists (regardless of prefix or area), do
+   NOT file a new issue.
+
+2. **Cross-area search.** Search WITHOUT the "TEST-INFRA:" prefix and
+   without the area tag (e.g., search for "dependency caching" not just
+   "TEST-INFRA: [ci-pipeline-design] dependency caching"). Other agents
+   or humans may have filed the same issue under a different prefix.
+
+3. **Include closed issues in search.** A closed duplicate means the topic
+   has already been addressed or intentionally rejected. Do NOT re-file it.
+
+4. **Dedup proof in issue body.** Every issue you file MUST include a
+   "### Duplicate Check" section in the body listing:
+   - The search queries you used
+   - The number of results found for each query
+   - Why none of the existing issues cover this specific finding
+   This makes dedup auditable and prevents future duplicates.
+
+5. **If uncertain, do NOT file.** When in doubt about whether an issue is
+   a duplicate, skip it. It is far better to miss a marginal finding than
+   to create another duplicate that wastes human review time.
 
 ---