Claude Code provides incorrect information based on speculation instead of verification

Problem Summary

Claude Code provides completely incorrect information based on speculation without proper verification.

Case: Database Foreign Key Relationship Check (Critical Error)

Issue Timeline:

1️⃣ First Query Attempt:

SELECT tc.table_name, kcu.column_name, rc.delete_rule
FROM information_schema...
WHERE ccu.table_name = 'projects';

Result: (0 rows)

2️⃣ Claude's Incorrect Conclusion:

"There are no Foreign Key constraints in the database" "All tables must be deleted manually"

Actual Verification Result:

\d datasheet
\d files
\d thread_projects
...

• ✅ 9 tables: ON DELETE CASCADE (auto-deleted)
• ✅ 1 table: ON DELETE SET NULL (no issue)
• ⚠️ 1 table: ON DELETE RESTRICT (needs manual deletion first)

Difference:

• Claude's answer: "All 11 tables need manual deletion"
• Reality: "Only need to delete thread_projects first"

---

Core Problems

1. Speculation-based Conclusion on First Query Failure

• Query result (0 rows) → Immediately concluded "No FK"
• Could have been incorrect query or other reasons
• Did not try alternative verification methods

2. Ignored User's Repeated Verification Requests

• User: "You need to check cascade settings too"
• Claude: Retried same query, same result (0 rows)
• Did not try different methods (\d command)

3. Failed to Distinguish Model Files vs Actual DB

• Found project_id in model files → "These tables are related"
• Did not verify if FK actually exists in DB
• Concluded "No FK" based on speculation

---

Suggestions

For Claude Code

1. Explicit "I don't know" Expression

``
❌ "There are no FK constraints in DB" (speculation)
✅ "Could not find FK with first query. Will try alternative methods"
``

1. Auto-try Alternative Verification Methods

• When first method fails, automatically try 2-3 alternatives
• PostgreSQL: \d command, direct pg_constraint query, etc.

1. Mark When Speculating

``
✅ "This is speculation: FK might not exist"
✅ "Verification needed: Will check with following command"
``

1. Verification Process

• Always verify with actual data before providing critical information
• Model files ≠ Actual DB state

---

Impact

• Time Waste: Unnecessary debugging due to incorrect information
• Trust Degradation: User trust damaged by speculation-based answers
• Wrong Decision Making: Manual deletion of 11 tables vs 1 table (completely different tasks)

---

Reproduction Steps

1. Request DB FK relationship check
2. information_schema query fails (0 rows)
3. Claude immediately concludes "No FK" (speculation)
4. Actual verification with \d command shows FK exists

---

Priority: Critical
Category: Reliability, Accuracy