evalbuff: add patterns/task-completion-validation.md (fde408c)

Author: jahooma

AGENTS.md

@@ -43,3 +43,4 @@ Make an efficient learning agent that can do anything.
 - [`docs/agents-and-tools.md`](docs/agents-and-tools.md) — Agent system, shell shims, tool definitions
 - [`docs/patterns/handle-steps-generators.md`](docs/patterns/handle-steps-generators.md) — handleSteps generator patterns and spawn_agents tool calls
 - [docs/evalbuff/interpreting-task-prompts.md](docs/evalbuff/interpreting-task-prompts.md)
+- [docs/patterns/task-completion-validation.md](docs/patterns/task-completion-validation.md)

docs/patterns/task-completion-validation.md

@@ -0,0 +1,130 @@
+# Task Completion Validation Pattern
+
+When implementing features, always validate whether the requested functionality already exists before making changes. Many tasks may already be complete or partially implemented.
+
+## The Validation Process
+
+### 1. Search for Existing Implementation
+
+Before implementing any feature, search the codebase for existing implementations:
+
+```bash
+# Search for relevant patterns
+code_search "pattern related to feature"
+# Check configuration files
+read_files ["config-file.js", "next.config.mjs"]
+```
+
+### 2. Verify Implementation Completeness
+
+When you find existing code, verify it matches the requirements:
+
+- **Check the exact pattern**: Does `/b/:hash` match the requested route?
+- **Verify the destination**: Does `https://go.trybeluga.ai/:hash` match the target?
+- **Confirm the behavior**: Is `permanent: false` the correct redirect type?
+
+### 3. Test the Implementation
+
+If implementation exists, verify it works:
+
+```bash
+# Look for existing tests
+code_search "test.*redirect.*b/"
+# Run relevant tests if they exist
+run_terminal_command "bun test path/to/redirect/tests"
+```
+
+### 4. Communicate Task Status Clearly
+
+Always provide explicit feedback about task completion:
+
+**✅ When feature is already implemented:**
+```
+The redirect for /b/:hash is already implemented in next.config.mjs:
+
+[show the relevant code]
+
+This configuration:
+- Redirects /b/:hash to https://go.trybeluga.ai/:hash
+- Uses temporary redirects (permanent: false)
+- Preserves query parameters
+
+No additional changes needed - the feature is complete!
+```
+
+**✅ When making changes:**
+```
+I need to add the redirect configuration to next.config.mjs:
+
+[show the changes being made]
+
+This will enable the requested /b/:hash → go.trybeluga.ai functionality.
+```
+
+## Common Scenarios
+
+### Next.js Redirects
+
+For Next.js redirect tasks, always check `next.config.mjs` first:
+
+```javascript
+// Look for existing redirects() function
+async redirects() {
+  return [
+    {
+      source: '/pattern',
+      destination: 'https://target.com/pattern',
+      permanent: false,
+    },
+  ]
+}
+```
+
+### API Routes
+
+For API endpoint tasks, check existing route files:
+
+```bash
+# Check if route already exists
+list_directory "src/app/api/target-path"
+read_files ["src/app/api/target-path/route.ts"]
+```
+
+### Component Features
+
+For UI feature tasks, search for existing components:
+
+```bash
+code_search "component.*feature.*name"
+glob "**/*ComponentName*"
+```
+
+## Anti-Patterns to Avoid
+
+❌ **Silent failure**: Making no changes without explanation
+❌ **Duplicate implementation**: Adding code when it already exists
+❌ **Incomplete verification**: Finding partial implementation but not checking if it's complete
+❌ **No status communication**: Leaving the user unsure whether the task succeeded
+
+## Test Validation
+
+When tests exist for the feature:
+
+1. **Read the test file** to understand expected behavior
+2. **Run the tests** to verify current implementation works
+3. **Report test results** as evidence of completion
+
+Example from redirect tests:
+```typescript
+test('redirects to go.trybeluga.ai with the hash', async ({ request }) => {
+  const response = await request.get('/b/test123', { maxRedirects: 0 })
+  expect(response.status()).toBe(307)
+  expect(response.headers()['location']).toBe('https://go.trybeluga.ai/test123')
+})
+```
+
+If these tests exist and pass, the feature is confirmed working.
+
+## Key Principle
+
+**Always explicitly state whether a task is complete, incomplete, or already done.** Never leave the user guessing about the status of their request.