Add v0.4 evolutionary specification example to gh-pages

- Add examples/evolution.simplex demonstrating BASELINE and EVAL
- Update examples.html with evolution example card
- Add Key Observations section explaining evolutionary specs
- Update description to reflect 15 landmarks (was 13)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: Bran H

examples.html

@@ -2,7 +2,7 @@
 layout: default
 title: Examples
 permalink: /examples/
-description: Simplex specification examples demonstrating authentication, shopping carts, document pipelines, and multi-agent coordination with all 13 landmarks.
+description: Simplex specification examples demonstrating authentication, shopping carts, document pipelines, evolutionary specifications, and multi-agent coordination with all 15 landmarks.
 ---
 
 <div class="spec-content">
@@ -209,6 +209,72 @@ <h3>Document Pipeline</h3>
   - on failure: error details with document path for retry queue</code></pre>
 </div>
 
+<div class="example-card">
+  <div class="example-card-header">
+    <h3>Evolutionary Specification</h3>
+    <p>Modernizing existing systems with BASELINE and EVAL (v0.4)</p>
+  </div>
+  <pre><code>DATA: AuthSystem
+  session_support: boolean
+  jwt_support: boolean
+  refresh_rotation: boolean
+  rate_limiting: boolean
+
+FUNCTION: modernize_authentication(config) → AuthSystem
+
+BASELINE:
+  reference: "session-based auth, commit abc123"
+  preserve:
+    - POST /login returns { session_id, expires_at }
+    - session timeout is 30 minutes
+    - existing client SDKs continue to work
+  evolve:
+    - add JWT token issuance alongside sessions
+    - implement refresh token rotation
+    - add rate limiting on auth endpoints
+
+RULES:
+  - authenticate user credentials against user store
+  - issue JWT token with configurable expiration
+  - issue refresh token that rotates on each use
+  - maintain session-based auth for backward compatibility
+  - rate limit failed attempts per IP address
+
+DONE_WHEN:
+  - valid credentials produce both session and JWT
+  - refresh tokens rotate correctly
+  - rate limiting activates after threshold
+  - existing session-based clients unaffected
+
+EXAMPLES:
+  # Preserved behaviors (regression tests)
+  (valid_creds, session_mode)
+    → { session_id: "...", expires_at: +30min }
+  (invalid_creds, any_mode)
+    → { error: "unauthorized" }
+
+  # Evolved capabilities (capability tests)
+  (valid_creds, jwt_mode)
+    → { token: "...", refresh: "...", expires_at: +1hr }
+  (expired_token, valid_refresh)
+    → { token: "new...", refresh: "new..." }
+  (any_creds, after_rate_limit)
+    → { error: "rate limited", retry_after: 60 }
+
+ERRORS:
+  - user store unavailable → "auth service unavailable"
+  - malformed credentials → "invalid request format"
+  - rate limit exceeded → "rate limited, retry after {seconds}"
+
+EVAL:
+  preserve: pass^3
+  evolve: pass@5
+  grading: code
+
+CONSTRAINT: backward_compatibility
+  existing v1 API clients must work without modification</code></pre>
+</div>
+
 </div>
 
 <h2 style="margin-top: 3rem;">Key Observations</h2>
@@ -257,4 +323,27 @@ <h3>Swarm Coordination</h3>
   enabling agents to coordinate without central orchestration.
 </p>
 
+<h3>Evolutionary Specifications (v0.4)</h3>
+<p>
+  When evolving existing systems rather than building greenfield, use <code>BASELINE</code>
+  and <code>EVAL</code> to declare what must be preserved versus what is being evolved.
+</p>
+<p>
+  <code>BASELINE</code> contains three fields: <code>reference</code> (the prior state),
+  <code>preserve</code> (behaviors that must not regress), and <code>evolve</code>
+  (capabilities being added or changed).
+</p>
+<p>
+  <code>EVAL</code> declares how to measure success using two threshold notations:
+  <code>pass^k</code> means all k trials must pass (for regression tests), while
+  <code>pass@k</code> means at least one of k trials must pass (for capability tests).
+  The <code>grading</code> field specifies evaluation approach: <code>code</code> for
+  deterministic comparison, <code>model</code> for LLM-as-judge, or <code>outcome</code>
+  for verifying state changes.
+</p>
+<p>
+  EVAL is required when BASELINE is present. This ensures evolutionary specs always
+  define how preservation and progress are measured.
+</p>
+
 </div>

examples/evolution.simplex

@@ -0,0 +1,54 @@
+DATA: AuthSystem
+  session_support: boolean
+  jwt_support: boolean
+  refresh_rotation: boolean
+  rate_limiting: boolean
+
+FUNCTION: modernize_authentication(config) → AuthSystem
+
+BASELINE:
+  reference: "session-based auth, commit abc123"
+  preserve:
+    - POST /login returns { session_id, expires_at }
+    - session timeout is 30 minutes
+    - existing client SDKs continue to work
+  evolve:
+    - add JWT token issuance alongside sessions
+    - implement refresh token rotation
+    - add rate limiting on auth endpoints
+
+RULES:
+  - authenticate user credentials against user store
+  - issue JWT token with configurable expiration
+  - issue refresh token that rotates on each use
+  - maintain session-based auth for backward compatibility
+  - rate limit failed attempts per IP address
+
+DONE_WHEN:
+  - valid credentials produce both session and JWT
+  - refresh tokens rotate correctly
+  - rate limiting activates after threshold
+  - existing session-based clients unaffected
+
+EXAMPLES:
+  # Preserved behaviors (regression tests)
+  (valid_creds, session_mode) → { session_id: "...", expires_at: +30min }
+  (invalid_creds, any_mode) → { error: "unauthorized" }
+
+  # Evolved capabilities (capability tests)
+  (valid_creds, jwt_mode) → { token: "...", refresh: "...", expires_at: +1hr }
+  (expired_token, valid_refresh) → { token: "new...", refresh: "new..." }
+  (any_creds, after_rate_limit) → { error: "rate limited", retry_after: 60 }
+
+ERRORS:
+  - user store unavailable → "auth service unavailable"
+  - malformed credentials → "invalid request format"
+  - rate limit exceeded → "rate limited, retry after {seconds}"
+
+EVAL:
+  preserve: pass^3
+  evolve: pass@5
+  grading: code
+
+CONSTRAINT: backward_compatibility
+  existing v1 API clients must work without modification