fix(pricing): refresh full DeepSeek snapshot to 2026-07 rates

Widens the deepseek-v4-flash addition to the whole stale-snapshot class:
- deepseek-v4-pro: $1.74/$3.48 → $0.435/$0.87, cache-read $0.003625
  (DeepSeek's 2026-07 price cut; every pro session was over-reporting 4x)
- deepseek-chat / deepseek-reasoner: deprecated 2026-07-24, now alias
  v4-flash non-thinking/thinking modes — repriced to match flash
  (reasoner was $0.55/$2.19 with no cache rate)
- cache_read added to every row; pricing_version unified at
  deepseek-pricing-2026-07
- invariant tests: aliases price identically to flash; every deepseek
  row carries cache_read < input

agent/usage_pricing.py

@@ -446,36 +446,41 @@ _OFFICIAL_DOCS_PRICING: Dict[tuple[str, str], PricingEntry] = {
         pricing_version="anthropic-pricing-2026-05",
     ),
     # DeepSeek
+    # Snapshot of https://api-docs.deepseek.com/quick_start/pricing (2026-07).
+    # deepseek-chat / deepseek-reasoner are deprecated 2026-07-24 and now alias
+    # deepseek-v4-flash's non-thinking / thinking modes — same rates.
     (
         "deepseek",
         "deepseek-chat",
     ): PricingEntry(
         input_cost_per_million=Decimal("0.14"),
         output_cost_per_million=Decimal("0.28"),
+        cache_read_cost_per_million=Decimal("0.0028"),
         source="official_docs_snapshot",
         source_url="https://api-docs.deepseek.com/quick_start/pricing",
-        pricing_version="deepseek-pricing-2026-03-16",
+        pricing_version="deepseek-pricing-2026-07",
     ),
     (
         "deepseek",
         "deepseek-reasoner",
     ): PricingEntry(
-        input_cost_per_million=Decimal("0.55"),
-        output_cost_per_million=Decimal("2.19"),
+        input_cost_per_million=Decimal("0.14"),
+        output_cost_per_million=Decimal("0.28"),
+        cache_read_cost_per_million=Decimal("0.0028"),
         source="official_docs_snapshot",
         source_url="https://api-docs.deepseek.com/quick_start/pricing",
-        pricing_version="deepseek-pricing-2026-03-16",
+        pricing_version="deepseek-pricing-2026-07",
     ),
     (
         "deepseek",
         "deepseek-v4-pro",
     ): PricingEntry(
-        input_cost_per_million=Decimal("1.74"),
-        output_cost_per_million=Decimal("3.48"),
-        cache_read_cost_per_million=Decimal("0.0145"),
+        input_cost_per_million=Decimal("0.435"),
+        output_cost_per_million=Decimal("0.87"),
+        cache_read_cost_per_million=Decimal("0.003625"),
         source="official_docs_snapshot",
         source_url="https://api-docs.deepseek.com/quick_start/pricing",
-        pricing_version="deepseek-pricing-2026-05-12",
+        pricing_version="deepseek-pricing-2026-07",
     ),
     (
         "deepseek",
@@ -486,7 +491,7 @@ _OFFICIAL_DOCS_PRICING: Dict[tuple[str, str], PricingEntry] = {
         cache_read_cost_per_million=Decimal("0.0028"),
         source="official_docs_snapshot",
         source_url="https://api-docs.deepseek.com/quick_start/pricing",
-        pricing_version="deepseek-pricing-2026-05-12",
+        pricing_version="deepseek-pricing-2026-07",
     ),
     # Google Gemini
     (

tests/agent/test_usage_pricing.py

@@ -223,7 +223,8 @@ def test_deepseek_v4_pro_pricing_entry_exists():
 
     Before this fix, deepseek-v4-pro sessions showed as unknown cost
     in hermes insights because the _OFFICIAL_DOCS_PRICING table had no
-    entry for that model.  See #24218.
+    entry for that model.  See #24218.  Rates track the 2026-07 price cut
+    ($1.74/$3.48 → $0.435/$0.87).
     """
     entry = get_pricing_entry(
         "deepseek-v4-pro",
@@ -233,9 +234,9 @@ def test_deepseek_v4_pro_pricing_entry_exists():
     assert entry is not None
     assert entry.input_cost_per_million is not None
     assert entry.output_cost_per_million is not None
-    assert float(entry.input_cost_per_million) == 1.74
-    assert float(entry.output_cost_per_million) == 3.48
-    assert float(entry.cache_read_cost_per_million) == 0.0145
+    assert float(entry.input_cost_per_million) == 0.435
+    assert float(entry.output_cost_per_million) == 0.87
+    assert float(entry.cache_read_cost_per_million) == 0.003625
 
 
 def test_deepseek_v4_pro_estimate_usage_cost():
@@ -248,8 +249,39 @@ def test_deepseek_v4_pro_estimate_usage_cost():
 
     assert result.status == "estimated"
     assert result.amount_usd is not None
-    # 1M input × $1.74/M + 500K output × $3.48/M = $1.74 + $1.74 = $3.48
-    assert float(result.amount_usd) == 3.48
+    # 1M input × $0.435/M + 500K output × $0.87/M = $0.435 + $0.435 = $0.87
+    assert float(result.amount_usd) == 0.87
+
+
+def test_deepseek_deprecated_aliases_price_as_v4_flash():
+    """Invariant: deepseek-chat / deepseek-reasoner are deprecated aliases for
+    deepseek-v4-flash's non-thinking / thinking modes (deprecation 2026-07-24)
+    — they must bill at identical rates to the flash entry, or sessions on the
+    legacy names over/under-report cost."""
+    flash = get_pricing_entry("deepseek-v4-flash", provider="deepseek")
+    assert flash is not None
+    for alias in ("deepseek-chat", "deepseek-reasoner"):
+        entry = get_pricing_entry(alias, provider="deepseek")
+        assert entry is not None, alias
+        assert entry.input_cost_per_million == flash.input_cost_per_million, alias
+        assert entry.output_cost_per_million == flash.output_cost_per_million, alias
+        assert (
+            entry.cache_read_cost_per_million == flash.cache_read_cost_per_million
+        ), alias
+
+
+def test_deepseek_rows_all_carry_cache_read_pricing():
+    """Invariant: DeepSeek publishes a cache-hit rate for every current model;
+    every deepseek snapshot row must carry cache_read < input so cached
+    sessions estimate correctly instead of billing reads at full price."""
+    from agent.usage_pricing import _OFFICIAL_DOCS_PRICING
+
+    ds_rows = [k for k in _OFFICIAL_DOCS_PRICING if k[0] == "deepseek"]
+    assert ds_rows, "expected at least one deepseek pricing row"
+    for key in ds_rows:
+        entry = _OFFICIAL_DOCS_PRICING[key]
+        assert entry.cache_read_cost_per_million is not None, key
+        assert entry.cache_read_cost_per_million < entry.input_cost_per_million, key
 
 
 def test_bedrock_claude_rows_all_carry_cache_pricing():