feat: add BPO1 and BPO2 hardfork support (#9)

* feat: add BPO1 and BPO2 hardfork support

Add BPO1 (Blob Parameter Only fork 1, EIP-7892) and BPO2 SpecId variants
between Osaka and Amsterdam, with corresponding blob fraction and max blob
count constants.

- Add `bpo1` and `bpo2` to `SpecId` enum (between osaka and amsterdam)
- Add `HardforkName.BPO1`/`BPO2` string constants
- Add `specIdFromString`/`specIdToString` mappings for BPO1/BPO2
- Add `BLOB_BASE_FEE_UPDATE_FRACTION_BPO1` (8346193) and `_BPO2` (11684671)
- Add `MAX_BLOB_NUMBER_PER_BLOCK_BPO1` (15) and `_BPO2` (21)
- Add `BLOB_BASE_FEE_UPDATE_FRACTION_CANCUN` alias for clarity
- Map bpo1/bpo2 to Osaka precompile set in `PrecompileSpecId`

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix: wire BPO1/BPO2 blob fractions into blobBaseFeeUpdateFraction

The new bpo1/bpo2 SpecId variants were added but blobBaseFeeUpdateFraction
only checked for Prague, returning 3,338,477 for all post-Prague forks
instead of the correct values.

Cascade the spec check to return the correct fraction per fork:
- BPO2+:  11,684,671 (BLOB_BASE_FEE_UPDATE_FRACTION_BPO2)
- BPO1+:   8,346,193 (BLOB_BASE_FEE_UPDATE_FRACTION_BPO1)
- Osaka+:  5,007,716 (BLOB_BASE_FEE_UPDATE_FRACTION_OSAKA, EIP-7691)
- Cancun+: 3,338,477 (BLOB_BASE_FEE_UPDATE_FRACTION_CANCUN)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix: activate EIP-7691 blob fraction at Prague instead of Osaka

BLOB_BASE_FEE_UPDATE_FRACTION_OSAKA (5007716) is renamed to
BLOB_BASE_FEE_UPDATE_FRACTION_PRAGUE since EIP-7691 activates at
Prague, not Osaka. The redundant Prague alias for the Cancun fraction
(3338477) is removed. blobBaseFeeUpdateFraction now branches on
.prague instead of .osaka.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Gabriel-Trintinalia

src/context/cfg.zig

@@ -39,8 +39,8 @@ pub const CfgEnv = struct {
     /// If this config is not set, the blob base fee update fraction will be set to the default value.
     /// See also [CfgEnv::blob_base_fee_update_fraction].
     ///
-    /// Default values for Cancun is [`primitives::eip4844::BLOB_BASE_FEE_UPDATE_FRACTION_CANCUN`]
-    /// and for Prague is [`primitives::eip4844::BLOB_BASE_FEE_UPDATE_FRACTION_PRAGUE`].
+    /// Default values: Cancun (3338477), Prague/Osaka (5007716), BPO1 (8346193), BPO2 (11684671).
+    /// See [`CfgEnv::blobBaseFeeUpdateFraction`] for the resolution logic.
     blob_base_fee_update_fraction: ?u64,
     /// Configures the gas limit cap for the transaction.
     ///
@@ -341,15 +341,21 @@ pub const CfgEnv = struct {
 
     /// Returns the blob base fee update fraction from [CfgEnv::blob_base_fee_update_fraction].
     ///
-    /// If this field is not set, return the default value for the spec.
-    ///
-    /// Default values for Cancun is [`primitives::eip4844::BLOB_BASE_FEE_UPDATE_FRACTION_CANCUN`]
-    /// and for Prague is [`primitives::eip4844::BLOB_BASE_FEE_UPDATE_FRACTION_PRAGUE`].
+    /// If this field is not set, the default is derived from the active spec:
+    /// - BPO2+:   11684671 (`BLOB_BASE_FEE_UPDATE_FRACTION_BPO2`)
+    /// - BPO1:    8346193 (`BLOB_BASE_FEE_UPDATE_FRACTION_BPO1`)
+    /// - Prague+:   5007716 (`BLOB_BASE_FEE_UPDATE_FRACTION_PRAGUE`, EIP-7691)
+    /// - Cancun:  3338477 (`BLOB_BASE_FEE_UPDATE_FRACTION_CANCUN`)
     pub fn blobBaseFeeUpdateFraction(self: CfgEnv) u64 {
-        return self.blob_base_fee_update_fraction orelse if (self.spec.isEnabledIn(primitives.SpecId.Prague))
-            primitives.BLOB_BASE_FEE_UPDATE_FRACTION_PRAGUE
-        else
-            primitives.BLOB_BASE_FEE_UPDATE_FRACTION_CANCUN;
+        return self.blob_base_fee_update_fraction orelse
+            if (self.spec.isEnabledIn(.bpo2))
+                primitives.BLOB_BASE_FEE_UPDATE_FRACTION_BPO2
+            else if (self.spec.isEnabledIn(.bpo1))
+                primitives.BLOB_BASE_FEE_UPDATE_FRACTION_BPO1
+            else if (self.spec.isEnabledIn(.prague))
+                primitives.BLOB_BASE_FEE_UPDATE_FRACTION_PRAGUE
+            else
+                primitives.BLOB_BASE_FEE_UPDATE_FRACTION_CANCUN;
     }
 
     pub fn chainId(self: CfgEnv) u64 {

src/precompile/main.zig

@@ -180,7 +180,7 @@ pub const PrecompileSpecId = enum {
             .berlin, .london, .arrow_glacier, .gray_glacier, .merge, .shanghai => .Berlin,
             .cancun => .Cancun,
             .prague => .Prague,
-            .osaka, .amsterdam => .Osaka,
+            .osaka, .bpo1, .bpo2, .amsterdam => .Osaka,
         };
     }
 };

src/primitives/main.zig

@@ -81,10 +81,14 @@ pub const STACK_LIMIT: usize = 1024;
 /// EVM call stack limit
 pub const CALL_STACK_LIMIT: u64 = 1024;
 
-/// Blob base fee update fraction for Prague hardfork
-pub const BLOB_BASE_FEE_UPDATE_FRACTION_PRAGUE: u64 = 3338477;
-/// Blob base fee update fraction for Osaka hardfork (EIP-7691)
-pub const BLOB_BASE_FEE_UPDATE_FRACTION_OSAKA: u64 = 5007716;
+/// Blob base fee update fraction for Cancun hardfork (EIP-4844)
+pub const BLOB_BASE_FEE_UPDATE_FRACTION_CANCUN: u64 = 3338477;
+/// Blob base fee update fraction for Prague/Osaka hardfork (EIP-7691)
+pub const BLOB_BASE_FEE_UPDATE_FRACTION_PRAGUE: u64 = 5007716;
+/// Blob base fee update fraction for BPO1 hardfork (EIP-7892)
+pub const BLOB_BASE_FEE_UPDATE_FRACTION_BPO1: u64 = 8346193;
+/// Blob base fee update fraction for BPO2/Amsterdam/Glamsterdam hardfork
+pub const BLOB_BASE_FEE_UPDATE_FRACTION_BPO2: u64 = 11684671;
 /// EIP-7918: blob base cost (2**13) used for reserve price calculation
 pub const BLOB_BASE_COST: u64 = 8192;
 
@@ -93,8 +97,12 @@ pub const GAS_PER_BLOB: u64 = 131_072;
 
 /// EIP-4844: maximum blobs per block (Cancun: 6, Prague+: 9 via EIP-7691)
 pub const MAX_BLOB_NUMBER_PER_BLOCK: usize = 6;
-/// EIP-7691: maximum blobs per block for Prague (9)
+/// EIP-7691: maximum blobs per block for Prague/Osaka (9)
 pub const MAX_BLOB_NUMBER_PER_BLOCK_PRAGUE: usize = 9;
+/// EIP-7892: maximum blobs per block for BPO1 (15)
+pub const MAX_BLOB_NUMBER_PER_BLOCK_BPO1: usize = 15;
+/// Maximum blobs per block for BPO2/Amsterdam/Glamsterdam (21)
+pub const MAX_BLOB_NUMBER_PER_BLOCK_BPO2: usize = 21;
 /// EIP-7594: maximum blobs per transaction for Osaka (6)
 pub const MAX_BLOB_NUMBER_PER_TX: usize = 6;
 
@@ -155,6 +163,10 @@ pub const SpecId = enum(u8) {
     prague,
     /// Osaka hard fork - Activated at block TBD
     osaka,
+    /// BPO1 hard fork - Blob Parameter Only fork 1 (EIP-7892)
+    bpo1,
+    /// BPO2 hard fork - Blob Parameter Only fork 2
+    bpo2,
     /// Amsterdam hard fork - Activated at block TBD
     amsterdam,
 };
@@ -191,6 +203,8 @@ pub const HardforkName = struct {
     pub const CANCUN = "Cancun";
     pub const PRAGUE = "Prague";
     pub const OSAKA = "Osaka";
+    pub const BPO1 = "BPO1";
+    pub const BPO2 = "BPO2";
     pub const AMSTERDAM = "Amsterdam";
     pub const LATEST = "Latest";
 };
@@ -220,6 +234,8 @@ pub fn specIdFromString(s: []const u8) UnknownHardfork!SpecId {
     if (std.mem.eql(u8, s, HardforkName.CANCUN)) return .cancun;
     if (std.mem.eql(u8, s, HardforkName.PRAGUE)) return .prague;
     if (std.mem.eql(u8, s, HardforkName.OSAKA)) return .osaka;
+    if (std.mem.eql(u8, s, HardforkName.BPO1)) return .bpo1;
+    if (std.mem.eql(u8, s, HardforkName.BPO2)) return .bpo2;
     if (std.mem.eql(u8, s, HardforkName.AMSTERDAM)) return .amsterdam;
     return UnknownHardfork.UnknownHardfork;
 }
@@ -247,6 +263,8 @@ pub fn specIdToString(spec_id: SpecId) []const u8 {
         .cancun => HardforkName.CANCUN,
         .prague => HardforkName.PRAGUE,
         .osaka => HardforkName.OSAKA,
+        .bpo1 => HardforkName.BPO1,
+        .bpo2 => HardforkName.BPO2,
         .amsterdam => HardforkName.AMSTERDAM,
     };
 }