Fix fuel implementation in PHP

AGENTS.md

@@ -2,7 +2,7 @@
 
 > For AI agents and contributors working in this repository.
 
-## 0. TDD
+## 0. Test Driven Development
 
 Write and discuss tests with the user before implementing any implementation code.
 
@@ -178,27 +178,7 @@ tricu/
 └── AGENTS.md           # This file
 ```
 
-## 9. JS Arboricx Runtime
-
-A JavaScript implementation of the Arboricx portable bundle runtime lives in `ext/js/`.
-It is a reference implementation — not a tricu source parser. It reads `.arboricx` files produced by the Haskell toolchain, verifies Merkle node hashes, reconstructs tree values, and reduces them.
-
-From project root:
-```bash
-node ext/js/src/cli.js inspect test/fixtures/id.arboricx
-node ext/js/src/cli.js run test/fixtures/true.arboricx
-```
-
-The JS runtime implements:
-- Bundle binary format parsing (header, section directory, manifest, nodes)
-- SHA-256 Merkle node hash verification against canonical payloads
-- Closure verification (all child references present)
-- Tree reconstruction from node DAG
-- Core `apply` reduction rules
-- Basic codecs (decodeResult)
-- CLI: `inspect` and `run` commands
-
-## 10. Content Store Workflow (Custom DB)
+## 9. Content Store Workflow (Custom DB)
 
 The content store location is controlled by the `TRICU_DB_PATH` environment variable. When set, `eval` mode automatically loads all stored terms into the initial environment, so you can call any previously imported/evaluated term by name.
 
@@ -226,14 +206,14 @@ t> !definitions
 
 Without `TRICU_DB_PATH` set, `eval` uses only the terms defined in the input file(s).
 
-## 11. Development Tips
+## 10. Development Tips
 
 - **REPL:** `nix run .#` starts the interactive tricu REPL.
 - **Evaluate files:** `nix run .# -- eval -f demos/equality.tri`
 - **GHC options:** `-threaded -rtsopts -with-rtsopts=-N` for parallel runtime. Use `-N` RTS flag for multi-core.
 - **Upx** is in the devShell for binary compression if needed.
 
-## 12. Viewing Haskell Dependency Docs from Nix
+## 11. Viewing Haskell Dependency Docs from Nix
 
 When you need Haddock documentation for a Haskell dependency available in Nixpkgs, build the package's `doc` output directly with `^doc`.
 

ext/php/run.php

@@ -87,7 +87,7 @@ function cmdRun(string $bundlePath, array $args): void
     debugTime('built expression');
 
     fwrite(STDERR, "Reducing kernel application...\n");
-    $result = reduce($expr, 1_000_000);
+    $result = reduce($expr, 1_000_000_000);
     debugTime('reduced kernel application');
 
     [$kind, $value, $rest] = unwrapResult($result);

ext/php/src/functions.php

@@ -21,6 +21,14 @@ $GLOBALS['ARB_B']   = [0 => 0];
 $GLOBALS['ARB_NEXT'] = 1;
 $GLOBALS['ARB_CONS_CACHE'] = [];
 
+function spendFuel(int &$fuel): void
+{
+    if ($fuel <= 0) {
+        throw new \RuntimeException('fuel exhausted');
+    }
+    $fuel--;
+}
+
 function newNode(int $tag, int $a, int $b = 0): int
 {
     $id = $GLOBALS['ARB_NEXT']++;
@@ -100,12 +108,12 @@ function newAppFast(int $f, int $x, array &$TAG, array &$A, array &$B): int
     return $id;
 }
 
-function apply_(int $a, int $b, int $fuel = 1_000_000): int
+function apply_(int $a, int $b, int $fuel = 100_000_000_000_000_000): int
 {
     return reduce(app($a, $b), $fuel);
 }
 
-function reduce(int $term, int $fuel = 1_000_000): int
+function reduce(int $term, int $fuel = 100_000_000_000_000_000): int
 {
     return whnf($term, $fuel);
 }
@@ -167,6 +175,7 @@ function whnf(int $term, int &$fuel): int
         if ($left === 0) {
             $term = $right;
             if ($orig !== $term) { $TAG[$orig] = 4; $A[$orig] = $term; $B[$orig] = 0; }
+						spendFuel($fuel);
             continue;
         }
 
@@ -178,6 +187,7 @@ function whnf(int $term, int &$fuel): int
                 $TAG, $A, $B
             );
             if ($orig !== $term) { $TAG[$orig] = 4; $A[$orig] = $term; $B[$orig] = 0; }
+						spendFuel($fuel);
             continue;
         }
 
@@ -195,6 +205,7 @@ function whnf(int $term, int &$fuel): int
         if ($arg === 0) {
             $term = $A[$left];
             if ($orig !== $term) { $TAG[$orig] = 4; $A[$orig] = $term; $B[$orig] = 0; }
+						spendFuel($fuel);
             continue;
         }
 
@@ -202,6 +213,7 @@ function whnf(int $term, int &$fuel): int
         if ($atag === 1) {
             $term = newAppFast($B[$left], $A[$arg], $TAG, $A, $B);
             if ($orig !== $term) { $TAG[$orig] = 4; $A[$orig] = $term; $B[$orig] = 0; }
+						spendFuel($fuel);
             continue;
         }
 
@@ -213,6 +225,7 @@ function whnf(int $term, int &$fuel): int
                 $TAG, $A, $B
             );
             if ($orig !== $term) { $TAG[$orig] = 4; $A[$orig] = $term; $B[$orig] = 0; }
+						spendFuel($fuel);
             continue;
         }