feat(plugins): apply augment_prompt on Direct-API/Codex backends

apps/backend/agents/coder.py

@@ -130,6 +130,39 @@
 logger = logging.getLogger(__name__)
 
 
+def _augment_direct_api_prompt(
+    prompt: str,
+    provider_name: str,
+    project_dir: Path,
+    spec_dir: Path,
+    agent_type: str,
+    metadata: dict[str, object] | None,
+) -> str:
+    """Append enabled plugins' prompt augmentations to a Direct-API agent message.
+
+    The Claude SDK path augments the system prompt inside ``create_client()``,
+    so this is a no-op for the ``claude`` provider to avoid double-applying.
+    Direct providers (OpenAI, Codex, ...) carry their instructions in the
+    message, so the same plugin contributions are appended there. Any failure
+    degrades to the original prompt rather than breaking the build.
+    """
+    if provider_name == "claude":
+        return prompt
+    try:
+        from plugins.runtime import apply_plugin_prompt_augmentations
+
+        return apply_plugin_prompt_augmentations(
+            prompt,
+            project_dir,
+            spec_dir,
+            agent_type,
+            metadata=metadata,
+        )
+    except Exception as exc:
+        logger.warning("Failed to apply plugin prompt augmentations: %s", exc)
+        return prompt
+
+
 # =============================================================================
 # FILE VALIDATION UTILITIES
 # =============================================================================
@@ -1288,6 +1321,20 @@ def _validate_and_fix_implementation_plan() -> tuple[bool, list[str]]:
         analysis_only_terminal_message: str | None = None
 
         provider = create_engine_provider(provider_config)
+
+        # Plugin prompt augmentation for Direct-API / Codex backends. The Claude
+        # SDK path augments the system prompt inside create_client(); direct
+        # providers carry their instructions in the message, so append the same
+        # plugin contributions there (no-op for claude to avoid double-applying).
+        prompt = _augment_direct_api_prompt(
+            prompt,
+            provider.name,
+            project_dir,
+            spec_dir,
+            agent_type_for_session,
+            runtime_metadata,
+        )
+
         runtime_phase = (
             "planning" if current_log_phase == LogPhase.PLANNING else "coding"
         )

tests/test_coder_prompt_augmentation.py

@@ -0,0 +1,60 @@
+"""Tests for cross-backend plugin prompt augmentation on the Direct-API path.
+
+The Claude SDK backend augments the system prompt inside ``create_client()``.
+Direct providers carry their instructions in the agent message, so coder.py
+appends the same plugin contributions to that message — but only for non-claude
+providers, so the claude path is never augmented twice.
+"""
+
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+from unittest.mock import patch
+
+REPO_ROOT = Path(__file__).resolve().parent.parent
+sys.path.insert(0, str(REPO_ROOT / "apps" / "backend"))
+
+from agents.coder import _augment_direct_api_prompt
+
+_TARGET = "plugins.runtime.apply_plugin_prompt_augmentations"
+
+
+def test_claude_provider_is_not_augmented(tmp_path):
+    # Claude already augments via create_client(); the message must be left
+    # untouched so contributions are not applied twice.
+    with patch(_TARGET) as apply_mock:
+        out = _augment_direct_api_prompt(
+            "BASE", "claude", tmp_path, tmp_path, "coder", None
+        )
+    assert out == "BASE"
+    apply_mock.assert_not_called()
+
+
+def test_direct_provider_is_augmented(tmp_path):
+    augmented = "BASE\n\n# Plugin Runtime Instructions\n## demo\nhello"
+    with patch(_TARGET, return_value=augmented) as apply_mock:
+        out = _augment_direct_api_prompt(
+            "BASE", "openai", tmp_path, tmp_path, "coder", {"subtask_id": "s1"}
+        )
+    apply_mock.assert_called_once_with(
+        "BASE", tmp_path, tmp_path, "coder", metadata={"subtask_id": "s1"}
+    )
+    assert out == augmented
+
+
+def test_codex_provider_is_augmented(tmp_path):
+    with patch(_TARGET, return_value="BASE+X") as apply_mock:
+        out = _augment_direct_api_prompt(
+            "BASE", "codex", tmp_path, tmp_path, "planner", None
+        )
+    apply_mock.assert_called_once()
+    assert out == "BASE+X"
+
+
+def test_augmentation_failure_degrades_to_base_prompt(tmp_path):
+    with patch(_TARGET, side_effect=RuntimeError("boom")):
+        out = _augment_direct_api_prompt(
+            "BASE", "openai", tmp_path, tmp_path, "coder", None
+        )
+    assert out == "BASE"