fix: build patches from complete target context

packages/casan-harness/scripts/bash/goal-orchestrator.py

@@ -206,20 +206,34 @@ def context_candidates(project: dict, goal: str):
     return sorted(candidates, key=lambda item: (-item[0], item[1]))
 
 
-def build_context(job_path: str, project_id: str, goal: str):
+def build_context(job_path: str, project_id: str, goal: str, write_intent=False):
     project = registered_project(project_id)
     candidates = context_candidates(project, goal)
     excerpts, manifest_files, characters = [], [], 0
-    max_files, max_characters, per_file = 16, 7_000, 1_200
+    # A diff can only apply when the model sees the exact target-file content.
+    # Read-only analysis stays compact; write-intent gives the three most
+    # relevant files their complete bounded snapshot and retains supporting
+    # contracts within a larger, still finite context budget.
+    max_files = 12 if write_intent else 16
+    max_characters = 30_000 if write_intent else 7_000
     for score, relative, raw in candidates:
         if len(excerpts) >= max_files or characters >= max_characters:
             break
-        excerpt = redact_context(raw[:min(per_file, max_characters - characters)]).strip()
+        per_file = 16_000 if write_intent and len(excerpts) < 3 else (3_000 if write_intent else 1_200)
+        source = redact_context(raw).strip()
+        excerpt = source[:min(per_file, max_characters - characters)].strip()
         if not excerpt or context_excerpt_is_sensitive(excerpt):
             continue
         excerpts.append(f"### FILE: {relative}\n{excerpt}")
         characters += len(excerpt)
-        manifest_files.append({"path": relative, "sha256": sha(raw), "characters": len(excerpt), "relevance": score})
+        manifest_files.append({
+            "path": relative,
+            "sha256": sha(raw),
+            "characters": len(excerpt),
+            "source_characters": len(source),
+            "truncated": len(excerpt) < len(source),
+            "relevance": score,
+        })
     bundle = "\n\n".join(excerpts)
     allowed, safe_bundle = scan(bundle, "input")
     if not allowed:
@@ -238,7 +252,7 @@ def build_context(job_path: str, project_id: str, goal: str):
         "files": manifest_files,
         "file_count": len(manifest_files),
         "characters": characters,
-        "truncated": len(manifest_files) < len(candidates),
+        "truncated": len(manifest_files) < len(candidates) or any(item["truncated"] for item in manifest_files),
         "bundle_sha256": sha(bundle),
     }
     atomic_json(manifest_path, manifest)
@@ -284,6 +298,52 @@ def validate_patch_check(patch: str) -> None:
         raise ValueError(f"goal_patch_check_failed:{detail}")
 
 
+def normalize_unified_diff(patch: str) -> str:
+    """Repair mechanical unified-diff hunk counts without changing code.
+
+    Language models frequently emit the intended +/- lines but miscalculate
+    the counts in `@@ -old,count +new,count @@`, or lose the single space on a
+    blank context line. Both make git report a syntactically corrupt patch.
+    CASAN can correct those two mechanical properties deterministically. It
+    never invents code lines, and leaves likely truncated hunks untouched.
+    """
+    lines = patch.rstrip("\n").split("\n")
+    normalized, changed = [], False
+    hunk_pattern = re.compile(r"^@@ -(\d+)(?:,(\d+))? \+(\d+)(?:,(\d+))? @@(.*)$")
+    index = 0
+    while index < len(lines):
+        header = hunk_pattern.match(lines[index])
+        if not header:
+            normalized.append(lines[index])
+            index += 1
+            continue
+        body, cursor = [], index + 1
+        while cursor < len(lines) and not lines[cursor].startswith(("@@ ", "diff --git ")):
+            line = lines[cursor]
+            if line == "":
+                line = " "
+                changed = True
+            if not line.startswith((" ", "+", "-", "\\")):
+                return patch
+            body.append(line)
+            cursor += 1
+        old_count = sum(1 for line in body if line.startswith((" ", "-")))
+        new_count = sum(1 for line in body if line.startswith((" ", "+")))
+        declared_old = int(header.group(2) or "1")
+        declared_new = int(header.group(4) or "1")
+        # A replacement cut immediately after its '-' lines must not be
+        # reinterpreted as a valid deletion-only patch.
+        if cursor == len(lines) and body and body[-1].startswith("-") and declared_new > new_count:
+            return patch
+        corrected = f"@@ -{header.group(1)},{old_count} +{header.group(3)},{new_count} @@{header.group(5)}"
+        if corrected != lines[index] or declared_old != old_count or declared_new != new_count:
+            changed = True
+        normalized.append(corrected)
+        normalized.extend(body)
+        index = cursor
+    return "\n".join(normalized) + "\n" if changed else patch
+
+
 def validate_write_output(text: str) -> str:
     """Fail at the producing harness when a write-intent reply is not a diff.
 
@@ -292,8 +352,17 @@ def validate_write_output(text: str) -> str:
     that violated the required output contract.
     """
     patch = extract_patch(text)
-    validate_patch_check(patch)
-    return patch
+    try:
+        validate_patch_check(patch)
+        return patch
+    except ValueError as original_error:
+        if "corrupt patch" not in str(original_error):
+            raise
+        normalized = normalize_unified_diff(patch)
+        if normalized == patch:
+            raise
+        validate_patch_check(normalized)
+        return normalized
 
 
 def patch_repair_attempts() -> int:
@@ -381,7 +450,7 @@ def repair_write_output(model: str, original_prompt: str, invalid_output: str, c
             })
             continue
         try:
-            validate_write_output(output)
+            checked_output = validate_write_output(output)
         except ValueError as error:
             last_reason = str(error)
             attempts.append({
@@ -408,7 +477,7 @@ def repair_write_output(model: str, original_prompt: str, invalid_output: str, c
             "reason": "ok",
         })
         metadata["repair_attempts"] = attempts
-        return True, output, metadata, "ok"
+        return True, checked_output, metadata, "ok"
     last_metadata["repair_attempts"] = attempts
     return False, "", last_metadata, f"goal_patch_repair_invalid:{last_reason}"
 
@@ -762,7 +831,8 @@ def run(job_path: str) -> int:
         if not allowed:
             emit(goal_id, "H4-security", "blocked", "Objective rejected by security boundary")
             raise ValueError("goal_security_blocked")
-        context_bundle, context_manifest, context_manifest_path = build_context(job_path, project_id, safe_goal)
+        write_intent = requests_side_effect(safe_goal)
+        context_bundle, context_manifest, context_manifest_path = build_context(job_path, project_id, safe_goal, write_intent)
         context_summary = {
             "files": context_manifest["file_count"],
             "characters": context_manifest["characters"],
@@ -776,8 +846,6 @@ def run(job_path: str) -> int:
         })
         emit(goal_id, "H4-security", "running", "Objective and workspace snapshot passed; model outputs pending")
 
-        write_intent = requests_side_effect(safe_goal)
-
         stage(job_path, "local-worker", "running", "Local model is developing the primary solution", job.get("local_provider", ""), local_model)
         emit(goal_id, "H2-tool", "running", "Local worker is developing a solution", {"provider": job.get("local_provider", ""), "model": local_model})
         output_contract = (
@@ -802,7 +870,7 @@ def run(job_path: str) -> int:
             raise ValueError("local_output_security_blocked")
         if write_intent:
             try:
-                validate_write_output(safe_local)
+                safe_local = validate_write_output(safe_local)
             except ValueError as first_error:
                 repair_candidates = patch_repair_models(local_model)[:patch_repair_attempts()]
                 repair_model = repair_candidates[0] if repair_candidates else local_model
@@ -819,7 +887,7 @@ def run(job_path: str) -> int:
                         emit(goal_id, "H4-security", "blocked", "Repaired local worker output rejected")
                         raise ValueError("local_output_security_blocked")
                     try:
-                        validate_write_output(safe_local)
+                        safe_local = validate_write_output(safe_local)
                         reason = ""
                     except ValueError as repair_error:
                         reason = f"goal_patch_repair_invalid:{repair_error}"
@@ -866,7 +934,7 @@ def run(job_path: str) -> int:
                 raise ValueError("cloud_output_security_blocked")
             if write_intent:
                 try:
-                    validate_write_output(safe_result)
+                    safe_result = validate_write_output(safe_result)
                 except ValueError as error:
                     cloud_ok = False
                     cloud_reason = f"reviewer_output_contract_invalid:{error}"

packages/casan-harness/tests/goal-patch-workflow-tests.py

@@ -43,6 +43,43 @@ class GoalPatchWorkflowTests(unittest.TestCase):
         with self.assertRaisesRegex(ValueError, "goal_patch_check_failed"):
             ORCHESTRATOR.validate_write_output(truncated)
 
+    def test_hunk_counts_and_blank_context_are_repaired_deterministically(self):
+        corrupt = (
+            "diff --git a/apps/okr/frontend/a.ts b/apps/okr/frontend/a.ts\n"
+            "--- a/apps/okr/frontend/a.ts\n+++ b/apps/okr/frontend/a.ts\n"
+            "@@ -10,8 +10,9 @@\n context\n-old\n+new\n\n tail\n"
+        )
+        normalized = ORCHESTRATOR.normalize_unified_diff(corrupt)
+        self.assertIn("@@ -10,4 +10,4 @@", normalized)
+        self.assertIn("\n \n tail\n", normalized)
+
+    def test_write_validation_uses_normalized_patch_after_corrupt_error(self):
+        corrupt = "diff --git a/a b/a\n--- a/a\n+++ b/a\n@@ -1,9 +1,9 @@\n-old\n+new\n"
+        with patch.object(ORCHESTRATOR, "validate_patch_check", side_effect=[ValueError("goal_patch_check_failed:error: corrupt patch at line 7"), None]) as check:
+            normalized = ORCHESTRATOR.validate_write_output(corrupt)
+        self.assertIn("@@ -1,1 +1,1 @@", normalized)
+        self.assertEqual(check.call_count, 2)
+
+    def test_truncated_replacement_is_not_reinterpreted_as_deletion(self):
+        truncated = "diff --git a/a b/a\n--- a/a\n+++ b/a\n@@ -1,1 +1,1 @@\n-old\n"
+        self.assertEqual(ORCHESTRATOR.normalize_unified_diff(truncated), truncated)
+
+    def test_write_context_keeps_the_most_relevant_target_file_complete(self):
+        raw = "export function KeyResultDetail() {\n" + ("  return null;\n" * 180) + "}\n"
+        candidates = [
+            (20, "apps/okr/frontend/src/pages/KeyResultDetail.tsx", raw),
+            (5, "docs/technical_architecture.md", "architecture" * 400),
+        ]
+        project = {"domain": "OKR", "domain_root": "apps/okr", "roots": []}
+        with tempfile.TemporaryDirectory() as directory, \
+                patch.object(ORCHESTRATOR, "registered_project", return_value=project), \
+                patch.object(ORCHESTRATOR, "context_candidates", return_value=candidates), \
+                patch.object(ORCHESTRATOR, "scan", side_effect=lambda text, mode: (True, text)):
+            bundle, manifest, _ = ORCHESTRATOR.build_context(os.path.join(directory, "goal.json"), "okr", "KeyResultDetail", True)
+        self.assertIn(raw.strip(), bundle)
+        self.assertEqual(manifest["files"][0]["characters"], len(raw.strip()))
+        self.assertFalse(manifest["files"][0]["truncated"])
+
     def test_invalid_write_output_gets_one_bounded_repair_attempt(self):
         repaired = "```diff\ndiff --git a/apps/okr/frontend/a.ts b/apps/okr/frontend/a.ts\n--- a/apps/okr/frontend/a.ts\n+++ b/apps/okr/frontend/a.ts\n@@ -1 +1 @@\n-a\n+b\n```"
         with patch.dict(os.environ, {"CASAN_GOAL_PATCH_REPAIR_ATTEMPTS": "1"}, clear=False), \