fix(code): tolerate bare agent JSON responses

packages/code/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- **Structured agent responses**: feasibility checks now accept the valid bare JSON commonly returned by Codex instead of requiring a Markdown code fence. Feasibility, estimation, and auto-review share brace-aware extraction that also tolerates narration and ignores unrelated braces in prose
+
 ## [2.3.2] - 2026-08-18
 
 ### Fixed

packages/code/src/index.ts

@@ -42,6 +42,7 @@ import { buildSandboxDoctorReport, getSandbox, setSandboxOverride } from "./lib/
 import { isMarkdownFilePath } from "@devintern/task-trackers";
 import { findEnvFile, maybeOfferCliUpdate, resolveConfigDir } from "@devintern/utils";
 import { ReadonlyAnalysisError, runAnalysisWithFallback } from "./lib/analysis-mode";
+import { parseAgentJsonObject } from "./lib/agent-json";
 import { TaskFormatter } from "./lib/task-formatter";
 import type { RetryPromptContext } from "./lib/task-formatter";
 import { resolveOutputDir } from "./lib/output-dir";
@@ -2735,21 +2736,15 @@ async function runClarityCheck(
  * @throws When JSON is missing or required fields are invalid
  */
 function parseClarityResponse(output: string): ClarityAssessment {
-  // Extract JSON from Agent's response
-  const jsonMatch = output.match(/```json\s*([\s\S]*?)\s*```/);
-  if (!jsonMatch) {
-    // Provide more specific error based on output content
-    if (detectMaxTurnsReached(output, "")) {
-      throw new Error("warn: Agent reached max turns - no JSON assessment available");
-    }
-    if (output.trim().length === 0) {
-      throw new Error("warn: Empty response from Agent");
-    }
-    throw new Error("warn: No JSON found in Agent response");
+  if (detectMaxTurnsReached(output, "")) {
+    throw new Error("warn: Agent reached max turns - no JSON assessment available");
+  }
+  if (output.trim().length === 0) {
+    throw new Error("warn: Empty response from Agent");
   }
 
   try {
-    const assessment = JSON.parse(jsonMatch[1]);
+    const assessment = parseAgentJsonObject(output, "isImplementable");
 
     // Validate required fields
     if (
@@ -2762,7 +2757,7 @@ function parseClarityResponse(output: string): ClarityAssessment {
       throw new Error("warn: Invalid assessment structure - missing required fields");
     }
 
-    return assessment;
+    return assessment as unknown as ClarityAssessment;
   } catch (error) {
     if (error instanceof SyntaxError) {
       throw new Error(`warn: Malformed JSON in Agent response: ${error.message}`);
@@ -3053,52 +3048,20 @@ async function runEstimation(
  * @throws When JSON is invalid or values are out of range
  */
 function parseEstimationResponse(output: string): EstimationResult {
-  // Try to find JSON in the response — with or without code fences
-  let jsonStr: string | null = null;
-
-  const fencedMatch = output.match(/```(?:json)?\s*([\s\S]*?)\s*```/);
-  if (fencedMatch) {
-    jsonStr = fencedMatch[1];
-  } else {
-    // Try to extract a raw JSON object containing "storyPoints".
-    // We find the last "storyPoints" in the output, then try { positions
-    // before it (nearest first) paired with the last } after it, letting
-    // JSON.parse decide validity. This avoids greedy-regex issues when
-    // the surrounding text contains stray braces (e.g. URL templates).
-    const spIdx = output.lastIndexOf('"storyPoints"');
-    if (spIdx !== -1) {
-      const endIdx = output.lastIndexOf("}");
-      if (endIdx > spIdx) {
-        for (let i = output.lastIndexOf("{", spIdx); i >= 0; i = output.lastIndexOf("{", i - 1)) {
-          const candidate = output.substring(i, endIdx + 1);
-          try {
-            JSON.parse(candidate);
-            jsonStr = candidate;
-            break;
-          } catch {
-            continue;
-          }
-        }
-      }
-    }
-  }
-
-  if (!jsonStr) {
-    throw new Error("No JSON found in estimation response");
-  }
-
-  const parsed = JSON.parse(jsonStr);
+  const parsed = parseAgentJsonObject(output, "storyPoints");
 
   // Validate required fields
   const validPoints = [1, 2, 3, 5, 8, 13, 21];
-  if (!validPoints.includes(parsed.storyPoints)) {
+  const storyPoints = parsed.storyPoints;
+  if (typeof storyPoints !== "number" || !validPoints.includes(storyPoints)) {
     throw new Error(
-      `Invalid story points value: ${parsed.storyPoints}. Must be one of: ${validPoints.join(", ")}`,
+      `Invalid story points value: ${storyPoints}. Must be one of: ${validPoints.join(", ")}`,
     );
   }
 
-  if (!["high", "medium", "low"].includes(parsed.confidence)) {
-    throw new Error(`Invalid confidence level: ${parsed.confidence}. Must be high, medium, or low`);
+  const confidence = parsed.confidence;
+  if (confidence !== "high" && confidence !== "medium" && confidence !== "low") {
+    throw new Error(`Invalid confidence level: ${confidence}. Must be high, medium, or low`);
   }
 
   // Clamp implementationConfidence to 0-10, default to 5 if missing
@@ -3107,13 +3070,13 @@ function parseEstimationResponse(output: string): EstimationResult {
   implConf = Math.max(0, Math.min(10, Math.round(implConf)));
 
   return {
-    storyPoints: parsed.storyPoints,
-    confidence: parsed.confidence,
+    storyPoints,
+    confidence,
     implementationConfidence: implConf,
-    reasoning: parsed.reasoning || "",
+    reasoning: typeof parsed.reasoning === "string" ? parsed.reasoning : "",
     risks: Array.isArray(parsed.risks) ? parsed.risks : [],
     unclearAreas: Array.isArray(parsed.unclearAreas) ? parsed.unclearAreas : [],
-    summary: parsed.summary || "",
+    summary: typeof parsed.summary === "string" ? parsed.summary : "",
   };
 }
 

packages/code/src/lib/agent-json.ts

@@ -0,0 +1,98 @@
+/**
+ * Extract a structured JSON object from an agent's final response.
+ *
+ * Agent CLIs do not consistently preserve formatting instructions: the same
+ * prompt may produce fenced JSON, bare JSON, or JSON surrounded by narration.
+ * This parser accepts all three shapes and ignores unrelated braces in prose.
+ */
+
+function balancedObjectCandidates(text: string): string[] {
+  const candidates: string[] = [];
+  let start = -1;
+  let depth = 0;
+  let inString = false;
+  let escaped = false;
+
+  for (let index = 0; index < text.length; index += 1) {
+    const character = text[index];
+
+    if (start === -1) {
+      if (character === "{") {
+        start = index;
+        depth = 1;
+      }
+      continue;
+    }
+
+    if (inString) {
+      if (escaped) {
+        escaped = false;
+      } else if (character === "\\") {
+        escaped = true;
+      } else if (character === '"') {
+        inString = false;
+      }
+      continue;
+    }
+
+    if (character === '"') {
+      inString = true;
+    } else if (character === "{") {
+      depth += 1;
+    } else if (character === "}") {
+      depth -= 1;
+      if (depth === 0) {
+        candidates.push(text.slice(start, index + 1));
+        start = -1;
+      }
+    }
+  }
+
+  return candidates;
+}
+
+/**
+ * Parse the expected JSON object from raw agent stdout.
+ *
+ * Fenced objects take precedence. For bare objects, the last matching object
+ * wins because agents commonly narrate before emitting their final answer.
+ *
+ * @param output - Raw agent stdout
+ * @param requiredKey - Key that identifies the expected response object
+ * @returns Parsed JSON object containing `requiredKey`
+ * @throws When no valid matching object is present
+ */
+export function parseAgentJsonObject(output: string, requiredKey: string): Record<string, unknown> {
+  const candidates: string[] = [];
+  const fencedPattern = /```(?:json)?\s*([\s\S]*?)\s*```/gi;
+
+  for (const match of output.matchAll(fencedPattern)) {
+    if (match[1]) {
+      candidates.push(match[1]);
+    }
+  }
+
+  candidates.push(...balancedObjectCandidates(output).reverse());
+
+  let lastParseError: unknown;
+  for (const candidate of candidates) {
+    try {
+      const parsed = JSON.parse(candidate) as unknown;
+      if (
+        typeof parsed === "object" &&
+        parsed !== null &&
+        !Array.isArray(parsed) &&
+        Object.hasOwn(parsed, requiredKey)
+      ) {
+        return parsed as Record<string, unknown>;
+      }
+    } catch (error) {
+      lastParseError = error;
+    }
+  }
+
+  if (lastParseError instanceof SyntaxError && candidates.length === 1) {
+    throw lastParseError;
+  }
+  throw new Error(`No valid JSON object containing "${requiredKey}" found in Agent response`);
+}

packages/code/src/lib/auto-review-loop.ts

@@ -13,6 +13,7 @@ import { writeFileSync, readFileSync, existsSync, mkdirSync } from "fs";
 import { join } from "path";
 import { spawnAgent, reapTree, resolveExecutablePathWithRetry } from "@devintern/agent-harness";
 import type { AgentHarness } from "@devintern/agent-harness";
+import { parseAgentJsonObject } from "./agent-json";
 import { buildHeadlessAgentArgs, HEADLESS_AGENT_STDIO } from "./agent-spawn";
 import { getSandbox } from "./sandbox";
 import type {
@@ -77,30 +78,28 @@ ${prDiff}
    - **low**: Style inconsistencies, minor optimizations
    - **info**: Suggestions, alternatives, educational feedback
 
-4. Provide your feedback as JSON in the following format:
+4. Provide your feedback as one JSON object in the following format:
 
-\`\`\`json
 {
   "summary": "Brief overall assessment of the PR (2-3 sentences)",
   "items": [
     {
       "priority": "critical|high|medium|low|info",
       "category": "code-quality|bug|performance|security|testing|documentation|style",
       "file": "path/to/file.ts",
-      "line": "42" or "42-45",
+      "line": "42-45",
       "issue": "Clear description of the issue",
       "suggestion": "Specific actionable fix or improvement"
     }
   ],
   "approved": false
 }
-\`\`\`
 
 5. Set "approved": true ONLY if all issues are low priority or informational
 6. Be constructive and specific in your feedback
 7. Focus on actionable improvements
 
-**IMPORTANT**: Your response must be valid JSON only. Do not include any explanatory text outside the JSON block.
+**IMPORTANT**: Return only the valid JSON object. Do not include Markdown fences or explanatory text.
 `;
 }
 
@@ -281,18 +280,8 @@ function getPRDiff(baseBranch: string, workingDir: string): string {
  * @throws When no JSON is found or the structure is invalid
  */
 function parseReviewFeedback(agentOutput: string): ReviewFeedback {
-  // Extract JSON from potential markdown code blocks
-  const jsonMatch =
-    agentOutput.match(/```json\s*([\s\S]*?)\s*```/) || agentOutput.match(/\{[\s\S]*\}/);
-
-  if (!jsonMatch) {
-    throw new Error("No JSON found in Agent output");
-  }
-
-  const jsonStr = jsonMatch[1] || jsonMatch[0];
-
   try {
-    const feedback = JSON.parse(jsonStr) as ReviewFeedback;
+    const feedback = parseAgentJsonObject(agentOutput, "approved");
 
     // Validate structure
     if (
@@ -303,7 +292,7 @@ function parseReviewFeedback(agentOutput: string): ReviewFeedback {
       throw new Error("Invalid feedback structure");
     }
 
-    return feedback;
+    return feedback as unknown as ReviewFeedback;
   } catch (error) {
     throw new Error(`Failed to parse review feedback JSON: ${error}`);
   }

packages/code/src/lib/task-formatter.ts

@@ -611,25 +611,20 @@ You are a senior software engineer reviewing a task before implementation. Your
 
     prompt += `## Assessment Instructions
 
-Please assess this task for basic implementation feasibility. Respond with a JSON object containing:
+Please assess this task for basic implementation feasibility. Return only one valid JSON object with this shape (no Markdown fences or explanatory text):
 
-\`\`\`json
 {
-  "isImplementable": boolean,
-  "clarityScore": number, // 1-10 scale (10 = perfectly clear)
-  "issues": [
-    {
-      "category": "missing_requirements" | "unclear_scope" | "missing_context" | "ambiguous_description" | "critical_gaps",
-      "description": "Specific issue description",
-      "severity": "critical" | "major" | "minor"
-    }
-  ],
-  "recommendations": [
-    "Specific recommendation for improving clarity"
-  ],
+  "isImplementable": true,
+  "clarityScore": 8,
+  "issues": [],
+  "recommendations": [],
   "summary": "Brief summary of the assessment"
 }
-\`\`\`
+
+Each issue must contain:
+- "category": one of "missing_requirements", "unclear_scope", "missing_context", "ambiguous_description", or "critical_gaps"
+- "description": a specific issue description
+- "severity": one of "critical", "major", or "minor"
 
 ## Evaluation Criteria (Relaxed for Real-World Development)
 

packages/code/tests/agent-json.test.ts

@@ -0,0 +1,54 @@
+import { describe, expect, test } from "bun:test";
+import { parseAgentJsonObject } from "../src/lib/agent-json";
+
+describe("parseAgentJsonObject", () => {
+  test("parses fenced JSON", () => {
+    expect(parseAgentJsonObject('```json\n{"approved": true}\n```', "approved")).toEqual({
+      approved: true,
+    });
+  });
+
+  test("parses bare JSON returned by Codex", () => {
+    const output = `{
+  "isImplementable": true,
+  "clarityScore": 8,
+  "issues": [],
+  "recommendations": [],
+  "summary": "The task is implementable."
+}`;
+
+    expect(parseAgentJsonObject(output, "isImplementable")).toEqual({
+      isImplementable: true,
+      clarityScore: 8,
+      issues: [],
+      recommendations: [],
+      summary: "The task is implementable.",
+    });
+  });
+
+  test("parses JSON surrounded by narration and unrelated braces", () => {
+    const output = `I checked PATCH /items/{id} first.
+{"approved":false,"summary":"A string with {braces}","items":[]}
+That is the final review.`;
+
+    expect(parseAgentJsonObject(output, "approved")).toEqual({
+      approved: false,
+      summary: "A string with {braces}",
+      items: [],
+    });
+  });
+
+  test("prefers the last matching bare object", () => {
+    const output = '{"storyPoints":1}\nFinal: {"storyPoints":5,"confidence":"high"}';
+    expect(parseAgentJsonObject(output, "storyPoints")).toEqual({
+      storyPoints: 5,
+      confidence: "high",
+    });
+  });
+
+  test("throws when the expected object is absent", () => {
+    expect(() => parseAgentJsonObject("No structured response.", "approved")).toThrow(
+      'No valid JSON object containing "approved"',
+    );
+  });
+});