[BUG] Groq 400 json_validate_failed causes silent fallback failure in code-generation

[koydas]

🎯 Goal

Fix the code-generation job so that a Groq json_validate_failed error is detected, logged, and correctly falls through to the Anthropic provider instead of crashing the run.

📍 Context

• Repo: autonomous-dev-loop
• Component: scripts/lib/groq_client.mjs, scripts/lib/error_taxonomy.mjs, scripts/lib/llm_client.mjs
• Environment: GitHub Actions — code-generation job

🔗 Status (re-checked 2026-10-01 on main @ 4e499fb)

• Blocked by [BUG] callLLM provider fallback sends the primary provider's model, API key and URL to the fallback provider #162. The fallback to Anthropic cannot succeed in production until [BUG] callLLM provider fallback sends the primary provider's model, API key and URL to the fallback provider #162 is fixed: today the Anthropic attempt receives the primary (Groq) apiKey, apiUrl and model, so it POSTs to Groq's endpoint and fails with 401. A mocked unit test for criterion 3 would pass anyway, because the mocked fetch accepts any key and URL. Write that test against the per-provider config introduced by [BUG] callLLM provider fallback sends the primary provider's model, API key and URL to the fallback provider #162 (assert URL, auth header and model).
• The "Anthropic fails silently" part is out of date. callLLM now pushes every provider's error into All providers failed: …, so criterion 4 is already met. The real cause behind the missing/failed Anthropic fallback is [BUG] callLLM provider fallback sends the primary provider's model, API key and URL to the fallback provider #162.
• Still missing: err.code = 'json_validate_failed' in groq_client.mjs, the per-provider log in llm_client.mjs, and both unit tests. generate_issue_change.mjs still uses the default response_format: json_object, so the error can still happen.
• Overlap with [FEATURE] Chaos test scenarios for transient failure recovery #134 on scripts/tests/llm_client.test.mjs: do not generate both in parallel.

❗ Observed problem

When Groq's JSON mode cannot constrain a large structured output (large file_content strings in the changes array), it returns HTTP 400 with code: "json_validate_failed". The pipeline crashes with:

{"level":"error","msg":"Fatal error","error":"All providers failed: groq: Groq API HTTP error 400: {\"error\":{\"code\":\"json_validate_failed\",...}}"}

Root cause: classifyError('400') in error_taxonomy.mjs returns 'UNKNOWN' (400 is not in the PERMANENT or TRANSIENT lists). In groq_client.mjs, retryable is false for 400 so no retry happens. In llm_client.mjs, UNKNOWN does not trigger a break, so the loop should continue to Anthropic — but the final error message only reports the Groq failure, indicating the Anthropic fallback also fails silently without surfacing its own error clearly.

🔁 Steps to reproduce

1. Trigger the code-generation workflow on an issue requiring multi-file changes (≥ 3 large files).
2. Observe the Groq provider returning HTTP 400 with json_validate_failed.
3. The job exits with code 1 — "All providers failed".

Example: run 26795257405, job 78990103447 (run ID issue-134)

✅ Expected behavior

When Groq returns json_validate_failed, the system:

1. Immediately stops retrying Groq (already the case — retryable: false).
2. Logs the Groq failure with its error code for traceability.
3. Falls through to Anthropic and succeeds (or reports the Anthropic failure clearly if it also fails).

🧪 Acceptance criteria

• When Groq returns HTTP 400 with code: "json_validate_failed", groq_client.mjs attaches err.code = 'json_validate_failed' to the thrown error so downstream handlers can inspect it.
• llm_client.mjs logs { provider: 'groq', error_type: 'json_validate_failed', status: 400 } before moving to the next provider.
• When Groq fails with json_validate_failed and Anthropic is available, the callLLM function returns the Anthropic response successfully (no crash). Requires [BUG] callLLM provider fallback sends the primary provider's model, API key and URL to the fallback provider #162.
• When Groq fails with json_validate_failed and Anthropic also fails, the error message includes both failures (e.g. "All providers failed: groq: ..., anthropic: ...") so the actual Anthropic error is visible. (Already the case on main: callLLM lists every provider error.)
• Unit test in scripts/tests/llm_client.test.mjs: mocking Groq to throw a json_validate_failed 400 error verifies that Anthropic is called as fallback, with Anthropic's own URL, key and model (see [BUG] callLLM provider fallback sends the primary provider's model, API key and URL to the fallback provider #162).
• Unit test in scripts/tests/groq_client.test.mjs: a mocked 400 response with json_validate_failed body results in an error with err.code === 'json_validate_failed' and err.retryable === false.

⚠️ Constraints

• Do not change the retry behavior for other 400 errors (e.g. malformed payloads unrelated to JSON mode).
• The PERMANENT break in llm_client.mjs stops all providers — do not reclassify json_validate_failed as PERMANENT; the fallback to Anthropic must remain active.
• Backward compatible: existing error handling for 401, 403, 429, 5xx must be unaffected.

[github-actions]

🚫 Issue Validation Report

Field	Value
Status	INVALID — needs refinement
Score	100/100 [██████████]

🚫 Blockers

The following issues must be resolved before this issue can proceed:

• Implementation depends on unresolved issue [BUG] callLLM provider fallback sends the primary provider's model, API key and URL to the fallback provider #162, which must be fixed before adding the fallback logic

💡 Suggested Acceptance Criteria

Copy the block below and paste it into the issue description, then save. Saving will re-trigger validation automatically.

## Acceptance Criteria

- [ ] [ ] groq_client.mjs throws an error with err.code set to "json_validate_failed" and err.retryable set to false when receiving HTTP 400 with that code
- [ ] [ ] llm_client.mjs logs an object { provider: "groq", error_type: "json_validate_failed", status: 400 } before proceeding to the next provider
- [ ] [ ] When Groq fails with json_validate_failed and Anthropic is available, callLLM returns the Anthropic response without throwing
- [ ] [ ] When both Groq and Anthropic fail, the final error message includes both provider errors in the format "All providers failed: groq: ..., anthropic: ..."
- [ ] [ ] Unit test in scripts/tests/groq_client.test.mjs verifies that a mocked 400 response with json_validate_failed results in err.code === "json_validate_failed" and err.retryable === false

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Next step: Edit this issue, paste the acceptance criteria above (or write your own testable AC), and click Save. This will re-trigger the validation agent automatically.