Fix Claude log parser: use stream-json and tee for JSONL output #12947

Copilot · 2026-01-31T15:02:29Z

Claude Code CLI was configured with --output-format json, which produces a single JSON object. The log parser expects either JSON array format [{...}, {...}] or JSONL format {...}\n{...}\n (newline-delimited). Additionally, the JSON output wasn't being captured to the log file for parsing.

Changes

Engine configuration (pkg/workflow/claude_engine.go):

// Before
claudeArgs = append(claudeArgs, "--output-format", "json")

// After
claudeArgs = append(claudeArgs, "--output-format", "stream-json")

Output capture (pkg/workflow/claude_engine.go):

# Before (no stdout capture)
claude --output-format json ...

# After (capture to both console and log file)
claude --output-format stream-json ... 2>&1 | tee -a /tmp/gh-aw/agent-stdio.log

Test update (pkg/workflow/claude_engine_test.go):

Updated test expectation to check for stream-json flag

Workflow recompilation:

All 147 .lock.yml files regenerated with new CLI flags and output redirection

Technical details

The stream-json format emits newline-delimited JSON objects (JSONL), which the parser's parseLogEntries() function already handles via its line-by-line JSON parsing logic. The tee command captures stdout/stderr to the log file while also displaying output on the GitHub Actions console for real-time monitoring.

Previously, only debug logs were written to the file via --debug-file, but the JSON output from --output-format stream-json went to stdout and wasn't captured. Now both debug logs and JSON output are written to /tmp/gh-aw/agent-stdio.log for parsing, while remaining visible on the console.

Original prompt

This section details on the original issue you should resolve

<issue_title>"Log format not recognized as Claude JSON array or JSONL."</issue_title>
<issue_description>Got this error in quick start path for Claude

https://github.com/githubnext/gh-aw-trial-hono/actions/runs/21479574343</issue_description>

Comments on the Issue (you are @copilot in this section)
@pelikhan Make sure Claude is writing JSON messages in the log file. Review flags used to launch Claude.

Fixes "Log format not recognized as Claude JSON array or JSONL." #12539

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Changeset

Type: patch
Description: Claude execution steps now emit stream-json output so the log parser can consume newline-delimited JSON.

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Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

pelikhan · 2026-01-31T15:10:37Z

@copilot make sure the Claude output is also streamed to the action stdout

The log parser expects either JSON array format or JSONL format (newline-delimited JSON objects), but the code was using `--output-format json` which outputs a single JSON object. Changed to `--output-format stream-json` which outputs JSONL format compatible with the parser. - Changed `--output-format json` to `--output-format stream-json` in claude_engine.go - Updated test to expect stream-json instead of json - Recompiled all workflow files to apply the change Fixes the "Log format not recognized as Claude JSON array or JSONL" error. Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

github-actions · 2026-01-31T15:22:21Z

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github-actions · 2026-01-31T15:25:15Z

Agent Container Tool Check

Tool	Status	Version
bash	✅	5.2.21
sh	✅	available
git	✅	2.52.0
jq	✅	1.7
yq	✅	4.50.1
curl	✅	8.5.0
gh	✅	2.86.0
node	✅	24.13.0
python3	✅	3.13.11
go	✅	1.24.12
java	❌	command not found
dotnet	❌	command not found

Result: 10/12 tools available ⚠️

Missing Tools:

java - command not found
dotnet - command not found

Core development tools (shell, git, HTTP, JSON/YAML processing, GitHub CLI, Node.js, Python, Go) are all available. Java and .NET runtimes are not installed in this container.

AI generated by Agent Container Smoke Test

github-actions · 2026-01-31T15:26:16Z

Smoke Test Results

Last 2 Merged PRs:

Add expires: 2d to create-issue safe-outputs across workflows #12950: Add expires: 2d to create-issue safe-outputs across workflows
Fix stdout buffer overflow in unit test coverage step #12945: Fix stdout buffer overflow in unit test coverage step

Test Results:

✅ GitHub MCP
✅ Safe Inputs GH CLI
✅ Serena MCP
✅ Playwright
✅ File Writing
✅ Bash Tool
✅ Discussion Interaction
✅ Build gh-aw

Status: PASS

@pelikhan @Copilot

AI generated by Smoke Copilot

Add `2>&1 | tee -a` redirection to capture Claude's stream-json output to the log file while also displaying it on the GitHub Actions console for monitoring. Previously, only debug logs were written to the file via --debug-file, but the JSON output from --output-format stream-json went to stdout and wasn't captured in the log file. This meant the log parser couldn't read the JSON output. Now both debug logs and JSON output are written to /tmp/gh-aw/agent-stdio.log AND displayed on the console. Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Copilot · 2026-01-31T15:26:31Z

@copilot make sure the Claude output is also streamed to the action stdout

Added 2>&1 | tee -a redirection to stream Claude's output to both the console and the log file. The stream-json output now appears on stdout (visible in GitHub Actions) while also being captured in /tmp/gh-aw/agent-stdio.log for parsing. Fixed in commit 74153ee.

github-actions · 2026-01-31T15:26:36Z

📰 VERDICT: Smoke Copilot has concluded. All systems operational. This is a developing story. 🎤

github-actions · 2026-01-31T15:31:06Z

PRs: Fix Claude log parser: use stream-json for JSONL output; [fp-enhancer] Apply functional programming and immutability improvements
GitHub MCP merged PRs ✅
safeinputs-gh PR list ✅
Serena activate ✅
Playwright GitHub title ✅
Tavily search ✅
File write + cat ✅
Discussion query + comment ✅
Build gh-aw ✅
Overall: PASS

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Initial plan

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Copilot AI assigned Copilot and pelikhan Jan 31, 2026

Copilot started work on behalf of pelikhan January 31, 2026 15:02 View session

Initial investigation of Claude log format issue

49a8c67

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Fix log format not recognized as Claude JSON~~ Fix Claude log parser: use stream-json for JSONL output Jan 31, 2026

Copilot AI requested a review from pelikhan January 31, 2026 15:19

Copilot finished work on behalf of pelikhan January 31, 2026 15:19

Copilot started work on behalf of pelikhan January 31, 2026 15:20 View session

pelikhan added the smoke label Jan 31, 2026

Add changeset [skip-ci]

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github-actions bot mentioned this pull request Jan 31, 2026

Smoke Test: Copilot - 21546586976 #12954

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github-actions bot mentioned this pull request Jan 31, 2026

Smoke Test: Claude - 21546586967 #12956

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Copilot AI changed the title ~~Fix Claude log parser: use stream-json for JSONL output~~ Fix Claude log parser: use stream-json and tee for JSONL output Jan 31, 2026

Copilot finished work on behalf of pelikhan January 31, 2026 15:27

github-actions bot added the smoke-codex label Jan 31, 2026

pelikhan marked this pull request as ready for review January 31, 2026 15:33

pelikhan merged commit 5bc946c into main Jan 31, 2026
114 of 115 checks passed

pelikhan deleted the copilot/fix-claude-json-log-format branch January 31, 2026 15:34

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Fix Claude log parser: use stream-json and tee for JSONL output #12947

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