dev-debug-logs

A local-development guide for finding browser, frontend, backend, and API-proxy logs created by the Fusebase development command.

In plain words
What is it for?
Use it to inspect browser errors, failed requests, frontend server output, and backend output during local Fusebase development.
Why use it?
It removes guesswork when a locally running app misbehaves by showing which log file contains each kind of error.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/fusebase-dev/fusebase-flow/dev-debug-logs
Any agent
npx skills add fusebase-dev/fusebase-flow --skill dev-debug-logs
Clone the repo
git clone --depth 1 https://github.com/fusebase-dev/fusebase-flow

Made for: Claude Code, Codex.

Per session 80 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,415 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00080 $0.01415
Opus 5 $0.00040 $0.00707
Sonnet 5 $0.00016 $0.00283
Haiku 4.5 $0.00008 $0.00142

Measured yesterday against content hash 9e5eb7ddb879, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

dev-debug-logs scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.agents/skills/dev-debug-logs/SKILL.md · 170 lines

How it starts

The opening of the file, as written. The whole thing — 170 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Dev Debug Logs

Important: This skill is for local development only. For logs from deployed app backends, use the remote-logs skill with fusebase remote-logs command.

When an app is run through:

fusebase dev start FEATURE_PATH

the CLI creates a per-session log directory inside the selected app directory:

<app-dir>/logs/dev-<timestamp>/

with these files:

  • browser-logs.jsonl
  • access-logs.jsonl
  • backend-logs.jsonl
  • frontend-dev-server-logs.jsonl

Use this skill when debugging the local app runtime. These logs are local development artifacts only.

Which Log File To Read

browser-logs.jsonl

Use for:

  • console.log / console.error output from the browser
  • uncaught browser errors
  • unhandled promise rejections
  • navigation/lifecycle events from the app page

Important:

  • It only works when the app is opened through the CLI proxy started by fusebase dev start
  • The CLI injects a browser debug script into proxied HTML pages automatically
  • Records are JSON Lines; each line is one event

Typical fields:

  • timestamp
  • type
  • level
  • message
  • args
  • error
  • url
  • pathname

backend-logs.jsonl

Use for:

  • backend stdout/stderr captured during fusebase dev start
  • runtime errors printed by an app backend
  • startup messages like port binding, env/config issues, and stack traces

Typical fields:

  • timestamp
  • appId
  • line

Important:

  • If the app defines a dedicated backend dev command, the CLI captures that process directly
  • If frontend and backend are started together from one dev.command using tools like concurrently, the CLI attempts to capture the backend lane into this file as well
  • This file is line-based output, not structured request logs

access-logs.jsonl

Use for:

  • requests made to /api through the local proxy
  • request/response headers
  • request/response bodies for small JSON/text payloads
  • proxy failures between the CLI and the app/frontend dev server

Read the full file on GitHub · 170 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 170 lines · 80 tokens per session scan A 9e5eb7ddb879

Subscribe to this mod's changes

dev-debug-logs is a skill published in the GitHub repository fusebase-dev/fusebase-flow (9 stars, last pushed 6d ago), licensed MIT. It adds 80 tokens to every session and 1,415 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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