Improve terminal readability for async logs by deduplicating repeated headers

[sunnynarula]

Description

When using Console with async runtimes (e.g. Falcon + Async + Rails), logs become difficult to read for humans due to repeated, identical headers being printed for every log event.

This is especially noticeable in development when scanning logs in a terminal.

---

Problem

In async environments, many consecutive log events share the same execution context (subject + annotations), but Console prints the full header for every event.

Example (simplified):

debug: Rails: Reading HTTP/1.1 requests for Async::HTTP::Protocol::HTTP1::Server.
| User Load (0.5ms) SELECT ...
debug: Rails: Reading HTTP/1.1 requests for Async::HTTP::Protocol::HTTP1::Server.
| ↳ app/controllers/users/sessions_controller.rb:36
debug: Rails: Reading HTTP/1.1 requests for Async::HTTP::Protocol::HTTP1::Server.
| TRANSACTION BEGIN

The information is correct, but the repeated header:

debug: Rails: Reading HTTP/1.1 requests for Async::HTTP::Protocol::HTTP1::Server.

adds significant visual noise and makes it hard to scan SQL, controller flow, and rendering steps.

Because async execution interleaves events from different fibers, ordering cannot be made deterministic — but repeating identical headers provides no additional information.

---

Observation

In practice:

• Many consecutive events share the same:
  • subject (e.g. Rails)
  • annotations (e.g. HTTP protocol / request loop)
• The header only needs to be shown once per context
• Humans naturally group log lines visually rather than by strict order

---

Proposed Solution

Introduce an optional terminal output mode that deduplicates consecutive identical headers.

Tentative names:

• Console::Output::TerminalSummary
• Terminal::Compact
• Terminal::Grouped

Behavior:

• Track the previously rendered header
• If the current event’s header matches the previous one:
  • suppress the header
  • print only the indented body
• If the header changes:
  • print the full header again

This would dramatically improve readability while preserving all log information.

---

Explicit Non-Goals

This proposal intentionally does not:

• reorder events
• group logs by request or fiber
• infer request boundaries
• change logging semantics
• affect machine-readable outputs (Serialized)

It is purely a presentation-layer improvement for human-readable terminal output.

---

Why This Belongs in Console

• The issue is at the output formatting layer
• Console already owns:
  • header rendering
  • subject formatting
  • indentation rules
• No changes are required in:
  • Rails
  • Falcon
  • Async
  • application code

The feature would be:

• opt-in
• backwards-compatible
• low risk

---

Possible Configuration

Examples (naming flexible):

CONSOLE_OUTPUT=TerminalSummary

or

CONSOLE_OUTPUT=Terminal
CONSOLE_COMPACT_HEADERS=1

or via config/console.rb.

Context

This issue arose during real-world use of Console with:

• Ruby on Rails
• Falcon
• Async
• concurrent request handling in development

The async execution model is correct and expected; this proposal focuses solely on improving human log readability under that model.

[ioquatix]

I like this idea. If it's just removing redundant information, we can make it the default for terminal output. There is no hard requirement on terminal output since it's user facing.