A 1M-Token Context Window Is Now Claude Code's Default — Here's What to Do With It

TL;DR: Claude Sonnet 5 is Claude Code's new default with a 1M-token context window — large enough for your whole codebase; here are three workflows that weren't practical before.

Sonnet 5 shipped June 30 and became Claude Code's default on July 1 (v2.1.197). The model is a meaningful upgrade in agentic ability, but the headline for day-to-day use is the context window: 1 million tokens — roughly 750,000 words, or a typical medium-sized codebase in one shot.

Here's what that changes in practice:

1 — Full-codebase questions without CLAUDE.md gymnastics

Before, you'd maintain a CLAUDE.md that carefully trimmed what Claude needed to "remember" so sessions didn't overflow. With a 1M window you can feed an entire src/ tree directly and ask cross-file questions without any manual summarization:

# Pull in everything under src/ in one shot
cat $(git ls-files 'src/**/*.ts') | claude -p "Find every place we handle auth tokens and summarize the flow"

This isn't practical with an 8K or 200K window — it's practical with 1M.

2 — Multi-file refactors with full dependency context

Before, a large refactor required breaking the task into sub-sessions or relying on summarized CLAUDE.md state. Now you can tell Claude Code to open every file touching the API layer, understand the full call graph, and produce the refactor plan in one pass:

/chat Show me every file that imports from lib/api.ts, then propose a migration plan to the new fetchClient interface — load all of them, no partial reads

The model holds the full dependency graph in context and reasons about impact before touching anything.

3 — Long-running background sessions with rich context

Claude Code's background sessions (stabilized in Week 27, v2.1.196) combine naturally with the 1M context window. Start a background session on a long task and it can accumulate a full trace of tool calls and file reads without context getting trimmed mid-run:

claude --session long-migration --background \
  "Migrate all 47 service files from legacy-client to new-client. Stage each file's changes before moving to the next."

On pricing: Sonnet 5 is at introductory rates ($2/$10 per Mtok) through August 31 — after that it moves to $3/$15. Large context reads are cheap right now; build the workflows while pricing is promotional.

Sources: Introducing Claude Sonnet 5 | Claude Code changelog | Sonnet 5 pricing