Fingers hovering over ‘send’ in Claude, watching the spinner as it ingests 108,075 lines of FastAPI—again.
That’s the ritual no one’s escaped yet. Codebase-to-AI tools promise to fix it, packing your repo into something agents can gulp without hallucinating the architecture from scratch. But do they deliver? I ran four heavy hitters—Repomix (23k GitHub stars), Aider’s repo-map (43k stars), Codebase Memory MCP (1.4k stars), and newcomer Stacklit—straight on FastAPI. Token counts via tiktoken, same encoding as GPT-4 and Claude. Here’s the blood on the floor.
Repomix spits out your entire repo as one XML or Markdown blob. ~800k tokens uncompressed for FastAPI. Compressed? Still 400k. It overflows context windows like a bad party guest—four to six chunks just to fit. Time: 8-12 seconds. Fine for tiny repos under 50 files, where you paste into ChatGPT for a quick hit. But scale to 500 files? You’re dumping raw source, no structure. The agent drowns in trivia, still hunting for the module graph amid the noise.
And here’s the killer stat, straight from the tests:
Tool Output tokens Context windows used Time Repomix (XML) ~800,000 4-6 windows (overflows 200k) ~8s Repomix (compressed) ~400,000 2-3 windows ~12s Aider repo-map ~8,000-15,000 Fits in one Per-prompt CB Memory MCP Varies per query N/A (streaming) Sub-ms per query Stacklit 4,142 Fits in one 0.4s
Aider’s repo-map feels smarter—ephemeral text map, functions and classes ranked by relevance via PageRank vibes. 8k-15k tokens, slips into one window. Regenerates per prompt, though, tuned to your task. Genius if you’re all-in on Aider (and why wouldn’t you be, with 43k stars?). Catch? Locked inside Aider. No love for Claude Code, Cursor, or Copilot. Can’t share it. It’s your personal ghost, vanishing on machine swap.
Codebase Memory MCP goes deep: SQLite knowledge graph from tree-sitter ASTs, 66 languages. Query for call paths, dead code, relationships—sub-millisecond hits. Dependency graphs? Yes. Full signatures? Check. But it’s a local server, no committed artifact. Teammate joins? They rebuild the DB. Switch laptops? Rinse, repeat. Powerful for solo semantic dives, clunky for teams.
Stacklit—the author’s fresh build—nails 4,142 tokens. A committed JSON index: modules, exports, types, connections, 90-day git heatmap. No source code bloat. Fits anywhere. Works with Claude, Cursor, Aider, Copilot—via file or MCP server (7 tools). Incremental via Merkle hashes. Monorepo-savvy. And get this: on Express.js (21k lines), 3,765 tokens; Gin (Go, 23k lines), 3,361; even Rust’s Axum (44k lines) at 14k. Blazing 0.4s, 32MB Go binary, no runtime deps.
Why Do Tokens Even Matter This Much?
Burn rate. Claude 3.5 Sonnet: $3 per million input tokens. FastAPI via Repomix? $2.40 a pop, every session. Do that 10x daily? $24 burned on context alone—before you type a prompt. Architecture reveal: these tools shift from full-code dumps to indexes, echoing 1990s databases ditching flat files for relational schemas. Remember Oracle’s early days? Indexes let queries fly without scanning every row. Same here—Stacklit’s JSON is your B-tree for code. Agents grasp the ‘how files wire together’ without reading lines.
But here’s my dig: corporate hype (or indie equivalent) sells ‘AI understands codebases now.’ Nah. Without indexes, it’s brute force. Stacklit calls out the emperor—structure first, tokens second. Bold prediction? Committed indexes become git convention, like package.json today. Your repo without one? Feels half-baked by 2026.
Can Stacklit Replace Aider’s Map for Real Teams?
Short answer: damn near. Aider wins on relevance-ranking per task—PageRank magic tailors to ‘fix this endpoint.’ Stacklit’s static, universal: everyone sees the same graph, heatmapped by commits. Trade-off? No per-prompt tweak. But commit it, clone anywhere, query via MCP. Visual HTML too—four views: modules, deps, activity, types. Monorepos? Parses 8 formats.
Teams crave shareability. MCP’s local DB? Rebuild hell. Repomix? Git-nope, too fat. Aider? Siloed. Stacklit commits clean—git diff shows index evolves with code. Incremental updates mean no full reparse post-tweak. That’s the architectural shift: code as living database, AI as perpetual reader.
Look, Repomix suits paste-happy soloists. Aider? Diehards only. MCP for query wizards on giants. Stacklit? The git-native play. Tested on FastAPI’s sprawl—1,131 files—it extracts essence without the bloat. Exports signatures with types (struct fields intact), module detection crisp.
Runtime matters too. Node for Repomix (50MB), Python for Aider, C binary (2MB) for MCP. Stacklit? Go static binary, drop-and-run. Config via stacklit.toml—dead simple.
Is Committed Code Indexing the Next Git Norm?
Think about it. Git tracks source, diffs, history. But architecture? Buried. Tools like this surface it as first-class artifact. Historical parallel: Makefiles standardized builds; .gitignore tamed noise. Stacklit.toml + stacklit.json? Could normify ‘repo intelligence.’ PR spin from tool makers glosses token math—reality bites at scale.
FastAPI proves it: 108k lines demand smarts, not dumps. Stacklit’s 4k tokens let agents focus—‘refactor auth’ zooms to hot modules via heatmap. No more ‘read everything.’
Wander a bit: I’ve used these in wild projects. Claude Code loves Stacklit’s file—just @stacklit.json. Cursor too. Aider reads it native. Copilot? Embed in workspace. Cross-tool utopia.
One nit: 11 langs full-parse (tree-sitter), basics for others. MCP edges on 66. But for Python/JS/Go/Rust web stacks? Covers you.
How Do These Stack Up Beyond FastAPI?
Stacklit on others: Express 3.7k, Gin 3.3k, Axum 14k (Rust verbose). Consistent sub-15k. Repomix? Would balloon those too.
Bottom line—pick by pain. Solo quickies? Repomix. Aider loyalist? Stay. Semantic surgeon? MCP. Team scaler? Stacklit’s your bet.
🧬 Related Insights
- Read more: 70% of Bugs Aren’t Code Problems—They’re Spec Nightmares
- Read more: GUI Agents Ditch RPA’s Brittle Scripts for Screenshot Smarts — And Go Fully Local
Frequently Asked Questions
What are the token costs for codebase to AI tools on FastAPI?
Repomix hits 400-800k, Aider 8-15k, MCP varies, Stacklit 4k—smallest static fit.
Does Stacklit work with Cursor and Claude?
Yes, via committed JSON file or MCP server; plug-and-play across agents.
Why commit a code index to git?
Shares structure instantly—no rebuilds for teams, evolves with Merkle hashes.
