Live-caught by Rune: a trivial one-tool request ("how many files in my
Downloads folder?") failed with "Provided 10,466 tokens, but the
maximum allowed is 8,192" — on the very first real test of tool
calling. Measured the real cause with Rune's actual live tool
configuration (via a throwaway, uncommitted diagnostic test, not
guessed): registering all 49 currently-enabled tools cost ~3,300
tokens of descriptions alone, before the system prompt, the user's
message, or any tool result even factored in. One External MCP server
(Obsidian, 16 tools) was 63% of that footprint by itself — third-party
tool descriptions are outside Confab's control and can be arbitrarily
verbose, unlike Confab's own deliberately-concise built-in tools.
Checked the fix approach with Rune before implementing (a real
product/scope decision, not something to guess): exclude External MCP
tools specifically for Apple On-Device (other providers' 100K+-token
windows absorb this fine) rather than building a full per-provider
tool-selection UI right now. Re-measured after the fix: 33 tools,
~1,212 tokens — comfortable headroom in a real conversation. Confab's
own built-in tools (files, bash, calendar, mail, contacts, Paperless,
Maps) are unaffected.
Also fixed while investigating: the real error dynamically reported
the actual 8,192-token limit (Apple's own error carries this), which
exposed that Confab's own hardcoded "4K context window" claims
(ModelInfo.contextLength, capabilities.maxContextLength, the model
description text, and a stale hardcoded "(4,096 tokens)" in the
macOS 26.x-only GenerationError fallback path) were wrong for the
current beta. Updated the verified ones to 8192; left the macOS
26.x-only error message without a specific number since whether that
runtime shares the same limit is genuinely unverified.
429 tests, clean.
rune
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