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Answer: The model.compressionThreshold setting is the fraction of context usage at which compression triggers. The /compress command replaces the entire chat context with a summary.

Automatic trigger

model.compressionThreshold is the fraction of context usage at which to trigger context compression (for example 0.2 or 0.3). The default is 0.5, and a change requires a restart.

Manual trigger

/compress replaces the entire chat context with a summary. This saves tokens for future tasks while retaining a high level summary of what has happened.

Related knob

model.summarizeToolOutput enables summarization of tool output with per-tool token budgets; currently only the run_shell_command tool supports summarization.

Artifacts

• Agent CLI compaction knobs (table)
• Agent CLI compaction knobs (markdown table)
• Compaction settings schema
• Topic packet: ao-compaction

See also

• ao-compaction
• ao-compaction-when-to-compact
• ao-compaction-side-constraints

Claims

• id: C1 claim: compressionThreshold sets the trigger fraction. source: S1 evidence: "The fraction of context usage at which to trigger context compression (e.g. 0.2, 0.3)."

• id: C2 claim: /compress swaps the context for a summary. source: S2 evidence: "Replace the entire chat context with a summary."

• id: C3 claim: Compression keeps a high-level summary. source: S2 evidence: "while retaining a high level summary of what has happened."

• id: C4 claim: Only run_shell_command supports tool-output summarization. source: S1 evidence: "Currently only the run_shell_command tool supports summarization."

Sources

• [S1] Gemini CLI configuration. Google Gemini CLI docs (GitHub). https://github.com/google-gemini/gemini-cli/blob/main/docs/reference/configuration.md . License: Apache-2.0 (google-gemini/gemini-cli LICENSE). Accessed 2026-11-09.

• [S2] CLI commands. Google Gemini CLI docs (GitHub). https://github.com/google-gemini/gemini-cli/blob/main/docs/reference/commands.md . License: Apache-2.0 (google-gemini/gemini-cli LICENSE). Accessed 2026-11-09.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted). Sources: GitHub repository docs under Apache License 2.0 (https://www.apache.org/licenses/LICENSE-2.0) or MIT License (https://opensource.org/licenses/MIT), as listed per source; copyright notices remain with the original authors. Text was condensed and changed from the originals.

@misc{iil_note_gjhhjyb0,
  author = {{iinventedlight}},
  title = {{Gemini CLI compaction: /compress and compressionThreshold}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-09},
  url = {https://iinventedlight.com/library/notes/ao-compaction-gemini-cli-compress/},
  note = {Permanent ID iil:note:gjhhjyb0. License: CC-BY-4.0.},
}

Markdown

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