[Brian Krabach (bkrabach)]

Summary

This change makes incomplete fork-resume cost reporting compact and avoids implying that missing history means zero cost.

• For a positive restored total, the console now says: Warning: historical cost is incomplete. Available amounts are a partial subtotal.
• When the total is zero, the console says: Warning: complete historical cost is unavailable. Do not treat missing cost as zero.
• Full diagnostic details are logged at WARNING only when SessionConfig.verbose is enabled. The existing amplifier run --resume <id> --verbose route provides that detail; this change does not add or promise a shorthand flag.
• Cost restoration, totals, contributors, fork boundaries, transcripts, metadata, and global logger thresholds are unchanged.

The commit is based directly on current main (b7e533a49ab3b155098caa68b4f3c5b7001d0482). It contains one commit and exactly four files: AGENTS.md, amplifier_app_cli/session_runner.py, docs/warm-shared-root-state.md, and tests/test_session_runner.py. The added and removed source lines match the previously reviewed four-file patch; current-main transcript-repair, doctor, provider-source, dependency, and guidance changes are retained. No unrelated old-branch commits are included.

Verification

• Current-main focused tests: 69 passed across tests/test_session_runner.py, tests/test_cost_history.py, and tests/test_cost_bridge.py.
• Ruff 0.15.5 checks passed for both changed Python files; source compilation and git diff --check passed.
• Earlier supporting synthetic terminal checks covered eight cases at 80 and 120 columns and parseable JSON/stdout separation. They ran on the earlier source base, not this current-main worktree; they are supporting evidence, not a fresh installed-CLI or live-resume test.
• The full repository suite, installed CLI, clean lockfile install, cross-Python matrix, and real user-session resume were not run locally.
• Exact-head GitHub CI passed on commit d1599189fb5dab706a5835c553c183b98f9abc1e: all eight jobs passed in run 40347753582. The license/cla policy check also passed. The Ubuntu Python 3.11 job included the installed doctor-wheel check.

Review scope

Astra (OpenAI gpt-6-astra) and Fable (claude-fable-5-1) reaffirmed approval within the supplied source-excerpt and evidence scope after reviewing the current-main integration and updated whole-file hashes. The reviewed packet covered the implementation, four source bindings, focused test result, and known limits. These were not independent full-source or runtime audits and are not formal GitHub reviews. The approved patch's added and removed lines are identical to the original reviewed patch.

• AGENTS.md SHA256: 3987df7c4e81dd56ba4ad7eca8db76206a1ee5d90448f0055263957ccc78fc0e
• amplifier_app_cli/session_runner.py SHA256: 6c88cc41c3b79844fc859f37ad0d840387b9482d3e0192d7a055eda831db2433

Compatibility and rollback

The intentional visible change is the warning wording and that detailed warning diagnostics are silent unless verbose mode is enabled. No CLI option, cost-accounting format, or migration is added. Revert this commit to roll back the presentation change; accounting data requires no rollback or migration.