build: upgrade Go to 1.26.8

[appleboy]

Summary

Raise the minimum Go version from 1.25.11 to 1.26.8, the latest Go 1.26 patch release. Update Anthropic and Gemini pointer construction to new(value), and Anthropic error matching to errors.AsType, to satisfy the modernize lint rules enabled by Go 1.26. Provider behavior and dependency versions remain unchanged.

Related issues

N/A — no GitHub or Jira issue supplied.

AI authorship

• AI was used
• Tool / model: Codex / GPT-6
• AI-authored files: go.mod, provider/anthropic/anthropic.go, provider/gemini/gemini.go
• Human line-by-line reviewed: None — not yet reviewed by a human.

Change classification

• Core change — the Go minimum affects builds across the repository.
• Recommend two reviewers, including a maintainer familiar with provider code.

Plan reference

Upgrade go.mod to the latest Go 1.26 patch and make the minimal behavior-preserving syntax changes required by lint.

Verification

Run from the repository root after checking out chore/upgrade-go-1.26.8. Prerequisites: Git, make, Go 1.26.8 (or automatic toolchain download enabled), and network access to download modules. No provider credentials or running services are needed for the existing tests.

Command	Coverage / expected result	Status	Observed result
go version	Go 1.26.8 toolchain selected	Passed	go1.26.8 darwin/arm64
make fmt	Repository formatting completes	Passed	Exit 0
make lint	New Go syntax satisfies modernize and other rules	Passed	0 issues
go test ./...	Existing regression tests, including provider stream behavior	Passed	All packages passed
make build	CLI compiles with the raised Go requirement	Passed	Exit 0
git diff --staged --check	No whitespace errors	Passed	Exit 0

Upgrade and provider regression scenario

1. Inspect go.mod: expect go 1.26.8 and unchanged dependency versions.
2. Run go version and make build: expect the selected toolchain to meet the new minimum and a successful CLI build.
3. Run go test ./...: expect existing Anthropic and Gemini streaming tests and the remaining suite to pass.
4. Inspect the provider diff: request parameter values and error message text must remain unchanged.

Status: Passed. The version, build, full suite, and diff inspection met these conditions. These are mechanical syntax changes, with no new functionality or bug fix; existing tests were used. Live provider API calls were not run because no API behavior changed.

Cleanup: the build creates ignored bin/codegpt; no application data or external service state is created.

Security check

• No secrets in the diff
• N/A — no external or security-sensitive interface changed

Risk and rollback

Build environments must support Go 1.26.8 or toolchain auto-download. Review provider syntax conversions for preserved values and error wrapping. Revert this commit to restore the previous Go requirement and syntax.

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